Intermixing at the absorber-buffer layer interface in thin-film solar cells: The electronic effects of point defects in Cu(In,Ga)(Se,S) 2 and Cu 2ZnSn(Se,S) 4 devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varley, J. B.; Lordi, V.

We investigate point defects in the buffer layers CdS and ZnS that may arise from intermixing with Cu(In,Ga)(S,Se) 2 (CIGS) or Cu 2ZnSn(S,Se) 4 (CZTS) absorber layers in thin-film photovoltaics. Using hybrid functional calculations, we characterize the electrical and optical behavior of Cu, In, Ga, Se, Sn, Zn, Na, and K impurities in the buffer. We find that In and Ga substituted on the cation site act as shallow donors in CdS and tend to enhance the prevailing n-type conductivity at the interface facilitated by Cd incorporation in CIGS, whereas they are deep donors in ZnS and will be lessmore » effective dopants. Substitutional In and Ga can favorably form complexes with cation vacancies (A-centers) which may contribute to the “red kink” effect observed in some CIGS-based devices. For CZTS absorbers, we find that Zn and Sn defects substituting on the buffer cation site are electrically inactive in n-type buffers and will not supplement the donor doping at the interface as in CIGS/CdS or ZnS devices. Sn may also preferentially incorporate on the S site as a deep acceptor in n-type ZnS, which suggests possible concerns with absorber-related interfacial compensation in CZTS devices with ZnS-derived buffers. Cu, Na, and K impurities are found to all have the same qualitative behavior, most favorably acting as compensating acceptors when substituting on the cation site. Lastly, our results suggest one beneficial role of K and Na incorporation in CIGS or CZTS devices is the partial passivation of vacancy-related centers in CdS and ZnS buffers, rendering them less effective interfacial hole traps and recombination centers.« less

Intermixing at the absorber-buffer layer interface in thin-film solar cells: The electronic effects of point defects in Cu(In,Ga)(Se,S){sub 2} and Cu{sub 2}ZnSn(Se,S){sub 4} devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varley, J. B.; Lordi, V.

We investigate point defects in the buffer layers CdS and ZnS that may arise from intermixing with Cu(In,Ga)(S,Se){sub 2} (CIGS) or Cu{sub 2}ZnSn(S,Se){sub 4} (CZTS) absorber layers in thin-film photovoltaics. Using hybrid functional calculations, we characterize the electrical and optical behavior of Cu, In, Ga, Se, Sn, Zn, Na, and K impurities in the buffer. We find that In and Ga substituted on the cation site act as shallow donors in CdS and tend to enhance the prevailing n-type conductivity at the interface facilitated by Cd incorporation in CIGS, whereas they are deep donors in ZnS and will be lessmore » effective dopants. Substitutional In and Ga can favorably form complexes with cation vacancies (A-centers) which may contribute to the “red kink” effect observed in some CIGS-based devices. For CZTS absorbers, we find that Zn and Sn defects substituting on the buffer cation site are electrically inactive in n-type buffers and will not supplement the donor doping at the interface as in CIGS/CdS or ZnS devices. Sn may also preferentially incorporate on the S site as a deep acceptor in n-type ZnS, which suggests possible concerns with absorber-related interfacial compensation in CZTS devices with ZnS-derived buffers. Cu, Na, and K impurities are found to all have the same qualitative behavior, most favorably acting as compensating acceptors when substituting on the cation site. Our results suggest one beneficial role of K and Na incorporation in CIGS or CZTS devices is the partial passivation of vacancy-related centers in CdS and ZnS buffers, rendering them less effective interfacial hole traps and recombination centers.« less

Intermixing at the absorber-buffer layer interface in thin-film solar cells: The electronic effects of point defects in Cu(In,Ga)(Se,S) 2 and Cu 2ZnSn(Se,S) 4 devices

DOE PAGES

Varley, J. B.; Lordi, V.

2014-08-08

We investigate point defects in the buffer layers CdS and ZnS that may arise from intermixing with Cu(In,Ga)(S,Se) 2 (CIGS) or Cu 2ZnSn(S,Se) 4 (CZTS) absorber layers in thin-film photovoltaics. Using hybrid functional calculations, we characterize the electrical and optical behavior of Cu, In, Ga, Se, Sn, Zn, Na, and K impurities in the buffer. We find that In and Ga substituted on the cation site act as shallow donors in CdS and tend to enhance the prevailing n-type conductivity at the interface facilitated by Cd incorporation in CIGS, whereas they are deep donors in ZnS and will be lessmore » effective dopants. Substitutional In and Ga can favorably form complexes with cation vacancies (A-centers) which may contribute to the “red kink” effect observed in some CIGS-based devices. For CZTS absorbers, we find that Zn and Sn defects substituting on the buffer cation site are electrically inactive in n-type buffers and will not supplement the donor doping at the interface as in CIGS/CdS or ZnS devices. Sn may also preferentially incorporate on the S site as a deep acceptor in n-type ZnS, which suggests possible concerns with absorber-related interfacial compensation in CZTS devices with ZnS-derived buffers. Cu, Na, and K impurities are found to all have the same qualitative behavior, most favorably acting as compensating acceptors when substituting on the cation site. Lastly, our results suggest one beneficial role of K and Na incorporation in CIGS or CZTS devices is the partial passivation of vacancy-related centers in CdS and ZnS buffers, rendering them less effective interfacial hole traps and recombination centers.« less

Transient and modulated charge separation at CuInSe2/C60 and CuInSe2/ZnPc hybrid interfaces

NASA Astrophysics Data System (ADS)

von Morzé, Natascha; Dittrich, Thomas; Calvet, Wolfram; Lauermann, Iver; Rusu, Marin

2017-02-01

Spectral dependent charge transfer and exciton dissociation have been investigated at hybrid interfaces between inorganic polycrystalline CuInSe2 (untreated and Na-conditioned) thin films and organic C60 as well as zinc phthalocyanine (ZnPc) layers by transient and modulated surface photovoltage measurements. The stoichiometry and electronic properties of the bare CuInSe2 surface were characterized by photoelectron spectroscopy which revealed a Cu-poor phase with n-type features. After the deposition of the C60 layer, a strong band bending at the CuInSe2 surface was observed. Evidence for dissociation of excitons followed by charge separation was found at the CuInSe2/ZnPc interface. The Cu-poor layer at the CuInSe2 surface was found to be crucial for transient and modulated charge separation at CuInSe2/organic hybrid interfaces.

Local Structure Analysis and Interface Layer Effect of Phase-Change Recording Material Using Actual Media

NASA Astrophysics Data System (ADS)

Nakai, Tsukasa; Yoshiki, Masahiko; Satoh, Yasuhiro; Ashida, Sumio

2008-07-01

The influences of the interface layer on crystal structure, the local atomic arrangement, and the electronic and chemical structure of a GeBiTe (GBT) phase-change recording material have been investigated using X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and hard X-ray photoelectron spectroscopy (HX-PES) methods using actual rewritable high-speed HD DVD media without special sample processing. XRD results showed that the crystal structure of laser-crystallized GBT alloy in the actual HD DVD media is the same as that of GeSbTe (GST) alloy, which has a NaCl-type structure. No differences between samples with and without interface layers were found. The lattice constant of GBT is larger than that of GST. Bi increases the lattice constant of GST with respect to the Bi substitution ratio of Sb. According to HX-PES, the DOS of in the recording film amorphous state with an interface layer is closer to that of the crystalline state than the recording film without an interface layer. From XAFS results, clear differences between amorphous (Amo.) and crystalline states (Cry.) were observed. The interatomic distance of amorphous recording material is independent of the existence of an interface layer. On the other hand, the coordination number varied slightly due to the presence of the interface layer. Therefore, the electronic state of the recording layer changes because of the interface layer, although the local structure changes only slightly except for the coordination number. Combining these results, we conclude that the interface layer changes the electronic state of the recording layer and promotes crystallization, but only affects the local structure of the atomic arrangement slightly.

Real-space imaging of interfacial water with submolecular resolution

NASA Astrophysics Data System (ADS)

Jiang, Ying; Peking University Team

2014-03-01

Water/solid interfaces are vital to our daily lives and also a central theme across an incredibly wide range of scientific disciplines. Resolving the internal structure, i.e. the O-H directionality, of water molecules adsorbed on solid surfaces has been one of the key issues of water science yet remains challenging. Using a low-temperature scanning tunneling microscope (STM), we report the submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate at 5 K. The frontier molecular orbitals of adsorbed water were directly visualized, which allowed discriminating the orientation of the monomers and the H-bond directionality of the tetramers in real space. Comparison with ab initio density functional theory calculations reveals that the ability to access the orbital structures of water stems from the electronic decoupling effect provided by the NaCl films and the precisely tunable tip-water coupling. Supported by National Basic Research Programs of China and National Science Foundation of China.

Fabrication and photoelectrochemical properties of ZnS/Au/TiO2 nanotube array films.

PubMed

Zhu, Yan-Feng; Zhang, Juan; Xu, Lu; Guo, Ya; Wang, Xiao-Ping; Du, Rong-Gui; Lin, Chang-Jian

2013-03-21

A highly ordered TiO(2) nanotube array film was fabricated by an anodic oxidation method. The film was modified by Au nanoparticles (NPs) formed by a deposition-precipitation technique and was covered with a thin ZnS shell prepared by a successive ionic layer adsorption and reaction (SILAR) method. The photoelectrochemical properties of the prepared ZnS/Au/TiO(2) composite film were evaluated by incident photon-to-current conversion efficiency (IPCE), and photopotential and electrochemical impedance spectroscopy (EIS) measurements under white light illumination. The results indicated that the Au NPs could expand the light sensitivity range of the film and suppress the electron-hole recombination, and the ZnS shell could inhibit the leakage of photogenerated electrons from the surface of Au NPs to the ZnS/electrolyte interface. When the 403 stainless steel in a 0.5 M NaCl solution was coupled to the ZnS/Au/TiO(2) nanotube film photoanode under illumination, its potential decreased by 400 mV, showing that the composite film had a better photocathodic protection effect on the steel than that of a pure TiO(2) nanotube film.

Total reflection infrared spectroscopy of water-ice and frozen aqueous NaCl solutions.

PubMed

Walker, Rachel L; Searles, Keith; Willard, Jesse A; Michelsen, Rebecca R H

2013-12-28

Liquid-like and liquid water at and near the surface of water-ice and frozen aqueous sodium chloride films were observed using attenuated total reflection infrared spectroscopy (ATR-IR). The concentration of NaCl ranged from 0.0001 to 0.01 M and the temperature varied from the melting point of water down to 256 K. The amount of liquid brine at the interface of the frozen films with the germanium ATR crystal increased with salt concentration and temperature. Experimental spectra are compared to reflection spectra calculated for a simplified morphology of a uniform liquid layer between the germanium crystal and the frozen film. This morphology allows for the amount of liquid observed in an experimental spectrum to be converted to the thickness of a homogenous layer with an equivalent amount of liquid. These equivalent thickness ranges from a nanometer for water-ice at 260 K to 170 nm for 0.01 M NaCl close to the melting point. The amounts of brine observed are over an order of magnitude less than the total liquid predicted by equilibrium thermodynamic models, implying that the vast majority of the liquid fraction of frozen solutions may be found in internal inclusions, grain boundaries, and the like. Thus, the amount of liquid and the solutes dissolved in them that are available to react with atmospheric gases on the surfaces of snow and ice are not well described by thermodynamic equilibrium models which assume the liquid phase is located entirely at the surface.

Selective enhancement of Selényi rings induced by the cross-correlation between the interfaces of a two-dimensional randomly rough dielectric film

NASA Astrophysics Data System (ADS)

Banon, J.-P.; Hetland, Ø. S.; Simonsen, I.

2018-02-01

By the use of both perturbative and non-perturbative solutions of the reduced Rayleigh equation, we present a detailed study of the scattering of light from two-dimensional weakly rough dielectric films. It is shown that for several rough film configurations, Selényi interference rings exist in the diffusely scattered light. For film systems supported by dielectric substrates where only one of the two interfaces of the film is weakly rough and the other planar, Selényi interference rings are observed at angular positions that can be determined from simple phase arguments. For such single-rough-interface films, we find and explain by a single scattering model that the contrast in the interference patterns is better when the top interface of the film (the interface facing the incident light) is rough than when the bottom interface is rough. When both film interfaces are rough, Selényi interference rings exist but a potential cross-correlation of the two rough interfaces of the film can be used to selectively enhance some of the interference rings while others are attenuated and might even disappear. This feature may in principle be used in determining the correlation properties of interfaces of films that otherwise would be difficult to access.

Halide Ions Effects on Surface Excess of Long Chain Ionic Liquids Water Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenjie; Sung, Woongmo; Ao, Mingqi

2013-10-07

The interfacial structure and composition of water solutions with alkylimidazolium ionic liquids varying in their halide anions ([C12mim][X], X = Cl and I) were investigated by X-ray near-total-reflection fluorescence spectroscopy and X-ray reflectivity measurements. We demonstrate that X-ray fluorescence and reflectivity techniques provide a more direct measurement of surface adsorption. Furthermore, we show that for [C12mim][Cl] and [C12mim][I] solutions with mixed inorganic salts (NaI, NaCl), I– ions replace Cl– above the critical micelle concentration (CMC) of [C12mim][Cl] at much lower concentrations of NaI, whereas NaCl concentrations a hundred times higher than the CMC of [C12mim][I] only partially replace the I–more » at the interface. Our surface-sensitive X-ray diffraction and spectroscopy provide two independent tools to directly determine the surface adsorption of ionic surfactants and the interfacial composition of the surface films.« less

Kinetics and mechanism of corrosion of SiC by molten salts

NASA Technical Reports Server (NTRS)

Jacobson, N. S.

1986-01-01

Corrosion of sintered alpha-SiC under thin films of Na2CO3/CO2, Na2SO4/O2, and Na2SO4/SO3 was investigated at 1000 C. Chemical analysis was used to follow silicate and silica evolution as a function of time. This information coupled with morphology observations leads to a detailed corrosion mechanism. In all cases the corrosion reactions occur primarily in the first few hours. In the Na2CO3/CO2 case, rapid oxidation and dissolution lead to a thick layer of silicate melt in about 0.25 h. After this, silica forms a protective layer on the carbide. In the Na2SO4/O2 case, a similar mechanism occurs. In the Na2SO4/SO3 case, a porous nonprotective layer of SiO2 grows directly on the carbide, and a silicate melt forms above this. In addition, SiO2 and regenerated Na2SO4 form at the melt/gas interface due to reaction of silicate with SO3 and SO2 + O2. The reaction slows when the lower silica layer becomes nonporous.

Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration

PubMed Central

Luo, Dan; Wang, Feng; Zhu, Jingyi; Cao, Feng; Liu, Yuan; Li, Xiaogang; Willson, Richard C.; Yang, Zhaozhong; Chu, Ching-Wu; Ren, Zhifeng

2016-01-01

The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil–water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl2), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions. PMID:27354529

Nanofluid of graphene-based amphiphilic Janus nanosheets for tertiary or enhanced oil recovery: High performance at low concentration.

PubMed

Luo, Dan; Wang, Feng; Zhu, Jingyi; Cao, Feng; Liu, Yuan; Li, Xiaogang; Willson, Richard C; Yang, Zhaozhong; Chu, Ching-Wu; Ren, Zhifeng

2016-07-12

The current simple nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. We have designed and produced a nanofluid of graphene-based amphiphilic nanosheets that is very effective at low concentration. Our nanosheets spontaneously approached the oil-water interface and reduced the interfacial tension in a saline environment (4 wt % NaCl and 1 wt % CaCl2), regardless of the solid surface wettability. A climbing film appeared and grew at moderate hydrodynamic condition to encapsulate the oil phase. With strong hydrodynamic power input, a solid-like interfacial film formed and was able to return to its original form even after being seriously disturbed. The film rapidly separated oil and water phases for slug-like oil displacement. The unique behavior of our nanosheet nanofluid tripled the best performance of conventional nanofluid flooding methods under similar conditions.

Effect of Gold on the Corrosion Behavior of an Electroless Nickel/Immersion Gold Surface Finish

NASA Astrophysics Data System (ADS)

Bui, Q. V.; Nam, N. D.; Yoon, J. W.; Choi, D. H.; Kar, A.; Kim, J. G.; Jung, S. B.

2011-09-01

The performance of surface finishes as a function of the pH of the utilized plating solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. In addition, the surface finishes were examined by x-ray diffraction (XRD), and the contact angle of the liquid/solid interface was recorded. NiP films on copper substrates with gold coatings exhibited their highest coating performance at pH 5. This was attributed to the films having the highest protective efficiency and charge transfer resistance, lowest porosity value, and highest contact angle among those examined as a result of the strongly preferred Au(111) orientation and the improved surface wettability.

Effects of Na Doping on Structural, Optical, and Electronic Properties of ZnO Thin Films Fabricated by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Fan, Heliang; Yao, Zhen; Xu, Cheng; Wang, Xinqiang; Yu, Zhichao

2018-04-01

Undoped and Na-doped ZnO thin films were fabricated by sol-gel technique on quartz glass substrates and annealed at 500°C for 1 h. The structural properties of the films were characterized using x-ray diffraction analysis, which revealed hexagonal wurtzite structure with no peaks corresponding to Na2O or other Na phases being found. Surface morphology observations by scanning electron microscopy revealed that the crystallite size and topographical properties of the ZnO films were influenced by the Na doping concentration. X-ray photoelectron spectra revealed presence of Na+ in ZnO regime. The transmittance spectra indicated that the average transmittance of Na-doped ZnO film was above 80% in the visible range, superior to that of the undoped film. There was a blue-shift in the ultraviolet absorption edge with increase of the Na content. Photoluminescence spectra illustrated two peaks, corresponding to ultraviolet near-band-edge and visible emission.

Water vapor adsorption on goethite.

PubMed

Song, Xiaowei; Boily, Jean-François

2013-07-02

Goethite (α-FeOOH) is an important mineral contributing to processes of atmospheric and terrestrial importance. Their interactions with water vapor are particularly relevant in these contexts. In this work, molecular details of water vapor (0.0-19.0 Torr; 0-96% relative humidity at 25 °C) adsorption at surfaces of synthetic goethite nanoparticles reacted with and without HCl and NaCl were resolved using vibrational spectroscopy. This technique probed interactions between surface (hydr)oxo groups and liquid water-like films. Molecular dynamics showed that structures and orientations adopted by these waters are comparable to those adopted at the interface with liquid water. Particle surfaces reacted with HCl accumulated less water than acid-free surfaces due to disruptions in hydrogen bond networks by chemisorbed waters and chloride. Particles reacted with NaCl had lower loadings below ∼10 Torr water vapor but greater loadings above this value than salt-free surfaces. Water adsorption reactions were here affected by competitive hydration of coexisting salt-free surface regions, adsorbed chloride and sodium, as well as precipitated NaCl. Collectively, the findings presented in this study add further insight into the initial mechanisms of thin water film formation at goethite surfaces subjected to variations in water vapor pressure that are relevant to natural systems.

Transport Properties of Anatase-TiO2 Polycrystalline-Thin-Film Field-Effect Transistors with Electrolyte Gate Layers

NASA Astrophysics Data System (ADS)

Horita, Ryohei; Ohtani, Kyosuke; Kai, Takahiro; Murao, Yusuke; Nishida, Hiroya; Toya, Taku; Seo, Kentaro; Sakai, Mio; Okuda, Tetsuji

2013-11-01

We have fabricated anatase-TiO2 polycrystalline-thin-film field-effect transistors (FETs) with poly(vinyl alcohol) (PVA), ion-liquid (IL), and ion-gel (IG) gate layers, and have tried to improve the response to gate voltage by varying the concentration of mobile ions in these electrolyte gate layers. The increase in the concentration of mobile ions by doping NaOH into the PVA gate layer or reducing the gelator in the IG gate layer markedly increases the drain-source current and reduces the driving gate voltage, which show that the mobile ions in the PVA, IL, and IG gate layers cause the formation of electric double layers (EDLs), which act as nanogap capacitors. In these TiO2-EDL-FETs, the slow formation of EDLs and the oxidation reaction at the interface between the surface of the TiO2 film and the electrolytes cause unideal FET properties. In the optimized IL and IG TiO2-EDL-FETs, the driving gate voltage is less than 1 V and the ON/OFF ratios of the transfer characteristics are about 1×104 at RT, and the nearly metallic state is realized at the interface purely by applying a gate voltage.

Equivalent Aqueous Phase Modulation of Domain Segregation in Myelin Monolayers and Bilayer Vesicles

PubMed Central

Oliveira, Rafael G.; Schneck, Emanuel; Funari, Sergio S.; Tanaka, Motomu; Maggio, Bruno

2010-01-01

Purified myelin can be spread as monomolecular films at the air/aqueous interface. These films were visualized by fluorescence and Brewster angle microscopy, showing phase coexistence at low and medium surface pressures (<20–30 mN/m). Beyond this threshold, the film becomes homogeneous or not, depending on the aqueous subphase composition. Pure water as well as sucrose, glycerol, dimethylsulfoxide, and dimethylformamide solutions (20% in water) produced monolayers that become homogeneous at high surface pressures; on the other hand, the presence of salts (NaCl, CaCl2) in Ringer's and physiological solution leads to phase domain microheterogeneity over the whole compression isotherm. These results show that surface heterogeneity is favored by the ionic milieu. The modulation of the phase-mixing behavior in monolayers is paralleled by the behavior of multilamellar vesicles as determined by small-angle and wide-angle x-ray scattering. The correspondence of the behavior of monolayers and multilayers is achieved only at high surface pressures near the equilibrium adsorption surface pressure; at lower surface pressures, the correspondence breaks down. The equilibrium surface tension on all subphases corresponds to that of the air/alkane interface (27 mN/m), independently on the surface tension of the clean subphase. PMID:20816062

Structure and piezo-ferroelectricity relationship study of (K0.5Na0.5)0.985La0.005NbO3 epitaxial films deposited on SrTiO3 by sputtering.

PubMed

H Mŏk, H Linh; Martínez-Aguilar, E; Gervacio-Arciniega, J J; Vendrell, X; Siqueiros-Beltrones, J M; Raymond-Herrera, O

2017-12-18

This work demonstrates that the rf-sputtering technique, combined with appropriate heat treatments, is potentially effective to develop new materials and devices based on oxide-interface and strain engineering. We report a study of the structural-physical properties relationship of high crystalline quality, highly oriented and epitaxial thin films of the lead-free (K 0.5 Na 0.5 ) 0.985 La 0.005 NbO 3 (KNNLa) compound which were successfully deposited on Nb-doped SrTiO 3 substrates, with orientations [100] (NSTO100) and [110] (NSTO110). The crystalline growth and the local ferroelectric and piezoelectric properties were evaluated by piezoresponse force microscopy combined with transmission electron microscopy and texture analysis by X-ray diffraction. Conditioned by the STO surface parameters, in the KNNLa films on NSTO100 coexist a commensurate [001]-tetragonal phase and two incommensurate [010]-monoclinic phases; while on NSTO110 the KNNLa films grew only in an incommensurate [101]-monoclinic phase. Both samples show excellent out-of-plane polarization switching patterns consistent with 180° domains walls; while for KNNLa/NSTO100 ferroelectric domains grow with the polarization pointing down, for KNNLa/NSTO110 they prefer to grow with the polarization pointing up. Comparing with previous reports on epitaxial KNN films, we find our samples to be of very high quality regarding their crystalline growth with highly ordered ferroelectric domains arrangements and, consequently, great potential for domain engineering.

Direct Room Temperature Welding and Chemical Protection of Silver Nanowire Thin Films for High Performance Transparent Conductors.

PubMed

Ge, Yongjie; Duan, Xidong; Zhang, Meng; Mei, Lin; Hu, Jiawen; Hu, Wei; Duan, Xiangfeng

2018-01-10

Silver nanowire (Ag-NW) thin films have emerged as a promising next-generation transparent electrode. However, the current Ag-NW thin films are often plagued by high NW-NW contact resistance and poor long-term stability, which can be largely attributed to the ill-defined polyvinylpyrrolidone (PVP) surface ligands and nonideal Ag-PVP-Ag contact at NW-NW junctions. Herein, we report a room temperature direct welding and chemical protection strategy to greatly improve the conductivity and stability of the Ag-NW thin films. Specifically, we use a sodium borohydride (NaBH 4 ) treatment process to thoroughly remove the PVP ligands and produce a clean Ag-Ag interface that allows direct welding of NW-NW junctions at room temperature, thus greatly improving the conductivity of the Ag-NW films, outperforming those obtained by thermal or plasmonic thermal treatment. We further show that, by decorating the as-formed Ag-NW thin film with a dense, hydrophobic dodecanethiol layer, the stability of the Ag-NW film can be greatly improved by 150-times compared with that of PVP-wrapped ones. Our studies demonstrate that a proper surface ligand design can effectively improve the conductivity and stability of Ag-NW thin films, marking an important step toward their applications in electronic and optoelectronic devices.

Model for interface formation and the resulting electrical properties for barium-strontium-titanate films on silicon

NASA Astrophysics Data System (ADS)

Mueller, A. H.; Suvorova, N. A.; Irene, E. A.; Auciello, O.; Schultz, J. A.

2003-04-01

The interface formation between sputtered barium strontium titanate (BST) films and both Si and SiO2 substrate surfaces has been followed using real-time spectroscopic ellipsometry and the mass spectrometry of recoiled ions. In both substrates an intermixed interface layer was observed and subcutaneous Si oxidation occurred. A model for the interface formation is proposed in which the interface includes an SiO2 film on Si, and an intermixed film on which is pure BST. During the deposition of BST the interfaces films were observed to change in time. Electrical characterization of the resulting metal-BST interface capacitors indicates that those samples with SiO2 on the Si surface had the best electrical characteristics.

The effect of K and Na excess on the ferroelectric and piezoelectric properties of K0.5Na0.5NbO3 thin films

NASA Astrophysics Data System (ADS)

Ahn, C. W.; Y Lee, S.; Lee, H. J.; Ullah, A.; Bae, J. S.; Jeong, E. D.; Choi, J. S.; Park, B. H.; Kim, I. W.

2009-11-01

We have fabricated K0.5Na0.5NbO3 (KNN) thin films on Pt substrates by a chemical solution deposition method and investigated the effect of K and Na excess (0-30 mol%) on ferroelectric and piezoelectric properties of KNN thin film. It was found that with increasing K and Na excess in a precursor solution from 0 to 30 mol%, the leakage current and ferroelectric properties were strongly affected. KNN thin film synthesized by using 20 mol% K and Na excess precursor solution exhibited a low leakage current density and well saturated ferroelectric P-E hysteresis loops. Moreover, the optimized KNN thin film had good fatigue resistance and a piezoelectric constant of 40 pm V-1, which is comparable to that of polycrystalline PZT thin films.

Structural and morphological modifications of polymer thin film in the presence of nonsolvent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talukdar, Hrishikesh, E-mail: hiasst@yahoo.in; Kundu, Sarathi

Thin films of sodium poly(acrylic acid) salt (Na-PAA) have been investigated to obtain the modification of the out-of-plane structure and surface morphology in the presence of toluene which is considered as nonsolvent for Na-PAA. X-ray reflectivity analysis show that the out-of-plane thickness of the Na-PAA film increases if the film is kept for longer time inside the toluene. For the thicker film the effect of toluene is more pronounced than the thinner one. Surface morphology obtained from the atomic force microscopy shows that the top surface becomes relatively rough after the dipping of the Na-PAA film inside toluene. Although toluenemore » is nonsolvent for Na-PAA molecules, however, the effect of restructuring of the nanometer-thick polymer film cannot be ignored. The reason for such structural modification has been proposed.« less

Total reflection infrared spectroscopy of water-ice and frozen aqueous NaCl solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Rachel L.; Searles, Keith; Willard, Jesse A.

2013-12-28

Liquid-like and liquid water at and near the surface of water-ice and frozen aqueous sodium chloride films were observed using attenuated total reflection infrared spectroscopy (ATR-IR). The concentration of NaCl ranged from 0.0001 to 0.01 M and the temperature varied from the melting point of water down to 256 K. The amount of liquid brine at the interface of the frozen films with the germanium ATR crystal increased with salt concentration and temperature. Experimental spectra are compared to reflection spectra calculated for a simplified morphology of a uniform liquid layer between the germanium crystal and the frozen film. This morphologymore » allows for the amount of liquid observed in an experimental spectrum to be converted to the thickness of a homogenous layer with an equivalent amount of liquid. These equivalent thickness ranges from a nanometer for water-ice at 260 K to 170 nm for 0.01 M NaCl close to the melting point. The amounts of brine observed are over an order of magnitude less than the total liquid predicted by equilibrium thermodynamic models, implying that the vast majority of the liquid fraction of frozen solutions may be found in internal inclusions, grain boundaries, and the like. Thus, the amount of liquid and the solutes dissolved in them that are available to react with atmospheric gases on the surfaces of snow and ice are not well described by thermodynamic equilibrium models which assume the liquid phase is located entirely at the surface.« less

Salt exclusion in silane-laced epoxy coatings.

PubMed

Wang, Peng; Schaefer, Dale W

2010-01-05

The corrosion protection mechanism of a one-step silane-laced epoxy coating system was investigated using neutron reflectivity. Pure epoxy and silane-laced epoxy films were examined at equilibrium with saturated NaCl water solution. The results demonstrate that the addition of silane introduces a salt-exclusion effect to epoxy coating. Specifically, the addition of silane densifies the epoxy network, which leads to exclusion of hydrated salt ions by a size effect. The effect is particularly significant at the metal-coating interface. Exclusion of ions improves the corrosion resistance, particularly for metals susceptible to pitting.

Surface and interface engineering of anatase TiO2 anode for sodium-ion batteries through Al2O3 surface modification and wise electrolyte selection

NASA Astrophysics Data System (ADS)

Li, Tao; Gulzar, Umair; Bai, Xue; Monaco, Simone; Longoni, Gianluca; Prato, Mirko; Marras, Sergio; Dang, Zhiya; Capiglia, Claudio; Proietti Zaccaria, Remo

2018-04-01

In the present study, Al2O3 is utilized for the first time as coating agent on nanostructured anatase TiO2 in order to investigate its effect on sodium-ion batteries performance. Our results show that the Al2O3 coating, introduced by a facile two-step approach, provides beneficial effects to the TiO2-based anodes. However, the coated TiO2 still suffers of capacity fading upon cycling when using 1.0 M of NaClO4 in propylene carbonate (PC) as electrolyte. To address this issue, the influence of different electrolytes (NaClO4 salt in various solvents) is further studied. It is found that the modified TiO2 exhibits significant improvements in cycling performance using binary ethylene carbonate (EC) and PC solvent mixture without the need of the commonly used fluoroethylene carbonate (FEC) additive. Under the best configuration, our battery could deliver a high reversible capacity of 188.1 mAh g-1 at 0.1C after 50 cycles, good rate capability up to 5C, and remarkable long-term cycling stability at 1C rate for 650 cycles. This excellent performance can be ascribed to the synergistic effects of surface and interface engineering enabling the formation of a stable and highly ionic conductive interface layer in EC:PC based electrolyte which combines the native SEI film and an 'artificial' SEI layer of irreversibly formed Na-Al-O.

Mammography film processor replenishment rate: bromide level monitoring.

PubMed

Kimme-Smith, C; Wuelfing, P; Kitts, E L; Cagnon, C; Basic, M; Bassett, L

1997-03-01

The effects of the mammography film processing replenishment rate on contrast and speed are studied sensitometrically. Two experiments studied decreasing replenishment rates in the Kodak RP developer and quantified changes in the developer by measuring bromide ion concentrations. First, values of NaBr concentration from 1.7 to 8.4 g/L, achieved by reducing the replenishment rate, were tested with sensitometry strips. Second, the developer replenishment rate of a high volume dedicated mammography processor was reduced by one-third, to 20 cm3/1560 cm2, so that the NaBr concentration rose from 2.0 to 12.36. Sensitometric results for four film types and patient films were tested for changes from standard values as NaBr concentration was restored to 3.31 g/L. Fifty-five clinical images obtained at 7.3-9.3 NaBr g/L were compared to their matching previous films, with NaBr levels of 2-3 g/L, for contrast and visibility of the skin line. For the range of the NaBr ion from 1.7 to 7 g/L, no significant sensitometric differences were found. Above 7 g/L, different film types had different sensitometric results. From 7.3 to 9.3 NaBr g/L, 47.5% of the clinical films reviewed by four radiologists had less contrast compared to previous films. Dedicated mammography processors with high film volume (i.e., those that do not have excessive oxidation or foreign dye problems) can operate at lower replenishment rates than are currently employed. All common mammography film types are stable at these lower replenishment rates up to 7.0 NaBr g/L.

Clay-Enriched Silk Biomaterials for Bone Formation

PubMed Central

Mieszawska, Aneta J.; Llamas, Jabier Gallego; Vaiana, Christopher A.; Kadakia, Madhavi P.; Naik, Rajesh R.; Kaplan, David L.

2011-01-01

The formation of silk protein/clay composite biomaterials for bone tissue formation is described. Silk fibroin serves as an organic scaffolding material offering mechanical stability suitable for bone specific uses. Clay montmorillonite (Cloisite ® Na+) and sodium silicate are sources of osteoinductive silica-rich inorganic species, analogous to bioactive bioglass-like bone repair biomaterial systems. Different clay particle-silk composite biomaterial films were compared to silk films doped with sodium silicate as controls for support of human bone marrow derived mesenchymal stem cells (hMSCs) in osteogenic culture. The cells adhered and proliferated on the silk/clay composites over two weeks. Quantitative real-time RT-PCR analysis revealed increased transcript levels for alkaline phosphatase (ALP), bone sialoprotein (BSP), and collagen type 1 (Col I) osteogenic markers in the cells cultured on the silk/clay films in comparison to the controls. Early evidence for bone formation based on collagen deposition at the cell-biomaterial interface was also found, with more collagen observed for the silk films with higher contents of clay particles. The data suggest that the silk/clay composite systems may be useful for further study toward bone regenerative needs. PMID:21549864

Thin-film formation of Si clathrates on Si wafers

NASA Astrophysics Data System (ADS)

Ohashi, Fumitaka; Iwai, Yoshiki; Noguchi, Akihiro; Sugiyama, Tomoya; Hattori, Masashi; Ogura, Takuya; Himeno, Roto; Kume, Tetsuji; Ban, Takayuki; Nonomura, Shuichi

2014-04-01

In this study, we prepared Si clathrate films (Na8Si46 and NaxSi136) using a single-crystalline Si substrate. Highly oriented film growth of Zintl-phase sodium silicide, which is a precursor of Si clathrate, was achieved by exposing Na vapour to Si substrates under an Ar atmosphere. Subsequent heat treatment of the NaSi film at 400 °C (3 h) under vacuum (<10-2 Pa) resulted in a film of Si clathrates having a thickness of several micrometres. Furthermore, this technique enabled the selective growth of Na8Si46 and NaxSi136 using the appropriate crystalline orientation of Si substrates.

In vitro cardiomyocyte-driven biogenerator based on aligned piezoelectric nanofibers

NASA Astrophysics Data System (ADS)

Liu, Xia; Zhao, Hui; Lu, Yingxian; Li, Song; Lin, Liwei; Du, Yanan; Wang, Xiaohong

2016-03-01

Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion.Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion. Electronic supplementary information (ESI) available: Includes the ESI methods and figures, and videos of cell contraction and biogenerator bending. See DOI: 10.1039/c5nr08430j

STABILITY OF AQUEOUS FILMS BETWEEN BUBBLES

PubMed Central

Ohnishi, Satomi; Vogler, Erwin A.; Horn, Roger G.

2010-01-01

Film thinning experiments have been conducted with aqueous films between two air phases in a thin film pressure balance. The films are free of added surfactant but simple NaCl electrolyte is added in some experiments. Initially the experiments begin with a comparatively large volume of water in a cylindrical capillary tube a few mm in diameter, and by withdrawing water from the center of the tube the two bounding menisci are drawn together at a prescribed rate. This models two air bubbles approaching at a controlled speed. In pure water the results show three regimes of behavior depending on the approach speed: at slow speed (<1 µm/s) it is possible to form a flat film of pure water, ~100 nm thick, that is stabilised indefinitely by disjoining pressure due to repulsive double-layer interactions between naturally-charged air/water interfaces. The data are consistent with a surface potential of −57 mV on the bubble surfaces. At intermediate approach speed (~1 – 150 µm/s) the films are transiently stable due to hydrodynamic drainage effects, and bubble coalescence is delayed by ~10 – 100 s. At approach speeds greater than ~150 µm/s the hydrodynamic resistance appears to become negligible, and the bubbles coalesce without any measurable delay. Explanations for these observations are presented that take into account DLVO and Marangoni effects entering through disjoining pressure, surface mobility and hydrodynamic flow regimes in thin film drainage. In particular, it is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia-controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles. A simple model is developed that accounts for the boundaries between different film stability or coalescence regimes. Predictions of the model are consistent with the data, and the effects of adding electrolyte can be explained. In particular, addition of electrolyte at high concentration inhibits the near-instantaneous coalescence phenomenon, thereby contributing to increased foam film stability at high approach speeds, as reported in previous literature. This work highlights the significance of bubble approach speed as well as electrolyte concentration in affecting bubble coalescence. PMID:20146434

Influence of Ionic Strength on the Deposition of Metal-Phenolic Networks.

PubMed

Guo, Junling; Richardson, Joseph J; Besford, Quinn A; Christofferson, Andrew J; Dai, Yunlu; Ong, Chien W; Tardy, Blaise L; Liang, Kang; Choi, Gwan H; Cui, Jiwei; Yoo, Pil J; Yarovsky, Irene; Caruso, Frank

2017-10-10

Metal-phenolic networks (MPNs) are a versatile class of self-assembled materials that are able to form functional thin films on various substrates with potential applications in areas including drug delivery and catalysis. Different metal ions (e.g., Fe III , Cu II ) and phenols (e.g., tannic acid, gallic acid) have been investigated for MPN film assembly; however, a mechanistic understanding of the thermodynamics governing MPN formation remains largely unexplored. To date, MPNs have been deposited at low ionic strengths (<5 mM), resulting in films with typical thicknesses of ∼10 nm, and it is still unclear how a bulk complexation reaction results in homogeneous thin films when a substrate is present. Herein we explore the influence of ionic strength (0-2 M NaCl) on the conformation of MPN precursors in solution and how this determines the final thickness and morphology of MPN films. Specifically, the film thickness increases from 10 nm in 0 M NaCl to 12 nm in 0.5 M NaCl and 15 nm in 1 M NaCl, after which the films grow rougher rather than thicker. For example, the root-mean-square roughness values of the films are constant below 1 M NaCl at 1.5 nm; in contrast, the roughness is 3 nm at 1 M NaCl and increases to 5 nm at 2 M NaCl. Small-angle X-ray scattering and molecular dynamics simulations allow for comparisons to be made with chelated metals and polyelectrolyte thin films. For example, at a higher ionic strength (2 M NaCl), sodium ions shield the galloyl groups of tannic acid, allowing them to extend away from the Fe III center and interact with other MPN complexes in solution to form thicker and rougher films. As the properties of films determine their final performance and application, the ability to tune both thickness and roughness using salts may allow for new applications of MPNs.

Leaf gas films contribute to rice (Oryza sativa) submergence tolerance during saline floods.

PubMed

Herzog, Max; Konnerup, Dennis; Pedersen, Ole; Winkel, Anders; Colmer, Timothy David

2018-05-01

Floods and salinization of agricultural land adversely impact global rice production. We investigated whether gas films on leaves of submerged rice delay salt entry during saline submergence. Two-week-old plants with leaf gas films (+GF) or with gas films experimentally removed (-GF) were submerged in artificial floodwater with 0 or 50 mm NaCl for up to 16 d. Gas films were present >9 d on GF plants after which gas films were diminished. Tissue ion analysis (Na + , Cl - and K + ) showed that gas films caused some delay of Na + entry, as leaf Na + concentration was 36-42% higher in -GF leaves than +GF leaves on days 1-5. However, significant net uptakes of Na + and Cl - , and K + net loss, occurred despite the presence of gas films, indicating the likely presence of some leaf-to-floodwater contact, so that the gas layer must not have completely separated the leaf surfaces from the water. Natural loss and removal of gas films resulted in severe declines in growth, underwater photosynthesis, chlorophyll a and tissue porosity. Submergence was more detrimental to leaf P N and growth than the additional effect of 50 mm NaCl, as salt did not significantly affect underwater P N at 200 μm CO 2 nor growth. © 2016 John Wiley & Sons Ltd.

Structure and Electric Conduction in Pulsed Laser-Deposited ZnO Thin Films Individually Doped with N, P, or Na

NASA Astrophysics Data System (ADS)

Jiao, D. L.; Zhong, X. C.; Qiu, W. Q.; Zhang, H.; Liu, Z. W.; Zhang, G. Q.

2018-03-01

N-, P-, and Na-doped ZnO films with c-axis orientation were produced by pulsed laser deposition using N2O or O2 as the reaction gas. The effects of deposition temperature and deposition pressure on the lattice structure, morphology, and electric conduction have been investigated. High gas pressure leads to large-sized grains with large grain barriers, which cause a reduced mobility. P acts as an acceptor and the number of compensating defects in the P-doped film is reduced under high O2 pressure. Na also acts as an acceptor, and the effects of high temperature on Na-doped films are encouraging as the solubility of the dopant is high. However, high temperature may cause less incorporation of N and P in the film. In the present work, p-type conduction has not been obtained in N- and P-doped films despite a wide range of processing parameters employed. Na-doped films display an increasing trend towards p-type films at high temperatures and high O2 pressures. These results provide an insight on how these dopants behave in ZnO films and indicate that the careful selection of the deposition conditions is necessary in order to obtain p-type films by pulsed laser deposition.

Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique

NASA Astrophysics Data System (ADS)

Gann, Eliot; Watson, Anne; Tumbleston, John R.; Cochran, Justin; Yan, Hongping; Wang, Cheng; Seok, Jaewook; Chabinyc, Michael; Ade, Harald

2014-12-01

The internal structures of thin films, particularly interfaces between different materials, are critical to system properties and performance across many disciplines, but characterization of buried interface topography is often unfeasible. In this work, we demonstrate that grazing resonant soft x-ray scattering (GRSoXS), a technique measuring diffusely scattered soft x rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces. By controlling and predicting the x-ray electric field intensity throughout the depth of the film and simultaneously the scattering contrast between materials, we are able to unambiguously identify the microstructure at different interfaces of a model polymer bilayer system. We additionally demonstrate the use of GRSoXS to selectively measure the topography of the surface and buried polymer-polymer interface in an organic thin-film transistor, revealing different microstructure and markedly differing evolution upon annealing. In such systems, where only indirect control of interface topography is possible, accurate measurement of the structure of interfaces for feedback is critically important. While we demonstrate the method here using organic materials, we also show that the technique is readily extendable to any thin-film system with elemental or chemical contrasts exploitable at absorption edges.

Surface instability of an imperfectly bonded thin elastic film under surface van der Waals forces

NASA Astrophysics Data System (ADS)

Wang, Xu; Jing, Rong

2017-02-01

This paper studies surface instability of a thin elastic film imperfectly bonded to a rigid substrate interacting with a rigid contactor through van der Waals forces under plane strain conditions. The film-substrate interface is modeled as a linear spring with vanishing thickness described in terms of the normal and tangential interface parameters. Depending on the ratio of the two imperfect interface parameters, the critical value of the Poisson's ratio for the occurrence of surface wrinkling in the absence of surface energy can be greater than, equal to, or smaller than 0.25, which is the critical Poisson's ratio for a perfect film-substrate interface. The critical surface energy for the inhibition of the surface wrinkling is also obtained. Finally, we propose a very simple and effective method to study the surface instability of a multilayered elastic film with imperfect interfaces interacting with a rigid contactor or with another multilayered elastic film (or a multilayered simply supported plate) with imperfect interfaces.

Behavior of oxide film at the interface between particles in sintered Al powders by pulse electric-current sintering

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Song, Minghui; Furuya, Kazuo; Noda, Tetsuji

2003-03-01

The microstructure of the bonding interfaces between particles in aluminum (Al) powder sintered specimens by the pulse electric-current sintering (PECS) process was observed, using conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM). The behavior of oxide film at the interface between Al particles and its effect on properties of the sintered specimens were investigated. The results showed there were two kinds of bonding interfaces in the sintered specimens, namely, the direct metal/metal bonding and the metal/oxide film layer/metal bonding interface. By increasing the fraction of the direct metal/metal bonding interfaces, the tensile strength of the sintered specimens increased, and the electrical resistivity decreased. By increasing the loading pressure at higher sintering temperatures or increasing the sintering temperature under loading pressure, the breakdown of oxide film was promoted. The broken oxide film debris was dispersed in aluminum metal near the bonding interfaces between particles.

Highly efficient lithium composite anode with hydrophobic molten salt in seawater

NASA Astrophysics Data System (ADS)

Zhang, Yancheng; Urquidi-Macdonald, Mirna

A lithium composite anode (lithium/1-butyl-3-methyl-imidazoleum hexafluorophosphate (BMI +PF 6-)/4-VLZ) for primary lithium/seawater semi-fuel-cells is proposed to reduce lithium-water parasitic reaction and, hence, increase the lithium anodic efficiency up to 100%. The lithium composite anode was activated when in contact with artificial seawater (3% NaCl solution) and the output was a stable anodic current density at 0.2 mA/cm 2, which lasted about 10 h under potentiostatic polarization at +0.5 V versus open circuit potential (OCP); the anodic efficiency was indirectly measured to be 100%. With time, a small traces of water diffused through the hydrophobic molten salt, BMI +PF 6-, reached the lithium interface and formed a double layer film (LiH/LiOH). Accordingly, the current density decreased and the anodic efficiency was estimated to be 90%. The hypothesis of small traces of water penetrating the molten salt and reaching the lithium anode—after several hours of operation—is supported by the collected experimental current density and hydrogen evolution, electrochemical impedance spectrum analysis, and non-mechanistic interface film modeling of lithium/BMI +PF 6-.

Water-Soluble Epitaxial NaCl Thin Film for Fabrication of Flexible Devices.

PubMed

Lee, Dong Kyu; Kim, Sungjoo; Oh, Sein; Choi, Jae-Young; Lee, Jong-Lam; Yu, Hak Ki

2017-08-18

We studied growth mechanisms of water-soluble NaCl thin films on single crystal substrates. Epitaxial growth of NaCl(100) on Si(100) and domain-matched growth of NaCl(111) on c-sapphire were obtained at thicknesses below 100 nm even at room temperature from low lattice mismatches in both cases. NaCl thin film, which demonstrates high solubility selectivity for water, was successfully applied as a water-soluble sacrificial layer for fabrication of several functional materials, such as WO 3 nano-helix and Sn doped In 2 O 3 nano-branches.

Molecular Processes Underlying the Structure and Assembly of Thin Films and Nanoparticles at Complex interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richmond, Geraldine

Since 1995 we have pursued a number of different studies that are quite diverse in nature but with the common theme of using novel laser based methods to study important processes at buried interfaces. Studies of Corrosion, Passivation on n-GaAs(100)Methanol Photoelectrochemical Cell In these studies we have used picosecond photoluminescence and electrochemical studies to understand the GaAs/methanol interface. In our most extensive set of studies we conducted photo-illumination and XPS experiments to understand the chemistry occurring in the GaAs/methanol photoelectrochemical during photoexcitation. An important distinction between photocorrosion and photoetching of GaAs is elucidated by these studies. The dependence of GaAsmore » photocorrosion on light intensity has been explored to better understand intrinsic differences between the lamplight studies and the picosecond photoluminescence studies. The effect of coating the GaAs with a sulfide layer prior to immersion in the cell has also been explored. This last result has led us to examine n-GaAs as a function of crystallographic orientation after exposure to aqueous Na 2S containing solutions has been studied as a function of crystallographic orientation of the GaAs surface. The (100) and (110) surfaces are relatively similar, with significant amounts of As-S species present at the interface. The (111)B surface lacks this constituent, but shows significant amounts of metallic As. The XPS results have been correlated with the results of previous photocorrosion and passivation studies conducted in a photoelectrochemical cell. The studies indicate that the metallic As present at (111)B surface contributes strongly to the large surface recombination velocity found there, and to the inability of Na 2S to passivate the (111)B surface. SAMS Under Water: Water Molecular Structure and Bonding at Hydrophobic Surfaces In these DOE sponsored studies we have been interested in learning the similarities and differences in how water behaves at hydrophobic self-assembled monolayer (SAMS)/water interfaces relative to the organic liquid/water interfaces. Several monolayer films have been examined in these studies using a combination of vibrational sum frequency spectroscopy (VSFS), contact angle measurements and AFM. At the hydrocarbon monolayer/water interface we find that water has a weak bonding interaction with the monolayer film that results in an orientation of water at the terminus of these hydrocarbon chains. The water-film interaction is still present for fluorinated films but it is found to be considerably weaker. Hydration and Surfactant Adsorption at Salt/Water Interfaces This set of studies has examined the molecular characteristics of the CaF 2/water interface using VSFS. Our first studies detailed the structure and orientation of water molecules adsorbed at this mineral surfaces including studies of the surface in the presence of aqueous solutions of salts. These studies have been followed by a series of static and time-resolved studies of the adsorption of carboxylic acid containing organics at this surface, specifically carboxylic acid surfactants and acetic acid. In the latter we have developed a new method for time resolved studies that involve sequential wavelength tuning and automated control of spatial beam overlap at the target can probe amplitude changes of sum-frequency resonances in widely spaced infrared regions. This offers great advantages for the study of the synchronism of molecular processes at interfaces. This approach is particularly suitable to investigate the synchronization of interfacial processes such as surfactant adsorption at charged mineral surfaces. Macromolecular Assembly at Liquid/Liquid Interfaces Macromolecular assembly at the interface between water and a hydrophobic surface underlies some of the most important biological and environmental processes on the planet. Our work has examined polymer adsorption and assembly of carboxylic acid-containing polyelectrolytes at the carbon tetrachloride–water interface, a model system for an oil–water interface. Using VSFS and interfacial tension techniques, these unique set of studies identify the factors that dictate whether or not polyelectrolytes will adsorb to the oil–water interface and also describe the specifics of the adsorption process that depend upon factors such as polymer size, charge density, hydrophobicity, conformation, and the effect of metal ion electrostatics and bonding. The systems studied include polyelectrolytes polyacrylic acid (PAA) and polymethylacrylic acid (PMA) of different polymer sizes and under different aqueous solution conditions. The studies are the first to show the highly ordered nature of the adsorption of the first monolayer with subsequent monolayers disordered. The second set of studies have examined how peptoid nanosheets assemble at the oil/water interface. Peptoid nanosheets are a recently discovered class of two-dimensional (2D) nanomaterial, which form from the self-assembly of a sequence-specific peptoid polymer at an air-water interface. Nanosheet formation occurs first through the assembly of a peptoid monolayer and subsequent compression into a bilayer structure. In these highly successful studies we have shown that the oil-water interface provides another opportunity for growth of these unique and highly ordered peptoid sheets. The monolayer formed at this interface are found through surface spectroscopic measurements to be highly ordered and electrostatic interactions between the charged moieties, namely carboxylate and ammonium residues, of the peptoid are essential in the ability of these peptoids to form ordered nanosheets at the oil-water interface.« less

Dentin bonding performance and interface observation of an MMA-based restorative material.

PubMed

Shinagawa, Junichi; Inoue, Go; Nikaido, Toru; Ikeda, Masaomi; Sadr, Alireza; Tagami, Junji

2016-07-30

The purpose of this study was to evaluate bonding performance and dentin interface acid resistance using a 4-META/MMA-TBB based restorative material (BF) compared to a conventional 4-META/MMA-TBB resin cement (SB), and the effect of sodium fluoride (NaF) addition to the materials. Dentin surfaces were treated with 10% citric acid-3% ferric chloride (10-3) or 4-META containing self-etching primer (TP), followed by application of BF or SB polymer powders with or without NaF, to evaluate microtensile bond strength (µTBS) in six experimental groups; 10-3/SB, 10-3/BF, TP/SB, TP/BF, TP/SB/NaF and TP/BF/NaF. SEM observation of the resin-dentin interface was performed after acid-base challenge to evaluate interfacial dentin resistance to acid attack. TP/BF showed highest µTBS, while NaF polymers decreased µTBS. TP/BF showed funnel-shaped erosion at the interface, however, NaF polymers improved acid resistance of interface. In conclusion, BF demonstrated high µTBSs and low acid-resistance at the interface. NaF addition enhanced acid resistance but decreased µTBS.

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep

To understand how variations in interface properties such as misfit-dislocation density and local chemistry affect radiation-induced defect absorption and recombination, we have explored a model system of CrxV1-x alloy epitaxial films deposited on MgO single crystals. By controlling film composition, the lattice mismatch with MgO was adjusted so that the misfit-dislocation density varies at the interface. These interfaces were exposed to irradiation and in situ results show that the film with a semi-coherent interface (Cr) withstands irradiation while V film, which has similar semi-coherent interface like Cr, showed the largest damage. Theoretical calculations indicate that, unlike at metal/metal interfaces, themore » misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry, and the precise location of the misfit-dislocation density relative to the interface, drives defect behavior. Together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials.« less

Films of Bacteria at Interfaces (FBI): Remodeling of Fluid Interfaces by Pseudomonas aeruginosa.

PubMed

Niepa, Tagbo H R; Vaccari, Liana; Leheny, Robert L; Goulian, Mark; Lee, Daeyeon; Stebe, Kathleen J

2017-12-19

Bacteria at fluid interfaces endure physical and chemical stresses unique to these highly asymmetric environments. The responses of Pseudomonas aeruginosa PAO1 and PA14 to a hexadecane-water interface are compared. PAO1 cells form elastic films of bacteria, excreted polysaccharides and proteins, whereas PA14 cells move actively without forming an elastic film. Studies of PAO1 mutants show that, unlike solid-supported biofilms, elastic interfacial film formation occurs in the absence of flagella, pili, or certain polysaccharides. Highly induced genes identified in transcriptional profiling include those for putative enzymes and a carbohydrate metabolism enzyme, alkB2; this latter gene is not upregulated in PA14 cells. Notably, PAO1 mutants lacking the alkB2 gene fail to form an elastic layer. Rather, they form an active film like that formed by PA14. These findings demonstrate that genetic expression is altered by interfacial confinement, and suggest that the ability to metabolize alkanes may play a role in elastic film formation at oil-water interfaces.

Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1984-01-01

The graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ion-plated gold. X-ray photoelectron spectroscopy (XPS) depth profiling and microhardness depth profiling were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultra high vacuum system to maximize adhesion and in oil to minimize adhesion. The results indicate that the solubility of gold on the substrate material controls the depth of the graded interface. Thermal diffusion and chemical diffusion mechanisms are thought to be involved in the formation of the gold-nickel interface. In iron-gold graded interfaces the gold was primarily dispersed in the iron and thus formed a physically bonded interface. The hardness of the gold film was influenced by its depth and was also related to the composition gradient between the gold and the substrate. The graded nickel-gold interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established.

Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1986-01-01

The graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ion-plated gold. X-ray photoelectron spectroscopy (XPS) depth profiling and microhardness depth profiling were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultra high vacuum system to maximize adhesion and in oil to minimize adhesion. The results indicate that the solubility of gold on the substrate material controls the depth of the graded interface. Thermal diffusion and chemical diffusion mechanisms are thought to be involved in the formation of the gold-nickel interface. In iron-gold graded interfaces the gold was primarily dispersed in the iron and thus formed a physically bonded interface. The hardness of the gold film was influenced by its depth and was also related to the composition gradient between the gold and the substrate. The graded nickel-gold interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established.

Symmetry and lattice mismatch induced strain accommodation near and away from correlated perovskite interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vailionis, A.; Boschker, H.; Max Planck Institute for Solid State Research, 70569 Stuttgart

2014-09-29

Distinct MnO{sub 6} octahedral distortions near and away from the La{sub 0.67}Sr{sub 0.33}MnO{sub 3}/SrTiO{sub 3}(001) (LSMO/STO) interface are quantified using synchrotron x-ray diffraction and dynamical x-ray diffraction simulations. Three structural regions of stress accommodation throughout the film thickness were resolved: near the LSMO/STO interface, intermediate region farther from the interface, and the main layer away from the interface. The results show that within the first two unit cells stress is accommodated by the suppression of octahedral rotations in the film, leading to the expansion of the c-axis lattice parameter. Farther from the interface film structure acquires octahedral tilts similar tomore » thicker perovskite films under tensile stress, leading to a reduced c-axis parameter. We demonstrate that these regions are related to two different strain coupling mechanisms: symmetry mismatch at the interface and lattice mismatch in the rest of the film. The findings suggest new routes for strain engineering in correlated perovskite heterostructures.« less

Phonon cross-plane transport and thermal boundary resistance: effect of heat source size and thermal boundary resistance on phonon characteristics

NASA Astrophysics Data System (ADS)

Ali, H.; Yilbas, B. S.

2016-09-01

Phonon cross-plane transport across silicon and diamond thin films pair is considered, and thermal boundary resistance across the films pair interface is examined incorporating the cut-off mismatch and diffusive mismatch models. In the cut-off mismatch model, phonon frequency mismatch for each acoustic branch is incorporated across the interface of the silicon and diamond films pair in line with the dispersion relations of both films. The frequency-dependent and transient solution of the Boltzmann transport equation is presented, and the equilibrium phonon intensity ratios at the silicon and diamond film edges are predicted across the interface for each phonon acoustic branch. Temperature disturbance across the edges of the films pair is incorporated to assess the phonon transport characteristics due to cut-off and diffusive mismatch models across the interface. The effect of heat source size, which is allocated at high-temperature (301 K) edge of the silicon film, on the phonon transport characteristics at the films pair interface is also investigated. It is found that cut-off mismatch model predicts higher values of the thermal boundary resistance across the films pair interface as compared to that of the diffusive mismatch model. The ratio of equilibrium phonon intensity due to the cut-off mismatch over the diffusive mismatch models remains >1 at the silicon edge, while it becomes <1 at the diamond edge for all acoustic branches.

Molecular dynamics simulation of temperature effects on deposition of Cu film on Si by magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhu, Guo; Sun, Jiangping; Zhang, Libin; Gan, Zhiyin

2018-06-01

The temperature effects on the growth of Cu thin film on Si (0 0 1) in the context of magnetron sputtering deposition were systematically studied using molecular dynamics (MD) method. To improve the comparability of simulation results at varying temperatures, the initial status data of incident Cu atoms used in all simulations were read from an identical file via LAMMPS-Python interface. In particular, crystalline microstructure, interface mixing and internal stress of Cu thin film deposited at different temperatures were investigated in detail. With raising the substrate temperature, the interspecies mixed volume and the proportion of face-centered cubic (fcc) structure in the deposited film both increased, while the internal compressive stress decreased. It was found that the fcc structure in the deposited Cu thin films was 〈1 1 1〉 oriented, which was reasonably explained by surface energy minimization and the selectivity of bombardment energy to the crystalline planes. The quantified analysis of interface mixing revealed that the diffusion of Cu atoms dominated the interface mixing, and the injection of incident Cu atoms resulted in the densification of phase near the film-substrate interface. More important, the distribution of atomic stress indicated that the compressive stress was mainly originated from the film-substrate interface, which might be attributed to the densification of interfacial phase at the initial stage of film deposition.

Positron annihilation studies of the AlOx/SiO2/Si interface in solar cell structures

NASA Astrophysics Data System (ADS)

Edwardson, C. J.; Coleman, P. G.; Li, T.-T. A.; Cuevas, A.; Ruffell, S.

2012-03-01

Film and film/substrate interface characteristics of 30 and 60 nm-thick AlOx films grown on Si substrates by thermal atomic layer deposition (ALD), and 30 nm-thick AlOx films by sputtering, have been probed using variable-energy positron annihilation spectroscopy (VEPAS) and Doppler-broadened spectra ratio curves. All samples were found to have an interface which traps positrons, with annealing increasing this trapping response, regardless of growth method. Thermal ALD creates an AlOx/SiOx/Si interface with positron trapping and annihilation occurring in the Si side of the SiOx/Si boundary. An induced positive charge in the Si next to the interface reduces diffusion into the oxides and increases annihilation in the Si. In this region there is a divacancy-type response (20 ± 2%) before annealing which is increased to 47 ± 2% after annealing. Sputtering seems to not produce samples with this same electrostatic shielding; instead, positron trapping occurs directly in the SiOx interface in the as-deposited sample, and the positron response to it increases after annealing as an SiO2 layer is formed. Annealing the film has the effect of lowering the film oxygen response in all film types. Compared to other structural characterization techniques, VEPAS shows larger sensitivity to differences in film preparation method and between as-deposited and annealed samples.

Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

NASA Astrophysics Data System (ADS)

Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

2014-07-01

Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface. The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is significantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.

Structural and Optoelectronic Properties of SnO2 Thin Films Doped by Group-Ia Elements

NASA Astrophysics Data System (ADS)

Benhebal, Hadj; Benrabah, Bedhiaf; Ammari, Aek; Madoune, Yacine; Lambert, Stéphanie D.

This paper presents the results of an experimental work devoted to the synthesis and the characterization of tin dioxide (SnO2) thin layers doped with group-IA elements (Li, Na and K). The materials were synthesized by the sol-gel method and deposited by dip-coating, using tin (II) chloride dihydrate as a source of tin and absolute ethyl alcohol as solvent. Thin films prepared were characterized by several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), visible and ultraviolet spectroscopy and complex impedance method. The results obtained show that the materials kept their tetragonal rutile structure with preferred orientation of (101), whereas doping leads to a reduction of their energy band gap. The complex impedance analysis suggests that the different processes occurring at the electrode interface are modeled by an electrical circuit not affected by the doping.

Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra

NASA Astrophysics Data System (ADS)

Högström, Jonas; Fredriksson, Wendy; Edstrom, Kristina; Björefors, Fredrik; Nyholm, Leif; Olsson, Claes-Olof A.

2013-11-01

An approach for determining depth gradients of metal-ion concentrations in passive films on stainless steel using angle-resolved X-ray photoelectron spectroscopy (ARXPS) is described. The iterative method, which is based on analyses of the oxidised metal peaks, provides increased precision and hence allows faster ARXPS measurements to be carried out. The method was used to determine the concentration depth profiles for molybdenum, iron and chromium in passive films on 316L/EN 1.4432 stainless steel samples oxidised in 0.5 M H2SO4 and acetic acid diluted with 0.02 M Na2B4O7 · 10H2O and 1 M H2O, respectively. The molybdenum concentration in the film is pin-pointed to the oxide/metal interface and the films also contained an iron-ion-enriched surface layer and a chromium-ion-dominated middle layer. Although films of similar composition and thickness (i.e., about 2 nm) were formed in the two electrolytes, the corrosion currents were found to be three orders of magnitude larger in the acetic acid solution. The differences in the layer composition, found for the two electrolytes as well as different oxidation conditions, can be explained based on the oxidation potentials of the metals and the dissolution rates of the different metal ions.

Spectroscopic study of fluorescent probes based on G-quadruplex oligonucleotides labeled with ethynylpyrenyldeoxyuridine.

PubMed

Switalska, Angelika; Kierzek, Ryszard; Dembska, Anna; Juskowiak, Bernard

2017-12-01

The design, synthesis, and spectral properties of four pyrene labeled oligonucleotide probes with G-quadruplex structure (Tel22-Tpy, Tel22-Upy, Tel22-6Upy, Tel22-18Upy) based on the 22-mer human telomeric sequence (Tel22) have been reported. Pyrene labels in the form of ethynylpyrenyldeoxyuridine have been inserted efficiently into oligodeoxynucleotides probes using phosphoramidite chemistry. The probes exhibited abilities to fold into G-quadruplex structures and to bind metal cations (Na + and K + ). Folding properties of probes and their spectral behavior were examined by recording the UV-vis, fluorescence, and CD spectra as well as by analyzing melting profiles. Fluorescence characteristics and G-quadruplex folding of probes were also studied at the interface of cationic dioctadecyldimethylammonium bromide (DODAB) monolayer. Investigations included film balance measurements (π-A isotherms) and fluorescence spectra recording using a fiber optic accessory interfaced with a spectrofluorimeter. Copyright © 2017 Elsevier B.V. All rights reserved.

Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

DOE PAGES

Ge, Ting; Robbins, Mark O.; Perahia, Dvora; ...

2014-07-25

Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface.more » The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.« less

What determines the interfacial configuration of Nb/Al2O3 and Nb/MgO interface

PubMed Central

Du, J. L.; Fang, Y.; Fu, E. G.; Ding, X.; Yu, K. Y.; Wang, Y. G.; Wang, Y. Q.; Baldwin, J. K.; Wang, P. P.; Bai, Q.

2016-01-01

Nb films are deposited on single crystal Al2O3 (110) and MgO(111) substrates by e-beam evaporation technique. Structure of Nb films and orientation relationships (ORs) of Nb/Al2O3 and Nb/MgO interface are studied and compared by the combination of experiments and simulations. The experiments show that the Nb films obtain strong (110) texture, and the Nb film on Al2O3(110) substrate shows a higher crystalline quality than that on MgO(111) substrate. First principle calculations show that both the lattice mismatch and the strength of interface bonding play major roles in determining the crystalline perfection of Nb films and ORs between Nb films and single crystal ceramic substrates. The fundamental mechanisms for forming the interfacial configuration in terms of the lattice mismatch and the strength of interface bonding are discussed. PMID:27698458

Graphene Oxide Monolayer as a Compatibilizer at the Polymer-Polymer Interface for Stabilizing Polymer Bilayer Films against Dewetting.

PubMed

Kim, Tae-Ho; Kim, Hyeri; Choi, Ki-In; Yoo, Jeseung; Seo, Young-Soo; Lee, Jeong-Soo; Koo, Jaseung

2016-12-06

We investigate the effect of adding graphene oxide (GO) sheets at the polymer-polymer interface on the dewetting dynamics and compatibility of immiscible polymer bilayer films. GO monolayers are deposited at the poly(methyl methacrylate) (PMMA)-polystyrene (PS) interface by the Langmuir-Schaefer technique. GO monolayers are found to significantly inhibit the dewetting behavior of both PMMA films (on PS substrates) and PS films (on PMMA substrates). This can be interpreted in terms of an interfacial interaction between the GO sheets and these polymers, which is evidenced by the reduced contact angle of the dewet droplets. The favorable interaction of GO with both PS and PMMA facilitates compatibilization of the immiscible polymer bilayer films, thereby stabilizing their bilayer films against dewetting. This compatibilization effect is verified by neutron reflectivity measurements, which reveal that the addition of GO monolayers broadens the interface between PS and the deuterated PMMA films by 2.2 times over that of the bilayer in the absence of GO.

Interfacial Properties of Thin Films of Poly(vinyl ether)s with Architectural Design in Water

NASA Astrophysics Data System (ADS)

Oda, Yukari; Itagaki, Nozomi; Sugimoto, Sin; Kawaguchi, Daisuke; Matsuno, Hisao; Tanaka, Keiji

Precise design of primary structure and architecture of polymers leads to the well-defined structure, unique physical properties, and excellent functions not only in the bulk but also at the interfaces. We here constructed functional polymer interfaces in water based on the architectural design of poly(vinyl ether)s with oxyethylene side-chains (POEVE). A branched polymer with POEVE parts was preferentially segregated at the air interface in the matrix of poly(methyl methacrylate). As an alternative way to prepare the POEVE surface, the cross-linked hydrogel thin films were prepared. The moduli of the hydrogel films near the water interfaces, which were examined by force-distance curve measurements using atomic force microscopy, were greatly sensitive to the cross-linking density of the polymers. Diffuse interfaces of POEVE chains at the water interface make it possible to prevent the platelet adhesion on the films.

A study on the relationships between corrosion properties and chemistry of thermally oxidised surface films formed on polished commercial magnesium alloys AZ31 and AZ61

NASA Astrophysics Data System (ADS)

Feliu, Sebastián; Samaniego, Alejandro; Barranco, Violeta; El-Hadad, A. A.; Llorente, Irene; Serra, Carmen; Galván, J. C.

2014-03-01

This paper studies the changes in chemical composition of the thin oxide surface films induced by heating in air at 200 °C for time intervals from 5 min to 60 min on the freshly polished commercial AZ31 and AZ61 alloys with a view to better understanding their protective properties. This thermal treatment resulted in the formation of layers enriched in metallic aluminium at the interface between the outer MgO surface films and the bulk material. A strong link was found between the degree of metallic Al enrichment in the subsurface layer (from 10 to 15 at.%) observed by XPS (X-ray photoelectron spectroscopy) in the AZ61 treated samples and the increase in protective properties observed by EIS (electrochemical impedance spectroscopy) in the immersion test in 0.6 M NaCl. Heating for 5-60 min in air at 200 °C seems to be an effective, easy to perform and inexpensive method for increasing the corrosion resistance of the AZ61 alloy by approximately two or three times.

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film.

PubMed

Cen, Xi; Thron, Andrew M; Zhang, Xinming; van Benthem, Klaus

2017-07-01

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO 2 /Si interface structure, the majority of the metal/SiO 2 interface was Au/SiO 2 after annealing at 675°C for 1h. Void nucleation was predominantly observed at Au/Ni/SiO 2 triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO 2 interface sections is found to be energetically preferred over Ni/SiO 2 due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural and optical properties of Na-doped ZnO films

NASA Astrophysics Data System (ADS)

Akcan, D.; Gungor, A.; Arda, L.

2018-06-01

Zn1-xNaxO (x = 0.0-0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV-Vis-NIR spectrophotometer in 190-1100 nm range. The structure, morphology, and optical properties of thin films are presented.

In-situ deposition of sodium titanate thin film as anode for sodium-ion micro-batteries developed by pulsed laser deposition.

PubMed

Rambabu, A; Senthilkumar, B; Sada, K; Krupanidhi, S B; Barpanda, P

2018-03-15

Sodium-ion thin-film micro-batteries form a niche sector of energy storage devices. Sodium titanate, Na 2 Ti 6 O 13 (NTO) thin films were deposited by pulsed laser deposition (PLD) using solid-state synthesized polycrystalline Na 2 Ti 6 O 13 compound. The phase-purity and crystallinity of NTO in bulk and thin-film forms were confirmed by Rietveld refinement. Electron microscopy and atomic force microscopy revealed the formation of uniform ∼100 nm thin film with roughness of ∼4 nm consisting of homogeneous nanoscale grains. These PLD-deposited NTO thin-films, when tested in Na-half cell architecture, delivered a near theoretical reversible capacity close to 42 mA h g -1 involving Ti 4+ /Ti 3+ redox activity along with good cycling stability and rate kinetics. Na 2 Ti 6 O 13 can work as an efficient and safe anode in designing sodium-ion thin-film micro-batteries. Copyright © 2017 Elsevier Inc. All rights reserved.

Layer-by-layer composite film of nickel phthalocyanine and montmorillonite clay for synergistic effect on electrochemical detection of dopamine

NASA Astrophysics Data System (ADS)

de Lucena, Nathalia C.; Miyazaki, Celina M.; Shimizu, Flávio M.; Constantino, Carlos J. L.; Ferreira, Marystela

2018-04-01

Dopamine (DA) abnormal levels are related to diseases which makes important the development of fast, reliable, low-cost and sensitive devices for diagnosis and pharmaceutical controls. Nanostructured film composite of sodium montmorillonite clay (Na+MMT) and nickel phthalocyanine (NiTsPc) was self-assembled by layer-by-layer (LbL) technique and applied as electrochemical sensor for DA in the presence of common natural interferents as ascorbic acid (AA) and uric acid (UA). Three different LbL architecture films were investigated: LbL films of clay (PEI/Na+MMT) and phthalocyanine (PEI/NiTsPc) in a bilayer structure with a conventional polyelectrolyte (PEI) and a composite film formed by both materials to verify the synergistic effect in the LbL film in a quadri-layer assembly (PEI/Na+MMT/PEI/NiTsPc). Structural characterization indicated molecular level interactions between the layers forming the LbL films. The ITO/(PEI/Na+MMT/PEI/NiTsPc)10 electrode exhibited a LOD of 1.0 μmol L-1 and linear range 5-150 μmol L-1.

Surface effects of corrosive media on hardness, friction, and wear of materials

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Rengstorff, G. W. P.; Ishigaki, H.

1985-01-01

Hardness, friction, and wear experiments were conducted with magnesium oxide exposed to various corrosive media and also with elemental iron and nickel exposed to water and NaOH. Chlorides such as MgCl2 and sodium containing films were formed on cleaved magnesium oxide surfaces. The MgCl2 films softened the magnesium oxide surfaces and caused high friction and great deformation. Hardness was strongly influenced by the pH value of the HCl-containing solution. The lower the pH, the lower the microhardness. Neither the pH value of nor the immersion time in NaOH containing, NaCl containing, and HNO3 containing solutions influenced the microhardness of magnesium oxide. NaOH formed a protective and low friction film on iron surfaces. The coefficient of friction and the wear for iron were low at concentrations of NaOH higher than 0.01 N. An increase in NaOH concentration resulted in a decrease in the concentration of ferric oxide on the iron surface. It took less NaOH to form a protective, low friction film on nickel than on iron.

Interfacing superhydrophobic silica nanoparticle films with graphene and thermoplastic polyurethane for wear/abrasion resistance.

PubMed

Naderizadeh, Sara; Athanassiou, Athanassia; Bayer, Ilker S

2018-06-01

Nanoparticle films are one of the most suitable platforms for obtaining sub-micrometer and nanometer dual-scale surface texture required for liquid repellency. The assembly of superhydrophobic nanoparticles into conformal and strongly adherent films having abrasion-induced wear resistance still poses a significant challenge. Various techniques have been developed over the years to render nanoparticle films with good liquid repellent properties and transparency. However, forming abrasion resistant superhydrophobic nanoparticle films on hard surfaces is challenging. One possibility is to partially embed or weld nanoparticles in thin thermoplastic primers applied over metals. Hexamethyldisilazane-functionalized fumed silica nanoparticle films spray deposited on aluminum surfaces were rendered abrasion resistant by thermally welding them into thermoplastic polyurethane (TPU) primer applied a priori over aluminum. Different solvents, nanoparticle concentrations and annealing temperatures were studied to optimize nanoparticle film morphology and hydrophobicity. Thermal annealing at 150 °C enhanced stability and wear resistance of nanoparticle films. A thin thermal interface layer of graphene nanoplatelets (GnPs) between the primer and the nanoparticle film significantly improved superhydrophobic wear resistance after annealing. As such, superhydrophobic nanocomposite films with the GnPs thermal interface layer displayed superior abrasion-induced wear resistance under 20 kPa compared to films having no GnPs-based thermal interface. Copyright © 2018 Elsevier Inc. All rights reserved.

FRET study of G-quadruplex forming fluorescent oligonucleotide probes at the lipid monolayer interface.

PubMed

Swiatkowska, Angelika; Kosman, Joanna; Juskowiak, Bernard

2016-01-05

Spectral properties and G-quadruplex folding ability of fluorescent oligonucleotide probes at the cationic dioctadecyldimethylammonium bromide (DODAB) monolayer interface are reported. Two oligonucleotides, a 19-mer bearing thrombin binding aptamer sequence and a 21-mer with human telomeric sequence, were end-labeled with fluorescent groups (FAM and TAMRA) to give FRET probes F19T and F21T, respectively. The probes exhibited abilities to fold into a quadruplex structure and to bind metal cations (Na(+) and K(+)). Fluorescence spectra of G-quadruplex FRET probes at the monolayer interface are reported for the first time. Investigations included film balance measurements (π-A isotherms) and fluorescence spectra recording using a fiber optic accessory interfaced with a spectrofluorimeter. The effect of the presence of DODAB monolayer, metal cations and the surface pressure of monolayer on spectral behavior of FRET probes were examined. Adsorption of probe at the cationic monolayer interface resulted in the FRET signal enhancement even in the absence of metal cations. Variation in the monolayer surface pressure exerted rather modest effect on the spectral properties of probes. The fluorescence energy transfer efficiency of monolayer adsorbed probes increased significantly in the presence of sodium or potassium ion in subphase, which indicated that the probes retained their cation binding properties when adsorbed at the monolayer interface. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies on stability of PEC cells formed with CdS:Al films

NASA Astrophysics Data System (ADS)

Lokhande, C. D.; Pawar, S. H.

1984-02-01

Aluminum doped and undoped CdS films are deposited on stainless steel substrates by chemical bath deposition technique and are employed in PEC cells. The effects of heat treatment to photoanode and addition of salts like KCl and NaCl in an electrolyte on the stability of the PEC cells are studied. It is found that though the PEC cells formed with CdS films are stable in NaOH-Na 2S-S electrolyte, the stability of PEC cells formed with Al doped CdS films is achieved only after the addition of saturated salts in the electrolyte.

Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells.

PubMed

Chirilă, Adrian; Reinhard, Patrick; Pianezzi, Fabian; Bloesch, Patrick; Uhl, Alexander R; Fella, Carolin; Kranz, Lukas; Keller, Debora; Gretener, Christina; Hagendorfer, Harald; Jaeger, Dominik; Erni, Rolf; Nishiwaki, Shiro; Buecheler, Stephan; Tiwari, Ayodhya N

2013-12-01

Thin-film photovoltaic devices based on chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber layers show excellent light-to-power conversion efficiencies exceeding 20%. This high performance level requires a small amount of alkaline metals incorporated into the CIGS layer, naturally provided by soda lime glass substrates used for processing of champion devices. The use of flexible substrates requires distinct incorporation of the alkaline metals, and so far mainly Na was believed to be the most favourable element, whereas other alkaline metals have resulted in significantly inferior device performance. Here we present a new sequential post-deposition treatment of the CIGS layer with sodium and potassium fluoride that enables fabrication of flexible photovoltaic devices with a remarkable conversion efficiency due to modified interface properties and mitigation of optical losses in the CdS buffer layer. The described treatment leads to a significant depletion of Cu and Ga concentrations in the CIGS near-surface region and enables a significant thickness reduction of the CdS buffer layer without the commonly observed losses in photovoltaic parameters. Ion exchange processes, well known in other research areas, are proposed as underlying mechanisms responsible for the changes in chemical composition of the deposited CIGS layer and interface properties of the heterojunction.

Phase transition of LB films of mixed diblock copolymer at the air/water interface

NASA Astrophysics Data System (ADS)

Seo, Y. S.; Kim, K. S.; Samuilov, V.; Rafailovich, M. H.; Sokolov, J.; Lammertink, Rob G. H.; Vancso, G. J.

2000-03-01

We have studied the morphology of Langmuir blodgett films at the air/water interface of mixed diblock copolymer films. Solutions of poly(styrene-b-ferrocenyldimethylsilane) and PS-b-P2VP mixed in a ratio of 20/80 in chloroform were spread at the air/water interface. The morphology of the films was studied with AFM as a function of the surface pressure and the diblock copolymer molecular weight. The results show that the two diblock copolymers can be induced to mix at the air/water interface with increasing surface pressure. A reversible transition from spherical to cylindrical morphologies is induced in the mixture which can not be observed in films formed of the two components separately. The effective surface phase diagram as a function of block copolymer composition and pressure will be presented.

Interface thermal resistance of nanostructured FeCoCu film and Si substrate

NASA Astrophysics Data System (ADS)

Nikolaenko, Yuri M.; Medvedev, Yuri V.; Genenko, Yuri A.; Ghafari, Mohammad; Hahn, Horst

2006-05-01

Results of measurement of thermal resistance (RFS ) of film substrate interface of 10 nm (Fe1-x Cox )1-y Cuy film on Si substrate with 50 nm SiO2 sublayer are presented. The estimated magnitude is two orders greater then RFS of epitaxial manganite films on StTiO3 substrate with and without sublayer. The significant increase of RFS is explained by granular structure of film with average size of grain about 10 nm. In this case the additional thermal barier in the film-substrate interface is appeared. It provides the change of regime of phonons propagation from ballistic to diffusion one. The principle possibility of variation of RFS in wide range as a task of nanotechnology is discussed.

Utilizing van der Waals Slippery Interfaces to Enhance the Electrochemical Stability of Silicon Film Anodes in Lithium-Ion Batteries.

PubMed

Basu, Swastik; Suresh, Shravan; Ghatak, Kamalika; Bartolucci, Stephen F; Gupta, Tushar; Hundekar, Prateek; Kumar, Rajesh; Lu, Toh-Ming; Datta, Dibakar; Shi, Yunfeng; Koratkar, Nikhil

2018-04-25

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals "slippery" interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress "cycling" on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

Electrostatic modulation of the electronic properties of Dirac semimetal Na3Bi thin films

NASA Astrophysics Data System (ADS)

Hellerstedt, Jack; Yudhistira, Indra; Edmonds, Mark T.; Liu, Chang; Collins, James; Adam, Shaffique; Fuhrer, Michael S.

2017-10-01

Large-area thin films of topological Dirac semimetal Na3Bi are grown on amorphous SiO2:Si substrates to realize a field-effect transistor with the doped Si acting as a back gate. As-grown films show charge carrier mobilities exceeding 7 000 cm2/V s and carrier densities below 3 ×1018cm-3 , comparable to the best thin-film Na3Bi . An ambipolar field effect and minimum conductivity are observed, characteristic of Dirac electronic systems. The results are quantitatively understood within a model of disorder-induced charge inhomogeneity in topological Dirac semimetals. The hole mobility is significantly larger than the electron mobility in Na3Bi which we ascribe to the inverted band structure. When present, these holes dominate the transport properties.

The effect of Na on Cu-K-In-Se thin film growth

NASA Astrophysics Data System (ADS)

Muzzillo, Christopher P.; Tong, Ho Ming; Anderson, Timothy J.

2018-04-01

Co-evaporation of Cu-KF-In-Se was performed on substrates with varied Na supply. Compositions of interest for photovoltaic absorbers were studied, with ratios of (K + Cu)/In ∼ 0.85 and K/(K + Cu) ∼ 0-0.57. Bare soda-lime glass (SLG) substrates had the highest Na supply as measured by secondary ion mass spectrometry, while SLG/Mo and SLG/SiO2/Mo substrates led to 3x and 3000x less Na in the growing film, respectively. Increased Na supply favored Cu1-xKxInSe2 (CKIS) alloy formation as proven by X-ray diffraction (XRD), while decreased Na supply favored the formation of CuInSe2 + KInSe2 mixed-phase films. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the KInSe2 precipitates to be readily recognizable planar crystals. Extrinsic KF addition during film growth promoted diffusion of Na out from the various substrates and into the growing film, in agreement with previous reports. Time-resolved photoluminescence showed enhanced minority carrier lifetimes for films with moderate K compositions (0.04 < K/(K + Cu) < 0.14) grown on SLG/Mo. Due to the relatively high detection limit of KInSe2 by XRD and the low magnitude of chalcopyrite lattice shift for CKIS alloys with these compositions, it is unclear if the lifetime gains were associated with CKIS alloying, minor KInSe2 content, or both. The identified Na-K interdependency can be used to engineer alkali metal bonding in Cu(In,Ga)(Se,S)2 absorbers to optimize both initial and long-term photovoltaic power generation.

The effect of Na on Cu-K-In-Se thin film growth

DOE PAGES

Muzzillo, Christopher P.; Tong, Ho Ming; Anderson, Timothy J.

2018-02-27

Co-evaporation of Cu-KF-In-Se was performed on substrates with varied Na supply. Compositions of interest for photovoltaic absorbers were studied, with ratios of (K + Cu)/In ~ 0.85 and K/(K + Cu) ~ 0-0.57. Bare soda-lime glass (SLG) substrates had the highest Na supply as measured by secondary ion mass spectrometry, while SLG/Mo and SLG/SiO 2/Mo substrates led to 3x and 3000x less Na in the growing film, respectively. Increased Na supply favored Cu 1-xK xInSe 2 (CKIS) alloy formation as proven by X-ray diffraction (XRD), while decreased Na supply favored the formation of CuInSe 2 + KInSe 2 mixed-phase films.more » Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the KInSe 2 precipitates to be readily recognizable planar crystals. Extrinsic KF addition during film growth promoted diffusion of Na out from the various substrates and into the growing film, in agreement with previous reports. Time-resolved photoluminescence showed enhanced minority carrier lifetimes for films with moderate K compositions (0.04 < K/(K + Cu) < 0.14) grown on SLG/Mo. Due to the relatively high detection limit of KInSe 2 by XRD and the low magnitude of chalcopyrite lattice shift for CKIS alloys with these compositions, it is unclear if the lifetime gains were associated with CKIS alloying, minor KInSe 2 content, or both. The identified Na-K interdependency can be used to engineer alkali metal bonding in Cu(In,Ga)(Se,S) 2 absorbers to optimize both initial and long-term photovoltaic power generation.« less

The effect of Na on Cu-K-In-Se thin film growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzillo, Christopher P.; Tong, Ho Ming; Anderson, Timothy J.

Co-evaporation of Cu-KF-In-Se was performed on substrates with varied Na supply. Compositions of interest for photovoltaic absorbers were studied, with ratios of (K + Cu)/In ~ 0.85 and K/(K + Cu) ~ 0-0.57. Bare soda-lime glass (SLG) substrates had the highest Na supply as measured by secondary ion mass spectrometry, while SLG/Mo and SLG/SiO 2/Mo substrates led to 3x and 3000x less Na in the growing film, respectively. Increased Na supply favored Cu 1-xK xInSe 2 (CKIS) alloy formation as proven by X-ray diffraction (XRD), while decreased Na supply favored the formation of CuInSe 2 + KInSe 2 mixed-phase films.more » Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed the KInSe 2 precipitates to be readily recognizable planar crystals. Extrinsic KF addition during film growth promoted diffusion of Na out from the various substrates and into the growing film, in agreement with previous reports. Time-resolved photoluminescence showed enhanced minority carrier lifetimes for films with moderate K compositions (0.04 < K/(K + Cu) < 0.14) grown on SLG/Mo. Due to the relatively high detection limit of KInSe 2 by XRD and the low magnitude of chalcopyrite lattice shift for CKIS alloys with these compositions, it is unclear if the lifetime gains were associated with CKIS alloying, minor KInSe 2 content, or both. The identified Na-K interdependency can be used to engineer alkali metal bonding in Cu(In,Ga)(Se,S) 2 absorbers to optimize both initial and long-term photovoltaic power generation.« less

Oxide-Based Composite Electrolytes Using Na3Zr2Si2PO12/Na3PS4 Interfacial Ion Transfer.

PubMed

Noi, Kousuke; Nagata, Yuka; Hakari, Takashi; Suzuki, Kenji; Yubuchi, So; Ito, Yusuke; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro

2018-05-31

All-solid-state sodium batteries using Na 3 Zr 2 Si 2 PO 12 (NASICON) solid electrolytes are promising candidates for safe and low-cost advanced rechargeable battery systems. Although NASICON electrolytes have intrinsically high sodium-ion conductivities, their high sintering temperatures interfere with the immediate development of high-performance batteries. In this work, sintering-free NASICON-based composites with Na 3 PS 4 (NPS) glass ceramics were prepared to combine the high grain-bulk conductivity of NASICON and the interfacial formation ability of NPS. Before the composite preparation, the NASICON/NPS interfacial resistance was investigated by modeling the interface between the NASICON sintered ceramic and the NPS glass thin film. The interfacial ion-transfer resistance was very small above room temperature; the area-specific resistances at 25 and 100 °C were 15.8 and 0.40 Ω cm 2 , respectively. On the basis of this smooth ion transfer, NASICON-rich (70-90 wt %) NASICON-NPS composite powders were prepared by ball-milling fine powders of each component. The composite powders were well-densified by pressing at room temperature. Scanning electron microscopy observation showed highly dispersed sub-micrometer NASICON grains in a dense NPS matrix to form closed interfaces between the oxide and sulfide solid electrolytes. The composite green (unfired) compacts with 70 and 80 wt % NASICON exhibited high total conductivities at 100 °C of 1.1 × 10 -3 and 6.8 × 10 -4 S cm -1 , respectively. An all-solid-state Na 15 Sn 4 /TiS 2 cell was constructed using the 70 wt % NASICON composite electrolyte by the uniaxial pressing of the powder materials, and its discharge properties were evaluated at 100 °C. The cell showed the reversible capacities of about 120 mAh g -1 under the current density of 640 μA cm -2 . The prepared oxide-based composite electrolytes were thus successfully applied in all-solid-state sodium rechargeable batteries without sintering.

Photoelectrochemical molecular comb

DOEpatents

Thundat, Thomas G.; Ferrell, Thomas L.; Brown, Gilbert M.

2006-08-15

A method and apparatus for separating molecules. The apparatus includes a substrate having a surface. A film in contact with the surface defines a substrate/film interface. An electrode electrically connected to the film applies a voltage potential between the electrode and the substrate to form a depletion region in the substrate at the substrate/film interface. A photon energy source having an energy level greater than the potential is directed at the depletion region to form electron-hole pairs in the depletion region. At least one of the electron-hole pairs is separated by the potential into an independent electron and an independent hole having opposite charges and move in opposing directions. One of the electron and hole reach the substrate/film interface to create a photopotential in the film causing charged molecules in the film to move in response to the localized photovoltage.

Simulation of interface dislocations effect on polarization distribution of ferroelectric thin films

NASA Astrophysics Data System (ADS)

Zheng, Yue; Wang, Biao; Woo, C. H.

2006-02-01

Effects of interfacial dislocations on the properties of ferroelectric thin films are investigated, using the dynamic Ginzburg-Landau equation. Our results confirm the existence of a dead layer near the film/substrate interface. Due to the combined effects of the dislocations and the near-surface eigenstrain relaxation, the ferroelectric properties of about one-third of the film volume suffers.

Experimental studies on the nature of bonding of DNA/bipyridyl-(ethylenediamine)platinum(II) and DNA/netropsin complexes in solution and oriented wet-spun films

NASA Astrophysics Data System (ADS)

Marlowe, R. L.; Szabo, A.; Lee, S. A.; Rupprecht, A.

2002-03-01

The stability of complexes of NaDNA with bipyridyl-(ethylenediamine)platinum(II) (abbreviated [(bipy)Pt(en)]) and with netropsin has been studied using two techniques: (i) ultraviolet melting experiments were done on NaDNA/[(bipy)Pt(en)], showing that the [(bipy)Pt(en)] ligand stabilizes the DNA double helix structure; and (ii) swelling measurements (via optical microscopy) as a function of relative humidity were done on wet-spun oriented films of NaDNA/[(bipy)Pt(en)] and of NaDNA/netropsin. The swelling data shows that an irreversible transition of the films occurs at high relative humidity, first for the NaDNA/netropsin, then for pure NaDNA, and lastly for the NaDNA/[(bipy)Pt(en)]. These results are indicative that the [(bipy)Pt(en)] complex stabilizes the intermolecular bonds which mediate the film swelling characteristics. A model is suggested for the binding of [(bipy)Pt(en)] to DNA to explain why the swelling experiments show this ligand as increasing the intermolecular bond strength between the DNA double helices, while netropsin decreases this degree of stabilization.

Strain, temperature, and electric-field effects on the phase transition and piezoelectric responses of K0.5Na0.5NbO3 thin films

NASA Astrophysics Data System (ADS)

Zhou, Meng-Jun; Wang, Jian-Jun; Chen, Long-Qing; Nan, Ce-Wen

2018-04-01

A KNbO3-based solid solution system is environmentally friendly with good electromechanical performance. This work established the misfit strain-strain and temperature-strain phase diagrams for K0.5Na0.5NbO3 thin films and calculated the polarization switching, phase transition, and piezoelectric responses of K0.5Na0.5NbO3 thin films under various strains, temperatures, and electric fields. The results show that the piezoelectric coefficient d33 can be enhanced near the phase boundaries. For the ferroelectric phase with a nonzero out-of-plane polarization component, an optimal electric field is identified for maximizing d33, which is desired in applications such as thin-film piezoelectric micro-electromechanical systems, transducers for ultrasound medical imaging, and energy harvesting. The present results are expected to provide guidance for the future experimental study of KxNa1-xNbO3 thin films and the optimization of ferroelectric thin film-based devices.

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films

NASA Astrophysics Data System (ADS)

Schwarzkopf, J.; Braun, D.; Schmidbauer, M.; Duk, A.; Wördenweber, R.

2014-05-01

NaNbO3 thin films have been grown under anisotropic biaxial strain on several oxide substrates by liquid-delivery spin metalorganic chemical vapor deposition. Compressive lattice strain of different magnitude, induced by the deposition of NaNbO3 films with varying film thickness on NdGaO3 single crystalline substrates, leads to modifications of film orientation and phase symmetry, which are similar to the phase transitions in Pb-containing oxides near the morphotropic phase boundary. Piezoresponse force microscopy measurements exhibit large out-of-plane polarization components, but no distinctive domain structure, while C-V measurements indicate relaxor properties in these films. When tensile strain is provoked by the epitaxial growth on DyScO3, TbScO3, and GdScO3 single crystalline substrates, NaNbO3 films behave rather like a normal ferroelectric. The application of these rare-earth scandate substrates yields well-ordered ferroelectric stripe domains of the type a1/a2 with coherent domain walls aligned along the [001] substrate direction as long as the films are fully strained. With increasing plastic lattice relaxation, initially, a 2D domain pattern with still exclusively in-plane electric polarization, and finally, domains with in-plane and out-of-plane polar components evolve.

The Influence of a TiN Film on the Electronic Contribution to the Thermal Conductivity of a TiC Film in a TiN-TiC Layer System

NASA Astrophysics Data System (ADS)

Jagannadham, K.

2018-01-01

TiC and TiN films were deposited by reactive magnetron sputtering on Si substrates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization of the microstructure and interface structure have been carried out and the stoichiometric composition of TiC is determined. Thermal conductivity and interface thermal conductance between different layers in the films are evaluated by the transient thermo reflectance (TTR) and three-omega (3- ω) methods. The results showed that the thermal conductivity of the TiC films increased with temperature. The thermal conductivity of TiC in the absence of TiN is dominated by phonon contribution. The electronic contribution to the thermal conductivity of TiC in the presence of TiN is found to be more significant. The interface thermal conductance of the TiC/TiN interface is much larger than that of interfaces at Au/TiC, TiC/Si, or TiN/Si. The interface thermal conductance between TiC and TiN is reduced by the layer formed as a result of interdiffusion.

Interpolymer complexation: comparisons of bulk and interfacial structures.

PubMed

Cattoz, Beatrice; de Vos, Wiebe M; Cosgrove, Terence; Crossman, Martin; Espidel, Youssef; Prescott, Stuart W

2015-04-14

The interactions between the strong polyelectrolyte sodium poly(styrenesulfonate), NaPSS, and the neutral polymer poly(vinylpyrrolidone), PVP, were investigated in bulk and at the silica/solution interface using a combination of diffusion nuclear magnetic resonance spectroscopy (NMR), small-angle neutron scattering (SANS), solvent relaxation NMR, and ellipsometry. We show for the first time that complex formation occurs between NaPSS and PVP in solution; the complexes formed were shown not to be influenced by pH variation, whereas increasing the ionic strength increases the complexation of NaPSS but does not influence the PVP directly. The complexes formed contained a large proportion of NaPSS. Study of these interactions at the silica interface demonstrated that complexes also form at the nanoparticle interface where PVP is added in the system prior to NaPSS. For a constant PVP concentration and varying NaPSS concentration, the system remains stable until NaPSS is added in excess, which leads to depletion flocculation. Surface complex formation using the layer-by-layer technique was also reported at a planar silica interface.

Thermoelectric properties of epitaxial β-FeSi2 thin films grown on Si(111) substrates with various film qualities

NASA Astrophysics Data System (ADS)

Watanabe, Kentaro; Taniguchi, Tatsuhiko; Sakane, Shunya; Aoki, Shunsuke; Suzuki, Takeyuki; Fujita, Takeshi; Nakamura, Yoshiaki

2017-05-01

Si-based epitaxial β-FeSi2 thin films are attractive as materials for on-chip thermoelectric power generators. We investigated the structure, crystallinity, and thermoelectric properties of β-FeSi2 thin films epitaxially grown on Si(111) substrates by using three different techniques: conventional reactive deposition epitaxy followed by molecular beam epitaxy (RDE+MBE), solid phase epitaxy (SPE) based on codeposition of Fe and Si presented previously, and SPE followed by MBE (SPE+MBE) presented newly by this work. Their epitaxial growth temperatures were fixed at 530 °C for comparison. RDE+MBE thin films exhibited high crystalline quality, but rough surfaces and rugged β-FeSi2/Si(111) interfaces. On the other hand, SPE thin films showed flat surfaces and abrupt β-FeSi2/Si(111) interfaces but low crystallinity. We found that SPE+MBE thin films realized crystallinity higher than SPE thin films, and also had flatter surfaces and sharper interfaces than RDE+MBE thin films. In SPE+MBE thin film growth, due to the initial SPE process with low temperature codeposition, thermal interdiffusion of Fe and Si was suppressed, resulting in the surface flatness and abrupt interface. Second high temperature MBE process improved the crystallinity. We also investigated thermoelectric properties of these β-FeSi2 thin films. Structural factors affecting the thermoelectric properties of RDE+MBE, SPE, and SPE+MBE thin films were investigated.

Electrochemical preparation of carbon films with a Mo2C interlayer in LiCl-NaCl-Na2CO3 melts

NASA Astrophysics Data System (ADS)

Ge, Jianbang; Wang, Shuai; Zhang, Feng; Zhang, Long; Jiao, Handong; Zhu, Hongmin; Jiao, Shuqiang

2015-08-01

The electrodeposition of carbon films with a Mo2C interlayer was investigated in LiCl-NaCl-Na2CO3 melts at 900 °C. Cyclic voltammetry was applied to study the electrochemical reaction mechanism on Mo and Pt electrodes, indicating that, two reduction reactions including carbon deposition and carbon monoxide evolution, may take place on the two electrodes simultaneously during the cathodic sweep. Carbon films with a continuous Mo2C interlayer were prepared by constant voltage electrolysis, showing a good adhesion between Mo substrate and carbon films. The carbon films with a Mo2C interlayer were characterized using X-ray diffraction measurement, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The results reveal that carbon materials deposited on the electrodes are mainly composed of graphite and carbon diffusion in Mo (or Mo2C) leads to the formation and growth of Mo2C interlayer.

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

NASA Astrophysics Data System (ADS)

Sahin, Bünyamin; Kaya, Tolga

2016-01-01

In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.

An investigation of the fluid-structure interaction of piston/cylinder interface

NASA Astrophysics Data System (ADS)

Pelosi, Matteo

The piston/cylinder lubricating interface represents one of the most critical design elements of axial piston machines. Being a pure hydrodynamic bearing, the piston/cylinder interface fulfills simultaneously a bearing and sealing function under oscillating load conditions. Operating in an elastohydrodynamic lubrication regime, it also represents one of the main sources of power loss due to viscous friction and leakage flow. An accurate prediction of the time changing tribological interface characteristics in terms of fluid film thickness, dynamic pressure field, load carrying ability and energy dissipation is necessary to create more efficient interface designs. The aim of this work is to deepen the understanding of the main physical phenomena defining the piston/cylinder fluid film and to discover the impact of surface elastic deformations and heat transfer on the interface behavior. For this purpose, a unique fully coupled multi-body dynamics model has been developed to capture the complex fluid-structure interaction phenomena affecting the non-isothermal fluid film conditions. The model considers the squeeze film effect due to the piston micro-motion and the change in fluid film thickness due to the solid boundaries elastic deformations caused by the fluid film pressure and by the thermal strain. The model has been verified comparing the numerical results with measurements taken on special designed test pumps. The fluid film calculated dynamic pressure and temperature fields have been compared. Further validation has been accomplished comparing piston/cylinder axial viscous friction forces with measured data. The model has been used to study the piston/cylinder interface behavior of an existing axial piston unit operating at high load conditions. Numerical results are presented in this thesis.

AES study on the chemical composition of ferroelectric BaTiO3 thin films RF sputter-deposited on silicon

NASA Technical Reports Server (NTRS)

Dharmadhikari, V. S.; Grannemann, W. W.

1983-01-01

AES depth profiling data are presented for thin films of BaTiO3 deposited on silicon by RF sputtering. By profiling the sputtered BaTiO3/silicon structures, it was possible to study the chemical composition and the interface characteristics of thin films deposited on silicon at different substrate temperatures. All the films showed that external surface layers were present, up to a few tens of angstroms thick, the chemical composition of which differed from that of the main layer. The main layer had stable composition, whereas the intermediate film-substrate interface consisted of reduced TiO(2-x) oxides. The thickness of this intermediate layer was a function of substrate temperature. All the films showed an excess of barium at the interface. These results are important in the context of ferroelectric phenomena observed in BaTiO3 thin films.

Novel fabrication method for 3D microstructures using surface-activated bonding and its application to micro-mechanical parts

NASA Astrophysics Data System (ADS)

Yamada, Takayuki; Takahashi, Mutsuya; Ozawa, Takashi; Tawara, Satoshi; Goto, Takayuki

2002-11-01

The purpose of this work is to demonstrate that a novel fabrication method for 3-D microstructures (FORMULA) is applicable to fabrication of micro mechanical parts with a large flexibility. This method is a kind of layer manufacturing method of thin films for metallic or dielectric microstructures using surface-activated bonding (SAB). The bonding interfaces of thin films are investigated by transmission electron microscope (TEM). Voids were observed at the interfaces of both pure aluminum films and Al-Cu alloy films. The ratio of void on the Al-Cu/Al-Cu interface is much larger than that of Al/Al interface, although the films have the same surface roughness of 3nm in Ra (average roughness). And approximately 10nm-thick amorphous intermediate layers were found at the interfaces. Furthermore, we have fabricated a micro gear of 900μm in diameter and 200μm in height, which is about ten times as large as our previous test pieces. Overhung structures such as a bridge structure and a cantilever were also fabricated without supporting layers beneath them.

Effects of ion irradiation on the mechanical properties of SiNa wO xC yH z sol-gel derived thin films

NASA Astrophysics Data System (ADS)

Lucca, D. A.; Qi, Y.; Harriman, T. A.; Prenzel, T.; Wang, Y. Q.; Nastasi, M.; Dong, J.; Mehner, A.

2010-10-01

A study of the effects of ion irradiation of hybrid organic/inorganic modified silicate thin films on their mechanical properties is presented. NaOH catalyzed SiNa wO xC yH z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H + or 250 keV N 2+ at fluences ranging from 1 × 10 14 to 2.5 × 10 16 ions/cm 2. Nanoindentation was used to characterize the films. Changes in hardness and reduced elastic modulus were examined as a function of ion fluence and irradiating species. The resulting increases in hardness and reduced elastic modulus are compared to similarly processed acid catalyzed silicate thin films.

Impact of Sodium Contamination in Tin Sulfide Thin-Film Solar Cells

DOE PAGES

Steinmann, Vera; Brandt, Riley E.; Chakraborty, Rupak; ...

2016-02-12

Empirical observations show that sodium(Na) is a benign contaminant in some thin-filmsolar cells. Here, we intentionally contaminate thermally evaporated tin sulfide (SnS)thin-films with sodium and measure the SnS absorber properties and solar cellcharacteristics. The carrier concentration increases from 2 × 10 16 cm -3 to 4.3 × 10 17 cm -3 in Na-doped SnSthin-films, when using a 13 nm NaCl seed layer, which is detrimental for SnS photovoltaic applications but could make Na-doped SnS an attractive candidate in thermoelectrics. We observed trends in carrier concentration and found that it is in good agreement with density functional theory calculations, which predictmore » an acceptor-type NaSn defect with low formation energy.« less

Grafting titanium nitride surfaces with sodium styrene sulfonate thin films

PubMed Central

Zorn, Gilad; Migonney, Véronique; Castner, David G.

2014-01-01

The importance of titanium nitride lies in its high hardness and its remarkable resistance to wear and corrosion, which has led to its use as a coating for the heads of hip prostheses, dental implants and dental surgery tools. However, the usefulness of titanium nitride coatings for biomedical applications could be significantly enhanced by modifying their surface with a bioactive polymer film. The main focus of the present work was to graft a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film from titanium nitride surfaces via a two-step procedure: first modifying the surface with 3-methacryloxypropyltrimethoxysilane (MPS) and then grafting the pNaSS film from the MPS modified titanium through free radical polymerization. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used after each step to characterize success and completeness of each reaction. The surface region of the titanium nitride prior to MPS functionalization and NaSS grafting contained a mixture of titanium nitride, oxy-nitride, oxide species as well as adventitious surface contaminants. After MPS functionalization, Si was detected by XPS, and characteristic MPS fragments were detected by ToF-SIMS. After NaSS grafting, Na and S were detected by XPS and characteristic NaSS fragments were detected by ToF-SIMS. The XPS determined thicknesses of the MPS and NaSS overlayers were ∼1.5 and ∼1.7 nm, respectively. The pNaSS film density was estimated by the toluidine blue colorimetric assay to be 260 ± 70 ng/cm2. PMID:25280842

P-type single-crystalline ZnO films obtained by (Na,N) dual implantation through dynamic annealing process

NASA Astrophysics Data System (ADS)

Zhang, Zhiyuan; Huang, Jingyun; Chen, Shanshan; Pan, Xinhua; Chen, Lingxiang; Ye, Zhizhen

2018-02-01

Single-crystalline ZnO films were grown by plasma-assisted molecular beam epitaxy technique on c-plane sapphire substrates. The films have been implanted with fixed fluence of 130 keV Na and 90 keV N ions at 460 °C. It is observed that dually-implanted single crystalline ZnO films exhibit p-type characteristics with hole concentration in the range of 1.24 × 1016-1.34 × 1017 cm-3, hole mobilities between 0.65 and 8.37 cm2 V-1 s-1, and resistivities in the range of 53.3-80.7 Ω cm by Hall-effect measurements. There are no other secondary phase appearing, with (0 0 2) (c-plane) orientation after ion implantation as identified by the X-ray diffraction pattern. It is obtained that Na and N ions were successfully implanted and activated as acceptors measured by XPS and SIMS results. Also compared to other similar studies, lower amount of Na and N ions make p-type characteristics excellent as others deposited by traditional techniques. It is concluded that Na and N ion implantation and dynamic annealing are essential in forming p-type single-crystalline ZnO films.

Rice Starch Particle Interactions at Air/Aqueous Interfaces-Effect of Particle Hydrophobicity and Solution Ionic Strength.

PubMed

McNamee, Cathy E; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

Achieving 14.4% Alcohol-Based Solution-Processed Cu(In,Ga)(S,Se)2 Thin Film Solar Cell through Interface Engineering.

PubMed

Park, Gi Soon; Chu, Van Ben; Kim, Byoung Woo; Kim, Dong-Wook; Oh, Hyung-Suk; Hwang, Yun Jeong; Min, Byoung Koun

2018-03-28

An optimization of band alignment at the p-n junction interface is realized on alcohol-based solution-processed Cu(In,Ga)(S,Se) 2 (CIGS) thin film solar cells, achieving a power-conversion-efficiency (PCE) of 14.4%. To obtain a CIGS thin film suitable for interface engineering, we designed a novel "3-step chalcogenization process" for Cu 2- x Se-derived grain growth and a double band gap grading structure. Considering S-rich surface of the CIGS thin film, an alternative ternary (Cd,Zn)S buffer layer is adopted to build favorable "spike" type conduction band alignment instead of "cliff" type. Suppression of interface recombination is elucidated by comparing recombination activation energies using a dark J- V- T analysis.

Strong modification of thin film properties due to screening across the interface

NASA Astrophysics Data System (ADS)

Altendorf, S. G.; Reisner, A.; Tam, B.; Meneghin, F.; Wirth, S.; Tjeng, L. H.

2018-04-01

We report on our investigation of the influence of screening across the interface on the properties of semiconducting thin films. Using EuO as a well-defined model material, layers of various thickness deposited on yttria-stabilized zirconia (100) substrates were covered half with Mg metal and half with the wide-band-gap insulator MgO. We observed that the Curie temperature for the thinnest films is significantly higher for the part which is interfaced with the metal compared to the part which is interfaced with the insulator. We infer that the proximity of a polarizable medium reduces the energies of virtual charge excitations and thus increases the effective exchange interactions, a strong effect that can be utilized systematically for the design of thin film and multilayer systems.

The film tells the story: Physical-chemical characteristics of IgG at the liquid-air interface.

PubMed

Koepf, Ellen; Schroeder, Rudolf; Brezesinski, Gerald; Friess, Wolfgang

2017-10-01

The presence of liquid-air interfaces in protein pharmaceuticals is known to negatively impact product stability. Nevertheless, the mechanisms behind interface-related protein aggregation are not yet fully understood. Little is known about the physical-chemical behavior of proteins adsorbed to the interface. Therefore, the combinatorial use of appropriate surface-sensitive analytical methods such as Langmuir trough experiments, Infrared Reflection-Absorption Spectroscopy (IRRAS), Brewster Angle Microscopy (BAM), and Atomic Force Microscopy (AFM) is highly expedient to uncover structures and events at the liquid-air interface directly. Concentration-dependent adsorption of a human immunoglobulin G (IgG) and characteristic surface-pressure/area isotherms substantiated the amphiphilic nature of the protein molecules as well as the formation of a compressible protein film at the liquid-air interface. Upon compression, the IgG molecules do not readily desorb but form a highly compressible interfacial film. IRRA spectra proved not only the presence of the protein at the interface, but also showed that the secondary structure does not change considerably during adsorption or compression. IRRAS experiments at different angles of incidence indicated that the film thickness and/or packing density increases upon compression. Furthermore, BAM images exposed the presence of a coherent but heterogeneous distribution of the protein at the interface. Topographical differences within the protein film after adsorption, compression and decompression were revealed using underwater AFM. The combinatorial use of physical-chemical, spectroscopic and microscopic methods provided useful insights into the liquid-air interfacial protein behavior and revealed the formation of a continuous but inhomogeneous film of native-like protein molecules whose topographical appearance is affected by compressive forces. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of nucleation and growth processes of diamond films by atomic force microscopy

NASA Technical Reports Server (NTRS)

George, M. A.; Burger, A.; Collins, W. E.; Davidson, J. L.; Barnes, A. V.; Tolk, N. H.

1994-01-01

The nucleation and growth of plasma-enhanced chemical-vapor deposited polycrystalline diamond films were studied using atomic force microscopy (AFM). AFM images were obtained for (1) nucleated diamond films produced from depositions that were terminated during the initial stages of growth, (2) the silicon substrate-diamond film interface side of diamond films (1-4 micrometers thick) removed from the original surface of the substrate, and (3) the cross-sectional fracture surface of the film, including the Si/diamond interface. Pronounced tip effects were observed for early-stage diamond nucleation attributed to tip convolution in the AFM images. AFM images of the film's cross section and interface, however, were not highly affected by tip convolution, and the images indicate that the surface of the silicon substrate is initially covered by a small grained polycrystalline-like film and the formation of this precursor film is followed by nucleation of the diamond film on top of this layer. X-ray photoelectron spectroscopy spectra indicate that some silicon carbide is present in the precursor layer.

Ultrasonic cavitation erosion of Ti in 0.35% NaCl solution with bubbling oxygen and nitrogen.

PubMed

Li, D G; Wang, J D; Chen, D R; Liang, P

2015-09-01

The influences of oxygen and nitrogen on the ultrasonic cavitation erosion of Ti in 0.35%NaCl solution at room temperature, were investigated using a magnetostrictive-induced ultrasonic cavitation erosion (CE) facility and scanning electron microscopy (SEM). The roles of oxygen and nitrogen in the composition and the electronic property of the passive film on Ti, were studied by Mott-Schottky plot and X-ray photoelectron spectroscopy (XPS). The results showed that the mass loss of Ti in 0.35%NaCl solution increased with increasing cavitation time. Bubbling oxygen can evidently increase the resistance of ultrasonic cavitation erosion comparing with bubbling nitrogen. XPS results showed that the thickness of the passive film on Ti in 0.35%NaCl solution in the case of bubbling oxygen for 3 weeks, was about 7 nm, and the passive film was mainly composed of TiO2 with an anatase structure. While TiO2 with a rutile structure was found to be the major component of the passive film on Ti in 0.35%NaCl solution in the case of bubbling nitrogen for 3 weeks, and the film thickness was 5 nm. The results extracted from Mott-Schottky plot showed that the passive film on Ti in the case of bubbling oxygen had more donor density than the passive film on Ti in the case of bubbling nitrogen. Copyright © 2015 Elsevier B.V. All rights reserved.

Microstructures, mechanical behavior and strengthening mechanism of TiSiCN nanocomposite films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wei; Liu, Ping; Xue, Zenghui

Recently, the arguments have existed in the strengthening mechanism and microstructural model of the nanocomposite film due to lack of the convincible experimental evidences. In this investigation, the quarternary TiSiCN nanocomposite films with the different C and Si contents are synthesized by the reactive-magnetron-sputtering technique. The TiSiCN film is characterized as the nanocomposite structure with the TiN nanocrystallites surrounded by the (Si 3N 4 + C + CN x) interface phase. When the C/Si content ratio is 2:2, the TiSiCN nanocomposite film is remarkably strengthened with the maximal hardness and elastic modulus of 46.1 GPa and 425 GPa, respectively. Meanwhile,more » the (Si 3N 4 + C + CN x) interfaces exhibit as a crystallized form, which can coordinate the growth misorientations and maintain the coherently epitaxial growth between the TiN nanocrystallites and interfaces. Through the high-resolution transmission electron microscopy (HRTEM) observations, this investigation firstly provides the direct experimental evidence for the crystallized feature of the interfaces when the TiSiCN nanocomposite film is strengthened, suggesting that the strengthening effect of the TiSiCN nanocomposite film can be attributed to the coherent-interface strengthening mechanism, which is expressed as the “nc-TiN/c-Si 3N 4/c-C/c-CN x” model.« less

Microstructures, mechanical behavior and strengthening mechanism of TiSiCN nanocomposite films

DOE PAGES

Li, Wei; Liu, Ping; Xue, Zenghui; ...

2017-05-18

Recently, the arguments have existed in the strengthening mechanism and microstructural model of the nanocomposite film due to lack of the convincible experimental evidences. In this investigation, the quarternary TiSiCN nanocomposite films with the different C and Si contents are synthesized by the reactive-magnetron-sputtering technique. The TiSiCN film is characterized as the nanocomposite structure with the TiN nanocrystallites surrounded by the (Si 3N 4 + C + CN x) interface phase. When the C/Si content ratio is 2:2, the TiSiCN nanocomposite film is remarkably strengthened with the maximal hardness and elastic modulus of 46.1 GPa and 425 GPa, respectively. Meanwhile,more » the (Si 3N 4 + C + CN x) interfaces exhibit as a crystallized form, which can coordinate the growth misorientations and maintain the coherently epitaxial growth between the TiN nanocrystallites and interfaces. Through the high-resolution transmission electron microscopy (HRTEM) observations, this investigation firstly provides the direct experimental evidence for the crystallized feature of the interfaces when the TiSiCN nanocomposite film is strengthened, suggesting that the strengthening effect of the TiSiCN nanocomposite film can be attributed to the coherent-interface strengthening mechanism, which is expressed as the “nc-TiN/c-Si 3N 4/c-C/c-CN x” model.« less

Measuring interactions between polydimethylsiloxane and serum proteins at the air-water interface.

PubMed

Liao, Zhengzheng; Hsieh, Wan-Ting; Baumgart, Tobias; Dmochowski, Ivan J

2013-07-30

The interaction between synthetic polymers and proteins at interfaces is relevant to basic science as well as a wide range of applications in biotechnology and medicine. One particularly common and important interface is the air-water interface (AWI). Due to the special energetics and dynamics of molecules at the AWI, the interplay between synthetic polymer and protein can be very different from that in bulk solution. In this paper, we applied the Langmuir-Blodgett technique and fluorescence microscopy to investigate how the compression state of polydimethylsiloxane (PDMS) film at the AWI affects the subsequent adsorption of serum protein [e.g., human serum albumin (HSA) or immunoglobulin G (IgG)] and the interaction between PDMS and protein. Of particular note is our observation of circular PDMS domains with micrometer diameters that form at the AWI in the highly compressed state of the surface film: proteins were shown to adsorb preferentially to the surface of these circular PDMS domains, accompanied by a greater than 4-fold increase in protein found in the interfacial film. The PDMS-only film and the PDMS-IgG composite film were transferred to cover glass, and platinum-carbon replicas of the transferred films were further characterized by scanning electron microscopy and atomic force microscopy. We conclude that the structure of the PDMS film greatly affects the amount and distribution of protein at the interface.

The structure of oleamide films at the aluminum/oil interface and aluminum/air interface studied by Sum Frequency Generation (SFG) vibrational spectroscopy and Reflection Absorption Infrared Spectroscopy (RAIRS).

PubMed

Casford, Michael T L; Davies, Paul B

2009-08-01

The structure of oleamide (cis-9-octadecenamide) films on aluminum has been investigated by sum frequency generation vibrational spectroscopy (SFG) and reflection absorption infrared spectroscopy (RAIRS). Three different film deposition strategies were investigated: (i) films formed by equilibrium adsorption from oleamide solutions in oil, (ii) Langmuir-Blodgett films cast at 1 and 25 mN m(-1), (iii) thick spin-cast films. Both L-B and spin-cast films were examined in air and under oil. The adsorbate formed in the 1 mN m(-1) film in air showed little orientational order. For this film, the spectroscopic results and the ellipsometric thickness point to a relatively conformationally disordered monolayer that is oriented principally in the plane of the interface. Direct adsorption to the metal interface from oil results in SFG spectra of oleamide that are comparable to those observed for the 1 mN m(-1) L-B film in air. In contrast, SFG and RAIRS results for the 25 mN m(-1) film in air and SFG spectra of the spin-cast film in air both show strong conformational ordering and orientational alignment normal to the interface. The 25 mN m(-1) film has an ellipsometric thickness almost twice that of the 1 mN m(-1) L-B film. Taken in combination with the spectroscopic results, this is indicative of a well packed monolayer in air in which the hydrocarbon chain is in an essentially defect-free extended conformation with the methyl terminus oriented away from the surface. A similar structure is also deduced for the surface of the spin-cast film in air. Upon immersion of the 25 mN m(-1) L-B film in oil the SFG spectra show that this film rapidly adopts a relatively disordered structure similar to that seen for the 1 mN m(-1) L-B film in air. Immersion of the spin-cast film in oil results in the gradual disordering of the amide film over a period of several days until the observed spectra become essentially identical to those observed for direct adsorption of oleamide from oil.

Electron solvation by polar molecules: the interaction of Na atoms with solid methanol films studied with MIES and density functional theory calculations.

PubMed

Borodin, A; Höfft, O; Kahnert, U; Kempter, V; Ferro, Y; Allouche, A

2004-05-08

The interaction of Na atoms with CH(3)OH films was studied with metastable impact electron spectroscopy (MIES) under UHV conditions. The films were grown at 90(+/-10) K on tungsten substrates and exposed to Na. Na-induced formation of methoxy (CH(3)O) species takes place, and Na atoms become ionized. At small Na exposures the outermost solvent layer remains largely intact as concluded from the absence of MIES signals caused by the reaction products. However, emission from CH(3)O, located at the film surface, occurs at larger exposures. In the same exposure range also Na species can be detected at the surface. The spectral feature from 3s Na ionization occurs at an energetic position different from that found for metals or semiconductors. The results are compared with density functional theory calculations [see Y. Ferro, A. Allouche, and V. Kempter, J. Chem. Phys. 120, 8683 (2004), preceding paper]. Experiment and theory agree in the energetic positions of the main spectral features from the methanol and sodium ionization. The calculations suggest that the 3s Na emission observed experimentally originates from solvated 3s electrons which are located far from the Na core and become stabilized by solvent molecules. The simultaneous emergence of emission from CH(3)O and from solvated 3s electrons suggests that the delocalization and, consequently, the solvation play an important role in the Na-induced formation of CH(3)O from CH(3)OH. (c) 2004 American Institute of Physics.

Langmuir Films of Flexible Polymers Transferred to Aqueous/Liquid Crystal Interfaces Induce Uniform Azimuthal Alignment of the Liquid Crystal

PubMed Central

Kinsinger, Michael I.; Buck, Maren E.; Meli, Maria-Victoria; Abbott, Nicholas L.; Lynn, David M.

2009-01-01

We reported recently that amphiphilic polymers can be assembled at interfaces created between aqueous phases and thermotropic liquid crystals (LCs) in ways that (i) couple the organization of the polymer to the order of the LC and (ii) respond to changes in the properties of aqueous phases that can be characterized as changes in the optical appearance of the LC. This investigation sought to characterize the behavior of aqueous-LC interfaces decorated with uniaxially compressed thin films of polymers transferred by Langmuir-Schaefer (LS) transfer. Here, we report physicochemical characterization of interfaces created between aqueous phases and the thermotropic LC 4-cyano-4’-pentylbiphenyl (5CB) decorated with Langmuir films of a novel amphiphilic polymer (polymer 1), synthesized by the addition of hydrophobic and hydrophilic side chains to poly(2-vinyl-4,4’-dimethylazlactone). Initial characterization of this system resulted in the unexpected observation of uniform azimuthal alignment of 5CB after LS transfer of the polymer films to aqueous-5CB interfaces. This paper describes characterization of Langmuir films of polymer 1 hosted at aqueous-5CB interfaces as well as the results of our investigations into the origins of the uniform ordering of the LC observed upon LS transfer. Our results, when combined, support the conclusion that uniform azimuthal alignment of 5CB is the result of long-range ordering of polymer chains in the Langmuir films (in a preferred direction orthogonal to the direction of compression) that is generated during uniaxial compression of the films prior to LS transfer. Although past studies of Langmuir films of polymers at aqueous-air interfaces have demonstrated that in-plane alignment of polymer backbones can be induced by uniaxial compression, these past reports have generally made use of polymers with rigid backbones. One important outcome of this current study is thus the observation of anisotropy and long-range order in Langmuir films of a novel flexible polymer. A second important outcome is the observation that the existence, extent, and dynamics of this order can be identified and characterized optically by transfer of the Langmuir film to a thin film of LC. Additional characterization of Langmuir films of two other flexible polymers [poly(methyl methacrylate) and poly(vinyl stearate)] using this method also resulted in uniform azimuthal alignment of 5CB, suggesting that the generation of long-range order in uniaxially compressed Langmuir films of polymers may also occur more generally over a broader range of polymers with flexible backbones. PMID:19836025

Interfacial Coupling-Induced Ferromagnetic Insulator Phase in Manganite Film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Bangmin; Wu, Lijun; Yin, Wei-Guo

Interfaces with subtle difference in atomic and electronic structures in perovskite ABO3 heterostructures often yield intriguingly different properties, yet their exact roles remain elusive. Here, we report an integrated study of unusual transport, magnetic, and structural properties of Pr0.67Sr0.33MnO3 (PSMO) film on SrTiO3 (STO) substrate. The variations in out-of-plane lattice constant and BO6 octahedral rotation across the PSMO/STO interface strongly depend on the thickness of PSMO films. In the 12-nm film, a new interface-sensitive ferromagnetic polaronic insulator (FI’) phase is formed during the cubic-to-tetragonal phase transition of STO, apparently due to enhanced electron-phonon interaction and atomic disorder in the film.more » The transport properties of the FI’ phase in the 30-nm film are masked because of the reduced interfacial effect and smaller interface-to-volume ratio. This work demonstrates how thickness-dependent interfacial coupling leads to formation of the theoretically predicted novel ferromagnetic-polaronic insulator in systems, as illustrated in a new phase diagram, that are otherwise ferromagnetic metals (FM) in bulk form.« less

Leaf gas films delay salt entry and enhance underwater photosynthesis and internal aeration of Melilotus siculus submerged in saline water.

PubMed

Teakle, Natasha Lea; Colmer, Timothy David; Pedersen, Ole

2014-10-01

A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M. siculus survived complete submergence of 1 week at low salinity (up to 50 mol m(-3) NaCl), but did not recover following de-submergence from 100 mol m(-3) NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3 d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na(+) and Cl(-) intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K(+) than those with intact gas films. This study has demonstrated that leaf gas films reduce Na(+) and Cl(-) ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water. © 2014 John Wiley & Sons Ltd.

Extracting interface locations in multilayer polymer waveguide films using scanning angle Raman spectroscopy

DOE PAGES

Bobbitt, Jonathan M.; Smith, Emily A.

2017-11-09

There is an increasing demand for nondestructive in situ techniques that measure chemical content, total thickness, and interface locations for multilayer polymer films, and SA Raman spectroscopy in combination with appropriate data models can provide this information. A scanning angle (SA) Raman spectroscopy method was developed to measure the chemical composition of multilayer polymer waveguide films and to extract the location of buried interfaces between polymer layers with 7–80-nm axial spatial resolution. The SA Raman method measures Raman spectra as the incident angle of light upon a prism-coupled thin film is scanned. Six multilayer films consisting of poly(methyl methacrylate)/polystyrene ormore » poly(methyl methacrylate)/polystyrene/poly(methyl methacrylate) were prepared with total thicknesses ranging from 330-1260 nm. The interface locations were varied by altering the individual layer thicknesses between 140-680 nm. The Raman amplitude ratio of the 1605 cm -1 peak for PS and 812 cm -1 peak for PMMA was used in calculations of the electric field intensity within the polymer layers to model the SA Raman data and extract the total thickness and interface locations. There is an average 8% and 7% difference in the measured thickness between the SA Raman and profilometry measurements for bilayer and trilayer films, respectively.« less

Extracting interface locations in multilayer polymer waveguide films using scanning angle Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobbitt, Jonathan M.; Smith, Emily A.

There is an increasing demand for nondestructive in situ techniques that measure chemical content, total thickness, and interface locations for multilayer polymer films, and SA Raman spectroscopy in combination with appropriate data models can provide this information. A scanning angle (SA) Raman spectroscopy method was developed to measure the chemical composition of multilayer polymer waveguide films and to extract the location of buried interfaces between polymer layers with 7–80-nm axial spatial resolution. The SA Raman method measures Raman spectra as the incident angle of light upon a prism-coupled thin film is scanned. Six multilayer films consisting of poly(methyl methacrylate)/polystyrene ormore » poly(methyl methacrylate)/polystyrene/poly(methyl methacrylate) were prepared with total thicknesses ranging from 330-1260 nm. The interface locations were varied by altering the individual layer thicknesses between 140-680 nm. The Raman amplitude ratio of the 1605 cm -1 peak for PS and 812 cm -1 peak for PMMA was used in calculations of the electric field intensity within the polymer layers to model the SA Raman data and extract the total thickness and interface locations. There is an average 8% and 7% difference in the measured thickness between the SA Raman and profilometry measurements for bilayer and trilayer films, respectively.« less

Application of scanning angle Raman spectroscopy for determining the location of buried polymer interfaces with tens of nanometer precision

DOE PAGES

Damin, Craig A.; Nguyen, Vy H. T.; Niyibizi, Auguste S.; ...

2015-02-11

In this study, near-infrared scanning angle (SA) Raman spectroscopy was utilized to determine the interface location in bilayer films (a stack of two polymer layers) of polystyrene (PS) and polycarbonate (PC). Finite-difference-time-domain (FDTD) calculations of the sum square electric field (SSEF) for films with total bilayer thicknesses of 1200–3600 nm were used to construct models for simultaneously measuring the film thickness and the location of the buried interface between the PS and PC layers. Samples with total thicknesses of 1320, 1890, 2300, and 2750 nm and varying PS/PC interface locations were analyzed using SA Raman spectroscopy. Comparing SA Raman spectroscopymore » and optical profilometry measurements, the average percent difference in the total bilayer thickness was 2.0% for films less than ~2300 nm thick. The average percent difference in the thickness of the PS layer, which reflects the interface location, was 2.5% when the PS layer was less than ~1800 nm. SA Raman spectroscopy has been shown to be a viable, non-destructive method capable of determining the total bilayer thickness and buried interface location for bilayer samples consisting of thin polymer films with comparable indices of refraction.« less

Interfacial coupling and polarization of perovskite ABO3 heterostructures

NASA Astrophysics Data System (ADS)

Wu, Lijun; Wang, Zhen; Zhang, Bangmin; Yu, Liping; Chow, G. M.; Tao, Jing; Han, Myung-Geun; Guo, Hangwen; Chen, Lina; Plummer, E. W.; Zhang, Jiandi; Zhu, Yimei

2017-02-01

Interfaces with subtle difference in atomic and electronic structures in perovskite ABO3 heterostructures often yield intriguingly different properties, yet their exact roles remain elusive. In this article, we report an integrated study of unusual transport, magnetic, and structural properties of Pr0.67Sr0.33MnO3 (PSMO) films and La0.67Sr0.33MnO3 (LSMO) films of various thicknesses on SrTiO3 (STO) substrate. In particular, using atomically resolved imaging and electron energy-loss spectroscopy (EELS), we measured interface related local lattice distortion, BO6 octahedral rotation and cation-anion displacement induced polarization. In the very thin PSMO film, an unexpected interface-induced ferromagnetic polaronic insulator phase was observed during the cubic-to-tetragonal phase transition of the substrate STO, due to the enhanced electron-phonon interaction and atomic disorder in the film. On the other hand, for the very thin LSMO films we observed a remarkably deep polarization in non-ferroelectric STO substrate near the interface. Combining the experimental results with first principles calculations, we propose that the observed deep polarization is induced by an electric field originating from oxygen vacancies that extend beyond a dozen unit-cells from the interface, thus providing important evidence of the role of defects in the emergent interface properties of transition metal oxides.

Sublimable chloroquinolinate lanthanoid single-ion magnets deposited on ferromagnetic electrodes.

PubMed

Miralles, Sara G; Bedoya-Pinto, Amilcar; Baldoví, José J; Cañon-Mancisidor, Walter; Prado, Yoann; Prima-Garcia, Helena; Gaita-Ariño, Alejandro; Mínguez Espallargas, Guillermo; Hueso, Luis E; Coronado, Eugenio

2018-01-07

A new family of chloroquinolinate lanthanoid complexes of the formula A + [Ln(5,7Cl 2 q) 4 ] - , with Ln = Y 3+ , Tb 3+ and Dy 3+ and A + = Na + , NEt 4 + and K 0.5 (NEt 4 ) 0.5 + , is studied, both in bulk and as thin films. Several members of the family are found to present single-molecule magnetic behavior in bulk. Interestingly, the sodium salts can be sublimed under high vacuum conditions retaining their molecular structures and magnetic properties. These thermally stable compounds have been deposited on different substrates (Al 2 O 3 , Au and NiFe). The magnetic properties of these molecular films show the appearance of cusps in the zero-field cooled curves when they are deposited on permalloy (NiFe). This indicates a magnetic blocking caused by the interaction between the single-ion magnet and the ferromagnet. X-ray absorption spectroscopy confirms the formation of hybrid states at the molecule/metal interface.

Nanometric organisation in blends of gellan/xyloglucan hydrogels.

PubMed

de Souza, Clayton F; Riegel-Vidotti, Izabel C; Cardoso, Mateus B; Ono, Lucy; Lucyszyn, Neoli; Lubambo, Adriana F; Sens, Camila V; Grein-Iankovski, Aline; Sierakowski, Maria Rita

2014-12-19

Mixtures of gellan gum (GL) and a xyloglucan (XGJ) extracted from Hymenaea courbaril seeds were prepared in a solution of 0.15 mol L(-1) NaCl. Rheology measurements revealed that 2.4 g L(-1) pure GL formed a brittle hydrogel, and GL-XGJ blends showed improved pseudoplastic character with higher XGJ contents. SAXS analyses showed that the Rg dimensions ranged from 1.3 to 4.9 nm, with larger values occurring as the amount of XGJ increased, and diffusion tests indicated that better diffusion of methylene blue dye was obtained in the network with a higher XGJ content. AFM topographic images of the films deposited onto mica revealed fewer heterogeneous surfaces with increased XGJ contents. The water contact angle revealed more hydrophobic character on all of the films, and the wettability decreased with increasing amounts of XGJ. Therefore, the demonstrated benefit of using XGJ blends is the production of a soft material with improved interface properties. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of the conjugation of whey proteins with gellan polysaccharides on surfactant-induced competitive displacement from the air-water interface.

PubMed

Cai, B; Ikeda, S

2016-08-01

Whey proteins can be used to stabilize foams and emulsions against coalescence because of their ability to form viscoelastic films at the interface that resist film rupture on collision between colloidal particles. However, whey proteins are competitively displaced from the interface if small-molecule surfactants are added, leading to destabilization of the entire system. This is because surfactants are more effective in molecular packing at the interface, and they lower interfacial tension to a greater degree than whey proteins do, but their interfacial films are poor in viscoelasticity. We hypothesized that whey proteins would become more resistant to surfactant-induced competitive displacement if they were conjugated with network-forming polysaccharides. The protein moiety of the conjugate would be expected to enable its adsorption to the interface, and the polysaccharide moiety would be expected to form self-assembled networks, strengthening the interfacial film as a whole. In this study, whey proteins were conjugated with gellan polysaccharides using the Maillard reaction. Atomic force microscopy images of interfacial films formed by the whey protein-gellan conjugate at the air-water interface and transferred onto mica sheets using the Langmuir-Blodgett method revealed that gellan did form self-assembled networks at the interface and that interfacial films also contained a large number of unconjugated whey protein molecules. Following the addition of a small-molecule surfactant (Tween 20) to the sub-phase, surface pressure increased, indicating spontaneous adsorption of surfactants to the interface. Atomic force microscopy images showed decreases in interfacial area coverage by whey proteins as surface pressure increased. At a given surface pressure, the interfacial area coverage by whey protein-gellan conjugates was greater than coverage by unconjugated whey proteins, confirming that whey proteins became more resistant to surfactant-induced displacement after conjugation with gellan. Furthermore, gellan molecules added to the sub-phase after the formation of a monolayer of whey proteins at the air-water interface did not adsorb to the interfacial protein film. These results provide a molecular basis for designing interfacial structures to enhance the stability of colloidal systems. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Unraveling the electrolyte properties of Na3SbS4 through computation and experiment

NASA Astrophysics Data System (ADS)

Rush, Larry E.; Hood, Zachary D.; Holzwarth, N. A. W.

2017-12-01

Solid-state sodium electrolytes are expected to improve next-generation batteries on the basis of favorable energy density and reduced cost. Na3SbS4 represents a new solid-state ion conductor with high ionic conductivities in the mS/cm range. Here, we explore the tetragonal phase of Na3SbS4 and its interface with metallic sodium anode using a combination of experiments and first-principles calculations. The computed Na-ion vacancy migration energies of 0.1 eV are smaller than the value inferred from experiment, suggesting that grain boundaries or other factors dominate the experimental systems. Analysis of symmetric cells of the electrolyte—Na/Na 3SbS4/Na —show that a conductive solid electrolyte interphase forms. Computer simulations infer that the interface is likely to be related to Na3SbS3 , involving the conversion of the tetrahedral SbS43 - ions of the bulk electrolyte into trigonal pyramidal SbS33 - ions at the interface.

Microstructural investigation of nickel silicide thin films and the silicide-silicon interface using transmission electron microscopy.

PubMed

Bhaskaran, M; Sriram, S; Mitchell, D R G; Short, K T; Holland, A S; Mitchell, A

2009-01-01

This article discusses the results of transmission electron microscopy (TEM)-based investigation of nickel silicide (NiSi) thin films grown on silicon. Nickel silicide is currently used as the CMOS technology standard for local interconnects and in electrical contacts. Films were characterized with a range of TEM-based techniques along with glancing angle X-ray diffraction. The nickel silicide thin films were formed by vacuum annealing thin films of nickel (50 nm) deposited on (100) silicon. The cross-sectional samples indicated a final silicide thickness of about 110 nm. This investigation studied and reports on three aspects of the thermally formed thin films: the uniformity in composition of the film using jump ratio maps; the nature of the interface using high resolution imaging; and the crystalline orientation of the thin films using selected-area electron diffraction (SAED). The analysis highlighted uniform composition in the thin films, which was also substantiated by spectroscopy techniques; an interface exhibiting the desired abrupt transition from silicide to silicon; and desired and preferential crystalline orientation corresponding to stoichiometric NiSi, supported by glancing angle X-ray diffraction results.

Effect of interface structure regulation caused by variation of imidization rate on conduction current characteristics of PI/nano-Al2O3 three-layer composite films

NASA Astrophysics Data System (ADS)

Ma, Xinyu; Liu, Lizhu; Zhang, Xiaorui; He, Hongju

2018-06-01

A series of sandwich structure PI films were prepared by different imidization process, with pure PI film as the interlayer and PI/Al2O3 composite films as outer layers. The imidization rate of the film with different cured processes was calculated by characterizing by infrared spectrum (FT-IR), and the morphology of interlayer interface with different imidization rates by scanning electron microscope (SEM). When the imidization conditions of the first and second films were 260 °C/120 min, the composite films displayed better interface structure and higher imidization rate (ID) than others. Moreover, results also showed that the conduction current of three-layer composite film steadily improved with increased ID and temperature, and was higher than that of the pure film. At the temperature of 30 °C, the electrical aging threshold at different ID was obtained. When the ID reached the maximum value of 78.9%, the electrical aging threshold reached the maximum 41.69 kV/mm.

Interface layer to tailor the texture and surface morphology of Al-doped ZnO polycrystalline films on glass substrates

NASA Astrophysics Data System (ADS)

Nomoto, Junichi; Inaba, Katsuhiko; Kobayashi, Shintaro; Makino, Hisao; Yamamoto, Tetsuya

2017-06-01

A 10-nm-thick radio frequency magnetron-sputtered aluminum-doped zinc oxide (AZO) showing a texture with a preferential (0001) orientation on amorphous glass substrates was used as an interface layer for tailoring the orientation of 490-nm-thick polycrystalline AZO films subsequently deposited by direct current (DC) magnetron sputtering at a substrate temperature of 200 °C. Wide-angle X-ray diffraction pole figure analysis showed that the resulting 500-nm-thick AZO films showed a texture with a highly preferential c-axis orientation. This showed that DC-magnetron-sputtered AZO films grew along with the orientation matching that of the interface layer, whereas 500-nm-thick AZO films deposited on bare glass substrates by DC magnetron sputtering exhibited a mixed orientation of the c-plane and other planes. The surface morphology was also improved while retaining the lateral grain size by applying the interface layer as revealed by atomic force microscopy.

Unidirectional oxide hetero-interface thin-film diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Youngmin; Lee, Eungkyu; Lee, Jinwon

2015-10-05

The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing amore » high feasibility for practical applications.« less

Heterojunction solar cell with 6% efficiency based on an n-type aluminum-gallium-oxide thin film and p-type sodium-doped Cu2O sheet

NASA Astrophysics Data System (ADS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2015-02-01

In this paper, we describe efforts to enhance the efficiency of Cu2O-based heterojunction solar cells fabricated with an aluminum-gallium-oxide (Al-Ga-O) thin film as the n-type layer and a p-type sodium (Na)-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing copper sheets. The optimal Al content [X; Al/(Ga + Al) atomic ratio] of an AlX-Ga1-X-O thin-film n-type layer was found to be approximately 2.5 at. %. The optimized resistivity was approximately 15 Ω cm for n-type AlX-Ga1-X-O/p-type Cu2O:Na heterojunction solar cells. A MgF2/AZO/Al0.025-Ga0.975-O/Cu2O:Na heterojunction solar cell with 6.1% efficiency was fabricated using a 60-nm-thick n-type oxide thin-film layer and a 0.2-mm-thick Cu2O:Na sheet with the optimized resistivity.

Understanding the conductive channel evolution in Na:WO3-x-based planar devices

NASA Astrophysics Data System (ADS)

Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

2015-03-01

An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07545e

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates.

PubMed

Foster, Rami N; Keefe, Andrew J; Jiang, Shaoyi; Castner, David G

2013-11-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone.

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates

PubMed Central

Foster, Rami N.; Keefe, Andrew J.; Jiang, Shaoyi; Castner, David G.

2013-01-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone. PMID:24482558

ZrO2 film interfaces with Si and SiO2

NASA Astrophysics Data System (ADS)

Lopez, C. M.; Suvorova, N. A.; Irene, E. A.; Suvorova, A. A.; Saunders, M.

2005-08-01

The interface formed by the thermal oxidation of sputter-deposited Zr metal onto Si(100)- and SiO2-coated Si(100) wafers was studied in situ and in real time using spectroscopic ellipsometry (SE) in the 1.5-4.5 photon energy range and mass spectrometry of recoiled ions (MSRI). SE yielded optical properties for the film and interface and MSRI yielded film and interface composition. An optical model was developed and verified using transmission electron microscopy. Interfacial reaction of the ZrO2 was observed for both substrates, with more interaction for Si substrates. Equivalent oxide thicknesses and interface trap levels were determined on capacitors with lower trap levels found on samples with a thicker SiO2 underlayer. In addition to the optical properties for the intermixed interface layer, the optical properties for Zr metal and unreacted ZrO2 are also reported.

Effect of cholesterol on electrostatics in lipid-protein films of a pulmonary surfactant.

PubMed

Finot, Eric; Leonenko, Yuri; Moores, Brad; Eng, Lukas; Amrein, Matthias; Leonenko, Zoya

2010-02-02

We report the changes in the electrical properties of the lipid-protein film of pulmonary surfactant produced by excess cholesterol. Pulmonary surfactant (PS) is a complex lipid-protein mixture that forms a molecular film at the interface of the lung's epithelia. The defined molecular arrangement of the lipids and proteins of the surfactant film gives rise to the locally highly variable electrical surface potential of the interface, which becomes considerably altered in the presence of cholesterol. With frequency modulation Kelvin probe force microscopy (FM-KPFM) and force measurements, complemented by theoretical analysis, we showed that excess cholesterol significantly changes the electric field around a PS film because of the presence of nanometer-sized electrostatic domains and affects the electrostatic interaction of an AFM probe with a PS film. These changes in the local electrical field would greatly alter the interaction of the surfactant film with charged species and would immediately impact the manner in which inhaled (often charged) airborne nanoparticles and fibers might interact with the lung interface.

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO3/SrTiO3 Heterostructure.

PubMed

Nazir, Safdar; Cheng, Jianli; Yang, Kesong

2016-01-13

We studied strain-induced polarization and resulting conductivity in the nonpolar/nonpolar CaZrO3/SrTiO3 (CZO/STO) heterostructure (HS) system by means of first-principles electronic structure calculations. By modeling four types of CZO/STO HS-based slab systems, i.e., TiO2/CaO and SrO/ZrO2 interface models with CaO and ZrO2 surface terminations in each model separately, we found that the lattice-mismatch-induced compressive strain leads to a strong polarization in the CZO film and that as the CZO film thickness increases there exists an insulator-to-metal transition. The polarization direction and critical thickness of the CZO film for forming interfacial metallic states depend on the surface termination of CZO film in both types of interface models. In the TiO2/CaO and SrO/ZrO2 interface models with CaO surface termination, the strong polarization drives the charge transfer from the CZO film to the first few TiO2 layers in the STO substrate, leading to the formation of two-dimensional electron gas (2DEG) at the interface. In the HS models with ZrO2 surface termination, two polarization domains with opposite directions are in the CZO film, which results in the charge transfer from the middle CZO layer to the interface and surface, respectively, leading to the coexistence of the 2DEG on the interface and the two-dimensional hole gas (2DHG) at the middle CZO layer. These findings open a new avenue to achieve 2DEG (2DHG) in perovskite-based HS systems via polarization discontinuity.

Thermotropic phase transition in an adsorbed melissic acid film at the n-hexane-water interface

NASA Astrophysics Data System (ADS)

Tikhonov, A. M.

2017-06-01

A reversible thermotropic phase transition in an adsorption melissic acid film at the interface between n-hexane and an aqueous solution of potassium hydroxide (pH ≈ 10) is investigated by X-ray reflectometry and diffuse scattering using synchrotron radiation. The experimental data indicate that the interface "freezing" transition is accompanied not only by the crystallization of the Gibbs monolayer but also by the formation of a planar smectic structure in the 300-Å-thick adsorption film; this structure is formed by 50-Å-thick layers.

Real-time observations of interface formation for barium strontium titanate films on silicon

NASA Astrophysics Data System (ADS)

Mueller, A. H.; Suvorova, N. A.; Irene, E. A.; Auciello, O.; Schultz, J. A.

2002-05-01

Ba.5Sr.5TiO3 (BST) film growth by ion sputtering on bare and thermally oxidized silicon was observed in real time using in-situ spectroscopic ellipsometry and time of flight ion scattering and recoil spectrometry techniques. At the outset of BST film deposition on silicon, an approximately 30 Å film with intermediate static dielectric constant (K˜12) and refractive index (n˜2.6 at photon energies of 1.5-3.25 eV) interface layer formed on bare silicon. The interface layer growth rate was greatly reduced on an oxidized silicon substrate. The results have profound implications on the static dielectric constant of BST.

Metal-Insulator Transitions in Epitaxial LaVO(3) and LaTiO(3) Films

DTIC Science & Technology

2012-08-01

epitaxial films of LaVO3 and LaTiO3 can exhibit metallicity though their bulk counterparts are Mott insulators. When LaTiO3 films are compressively...secondarily to interface electronic reconstruction at the LaTiO3 /SrTiO3 interface. However, when LaVO3 films are compressively strained on SrTiO3...ABSTRACT We have demonstrated that epitaxial films of LaVO3 and LaTiO3 can exhibit metallicity though their bulk counterparts are Mott insulators. When

Silicon content design of CrSiN films for good anti-corrosion and anti-wear performances in NaOH solution

NASA Astrophysics Data System (ADS)

Wang, Haixin; Ye, Yuwei; Wang, Chunting; Zhang, Guangan; Liu, Wei

2018-06-01

The CrSiN films with different silicon contents were fabricated by medium frequency magnetron sputtering. The 304L stainless steel and Si (1 0 0) wafer were used for substrate specimens. Film plasticity, corrosion and tribological behaviors in 0.1 M NaOH solution were systematically investigated. Results show that the plasticity of CrN film could be improved by the addition of silicon. During the corrosion test, with the increase of silicon content, the corrosion current density exhibited a descending trend and impedance presented a rising trend. The COF and wear rate of as-prepared CrSiN film initially decreased and then increased as the silicon content increased. The CrSiN film with 12.7 at.% Si exhibited the lowest COF of 0.04 and a wear rate of 6.746  ×  10‑8 mm3 Nm‑1 in 0.1 M NaOH solution.

On the temperature dependence of Na migration in thin SiO 2 films during ToF-SIMS O 2+ depth profiling

NASA Astrophysics Data System (ADS)

Krivec, Stefan; Detzel, Thomas; Buchmayr, Michael; Hutter, Herbert

2010-10-01

The detection of Na in insulating samples by means of time of flight-secondary ion mass spectrometry (ToF-SIMS) depth profiling has always been a challenge. In particular the use of O 2+ as sputter species causes a severe artifact in the Na depth distribution due to Na migration under the influence of an internal electrical filed. In this paper we address the influence of the sample temperature on this artifact. It is shown that the transport of Na is a dynamic process in concordance with the proceeding sputter front. Low temperatures mitigated the migration process by reducing the Na mobility in the target. In the course of this work two sample types have been investigated: (i) A Na doped PMMA layer, deposited on a thin SiO 2 film. Here, the incorporation behavior of Na into SiO 2 during depth profiling is demonstrated. (ii) Na implanted into a thin SiO 2 film. By this sample type the migration behavior could be examined when defects, originating from the implantation process, are present in the SiO 2 target. In addition, we propose an approach for the evaluation of an implanted Na profile, which is unaffected by the migration process.

Nanocube-based hematite photoanode produced in the presence of Na2HPO4 for efficient solar water splitting

NASA Astrophysics Data System (ADS)

Liu, Kan; Wang, Hongyan; Wu, Quanping; Zhao, Jun; Sun, Zhe; Xue, Song

2015-06-01

A thin film of α-Fe2O3 on FTO substrate has been synthesized from hydrothermal process in an aqueous solution of FeCl3 and Na2HPO4. A nanocube structure of α-Fe2O3 is observed within the formed hematite films and coated with phosphate ions on the surface. For comparison, another phosphate modified hematite film has been prepared by soaking the bare hematite film in Na2HPO4 solution. A negative electrostatic field can be built up on the surface of both phosphate modified hematite which will promote charge separation and extraction of photoexcited holes to the electrode surface. It is found that different types of phosphate complex exist in the hematite films, which has been determined by the isoelectric point (IEP) of the hematite films, and consequently influences the formation and strength of the electrostatic field. The effects of phosphate ions on the morphology, surface characteristics and the photoelectrochemical properties of the hematite thin films are investigated and the mechanism is proposed.

Scanning force microscopy at the air-water interface of an air bubble coated with pulmonary surfactant.

PubMed Central

Knebel, D; Sieber, M; Reichelt, R; Galla, H-J; Amrein, M

2002-01-01

To study the structure-function relationship of pulmonary surfactant under conditions close to nature, molecular films of a model system consisting of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol, and surfactant-associated protein C were prepared at the air-water interface of air bubbles about the size of human alveoli (diameter of 100 microm). The high mechanical stability as well as the absence of substantial film flow, inherent to small air bubbles, allowed for scanning force microscopy (SFM) directly at the air-water interface. The SFM topographical structure was correlated to the local distribution of fluorescent-labeled dipalmitoylphosphatidylcholine, as revealed from fluorescence light microscopy of the same bubbles. Although SFM has proven before to be exceptionally well suited to probe the structure of molecular films of pulmonary surfactant, the films so far had to be transferred onto a solid support from the air-water interface of a film balance, where they had been formed. This made them prone to artifacts imposed by the transfer. Moreover, the supported monolayers disallowed the direct observation of the structural dynamics associated with expansion and compression of the films as upon breathing. The current findings are compared in this respect to our earlier findings from films, transferred onto a solid support. PMID:11751334

Enhanced Performance in Al-Doped ZnO Based Transparent Flexible Transparent Thin-Film Transistors Due to Oxygen Vacancy in ZnO Film with Zn-Al-O Interfaces Fabricated by Atomic Layer Deposition.

PubMed

Li, Yang; Yao, Rui; Wang, Huanhuan; Wu, Xiaoming; Wu, Jinzhu; Wu, Xiaohong; Qin, Wei

2017-04-05

Highly conductive and optical transparent Al-doped ZnO (AZO) thin film composed of ZnO with a Zn-Al-O interface was fabricated by thermal atomic layer deposition (ALD) method. The as-prepared AZO thin film exhibits excellent electrical and optical properties with high stability and compatibility with temperature-sensitive flexible photoelectronic devices; film resistivity is as low as 5.7 × 10 -4 Ω·cm, the carrier concentration is high up to 2.2 × 10 21 cm -3 . optical transparency is greater than 80% in a visible range, and the growth temperature is below 150 °C on the PEN substrate. Compared with the conventional AZO film containing by a ZnO-Al 2 O 3 interface, we propose that the underlying mechanism of the enhanced electrical conductivity for the current AZO thin film is attributed to the oxygen vacancies deficiency derived from the free competitive growth mode of Zn-O and Al-O bonds in the Zn-Al-O interface. The flexible transparent transistor based on this AZO electrode exhibits a favorable threshold voltage and I on /I off ratio, showing promising for use in high-resolution, fully transparent, and flexible display applications.

Effect of internal flow and evaporation on hydrogel assembly process at droplet interface

NASA Astrophysics Data System (ADS)

Kang, Giho; Seong, Baekhoon; Gim, Yeonghyeon; Ko, Han Seo; Byun, Doyoung

2017-11-01

Recently, controlling the behavior of nanoparticles inside liquid droplet has been widely studied. There have been many reports about the mechanism of the nanoparticles assembly and fabrication of a thin film on a substrate. However, the assembly mechanism at a liquid-air interface has not been clearly understood to form polymer chains into films. Herein, we investigated the role of internal flow on the thin film assembly process at the interface of the hydrogel droplet. The internal fluid flow during the formation of the hydrogel film was visualized systematically using micro-PIV (Particle image velocimetry) technique at various temperatures. We show that the buoyancy effect and convection flow induced by heat can affect the film morphology and its mechanical characteristics. Due to the accelerated fluid flow inside the droplet and evaporation flux, densely assembled hydrogel film was able to be formed. Film strength was increased 24% with temperature increase from 40 to 80 degrees Celsius. We expect our investigations could be applied to many applications such as self-assembly of planar structures at the interface in coating and printing process. The support from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2015R1A2A1A05001829) is acknowledged.

The role of symmetry-breaking-induced interface anisotropy in [Fe/Pt]{sub n} multilayer films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhenghua; Center for Geo-environment Science, Faculty of Engineering and Resource Science, Akita University, Tegatagakuen-machi 1-1, Akita 010-8502; Xie Hailong

2011-04-01

The FePt films were deposited with [Fe/Pt]{sub n} multilayer structure on preheated Corning 1737F glass substrate using pure Fe and Pt target in a CMS-18 sputtering system. The dependence of FePt's texture and magnetic properties on the multilayer structure was investigated. The XRD patterns indicate that (111) texture is dominant for all [Fe/Pt]{sub n} (n = 8, 16, 20, 32) multilayer films. However, the measured M-H loops show that the perpendicular anisotropy is greatly enhanced in samples with n = 16, 20, and 32. The origin of the increased perpendicular anisotropy of [Fe/Pt]{sub n} multilayer films is related to themore » contributions of the interfaces, which will be analyzed using the micromagnetic models, with careful discussions of the crystalline and interface anisotropies. Finally, it is confirmed that the Fe/Pt interfaces favor the perpendicular orientation in the multilayer structure.« less

Molecular dynamics simulations of ferroelectric domain formation by oxygen vacancy

NASA Astrophysics Data System (ADS)

Zhu, Lin; You, Jeong Ho; Chen, Jinghong; Yeo, Changdong

2018-05-01

An oxygen vacancy, known to be detrimental to ferroelectric properties, has been investigated numerically for the potential uses to control ferroelectric domains in films using molecular dynamics simulations based on the first-principles effective Hamiltonian. As an electron donor, an oxygen vacancy generates inhomogeneous electrostatic and displacement fields which impose preferred polarization directions near the oxygen vacancy. When the oxygen vacancies are placed at the top and bottom interfaces, the out-of-plane polarizations are locally developed near the interfaces in the directions away from the interfaces. These polarizations from the interfaces are in opposite directions so that the overall out-of-plane polarization becomes significantly reduced. In the middle of the films, the in-plane domains are formed with containing 90° a 1/a 2 domain walls and the films are polarized along the [1 1 0] direction even when no electric field is applied. With oxygen vacancies placed at the top interface only, the films exhibit asymmetric hysteresis loops, confirming that the oxygen vacancies are one of the possible sources of ferroelectric imprint. It has been qualitatively demonstrated that the domain structures in the imprint films can be turned on and off by controlling an external field along the thickness direction. This study shows qualitatively that the oxygen vacancies can be utilized for tuning ferroelectric domain structures in films.

Morphology of the D/A interface in vapor deposited bilayer organic photovoltaics

NASA Astrophysics Data System (ADS)

Erwin, Patrick; Dimitriou, Michael; Thompson, Mark E.

2017-08-01

A series of bilayer films were prepared by vacuum deposition onto Silicon substrates. These films consisted of either Si/SiO2/donor/C60 or Si/SiO2/C60/donor, where the organic films were in the 20-40 nm thick range and the donors were 7,7-difluoro-14-phenyl-7H-6l4,7l4-[1,3,2]diazaborinino[4,3-a:6,1-a']diisoindole (bDIP), copper phthalocyanine (CuPC), 3,6,11,14-tetraphenyldiindeno[1,2,3-cd:1',2',3'-lm]perylene (DBP) and 2-(4-(diphenylamino)-2,6- dihydroxyphenyl)-4-(4-(diphenyliminio)-2,6-dihydroxycyclohexa-2,5-dien-1-ylidene)-3-oxocyclobut-1-en-1-olate (DPSQ). The donors chosen here have been reported to give good power efficiencies when incorporated into bilayer photovoltaic cells with a C60 acceptor. These bilayer films were examined by neutron reflectometry to characterize the interface between the donor and C60. In the SiO2/donor/C60 films, DPSQ, CuPC, and DBP show a discrete interface with C60 while bDIP shows substantial spontaneous mixing at the interface, consistent with a donor/(donor + C60)/C60 structure, where the mixed layer is 14 nm.. In the SiO2/C60/donor films, all four donors show negligible mixing at the D/A interface consistent with a discrete D/A junction.

Dielectric and ferroelectric properties of highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 thin films grown on LaNiO 3/γ-Al 2O 3/Si substrates by chemical solution deposition

NASA Astrophysics Data System (ADS)

Guo, Yiping; Akai, Daisuke; Sawada, Kazauki; Ishida, Makoto

2008-07-01

A (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 chemical solution was prepared by using barium acetate, nitrate of sodium, nitrate of bismuth, and Ti-isopropoxide as raw materials. A white precipitation appeared during the preparation was analyzed to be Ba(NO 3) 2. We found that ethanolamine is a very effective coordinating ligand of Ba 2+. A transparent and stable (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 precursor chemical solution has been achieved by using ethanolamine as a ligand of Ba 2+. (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were grown on LaNiO 3/γ-Al 2O 3/Si substrates. Highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were obtained in this work due to lattice match growth. The dielectric, ferroelectric and insulative characteristics against applied field were studied. The conduction current shows an Ohmic conduction behavior at lower voltages and space-charge-limited behavior at higher voltages, respectively. These results indicate that, the (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 film is a promising lead-free ferroelectric film.

Direct observation of twin deformation in YBa2Cu3O7-x thin films by in situ nanoindentation in TEM

NASA Astrophysics Data System (ADS)

Lee, Joon Hwan; Zhang, Xinghang; Wang, Haiyan

2011-04-01

The deformation behaviors of YBa2Cu3O7-x (YBCO) thin films with twinning structures were studied via in situ nanoindentation experiments in a transmission electron microscope. The YBCO films were grown on SrTiO3 (001) substrates by pulsed laser deposition. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of the YBCO films from the directions perpendicular and parallel to the twin interfaces. The hardness measured perpendicular to the twin interfaces is ˜50% and 40% higher than that measured parallel to the twin interfaces ex situ and in situ, respectively. Detailed in situ movie analysis reveals that the twin structures play an important role in deformation and strengthening mechanisms in YBCO thin films.

Coherency strain and its effect on ionic conductivity and diffusion in solid electrolytes--an improved model for nanocrystalline thin films and a review of experimental data.

PubMed

Korte, C; Keppner, J; Peters, A; Schichtel, N; Aydin, H; Janek, J

2014-11-28

A phenomenological and analytical model for the influence of strain effects on atomic transport in columnar thin films is presented. A model system consisting of two types of crystalline thin films with coherent interfaces is assumed. Biaxial mechanical strain ε0 is caused by lattice misfit of the two phases. The conjoined films consist of columnar crystallites with a small diameter l. Strain relaxation by local elastic deformation, parallel to the hetero-interface, is possible along the columnar grain boundaries. The spatial extent δ0 of the strained hetero-interface regions can be calculated, assuming an exponential decay of the deformation-forces. The effect of the strain field on the local ionic transport in a thin film is then calculated by using the thermodynamic relation between (isostatic) pressure and free activation enthalpy ΔG(#). An expression describing the total ionic transport relative to bulk transport of a thin film or a multilayer as a function of the layer thickness is obtained as an integral average over strained and unstrained regions. The expression depends only on known material constants such as Young modulus Y, Poisson ratio ν and activation volume ΔV(#), which can be combined as dimensionless parameters. The model is successfully used to describe own experimental data from conductivity and diffusion studies. In the second part of the paper a comprehensive literature overview of experimental studies on (fast) ion transport in thin films and multilayers along solid-solid hetero-interfaces is presented. By comparing and reviewing the data the observed interface effects can be classified into three groups: (i) transport along interfaces between extrinsic ionic conductors (and insulator), (ii) transport along an open surface of an extrinsic ionic conductor and (iii) transport along interfaces between intrinsic ionic conductors. The observed effects in these groups differ by about five orders of magnitude in a very consistent way. The modified interface transport in group (i) is most probably caused by strain effects, misfit dislocations or disordered transition regions.

Rupture of vertical soap films

NASA Astrophysics Data System (ADS)

Rio, Emmanuelle

2014-11-01

Soap films are ephemeral and fragile objects. They tend to thin under gravity, which gives rise to the fascinating variations of colors at their interfaces but leads systematically to rupture. Even a child can create, manipulate and admire soap films and bubbles. Nevertheless, the reason why it suddenly bursts remains a mystery although the soap chosen to stabilize the film as well as the humidity of the air seem very important. One difficulty to study the rupture of vertical soap films is to control the initial solution. To avoid this problem we choose to study the rupture during the generation of the film at a controlled velocity. We have built an experiment, in which we measure the maximum length of the film together with its lifetime. The generation of the film is due to the presence of a gradient of surface concentration of surfactants at the liquid/air interface. This leads to a Marangoni force directed toward the top of the film. The film is expected to burst only when its weight is not balanced anymore by this force. We will show that this leads to the surprising result that the thicker films have shorter lifetimes than the thinner ones. It is thus the ability of the interface to sustain a surface concentration gradient of surfactants which controls its stability.

Conduction mechanism change with transport oxide layer thickness in oxide hetero-interface diode

NASA Astrophysics Data System (ADS)

Nam, Bu-il; Park, Jong Seo; Lim, Keon-Hee; Ahn, Yong-keon; Lee, Jinwon; Park, Jun-woo; Cho, Nam-Kwang; Lee, Donggun; Lee, Han-Bo-Ram; Kim, Youn Sang

2017-07-01

An effective and facile strategy is proposed to demonstrate an engineered oxide hetero-interface of a thin film diode with a high current density and low operating voltage. The electrical characteristics of an oxide hetero-interface thin film diode are governed by two theoretical models: the space charge-limited current model and the Fowler-Nordheim (F-N) tunneling model. Interestingly, the dominant mechanism strongly depends on the insulator thickness, and the mechanism change occurs at a critical thickness. This paper shows that conduction mechanisms of oxide hetero-interface thin film diodes depend on thicknesses of transport oxide layers and that current densities of these can be exponentially increased through quantum tunneling in the diodes with the thicknesses less than 10 nm. These oxide hetero-interface diodes have great potential for low-powered transparent nanoscale applications.

Capillary bending of a thin polymer film floating on a liquid bath

NASA Astrophysics Data System (ADS)

Twohig, Timothy; Croll, Andrew B.

Thin elastic films and shells are very important in schemes for the encapsulation and protection of fluids from their environment. Capillary origami is a particularly poignant example of how useful fluid/film structures can be formed. The interactions of fluids on thin-films which themselves lie on another surface (fluid or low friction solid) need to be studied if the differences from fluid-fluid and fluid-solid film interfaces are to be fully appreciated. In this experiment, we examine the triple line that occurs when a fluid is resting on a thin polymer film which is itself floating on a second fluid. The top fluid has a high-energy air/fluid interface which can be minimized by deforming the film in a manner that reduces the total air/fluid interface. We create a one-dimensional experiment in order to isolate the basic physics that occurs as the tension of the top fluid pulls on the thin film. Notably, the 1D geometry removes all the complexity incurred by thin films in biaxial stress states (such as wrinkling, folding and crumpling) from the problem. AFOSR under the Young Investigator Program (FA9550-15-1-0168).

Structural, electronic and chemical properties of metal/oxide and oxide/oxide interfaces and thin film structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lad, Robert J.

1999-12-14

This project focused on three different aspects of oxide thin film systems: (1) Model metal/oxide and oxide/oxide interface studies were carried out by depositing ultra-thin metal (Al, K, Mg) and oxide (MgO, AlO{sub x}) films on TiO{sub 2}, NiO and {alpha}-Al{sub 2}O{sub 3} single crystal oxide substrates. (2) Electron cyclotron resonance (ECR) oxygen plasma deposition was used to fabricate AlO{sub 3} and ZrO{sub 2} films on sapphire substrates, and film growth mechanisms and structural characteristics were investigated. (3) The friction and wear characteristics of ZrO{sub 2} films on sapphire substrates in unlubricated sliding contact were studied and correlated with filmmore » microstructure. In these studies, thin film and interfacial regions were characterized using diffraction (RHEED, LEED, XRD), electron spectroscopies (XPS, UPS, AES), microscopy (AFM) and tribology instruments (pin-on-disk, friction microprobe, and scratch tester). By precise control of thin film microstructure, an increased understanding of the structural and chemical stability of interface regions and tribological performance of ultra-thin oxide films was achieved in these important ceramic systems.« less

Modeling of single film bubble and numerical study of the plateau structure in foam system

NASA Astrophysics Data System (ADS)

Sun, Zhong-guo; Ni, Ni; Sun, Yi-jie; Xi, Guang

2018-02-01

The single-film bubble has a special geometry with a certain amount of gas shrouded by a thin layer of liquid film under the surface tension force both on the inside and outside surfaces of the bubble. Based on the mesh-less moving particle semi-implicit (MPS) method, a single-film double-gas-liquid-interface surface tension (SDST) model is established for the single-film bubble, which characteristically has totally two gas-liquid interfaces on both sides of the film. Within this framework, the conventional surface free energy surface tension model is improved by using a higher order potential energy equation between particles, and the modification results in higher accuracy and better symmetry properties. The complex interface movement in the oscillation process of the single-film bubble is numerically captured, as well as typical flow phenomena and deformation characteristics of the liquid film. In addition, the basic behaviors of the coalescence and connection process between two and even three single-film bubbles are studied, and the cases with bubbles of different sizes are also included. Furthermore, the classic plateau structure in the foam system is reproduced and numerically proved to be in the steady state for multi-bubble connections.

Rice Starch Particle Interactions at Air/Aqueous Interfaces—Effect of Particle Hydrophobicity and Solution Ionic Strength

PubMed Central

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-01-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e., the natural particle found inside the plant, at air/aqueous interfaces, and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film. PMID:29868551

Rice starch particle interactions at air/aqueous interfaces– effect of particle hydrophobicity and solution ionic strength

NASA Astrophysics Data System (ADS)

McNamee, Cathy E.; Sato, Yu; Wiege, Berthold; Furikado, Ippei; Marefati, Ali; Nylander, Tommy; Kappl, Michael; Rayner, Marilyn

2018-05-01

Starch particles modified by esterification with dicarboxylic acids to give octenyl succinic anhydride (OSA) starch is an approved food additive that can be used to stabilize oil in water emulsions used in foods and drinks. However, the effects of the OSA modification of the starch particle on the interfacial interactions are not fully understood. Here, we directly measured the packing of films of rice starch granules, i.e. the natural particle found inside the plant, at air/aqueous interfaces and the interaction forces in that system as a function of the particle hydrophobicity and ionic strength, in order to gain insight on how starch particles can stabilize emulsions. This was achieved by using a combined Langmuir trough and optical microscope system, and the Monolayer Interaction Particle Apparatus. Native rice starch particles were seen to form large aggregates at air/water interfaces, causing films with large voids to be formed at the interface. The OSA modification of the rice starches particles decreased this aggregation. Increasing the degree of modification improved the particle packing within the film of particles at the air/water interface, due to the introduction of inter-particle electrostatic interactions within the film. The introduction of salt to the water phase caused the particles to aggregate and form holes within the film, due to the screening of the charged groups on the starch particles by the salt. The presence of these holes in the film decreased the stiffness of the films. The effect of the OSA modification was concluded to decrease the aggregation of the particles at an air/water interface. The presence of salts, however, caused the particles to aggregate, thereby reducing the strength of the interfacial film.

Effect of interfacial interactions on the thermal conductivity and interfacial thermal conductance in tungsten–graphene layered structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jagannadham, K., E-mail: jag-kasichainula@ncsu.edu

2014-09-01

Graphene film was deposited by microwave plasma assisted deposition on polished oxygen free high conductivity copper foils. Tungsten–graphene layered film was formed by deposition of tungsten film by magnetron sputtering on the graphene covered copper foils. Tungsten film was also deposited directly on copper foil without graphene as the intermediate film. The tungsten–graphene–copper samples were heated at different temperatures up to 900 °C in argon atmosphere to form an interfacial tungsten carbide film. Tungsten film deposited on thicker graphene platelets dispersed on silicon wafer was also heated at 900 °C to identify the formation of tungsten carbide film by reaction of tungstenmore » with graphene platelets. The films were characterized by scanning electron microscopy, Raman spectroscopy, and x-ray diffraction. It was found that tungsten carbide film formed at the interface upon heating only above 650 °C. Transient thermoreflectance signal from the tungsten film surface on the samples was collected and modeled using one-dimensional heat equation. The experimental and modeled results showed that the presence of graphene at the interface reduced the cross-plane effective thermal conductivity and the interfacial thermal conductance of the layer structure. Heating at 650 and 900 °C in argon further reduced the cross-plane thermal conductivity and interface thermal conductance as a result of formation nanocrystalline tungsten carbide at the interface leading to separation and formation of voids. The present results emphasize that interfacial interactions between graphene and carbide forming bcc and hcp elements will reduce the cross-plane effective thermal conductivity in composites.« less

Tracer Film Growth Study of the Corrosion of Magnesium Alloys AZ31B and ZE10A in 0.01% NaCl Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, M. P.; Fayek, M.; Leonard, D. N.

We conducted a sequential isotopic tracer study of corrosion film growth for Mg-3Al-1Zn-0.25Mn (AZ31B) and Mg-1.2Zn-0.25Zr-<0.5Nd (ZE10A) by 4 h immersion in H 2 18O or D 2 16O, followed by a 20 h immersion in a 0.01 wt% NaCl H 2 18O or D 2 16O solution. Sputter depth profiles were obtained for 16O, 18O, H, and D using secondary ion mass spectrometry (SIMS). When compared to the previous tracer study for these alloys in salt-free water, the addition of 0.01 wt% NaCl resulted in a transition from oxygen inward-dominated film growth to a component of mixed inward/outward filmmore » growth for both alloys. The hydrogen tracer behavior remained inward growing for AZ31B, and short-circuit, inward growing for ZE10A, in both pure water and in 0.01 wt% NaCl solution, with extensive penetration of D beyond the film and into the underlying alloy also observed for ZE10A. Our analysis of the films by X-ray photoelectron spectroscopy (XPS) and cross-section scanning transmission electron microscopy (STEM) indicated intermixed Mg(OH) 2 and MgO, with the relative fraction of Mg(OH) 2 peaking near the center of the film. These findings suggest a decoupled film growth mechanism, with initial formation of oxide followed by NaCl-accelerated conversion to hydroxide, likely by both solid-state and dissolution-precipitation processes.« less

Tracer Film Growth Study of the Corrosion of Magnesium Alloys AZ31B and ZE10A in 0.01% NaCl Solution

DOE PAGES

Brady, M. P.; Fayek, M.; Leonard, D. N.; ...

2017-05-25

We conducted a sequential isotopic tracer study of corrosion film growth for Mg-3Al-1Zn-0.25Mn (AZ31B) and Mg-1.2Zn-0.25Zr-<0.5Nd (ZE10A) by 4 h immersion in H 2 18O or D 2 16O, followed by a 20 h immersion in a 0.01 wt% NaCl H 2 18O or D 2 16O solution. Sputter depth profiles were obtained for 16O, 18O, H, and D using secondary ion mass spectrometry (SIMS). When compared to the previous tracer study for these alloys in salt-free water, the addition of 0.01 wt% NaCl resulted in a transition from oxygen inward-dominated film growth to a component of mixed inward/outward filmmore » growth for both alloys. The hydrogen tracer behavior remained inward growing for AZ31B, and short-circuit, inward growing for ZE10A, in both pure water and in 0.01 wt% NaCl solution, with extensive penetration of D beyond the film and into the underlying alloy also observed for ZE10A. Our analysis of the films by X-ray photoelectron spectroscopy (XPS) and cross-section scanning transmission electron microscopy (STEM) indicated intermixed Mg(OH) 2 and MgO, with the relative fraction of Mg(OH) 2 peaking near the center of the film. These findings suggest a decoupled film growth mechanism, with initial formation of oxide followed by NaCl-accelerated conversion to hydroxide, likely by both solid-state and dissolution-precipitation processes.« less

Improvement of laser molecular beam epitaxy grown SrTiO3 thin film properties by temperature gradient modulation growth

NASA Astrophysics Data System (ADS)

Li, Jin Long; Hao, J. H.; Li, Y. R.

2007-09-01

Oxygen diffusion at the SrTiO3/Si interface was analyzed. A method called temperature gradient modulation growth was introduced to control oxygen diffusion at the interface of SrTiO3/Si. Nanoscale multilayers were grown at different temperatures at the initial growing stage of films. Continuous growth of SrTiO3 films was followed to deposit on the grown sacrificial layers. The interface and crystallinity of SrTiO3/Si were investigated by in situ reflection high energy electron diffraction and x-ray diffraction measurements. It has been shown that the modulated multilayers may help suppress the interfacial diffusion, and therefore improve SrTiO3 thin film properties.

A correlation between secondary structure and rheological properties of low-density lipoproteins at air/water interfaces.

PubMed

Khattari, Ziad

2017-09-01

The secondary structure of apolipoprotein B-100 is studied within the bulk phase and at the air/water interface. In these "in viro" experiments, infrared reflection absorption spectroscopy (IRRAS) study was performed at the air/water interface while circular dichroism (CD) was conducted in the bulk phase. In the bulk phase, the conformational structure containing a significant amount of β-structure, whereas varying amount of α-helix, unordered structures, and β-sheet were observed at the air/water interface depending on the low-density lipoprotein (LDL) film interfacial pressure. The present IRRAS results demonstrate the importance of interfacial pressure-induced structural conformations on the apoB-100. A correlation between the secondary structure of the apoB-100 protein and the monomolecular film elasticity at the air/water interface was also established. The orientation of apoB-100 with respect to the LDL film-normal was found to depend on the interfacial pressure exhibited by the monomolecular film. These results may shed light on LDL's pivotal role in the progression of atherosclerotic coronary artery disease as demonstrated previously by clinical trials.

Tuning the Solid Electrolyte Interphase for Selective Li- and Na-Ion Storage in Hard Carbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soto, Fernando A.; Yan, Pengfei; Engelhard, Mark H.

Solid-electrolyte interphase (SEI) films with controllable properties are highly desirable for improving battery performance. In this paper, a combined experimental and theoretical approach is used to study SEI films formed on hard carbon in Li- and Na-ion batteries. It is shown that a stable SEI layer can be designed by precycling an electrode in a desired Li- or Na-based electrolyte, and that ionic transport can be kinetically controlled. Selective Li- and Na-based SEI membranes are produced using Li- or Na-based electrolytes, respectively. The Na-based SEI allows easy transport of Li ions, while the Li-based SEI shuts off Na-ion transport. Na-ionmore » storage can be manipulated by tuning the SEI layer with film-forming electrolyte additives, or by preforming an SEI layer on the electrode surface. The Na specific capacity can be controlled to < 25 mAh g(-1); approximate to 1/10 of the normal capacity (250 mAh g(-1)). Unusual selective/ preferential transport of Li ions is demonstrated by preforming an SEI layer on the electrode surface and corroborated with a mixed electrolyte. This work may provide new guidance for preparing good ion-selective conductors using electrochemical approaches.« less

Interface morphology studies of liquid phase epitaxy grown HgCdTe films by atomic force microscopy

NASA Astrophysics Data System (ADS)

Azoulay, M.; George, M. A.; Burger, A.; Collins, W. E.; Silberman, E.

1994-04-01

In this paper we report an investigation of the morphology of the interfaces of liquid phase epitaxy (LPE) grown HgCdTe thin films on CdTe and CdZnTe substrates by atomic force microscopy (AFM) on freshly cleaved (110) crystallographic planes. An empirical observation which may be linked to lattice mismatch was indicated by an angle between the cleavage steps of the substrate to those of the film. The precipitates with size ranging from 5 nm to 20 nm were found to be most apparent near the interface.

Effects of interfaces on the thermal conductivity in Si/Si0.75Ge0.25 multilayer with varying Au layers

NASA Astrophysics Data System (ADS)

Hu, Yangsen; Wu, Zhenghua; Ye, Fengjie; Hu, Zhiyu

2018-02-01

The manoeuvre of thermal transport property across multilayer films with inserted metal layers through controlling the metal-nonmetal interfaces is of fundamental interest. In this work, amorphous Si/Si0.75Ge0.25 multilayer films inserted with varying Au layers were fabricated by magnetron sputtering. The structure and sharp interface of multilayers films were characterized by low angle x-ray diffraction (LAXRD), grazing incidence small angle x-ray scattering (GISAXS) and scanning electron microscopy (SEM). A differential 3ω method was applied to measure the effective thermal conductivity. The measurements show that thermal conductivity has changed as varying Au layers. Thermal conductivity increased from 0.94 to 1.31 Wm-1K-1 while Si0.75Ge0.25 layer was replaced by different Au layers, which was attributed to the strong electron-phonon coupling and interface thermal resistance in a metal-nonmetal multilayered system. Theoretical calculation combined with experimental results indicate that the thermal conductivity of the multilayer film could be facilely controlled by introducing different number of nanoconstructed metal-nonmetal interfaces, which provide a more insightful understanding of the thermal transport manipulation mechanism of the thin film system with inserting metal layers.

Effect of film multi-scale structure on the water vapor permeability in hydroxypropyl starch (HPS)/Na-MMT nanocomposites.

PubMed

Liu, Siyuan; Cai, Panfu; Li, Xiaoxi; Chen, Ling; Li, Lin; Li, Bing

2016-12-10

To improve the water vapor resistance of starch-based films, Na-MMT (Na-montmorillonite) as nanofillers were fabricated into hydroxypropyl starch and the multi-scale structural changes (including intermolecular interaction, short-range conformation, long-range ordered structure and the aggregated structure of the film) were revealed. The elongation of the water vapor molecule pathway by tortuous path is generally recognized as the main reason for the improvement of water resistance. However this study observed the lowest water vapor permeability (WVP) was at the 3% Na-MMT/hydroxypropyl starch (HPS) ratio instead of 5% even nanofillers were partially exfoliated at both ratio. Except for the "tortuous path" caused by nanofillers, this observation proposed that the short-range conformation of HPS chains, long-range ordered structure and the aggregated structure likely influenced the water barrier property. The relationship between WVP and multi-scale structure of the film was investigated. The results suggested that a good balance of short-range conformationin the amorphous region, long-range ordered structure and the aggregated structure of the film was required for the improvement of water vapor barrier property. Copyright © 2016 Elsevier Ltd. All rights reserved.

(Na{sub x}k{sub 1−x}){sub 2}Ta{sub 4}O{sub 11}(x≈0.93) piezoelectric phase from the transformation of Ta{sub 2}O{sub 5} thin films of monoclinic structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Gallic, M., E-mail: Marie.Le-Gallic@grenoble-inp.fr; Roussel, H.

2013-04-15

A phase of trigonal structure has been reported in previous articles to be piezoelectric with a very high longitudinal d{sub 33} coefficient of several thousand pm/V (J. Solid State Chem. 184 (2011) 2023, 2033). It was observed in Ta{sub 2}O{sub 5} thin films and assumed to be the result of a reversible monoclinic–trigonal phase transition. However, new investigations are reported because the cell parameters of this phase are actually very close to those of the natrotantite mineral Na{sub 2}Ta{sub 4}O{sub 11}. From analyses by X-ray energy dispersive spectroscopy (XEDS), the chemical composition of this trigonal phase corresponds to (Na{sub x}K{submore » 1−x}){sub 2}Ta{sub 4}O{sub 11} with x≈0.93. The origin of sodium, potassium, iron and oxygen atoms is found to be due to a pollution coming from alumina crucibles used for thermal treatments. Knowing both atomic structures Ta{sub 2}O{sub 5} and Na{sub 2}Ta{sub 4}O{sub 11} and their structural relationships, observed by high resolution transmission electron microscopy (HRTEM), the mechanism of the reaction of transformation is re-examined and discussed. This mechanism implies that Ta{sup 5+} vacancies likely exist in monoclinic structures of tantalum oxide and that electrical neutrality could be due to incorporated proton H{sup +} instead of O{sup 2−} vacancies or Ta{sup 5+} interstitials. - Graphical abstract: (a, b) TEM images of interfaces between Ta{sub 2}O{sub 5} monoclinic and (Na{sub 0.93}K{sub 0.07}){sub 2}Ta{sub 4}O{sub 11} trigonal phases where it appears that the ratio of periods for the transformation monoclinic-to-trigonal is 3/2 (c, d) corresponding schema of the reaction of transformation, (a, c) viewed along the zone axes [010]{sub o}∥[1{sup ¯}21{sup ¯}]{sub R} and (b, d) along the zone axes [100]{sub o}∥[101{sup ¯}]{sub R}. Highlights: ► The formation of a piezoelectric phase in Ta{sub 2}O{sub 5} thin films, reported in previous articles, is re-examined. ► Its composition is actually (Na{sub x},K{sub 1}−x){sub 2}Ta{sub 4}O{sub 11} with x=0.93, instead of Ta{sub 2}O{sub 5}. ► Ta{sup 5+} vacancies, compensated by protons within tantalumoxide, are involved in a new analysis of the transformation.« less

Dislocation confinement in the growth of Na flux GaN on metalorganic chemical vapor deposition-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeuchi, S., E-mail: takeuchi@ee.es.osaka-u.ac.jp; Asazu, H.; Nakamura, Y.

2015-12-28

We have demonstrated a GaN growth technique in the Na flux method to confine c-, (a+c)-, and a-type dislocations around the interface between a Na flux GaN crystal and a GaN layer grown by metalorganic chemical vapor deposition (MOCVD) on a (0001) sapphire substrate. Transmission electron microscopy (TEM) clearly revealed detailed interface structures and dislocation behaviors that reduced the density of vertically aligned dislocations threading to the Na flux GaN surface. Submicron-scale voids were formed at the interface above the dislocations with a c component in MOCVD-GaN, while no such voids were formed above the a-type dislocations. The penetration ofmore » the dislocations with a c component into Na flux GaN was, in most cases, effectively blocked by the presence of the voids. Although some dislocations with a c component in the MOCVD-GaN penetrated into the Na flux GaN, their propagation direction changed laterally through the voids. On the other hand, the a-type dislocations propagated laterally and collectively near the interface, when these dislocations in the MOCVD-GaN penetrated into the Na flux GaN. These results indicated that the dislocation propagation behavior was highly sensitive to the type of dislocation, but all types of dislocations were confined to within several micrometers region of the Na flux GaN from the interface. The cause of void formation, the role of voids in controlling the dislocation behavior, and the mechanism of lateral and collective dislocation propagation are discussed on the basis of TEM results.« less

Understanding the conductive channel evolution in Na:WO(3-x)-based planar devices.

PubMed

Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

2015-04-14

An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO(3-x)) films on a soda-lime glass substrate, from which Na(+) diffuses into the WO(3-x) films during the deposition. The entire process of Na(+) migration driven by an alternating electric field is visualized in the Na-doped WO(3-x) films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na(+) mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.

The Preparation and Microstructure of Nanocrystal 3C-SiC/ZrO2 Bilayer Films

PubMed Central

Ye, Chao; Ran, Guang; Zhou, Wei; Qu, Yazhou; Yan, Xin; Cheng, Qijin; Li, Ning

2017-01-01

The nanocrystal 3C-SiC/ZrO2 bilayer films that could be used as the protective coatings of zirconium alloy fuel cladding were prepared on a single-crystal Si substrate. The corresponding nanocrystal 3C-SiC film and nanocrystal ZrO2 film were also dividedly synthesized. The microstructure of nanocrystal films was analyzed by grazing incidence X-ray diffraction (GIXRD) and cross-sectional transmission electron microscopy (TEM). The 3C-SiC film with less than 30 nm crystal size was synthesized by Plasma Enhanced Chemical Vapor Deposition (PECVD) and annealing. The corresponding formation mechanism of some impurities in SiC film was analyzed and discussed. An amorphous Zr layer about 600 nm in width was first deposited by magnetron sputtering and then oxidized to form a nanocrystal ZrO2 layer during the annealing process. The interface characteristics of 3C-SiC/ZrO2 bilayer films prepared by two different processes were obviously different. SiZr and SiO2 compounds were formed at the interface of 3C-SiC/ZrO2 bilayer films. A corrosion test of 3C-SiC/ZrO2 bilayer films was conducted to qualitatively analyze the surface corrosion resistance and the binding force of the interface. PMID:29168782

The study on the electrical resistivity of Cu/V multilayer films subjected to helium (He) ion irradiation

NASA Astrophysics Data System (ADS)

Wang, P. P.; Xu, C.; Fu, E. G.; Du, J. L.; Gao, Y.; Wang, X. J.; Qiu, Y. H.

2018-05-01

Sputtering-deposited Cu/V multilayer films with the individual layer thickness varying from 2.5 nm to 100 nm were irradiated by 1 MeV helium (He) ion at the fluence of 6 ×1016 ions ·cm-2 at room temperature. The resistivity of Cu/V multilayer films after ion irradiation was evaluated as a function of individual layer thickness at 300 K and compared with their resistivity before ion irradiation. The results show that the resistivity change before and after ion irradiation is largely determined by the interface structure, grain boundary and radiation induced defects. A model amended based on the model used in describing the resistivity of as-deposited Cu/V multilayer films was proposed to describe the resistivity of ion irradiated Cu/V multilayer films by considering the point defects induced by ion irradiation, the effect of interface absorption on defects and the effect of interface microstructure in the multilayer films.

LEED and AES characterization of the GaAs(110)-ZnSe interface

NASA Technical Reports Server (NTRS)

Tu, D.-W.; Kahn, A.

1984-01-01

In this paper, a study is conducted of the composition and structure of epitaxial ZnSe films grown by congruent evaporation on GaAs(110) at a rate of 2 A/min. It is found that the films grown on 300 C GaAs are nearly stoichiometric and form an abrupt interface with the substrate. Films grown at higher temperature (T greater than 350-400 C) are Se rich. The crystallinity of films grown at 300 C is good and their surface atomic geometry is identical to that of a ZnSe crystal. The GaAs-ZnSe interface geometry seems to be dominated by the Se-substrate bonds. The adsorption of Se, during the formation of very thin ZnSe films (2-3 A), produces a (1 x 2) LEED pattern and modifications of the LEED I-V profiles, which probably indicate a change in the substrate atomic relaxation.

Viscosity of particle laden films

NASA Astrophysics Data System (ADS)

Timounay, Yousra; Rouyer, Florence

2017-06-01

We perform retraction experiments on soap films where large particles bridge the two interfaces. Local velocities are measured by PIV during the unstationnary regime. The velocity variation in time and space can be described by a continuous fluid model from which effective viscosity (shear and dilatational) of particulate films is measured. The 2D effective viscosity of particulate films η2D increases with particle surface fraction ϕ: at low ϕ, it tends to the interfacial dilatational viscosity of the liquid/air interfaces and it diverges at the critical particle surface fraction ϕc ≃ 0.84. Experimental data agree with classical viscosity laws of hard spheres suspensions adapted to the 2D geometry, assuming viscous dissipation resulting from the squeeze of the liquid/air interfaces between the particles. Finally, we show that the observed viscous dissipation in particulate films has to be considered to describe the edge velocity during a retraction experiment at large particle coverage.

Water-Based Peeling of Thin Hydrophobic Films

NASA Astrophysics Data System (ADS)

Khodaparast, Sepideh; Boulogne, François; Poulard, Christophe; Stone, Howard A.

2017-10-01

Inks of permanent markers and waterproof cosmetics create elastic thin films upon application on a surface. Such adhesive materials are deliberately designed to exhibit water-repellent behavior. Therefore, patterns made up of these inks become resistant to moisture and cannot be cleaned by water after drying. However, we show that sufficiently slow dipping of such elastic films, which are adhered to a substrate, into a bath of pure water allows for complete removal of the hydrophobic coatings. Upon dipping, the air-water interface in the bath forms a contact line on the substrate, which exerts a capillary-induced peeling force at the edge of the hydrophobic thin film. We highlight that this capillary peeling process is more effective at lower velocities of the air-liquid interface and lower viscosities. Capillary peeling not only removes such thin films from the substrate but also transfers them flawlessly onto the air-water interface.

Ion-beam mixed ultra-thin cobalt suicide (CoSi2) films by cobalt sputtering and rapid thermal annealing

NASA Astrophysics Data System (ADS)

Kal, S.; Kasko, I.; Ryssel, H.

1995-10-01

The influence of ion-beam mixing on ultra-thin cobalt silicide (CoSi2) formation was investigated by characterizing the ion-beam mixed and unmixed CoSi2 films. A Ge+ ion-implantation through the Co film prior to silicidation causes an interface mixing of the cobalt film with the silicon substrate and results in improved silicide-to-silicon interface roughness. Rapid thermal annealing was used to form Ge+ ion mixed and unmixed thin CoSi2 layer from 10 nm sputter deposited Co film. The silicide films were characterized by secondary neutral mass spectroscopy, x-ray diffraction, tunneling electron microscopy (TEM), Rutherford backscattering, and sheet resistance measurements. The experi-mental results indicate that the final rapid thermal annealing temperature should not exceed 800°C for thin (<50 nm) CoSi2 preparation. A comparison of the plan-view and cross-section TEM micrographs of the ion-beam mixed and unmixed CoSi2 films reveals that Ge+ ion mixing (45 keV, 1 × 1015 cm-2) produces homogeneous silicide with smooth silicide-to-silicon interface.

Structural, chemical, and magnetic properties of Fe films grown on InAs(100)

NASA Astrophysics Data System (ADS)

Ruppel, L.; Witte, G.; Wöll, Ch.; Last, T.; Fischer, S. F.; Kunze, U.

2002-12-01

The structure of epitaxial Fe films grown on an InAs(100)-c(8×2)/(4×2) surface has been studied in situ by means of low-energy electron diffraction and x-ray photoelectron spectroscopy, while their magnetic properties were characterized ex situ by superconducting quantum interference device magnetometry at temperatures of 5 300 K. Deposition of iron at room temperature or below leads to the formation of a thin iron arsenide layer that floats on the Fe film upon further deposition. Postdeposition annealing causes no significant improvement of the film structure but activates a further arsenic diffusion through the Fe film. Significant exchange-bias effects were found at low temperatures for insufficiently capped and partially oxidized Fe films, and are attributed to noncollinear spin order at the Ag capping layer/Fe interface. For perfect, nonoxidized Fe films, such a noncollinear spin order at the Fe/InAs interface is excluded as no thermomagnetic irreversibilities were found. This indicates that the spin order at the Fe/InAs interface is suitable for spin injection.

Laser-induced vibration of a thin soap film.

PubMed

Emile, Olivier; Emile, Janine

2014-09-21

We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems.

Stability of embossed PEI-(PSS-PDADMAC) 20 multilayer films versus storage time and versus a change in ionic strength

NASA Astrophysics Data System (ADS)

Ladhari, Nadia; Hemmerlé, Joseph; Haikel, Youssef; Voegel, Jean-Claude; Schaaf, Pierre; Ball, Vincent

2008-12-01

The use of microstructured films increased markedly in many areas of science and technology, notably in the design of microfluidic channels and in the design of parallel biosensing arrays. The concept of imprinting polyelectrolyte multilayer films (PEMs) has been introduced recently [C. Gao, B. Wang, J. Feng, J. Shen, Macromolecules 37 (2004) 8836]. These irreversibly imprinted films, obtained by plastic deformation, have to keep their size and shape after contact with fluids having physicochemical properties comparable to those of biological fluids in order to be used as microfluidic channels. We demonstrate herein that PEI-(PSS-PDADMAC) 20 PEMs built-up by the spray deposition from NaCl 1 M solutions and subsequently imprinted with polydimethylsiloxane stamps keep their morphology over time (up to 9 months) when stored in the dry state. In addition the depth of the imprinted channels does not change over this time duration. When the embossed films are immersed in NaCl 0.15 M solutions, mimicking biological fluids, the depth of the imprinted channels also does not significantly change. But, when the imprinted films prepared in the presence of 1 M NaCl are subsequently dipped in a 4 M NaCl solution, partial film loss and subsequent disappearance of the imprinted channels are observed. An explanation for these findings is furnished by means of FTIR spectroscopy in the attenuated total reflection mode (ATR-FTIR). These observations should offer large opportunities for the use of the imprinted multilayer films as microfluidic channels.

Surface Termination Conversion during SrTiO3 Thin Film Growth Revealed by X-ray Photoelectron Spectroscopy

PubMed Central

Baeumer, Christoph; Xu, Chencheng; Gunkel, Felix; Raab, Nicolas; Heinen, Ronja Anika; Koehl, Annemarie; Dittmann, Regina

2015-01-01

Emerging electrical and magnetic properties of oxide interfaces are often dominated by the termination and stoichiometry of substrates and thin films, which depend critically on the growth conditions. Currently, these quantities have to be measured separately with different sophisticated techniques. This report will demonstrate that the analysis of angle dependent X-ray photoelectron intensity ratios provides a unique tool to determine both termination and stoichiometry simultaneously in a straightforward experiment. Fitting the experimental angle dependence with a simple analytical model directly yields both values. The model is calibrated through the determination of the termination of SrTiO3 single crystals after systematic pulsed laser deposition of sub-monolayer thin films of SrO. We then use the model to demonstrate that during homoepitaxial SrTiO3 growth, excess Sr cations are consumed in a self-organized surface termination conversion before cation defects are incorporated into the film. We show that this termination conversion results in insulating properties of interfaces between polar perovskites and SrTiO3 thin films. These insights about oxide thin film growth can be utilized for interface engineering of oxide heterostructures. In particular, they suggest a recipe for obtaining two-dimensional electron gases at thin film interfaces: SrTiO3 should be deposited slightly Ti-rich to conserve the TiO2-termination. PMID:26189436

A comparative study about electronic structures at rubrene/Ag and Ag/rubrene interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, Sumona, E-mail: sumona.net.09@gmail.com; Mukherjee, M.

The contact between the electrode and the organic semiconductor is one of the most crucial factors in determining the organic device performance. The development and production technology of different organic devices require the understanding of different types of metal/organic semiconducting thin film interfaces. Comparisons about the electronic structures at Rubrene/Ag and Ag/Rubrene interfaces have been studied using photoemission spectroscopy. The Ag on rubrene interfaces is found to show more interesting and complex natures than its counterpart. The vacuum level (VL) was shifted about 0.51 eV from push back effect for deposition of 5 Å rubrene onto Ag film whereas themore » electronic features of silver was only suppressed and no energy shift was resulted. While the deposition of 5 Å Ag onto rubrene film leads to the diffusion of the Ag atoms, as a cluster with quantum size effect, inside the film. Angle dependent XPS measurement indicates that diffused metal clusters were present at entire probed depth of the film. Moreover these clusters dope the uppermost surface of the rubrene film which consequences a shift of the electronic states of thick organic film towards higher binding energy. The VL was found to shift about 0.31 eV toward higher binding energy whereas the shift was around 0.21 eV for the electronic states of rubrene layer.« less

Structural and electrical properties of atomic layer deposited Al-doped ZrO2 films and of the interface with TaN electrode

NASA Astrophysics Data System (ADS)

Spiga, S.; Rao, R.; Lamagna, L.; Wiemer, C.; Congedo, G.; Lamperti, A.; Molle, A.; Fanciulli, M.; Palma, F.; Irrera, F.

2012-07-01

Al-doped ZrO2 (Al-ZrO2) films deposited by atomic layer deposition onto silicon substrates and the interface with the TaN metal gate are investigated. In particular, structural properties of as-grown and annealed films in the 6-26 nm thickness range, as well as leakage and capacitive behavior of metal-oxide-semiconductor stacks are characterized. As-deposited Al-ZrO2 films in the mentioned thickness range are amorphous and crystallize in the ZrO2 cubic phase after thermal treatment at 900 °C. Correspondingly, the dielectric constant (k) value increases from 20 ± 1 to 27 ± 2. The Al-ZrO2 layers exhibit uniform composition through the film thickness and are thermally stable on Si, whereas chemical reactions take place at the TaN/Al-ZrO2 interface. A transient capacitance technique is adopted for monitoring charge trapping and flat band instability at short and long time scales. The role of traps nearby the TaN/Al-ZrO2 interface is discussed and compared with other metal/high-k oxide films. Further, analytical modeling of the flat band voltage shift with a power-law dependence on time allows extracting features of bulk traps close to the silicon/oxide interface, which exhibit energy levels in the 1.4-1.9 eV range above the valence band of the Al-ZrO2.

Combinatorial investigation of the effects of sodium on Cu 2ZnSnSe4 polycrystalline thin films

NASA Astrophysics Data System (ADS)

Gibbs, Alex Hilton

Cu2ZnSnSe4 (CZTSe) possess highly suitable optical and electronic properties for use as an absorber layer in thin film solar cells. CZTSe also has potential to achieve terawatt level solar energy production due to its inexpensive and abundant material constituents. Currently, fabricating CZTSe devices with the expected theoretical performance has not been achieved, making the growth and formation of CZTSe an interesting topic of research. In this work, a two-step vacuum fabrication process consisting of RF co-sputtering followed by reactive annealing was explored as a viable technique for synthesizing CZTSe thin films. Furthermore, the enhancement of the fabrication process by the incorporation of sodium during annealing was studied using a combinatorial approach. Film composition was analyzed using electron dispersive spectroscopy. Structure, phase morphology, and formation were determined using scanning electron microscopy, x-ray diffraction, atomic force microscopy and raman spectroscopy. Optical and electronic properties were characterized using UV-Vis and Voc were measurements under a one sun solar simulator. RF co-sputtering CuSe, ZnSe, and SnSe precursors produced films with good thickness uniformity, adhesion and stoichiometry control over 3 x 3 in 2 substrates. Composition measurements showed that the precursor films maintained stability during an annealing process of 580° C for 20 minutes producing near stoichiometric CZTSe. However, grain size was small with an average diameter of 350 nm. The CZTSe film produced by this process exhibited a suitable absorption coefficient of > 104 cm-1 and aband gap near 1.0 eV. The film also produced an XRD pattern consistent with tetragonal CZTSe with no secondary phase formation with the exception of approximately 12.5 nm of interfacial MoSe2 formation at the back contact. The combinatorial investigation of the influence of sodium on CZTSe growth and morphology was achieved using a custom built constant withdraw shutter to evaporate NaF with a 0-60 nm thickness spread on the substrate prior to precursor sputtering. This experiment showed that the incorporation of NaF did enhance grain size; however, there was little correlation with initial NaF composition observed. It is concluded that NaF undergoes high degree of vapor transport and readily distributes nonuniformly throughout the film during the annealing process and also potentially escapes the annealing environment if not properly contained. An experiment on achieving Na incorporation by diffusion from a soda lime glass substrate resulted in a far more uniform enhancement of grain growth. The experiment also revealed that NaF greatly reduced precursor film adhesion to the substrate due to the hygroscopic nature of NaF. X-ray diffraction measurements also showed that the addition of the NaF layer was could potentially suppress the formation of MoSe2.

Effect of nitrogen doping on the structural, optical and electrical properties of indium tin oxide films prepared by magnetron sputtering for gallium nitride light emitting diodes

NASA Astrophysics Data System (ADS)

Tian, Lifei; Cheng, Guoan; Wang, Hougong; Wu, Yulong; Zheng, Ruiting; Ding, Peijun

2017-01-01

The indium tin oxide (ITO) films are prepared by the direct current magnetron sputtering technology with an ITO target in a mixture of argon and nitrogen gas at room temperature. The blue transmittance at 455 nm rises from 63% to 83% after nitrogen doping. The resistivity of the ITO film reduces from 4.6 × 10-3 (undoped film) to 5.7 × 10-4 Ω cm (N-doped film). The X-ray photoelectron spectroscopy data imply that the binding energy of the In3d5/2 peak is declined 0.05 eV after nitrogen doping. The high resolution transmission electron microscope images show that the nitrogen loss density of the GaN/ITO interface with N-doped ITO film is smaller than that of the GaN/ITO interface with undoped ITO film. The forward turn-on voltage of gallium nitride light emitting diode reduces by 0.5 V after nitrogen doping. The fabrication of the N-doped ITO film is conducive to modify the N component of the interface between GaN and ITO layer.

Effects of argon addition on a-CNx film deposition by hot carbon filament chemical vapor deposition

NASA Astrophysics Data System (ADS)

Watanabe, Yoshihisa; Aono, Masami; Yamazaki, Ayumi; Kitazawa, Nobuaki; Nakamura, Yoshikazu

2002-07-01

Using a carbon filament which supplies carbon and heat, amorphous carbon nitride (a-CNx) films were prepared on Si (100) substrates by hot filament chemical vapor deposition. Deposition was performed in a low-pressure atmosphere of pure nitrogen and a gas mixture of nitrogen and argon. Effects of argon additions to the nitrogen atmosphere on the film microstructure and interface composition between the film and substrate were studied by field-emission scanning electron microscopy (FESEM) and x-ray photoelectron spectroscopy (XPS). FESEM observations reveal that the film prepared in a pure nitrogen atmosphere has uniform nucleation and a densely packed columnar pieces structure. The film prepared in the nitrogen and argon gas mixture exhibits preferential nucleation and a tapered structure with macroscopic voids. Depth analyses using XPS reveal that the film prepared in pure nitrogen possesses a broad interface, which includes silicon carbide as well as a-CNx, whereas a sharp interface is discerned in the film prepared in the mixed nitrogen and argon gas. We observed that silicon carbide formation is suppressed by an argon addition to the nitrogen atmosphere during deposition. copyright 2002 American Vacuum Society.

Stoichiometry dependence of potential screening at La ( 1 - δ ) Al ( 1 + δ ) O 3 / SrTiO 3 interfaces

DOE PAGES

Weiland, Conan; Sterbinsky, George E.; Rumaiz, Abdul K.; ...

2015-04-03

Hard x-ray photoelectron spectroscopy (HAXPES) and variable kinetic energy x-ray photoelectron spectroscopy (VKE-XPS) analyses have been performed on ten-unit-cell-thick La (1-δ)Al (1+δ)O₃ films, with La:Al ratios of 1.1, 1.0, and 0.9, deposited on SrTiO₃. Only Al-rich films are known to have a conductive interface. VKE-XPS, coupled with maximum entropy analysis, shows significant differences in the compositional depth profile among the Al-rich, La-rich, and stoichiometric films: significant La enrichment at the interface is observed in the La-rich and stoichiometric films, while the Al-rich film shows little to no intermixing. Additionally, the La-rich and stoichiometric films show a high concentration of Almore » at the surface, which is not observed in the Al-rich film. HAXPES valence band (VB) analysis shows a broadening of the VB for the Al-rich sample relative to the stoichiometric and La-rich samples. This broadening is consistent with an electric field across the Al-rich film. These results are consistent with a defect-driven electronic reconstruction.« less

Asymmetry of radiation damage properties in Al-Ti nanolayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Setyawan, Wahyu; Gerboth, Matthew D.; Yao, Bo

2014-02-01

Molecular dynamics (MD) simulations were employed with empirical potentials to study the effects of multilayer interfaces and interface spacing in Al-Ti nanolayers. Several model interfaces derived from stacking of close-packed layers or face-centered cubic \\{100\\} layers were investigated. The simulations reveal significant and important asymmetries in defect production withmore » $$\\sim$$60\\% of vacancies created in Al layers compared to Ti layers within the Al-Ti multilayer system. The asymmetry in the creation of interstitials is even more pronounced. The asymmetries cause an imbalance in the ratio of vacancies and interstitials in films of dissimilar materials leading to $>$$90\\% of the surviving interstitials located in the Al layers. While in the close-packed nanolayers the interstitials migrate to the atomic layers adjacent to the interface of the Al layers, in the \\{100\\} nanolayers the interstitials migrate to the center of the Al layers and away from the interfaces. The degree of asymmetry and defect ratio imbalance increases as the layer spacing decreases in the multilayer films. Underlying physical processes are discussed including the interfacial strain fields and the individual elemental layer stopping power in nanolayered systems. In addition, experimental work was performed on low-dose (10$$^{16}$ atoms/cm$^2$) helium (He) irradiation on Al/Ti nanolayers (5 nm per film), resulting in He bubble formation $$\\sim$$1 nm in diameter in the Ti film near the interface. The correlation between the preferential flux of displaced atoms from Ti films to Al films during the defect production that is revealed in the simulations and the morphology and location of He bubbles from the experiments is discussed.« less

Atomic layer deposition of (K,Na)(Nb,Ta)O{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sønsteby, Henrik Hovde, E-mail: henrik.sonsteby@kjemi.iuio.no; Nilsen, Ola; Fjellvåg, Helmer

2016-07-15

Thin films of complex alkali oxides are frequently investigated due to the large range of electric effects that are found in this class of materials. Their piezo- and ferroelectric properties also place them as sustainable lead free alternatives in optoelectronic devices. Fully gas-based routes for deposition of such compounds are required for integration into microelectronic devices that need conformal thin films with high control of thickness- and composition. The authors here present a route for deposition of materials in the (K,Na)(Nb,Ta)O{sub 3}-system, including the four end members NaNbO{sub 3}, KNbO{sub 3}, NaTaO{sub 3}, and KTaO{sub 3}, using atomic layer depositionmore » with emphasis on control of stoichiometry in such mixed quaternary and quinary compunds.« less

Partially Ionized Beam Deposition of Silicon-Dioxide and Aluminum Thin Films - Defects Generation.

NASA Astrophysics Data System (ADS)

Wong, Justin Wai-Chow

1987-09-01

Detect formation in SiO_2 and Al thin films and interfaces were studied using a partially ionized beam (PIB) deposition technique. The evaporated species (the deposition material) were partially ionized to give an ion/atom ratio of <=q0.1% and the substrate was biased at 0-5kV during the deposition. The results suggest that due to the ion bombardment, stoichiometric SiO_2 films can be deposited at a low substrate temperature (~300 ^circC) and low oxygen pressure (<=q10^{-4} Torr). Such deposition cannot be achieved using conventional evaporation-deposition techniques. However, traps and mobile ions were observed in the oxide and local melt-down was observed when a sufficiently high electric field was applied to the film. For the PIB Al deposition on the Si substrate, stable Al/Si Schottky contact was formed when the substrate bias was <=q1kV. For a substrate bias of 2.5kV, the capacitance of the Al/Si interface increased dramatically. A model of self-ion implantation with a p-n junction created by the Al^+ ion implantation was proposed and tested to explain the increase of the interface capacitance. Several deep level states at the Al/Si interface were observed using Deep Level Transient Spectroscopy (DLTS) technique when the film was deposited at a bias of 3kV. The PIB Al films deposited on the Si substrate showed unusually strong electromigration resistance under high current density operation. This phenomenon was explained by the highly oriented microstructure of the Al films created by the self-ion bombardment during deposition. These findings show that PIB has potential applications in a number of areas, including low temperature thin film deposition, and epitaxial growth of thin films in the microelectronics thin film industry.

Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

NASA Astrophysics Data System (ADS)

Tan, Feihu; Zhang, Qingmeng; Zhao, Hongbin; Wei, Feng; Du, Jun

2018-03-01

PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

Tools to Study Interfaces for Superconducting, Thermoelectric, and Magnetic Materials at the University of Houston

DTIC Science & Technology

2016-09-01

The MBE system, which grows crystalline thin films in ultrahigh vacuum (UHV) with precise control of thickness, composition, and morphology, will...used on our sputtering system to fabricate thin films with interfaces. - The electronic structures of these materials will be investigated using the...magnetization/transport measurements. The MBE system, which grows crystalline thin films in ultrahigh vacuum (UHV) with precise control of thickness, composition

Interfacial Coupling-Induced Ferromagnetic Insulator Phase in Manganite Film

DOE PAGES

Zhang, Bangmin; Wu, Lijun; Yin, Wei-Guo; ...

2016-06-08

Interfaces with subtle differences in atomic and electronic structures in perovskite ABO 3 heterostructures often yield intriguingly different properties, yet their exact roles remain elusive. Here, we report an integrated study of unusual transport, magnetic, and structural properties of Pr 0.67Sr 0.33MnO 3 film on SrTiO 3 substrate. The variations in the out-of-plane lattice constant and BO 6 octahedral rotation across the Pr 0.67Sr 0.33MnO 3/SrTiO 3 interface strongly depend on the thickness of the Pr 0.67Sr 0.33MnO 3 film. In the 12-nm film, a new interface-sensitive ferromagnetic polaronic insulator (FI') phase is formed during the cubic-to-tetragonal phase transition ofmore » SrTiO 3, apparently due to the enhanced electron–phonon interaction and atomic disorder in the film. The transport properties of the FI' phase in the 30-nm film are masked because of the reduced interfacial coupling and smaller interface-to-volume ratio. In conclusion, this work demonstrates how thickness-dependent interfacial coupling leads to the formation of a theoretically predicted ferromagnetic–polaronic insulator, as illustrated in a new phase diagram, that is otherwise ferromagnetic metal (FM) in bulk form.« less

Interfacial Coupling-Induced Ferromagnetic Insulator Phase in Manganite Film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Bangmin; Wu, Lijun; Yin, Wei-Guo

Interfaces with subtle differences in atomic and electronic structures in perovskite ABO 3 heterostructures often yield intriguingly different properties, yet their exact roles remain elusive. Here, we report an integrated study of unusual transport, magnetic, and structural properties of Pr 0.67Sr 0.33MnO 3 film on SrTiO 3 substrate. The variations in the out-of-plane lattice constant and BO 6 octahedral rotation across the Pr 0.67Sr 0.33MnO 3/SrTiO 3 interface strongly depend on the thickness of the Pr 0.67Sr 0.33MnO 3 film. In the 12-nm film, a new interface-sensitive ferromagnetic polaronic insulator (FI') phase is formed during the cubic-to-tetragonal phase transition ofmore » SrTiO 3, apparently due to the enhanced electron–phonon interaction and atomic disorder in the film. The transport properties of the FI' phase in the 30-nm film are masked because of the reduced interfacial coupling and smaller interface-to-volume ratio. In conclusion, this work demonstrates how thickness-dependent interfacial coupling leads to the formation of a theoretically predicted ferromagnetic–polaronic insulator, as illustrated in a new phase diagram, that is otherwise ferromagnetic metal (FM) in bulk form.« less

Molecular dynamics study of structure and vibrational spectra at zwitterionoic lipid/aqueous KCl, NaCl, and CaCl2 solution interfaces

NASA Astrophysics Data System (ADS)

Ishiyama, Tatsuya; Shirai, Shinnosuke; Okumura, Tomoaki; Morita, Akihiro

2018-06-01

Molecular dynamics (MD) simulations of KCl, NaCl, and CaCl2 solution/dipalmytoylphosphatidylcholine lipid interfaces were performed to analyze heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectra in relation to the interfacial water structure. The present MD simulation well reproduces the experimental spectra and elucidates a specific cation effect on the interfacial structure. The K+, Na+, and Ca2+ cation species penetrate in the lipid layer more than the anions in this order, due to the electrostatic interaction with negative polar groups of lipid, and the electric double layer between the cations and anions cancels the intrinsic orientation of water at the water/lipid interface. These mechanisms explain the HD-VSFG spectrum of the water/lipid interface and its spectral perturbation by adding the ions. The lipid monolayer reverses the order of surface preference of the cations at the solution/lipid interface from that at the solution/air interface.

Effects of Oxide Film on the Corrosion Resistance of Titanium Grade 7 in Fluoride-Containing NaCl Brines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lian, T; Whalen, M T; Wong, L

2004-11-30

The effects of oxide film on the corrosion behavior of Titanium Grade 7 (0.12-0.25% Pd) in fluoride-containing NaCl brines have been investigated. With the presence of a 0.6 {micro}m thick oxide layer, the annealed Ti grade 7 exhibited a significant improvement on the anodic polarization behavior. However, the oxide film did not demonstrate sustainable corrosion resistance in fluoride-containing solutions.

How are soap bubbles blown? Fluid dynamics of soap bubble blowing

NASA Astrophysics Data System (ADS)

Davidson, John; Lambert, Lori; Sherman, Erica; Wei, Timothy; Ryu, Sangjin

2013-11-01

Soap bubbles are a common interfacial fluid dynamics phenomenon having a long history of delighting not only children and artists but also scientists. In contrast to the dynamics of liquid droplets in gas and gas bubbles in liquid, the dynamics of soap bubbles has not been well documented. This is possibly because studying soap bubbles is more challenging due to there existing two gas-liquid interfaces. Having the thin-film interface seems to alter the characteristics of the bubble/drop creation process since the interface has limiting factors such as thickness. Thus, the main objective of this study is to determine how the thin-film interface differentiates soap bubbles from gas bubbles and liquid drops. To investigate the creation process of soap bubbles, we constructed an experimental model consisting of air jet flow and a soap film, which consistently replicates the conditions that a human produces when blowing soap bubbles, and examined the interaction between the jet and the soap film using the high-speed videography and the particle image velocimetry.

Effect of interface-dependent crystalline boundary on sub-threshold characteristics in a solution-processed 6,13-bis(triisopropylsilylethynyl)-pentacene thin-film transistor

NASA Astrophysics Data System (ADS)

Kwon, Jin-Hyuk; Kang, In Man; Bae, Jin-Hyuk

2014-03-01

We demonstrate how the sub-threshold characteristics are affected by the density of crystalline domain boundaries directly governed by an organic semiconductor (OSC) - a gate insulator interface in a solution-processed 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) thin-film transistor (TFT). For generation of an engineered interface, a self assembled monolayer of octadecyltricholorosilane (OTS) was produced between a solution processed TIPS-pentacene film and a silicon dioxide layer. The interfacial charge trap density (Ntrap) deduced from the sub-threshold characteristics was significantly minimized after OTS treatment due to reduced crystal domain boundaries in the TIPS-pentacene film. In addition, the carrier mobility exhibits a value twice as large by OTS treatment. It is found that less crystal domain boundaries in the solution-processed OSC obtained from the engineered interface play an important role in inducing improved sub-threshold characteristics together with increased carrier mobility in organic TFTs.

Fluorescence light microscopy of pulmonary surfactant at the air-water interface of an air bubble of adjustable size.

PubMed Central

Knebel, D; Sieber, M; Reichelt, R; Galla, H-J; Amrein, M

2002-01-01

The structural dynamics of pulmonary surfactant was studied by epifluorescence light microscopy at the air-water interface of a bubble as a model close to nature for an alveolus. Small unilamellar vesicles of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol, a small amount of a fluorescent dipalmitoylphosphatidylcholine-analog, and surfactant-associated protein C were injected into the buffer solution. They aggregated to large clusters in the presence of Ca(2+) and adsorbed from these units to the interface. This gave rise to an interfacial film that eventually became fully condensed with dark, polygonal domains in a fluorescent matrix. When now the bubble size was increased or decreased, respectively, the film expanded or contracted. Upon expansion of the bubble, the dark areas became larger to the debit of the bright matrix and reversed upon contraction. We were able to observe single domains during the whole process. The film remained condensed, even when the interface was increased to twice its original size. From comparison with scanning force microscopy directly at the air-water interface, the fluorescent areas proved to be lipid bilayers associated with the (dark) monolayer. In the lung, such multilayer phase acts as a reservoir that guarantees a full molecular coverage of the alveolar interface during the breathing cycle and provides mechanical stability to the film. PMID:12080141

Non-polar p-type Zn0.94Mn0.05Na0.01O texture: Growth mechanism and codoping effect

NASA Astrophysics Data System (ADS)

Zhang, L. Q.; Lu, B.; Lu, Y. H.; Ye, Z. Z.; Lu, J. G.; Pan, X. H.; Huang, J. Y.

2013-02-01

The microstructure and crystal orientations of polycrystalline films crucially affect the properties and performance of the films. Controlling preferred orientations (PO) and related film morphology are necessary to obtain the desirable properties. In this paper, we demonstrate a rational and effective route toward the realization of non-polar p-type ZnO thin film with surface texture on quartz substrate through Mn-Na codoping. It is uncovered experimentally and theoretically that mono-doping of Mn creates opportunity to realize PO from polar (c-axis) to non-polar ((101¯0), (101¯1), and (112¯0)) changing. With Mn-Na codoping, an acute modulation of the growth behavior and electrical conductivity of the film have been revealed, leading to weak p-type non-polar Zn0.94Mn0.05Na0.01O (ZMNO) texture. The dominant mechanism for the non-polar self-texture in the current paper is deliberately elucidated as resulting from the interplane surface diffusion with the cooperative effect of impurity dopants. The ZMNO films exhibit p-type conduction with hole concentration of 9.51 × 1015-1.86 × 1017 cm-3 and enhanced room temperature (RT) ferromagnetism possessing a saturation magnetization (Ms) of 1.52 μB/Mn. The results have potential applications in development of non-polar optoelectronic devices such as lighting emitting diodes (LEDs).

Atomic layer epitaxy of YBaCuO for optoelectronic applications

NASA Technical Reports Server (NTRS)

Skogman, R. A.; Khan, M. A.; Van Hove, J. M.; Bhattarai, A.; Boord, W. T.

1992-01-01

An MOCVD-based atomic-layer epitaxy process is being developed as a potential solution to the problems of film-thickness and interface-abruptness control which are encountered when fabricating superconductor-insulator-superconductor devices using YBa2Cu3O(7-x). In initial studies, the atomic-layer MOCVD process yields superconducting YBa2Cu3O(7-x) films with substrate temperatures of 605 C during film growth, and no postdeposition anneal. The low temperature process yields a smooth film surface and can reduce interface degradation due to diffusion.

Field emission from amorphous carbon films grown by electrochemical deposition using methanol liquid

NASA Astrophysics Data System (ADS)

Kiyota, H.; Higashi, M.; Kurosu, T.; Iida, M.

2006-05-01

The field emission from an amorphous carbon (a-C) film grown by electrochemical deposition has been studied. The deposition of the a-C film was accomplished by applying a direct-current potential to a substrate that was immersed in methanol. Both scanning electron microscopy and Raman results indicate that smooth and homogeneous a-C films are grown on specific substrates such as Ti and Al. Field emission measurements demonstrate excellent emission properties such as threshold fields as low as 5 V/μm. Enhancement factors are estimated to be in the range of 1300-1500; these are attributed to local field enhancements around sp2 carbon clusters that are embedded in the a-C films. Emission properties of a-C films grown on Si exhibit a current saturation under higher applied fields. These saturation characteristics are explained by effects of a potential barrier at the interface between the a-C film and the substrate. The interface barrier is reduced by formation of the Ti interfacial layer, suggesting that the formation of TiC decreases the contact resistance between the substrate and the a-C film. Therefore, an approach to use carbide formation at the interface is verified as useful to improve the emission properties of a-C films.

Aerosol-assisted molten salt synthesis of NaInS(2) nanoplates for use as a new photoanode material.

PubMed

Mann, Amanda K P; Wicker, Susanne; Skrabalak, Sara E

2012-12-04

NaInS(2) , a H(2) -evolving photocatalyst, is synthesized as single-crystalline hexagonal plates by coupling a molten salt synthesis with ultrasonic spray pyrolysis (USP) for the first time. USP NaInS(2) films are used as a new photoanode material and have an initial photocurrent of ≈37 μA/cm(2) upon illumination and activities 25 times greater than films made from a standard non-aerosol NaInS(2) sample. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wick, Collin D.; Dang, Liem X.

NaCl pairing and dissociation was investigated at the CCl 4-water and 1,2-dichloroethane (DCE)-water interfaces, and compared with dissociation results in the bulk and at the air-water interface utilizing polarizable potentials. The transition path sampling methodology was used to calculate the rate constant for dissociation, while umbrella sampling was used to map out a free energy profile for NaCl dissociation. The results found that ion pairing was weakest at the organic-water interfaces, even weaker than in the water bulk. This is in contrast to what has been observed previously for the air-water interface, in which NaCl ion paring is stronger thanmore » in the bulk [Wick, C.D. J. Phys. Chem. C, 2009, 113, 6356]. The consequence of the weaker binding at the organic-water interfaces was that ion dissociation was faster than in the other systems studied. Interactions of the organic phase with the ions influenced the magnitude of the Cl - dipole moment, and at the organic-water interfaces, the average Cl - dipole was found to be lower than at the air-water interface, weakening interactions with Na +. Work was performed at the Pacific Northwest National Laboratory (PNNL) was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). PNNL is operated by Battelle for the DOE.« less

Effects of various plasticizers and nanoclays on the mechanical properties of red algae film.

PubMed

Jang, S A; Shin, Y J; Seo, Y B; Song, K B

2011-04-01

To manufacture red algae (RA) film, we used various plasticizers such as glycerol, sorbitol, sucrose, fructose, and polypropylene glycol (PPG), and then determined the mechanical properties of the RA films. The tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of the films containing various plasticizers ranged between 0.43 to 9.10 MPa, 10.93% to 47.17%, and 1.28 to 1.42 ng m/m2sPa, respectively. RA films containing fructose as a plasticizer had the best mechanical properties of all the films evaluated. Incorporation of nanoclay (Cloisite Na+ and 30B) improved the mechanical properties of the films. RA film with 3% Cloisite Na+ had a TS of 10.89, while RA film with 30B had a TS of 10.85 MPa; these films also had better E and WVP values than the other RA films evaluated. These results suggest that RA/nanoclay composite films are suitable for use as food packaging materials.   Edible RE/nanoclay composite films prepared in the present investigation can be applied in food packaging.

Molecular beam epitaxially grown copper indium diselenide and copper gallium diselenide films

NASA Astrophysics Data System (ADS)

Yoon, Seokhyun

2005-12-01

To eliminate the influence of grain boundaries, CuInSe2 (CIS) and CuGaSe2 (CGS) films were grown on (100) GaAs wafers. The effects of Cu to III metal ratio and dosing with Na on the growth mode and defect properties were studied at two growth temperatures. The impact of post-annealing in Se on the defect structure of CGS film was also studied. Two-dimensional simulations were used to better understand the role of grain boundary on cell performance. For growth at 360°C, the In-rich CIS films were polycrystalline, whereas the Cu-rich CIS films were epitaxial exhibiting a Stranski-Krastanov (S-K) growth mode. It is proposed that a Cu-Se secondary phase enhances the mobility of adatoms, allowing epitaxial growth to a critical thickness, at which point segregation at the nucleation sites became faster the rate of growth. Island structures, embedded in a matrix region, were oriented along the [01-1] directed edges with surface undulations apparent on the matrix surface with dominant {112} crystal planes. At the higher growth temperature of 464°C, the CIS films grew epitaxially without the need of a Cu-Se phase. Both CIS films grown at low and high temperatures were nearly relaxed. The segregation of epitaxial Cu1.5Se was also observed in the Cu-rich, Na-dosed CIS film, which is attributed to a surfactant effect of Na. At a growth temperature of 438°C, CGS films showed a S-K growth mode and nearly pseudomorphic growth. Hemispherical islands with twins were observed in the Ga-rich CGS films and epitaxial Cu1.5Se phase were identified in the top region of the island structure. From the PL analysis of Cu-rich, Na-dosed CGS film after Se-annealing, a new defect level located 20 meV above the valence band edge was identified as NaGa acceptor state. Two-dimensional simulation of the impact of grain boundaries on device performance showed that the short circuit current decreases sharply along with the other device parameters below a critical grain size due to the complete depletion. The increase of dark saturation current with decreasing grain size was predicted due to an increase in the recombination current.

Dehydration process in NaCl solutions under various external electric fields

NASA Astrophysics Data System (ADS)

Kadota, Kazunori; Shimosaka, Atsuko; Shirakawa, Yoshiyuki; Hidaka, Jusuke

2007-06-01

Ionic motions at solid-liquid interface in supersaturated NaCl solutions have been investigated by molecular dynamics (MD) simulation for understanding crystal growth processes. The density profile in the vicinity of the interfaces between NaCl(100) and the supersaturated NaCl solution was calculated. Diffusion coefficients of water molecules in the solution were estimated as a function of distance from the crystal interface. It turned out that the structure and dynamics of the solution in the interfaces was different from those of bulk solution owing to electric fields depending on the surface charge. Therefore, the electric field was applied to the supersaturated solutions and dehydration phenomenon occurring in the process of the crystal growth was discussed. As the electric field increased, it was observed that the Na+ keeping strongly hydration structure broke out by the electric force. In supersaturated concentration, the solution structure is significantly different from that of dilution and has a complicated structure with hydration ions and clusters of NaCl. If the electric fields were applied to the solutions, the breakout of hydration structure was not affected with increasing the supersaturated ratio. This reason is that the cluster structures are destroyed by the electric force. The situation depends on the electric field or crystal surface structure.

Temperature Dependence of Behavior of Interface Between Molten Sn and LiCl-KCl Eutectic Melt Due to Rising Gas Bubble

NASA Astrophysics Data System (ADS)

Natsui, Shungo; Nashimoto, Ryota; Takai, Hifumi; Kumagai, Takehiko; Kikuchi, Tatsuya; Suzuki, Ryosuke O.

2016-06-01

The behavior of the interface between molten Sn and the LiCl-KCl eutectic melt system was observed directly. We found that the transient behavior of the interface exhibits considerable temperature dependence through a change in its physical properties. The "metal film" generated in the upper molten salt phase significantly influences the shape of the interface. Although the lifetime of the metal film depends on the gas flow rate, it is not affected by the buoyancy if the interfacial tension is dominant.

Electrochemical aspects of copper atmospheric corrosion in the presence of sodium chloride

DOE PAGES

Schindelholz, Eric John; Cong, Hongbo; Jove-Colon, Carlos F.; ...

2018-04-26

Here, this study describes the evolving state of electrolyte and corrosion processes associated with sodium chloride on copper at the initial stage of corrosion and the critical implications of this behavior on controlling kinetics and damage distributions. Sodium chloride droplets were placed on copper in humid conditions and the resulting electrolyte properties, corrosion products and damage were characterized over time using time-lapse imaging, micro Raman spectroscopy, TOF-SIMS and optical profilometry. Within minutes of NaCl droplet placement, NaOH-rich films resultant from oxygen reduction advanced stepwise from the droplets, leaving behind concentric trenching attack patterns suggestive of moving anode-cathode pairs at themore » alkaline film front. Corrosion attack under these spreading alkaline films was up to 10x greater than under the original NaCl drops. Furthermore, solid Cu 2Cl(OH) 3 shells formed over the surface of the NaCl drops within hours of exposure. Thermodynamic modeling along with immersed electrochemical experiments in simulated droplet and films electrolytes were used to rationalize this behavior and build a description of the rapidly evolving corroding system.« less

Electrochemical aspects of copper atmospheric corrosion in the presence of sodium chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schindelholz, Eric John; Cong, Hongbo; Jove-Colon, Carlos F.

Here, this study describes the evolving state of electrolyte and corrosion processes associated with sodium chloride on copper at the initial stage of corrosion and the critical implications of this behavior on controlling kinetics and damage distributions. Sodium chloride droplets were placed on copper in humid conditions and the resulting electrolyte properties, corrosion products and damage were characterized over time using time-lapse imaging, micro Raman spectroscopy, TOF-SIMS and optical profilometry. Within minutes of NaCl droplet placement, NaOH-rich films resultant from oxygen reduction advanced stepwise from the droplets, leaving behind concentric trenching attack patterns suggestive of moving anode-cathode pairs at themore » alkaline film front. Corrosion attack under these spreading alkaline films was up to 10x greater than under the original NaCl drops. Furthermore, solid Cu 2Cl(OH) 3 shells formed over the surface of the NaCl drops within hours of exposure. Thermodynamic modeling along with immersed electrochemical experiments in simulated droplet and films electrolytes were used to rationalize this behavior and build a description of the rapidly evolving corroding system.« less

Weak ferromagnetism and short range polar order in NaMnF3 thin films

NASA Astrophysics Data System (ADS)

KC, Amit; Borisov, Pavel; Shvartsman, Vladimir V.; Lederman, David

2017-02-01

The orthorhombically distorted perovskite NaMnF3 has been predicted to become ferroelectric if an a = c distortion of the bulk Pnma structure is imposed. In order to test this prediction, NaMnF3 thin films were grown on SrTiO3 (001) single crystal substrates via molecular beam epitaxy. The best films were smooth and single phase with four different twin domains. In-plane magnetization measurements revealed the presence of antiferromagnetic ordering with weak ferromagnetism below the Néel temperature TN = 66 K. For the dielectric studies, NaMnF3 films were grown on a 30 nm SrRuO3 (001) layer used as a bottom electrode grown via pulsed laser deposition. The complex permittivity as a function of frequency indicated a strong Debye-like relaxation contribution characterized by a distribution of relaxation times. A power-law divergence of the characteristic relaxation time revealed an order-disorder phase transition at 8 K. The slow relaxation dynamics indicated the formation of super-dipoles (superparaelectric moments) that extend over several unit cells, similar to polar nanoregions of relaxor ferroelectrics.

Molecular tailoring of interfaces for thin film on substrate systems

NASA Astrophysics Data System (ADS)

Grady, Martha Elizabeth

Thin film on substrate systems appear most prevalently within the microelectronics industry, which demands that devices operate in smaller and smaller packages with greater reliability. The reliability of these multilayer film systems is strongly influenced by the adhesion of each of the bimaterial interfaces. During use, microelectronic components undergo thermo-mechanical cycling, which induces interfacial delaminations leading to failure of the overall device. The ability to tailor interfacial properties at the molecular level provides a mechanism to improve thin film adhesion, reliability and performance. This dissertation presents the investigation of molecular level control of interface properties in three thin film-substrate systems: photodefinable polyimide films on passivated silicon substrates, self-assembled monolayers at the interface of Au films and dielectric substrates, and mechanochemically active materials on rigid substrates. For all three materials systems, the effect of interfacial modifications on adhesion is assessed using a laser-spallation technique. Laser-induced stress waves are chosen because they dynamically load the thin film interface in a precise, noncontacting manner at high strain rates and are suitable for both weak and strong interfaces. Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. The influence of processing parameters on adhesion is examined for photodefinable polyimide films on silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). Interfacial strength increases when films are processed with an exposure step as well as a longer cure cycle. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The high toughness of this interface (ca. 100 J/m2) makes it difficult to use more conventional interfacial fracture testing techniques. Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface in an on-demand fashion. The SAM end-group functionality is systematically varied and the corresponding effect on interfacial adhesion between a transfer printed gold (Au) film and a fused silica substrate is measured. SAMs with four different end groups are investigated: methyl, amine, bromine and thiol. In addition to these four end groups, mixed monolayers of increasing molar ratio of thiol to methyl SAMs in solution are investigated. There is a strong dependence of interfacial chemistry on the adhesion strength of Au films. In addition to the chemical functionality of the SAM, surface roughness of the underlying substrate also has a significant impact on the interfacial strength. Thin films of mechanochemically active polymer are subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produces large amplitude stresses (>100 MPa) in short time frames (10-20 ns), leading to very high strain-rates (ca. 107-108 s -1). The polymer system, spiropyran (SP)- linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP is evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions. In addition to SP-linked polymer films, the activation of spiropyran interfacial molecules with different side groups is characterized as they adsorb onto a SAM platform with preferential amine terminating chemistry. The reactivity of SP monolayers due to UV irradiation is evaluated by water contact angle goniometry and fluorescence spectroscopy. Side groups on the interfacial spiropyran molecule affect the reactivity and the proximity of neighboring spiropyrans can prevent efficient mobility.

Structured Ionomer Thin Films at Water Interface: Molecular Dynamics Simulation Insight

DOE PAGES

Aryal, Dipak; Agrawal, Anupriya; Perahia, Dvora; ...

2017-08-23

Controlling the structure and dynamics of thin films of ionizable polymers at water interfaces is critical to their many applications. As the chemical diversity within one polymer is increased, controlling the structure and dynamics of the polymer, which is a key to their use, becomes a challenge. Here molecular dynamics simulations (MD) are used to obtain molecular insight into the structure and dynamics of thin films of one such macromolecule at the interface with water. The polymer consists of an ABCBA topology with randomly sulfonated polystyrene (C), tethered symmetrically to flexible poly(ethylene- r-propylene) blocks (B), and end-capped by a poly(more » t-butylstyrene) block (A). The compositions of the interfacial and bulk regions of thin films of the ABCBA polymers are followed as a function of exposure time to water. We find that interfacial rearrangements take place where buried ionic segments migrate toward the water interface. The hydrophobic blocks collapse and rearrange to minimize their exposure to water. In conclusion, the water that initially drives interfacial reengagements breaks the ionic clusters within the film, forming a dynamic hydrophilic internal network within the hydrophobic segments.« less

Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

PubMed Central

Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

2016-01-01

Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors. PMID:27869132

Misfit strain driven cation inter-diffusion across an epitaxial multiferroic thin film interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sankara Rama Krishnan, P. S.; Munroe, Paul; Nagarajan, V.

Cation intermixing at functional oxide interfaces remains a highly controversial area directly relevant to interface-driven nanoelectronic device properties. Here, we systematically explore the cation intermixing in epitaxial (001) oriented multiferroic bismuth ferrite (BFO) grown on a (001) lanthanum aluminate (LAO) substrate. Aberration corrected dedicated scanning transmission electron microscopy and electron energy loss spectroscopy reveal that the interface is not chemically sharp, but with an intermixing of ∼2 nm. The driving force for this process is identified as misfit-driven elastic strain. Landau-Ginzburg-Devonshire-based phenomenological theory was combined with the Sheldon and Shenoy formula in order to understand the influence of boundary conditions andmore » depolarizing fields arising from misfit strain between the LAO substrate and BFO film. The theory predicts the presence of a strong potential gradient at the interface, which decays on moving into the bulk of the film. This potential gradient is significant enough to drive the cation migration across the interface, thereby mitigating the misfit strain. Our results offer new insights on how chemical roughening at oxide interfaces can be effective in stabilizing the structural integrity of the interface without the need for misfit dislocations. These findings offer a general formalism for understanding cation intermixing at highly strained oxide interfaces that are used in nanoelectronic devices.« less

Energy level alignment and molecular conformation at rubrene/Ag interfaces: Impact of contact contaminations on the interfaces

NASA Astrophysics Data System (ADS)

Sinha, Sumona; Wang, C.-H.; Mukherjee, M.

2017-07-01

This paper addresses the impact of electrode contaminations on the interfacial energy level alignment, the molecular conformation, orientation and surface morphology deposited organic film at organic semiconductor/noble metal interfaces by varying of film thickness from sub-monolayer to multilayer, which currently draws significant attention with regard to its application in organic electronics. The UHV clean Ag and unclean Ag were employed as substrate whereas rubrene was used as an organic semiconducting material. The photoelectron spectroscopy (XPS and UPS) was engaged to investigate the evolution of interfacial energetics; polarization dependent near edge x-ray absorption fine structure spectroscopy (NEXAFS) was employed to understand the molecular conformation as well as orientation whereas atomic force microscopy (AFM) was used to investigate the surface morphologies of the films. The adventitious contamination layer was acted as a spacer layer between clean Ag substrate surface and rubrene molecular layer. As a consequence, hole injection barrier height, interface dipole as well as molecular-conformation, molecular-orientation and surface morphology of rubrene thin films were found to depend on the cleanliness of Ag substrate. The results have important inferences about the understanding of the impact of substrate contamination on the energy level alignment, the molecular conformation as well as orientation and surface morphology of deposited rubrene thin film at rubrene/Ag interfaces and are beneficial for the improvement of the device performance.

Understanding the Effect of Na in Improving the Performance of CuInSe 2 Based Photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobson, Kevin D.

Cu(In,Ga)Se 2 (CIGS) thin film photovoltaic technology is in the early stages of commercialization with an annual manufacturing capacity over 1 GW and has demonstrated the highest module efficiency of any of the thin film technologies. However there still is a lack of fundamental understanding of the relationship between the material properties and solar cell device operation. It is well known that the incorporation of a small amount of Na into the CIGS film during processing is essential for high efficiency devices. However, there are conflicting explanations for how Na behaves at the atomic scale. This report investigates how Namore » is incorporated into the CIGS device structure and evaluates the diffusion of Na into CIGS grain boundaries (GBs) and bulk crystallites. Participants: This project was carried out at the Institute of Energy Conversion at the University of Delaware, collaborating with the Rockett group at the University of Illinois Urbana-Champagne. Significant Findings: The significant outcomes of this project for each task include; Task 1.0: Effect of Na in Devices Fabricated on PVD Deposited CIGS; Na diffusion occurs through the Mo back contact via GBs driven by the presence of oxygen; Na reversibly compensates donor defects in CIGS GBs,Task 2.0: Na Incorporation in Single Crystal CIGS; and bulk Na diffusion proceeds rapidly such that grains are Na-saturated immediately following CIGS thin film manufacture. Industry Guidance: The presented results offer interesting concepts for modification of manufacturing processes of CIGS-based PV modules. Possible approaches to improve control of Na uptake and uniformly increase levels in CIGS films are highlighted for processes that employ either soda-lime glass or NaF as the Na source. Concepts include the potential of O 2 or oxidative based treatments of Mo back contacts to improve Na diffusion through the metal film and increase Na uptake into the growing CIGS. This project has also offered fundamental understanding of the behavior of Na in CIGS grains and GBs, particularly the confirmation that CIGS grains will be saturated with Na immediately following manufacture Summary of Results: Most commercially available CIGS modules are fabricated on soda-lime glass coated with Mo as the back electric contact, and Na in the glass diffuses through the Mo layer into the CIGS during film growth. In Task 1 the transport of Na through Mo was evaluated using x-ray photoelectron surface spectroscopy along with diffusion modeling to obtain diffusion coefficients at several temperatures. It was determined that Na diffusion in Mo only occurs along GBs and that oxygen provides an additional driving force to enhance Na transport. Device data revealed that older Mo substrates with a greater amount of surface oxide resulted in slightly higher efficiencies due to enhanced Na incorporation caused by the oxide. This finding shows that Mo substrates could potentially undergo an oxidation treatment prior to CIGS deposition to further improve and control the incorporation of Na. To determine if in-grain Na affects device performance, in Task 1 Na was selectively removed from GBs using heat/rinse cycles. Due to the low temperature of this treatment, Na at GBS remained mobile while diffusion within the bulk was too slow for Na removal from the grain interiors. Changes in electrical properties were evaluated using conductivity and Seebeck coefficient measurements, with both decreasing as Na was removed to reach values similar to Na-free controls samples. This can be explained by the compensation of donor defects by Na, causing an increase in the free carrier concentration. Devices showed a decrease in open-circuit voltage after Na removal confirming that the beneficial effects of GB Na. The findings of this project will provide guidance for rational optimization of Na incorporation procedures in the manufacturing of CIGS solar cells. While it is known that Na segregates at CIGS GBs, the nature and role of Na diffusion into grain interiors was less clear. In Task 2, single crystal CuInSe 2 was used as a model system to represent the grain interiors of CIGS. Crystals processed by two different methods of different compositions and dislocation densities, were evaluated. Diffusion coefficients were obtained at two temperatures after Na diffusion, giving near identical values, ~2x10 11 cm 2/s and ~6x10 11 cm2/s at 420°C and 480°C, respectively, for each crystal. Characterization confirmed that dislocation densities were too low to significantly impact the effective diffusion coefficient. The Cu-poor crystal had a higher solubility suggesting that Na diffusion is mediated by Cu-vacancies, but was not accompanied by an expected increase in diffusion coefficient. The activation energy for diffusion was similar to values expected for interstitial diffusion, but the large size of Na + ions should result in a solubility that is much lower than what was experimentally measured. A hybrid interstitial-substitutional mechanism is proposed that combines the fast diffusion of interstitial atoms with the high solubility common for substitutional impurities. Lattice diffusion of Na proceeds fast enough that CIGS grain interiors will have Na concentrations near the solubility limit of 1018 cm -3 when manufactured under standard conditions. Na and K treated epitaxial CIS films showed a significant increase in cathodoluminescence emission intensity, indicating a reduction of non-radiative recombination pathways, which is consistent with improvements in CIGS device performance, though the mechanism is not clear. Pathways forward: Despite the success of this project, there are a number of questions remaining related to further the understanding of the chemistry of Na in CIGS films and devices. These include further elucidation of the mechanisms of Na passivation in CIGS GBs, with identification of which defects are involved and confirmation of the possible effects of in-grain Na on device performance. To complete analysis of the cell structure, conformation of the presence and possible chemistries of Na at the CIGS/CdS junction and/or in the front transparent contacts, and its effects on device performance, is needed.« less

Electricity in foams: from one soapy interface to the macroscopic material

NASA Astrophysics Data System (ADS)

Biance, Anne-Laure

2017-11-01

Liquid foams (a dispersion of gas bubbles in a soapy solution) destabilize with time due to coarsening, coalescence and gravity driven drainage. We propose here to inhibit (or trigger) the foam destabilization by applying an electric field to the material. This effect is investigated at the different scales of the system: one soapy interface, one liquid film, the macroscopic foam. The generation of an electroosmotic flow near a soapy liquid/gas interface raises many issues. How does the flow affect surfactant repartition? Is there a Marangoni stress at the interface? At the scale of one soap film, how the electric field affects the film stability and deformation? In a macroscopic foam, one can wonder whether the electric field can indeed reverse gravity driven drainage and increase foam lifetime? These different issues are considered by developing new experimental techniques allowing us to probe surfactant repartition at liquid interfaces, soap film thicknesses and liquid foam properties when an electric field is applied. The results will be presented together with a comprehensive picture of the mechanisms arising at each scale of the material, to conclude with the potential use of electricity in liquid foams to control destabilization. Collaborators: Baptiste Blanc, Oriane Bonhomme, Laurent Joly, Christophe Ybert.

The XPS depth profiling and tribological characterization of ion-plated gold on various metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

Friction properties were measured with a gold film; the graded interface between gold and nickel substrate; and the nickel substrate. All sliding was conducted against hard silicon carbide pins in two processes. In the adhesive process, friction arises primarily from adhesion between sliding surfaces. In the abrasion process, friction occurs as a result of the hard pin sliding against the film, indenting into it, and plowing a series of grooves. Copper and 440 C stainless steel substrates were also used. Results indicate that the friction related to both adhesion and abrasion is influenced by coating depth. The trends in friction behavior as a function of film depth are, however, just the opposite. The graded interface exhibited the highest adhesion and friction, while the graded interface resulted in the lowest abrasion and friction. The coefficient of friction due to abrasion is inversely related to the hardness. The greater the hardness of the surface, the lower is the abrasion and friction. The microhardness in the graded interface exhibited the highest hardness due to an alloy hardening effect. Almost no graded interface between the vapor-deposited gold film and the substrates was detected.

Dissociative adsorption of water on Au/MgO/Ag(001) from first principles calculations

NASA Astrophysics Data System (ADS)

Nevalaita, J.; Häkkinen, H.; Honkala, K.

2015-10-01

The molecular and dissociative adsorption of water on a Ag-supported 1 ML, 2 ML and 3 ML-a six atomic layer-thick MgO films with a single Au adatom is investigated using density functional theory calculations. The obtained results are compared to a bulk MgO(001) surface with an Au atom. On thin films the negatively charged Au strengthens the binding of the polar water molecule due to the attractive Au-H interaction. The adsorption energy trends of OH and H with respect to the film thickness depend on an adsorption site. In the case OH or H binds atop Au on MgO/Ag(001), the adsorption becomes more exothermic with the increasing film thickness, while the reverse trend is seen when the adsorption takes place on bare MgO/Ag(001). This behavior can be explained by different bonding mechanisms identified with the Bader analysis. Interestingly, we find that the rumpling of the MgO film and the MgO-Ag interface distance correlate with the charge transfer over the thin film and the interface charge, respectively. Moreover, we employ a modified Born-Haber-cycle to analyze the effect of film thickness to the adsorption energy of isolated Au and OH species on MgO/Ag(001). The analysis shows that the attractive Coulomb interaction between the negatively charged adsorbate and the positive MgO-Ag-interface does not completely account for the weaker binding with increasing film thickness. The redox energy associated with the charge transfer from the interface to the adsorbate is more exothermic with the increasing film thickness and partly compensates the decrease in the attractive Coulomb interaction.

Combining light-harvesting with detachability in high-efficiency thin-film silicon solar cells.

PubMed

Ram, Sanjay K; Desta, Derese; Rizzoli, Rita; Bellettato, Michele; Lyckegaard, Folmer; Jensen, Pia B; Jeppesen, Bjarke R; Chevallier, Jacques; Summonte, Caterina; Larsen, Arne Nylandsted; Balling, Peter

2017-06-01

Efforts to realize thin-film solar cells on unconventional substrates face several obstacles in achieving good energy-conversion efficiency and integrating light-management into the solar cell design. In this report a technique to circumvent these obstacles is presented: transferability and an efficient light-harvesting scheme are combined for thin-film silicon solar cells by the incorporation of a NaCl layer. Amorphous silicon solar cells in p-i-n configuration are fabricated on reusable glass substrates coated with an interlayer of NaCl. Subsequently, the solar cells are detached from the substrate by dissolution of the sacrificial NaCl layer in water and then transferred onto a plastic sheet, with a resultant post-transfer efficiency of 9%. The light-trapping effect of the surface nanotextures originating from the NaCl layer on the overlying solar cell is studied theoretically and experimentally. The enhanced light absorption in the solar cells on NaCl-coated substrates leads to significant improvement in the photocurrent and energy-conversion efficiency in solar cells with both 350 and 100 nm thick absorber layers, compared to flat-substrate solar cells. Efficient transferable thin-film solar cells hold a vast potential for widespread deployment of off-grid photovoltaics and cost reduction.

Controllable film densification and interface flatness for high-performance amorphous indium oxide based thin film transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ou-Yang, Wei, E-mail: OUYANG.Wei@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Kizu, Takio

2014-10-20

To avoid the problem of air sensitive and wet-etched Zn and/or Ga contained amorphous oxide transistors, we propose an alternative amorphous semiconductor of indium silicon tungsten oxide as the channel material for thin film transistors. In this study, we employ the material to reveal the relation between the active thin film and the transistor performance with aid of x-ray reflectivity study. By adjusting the pre-annealing temperature, we find that the film densification and interface flatness between the film and gate insulator are crucial for achieving controllable high-performance transistors. The material and findings in the study are believed helpful for realizingmore » controllable high-performance stable transistors.« less

Scaling behavior in corrosion and growth of a passive film.

PubMed

Aarão Reis, F D A; Stafiej, Janusz

2007-07-01

We study a simple model for metal corrosion controlled by the reaction rate of the metal with an anionic species and the diffusion of that species in the growing passive film between the solution and the metal. A crossover from the reaction-controlled to the diffusion-controlled growth regime with different roughening properties is observed. Scaling arguments provide estimates of the crossover time and film thickness as functions of the reaction and diffusion rates and the concentration of anionic species in the film-solution interface, including a nontrivial square-root dependence on that concentration. At short times, the metal-film interface exhibits Kardar-Parisi-Zhang (KPZ) scaling, which crosses over to a diffusion-limited erosion (Laplacian growth) regime at long times. The roughness of the metal-film interface at long times is obtained as a function of the rates of reaction and diffusion and of the KPZ growth exponent. The predictions have been confirmed by simulations of a lattice version of the model in two dimensions. Relations with other erosion and corrosion models and possible applications are discussed.

Studies on interface between In2O3 and CuInTe2 thin films

NASA Astrophysics Data System (ADS)

Ananthan, M. R.; Malar, P.; Osipowicz, Thomas; Kasiviswanathan, S.

2017-10-01

Interface between dc sputtered In2O3 and stepwise flash evaporated CuInTe2 films were studied by probing Si/In2O3/CuInTe2 and Si/CuInTe2/In2O3 structures with the help of glancing angle X-ray diffraction, Rutherford backscattering spectrometry and micro-Raman spectroscopy. The results showed that in Si/In2O3/CuInTe2 structure, a ∼20 nm thick interface consisting of In, Cu and O had formed between In2O3 and CuInTe2 and was attributed to the diffusion of Cu from CuInTe2 into In2O3 film. On the other hand, in Si/CuInTe2/In2O3 structure, homogeneity of the underlying CuInTe2 film was found lost completely. An estimate of the masses of the constituent elements showed that the damage was caused by loss of Te from CuInTe2 film during the growth of In2O3 film on Si/CuInTe2.

Thin film instabilities: Rayleigh-Taylor with thermocapillarity and Kolmogorov flow in a soap film

NASA Astrophysics Data System (ADS)

Burgess, John Matthew

The Rayleigh-Taylor instability occurs when a more dense fluid layer is suspended above a less dense fluid layer in a gravitational field. The horizontal interface between the two fluids is unstable to infinitesimal deformations and the dense fluid falls. To counteract the destabilizing effects of gravity on the interface between two thin fluid layers, we apply a vertical temperature gradient, heating from below. The dependence of surface tension on temperature (``thermocapillarity'') can cause spatially-varying interfacial forces between two immiscible fluid layers if a variation in temperature along the interface is introduced. With an applied vertical temperature gradient, the deforming interface spontaneously develops temperature variations which locally adjust the surface tension to restore a flat interface. We find that these surface tension gradients can stabilize a more dense thin fluid layer (silicone oil, 0.015 cm thick) above a less dense thin fluid layer (air, 0.025 cm thick) in a gravitational field, in qualitative agreement with linear stability analysis. This is the first experimental observation of the stabilization of Rayleigh-Taylor instability by thermocapillary forces. We also examine the instability of a soap film flow driven by a time-independent force that is spatially periodic in the direction perpendicular to the forcing (Kolmogorov flow). The film is in the x- y plane, where the forcing approximates a shape sin (y)x̂. Linear stability analysis of an idealized model of this flow predicts a critical Reynolds number Rc~2 . In our soap film experiment, we find a critical value Rc~70 . This discrepancy can be ascribed to frictional effects from viscous coupling of gas to the film, which is neglected in the idealized model. The kinematic viscosity of the surrounding gas and the thickness of gas layers on each side of the soap film are varied in the experiments to better understand these frictional effects. We conclude that flows in soap films cannot be decoupled from flows in the surrounding gas.

Strain transfer through film-substrate interface and surface curvature evolution during a tensile test

NASA Astrophysics Data System (ADS)

He, Wei; Han, Meidong; Goudeau, Philippe; Bourhis, Eric Le; Renault, Pierre-Olivier; Wang, Shibin; Li, Lin-an

2018-03-01

Uniaxial tensile tests on polyimide-supported thin metal films are performed to respectively study the macroscopic strain transfer through an interface and the surface curvature evolution. With a dual digital image correlation (DIC) system, the strains of the film and the substrate can be simultaneously measured in situ during the tensile test. For the true strains below 2% (far beyond the films' elastic limit), a complete longitudinal strain transfer is present irrespective of the film thickness, residual stresses and microstructure. By means of an optical surface profiler, the three-dimensional (3D) topography of film surface can be obtained during straining. As expected, the profile of the specimen center remains almost flat in the tensile direction. Nevertheless, a relatively significant curvature evolution (of the same order with the initial curvature induced by residual stresses) is observed along the transverse direction as a result of a Poisson's ratio mismatch between the film and the substrate. Furthermore, finite element method (FEM) has been performed to simulate the curvature evolution considering the geometric nonlinearity and the perfect strain transfer at the interface, which agrees well with the experimental results.

Auger electron diffraction study of the growth of Fe(001) films on ZnSe(001)

NASA Astrophysics Data System (ADS)

Jonker, B. T.; Prinz, G. A.

1991-03-01

The growth of Fe films on ZnSe(001) epilayers and bulk GaAs(001) substrates has been studied to determine the mode of film growth, the formation of the interface, and the structure of the overlayer at the 1-10 monolayer level. Auger electron diffraction (AED), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction data are obtained for incremental deposition of the Fe(001) overlayer. The coverage dependence of the AED forward scattering peaks reveals a predominantly layer-by-layer mode of film growth at 175 °C on ZnSe, while a more three-dimensional growth mode occurs on the oxide-desorbed GaAs(001) substrate. XPS studies of the semiconductor 3d levels indicate that the Fe/ZnSe interface is less reactive than the Fe/GaAs interface.

X-Ray photoelectron spectroscopy study of radiofrequency-sputtered titanium, carbide, molybdenum carbide, and titanium boride coatings and their friction properties

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1977-01-01

Radiofrequency sputtered coatings of titanium carbide, molybdenum carbide and titanium boride were tested as wear resistant coatings on stainless steel in a pin on disk apparatus. X-ray photoelectron spectroscopy (XPS) was used to analyze the sputtered films with regard to both bulk and interface composition in order to obtain maximum film performance. Significant improvements in friction behavior were obtained when properly biased films were deposited on deliberately preoxidized substrates. XPS depth profile data showed thick graded interfaces for bias deposited films even when adherence was poor. The addition of 10 percent hydrogen to the sputtering gas produced coatings with thin poorly adherent interfaces. Results suggest that some of the common practices in the field of sputtering may be detrimental to achieving maximum adherence and optimum composition for these refractory compounds.

Role of HfO 2/SiO 2 thin-film interfaces in near-ultraviolet absorption and pulsed laser damage

DOE PAGES

Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; ...

2016-07-15

Here, the role of thin-film interfaces in the near-ultraviolet (near-UV) absorption and pulsed laser-induced damage was studied for ion-beam-sputtered and electron-beam-evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and anmore » E-field peak and average intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-UV, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. The results are explained through the similarity of interfacial film structure with structure formed during the codeposition of HfO 2 and SiO 2 materials.« less

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Understanding Interfacial Alignment in Solution Coated Conjugated Polymer Thin Films

DOE PAGES

Qu, Ge; Zhao, Xikang; Newbloom, Gregory M.; ...

2017-08-01

Domain alignment in conjugated polymer thin films can significantly enhance charge carrier mobility. However, the alignment mechanism during meniscus-guided solution coating remains unclear. Furthermore, interfacial alignment has been rarely studied despite its direct relevance and critical importance to charge transport. In this study, we uncover a significantly higher degree of alignment at the top interface of solution coated thin films, using a donor–acceptor conjugated polymer, poly(diketopyrrolopyrrole-co-thiopheneco- thieno[3,2- b]thiophene-co-thiophene) (DPP2T-TT), as the model system. At the molecular level, we observe in-plane π–π stacking anisotropy of up to 4.8 near the top interface with the polymer backbone aligned parallel to the coatingmore » direction. The bulk of the film is only weakly aligned with the backbone oriented transverse to coating. At the mesoscale, we observe a well-defined fibril-like morphology at the top interface with the fibril long axis pointing toward the coating direction. Significantly smaller fibrils with poor orientational order are found on the bottom interface, weakly aligned orthogonal to the fibrils on the top interface. The high degree of alignment at the top interface leads to a charge transport anisotropy of up to 5.4 compared to an anisotropy close to 1 on the bottom interface. We attribute the formation of distinct interfacial morphology to the skin-layer formation associated with high Peclet number, which promotes crystallization on the top interface while suppressing it in the bulk. As a result, we further infer that the interfacial fibril alignment is driven by the extensional flow on the top interface arisen from increasing solvent evaporation rate closer to the meniscus front.« less

Room temperature bonding and debonding of polyimide film and glass substrate based on surface activate bonding method

NASA Astrophysics Data System (ADS)

Takeuchi, Kai; Fujino, Masahisa; Matsumoto, Yoshiie; Suga, Tadatomo

2018-02-01

The temporary bonding of polyimide (PI) films and glass substrates is a key technology for realizing flexible devices with thin-film transistors (TFTs). In this paper, we report the surface activated bonding (SAB) method using Si intermediate layers and its bonding and debonding mechanisms after heating. The bonding interface composed of Si and Fe shows a higher bond strength than the interface of only Si, while the bond strengths of both interfaces decrease with post bonding heating. It is also clarified by composition analysis on the debonded surfaces and cross-sectional observation of the bonding interface that the bond strength depends on the toughness of the intermediated layers and PI. The SAB method using Si intermediate layers is found to be applicable to the bonding and debonding of PI and glass.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lomenzo, Patrick D.; Nishida, Toshikazu, E-mail: nishida@ufl.edu; Takmeel, Qanit

Ferroelectric HfO{sub 2}-based thin films, which can exhibit ferroelectric properties down to sub-10 nm thicknesses, are a promising candidate for emerging high density memory technologies. As the ferroelectric thickness continues to shrink, the electrode-ferroelectric interface properties play an increasingly important role. We investigate the TaN interface properties on 10 nm thick Si-doped HfO{sub 2} thin films fabricated in a TaN metal-ferroelectric-metal stack which exhibit highly asymmetric ferroelectric characteristics. To understand the asymmetric behavior of the ferroelectric characteristics of the Si-doped HfO{sub 2} thin films, the chemical interface properties of sputtered TaN bottom and top electrodes are probed with x-ray photoelectron spectroscopy. Ta-Omore » bonds at the bottom electrode interface and a significant presence of Hf-N bonds at both electrode interfaces are identified. It is shown that the chemical heterogeneity of the bottom and top electrode interfaces gives rise to an internal electric field, which causes the as-grown ferroelectric domains to preferentially polarize to screen positively charged oxygen vacancies aggregated at the oxidized bottom electrode interface. Electric field cycling is shown to reduce the internal electric field with a concomitant increase in remanent polarization and decrease in relative permittivity. Through an analysis of pulsed transient switching currents, back-switching is observed in Si-doped HfO{sub 2} thin films with pinched hysteresis loops and is shown to be influenced by the internal electric field.« less

Light trapping in thin-film solar cells with randomly rough and hybrid textures.

PubMed

Kowalczewski, Piotr; Liscidini, Marco; Andreani, Lucio Claudio

2013-09-09

We study light-trapping in thin-film silicon solar cells with rough interfaces. We consider solar cells made of different materials (c-Si and μc-Si) to investigate the role of size and nature (direct/indirect) of the energy band gap in light trapping. By means of rigorous calculations we demonstrate that the Lambertian Limit of absorption can be obtained in a structure with an optimized rough interface. We gain insight into the light trapping mechanisms by analysing the optical properties of rough interfaces in terms of Angular Intensity Distribution (AID) and haze. Finally, we show the benefits of merging ordered and disordered photonic structures for light trapping by studying a hybrid interface, which is a combination of a rough interface and a diffraction grating. This approach gives a significant absorption enhancement for a roughness with a modest size of spatial features, assuring good electrical properties of the interface. All the structures presented in this work are compatible with present-day technologies, giving recent progress in fabrication of thin monocrystalline silicon films and nanoimprint lithography.

Corrosion behavior of aluminum doped diamond-like carbon thin films in NaCl aqueous solution.

PubMed

Khun, N W; Liu, E

2010-07-01

Aluminum doped diamond-like carbon (DLC:Al) thin films were deposited on n-Si(100) substrates by co-sputtering a graphite target under a fixed DC power (650 W) and an aluminum target under varying DC power (10-90 W) at room temperature. The structure, adhesion strength and surface morphology of the DLC:Al films were characterized by X-ray photoelectron spectroscopy (XPS), micro-scratch testing and atomic force microscopy (AFM), respectively. The corrosion performance of the DLC:Al films was investigated by means of potentiodynamic polarization testing in a 0.6 M NaCl aqueous solution. The results showed that the polarization resistance of the DLC:Al films increased from about 18 to 30.7 k(omega) though the corrosion potentials of the films shifted to more negative values with increased Al content in the films.

Carrier collection losses in interface passivated amorphous silicon thin-film solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neumüller, A., E-mail: alex.neumueller@next-energy.de; Sergeev, O.; Vehse, M.

In silicon thin-film solar cells the interface between the i- and p-layer is the most critical. In the case of back diffusion of photogenerated minority carriers to the i/p-interface, recombination occurs mainly on the defect states at the interface. To suppress this effect and to reduce recombination losses, hydrogen plasma treatment (HPT) is usually applied. As an alternative to using state of the art HPT we apply an argon plasma treatment (APT) before the p-layer deposition in n-i-p solar cells. To study the effect of APT, several investigations were applied to compare the results with HPT and no plasma treatmentmore » at the interface. Carrier collection losses in resulting solar cells were examined with spectral response measurements with and without bias voltage. To investigate single layers, surface photovoltage and X-ray photoelectron spectroscopy (XPS) measurements were conducted. The results with APT at the i/p-interface show a beneficial contribution to the carrier collection compared with HPT and no plasma treatment. Therefore, it can be concluded that APT reduces the recombination centers at the interface. Further, we demonstrate that carrier collection losses of thin-film solar cells are significantly lower with APT.« less

Cellulose ionics: switching ionic diode responses by surface charge in reconstituted cellulose films.

PubMed

Aaronson, Barak D B; Wigmore, David; Johns, Marcus A; Scott, Janet L; Polikarpov, Igor; Marken, Frank

2017-09-25

Cellulose films as well as chitosan-modified cellulose films of approximately 5 μm thickness, reconstituted from ionic liquid media onto a poly(ethylene-terephthalate) (PET, 6 μm thickness) film with a 5, 10, 20, or 40 μm diameter laser-drilled microhole, show significant current rectification in aqueous NaCl. Reconstituted α-cellulose films provide "cationic diodes" (due to predominant cation conductivity) whereas chitosan-doped cellulose shows "anionic diode" effects (due to predominant anion conductivity). The current rectification, or "ionic diode" behaviour, is investigated as a function of NaCl concentration, pH, microhole diameter, and molecular weight of the chitosan dopant. Future applications are envisaged exploiting the surface charge induced switching of diode currents for signal amplification in sensing.

Optical response tuning in nanorod-on-semicontinous film systems: A computational study

NASA Astrophysics Data System (ADS)

Mokkath, Junais Habeeb

2018-01-01

Strongly confined and intense optical fields within the plasmonic metal nanocavities show outstanding potential for a wide range of functionalities in nanophotonics. Using time dependent density functional theory calculations, we investigate the optical response evolution as a function of the gap separation distances in nanorod-on-film systems comprised of a nanorod (NR) made of Al or Na on top of an Al film. Huge optical field modulations emerged in the chemically distinct Na NR - Al film system in comparison to the Al NR - Al film system, indicating the vital role of metals involved. We further study the optical response modifications by placing a conducting molecule in the gap region, finding strong spectral modulations via through-molecule electron tunneling.

Effects of Na and secondary phases on physical properties of SnS thin film after sulfurization process

NASA Astrophysics Data System (ADS)

Kawano, Yu; Kodani, Yuto; Chantana, Jakapan; Minemoto, Takashi

2016-09-01

2.48%-efficient SnS thin film solar cell is obtained under thermal evaporation method by optimizing growth temperature. The method to fabricate SnS films is limited by growth temperature, which should not be over 200 °C to prevent re-evaporation of SnS. To further enhance SnS grains, SnS films were annealed in H2S gas from 200 to 500 °C, namely sulfurization process. SnS grain size was increased with sulfurization temperature of above 400 °C however, secondary phase grains on film’s surface were observed owing to the accumulated Na, diffused from soda-lime glass substrate into the film, thus deteriorating film’s quality, implied by Urbach energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barbante, Paolo; Frezzotti, Aldo; Gibelli, Livio

The unsteady evaporation of a thin planar liquid film is studied by molecular dynamics simulations of Lennard-Jones fluid. The obtained results are compared with the predictions of a diffuse interface model in which capillary Korteweg contributions are added to hydrodynamic equations, in order to obtain a unified description of the liquid bulk, liquid-vapor interface and vapor region. Particular care has been taken in constructing a diffuse interface model matching the thermodynamic and transport properties of the Lennard-Jones fluid. The comparison of diffuse interface model and molecular dynamics results shows that, although good agreement is obtained in equilibrium conditions, remarkable deviationsmore » of diffuse interface model predictions from the reference molecular dynamics results are observed in the simulation of liquid film evaporation. It is also observed that molecular dynamics results are in good agreement with preliminary results obtained from a composite model which describes the liquid film by a standard hydrodynamic model and the vapor by the Boltzmann equation. The two mathematical model models are connected by kinetic boundary conditions assuming unit evaporation coefficient.« less

Controllable fabrication of porous free-standing polypyrrole films via a gas phase polymerization.

PubMed

Lei, Junyu; Li, Zhicheng; Lu, Xiaofeng; Wang, Wei; Bian, Xiujie; Zheng, Tian; Xue, Yanpeng; Wang, Ce

2011-12-15

A facile gas phase polymerization method has been proposed in this work to fabricate porous free-standing polypyrrole (PPy) films. In the presence of pyrrole vapor, the films are obtained in the gas/water interface spontaneously through the interface polymerization with the oxidant of FeCl(3) in the water. Both the thickness of the film and the size of the pores could be controlled by adjusting the concentrations of the oxidant and the reaction time. The as-prepared PPy films exhibited a superhydrophilic behavior due to its composition and porous structures. We have demonstrated a possible formation mechanism for the porous free-standing PPy films. This gas phase polymerization is shown to be readily scalable to prepare large area of PPy films. Copyright © 2011 Elsevier Inc. All rights reserved.

Influence of the side chain and substrate on polythiophene thin film surface, bulk, and buried interfacial structures.

PubMed

Xiao, Minyu; Jasensky, Joshua; Zhang, Xiaoxian; Li, Yaoxin; Pichan, Cayla; Lu, Xiaolin; Chen, Zhan

2016-08-10

The molecular structures of organic semiconducting thin films mediate the performance of various devices composed of such materials. To fully understand how the structures of organic semiconductors alter on substrates due to different polymer side chains and different interfacial interactions, thin films of two kinds of polythiophene derivatives with different side-chains, poly(3-hexylthiophene) (P3HT) and poly(3-potassium-6-hexanoate thiophene) (P3KHT), were deposited and compared on various surfaces. A combination of analytical tools was applied in this research: contact angle goniometry and X-ray photoelectron spectroscopy (XPS) were used to characterize substrate dielectric surfaces with varied hydrophobicity for polymer film deposition; X-ray diffraction and UV-vis spectroscopy were used to examine the polythiophene film bulk structure; sum frequency generation (SFG) vibrational spectroscopy was utilized to probe the molecular structures of polymer film surfaces in air and buried solid/solid interfaces. Both side-chain hydrophobicity and substrate hydrophobicity were found to mediate the crystallinity of the polythiophene film, as well as the orientation of the thiophene ring within the polymer backbone at the buried polymer/substrate interface and the polymer thin film surface in air. For the same type of polythiophene film deposited on different substrates, a more hydrophobic substrate surface induced thiophene ring alignment with the surface normal at both the buried interface and on the surface in air. For different films (P3HT vs. P3KHT) deposited on the same dielectric substrate, a more hydrophobic polythiophene side chain caused the thiophene ring to align more towards the surface at the buried polymer/substrate interface and on the surface in air. We believe that the polythiophene surface, bulk, and buried interfacial molecular structures all influence the hole mobility within the polythiophene film. Successful characterization of an organic conducting thin film surface, buried interfacial, and bulk structures is a first crucial step in understanding the structure-function relationship of such films in order to optimize device performance. An in-depth understanding on how the side-chain influences the interfacial and surface polymer orientation will guide the future molecular structure design of organic semiconductors.

The role of film interfaces in near-ultraviolet absorption and pulsed-laser damage in ion-beam-sputtered coatings based on HfO 2/SiO 2 thin-film pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ristau, Detlev; Papernov, S.; Kozlov, A. A.

2015-11-23

The role of thin-film interfaces in the near-ultraviolet absorption and pulsed-laser–induced damage was studied for ion-beam–sputtered and electron-beam–evaporated coatings comprised from HfO 2 and SiO 2 thin-film pairs. To separate contributions from the bulk of the film and from interfacial areas, absorption and damage-threshold measurements were performed for a one-wave (355-nm wavelength) thick, HfO 2 single-layer film and for a film containing seven narrow HfO 2 layers separated by SiO 2 layers. The seven-layer film was designed to have a total optical thickness of HfO 2 layers, equal to one wave at 355 nm and an E-field peak and averagemore » intensity similar to a single-layer HfO 2 film. Absorption in both types of films was measured using laser calorimetry and photothermal heterodyne imaging. The results showed a small contribution to total absorption from thin-film interfaces, as compared to HfO 2 film material. The relevance of obtained absorption data to coating near-ultraviolet, nanosecond-pulse laser damage was verified by measuring the damage threshold and characterizing damage morphology. The results of this study revealed a higher damage resistance in the seven-layer coating as compared to the single-layer HfO 2 film in both sputtered and evaporated coatings. Here, the results are explained through the similarity of interfacial film structure with structure formed during the co-deposition of HfO 2 and SiO 2 materials.« less

Fabrication and ferroelectric properties of highly dense lead-free piezoelectric (K0.5Na0.5)NbO3 thick films by aerosol deposition

NASA Astrophysics Data System (ADS)

Ryu, Jungho; Choi, Jong-Jin; Hahn, Byung-Dong; Park, Dong-Soo; Yoon, Woon-Ha; Kim, Ki-Hoon

2007-04-01

Lead-free piezoelectric thick films of (K0.5Na0.5)NbO3 were fabricated by aerosol-deposition method. The thickness of KNN film was 7.1μm and fully dense films were obtained. The dielectric constants ɛ3T/ɛ0 of the as-deposited and annealed films at 1kHz were 116 and 545, respectively, which are higher than any previously reported values for lead-free piezoelectric thin/thick films, either without or with heat treatment. The ferroelectric properties were improved after annealing and the maximum values of Pr=8.1μC/cm3 and Ec=100kV/cm were achieved. These values are markedly superior to those of sintered KNN ceramic counterparts.

Dielectric and piezoelectric properties of lead-free (Bi,Na)TiO3-based thin films

NASA Astrophysics Data System (ADS)

Abazari, M.; Safari, A.; Bharadwaja, S. S. N.; Trolier-McKinstry, S.

2010-02-01

Dielectric and piezoelectric properties of morphotropic phase boundary (Bi,Na)TiO3-(Bi,K)TiO3-BaTiO3 epitaxial thin films deposited on SrRuO3 coated SrTiO3 substrates were reported. Thin films of 350 nm thickness exhibited small signal dielectric permittivity and loss tangent values of 750 and 0.15, respectively, at 1 kHz. Ferroelectric hysteresis measurements indicated a remanent polarization value of 30 μC/cm2 with a coercive field of 85-100 kV/cm. The thin film transverse piezoelectric coefficient (e31,f) of these films after poling at 600 kV/cm was found to be -2.2 C/m2. The results indicate that these BNT-based thin films are a potential candidate for lead-free piezoelectric devices.

Growth of high-quality thin-film Ge single crystals by plasma-enhanced chemical vapor deposition

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Hopson, P., Jr.

1986-01-01

Thin-film Ge single crystals (approx. 10 microns) have been epitaxially grown on polished NaCl(100) substrates at 450C by using plasma-enhanced chemical vapor deposition. Films on approximately 1 sq cm and larger were separated from the NaCl by either melting the salt or by differential shear stress upon cooling to room temperature. The ordered growth of the Ge was found to be most sensitive to the initial plasma power and to the continuum flow dynamics within the carbon susceptor. The films were visually specular and exhibited a high degree of crysalline order when examined by X-ray diffraction. The films were found to be p-type with a carrier concentration of approximately 3 x 10 to the 16th power/cu cm, a resistivity of 0.11 ohm-cm, and a Hall hole mobility of 1820 sq cm/v/s at room temperature. Vacuum firing minimized the primary contaminant, Na, and corresponding lowered the carrier concentration to 4 x 10 to the 14th power/cu cm.

Evaluating and improving the performance of thin film force sensors within body and device interfaces.

PubMed

Likitlersuang, Jirapat; Leineweber, Matthew J; Andrysek, Jan

2017-10-01

Thin film force sensors are commonly used within biomechanical systems, and at the interface of the human body and medical and non-medical devices. However, limited information is available about their performance in such applications. The aims of this study were to evaluate and determine ways to improve the performance of thin film (FlexiForce) sensors at the body/device interface. Using a custom apparatus designed to load the sensors under simulated body/device conditions, two aspects were explored relating to sensor calibration and application. The findings revealed accuracy errors of 23.3±17.6% for force measurements at the body/device interface with conventional techniques of sensor calibration and application. Applying a thin rigid disc between the sensor and human body and calibrating the sensor using compliant surfaces was found to substantially reduce measurement errors to 2.9±2.0%. The use of alternative calibration and application procedures is recommended to gain acceptable measurement performance from thin film force sensors in body/device applications. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

The extent of slits at the interfaces between luting cements and enamel, dentin and alloy.

PubMed

Oilo, G

1978-01-01

Four different cements were used to assess the presence of slits at the cement/tooth or the cement/alloy interfaces using a tooth-crown model. The model consisted of ground sections of teeth and plane plates of silver/palladium alloy. The plates were fixed with bolts between two brass plates and with three different dimensions of the cement film between tooth and alloy, i.e. 50 micrometer, 100 micrometer and 200 micrometer. The tooth-alloy specimens were sectioned and the adaption of cements was studied with an indirect technique (replica) in a scanning electron microscope. The extent of slits was expressed as the length of all slits relative to the total length of the interface in each specimen. The results showed that the zinc phosphate cement and polycarboxylate cement exhibited a slight to moderate tendency to formation of slits at the interfaces. The EBA cement had a small extent of slits adjacent to thin cement films, but more slits were observed with increasing film thickness. The composite resin cement had a marked tendency to slit formation independent of the cement film thickness.

Unusual folded structures for a tethered squaraine-cholesterol derivative in Langmuir-Blodgett films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanescu, M.; Samha, H.; Perlstein, J.

2000-01-11

A squaraine-cholesterol diad, 1, which has been found to be a good gelator, has been studied in films at the air-water interface and in supported Langmuir-Blodgett films. Both experimental observations and simulations are consistent with a low-energy folded structure in which there are attractive noncovalent interactions between the squaraine chromophore and the steroid. Although different structures seem likely for 1 in both the crystal and organogels, the present studies suggest that the folded structure exists in both uncompressed and compressed films at the air-water interface and in supported LB films. In both environments the squaraine chromophore shows evidence of squaraine-squarainemore » aggregation; both J and H aggregates are indicated depending upon the conditions imposed upon the film.« less

Reduction of Electrolyte Components on a Coated Si Anode of Lithium-Ion Batteries.

PubMed

Gomez-Ballesteros, Jose L; Balbuena, Perla B

2017-07-20

Surface modification of Si anodes in Li-ion batteries by deposition of a thin alucone coating has demonstrated an effective way to help maintain a stable anode/electrolyte interface and good battery performance. In this work, we investigate the interactions and reactivity of the film with electrolyte components using ab initio molecular dynamics simulations. Adsorption of solvent molecules (ethylene carbonate, EC) and salt (LiPF 6 ) and reduction by two mechanisms depending on the Li content of the film (yielding open EC adsorbed on the film or C 2 H 4 + CO 3 2- ) take place near the film/electrolyte and film/anode interfaces. Reaction products incorporate into the structure of the film and create a new kind of solid-electrolyte interphase layer.

Reduction of Electrolyte Components on a Coated Si Anode of Lithium-Ion Batteries

DOE PAGES

Gomez-Ballesteros, Jose L.; Balbuena, Perla B.

2017-07-07

Surface modification of Si anodes in Li-ion batteries by deposition of a thin alucone coating has demonstrated an effective way to help maintain a stable anode/electrolyte interface and good battery performance. In this paper, we investigate the interactions and reactivity of the film with electrolyte components using ab initio molecular dynamics simulations. Adsorption of solvent molecules (ethylene carbonate, EC) and salt (LiPF 6), and reduction by two mechanisms depending on the Li content of the film (yielding open EC adsorbed on the film or C 2H 4 + CO 3 2-) take place near the film/electrolyte and film/anode interfaces. Finally,more » reactions products incorporate to the structure of the film and create a new kind of solid-electrolyte interphase layer.« less

Development of Network Interface Cards for TRIDAQ systems with the NaNet framework

NASA Astrophysics Data System (ADS)

Ammendola, R.; Biagioni, A.; Cretaro, P.; Di Lorenzo, S.; Fiorini, M.; Frezza, O.; Lamanna, G.; Lo Cicero, F.; Lonardo, A.; Martinelli, M.; Neri, I.; Paolucci, P. S.; Pastorelli, E.; Piandani, R.; Pontisso, L.; Rossetti, D.; Simula, F.; Sozzi, M.; Valente, P.; Vicini, P.

2017-03-01

NaNet is a framework for the development of FPGA-based PCI Express (PCIe) Network Interface Cards (NICs) with real-time data transport architecture that can be effectively employed in TRIDAQ systems. Key features of the architecture are the flexibility in the configuration of the number and kind of the I/O channels, the hardware offloading of the network protocol stack, the stream processing capability, and the zero-copy CPU and GPU Remote Direct Memory Access (RDMA). Three NIC designs have been developed with the NaNet framework: NaNet-1 and NaNet-10 for the CERN NA62 low level trigger and NaNet3 for the KM3NeT-IT underwater neutrino telescope DAQ system. We will focus our description on the NaNet-10 design, as it is the most complete of the three in terms of capabilities and integrated IPs of the framework.

Surface and interface of epitaxial CdTe film on CdS buffered van der Waals mica substrate

NASA Astrophysics Data System (ADS)

Yang, Y.-B.; Seewald, L.; Mohanty, Dibyajyoti; Wang, Y.; Zhang, L. H.; Kisslinger, K.; Xie, Weiyu; Shi, J.; Bhat, I.; Zhang, Shengbai; Lu, T.-M.; Wang, G.-C.

2017-08-01

Single crystal CdTe films are desirable for optoelectronic device applications. An important strategy of creating films with high crystallinity is through epitaxial growth on a proper single crystal substrate. We report the metalorganic chemical vapor deposition of epitaxial CdTe films on the CdS/mica substrate. The epitaxial CdS film was grown on a mica surface by thermal evaporation. Due to the weak van der Waals forces, epitaxy is achieved despite the very large interface lattice mismatch between CdS and mica (∼21-55%). The surface morphology of mica, CdS and CdTe were quantified by atomic force microscopy. The near surface structures, orientations and texture of CdTe and CdS films were characterized by the unique reflection high-energy electron diffraction surface pole figure technique. The interfaces of CdTe and CdS films and mica were characterized by X-ray pole figure technique and transmission electron microscopy. The out-of-plane and in-plane epitaxy of the heteroepitaxial films stack are determined to be CdTe(111)//CdS(0001)//mica(001) and [1 bar2 1 bar]CdTe//[ 1 bar100]CdS//[010]mica, respectively. The measured photoluminescence (PL), time resolved PL, photoresponse, and Hall mobility of the CdTe/CdS/mica indicate quality films. The use of van der Waals surface to grow epitaxial CdTe/CdS films offers an alternative strategy towards infrared imaging and solar cell applications.

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep

The interaction of radiation with materials controls the performance, reliability, and safety of many structures in nuclear power systems. Revolutionary improvements in radiation damage resistance may be attainable if methods can be found to manipulate interface properties to give optimal interface stability and point defect recombination capability. To understand how variations in interface properties such as misfit dislocation density and local chemistry affect radiation-induced defect absorption and recombination, a model system of metallic Cr xV 1-x (0 ≤ x ≤ 1) epitaxial films deposited on MgO(001) single crystal substrates has been explored in this paper. By controlling film composition, themore » lattice mismatch between the film and MgO is adjusted to vary the misfit dislocation density at the metal/oxide interface. The stability of these interfaces under various irradiation conditions is studied experimentally and theoretically. The results indicate that, unlike at metal/metal interfaces, the misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry and the location of the misfit dislocation extra half-plane (in the metal or the oxide) drive radiation-induced defect behavior. Finally, together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials for next-generation nuclear power plants.« less

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE PAGES

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep; ...

2017-04-24

The interaction of radiation with materials controls the performance, reliability, and safety of many structures in nuclear power systems. Revolutionary improvements in radiation damage resistance may be attainable if methods can be found to manipulate interface properties to give optimal interface stability and point defect recombination capability. To understand how variations in interface properties such as misfit dislocation density and local chemistry affect radiation-induced defect absorption and recombination, a model system of metallic Cr xV 1-x (0 ≤ x ≤ 1) epitaxial films deposited on MgO(001) single crystal substrates has been explored in this paper. By controlling film composition, themore » lattice mismatch between the film and MgO is adjusted to vary the misfit dislocation density at the metal/oxide interface. The stability of these interfaces under various irradiation conditions is studied experimentally and theoretically. The results indicate that, unlike at metal/metal interfaces, the misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry and the location of the misfit dislocation extra half-plane (in the metal or the oxide) drive radiation-induced defect behavior. Finally, together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials for next-generation nuclear power plants.« less

Influence of gold species (AuCl4(-) and AuCl2(-)) on self-assembly of PS-b-P2VP in solutions and morphology of composite thin films fabricated at the air/liquid interfaces.

PubMed

Zhao, Xingjuan; Wang, Qian; Zhang, Xiaokai; Lee, Yong-Ill; Liu, Hong-Guo

2016-01-21

Composite thin films doped with Au species were fabricated at an air/liquid interface via a series of steps, including the mass transfer of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) across the liquid/liquid interface between a DMF/CHCl3 solution and an aqueous solution containing either AuCl4(-) or AuCl2(-), self-assembly of PS-b-P2VP in a mixed DMF-water solution, and adsorption and further self-organization of the formed aggregates at the air/liquid interface. This is a new approach for fabricating composite polymer films and can be completed within a very short time. AuCl4(-) and AuCl2(-) ions were found to significantly influence the self-assembly behavior of the block copolymer and the morphologies of the composite films, leading to the formation of nanowire arrays and a foam structure at the air/liquid interface, respectively, which originated from rod-like micelles and microcapsules that had formed in the respective solutions. The effect of the metal complex was analyzed based on the packing parameters of the amphiphilic polymer molecules in different microenvironments and the interactions between the pyridine groups and the metal chloride anions. In addition, these composite thin films exhibited stable and durable performance as heterogeneous catalysts for the hydrogenation of nitroaromatics in aqueous solutions.

Structural Evaluation of 5,5'-Bis(naphth-2-yl)-2,2'-bithiophene in Organic Field-Effect Transistors with n-Octadecyltrichlorosilane Coated SiO2 Gate Dielectric.

PubMed

Lauritzen, Andreas E; Torkkeli, Mika; Bikondoa, Oier; Linnet, Jes; Tavares, Luciana; Kjelstrup-Hansen, Jakob; Knaapila, Matti

2018-05-25

We report on the structure and morphology of 5,5'-bis(naphth-2-yl)-2,2'-bithiophene (NaT2) films in bottom-contact organic field-effect transistors (OFETs) with octadecyltrichlorosilane (OTS) coated SiO 2 gate dielectric, characterized by atomic force microscopy (AFM), grazing-incidence X-ray diffraction (GIXRD), and electrical transport measurements. Three types of devices were investigated with the NaT2 thin-film deposited either on (1) pristine SiO 2 (corresponding to higher surface energy, 47 mJ/m 2 ) or on OTS deposited on SiO 2 under (2) anhydrous or (3) humid conditions (corresponding to lower surface energies, 20-25 mJ/m 2 ). NaT2 films grown on pristine SiO 2 form nearly featureless three-dimensional islands. NaT2 films grown on OTS/SiO 2 deposited under anhydrous conditions form staggered pyramid islands where the interlayer spacing corresponds to the size of the NaT2 unit cell. At the same time, the grain size measured by AFM increases from hundreds of nanometers to micrometers and the crystal size measured by GIXRD from 30 nm to more than 100 nm. NaT2 on OTS/SiO 2 deposited under humid conditions also promotes staggered pyramids but with smaller crystals 30-80 nm. The NaT2 unit cell parameters in OFETs differ 1-2% from those in bulk. Carrier mobilities tend to be higher for NaT2 layers on SiO 2 (2-3 × 10 -4 cm 2 /(V s)) compared to NaT2 on OTS (2 × 10 -5 -1 × 10 -4 cm 2 /(V s)). An applied voltage does not influence the unit cell parameters when probed by GIXRD in operando.

Electronic properties of the interface between hexadecafluoro copper phthalocyanine and unsubstituted copper phthalocyanine films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komolov, A. S., E-mail: akomolov07@ya.ru; Lazneva, E. F.; Pshenichnyuk, S. A.

2013-07-15

The formation of an interface during the deposition of unsubstituted copper phthalocyanine (CuPc) films on the surface of hexadecafluoro copper phthalocyanine (F{sub 16}-CuPc) films is studied. An incident low-energy electron beam with energies from 0 to 25 eV is used to test the surface under study according to the very-low-energy electron-diffraction technique (VLEED) in the mode of total current spectroscopy. For F{sub 16}-CuPc films, the structure of the maxima in the total current spectra and its main differences from the structure of the maxima for the CuPc film are determined in the energy range from 5 to 15 eV abovemore » the Fermi level. The differences in the structure of vacant electron orbitals for CuPc and F{sub 16}-CuPc are also revealed using density functional theory calculations. As a result of an analysis of variations in the intensities of the total current spectra of the CuPc and F{sub 16}-CuPc films, it is assumed that an intermediate layer up to 1 nm thick appears during the formation of an interface between these films, which is characterized by a spread of the features in the total current spectrum. The height, width, and change in the work function are determined for the studied F{sub 16}-CuPc/NuPc interface barrier. A decrease in the level of vacuum by 0.7 eV occurs in the boundary region, which corresponds to electron density transfer from the CuPc film toward the F{sub 16}-CuPc substrate.« less

Investigating the electronic properties of Al2O3/Cu(In,Ga)Se2 interface

NASA Astrophysics Data System (ADS)

Kotipalli, R.; Vermang, B.; Joel, J.; Rajkumar, R.; Edoff, M.; Flandre, D.

2015-10-01

Atomic layer deposited (ALD) Al2O3 films on Cu(In,Ga)Se2 (CIGS) surfaces have been demonstrated to exhibit excellent surface passivation properties, which is advantageous in reducing recombination losses at the rear metal contact of CIGS thin-film solar cells. Here, we report, for the first time, experimentally extracted electronic parameters, i.e. fixed charge density (Qf) and interface-trap charge density (Dit), for as-deposited (AD) and post-deposition annealed (PDA) ALD Al2O3 films on CIGS surfaces using capacitance-voltage (C-V) and conductance-frequency (G-f) measurements. These results indicate that the AD films exhibit positive fixed charges Qf (approximately 1012 cm-2), whereas the PDA films exhibit a very high density of negative fixed charges Qf (approximately 1013 cm-2). The extracted Dit values, which reflect the extent of chemical passivation, were found to be in a similar range of order (approximately 1012 cm-2 eV-1) for both AD and PDA samples. The high density of negative Qf in the bulk of the PDA Al2O3 film exerts a strong Coulomb repulsive force on the underlying CIGS minority carriers (ns), preventing them to recombine at the CIGS/Al2O3 interface. Using experimentally extracted Qf and Dit values, SCAPS simulation results showed that the surface concentration of minority carriers (ns) in the PDA films was approximately eight-orders of magnitude lower than in the AD films. The electrical characterization and estimations presented in this letter construct a comprehensive picture of the interfacial physics involved at the Al2O3/CIGS interface.

Optical models for radio-frequency-magnetron reactively sputtered AlN films

NASA Astrophysics Data System (ADS)

Easwarakhanthan, T.; Assouar, M. B.; Pigeat, P.; Alnot, P.

2005-10-01

The optical properties of aluminum nitrate (AlN) films reactively sputtered on Si substrates using radio-frequency (rf) magnetron have been studied in this work from multiwavelength spectroscopic ellipsometry (SE) measurements performed over the 290-615 nm wavelength range. The SE modeling carried out with care to adhere as much to the ellipsometric fitting qualities is also backed up with atomic force microscopy and x-ray-diffraction measurements taken on these films thus grown to nominal thicknesses from 40 to 150 nm under the same optimized experimental conditions. It follows that the model describing the optical properties of the thicker AlN films should consist at least in three layers on the Si substrate: an almost roughnessless smooth surface overlayer that is presumed essentially of Al2O3, a bulk AlN layer, and an AlN interface layer that has a refractive index dispersion falling in the range from 2.04 [312 nm] to 1.91 [615 nm] on the average and is fairly distinguishable from the slightly higher bulk layer index which drops correspondingly from 2.12 to 1.99. These index values imply that, beneath the partly or mostly oxidized surface AlN layer, the films comprise a polycrystalline-structured bulk AlN layer above a less-microstructurally-ordered interface layer that extends over 40-55 nm from the substrate among thicker films. This ellipsometric evidence indicating the existence of the interface layer is consistent with those interface layers confirmed through electron microscopy in some previous works. However, the ellipsometrically insufficient thinner AlN films may be only modeled with the surface layer and an AlN layer. The film surface oxide layer thickness varies between 5 and 15 nm among samples. The refractive index dispersions, the layer thicknesses, and the lateral thickness variation of the films are given and discussed regarding the optical constitution of these films and the ellipsometric validity of these parameters.

Exchange coupled CoPd/TbCo magneto-optic storage films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gambino, R.J.; Ruf, R.R.; Rishi, R.

1989-09-01

Films of CoPd with weak perpendicular anisotropy are shown to exchange couple to square loop TbCo films on both the Tb and Co sides of compensation. The exchange is sensitive to reactive impurities at the interface and is broken under conditions that produce as little as one monolayer of paramagnetic compound. Even when the coupling at the interface is strong, the authors show that only a limited thickness of the CoPd layer is spin oriented perpendicular.

International Conference on Solid Films and Surfaces (2nd) (ICSFS-2), Programn and Abstracts Held at College Park, Maryland on 8-11 June 1981.

DTIC Science & Technology

1981-06-01

film recrystal- lization and the changing of their optical properties. The data of ther- mal treatment of the Zinc Sulphide and Magnium films in...11. J. KtEUZt 2:00 Surface Potentials of Benzene Derivative Monolayers and Submono- layers at the Mercury /Nitrogen Interface. B. J. KINZIG 2:20 Alkoxy...Potentials of Benzene Derivative Monolayers and Submonolayers at the Mercury /Nitrogen Interface by • B. J. Kinzig Naval Research Laboratory Optical

Flat-lying semiconductor-insulator interfacial layer in DNTT thin films.

PubMed

Jung, Min-Cherl; Leyden, Matthew R; Nikiforov, Gueorgui O; Lee, Michael V; Lee, Han-Koo; Shin, Tae Joo; Takimiya, Kazuo; Qi, Yabing

2015-01-28

The molecular order of organic semiconductors at the gate dielectric is the most critical factor determining carrier mobility in thin film transistors since the conducting channel forms at the dielectric interface. Despite its fundamental importance, this semiconductor-insulator interface is not well understood, primarily because it is buried within the device. We fabricated dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) thin film transistors by thermal evaporation in vacuum onto substrates held at different temperatures and systematically correlated the extracted charge mobility to the crystal grain size and crystal orientation. As a result, we identify a molecular layer of flat-lying DNTT molecules at the semiconductor-insulator interface. It is likely that such a layer might form in other material systems as well, and could be one of the factors reducing charge transport. Controlling this interfacial flat-lying layer may raise the ultimate possible device performance for thin film devices.

New method for measuring the laser-induced damage threshold of optical thin film

NASA Astrophysics Data System (ADS)

Su, Jun-hong; Wang, Hong; Xi, Ying-xue

2012-10-01

The laser-induced damage threshold (LIDT) of thin film means that the thin film can withstand a maximum intensity of laser radiation. The film will be damaged when the irradiation under high laser intensity is greater than the value of LIDT. In this paper, an experimental platform with measurement operator interfaces and control procedures in the VB circumstance is built according to ISO11254-1. In order to obtain more accurate results than that with manual measurement, in the software system, a hardware device can be controlled by control widget on the operator interfaces. According to the sample characteristic, critical parameters of the LIDT measurement system such as spot diameter, damage threshold region, and critical damage pixel number are set up on the man-machine conversation interface, which could realize intelligent measurements of the LIDT. According to experimental data, the LIDT is obtained by fitting damage curve automatically.

Novel Monitoring Techniques for Characterizing Frictional Interfaces in the Laboratory

PubMed Central

Selvadurai, Paul A.; Glaser, Steven D.

2015-01-01

A pressure-sensitive film was used to characterize the asperity contacts along a polymethyl methacrylate (PMMA) interface in the laboratory. The film has structural health monitoring (SHM) applications for flanges and other precision fittings and train rail condition monitoring. To calibrate the film, simple spherical indentation tests were performed and validated against a finite element model (FEM) to compare normal stress profiles. Experimental measurements of the normal stress profiles were within −7.7% to 6.6% of the numerical calculations between 12 and 50 MPa asperity normal stress. The film also possessed the capability of quantifying surface roughness, an important parameter when examining wear and attrition in SHM applications. A high definition video camera supplied data for photometric analysis (i.e., the measure of visible light) of asperities along the PMMA-PMMA interface in a direct shear configuration, taking advantage of the transparent nature of the sample material. Normal stress over individual asperities, calculated with the pressure-sensitive film, was compared to the light intensity transmitted through the interface. We found that the luminous intensity transmitted through individual asperities linearly increased 0.05643 ± 0.0012 candelas for an increase of 1 MPa in normal stress between normal stresses ranging from 23 to 33 MPa. PMID:25923930

Large-scale recrystallization of the S-layer of Bacillus coagulans E38-66 at the air/water interface and on lipid films.

PubMed Central

Pum, D; Weinhandl, M; Hödl, C; Sleytr, U B

1993-01-01

S-layer protein isolated from Bacillus coagulans E38-66 could be recrystallized into large-scale coherent monolayers at an air/water interface and on phospholipid films spread on a Langmuir-Blodgett trough. Because of the asymmetry in the physiochemical surface properties of the S-layer protein, the subunits were associated with their more hydrophobic outer face with the air/water interface and oriented with their negatively charged inner face to the zwitterionic head groups of the dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylethanolamine (DPPE) monolayer films. The dynamic crystal growth at both types of interfaces was first initiated at several distant nucleation points. The individual monocrystalline areas grew isotropically in all directions until the front edge of neighboring crystals was met. The recrystallized S-layer protein and the S-layer-DPPE layer could be chemically cross-linked from the subphase with glutaraldehyde. Images PMID:8478338

Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

PubMed

Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

2016-05-11

We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors.

Effects of van der Waals forces and salt ions on the growth of water films on ice and the detachment of CO2 bubbles

NASA Astrophysics Data System (ADS)

Thiyam, P.; Lima, E. R. A.; Malyi, O. I.; Parsons, D. F.; Buhmann, S. Y.; Persson, C.; Boström, M.

2016-02-01

We study the effect of salts on the thickness of wetting films on melting ice and interactions acting on CO2 bubble near ice-water and vapor-water interfaces. Governing mechanisms are the Lifshitz and the double-layer interactions in the respective three-layer geometries. We demonstrate that the latter depend on the Casimir-Polder interaction of the salt ions dissolved in water with the respective ice, vapor and CO2 interfaces, as calculated using different models for their effective polarizability in water. Significant variation in the predicted thickness of the equilibrium water film is observed for different salt ions and when using different models for the ions' polarizabilities. We find that CO2 bubbles are attracted towards the ice-water interface and repelled from the vapor-water interface.

Interaction of L-Phenylalanine with a Phospholipid Monolayer at the Water-Air Interface.

PubMed

Griffith, Elizabeth C; Perkins, Russell J; Telesford, Dana-Marie; Adams, Ellen M; Cwiklik, Lukasz; Allen, Heather C; Roeselová, Martina; Vaida, Veronica

2015-07-23

The interaction of L-phenylalanine with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air-water interface was explored using a combination of experimental techniques and molecular dynamics (MD) simulations. By means of Langmuir trough methods and Brewster angle microscopy, L-phenylalanine was shown to significantly alter the interfacial tension and the surface domain morphology of the DPPC film. In addition, confocal microscopy was used to explore the aggregation state of L-phenylalanine in the bulk aqueous phase. Finally, MD simulations were performed to gain molecular-level information on the interactions of L-phenylalanine and DPPC at the interface. Taken together, these results show that L-phenylalanine intercalates into a DPPC film at the air-water interface, thereby affecting the surface tension, phase morphology, and ordering of the DPPC film. The results are discussed in the context of biological systems and the mechanism of diseases such as phenylketonuria.

Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation

NASA Astrophysics Data System (ADS)

Wang, Jin Jimmy

This thesis examines melting in superheated silicon films in contact with SiO2 under pulsed laser irradiation. An excimer-laser pulse was employed to induce heating of the film by irradiating the film through the transparent fused-quartz substrate such that most of the beam energy was deposited near the bottom Si-SiO2 interface. Melting dynamics were probed via in situ transient reflectance measurements. The temperature profile was estimated computationally by incorporating temperature- and phase-dependent physical parameters and the time-dependent intensity profile of the incident excimer-laser beam obtained from the experiments. The results indicate that a significant degree of superheating occurred in the subsurface region of the film. Surface-initiated melting was observed in spite of the internal heating scheme, which resulted in the film being substantially hotter at and near the bottom Si-SiO2 interface. By considering that the surface melts at the equilibrium melting point, the solid-phase-only heat-flow analysis estimates that the bottom Si-SiO2 interface can be superheated by at least 220 K during excimer-laser irradiation. It was found that at higher laser fluences (i.e., at higher temperatures), melting can be triggered internally. At heating rates of 1010 K/s, melting was observed to initiate at or near the (100)-oriented Si-SiO2 interface at temperatures estimated to be over 300 K above the equilibrium melting point. Based on theoretical considerations, it was deduced that melting in the superheated solid initiated via a nucleation and growth process. Nucleation rates were estimated from the experimental data using Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Interpretation of the results using classical nucleation theory suggests that nucleation of the liquid phase occurred via the heterogeneous mechanism along the Si-SiO2 interface.

Dose in bone and tissue near bone-tissue interface from electron beam.

PubMed

Shiu, A S; Hogstrom, K R

1991-08-01

This work has quantitatively studied the variation of dose both within bone and in unit density tissue near bone-tissue interfaces. Dose upstream of a bone-tissue interface is increased because of an increase in the backscattered electrons from the bone. The magnitude of this effect was measured using a thin parallel-plate ionization chamber upstream of a polymethyl methacrylate (PMMA)-hard bone interface. The electron backscatter factor (EBF) increased rapidly with bone thickness until a full EBF was achieved. This occurred at approximately 3.5 mm at 2 MeV and 6 mm at 13.1 MeV. The full EBF at the interface ranged from approximately 1.018 at 13.1 MeV to 1.05 at 2 MeV. It was also observed that the EBF had a dependence on the energy spectrum at the interface. The penetration of the backscattered electrons in the upstream direction of PMMA was also measured. The dose penetration fell off rapidly in the upstream direction of the interface. Dose enhancement to unit density tissue in bone was measured for an electron beam by placing thermoluminescent dosimeters (TLDs) in a PMMA-bone-PMMA phantom. The maximum dose enhancement in bone was approximately 7% of the maximum dose in water. However, the pencil-beam algorithm of Hogstrom et al. predicted an increase of only 1%, primarily owing to the inverse-square correction. Film was also used to measure the dose enhancement in bone. The film plane was aligned either perpendicular or parallel to the central axis of the beam. The film data indicated that the maximum dose enhancement in bone was approximately 8% for the former film alignment (which was similarly predicted by the TLD measurements) and 13% for the latter film alignment. These results confirm that the X ray film is not suitable to be irritated "edge on" in an inhomogeneous phantom without making perturbation corrections resulting from the film acting as a long narrow inhomogeneous cavity within the bone. In addition, the results give the radiotherapist a basis for clinical judgment when electron beams are used to treat lesions behind bone or near bony structures. We feel these data enhance the ability to recognize the shortcomings of the current dose calculation algorithm used clinically.

Demonstrating the feasibility of monitoring the molecular-level structures of moving polymer/silane interfaces during silane diffusion using SFG.

PubMed

Chen, Chunyan; Wang, Jie; Loch, Cheryl L; Ahn, Dongchan; Chen, Zhan

2004-02-04

In this paper, the feasibility of monitoring molecular structures at a moving polymer/liquid interface by sum frequency generation (SFG) vibrational spectroscopy has been demonstrated. N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (AATM, NH2(CH2)2NH(CH2)3Si(OCH3)3) has been brought into contact with a deuterated poly(methyl methacrylate) (d-PMMA) film, and the interfacial silane structure has been monitored using SFG. Upon initial contact, the SFG spectra can be detected, but as time progresses, the spectral intensity changes and finally disappears. Additional experiments indicate that these silane molecules can diffuse into the polymer film and the detected SFG signals are actually from the moving polymer/silane interface. Our results show that the molecular order of the polymer/silane interface exists during the entire diffusion process and is lost when the silane molecules traverse through the thickness of the d-PMMA film. The loss of the SFG signal is due to the formation of a new disordered substrate/silane interface, which contributes no detectable SFG signal. The kinetics of the diffusion of the silane into the polymer have been deduced from the time-dependent SFG signals detected from the AATM molecules as they diffuse through polymer films of different thickness.

Capillary wave theory of adsorbed liquid films and the structure of the liquid-vapor interface

NASA Astrophysics Data System (ADS)

MacDowell, Luis G.

2017-08-01

In this paper we try to work out in detail the implications of a microscopic theory for capillary waves under the assumption that the density is given along lines normal to the interface. Within this approximation, which may be justified in terms of symmetry arguments, the Fisk-Widom scaling of the density profile holds for frozen realizations of the interface profile. Upon thermal averaging of capillary wave fluctuations, the resulting density profile yields results consistent with renormalization group calculations in the one-loop approximation. The thermal average over capillary waves may be expressed in terms of a modified convolution approximation where normals to the interface are Gaussian distributed. In the absence of an external field we show that the phenomenological density profile applied to the square-gradient free energy functional recovers the capillary wave Hamiltonian exactly. We extend the theory to the case of liquid films adsorbed on a substrate. For systems with short-range forces, we recover an effective interface Hamiltonian with a film height dependent surface tension that stems from the distortion of the liquid-vapor interface by the substrate, in agreement with the Fisher-Jin theory of short-range wetting. In the presence of long-range interactions, the surface tension picks up an explicit dependence on the external field and recovers the wave vector dependent logarithmic contribution observed by Napiorkowski and Dietrich. Using an error function for the intrinsic density profile, we obtain closed expressions for the surface tension and the interface width. We show the external field contribution to the surface tension may be given in terms of the film's disjoining pressure. From literature values of the Hamaker constant, it is found that the fluid-substrate forces may be able to double the surface tension for films in the nanometer range. The film height dependence of the surface tension described here is in full agreement with results of the capillary wave spectrum obtained recently in computer simulations, and the predicted translation mode of surface fluctuations reproduces to linear order in field strength an exact solution of the density correlation function for the Landau-Ginzburg-Wilson Hamiltonian in an external field.

Thin film silicon by a microwave plasma deposition technique: Growth and devices, and, interface effects in amorphous silicon/crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Jagannathan, Basanth

Thin film silicon (Si) was deposited by a microwave plasma CVD technique, employing double dilution of silane, for the growth of low hydrogen content Si films with a controllable microstructure on amorphous substrates at low temperatures (<400sp°C). The double dilution was achieved by using a Ar (He) carrier for silane and its subsequent dilution by Hsb2. Structural and electrical properties of the films have been investigated over a wide growth space (temperature, power, pressure and dilution). Amorphous Si films deposited by silane diluted in He showed a compact nature and a hydrogen content of ˜8 at.% with a photo/dark conductivity ratio of 10sp4. Thin film transistors (W/L = 500/25) fabricated on these films, showed an on/off ratio of ˜10sp6 and a low threshold voltage of 2.92 volts. Microcrystalline Si films with a high crystalline content (˜80%) were also prepared by this technique. Such films showed a dark conductivity ˜10sp{-6} S/cm, with a conduction activation energy of 0.49 eV. Film growth and properties have been compared for deposition in Ar and He carrier systems and growth models have been proposed. Low temperature junction formation by undoped thin film silicon was examined through a thin film silicon/p-type crystalline silicon heterojunctions. The thin film silicon layers were deposited by rf glow discharge, dc magnetron sputtering and microwave plasma CVD. The hetero-interface was identified by current transport analysis and high frequency capacitance methods as the key parameter controlling the photovoltaic (PV) response. The effect of the interface on the device properties (PV, junction, and carrier transport) was examined with respect to modifications created by chemical treatment, type of plasma species, their energy and film microstructure interacting with the substrate. Thermally stimulated capacitance was used to determine the interfacial trap parameters. Plasma deposition of thin film silicon on chemically clean c-Si created electron trapping sites while hole traps were seen when a thin oxide was present at the interface. Under optimized conditions, a 10.6% efficient cell (11.5% with SiOsb2 A/R) with an open circuit voltage of 0.55 volts and a short circuit current density of 30 mA/cmsp2 was fabricated.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

2001-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J.

1998-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, H.J.; Stoner, R.J.

1998-05-05

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects. 32 figs.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

2002-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Optical stress generator and detector

DOEpatents

Maris, Humphrey J.; Stoner, Robert J

1999-01-01

Disclosed is a system for the characterization of thin films and interfaces between thin films through measurements of their mechanical and thermal properties. In the system light is absorbed in a thin film or in a structure made up of several thin films, and the change in optical transmission or reflection is measured and analyzed. The change in reflection or transmission is used to give information about the ultrasonic waves that are produced in the structure. The information that is obtained from the use of the measurement methods and apparatus of this invention can include: (a) a determination of the thickness of thin films with a speed and accuracy that is improved compared to earlier methods; (b) a determination of the thermal, elastic, and optical properties of thin films; (c) a determination of the stress in thin films; and (d) a characterization of the properties of interfaces, including the presence of roughness and defects.

Magnetic properties influenced by interfaces in ultrathin Co/Ge(1 0 0) and Co/Ge(1 1 1) films

NASA Astrophysics Data System (ADS)

Tsay, J. S.; Yao, Y. D.; Cheng, W. C.; Tseng, T. K.; Wang, K. C.; Yang, C. S.

2003-10-01

Magnetic properties influenced by interfaces in ultrathin Co/Ge(1 0 0) and Co/Ge(1 1 1) films with thickness below 28 monolayers (ML) have been studied using the surface magneto-optic Kerr effect (SMOKE) technique. In both systems, the nonferromagnetic layer, as an interface between Co and Ge, plays an important role during annealing. In general, ultrathin Co films with fixed total thickness but fabricated at different temperatures on the same substrate, their Kerr hysteresis loops disappear roughly at the same temperature. This suggests that the thickness of the interfacial layer could inversely prevent the diffusion between Co and Ge substrate. From the annealing studies for both systems with total film thickness of 28 monolayers, we have found that Kerr signal disappears at 375 K for Co/Ge(1 1 1) and 425 K for Co/Ge(1 0 0) films. This suggests that Co/Ge(1 1 1) films possess a lower thermal stability than that of the Co/Ge(1 0 0) films. Our experimental data could be explained by different interfacial condition between Ge(1 0 0) and Ge(1 1 1), the different onset of interdiffusion, and the surface structure condition of Ge(1 0 0) and Ge(1 1 1).

Collection of Light From an Optical Fiber With a Numerical Aperture Greater Than One

NASA Technical Reports Server (NTRS)

Egalon, Claudio O. (Inventor); Rogowski, Robert S. (Inventor)

1996-01-01

In an optical fiber having NA greater than 1, light may be internally reflected when it strikes the fiber end at a fiber-air interface. This problem may be overcome by modification of the fiber by reverse tapering the core. Light is redirected by the taper to strike the interface at an angle closer to normal. This allows light to exit the fiber end that would by internally reflected in an untapered fiber of NA greater than 1. The novelty of the present invention lies in the tapering of the fiber core for increased through transmission of light. Prior art devices have made use of fiber tapers to achieve mode control or fiber coupling. The problem of internal reflection has not been addressed as it is one that is not as important in fibers having NA less than 1, which are more common. In chemical sensing it is advantageous to make use of fibers having higher NA due to an increased sensitivity. However the advantages in sensitivity are diminished due to the loss of signal at the fiber-air interface. The present invention overcomes the problem of loss at the interface, thus facilitating the use of high NA fibers for chemical sensing.

Measurement of liquid film in microchannels using a laser focus displacement meter

NASA Astrophysics Data System (ADS)

Hazuku, Tatsuya; Fukamachi, Norihiro; Takamasa, Tomoji; Hibiki, Takashi; Ishii, Mamoru

2005-06-01

This paper presents a new method for measuring the interfacial displacement of a liquid film in microchannels using a laser focus displacement meter (LFD). The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in microchannels and minichannels. To prevent the tube wall signal from disturbing that of the gas liquid interface, a fluorocarbon tube with a water box was used; the refraction index of this device is the same as that for water. With this method, accurate instantaneous measurements of the interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement by using the measured displacement in a fluorocarbon tube of 25 μm to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 mm and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with the real displacement to within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 μm at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 mm and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film of less than 1 μm in thickness in the slug and annular flow regimes.

SILAR deposited Bi2S3 thin film towards electrochemical supercapacitor

NASA Astrophysics Data System (ADS)

Raut, Shrikant S.; Dhobale, Jyotsna A.; Sankapal, Babasaheb R.

2017-03-01

Bi2S3 thin film electrode has been synthesized by simple and low cost successive ionic layer adsorption and reaction (SILAR) method on stainless steel (SS) substrate at room temperature. The formation of interconnected nanoparticles with nanoporous surface morphology has been achieved and which is favourable to the supercapacitor applications. Electrochemical supercapacitive performance of Bi2S3 thin film electrode has been performed through cyclic voltammetry, charge-discharge and stability studies in aqueous Na2SO4 electrolyte. The Bi2S3 thin film electrode exhibits the specific capacitance of 289 Fg-1 at 5 mVs-1 scan rate in 1 M Na2SO4 electrolyte.

Room temperature ppb level Cl2 sensing using sulphonated copper phthalocyanine films.

PubMed

Kumar, Arvind; Singh, A; Debnath, A K; Samanta, S; Aswal, D K; Gupta, S K; Yakhmi, J V

2010-09-15

We present room temperature chemiresistive gas sensing characteristics of drop casted sulphonated copper phthalocyanine (CuTsPc) films. It has been demonstrated that these films are highly selective to Cl(2) and the sensitivity in the 5-2000 ppb range varies linearly between 65 and 625%. However, for concentrations >or=2000 ppb, the response becomes irreversible, which is found to be due to the chemical bond formation between Cl(2) and SO(3)Na group of CuTsPc films. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) data confirms the oxidation of SO(3)Na group by Cl(2) gas. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Controllable Electrical Contact Resistance between Cu and Oriented-Bi2Te3 Film via Interface Tuning.

PubMed

Kong, Xixia; Zhu, Wei; Cao, Lili; Peng, Yuncheng; Shen, Shengfei; Deng, Yuan

2017-08-02

The contact resistance between metals and semiconductors has become critical for the design of thin-film thermoelectric devices with their continuous miniaturization. Herein, we report a novel interface tuning method to regulate the contact resistance at the Bi 2 Te 3 -Cu interface, and three Bi 2 Te 3 films with different oriented microstructures are obtained. The lowest contact resistivity (∼10 -7 Ω cm 2 ) is observed between highly (00l) oriented Bi 2 Te 3 and Cu film, nearly an order of magnitude lower than other orientations. This significant decrease of contact resistivity is attributed to the denser film connections, lower lattice misfit, larger effective conducting contact area, and smaller width of the surface depletion region. Meanwhile, our results show that the reduction of contact resistance has little dependence on the interfacial diffusion based on the little change in contact resistivity after the introduction of an effective Ti barrier layer. Our work provides a new idea for the mitigation of contact resistivity in thin-film thermoelectric devices and also gives certain guidance for the size design of the next-level miniaturized devices.

Depth-resolved magnetic and structural analysis of relaxing epitaxial Sr 2 CrReO 6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucy, J. M.; Hauser, A. J.; Liu, Y.

2015-03-01

Structural relaxation in a Sr2CrReO6 epitaxial film, which exhibits strong spin-orbit coupling, leads to depth-dependent magnetism. We combine two depth-resolved synchrotron x-ray techniques, two-dimensional reciprocal space mapping and x-ray magnetic circular dichroism, to quantitatively determine this effect. An 800 nm thick film of Sr2CrReO6, grown with tensile epitaxial strain on SrCr0:5Nb0:5O3(225 nm)/LSAT, relaxes away from the Sr2CrReO6/SrCr0:5Nb0:5O3 interface to its bulk lattice parameters, with much of the film being fully relaxed. Grazing incidence xray diffraction measurements of the film elucidate the in-plane strain relaxation near the film- substrate interface while depth-resolved x-ray magnetic circular dichroism at the Re L edgemore » reveals the magnetic contributions of the Re site. The smooth relaxation of the film near the interface correlates with changes in the magnetic anisotropy. This provides a systematic and powerful way to probe the depth-varying structural and magnetic properties of a complex oxide with synchrotronsource x-ray techniques.« less

Nanoscale strengthening mechanisms in metallic thin film systems

NASA Astrophysics Data System (ADS)

Schoeppner, Rachel Lynn

Nano-scale strengthening mechanisms for thin films were investigated for systems governed by two different strengthening techniques: nano-laminate strengthening and oxide dispersion strengthening. Films were tested under elevated temperature conditions to investigate changes in deformation mechanisms at different operating temperatures, and the structural stability. Both systems exhibit remarkable stability after annealing and thus long-term reliability. Nano-scale metallic multilayers with smaller layer thicknesses show a greater relative resistance to decreasing strength at higher temperature testing conditions than those with larger layer thicknesses. This is seen in both Cu/Ni/Nb multilayers as well as a similar tri-component bi-layer system (Cu-Ni/Nb), which removed the coherent interface from the film. Both nanoindentation and micro-pillar compression tests investigated the strain-hardening ability of these two systems to determine what role the coherent interface plays in this mechanism. Tri-layer films showed a higher strain-hardening ability as the layer thickness decreased and a higher strain-hardening exponent than the bi-layer system: verifying the presence of a coherent interface increases the strain-hardening ability of these multilayer systems. Both systems exhibited hardening of the room temperature strength after annealing, suggesting a change in microstructure has occurred, unlike that seen in other multilayer systems. Oxide dispersion strengthened Au films showed a marked increase in hardness and wear resistance with the addition of ZnO particles. The threshold for stress-induced grain-refinement as opposed to grain growth is seen at concentrations of at least 0.5 vol%. These systems exhibited stable microstructures during thermal cycling in films containing at least 1.0%ZnO. Nanoindentation experiments show the drop in hardness following annealing is almost completely attributed to the resulting grain growth. Four-point probe resistivity measurements on annealed films showed a significant drop in resistivity for the higher concentration ZnO films, which is proposed to be the result of a change in the particle-matrix interface structure. A model connecting the hardness and resistivity as a function of ZnO concentration has been developed based on the assumption that the impact of nm-scale ZnO precipitates on the mechanical and electrical behavior of Au films is likely dominated by a transition from semi-coherent to incoherent interfaces.

Corrosion studies of DC reactive magnetron sputtered alumina coating on 304 SS

NASA Astrophysics Data System (ADS)

Thangaraj, Baskar; Mahadevan, Krishnan

2017-12-01

Aluminum oxide films on SS 304 deposited by DC reactive magnetron sputtering technique were studied with respect to the composition of the sputter gas (Ar:O2), gas pressure, substrate temperature, current etc. to achieve good insulating films with high corrosion resistance. The films were characterized by XRD and SEM techniques. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were made under static conditions in order to evaluate the corrosion performance of the alumina-coated SS 304 for various immersion durations in 0.5 M and 1 M NaCl solution. Alumina-coated SS 304 has low corrosion value of 0.4550 and 1.1090MPY for 24 h immersion time in both solutions. The impedance plots for the alumina coated SS 304 in 1 M NaCl solution at different durations are slightly different to when compared to its immersion in 0.5 M NaCl solutions and are composed of two depressed semi circles. For the alumina coated film, the impedance spectrum decreased, when immersion time increased.

Effect of TiO2 nanoparticles doping on structural and electrical properties of PVA: NaBr polymer electrolyte

NASA Astrophysics Data System (ADS)

Sagar, Rohan N.; Ravindrachary, V.; Guruswamy, B.; Hegde, Shreedatta; Mahanthesh, B. K.; Kumari, R. Padma

2018-05-01

The effect of TiO2 nanoparticles on morphology and electrical properties of PVA: NaBr composite films were carried out using various techniques. The pure and TiO2 nanoparticle doped PVA: NaBr composite films were prepared using solvent casting method. The FTIR spectral studies shows that the Ti+ ions of TiO2 interacts with hydroxyl group (OH) of PVA via hydrogen bonding and forms the charge transfer complexes (CTC). These interactions are of inter/intra molecular type and affects the surface morphology as well as the electrical properties of composite films. XRD study shows that the crystallinity of the composite increases with doping level. SEM studies shows that the increase in roughness of the surface of the composite films and uniform dispersion of nanofillers in polymer matrix. Electrical properties are analyzed using impedance analyzer and higher conductivity (10-4Scm-1) is achieved for 5 wt % TiO2 doping concentration.

Growth and structure of Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 thin films prepared by pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Lu, Lei; Xiao, Dingquan; Lin, Dunmin; Zhang, Yongbin; Zhu, Jianguo

2009-02-01

Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 (BNKLT) thin films were prepared on Pt/Ti/SiO 2/Si substrates by pulsed laser deposition (PLD) technique. The films prepared were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effects of the processing parameters, such as oxygen pressure, substrate temperature and laser power, on the crystal structure, surface morphology, roughness and deposition rates of the thin films were investigated. It was found that the substrate temperature of 600 °C and oxygen pressure of 30 Pa are the optimized technical parameters for the growth of textured film, and all the thin films prepared have granular structure, homogeneous grain size and smooth surfaces.

Leakage current behavior in lead-free ferroelectric (K,Na)NbO3-LiTaO3-LiSbO3 thin films

NASA Astrophysics Data System (ADS)

Abazari, M.; Safari, A.

2010-12-01

Conduction mechanisms in epitaxial (001)-oriented pure and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.1,Sb0.06)O3 (KNN-LT-LS) thin films on SrTiO3 substrate were investigated. Temperature dependence of leakage current density was measured as a function of applied electric field in the range of 200-380 K. It was shown that the different transport mechanisms dominate in pure and Mn-doped thin films. In pure (KNN-LT-LS) thin films, Poole-Frenkel emission was found to be responsible for the leakage, while Schottky emission was the dominant mechanism in Mn-doped thin films at higher electric fields. This is a remarkable yet clear indication of effect of 1 mol % Mn on the resistive behavior of such thin films.

Optical Properties of Ferroelectric Epitaxial K0.5Na0.5NbO3 Films in Visible to Ultraviolet Range

PubMed Central

Pacherova, O.; Kocourek, T.; Jelinek, M.; Dejneka, A.; Tyunina, M.

2016-01-01

The complex index of refraction in the spectral range of 0.74 to 4.5 eV is studied by variable-angle spectroscopic ellipsometry in ferroelectric K0.5Na0.5NbO3 films. The 20-nm-thick cube-on-cube-type epitaxial films are grown on SrTiO3(001) and DyScO3(011) single-crystal substrates. The films are transparent and exhibit a significant difference between refractive indices Δn = 0.5 at photon energies below 3 eV. The energies of optical transitions are in the range of 3.15–4.30 eV and differ by 0.2–0.3 eV in these films. The observed behavior is discussed in terms of lattice strain and strain-induced ferroelectric polarization in epitaxial perovskite oxide films. PMID:27074042

Efficiency enhancement using a Zn1- x Ge x -O thin film as an n-type window layer in Cu2O-based heterojunction solar cells

NASA Astrophysics Data System (ADS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2016-05-01

Efficiency enhancement was achieved in Cu2O-based heterojunction solar cells fabricated with a zinc-germanium-oxide (Zn1- x Ge x -O) thin film as the n-type window layer and a p-type Na-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing Cu sheets. The Ge content (x) dependence of the obtained photovoltaic properties of the heterojunction solar cells is mainly explained by the conduction band discontinuity that results from the electron affinity difference between Zn1- x Ge x -O and Cu2O:Na. The optimal value of x in Zn1- x Ge x -O thin films prepared by pulsed laser deposition was observed to be 0.62. An efficiency of 8.1% was obtained in a MgF2/Al-doped ZnO/Zn0.38Ge0.62-O/Cu2O:Na heterojunction solar cell.

Formulation and In Vitro Characterization of Thiolated Buccoadhesive Film of Fluconazole.

PubMed

Naz, Kiran; Shahnaz, Gul; Ahmed, Naveed; Qureshi, Naveeda Akhtar; Sarwar, Hafiz Shoaib; Imran, Muhammad; Khan, Gul Majid

2017-05-01

The present work is focused on the development of thiolated film for fluconazole buccal delivery. To this end, unmodified polymers chitosan and sodium carboxymethylcellulose (NaCMC) backbone was covalently modified by thioglycolic acid (TGA) and cysteine, respectively. The thiolated buccoadhesive film was evaluated in terms of thickness, weight uniformity, water-uptake capacity, drug content, and release patterns. Moreover, mucoadhesion profile was investigated on buccal mucosa. The resulting chitosan-TGA and NaCMC-cysteine conjugates displayed 171 ± 13 and 380 ± 19 μmol thiol groups per gram of polymer (mean ± SD; n = 3), respectively. The water binding capacity of the thiolated film was significantly ∼2-fold higher (p < 0.05) as compared to unmodified film. The obtained thiolated film displayed 5.8-fold higher mucoadhesive properties compared with corresponding film. Controlled release of drugs from film was observed over 8 h. The transport of fluconazole across excised buccal mucosa was enhanced up to 17-fold in comparison with fluconazole applied in buffer. Based on these findings, thiolated film seems to be promising for fluconazole buccal delivery.

Atomic-scale visualization of oxide thin-film surfaces.

PubMed

Iwaya, Katsuya; Ohsawa, Takeo; Shimizu, Ryota; Okada, Yoshinori; Hitosugi, Taro

2018-01-01

The interfaces of complex oxide heterostructures exhibit intriguing phenomena not observed in their constituent materials. The oxide thin-film growth of such heterostructures has been successfully controlled with unit-cell precision; however, atomic-scale understandings of oxide thin-film surfaces and interfaces have remained insufficient. We examined, with atomic precision, the surface and electronic structures of oxide thin films and their growth processes using low-temperature scanning tunneling microscopy. Our results reveal that oxide thin-film surface structures are complicated in contrast to the general perception and that atomically ordered surfaces can be achieved with careful attention to the surface preparation. Such atomically ordered oxide thin-film surfaces offer great opportunities not only for investigating the microscopic origins of interfacial phenomena but also for exploring new surface phenomena and for studying the electronic states of complex oxides that are inaccessible using bulk samples.

Interface investigation of solution processed high- κ ZrO2/Si MOS structure by DLTS

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Mondal, Sandip; Rao, Ksr Koteswara

The interfacial region is dominating due to the continuous downscaling and integration of high- k oxides in CMOS applications. The accurate characterization of high- k oxides/semiconductor interface has the significant importance towards its usage in memory and thin film devices. The interface traps at the high - k /semiconductor interface can be quantified by deep level transient spectroscopy (DLTS) with better accuracy in contrast to capacitance-voltage (CV) and conductance technique. We report the fabrication of high- k ZrO2 films on p-Si substrate by a simple and inexpensive sol-gel spin-coating technique. Further, the ZrO2/Si interface is characterized through DLTS. The flat-band voltage (VFB) and the density of slow interface states (oxide trapped charges) extracted from CV characteristics are 0.37 V and 2x10- 11 C/cm2, respectively. The activation energy, interface state density and capture cross-section quantified by DLTS are EV + 0.42 eV, 3.4x1011 eV- 1 cm- 2 and 5.8x10- 18 cm2, respectively. The high quality ZrO2 films own high dielectric constant 15 with low leakage current density might be an appropriate insulating layer in future electronic application. The low value of interface state density and capture cross-section are the indication of high quality interface and the defect present at the interface may not affect the device performance to a great extent. The DLTS study provides a broad understanding about the traps present at the interface of spin-coated ZrO2/Si.

DLTS Analysis and Interface Engineering of Solution Route Fabricated Zirconia Based MIS Devices Using Plasma Treatment

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Mondal, Sandip; Koteswara Rao, K. S. R.

2018-02-01

In this work, we have fabricated low-temperature sol-gel spin-coated and oxygen (O2) plasma treated ZrO2 thin film-based metal-insulator-semiconductor devices. To understand the impact of plasma treatment on the Si/ZrO2 interface, deep level transient spectroscopy measurements were performed. It is reported that the interface state density ( D it) comes down to 7.1 × 1010 eV-1 cm-2 from 4 × 1011 eV-1 cm-2, after plasma treatment. The reduction in D it is around five times and can be attributed to the passivation of oxygen vacancies near the Si/ZrO2 interface, as they try to relocate near the interface. The energy level position ( E T) of interfacial traps is estimated to be 0.36 eV below the conduction band edge. The untreated ZrO2 film displayed poor leakage behavior due to the presence of several traps within the film and at the interface; O2 plasma treated films show improved leakage current density as they have been reduced from 5.4 × 10-8 A/cm2 to 1.98 × 10-9 A/cm2 for gate injection mode and 6.4 × 10-8 A/cm2 to 6.3 × 10-10 A/cm2 for substrate injection mode at 1 V. Hence, we suggest that plasma treatment might be useful in future device fabrication technology.

Biopolymer films to control fusarium dry rot and their application to preserve potato tubers

USDA-ARS?s Scientific Manuscript database

Films were cast using sodium alginate (NaAlg), high molecular weight (HMW) chitosan, and low molecular weight (LMW) chitosan as film forming biopolymers. Fludioxonil (Fl) at 1% concentration was used as fungicide. Thermal stability, mechanical, and water sorption properties of the films were examine...

Electrohydrodynamic controlled assembly and fracturing of thin colloidal particle films confined at drop interfaces

NASA Astrophysics Data System (ADS)

Rozynek, Z.; Dommersnes, P.; Mikkelsen, A.; Michels, L.; Fossum, J. O.

2014-09-01

Particles can adsorb strongly at liquid interfaces due to capillary forces, which in practice can confine the particles to the interface. Here we investigate the electrohydrodynamic flow driven packing and deformation of colloidal particle layers confined at the surface of liquid drops. The electrohydrodynamic flow has a stagnation point at the drop equator, leading to assembly of particles in a ribbon shaped film. The flow is entirely controlled by the electric field, and we demonstrate that AC fields can be used to induce hydrodynamic "shaking" of the colloidal particle film. We find that the mechanical properties of the film is highly dependent on the particles: monodisperse polystyrene beads form packed granular monolayers which "liquefies" upon shaking, whereas clay mineral particles form cohesive films that fracture upon shaking. The results are expected to be relevant for understanding the mechanics and rheology of particle stabilized emulsions. Supplementary material in the form of a pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjst/e2014-02231-x

Interfacial structure, bonding and composition of InAs and GaSb thin films determined using coherent Bragg rod analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cionca, C.; Walko, D. A.; Yacoby, Y.

2007-01-01

We have used Bragg rod x-ray diffraction combined with a direct method of phase retrieval to extract atomic resolution electron-density maps of a complementary series of heteroepitaxial III-V semiconductor samples. From the three-dimensional electron-density maps we derive the monolayer spacings, the chemical compositions, and the characteristics of the bonding for all atomic planes in the film and across the film-substrate interface. InAs films grown on GaSb(001) under two different As conditions (using dimer or tetramer forms) both showed conformal roughness and mixed GaAs/InSb interfacial bonding character. The As tetramer conditions favored InSb bonding at the interface while, in the casemore » of the dimer, the percentages corresponding to GaAs and InSb bonding were equal within the experimental error. The GaSb film grown on InAs(001) displayed significant In and As interdiffusion and had a relatively large fraction of GaAs-like bonds at the interface.« less

Atmospheric photochemistry at a fatty acid-coated air-water interface

NASA Astrophysics Data System (ADS)

Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D. James; George, Christian

2016-08-01

Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

Depth profiling and morphological characterization of AlN thin films deposited on Si substrates using a reactive sputter magnetron

NASA Astrophysics Data System (ADS)

Macchi, Carlos; Bürgi, Juan; García Molleja, Javier; Mariazzi, Sebastiano; Piccoli, Mattia; Bemporad, Edoardo; Feugeas, Jorge; Sennen Brusa, Roberto; Somoza, Alberto

2014-08-01

It is well-known that the characteristics of aluminum nitride thin films mainly depend on their morphologies, the quality of the film-substrate interfaces and the open volume defects. A study of the depth profiling and morphological characterization of AlN thin films deposited on two types of Si substrates is presented. Thin films of thicknesses between 200 and 400 nm were deposited during two deposition times using a reactive sputter magnetron. These films were characterized by means of X-ray diffraction and imaging techniques (SEM and TEM). To analyze the composition of the films, energy dispersive X-ray spectroscopy was applied. Positron annihilation spectroscopy, specifically Doppler broadening spectroscopy, was used to gather information on the depth profiling of open volume defects inside the films and the AlN films-Si substrate interfaces. The results are interpreted in terms of the structural changes induced in the films as a consequence of changes in the deposition time (i.e., thicknesses) and of the orientation of the substrates.

Layering Transitions and Squeeze-Out Patterns in Nanoscale Polymeric Soap Films

NASA Astrophysics Data System (ADS)

Berg, Steffen; Troian, Sandra M.

2004-11-01

Oscillatory forces in freely suspended or confined nanofilms of micellar solutions, colloidal suspensions, alkanes and semidilute polyelectrolyte films generate stepwise thinning during the final stages of film drainage. The step jump correlates with the basic aggregation unit such as the micellar size or the polymer mesh size. In all studies so far reported, the interface separating films of different thickness is circular or elliptical, as seen in common or Newton black films. Our studies of freely suspended soaps films containing an anionic surfactant and nonionic polymer have revealed that the last stratification event expands with a fractal boundary whose dimension increases with the solution viscosity above a critical value. Unstable front propagation resembles a viscous fingering instability. We propose that internal film layering due to confinement of polymer-surfactant aggregates leads to a smaller viscosity in the thinnest film (≈ 12 nm), which rapidly penetrates into an exterior layer (≈ 62 nm) of higher viscosity. Subsequent coarsening of the fractal interface mimics shapes recently observed in macroscopic systems.

Ultrathin ZnS and ZnO Interfacial Passivation Layers for Atomic-Layer-Deposited HfO2 Films on InP Substrates.

PubMed

Kim, Seung Hyun; Joo, So Yeong; Jin, Hyun Soo; Kim, Woo-Byoung; Park, Tae Joo

2016-08-17

Ultrathin ZnS and ZnO films grown by atomic layer deposition (ALD) were employed as interfacial passivation layers (IPLs) for HfO2 films on InP substrates. The interfacial layer growth during the ALD of the HfO2 film was effectively suppressed by the IPLs, resulting in the decrease of electrical thickness, hysteresis, and interface state density. Compared with the ZnO IPL, the ZnS IPL was more effective in reducing the interface state density near the valence band edge. The leakage current density through the film was considerably lowered by the IPLs because the film crystallization was suppressed. Especially for the film with the ZnS IPL, the leakage current density in the low-voltage region was significantly lower than that observed for the film with the ZnO IPL, because the direct tunneling current was suppressed by the higher conduction band offset of ZnS with the InP substrate.

Strategies to improve the mechanical strength and water resistance of agar films for food packaging applications.

PubMed

Sousa, Ana M M; Gonçalves, Maria P

2015-11-05

Agar films possess several properties adequate for food packaging applications. However, their high cost-production and quality variations caused by physiological and environmental factors affecting wild seaweeds make them less attractive for industries. In this work, native (NA) and alkali-modified (AA) agars obtained from sustainably grown seaweeds (integrated multi-trophic aquaculture) were mixed with locust bean gum (LBG) to make 'knife-coated' films with fixed final concentration (1 wt%) and variable agar/LBG ratios. Agar films were easier to process upon LBG addition (viscosity increase and gelling character decrease of the film-forming solutions observed by dynamic oscillatory and steady shear measurements). The mechanical properties and water resistance were optimal for films with 50 and/or 75% LBG contents and best in the case of NA (cheaper to extract). These findings can help reduce the cost-production of agar packaging films. Moreover, the controlled cultivation of seaweeds can provide continuous and reliable feedstock for transformation industries. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface and interface of epitaxial CdTe film on CdS buffered van der Waals mica substrate

DOE PAGES

Yang, Y. -B.; Seewald, L.; Mohanty, Dibyajyoti; ...

2017-03-31

We report single crystal CdTe films are desirable for optoelectronic device applications. An important strategy of creating films with high crystallinity is through epitaxial growth on a proper single crystal substrate. We report the metalorganic chemical vapor deposition of epitaxial CdTe films on the CdS/mica substrate. The epitaxial CdS film was grown on a mica surface by thermal evaporation. Due to the weak van der Waals forces, epitaxy is achieved despite the very large interface lattice mismatch between CdS and mica (~21–55%). The surface morphology of mica, CdS and CdTe were quantified by atomic force microscopy. The near surface structures, orientations and texture of CdTe and CdS films were characterized by the unique reflection high-energy electron diffraction surface pole figure technique. The interfaces of CdTe and CdS films and mica were characterized by X-ray pole figure technique and transmission electron microscopy. The out-of-plane and in-plane epitaxy of the heteroepitaxial films stack are determined to be CdTe(111)//CdS(0001)//mica(001) and [more » $$\\overline{1}2\\overline{1}$$] CdTe//[$$\\overline{1}100$$] CdS//[010] mica, respectively. The measured photoluminescence (PL), time resolved PL, photoresponse, and Hall mobility of the CdTe/CdS/mica indicate quality films. Finally, the use of van der Waals surface to grow epitaxial CdTe/CdS films offers an alternative strategy towards infrared imaging and solar cell applications.« less

Surface and interface of epitaxial CdTe film on CdS buffered van der Waals mica substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y. -B.; Seewald, L.; Mohanty, Dibyajyoti

We report single crystal CdTe films are desirable for optoelectronic device applications. An important strategy of creating films with high crystallinity is through epitaxial growth on a proper single crystal substrate. We report the metalorganic chemical vapor deposition of epitaxial CdTe films on the CdS/mica substrate. The epitaxial CdS film was grown on a mica surface by thermal evaporation. Due to the weak van der Waals forces, epitaxy is achieved despite the very large interface lattice mismatch between CdS and mica (~21–55%). The surface morphology of mica, CdS and CdTe were quantified by atomic force microscopy. The near surface structures, orientations and texture of CdTe and CdS films were characterized by the unique reflection high-energy electron diffraction surface pole figure technique. The interfaces of CdTe and CdS films and mica were characterized by X-ray pole figure technique and transmission electron microscopy. The out-of-plane and in-plane epitaxy of the heteroepitaxial films stack are determined to be CdTe(111)//CdS(0001)//mica(001) and [more » $$\\overline{1}2\\overline{1}$$] CdTe//[$$\\overline{1}100$$] CdS//[010] mica, respectively. The measured photoluminescence (PL), time resolved PL, photoresponse, and Hall mobility of the CdTe/CdS/mica indicate quality films. Finally, the use of van der Waals surface to grow epitaxial CdTe/CdS films offers an alternative strategy towards infrared imaging and solar cell applications.« less

Potential energy landscape of an interstitial O2 molecule in a SiO2 film near the SiO2/Si(001) interface

NASA Astrophysics Data System (ADS)

Ohta, Hiromichi; Watanabe, Takanobu; Ohdomari, Iwao

2008-10-01

Potential energy distribution of interstitial O2 molecule in the vicinity of SiO2/Si(001) interface is investigated by means of classical molecular simulation. A 4-nm-thick SiO2 film model is built by oxidizing a Si(001) substrate, and the potential energy of an O2 molecule is calculated at Cartesian grid points with an interval of 0.05 nm in the SiO2 film region. The result shows that the potential energy of the interstitial site gradually rises with approaching the interface. The potential gradient is localized in the region within about 1 nm from the interface, which coincides with the experimental thickness of the interfacial strained layer. The potential energy is increased by about 0.62 eV at the SiO2/Si interface. The result agrees with a recently proposed kinetic model for dry oxidation of silicon [Phys. Rev. Lett. 96, 196102 (2006)], which argues that the oxidation rate is fully limited by the oxidant diffusion.

Detailed study of SiOxNy:H/Si interface properties for high quality surface passivation of crystalline silicon

NASA Astrophysics Data System (ADS)

Dong, Peng; Lei, Dong; Yu, Xuegong; Huang, Chunlai; Li, Mo; Dai, Gang; Zhang, Jian; Yang, Deren

2018-01-01

In this work, we present a detailed study on the interface and passivation properties of the hydrogenated silicon oxynitride (SiOxNy:H) on the crystalline silicon (c-Si) and their correlations with the film composition. The SiOxNy:H films were synthesized by plasma enhanced chemical vapor deposition (PECVD) at various N2O flow rates, which results in different film composition, in particular the different H-related bonds, such as Sisbnd H and Nsbnd H bonds. Fourier transform infrared spectroscopy measurements show that the concentration of Nsbnd H bonds increases with the N2O flows from 0 to 30 sccm, while drops below the detection limit at N2O flows above 30 sccm. This changing trend of Nsbnd H bonds correlates well with the evolution of carrier lifetime of silicon substrate passivated by SiOxNy:H film, indicating the crucial role of Nsbnd H bonds in surface passivation. It is inferred that during the film deposition and forming gas anneal (FGA) a considerable amount of hydrogen atoms are liberated from the weak type of Nsbnd H bonds rather than Sisbnd H bonds, and then passivate the dangling bonds at the interface, thus resulting in the significant reduction of interface state density and the improved passivation quality. In detail, the interface state density is reduced from ∼5 × 1012 to ∼2 × 1012 cm-2 eV-1 after the FGA, as derived from the high frequency capacitance-voltage (Csbnd V) measurements.

Characterization of poly(Sodium Styrene Sulfonate) Thin Films Grafted from Functionalized Titanium Surfaces

PubMed Central

Zorn, Gilad; Baio, Joe E.; Weidner, Tobias; Migonney, Veronique; Castner, David G.

2011-01-01

Biointegration of titanium implants in the body is controlled by their surface properties. Improving surface properties by coating with a bioactive polymer is a promising approach to improve the biological performance of titanium implants. To optimize the grafting processes, it is important to fully understand the composition and structure of the modified surfaces. The main focus of this study is to provide a detailed, multi-technique characterization of a bioactive poly(sodium styrene sulfonate) (pNaSS) thin film grafted from titanium surfaces via a two-step procedure. Thin titanium films (~50 nm thick with an average surface roughness of 0.9±0.2nm) prepared by evaporation onto silicon wafers were used as smooth model substrates. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that the titanium film was covered with a TiO2 layer that was at least 10nm thick and contained hydroxyl groups present at the outermost surface. These hydroxyl groups were first modified with a 3-methacryloxypropyltrimethoxysilane (MPS) cross linker. XPS and ToF-SIMS showed that a monolayer of the MPS molecules were successfully attached onto the titanium surfaces. The pNaSS film was grafted from the MPS modified titanium through atom transfer radical polymerization. Again, XPS and ToF-SIMS were used to verify that the pNaSS molecules were successfully grafted onto the modified surfaces. Atomic force microscopy analysis showed that the film was smooth and uniformly covered the surface. Fourier transform infrared spectroscopy indicated an ordered array of grafted NaSS molecules were present on the titanium surfaces. Sum frequency generation vibration spectroscopy and near edge X-ray absorption fine structure spectroscopy illustrated that the NaSS molecules were grafted onto the titanium surface with a substantial degree of orientational order in the styrene rings. PMID:21892821

The effect of ionic environment and mercury(II) binding on the alternative structures of DNA. An infrared spectroscopic study

NASA Astrophysics Data System (ADS)

Keller, P. B.; Hartman, K. A.

Infrared spectroscopy was used to measure the effects of NaCl, NaNO 3 and HgCl 2 on the structure and structural transitions of DNA in hydrated films. The following conclusions are supported by the data. (1) The transition from the B- to the A-structural form in films of salt-free, calf-thymus DNA occurs between 86 and 75% r.h. Previous failures to obtain this transition in salt-free films and the finding that ca 4% (w/w) NaCl is needed to observe the B to A transition in films of DNA appear to be anomalies produced by the very slow kinetics for this transition. (2) The addition of NaCl to DNA increases the quantity of water absorbed at a given r.h. value and shifts the B to A transition to lower r.h. values. (3) Highly hydrated DNA (100% r.h.) with or without added NaCl exists in the B-helical structure for all samples examined. (4) DNA films containing one NaNO 3 per 6.7 nucleotide residues remained in the B-helical form to very low values of hydration. (5) The interaction of HgCl 2 with DNA to form the type I complex prevents the transition of DNA from the B- to the A-helical form but a conformational variation within the B family of structures was observed to occur between 94 and 75% r.h. (6) The primary sites of binding of Hg 2+ in the type-1 complex with the DNA are the AT base pairs. Hg 2+ binds to the N3 atom of thymine. Binding of Hg 2+ to AT pairs perturbs the CG pairs but has only a minor effect on the sugar—phosphate conformation.

Thermal conductivity of SrVO3-SrTiO3 thin films: Evidence of intrinsic thermal resistance at the interface between oxide layers

NASA Astrophysics Data System (ADS)

Katsufuji, T.; Saiki, T.; Okubo, S.; Katayama, Y.; Ueno, K.

2018-05-01

By using a technique of thermoreflectance that can precisely measure the thermal conductivity of thin films, we found that the thermal conductivity of SrVO3-SrTiO3 multilayer thin films normal to the surface was substantially reduced by decreasing the thickness of each layer. This indicates that a large intrinsic thermal resistance exists at the interface between SrVO3 and SrTiO3 in spite of the similar phononic properties for these two compounds.

Epitaxial ferromagnetic oxide thin films on silicon with atomically sharp interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coux, P. de; CEMES-CNRS, 29 rue Jeanne Marvig, BP 94347, Toulouse Cedex 4; Bachelet, R.

A bottleneck in the integration of functional oxides with silicon, either directly grown or using a buffer, is the usual formation of an amorphous interfacial layer. Here, we demonstrate that ferromagnetic CoFe{sub 2}O{sub 4} films can be grown epitaxially on Si(111) using a Y{sub 2}O{sub 3} buffer layer, and remarkably the Y{sub 2}O{sub 3}/Si(111) interface is stable and remains atomically sharp. CoFe{sub 2}O{sub 4} films present high crystal quality and high saturation magnetization.

Effects of crystallization interfaces on irradiated ferroelectric thin films

NASA Astrophysics Data System (ADS)

Brewer, S. J.; Williams, S. C.; Cress, C. D.; Bassiri-Gharb, N.

2017-11-01

This work investigates the role of crystallization interfaces and chemical heterogeneity in the radiation tolerance of chemical solution-deposited lead zirconate titanate (PZT) thin films. Two sets of PZT thin films were fabricated with crystallization performed at (i) every deposited layer or (ii) every three layers. The films were exposed to a range of 60Co gamma radiation doses, between 0.2 and 20 Mrad, and their functional response was compared before and after irradiation. The observed trends indicate enhancements of dielectric, ferroelectric, and piezoelectric responses at low radiation doses and degradation of the same at higher doses. Response enhancements are expected to result from low-dose (≤2 Mrad), ionizing radiation-induced charging of internal interfaces—an effect that results in neutralization of pre-existing internal bias in the samples. At higher radiation doses (>2 Mrad), accumulation and self-ordering of radiation-modified, mobile, oxygen vacancy-related defects contribute to degradation of dielectric, ferroelectric, and piezoelectric properties, exacerbated in the samples with more crystallization layers, potentially due to increased defect accumulation at these internal interfaces. These results suggest that the interaction between radiation and crystallization interfaces is multifaceted—the effects of ionization, domain wall motion, point defect mobility, and microstructure are considered.

Measurements of ultrafast spin-profiles and spin-diffusion properties in the domain wall area at a metal/ferromagnetic film interface.

PubMed

Sant, T; Ksenzov, D; Capotondi, F; Pedersoli, E; Manfredda, M; Kiskinova, M; Zabel, H; Kläui, M; Lüning, J; Pietsch, U; Gutt, C

2017-11-08

Exciting a ferromagnetic material with an ultrashort IR laser pulse is known to induce spin dynamics by heating the spin system and by ultrafast spin diffusion processes. Here, we report on measurements of spin-profiles and spin diffusion properties in the vicinity of domain walls in the interface region between a metallic Al layer and a ferromagnetic Co/Pd thin film upon IR excitation. We followed the ultrafast temporal evolution by means of an ultrafast resonant magnetic scattering experiment in surface scattering geometry, which enables us to exploit the evolution of the domain network within a 1/e distance of 3 nm to 5 nm from the Al/FM film interface. We observe a magnetization-reversal close to the domain wall boundaries that becomes more pronounced closer to the Al/FM film interface. This magnetization-reversal is driven by the different transport properties of majority and minority carriers through a magnetically disordered domain network. Its finite lateral extension has allowed us to measure the ultrafast spin-diffusion coefficients and ultrafast spin velocities for majority and minority carriers upon IR excitation.

Efficient color display using low-absorption in-pixel color filters

NASA Technical Reports Server (NTRS)

Wang, Yu (Inventor)

2000-01-01

A display system having a non-absorbing and reflective color filtering array and a reflector to improve light utilization efficiency. One implementation of the color filtering array uses a surface plasmon filter having two symmetric metal-dielectric interfaces coupled with each other to produce a transmission optical wave at a surface plasmon resonance wavelength at one interface from a p-polarized input beam on the other interface. Another implementation of the color filtering array uses a metal-film interference filter having two dielectric layers and three metallic films.

Influence of alkali metals (Na, Li, Rb) on the performance of electrostatic spray-assisted vapor deposited Cu2ZnSn(S,Se)4 solar cells

NASA Astrophysics Data System (ADS)

Altamura, Giovanni; Wang, Mingqing; Choy, Kwang-Leong

2016-02-01

Electrostatic Spray-Assisted Vapor Deposition (ESAVD) is a non-vacuum and cost-effective method to deposit metal oxide, various sulphide and chalcogenide at large scale. In this work, ESAVD was used to deposit Cu2ZnSn(S1-xSex)4 (CZTSSe) absorber. Different alkali metals like Na, Li and Rb were incorporated in CZTSSe compounds to further improve the photovoltaic performances of related devices. In addition, to the best of our knowledge, no experimental study has been carried out to test the effect of Li and Rb incorporation in CZTSSe solar cells. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and glow discharge spectroscopy have been used to characterize the phase purity, morphology and composition of as-deposited CZTSSe thin films. Photovoltaic properties of the resulting devices were determined by completing the solar cells as follows: Mo/CZTSSe/CdS/i-ZnO/Al:ZnO/Ni/Al. The results showed that Li, Na and Rb incorporation can increase power conversion efficiency of CZTS devices up to 5.5%. The introduction of a thiourea treatment, has improved the quality of the absorber|buffer interface, pushed the device efficiency up to 6.3% which is at the moment the best reported result for ESAVD deposited CZTSSe solar cells.

Diffusion and interface evolution during the atomic layer deposition of TiO{sub 2} on GaAs(100) and InAs(100) surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Liwang; Gougousi, Theodosia, E-mail: gougousi@umbc.edu

2016-01-15

Atomic layer deposition is used to form TiO{sub 2} films from tetrakis dimethyl amino titanium and H{sub 2}O on native oxide GaAs(100) and InAs(100) surfaces. The evolution of the film/substrate interface is examined as a function of the deposition temperature (100–325 °C) using ex situ x-ray photoelectron spectroscopy. An increase in the deposition temperature up to 250 °C leads to enhancement of the native oxide removal. For depositions at 300 °C and above, interface reoxidation is observed during the initial deposition cycles but when the films are thicker than 3 nm, the surface oxides are removed steadily. Based on these observations, two distinct filmmore » growth regimes are identified; up to 250 °C, layer-by-layer dominates while at higher temperatures island growth takes over. Angle resolved x-ray photoelectron spectroscopy measurements performed on 3 nm TiO{sub 2} film deposited at 325 °C on both surfaces demonstrates a very important difference between the two substrates: for GaAs the native oxides remaining in the stack are localized at the interface, while for InAs(100), the indium oxides are mixed in the TiO{sub 2} film.« less

Introduction of Si/SiO{sub 2} interface states by annealing Ge-implanted films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marstein, E.S.; Gunnaes, A.E.; Olsen, A.

2004-10-15

Nanocrystals embedded in SiO{sub 2} films are the subject of a number of recent works, mainly because of their potential usefulness in the fabrication of optoelectronic devices and nanocrystal memory structures. One interesting method for the fabrication of such nanocrystals is the ion implantation of segregating species into SiO{sub 2} films followed by heat treatment in order to induce nanocrystal formation. This method is both relatively simple and also compatible with the current MOS (metal-oxide-semiconductor) device technology. An unintentional effect can occur during the fabrication of nanocrystals using this method, namely a significant diffusion of the implanted species during annealing,more » away from the regions with the highest concentration. The Si/SiO{sub 2} interface can be exposed to this diffusion flux. This can result in an altered interface and have a significant influence on electronic devices. Here, we report on ion implantation of Ge into SiO{sub 2} on Si followed by annealing under conditions, resulting in Ge accumulation at the Si/SiO{sub 2} interface as determined by secondary-ion mass spectroscopy analysis, transmission electron microscopy with energy dispersive analysis of x-rays, and Rutherford backscattering spectrometry. The accumulation of Ge at the Si/SiO{sub 2} interface has also been reported before. The resulting effect on the electronic structure of the interface is a priori unknown. We have fabricated MOS capacitors on the sample structures and their capacitance-voltage characteristics were measured and analyzed. We measure an interface state density around 1x10{sup 12} cm{sup -2}, which is high compared to standard Si MOS devices. We discuss the results in terms of the previous electrical measurements on Ge-oxide interfaces and SiGe interfaces, which also can yield a high interface state density. The specific conditions we report result in a sufficiently low Ge concentration that nanocrystals are not segregated in the SiO{sub 2} film, while Ge still accumulates at the Si/SiO{sub 2} interface after annealing.« less

Electric field induced self-assembly of monolayers of gold nanoparticles for surface enhanced Raman scattering applications

NASA Astrophysics Data System (ADS)

Das, Suchandra; Musunuri, Naga; Kucheryavy, Pavel; Lockard, Jenny; Fischer, Ian; Singh, Pushpendra; New Jersey Institute of Technology Collaboration; Rutgers University Newark Collaboration

2017-11-01

We present a technique that uses an electric field in the direction normal to the interface for self-assembling monolayers of gold nanoparticles on fluid-liquid interfaces and freezing these monolayers onto the surface of a flexible thin film. The electric field gives rise to dipole-dipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another fluid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film. We are using these films for surface enhanced Raman scattering (SERS) applications. Initial measurements indicate improved performance over commercially available SERS substrates.

Dewetting in immiscible polymer bilayer films

DOE PAGES

Lal, J.; Malkova, S.; Mukhopadhyay, M. K.; ...

2017-06-19

We have measured in situ the progression of dewetting from a large number of holes in immiscible polymer bilayer films. Using x-ray photon correlation spectroscopy (XPCS) in grazing incidence we probe independently the evolving dewetting process both at the top surface and the buried interface of the bilayer. At an early stage, differences in the evolution of the velocities measured by XPCS between the surface and buried interface indicate that the holes do not penetrate the bottom layer. The rim velocity at late stages decays according to a wave-vector-dependent power law, which indicates inhomogeneous flows in the film. The changesmore » in the static scattering show that observed slow-down of the dewetting velocity is correlated with the changing roughness at the buried interface of the polymer bilayer.« less

The atomic structure and polarization of strained SrTiO3/Si

NASA Astrophysics Data System (ADS)

Kumah, D. P.; Reiner, J. W.; Segal, Y.; Kolpak, A. M.; Zhang, Z.; Su, D.; Zhu, Y.; Sawicki, M. S.; Broadbridge, C. C.; Ahn, C. H.; Walker, F. J.

2010-12-01

For thin film devices based on coupling ferroelectric polarization to charge carriers in semiconductors, the role of the interface is critical. To elucidate this role, we use synchrotron x-ray diffraction to determine the interface structure of epitaxial SrTiO3 grown on the (001) surface of Si. The average displacement of the O octahedral sublattice relative to the Sr sublattice determines the film polarization and is measured to be about 0.05 nm toward the Si, with Ti off-center displacements 0.009 nm away from the substrate. Measurements of films with different boundary conditions on the top of the SrTiO3 show that the polarization at the SrTiO3/Si interface is dominated by oxide-Si chemical interactions.

Cobalt-supported alumina as catalytic film prepared by electrophoretic deposition for hydrogen release applications

NASA Astrophysics Data System (ADS)

Chamoun, R.; Demirci, U. B.; Cornu, D.; Zaatar, Y.; Khoury, A.; Khoury, R.; Miele, P.

2010-10-01

Shaped catalysts are crucial for technological applications. In this context, we have developed Co-αAl 2O 3 catalyst films deposited over Cu plates to be used in hydrogen generation by hydrolysis of sodium borohydride NaBH 4 in alkaline solution. The Co-αAl 2O 3 films were prepared by electrophoretic deposition according to six different routes. While five of them failed in fabricating adhering films, the sixth route, consisting of electrodepositing Co-impregnated αAl 2O 3, showed promising results. The as-obtained shaped catalysts were stable when hydrogen vigorously bubbled and catalyzed the NaBH 4 hydrolysis with attractive hydrogen generation rates. These results open an alternative route for preparing shaped catalysts in this reaction.

Direct Synthesis of Anatase Films with ~100% (001) Facets and [001] Preferred Orientation.

PubMed

Ichimura, Andrew S; Mack, Brianne; Usmani, Shirin M; Mars, Diana

2012-06-26

Anatase films exhibiting ~100% (001) reactive facets at the surface were grown hydrothermally on gold substrate from a homogeneous solution of TiF(4) and NaF. In addition to NaF, it was found that TiO(2) films with very similar properties could be prepared with the fluoride salts LiF, CsF, HF, NH(4)F, and N(CH(2)CH(3))(4)F. The polycrystalline anatase films are continuous, approximately 1 μm thick, and evenly coat the substrate. The surface grain size is ~400 nm. Grazing angle XRD measurements show that the films exhibit a high degree of preferred orientation with the c-axis normal to the substrate surface. SEM images reveal that the grains span the thickness of the films. Annealing the films at 500 °C removes fluorine and causes crystallites within the grains to restructure as shown by SEM, XRD, and Raman spectroscopy. Supported anatase films grown from this one-pot method may serve as oxidative photocatalysts and electrodes for photoelectrochemical applications such as solar cells and hydrogen evolution.

Role of interfacial transition layers in VO2/Al2O3 heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Honghui; Chisholm, Matthew F; Yang, Tsung-Han

2011-01-01

Epitaxial VO2 films grown by pulsed laser deposition (PLD) on c-cut sapphire substrates ((0001) Al2O3) were studied by aberration-corrected scanning transmission electron microscopy (STEM). A number of film/substrate orientation relationships were found and are discussed in the context of the semiconductor-metal transition (SMT) characteristics. A structurally and electronically modified buffer layer was revealed on the interface and was attributed to the interface free-energy minimization process of accommodating the symmetry mismatch between the substrate and the film. This interfacial transition layer is expected to affect the SMT behavior when the interfacial region is a significant fraction of the VO2 film thickness.

Weak ferromagnetism and short range polar order in NaMnF3 thin films

NASA Astrophysics Data System (ADS)

Kc, Amit; Borisov, Pavel; Shvartsman, Vladimir; Lederman, David

The orthorhombically distorted perovskite NaMnF3 has been predicted to become ferroelectric if an a = c distortion of the bulk Pnma structure is imposed. In order to test this prediction, NaMnF3 thin films were grown on SrTiO3 (100) single crystal substrates via molecular beam epitaxy. The best films were smooth and single phase with four different twin domains. In-plane magnetization measurements revealed the presence of antiferromagnetic ordering with weak ferromagnetism below the Néel temperature TN = 66 K. For the dielectric studies, NaMnF3 films were grown on a 30 nm SrRuO3 (100) layer used as a bottom electrode grown via pulsed laser deposition. The complex permittivity as a function of frequency indicated a strong Debye-like relaxation contribution characterized by a distribution of relaxation times. A power-law divergence of the characteristic relaxation time revealed an order-disorder phase transition at 8 K. The slow relaxation dynamics indicated the formation of super-dipoles (superparaelectric moments) that extend over several unit cells, similar to polar nanoregions of relaxor ferroelectrics. This work was supported by the National Science Foundation (Grant 1434897) and the WVU Shared Research Facilities at West Virginia University.

Thin Film Stability of Polystyrene with a Functional End Group

NASA Astrophysics Data System (ADS)

Tanaka, Keiji; Shimomura, Shinichiro; Inutsuka, Manabu; Tajima, Koichiro; Nabika, Masaaki; Moritomi, Satoru; Matsuno, Hisao; Kyushu Univ. Team; Sumitomo Chemical Co., Ltd. Collaboration

The thin film stability of omega- N-(3-(dimethylamino)propyl)propylamide-terminated polystyrene (PS-N) and its mixture with conventional polystyrene (PS-H) spin-coated on silicon wafers with a native oxide layer was studied. While a 20 nm-thick film of PS-H with a number-average molecular weight of approximately 50k was broken at 423 K, a comparable PS-N film and blend films with a PS-N fraction higher than 40 wt% were stable. Although the local conformation of chains at the substrate interface was not the same for PS with/without the functionalized terminal group, the glass transition temperature at the interface was identical for PS-H and PS-N. The residual adsorbed layer on the substrate after washing the films with toluene was thicker for PS-N than for PS-H. This implies that the end functionalization impacts chain movement on a large scale rather than via segmental dynamics.

Effects of Etching Time and NaOH Concentration on the Production of Alumina Nanowires Using Porous Anodic Alumina Template

NASA Astrophysics Data System (ADS)

Sadeghpour-Motlagh, M.; Mokhtari-Zonouzi, K.; Aghajani, H.; Kakroudi, M. Ghassemi

2014-06-01

In this work, two-step anodizing of commercial aluminum foil in acid oxalic solution was applied for producing alumina film. Then the anodic alumina film was etched in sodium hydroxide (NaOH) solution resulting dense and aligned alumina nanowires. This procedure leads to splitting of alumina nanotubes. Subsequently nanowires are produced. The effects of NaOH solution concentration (0.2-1 mol/L) and etching time (60-300 s) at constant temperature on characteristic of nanotubes and produced nanowires were investigated using scanning electron microscopy. The results show that an increase in NaOH solution concentration increases the rate of nanowires production and in turn the manipulation process will be more specific.

Electrolyte and Electrode Passivation for Thin Film Batteries

NASA Technical Reports Server (NTRS)

West, W.; Whitacre, J.; Ratnakumar, B.; Brandon, E.; Blosiu, J.; Surampudi, S.

2000-01-01

Passivation films for thin film batteries have been prepared and the conductivity and voltage stability window have been measured. Thin films of Li2CO3 have a large voltage stability window of 4.8V, which facilitates the use of this film as a passivation at both the lithium anode-electrolyte interface at high cathodic potentials.

Dispersing nanoparticles in a polymer film via solvent evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Shengfeng; Grest, Gary S.

Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

Manipulating the polar mismatch at the LaNi O 3 / SrTi O 3 (111) interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saghayezhian, M.; Wang, Zhen; Guo, Hangwen

2017-04-20

Heteroepitaxial growth of transition-metal oxide films on the open (111) surface of SrTi O 3 results in significant restructuring due to the polar mismatch. Monitoring the structure and composition on an atomic scale of LaNi O 3 / SrTi O 3 (111) interface as a function of processing conditions has enabled the avoidance of the expected polar catastrophe. Using atomically resolved transmission electron microscopy and spectroscopy as well as low-energy electron diffraction, the structure of the thin film, from interface to the surface, has been studied. Here, we show that the proper processing can lead to a structure that ismore » ordered, coherent with the substrate without intermediate structural phase. Using angle-resolved x-ray photoemission spectroscopy we show that the oxygen content of thin films increases with the film thickness, which indicates that the polar mismatch is avoided by the presence of oxygen vacancies.« less

Sequence control of phase separation and dewetting in PS/PVME blend thin films by changing molecular weight of PS.

PubMed

Xia, Tian; Qin, Yaping; Huang, Yajiang; Huang, Ting; Xu, Jianhui; Li, Youbing

2016-11-28

The morphology evolution mechanism of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films with different PS molecular weights (M w ) was studied. It was found that the morphology evolution was closely related to the molecular weight asymmetry between PS and PVME. In the film where M w (PS) ≈ M w (PVME), dewetting happened at the interface between the bottom layer and substrate after SD phase separation. While in the film where M w (PS) > M w (PVME), dewetting happened at the interface between the middle PS/PVME blend layer and bottom PVME layer near the substrate prior to phase separation. The different sequences of phase separation and dewetting and different interface for dewetting occurrence were studied by regarding the competitive effects of viscoelasticity contrast between polymer components and preferential wetting between PVME and the substrate. The viscoelastic nature of the PS component played a crucial role in the sequence of phase separation and dewetting.

A study of the properties and microstructure of Ni 81Fe 19 ultrathin films with MgO

NASA Astrophysics Data System (ADS)

Li, Minghua; Han, Gan; Ding, Lei; Wang, Xiaocui; Liu, Yang; Feng, Chun; Wang, Haicheng; Yu, Guanghua

2012-01-01

The anisotropic magnetoresistance (AMR) of a Ta (5 nm)/MgO (3 nm)/Ni81Fe19 (10 nm)/MgO (2 nm)/Ta (3 nm) film with MgO-Nano Oxide Layer (NOL) increases dramatically from 1.05% to 3.24% compared with a Ta (5 nm)/Ni81Fe19 (10 nm)/Ta (3 nm) film without the MgO-NOL layer after annealing at 380 °C for 2 h. Although the MgO destroys the NiFe (1 1 1) texture, it enhances the specular electron scattering of the conduction electrons at the NOL interface and suppresses the interface reactions and diffusion at the Ta/NiFe and NiFe/Ta interfaces. The NiFe (1 1 1) texture was formed after the annealing, resulting in a higher AMR ratio. X-ray photoelectron spectroscope results show that Mg and Mg2+ were present in the MgOx films.

Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

NASA Astrophysics Data System (ADS)

Cabrero-Vilatela, A.; Alexander-Webber, J. A.; Sagade, A. A.; Aria, A. I.; Braeuninger-Weimer, P.; Martin, M.-B.; Weatherup, R. S.; Hofmann, S.

2017-12-01

The transfer of chemical vapour deposited graphene from its parent growth catalyst has become a bottleneck for many of its emerging applications. The sacrificial polymer layers that are typically deposited onto graphene for mechanical support during transfer are challenging to remove completely and hence leave graphene and subsequent device interfaces contaminated. Here, we report on the use of atomic layer deposited (ALD) oxide films as protective interface and support layers during graphene transfer. The method avoids any direct contact of the graphene with polymers and through the use of thicker ALD layers (≥100 nm), polymers can be eliminated from the transfer-process altogether. The ALD film can be kept as a functional device layer, facilitating integrated device manufacturing. We demonstrate back-gated field effect devices based on single-layer graphene transferred with a protective Al2O3 film onto SiO2 that show significantly reduced charge trap and residual carrier densities. We critically discuss the advantages and challenges of processing graphene/ALD bilayer structures.

Strain Coupling of Conversion-type Fe 3O 4 Thin Films for Lithium Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Sooyeon; Meng, Qingping; Chen, Ping-Fan

2017-05-29

Lithiation/delithiation induces significant stresses and strains into the electrodes for lithium ion batteries, which can severely degrade their cycling performance. Moreover, this electrochemically induced strain can interact with the local strain existing at solid–solid interfaces. It is not clear how this interaction affects the lithiation mechanism. The effect of this coupling on the lithiation kinetics in epitaxial Fe 3O 4 thin film on a Nb-doped SrTiO 3 substrate is investigated. In-situ and ex-situ transmission electron microscopy (TEM) results show that the lithiation is suppressed by the compressive interfacial strain. At the interface between the film and substrate, the existence ofmore » Li xFe 3O 4 rock-salt phase during lithiation consequently restrains the film from delamination. 2D phase-field simulation verifies the effect of strain. This work provides critical insights of understanding the solid–solid interfaces of conversion-type electrodes.« less

Interfacial oxygen migration and its effect on the magnetic anisotropy in Pt/Co/MgO/Pt films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xi; Feng, Chun, E-mail: fengchun@ustb.edu.cn, E-mail: ghyu@mater.ustb.edu.cn; Liu, Yang

2014-02-03

This paper reports the interfacial oxygen migration effect and its induced magnetic anisotropy evolution in Pt/Co/MgO/Pt films. During depositing the MgO layer, oxygen atoms from the MgO combine with the neighboring Co atoms, leading to the formation of CoO at the Co/MgO interface. Meanwhile, the films show in-plane magnetic anisotropy (IMA). After annealing, most of the oxygen atoms in CoO migrate back to the MgO layer, resulting in obvious improvement of Co/MgO interface and the enhancement of effective Co-O orbital hybridization. These favor the evolution of magnetic anisotropy from IMA to perpendicular magnetic anisotropy (PMA). The oxygen migration effect ismore » achieved by the redox reaction at the Co/MgO interface. On the contrary, the transfer from IMA to PMA cannot be observed in Pt/Co/Pt films due to the lack of interfacial oxygen migration.« less

Dispersing nanoparticles in a polymer film via solvent evaporation

DOE PAGES

Cheng, Shengfeng; Grest, Gary S.

2016-05-19

Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

Depth resolved compositional analysis of aluminium oxide thin film using non-destructive soft x-ray reflectivity technique

NASA Astrophysics Data System (ADS)

Sinha, Mangalika; Modi, Mohammed H.

2017-10-01

In-depth compositional analysis of 240 Å thick aluminium oxide thin film has been carried out using soft x-ray reflectivity (SXR) and x-ray photoelectron spectroscopy technique (XPS). The compositional details of the film is estimated by modelling the optical index profile obtained from the SXR measurements over 60-200 Å wavelength region. The SXR measurements are carried out at Indus-1 reflectivity beamline. The method suggests that the principal film region is comprised of Al2O3 and AlOx (x = 1.6) phases whereas the interface region comprised of SiO2 and AlOx (x = 1.6) mixture. The soft x-ray reflectivity technique combined with XPS measurements explains the compositional details of principal layer. Since the interface region cannot be analyzed with the XPS technique in a non-destructive manner in such a case the SXR technique is a powerful tool for nondestructive compositional analysis of interface region.

Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO3 interface

PubMed Central

Zhao, Weiwei; Li, Mingda; Chang, Cui-Zu; Jiang, Jue; Wu, Lijun; Liu, Chaoxing; Moodera, Jagadeesh S.; Zhu, Yimei; Chan, Moses H. W.

2018-01-01

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (Tc) of monolayer iron selenide (FeSe) films on SrTiO3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiOx-terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing Tc of the films while minimally changing the carrier density. This increase in Tc is due to the positive backgate that “pulls” the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films. PMID:29556528

Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO 3 interface

DOE PAGES

Zhao, Weiwei; Li, Mingda; Chang, Cui -Zu; ...

2018-03-16

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (T c) of monolayer iron selenide (FeSe) films on SrTiO 3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first twomore » atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiO x-terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing T c of the films while minimally changing the carrier density. Furthermore, this increase in T c is due to the positive backgate that “pulls” the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.« less

Water permeation and electrical properties of pottants, backings, and pottant/backing composites

NASA Technical Reports Server (NTRS)

Orehotsky, J.

1986-01-01

It is reported that the interface between plastic film back covers and ethylene vinyl acetates (EVA) or polyvinyl butyral (PVB) in photovoltaic modules can influence water permeation, and electrial properties of the composites such as leakage current and dielectric constant. The interface can either be one of two dissimilar materials in physical contact with no intermixing, or the interface can constitute a thin zone which is an interphase of the two materials having a gradient composition from one material to the other. The former condition is described as a discrete interface. A discrete interface model was developed to predict water permeation, dielectric strength, and leakage current for EVA, ethylene methyl acrylate (EMA), and PVB coupled to Tedlar and mylar films. Experimental data was compared with predicted data.

Anomalously deep polarization in SrTiO3 (001) interfaced with an epitaxial ultrathin manganite film

DOE PAGES

Wang, Zhen; Tao, Jing; Yu, Liping; ...

2016-10-17

Using atomically-resolved imaging and spectroscopy, we reveal a remarkably deep polarization in non-ferroelectric SrTiO 3 near its interface with an ultrathin nonmetallic film of La 2/3Sr 1/3MnO 3. Electron holography shows an electric field near the interface in SrTiO 3, yielding a surprising spontaneous polarization density of ~ 21 μC/cm 2. Combining the experimental results with first principles calculations, we propose that the observed deep polarization is induced by the electric field originating from oxygen vacancies that extend beyond a dozen unit-cells from the interface, thus providing important evidence of the role of defects in the emergent interface properties ofmore » transition metal oxides.« less

Impedance spectroscopy of the electrode-tissue interface of living heart with isoösmotic conductivity perturbation

NASA Astrophysics Data System (ADS)

Ovadia, Marc; Zavitz, Daniel H.

2004-06-01

Impedance spectroscopy was used to solve the Pt electrode interface with metabolically active perfused living heart. Three impedance spectra were observed: the Warburg impedance ( ZW∞), a single high angle constant-phase-element, and a thin-film impedance ( ZD). When characterized again after cyclic change of ionic strength (and hence conductivity κ) each interface had one of only two spectra, with exclusion of ZW∞. The in vivo interfacial impedance spectrum is thus neither single-valued nor stable in time. Because metal|living tissue interfaces are obligatory circuit elements in biosensors and electrodes in heart and brain, the multiple-valued and thin-film character of its impedance are significant.

Dynamics of ultra-thin polystyrene with and without a (artificial) dead layer studied by resonance enhanced dynamic light scattering

NASA Astrophysics Data System (ADS)

Vianna, S. D. B.; Lin, F. Y.; Plum, M. A.; Duran, H.; Steffen, W.

2017-05-01

Using non-invasive, marker-free resonance enhanced dynamic light scattering, the dynamics of capillary waves on ultrathin polystyrene films' coupling to the viscoelastic and mechanical properties have been studied. The dynamics of ultrathin polymer films is still debated. In particular the question of what influence either the solid substrate and/or the fluid-gas interface has on the dynamics and the mechanical properties of films of glass forming liquids as polymers is in the focus of the present research. As a consequence, e.g., viscosity close to interfaces and thus the average viscosity of very thin films are prone to change. This study is focused on atactic, non-entangled polystyrene thin films on the gold surface. A slow dynamic mode was observed with Vogel-Fulcher-Tammann temperature dependence, slowing down with decreasing film thickness. We tentatively attribute this relaxation mode to overdamped capillary waves because of its temperature dependence and the dispersion with a wave vector which was found. No signs of a more mobile layer at the air/polymer interface or of a "dead layer" at the solid/polymer interface were found. Therefore we investigated the influence of an artificially created dead layer on the capillary wave dynamics by introducing covalently bound polystyrene polymer brushes as anchors. The dynamics was slowed down to a degree more than expected from theoretical work on the increase of density close to the solid liquid interface—instead of a "dead layer" of 2 nm, the interaction seems to extend more than 10 nm into the polymer.

Electron-stimulated reactions in nanoscale water films adsorbed on α-Al 2O 3 (0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrik, Nikolay G.; Kimmel, Gregory A.

The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D2O) films adsorbed on -Al2O3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products ( D2, O2 and D¬2O) and the total sputtering yield increased with increasing D2O coverage up to ~15 water monolayers (i.e. ~15 1015 cm-2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D2O and H2O) demonstrated that the highest water decomposition yields occurred at the interfaces of the nanoscalemore » water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO2(110) interfaces. We propose that the relatively low activity of Al2O3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the molecular hydrogen.100 eV electrons are stopped in the H 2O portion of the isotopically-layered nanoscale film on α-Al 2O 3(0001) but D 2is produced at the D 2O/alumina interface by mobile electronic excitations and/or hydronium ions.« less

Electronic structure at transition metal phthalocyanine-transition metal oxide interfaces: Cobalt phthalocyanine on epitaxial MnO films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glaser, Mathias; Peisert, Heiko, E-mail: heiko.peisert@uni-tuebingen.de; Adler, Hilmar

2015-03-14

The electronic structure of the interface between cobalt phthalocyanine (CoPc) and epitaxially grown manganese oxide (MnO) thin films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results reveal a flat-lying adsorption geometry of the molecules on the oxide surface which allows a maximal interaction between the π-system and the substrate. A charge transfer from MnO, in particular, to the central metal atom of CoPc is observed by both PES and XAS. The change of the shape of N-K XAS spectra at the interface points, however, to the involvement of the Pc macrocycle in the chargemore » transfer process. As a consequence of the charge transfer, energetic shifts of MnO related core levels were observed, which are discussed in terms of a Fermi level shift in the semiconducting MnO films due to interface charge redistribution.« less

Adsorption and Distribution of Edible Gliadin Nanoparticles at the Air/Water Interface.

PubMed

Peng, Dengfeng; Jin, Weiping; Li, Jing; Xiong, Wenfei; Pei, Yaqiong; Wang, Yuntao; Li, Yan; Li, Bin

2017-03-22

Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.

Spectroscopic investigation of the chemical and electronic properties of chalcogenide materials for thin-film optoelectronic devices

NASA Astrophysics Data System (ADS)

Horsley, Kimberly Anne

Chalcogen-based materials are at the forefront of technologies for sustainable energy production. This progress has come only from decades of research, and further investigation is needed to continue improvement of these materials. For this dissertation, a number of chalcogenide systems were studied, which have applications in optoelectronic devices, such as LEDs and Photovoltaics. The systems studied include Cu(In,Ga)Se2 (CIGSe) and CuInSe 2 (CISe) thin-film absorbers, CdTe-based photovoltaic structures, and CdTe-ZnO nanocomposite materials. For each project, a sample set was prepared through collaboration with outside institutions, and a suite of spectroscopy techniques was employed to answer specific questions about the system. These techniques enabled the investigation of the chemical and electronic structure of the materials, both at the surface and towards the bulk. CdS/Cu(In,Ga)Se2 thin-films produced from the roll-to-roll, ambient pressure, Nanosolar industrial line were studied. While record-breaking efficiency cells are usually prepared in high-vacuum (HV) or ultra-high vacuum (UHV) environments, these samples demonstrate competitive mass-production efficiency without the high-cost deposition environment. We found relatively low levels of C contaminants, limited Na and Se oxidation, and a S-Se intermixing at the CdS/CIGSe interface. The surface band gap compared closely to previously investigated CIGSe thin-films deposited under vacuum, illustrating that roll-to-roll processing is a promising and less-expensive alternative for solar cell production. An alternative deposition process for CuInSe2 was also studied, in collaboration with the University of Luxembourg. CuInSe2 absorbers were prepared with varying Cu content and surface treatments to investigate the potential to produce an absorber with a Cu-rich bulk and Cu-poor surface. This is desired to combine the bulk characteristics of reduced defects and larger grains in Cu-rich films, while maintaining a wide surface band gap, as seen in Cu-poor films. A novel absorber was prepared Cu-rich with a final In-Se treatment to produce a Cu-poor surface, and compared directly to Cu-poor and Cu-rich produced samples. Despite reduced Cu at the surface, the novel absorber was found to have a surface band gap similar to that of traditional, Cu-poor grown absorbers. Furthermore, estimation of the near-surface bulk band gap suggests a narrowing of the band gap away from the surface, similar to highly efficient, Cu-poor grown absorbers. Long-term degradation is another concern facing solar cells, as heat and moistures stress can result in reduced efficiencies over time. The interface of the back contact material and absorber layer in (Au/Cu)/CdTe/CdS thin-film structures from the University of Toledo were investigated after a variety of accelerated stress treatments with the aim of further understanding the chemical and/or electronic degradation of this interface. Sulfur migration to the back contact was observed, along with the formation of Au-S and Cu-S bonds. A correlation between heat stress under illumination and the formation of Cu-Cl bonds was also found. Nanocomposite materials hold promise as a next-generation photovoltaic material and for use in LED devices, due in part to the unique ability to tune the absorption edge of the film by adjusting the semiconductor particle size, and the prospective for long-range charge-carrier (exciton) transport through the wide band gap matrix material. Thin films of CdTe were sputter deposited onto ZnO substrates at the University of Arizona and studied before and after a short, high temperature annealing to further understand the effects of annealing on the CdTe/ZnO interface. A clumping of the CdTe layer and the formation of Cd- and Te-oxides was observed using surface microscopy and photoelectron spectroscopy techniques. These findings help to evaluate post-deposition annealing as a treatment to adjust the final crystallinity and optoelectronic properties of these films. Through publication and/or discussion with collaborators, each project presented in this dissertation contributed to the understanding of the chemical and electronic properties of the material surface, near-surface bulk, and/or interfaces formed. The information gained on these unique chalcogenide materials will assist in designing more efficient and successful optoelectronic devices for the next generation of solar cells and LEDs.

Reorientation of the ‘free OH’ group in the top-most layer of air/water interface of sodium fluoride aqueous solution probed with sum-frequency generation vibrational spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Ran-Ran; Guo, Yuan; Wang, Hongfei

2014-09-17

Many experimental and theoretical studies have established the specific anion, as well as cation effects on the hydrogen-bond structures at the air/water interface of electrolyte solutions. However, the ion effects on the top-most layer of the air/water interface, which is signified by the non-hydrogen-bonded so-called ‘free O-H’ group, has not been discussed or studied. In this report, we present the measurement of changes of the orientational angle of the ‘free O-H’ group at the air/water interface of the sodium fluoride (NaF) solutions at different concentrations using the interface selective sum-frequency generation vibrational spectroscopy (SFG-VS) in the ssp and ppp polarizations.more » The polarization dependent SFG-VS results show that the average tilt angle of the ‘free O-H’ changes from about 35.3 degrees ± 0.5 degrees to 43.4 degrees ± 2.1degrees as the NaF concentration increase from 0 to 0.94M (nearly saturated). Such tilt angle change is around the axis of the other O-H group of the same water molecule at the top-most layer at the air/water interface that is hydrogen-bonded to the water molecules below the top-most layer. These results provide quantitative molecular details of the ion effects of the NaF salt on the structure of the water molecules at the top-most layer of the air/water interfacial, even though both the Na+ cation and the F- anion are believed to be among the most excluded ions from the air/water interface.« less

Interface and Electronic Characterization of Thin Epitaxial Co3O4 Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaz, C.A.; Zhu, Y.; Wang, H.-Q.

2009-01-15

The interface and electronic structure of thin ({approx} 20-74 nm) Co{sub 3}O{sub 4}(1 1 0) epitaxial films grown by oxygen-assisted molecular beam epitaxy on MgAl{sub 2}O{sub 4}(1 1 0) single crystal substrates have been investigated by means of real and reciprocal space techniques. As-grown film surfaces are found to be relatively disordered and exhibit an oblique low energy electron diffraction (LEED) pattern associated with the O-rich CoO{sub 2} bulk termination of the (1 1 0) surface. Interface and bulk film structure are found to improve significantly with post-growth annealing at 820 K in air and display sharp rectangular LEED patterns,more » suggesting a surface stoichiometry of the alternative Co{sub 2}O{sub 2} bulk termination of the (1 1 0) surface. Non-contact atomic force microscopy demonstrates the presence of wide terraces separated by atomic steps in the annealed films that are not present in the as-grown structures; the step height of {approx}2.7 {angstrom} corresponds to two atomic layers and confirms a single termination for the annealed films, consistent with the LEED results. A model of the (1 x 1) surfaces that allows for compensation of the polar surfaces is presented.« less

Preparation and characterization of mono- and multilayer films of polymerizable 1,2-polybutadiene using the Langmuir-Blodgett technique.

PubMed

Hitrik, Maria; Gutkin, Vitaly; Lev, Ovadia; Mandler, Daniel

2011-10-04

The essence of this study is to apply the Langmuir-Blodgett (LB) technique for assembling asymmetric membranes. Accordingly, Langmuir films of a (further) polymerizable polymer, 1,2-polybutadiene (1,2-pbd), were studied and transferred onto different solid supports, such as gold, indium tin oxide (ITO), and silicon. The layers were characterized both at the air/water interface as well as on different substrates using numerous methods including cyclic voltammetry, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, and reflection-absorption Fourier transform infrared spectroscopy. The Langmuir films were stable at the air-water interface as long as they were not exposed to UV irradiation. The LB films formed disorganized layers, which gradually blocked the permeation of different species with increasing the number of deposited layers. The thickness was ca. 4-7 Å per layer. Irradiating the Langmuir films caused their cross-linking at the air-water interface. Furthermore, we took advantage of the reactivity of the double bond of the LB films on the solid supports and graft polymerized acrylic acid on top of the 1,2-pbd layers. This approach is the basis of the formation of an asymmetric membrane that requires different porosity on both of its sides. © 2011 American Chemical Society

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

NASA Astrophysics Data System (ADS)

Khosa, R. Y.; Thorsteinsson, E. B.; Winters, M.; Rorsman, N.; Karhu, R.; Hassan, J.; Sveinbjörnsson, E. Ö.

2018-02-01

We report on the electrical properties of Al2O3 films grown on 4H-SiC by successive thermal oxidation of thin Al layers at low temperatures (200°C - 300°C). MOS capacitors made using these films contain lower density of interface traps, are more immune to electron injection and exhibit higher breakdown field (5MV/cm) than Al2O3 films grown by atomic layer deposition (ALD) or rapid thermal processing (RTP). Furthermore, the interface state density is significantly lower than in MOS capacitors with nitrided thermal silicon dioxide, grown in N2O, serving as the gate dielectric. Deposition of an additional SiO2 film on the top of the Al2O3 layer increases the breakdown voltage of the MOS capacitors while maintaining low density of interface traps. We examine the origin of negative charges frequently encountered in Al2O3 films grown on SiC and find that these charges consist of trapped electrons which can be released from the Al2O3 layer by depletion bias stress and ultraviolet light exposure. This electron trapping needs to be reduced if Al2O3 is to be used as a gate dielectric in SiC MOS technology.

Sublimable chloroquinolinate lanthanoid single-ion magnets deposited on ferromagnetic electrodes† †Electronic supplementary information (ESI) available. CCDC 1557647–1557649. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03463f

PubMed Central

Miralles, Sara G.; Bedoya-Pinto, Amilcar; Baldoví, José J.; Cañon-Mancisidor, Walter; Prado, Yoann; Prima-Garcia, Helena; Gaita-Ariño, Alejandro; Mínguez Espallargas, Guillermo

2017-01-01

A new family of chloroquinolinate lanthanoid complexes of the formula A+[Ln(5,7Cl2q)4]–, with Ln = Y3+, Tb3+ and Dy3+ and A+ = Na+, NEt4+ and K0.5(NEt4)0.5+, is studied, both in bulk and as thin films. Several members of the family are found to present single-molecule magnetic behavior in bulk. Interestingly, the sodium salts can be sublimed under high vacuum conditions retaining their molecular structures and magnetic properties. These thermally stable compounds have been deposited on different substrates (Al2O3, Au and NiFe). The magnetic properties of these molecular films show the appearance of cusps in the zero-field cooled curves when they are deposited on permalloy (NiFe). This indicates a magnetic blocking caused by the interaction between the single-ion magnet and the ferromagnet. X-ray absorption spectroscopy confirms the formation of hybrid states at the molecule/metal interface. PMID:29629088

Improved efficiency of a large-area Cu(In,Ga)Se₂ solar cell by a nontoxic hydrogen-assisted solid Se vapor selenization process.

PubMed

Wu, Tsung-Ta; Hu, Fan; Huang, Jyun-Hong; Chang, Chia-ho; Lai, Chih-chung; Yen, Yu-Ting; Huang, Hou-Ying; Hong, Hwen-Fen; Wang, Zhiming M; Shen, Chang-Hong; Shieh, Jia-Min; Chueh, Yu-Lun

2014-04-09

A nontoxic hydrogen-assisted solid Se vapor selenization process (HASVS) technique to achieve a large-area (40 × 30 cm(2)) Cu(In,Ga)Se2 (CIGS) solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for active area) was demonstrated. The remarkable improvement of efficiency and fill factor comes from improved open circuit voltage (Voc) and reduced dark current due to (1) decreased interface recombination raised from the formation of a widened buried homojunction with n-type Cd(Cu) participation and (2) enhanced separation of electron and hole carriers resulting from the accumulation of Na atoms on the surface of the CIGS film. The effects of microstructural, compositional, and electrical characteristics with hydrogen-assisted Se vapor selenization, including interdiffusion of atoms and formation of buried homojunction, were examined in detail. This methodology can be also applied to CIS (CuInSe2) thin film solar cells with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area) and provides a facile approach to improve quality of CIGS and stimulate the nontoxic progress in the large scale CIGS PV industry.

NaNet-10: a 10GbE network interface card for the GPU-based low-level trigger of the NA62 RICH detector.

NASA Astrophysics Data System (ADS)

Ammendola, R.; Biagioni, A.; Fiorini, M.; Frezza, O.; Lonardo, A.; Lamanna, G.; Lo Cicero, F.; Martinelli, M.; Neri, I.; Paolucci, P. S.; Pastorelli, E.; Piandani, R.; Pontisso, L.; Rossetti, D.; Simula, F.; Sozzi, M.; Tosoratto, L.; Vicini, P.

2016-03-01

A GPU-based low level (L0) trigger is currently integrated in the experimental setup of the RICH detector of the NA62 experiment to assess the feasibility of building more refined physics-related trigger primitives and thus improve the trigger discriminating power. To ensure the real-time operation of the system, a dedicated data transport mechanism has been implemented: an FPGA-based Network Interface Card (NaNet-10) receives data from detectors and forwards them with low, predictable latency to the memory of the GPU performing the trigger algorithms. Results of the ring-shaped hit patterns reconstruction will be reported and discussed.

Evaporation thermal anslysis of Swallow-tailed Axial-grooved Heat Pipe

NASA Astrophysics Data System (ADS)

Zhang, Renping

2018-03-01

A detailed mathematical model that describes evaporating characteristics through thin liquid film at the evaporator section of swallow-tailed axial-grooved heat pipe was developed. The numerical simulation results about thin film profile, liquid-vapour interface temperature, evaporating rate and heat flux at the evaporating thin film region were given by the current investigation and the effect of superheat on the liquid-vapour interface temperature, evaporating mass rate and heat flux was discussed. Meanwhile, thermal model of the meniscus region at the evaporating section was developed to calculate the rate of heat transfer. The ratio of the heat conduction in the evaporating thin liquid film region and total heat rate were also discussed. It is indicated that the thickness of thin liquid film rises in a nearly linear fashion. The disjoining pressure can be neglected with increasing the liquid film thickness, tends to be negligibly small. The heat transfer rate at the intrinsic meniscus cannot be compared with that of the evaporating liquid film region.

Self-assembly of large-scale crack-free gold nanoparticle films using a ‘drain-to-deposit’ strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Guang; Hallinan, Daniel T.

2016-04-26

Gold nanoparticles are widely studied due to the ease of controlled synthesis, facile surface modification, and interesting physical properties. However, a technique for depositing large-area, crack-free monolayers on solid substrates is lacking. Herein is presented a method for accomplishing this. Spherical gold nanoparticles were synthesized as an aqueous dispersion. Assembly into monolayers and ligand exchange occurred simultaneously at an organic/aqueous interface. Then the monolayer film was deposited onto arbitrary solid substrates by slowly pumping out the lower, aqueous phase. This allowed the monolayer film (and liquid–liquid interface) to descend without significant disturbance, eventually reaching substrates contained in the aqueous phase.more » The resulting macroscopic quality of the films was found to be superior to films transferred by Langmuir techniques. The surface plasmon resonance and Raman enhancement of the films were evaluated and found to be uniform across the surface of each film.« less

Micron-scale channel formation by the release and bond-back of pre-stressed thin films: A finite element analysis

NASA Astrophysics Data System (ADS)

Annabattula, R. K.; Huck, W. T. S.; Onck, P. R.

2010-04-01

Buckling of thin films on a rigid substrate during use or fabrication is a well-known but unwanted phenomenon. However, this phenomenon can also be exploited to generate well-controlled patterns at the micro and nano-scale. These patterned surfaces find various technological applications such as optical gratings or micro/nano-fluidic channels. In this article, we present a numerical model that accounts for the buckling-up of pre-strained thin films by a reduction of the interface toughness and the subsequent bond-back. Channels are formed whose dimensions can be controlled by tuning the film dimensions, film thickness and stiffness, the eigenstrain in the film and the cohesive interface energy between the film and the substrate. We will show how the buckling-up and draping back processes can be captured in terms of a limited set of dimensionless parameters, providing quantitative insight on how these parameters should be tuned to generate a specified channel geometry.

Finite-size versus interface-proximity effects in thin-film epitaxial SrTiO3

NASA Astrophysics Data System (ADS)

De Souza, R. A.; Gunkel, F.; Hoffmann-Eifert, S.; Dittmann, R.

2014-06-01

The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10-23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.

Characterization of single-crystalline Al films grown on Si(111)

NASA Astrophysics Data System (ADS)

Fortuin, A. W.; Alkemade, P. F. A.; Verbruggen, A. H.; Steinfort, A. J.; Zandbergen, H.; Radelaar, S.

1996-10-01

Single-crystalline Al films have been grown by molecular beam epitaxy on a (7 × 7) reconstructed Si(111) surface at 50°C. The 100 nm thick Al films were extensively characterized by X-ray diffraction, transmission electron diffraction and microscopy, SIMS, and RBS in combination with ion channeling. The orientational relationship found was Al(111) t' | Si(111) and Al[11¯0] t'| Si[11¯0]. The film is single-crystalline over the entire 4″ Si wafer. TED and TEM showed that the lattice mismatch of 25.3% at room temperature is accommodated at the interface by alignment of every three Si atoms to four Al atoms. Annealing of the film at 400°C for 30 min led to a reduction of defects in the film and an increase at the interface. Furthermore, it increased the Si concentration in the Al film slightly. We regard this deposition method as the most appropriate one among the various techniques for epitaxial growth of Al on Si explored so far.

The Interface Structure of FeSe Thin Film on CaF2 Substrate and its Influence on the Superconducting Performance.

PubMed

Qiu, Wenbin; Ma, Zongqing; Patel, Dipak; Sang, Lina; Cai, Chuanbing; Shahriar Al Hossain, Mohammed; Cheng, Zhenxiang; Wang, Xiaolin; Dou, Shi Xue

2017-10-25

The investigations into the interfaces in iron selenide (FeSe) thin films on various substrates have manifested the great potential of showing high-temperature-superconductivity in this unique system. In present work, we obtain FeSe thin films with a series of thicknesses on calcium fluoride (CaF 2 ) (100) substrates and glean the detailed information from the FeSe/CaF 2 interface by using scanning transmission electron microscopy (STEM). Intriguingly, we have found the universal existence of a calcium selenide (CaSe) interlayer with a thickness of approximate 3 nm between FeSe and CaF 2 in all the samples, which is irrelevant to the thickness of FeSe layers. A slight Se deficiency occurs in the FeSe layer due to the formation of CaSe interlayer. This Se deficiency is generally negligible except for the case of the ultrathin FeSe film (8 nm in thickness), in which the stoichiometric deviation from FeSe is big enough to suppress the superconductivity. Meanwhile, in the overly thick FeSe layer (160 nm in thickness), vast precipitates are found and recognized as Fe-rich phases, which brings about degradation in superconductivity. Consequently, the thickness dependence of superconducting transition temperature (T c ) of FeSe thin films is investigated and one of our atmosphere-stable FeSe thin film (127 nm) possesses the highest T c onset /T c zero as 15.1 K/13.4 K on record to date in the class of FeSe thin film with practical thickness. Our results provide a new perspective for exploring the mechanism of superconductivity in FeSe thin film via high-resolution STEM. Moreover, approaches that might improve the quality of FeSe/CaF 2 interfaces are also proposed for further enhancing the superconducting performance in this system.

Atomic-scale structural and electronic properties of SrTiO3/GaAs interfaces: A combined STEM-EELS and first-principles study

NASA Astrophysics Data System (ADS)

Hong, Liang; Bhatnagar, Kunal; Droopad, Ravi; Klie, Robert F.; Öǧüt, Serdar

2017-07-01

The electronic properties of epitaxial oxide thin films grown on compound semiconductors are largely determined by the interfacial atomic structure, as well as the thermodynamic conditions during synthesis. Ferroelectric polarization and Fermi-level pinning in SrTiO3 films have been attributed to the presence of oxygen vacancies at the oxide/semiconductor interface. Here, we present scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy analyses of GaAs films grown on SrTiO3 combined with first-principles calculations to determine the atomic and electronic structures of the SrTiO3/GaAs interfaces. An atomically abrupt SrO/As interface is observed and the interfacial SrO layer is found to be O-deficient. First-principles density functional theory (DFT) calculations show SrO/Ga and Sr/As interfaces are favorable under O-rich and O-poor conditions, respectively. The SrO/Ga interface is reconstructed via the formation of Ga-Ga dimers while the Sr/As interface is abrupt and consistent with the experiment. DFT calculations further reveal that intrinsic two-dimensional electron gas (2DEG) forms in both SrO/Ga and Sr/As interfaces, and the Fermi level is pinned to the localized 2DEG states. Interfacial O vacancies can enhance the 2DEG density while it is possible for Ga/As vacancies to unpin the Fermi level from the 2DEG states.

Influence of Thickness and Interface on the Low-Temperature Enhancement of the Spin Seebeck Effect in YIG Films

DOE PAGES

Guo, Er-Jia; Cramer, Joel; Kehlberger, Andreas; ...

2016-07-27

The temperature-dependent longitudinal spin Seebeck effect (LSSE) in heavy metal (HM)/Y 3Fe 5O 12 (YIG) hybrid structures is investigated as a function of YIG film thickness, magnetic field strength, and different HM detection materials. The LSSE signal shows a large enhancement with reductions in temperature, leading to a pronounced peak at low temperatures. Here we find that the LSSE peak temperature strongly depends on the film thickness as well as on the magnetic field. Our result can be well explained in the framework of magnon-driven LSSE by taking into account the temperature-dependent effective propagation length of thermally excited magnons inmore » the bulk of the material. We further demonstrate that the LSSE peak is significantly shifted by changing the interface coupling to an adjacent detection layer, revealing a more complex behavior beyond the currently discussed bulk effect. By direct microscopic imaging of the interface, we correlate the observed temperature dependence with the interface structure between the YIG and the adjacent metal layer. Finally, our results highlight the role of interface effects on the temperature-dependent LSSE in HM/YIG system, suggesting that the temperature-dependent spin current transparency strikingly relies on the interface conditions.« less

In situ assessment of the contact angles of nanoparticles adsorbed at fluid interfaces by multiple angle of incidence ellipsometry.

PubMed

Stocco, Antonio; Su, Ge; Nobili, Maurizio; In, Martin; Wang, Dayang

2014-09-28

Here multiple angle of incidence ellipsometry was successfully applied to in situ assess the contact angle and surface coverage of gold nanoparticles as small as 18 nm, coated with stimuli-responsive polymers, at water-oil and water-air interfaces in the presence of NaCl and NaOH, respectively. The interfacial adsorption of the nanoparticles was found to be very slow and took days to reach a fairly low surface coverage. For water-oil interfaces, in situ nanoparticle contact angles agree with the macroscopic equilibrium contact angles of planar gold surfaces with the same polymer coatings, whilst for water-air interfaces, significant differences have been observed.

Preparation and properties of biodegradable films from Sterculia urens short fiber/cellulose green composites.

PubMed

Jayaramudu, J; Reddy, G Siva Mohan; Varaprasad, K; Sadiku, E R; Sinha Ray, S; Varada Rajulu, A

2013-04-02

The development of commercially viable "green products", based on natural resources for the matrices and reinforcements, in a wide range of applications, is on the rise. The present paper focuses on Sterculia urens short fiber reinforced pure cellulose matrix composite films. The morphologies of the untreated and 5% NaOH (alkali) treated S. urens fibers were observed by SEM. The effect of 5% NaOH treated S. urens fiber (5, 10, 15 and 20% loading) on the mechanical properties and thermal stability of the composites films is discussed. This paper presents the developments made in the area of biodegradable S. urens short fiber/cellulose (SUSF/cellulose) composite films, buried in the soil and later investigated by the (POM), before and after biodegradation has taken place. SUSF/cellulose composite films have great potential in food packaging and for medical applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of Alloying Element Ca on the Corrosion Behavior and Bioactivity of Anodic Films Formed on AM60 Mg Alloys

PubMed Central

Anawati, Anawati; Asoh, Hidetaka; Ono, Sachiko

2016-01-01

Effects of alloying element Ca on the corrosion behavior and bioactivity of films formed by plasma electrolytic oxidation (PEO) on AM60 alloys were investigated. The corrosion behavior was studied by conducting electrochemical tests in 0.9% NaCl solution while the bioactivity was evaluated by soaking the specimens in simulated body fluid (SBF). Under identical anodization conditions, the PEO film thicknesses increased with increasing Ca content in the alloys, which enhanced the corrosion resistance in NaCl solution. Thicker apatite layers grew on the PEO films of Ca-containing alloys because Ca was incorporated into the PEO film and because Ca was present in the alloys. Improvement of corrosion resistance and bioactivity of the PEO-coated AM60 by alloying with Ca may be beneficial for biodegradable implant applications. PMID:28772371

Covering surface nanobubbles with a NaCl nanoblanket.

PubMed

Berkelaar, Robin P; Zandvliet, Harold J W; Lohse, Detlef

2013-09-10

By letting a NaCl aqueous solution of low (0.01 M) concentration evaporate on a highly oriented pyrolytic graphite (HOPG) surface, it is possible to form a thin film of salt. However, pre-existing surface nanobubbles prevent the homogeneous coverage of the surface with the salt, keeping the footprint areas on the substrate pristine. Comparing the surface nanobubbles in the salt solution with their associated footprint after drying, provides information on the shrinkage of nanobubbles during the hours-long process of drying the liquid film. At a slightly higher NaCl concentration and thus salt layer thickness, the nanobubbles are covered with a thin blanket of salt. Once the liquid film has evaporated until a water film remains that is smaller than the height of the nanobubbles, the blanket of salt cracks and unfolds into a flower-like pattern of salt flakes that is located at the rim of the nanobubble footprint. The formation of a blanket of salt covering the nanobubbles is likely to considerably or even completely block the gas out-flux from the nanobubble, partially stabilizing the nanobubbles against dissolution.

Interface-engineered oxygen octahedral coupling in manganite heterostructures

NASA Astrophysics Data System (ADS)

Huijben, M.; Koster, G.; Liao, Z. L.; Rijnders, G.

2017-12-01

Control of the oxygen octahedral coupling (OOC) provides a large degree of freedom to manipulate physical phenomena in complex oxide heterostructures. Recently, local tuning of the tilt angle has been found to control the magnetic anisotropy in ultrathin films of manganites and ruthenates, while symmetry control can manipulate the metal insulator transition in nickelate thin films. The required connectivity of the octahedra across the heterostructure interface enforces a geometric constraint to the 3-dimensional octahedral network in epitaxial films. Such geometric constraint will either change the tilt angle to retain the connectivity of the corner shared oxygen octahedral network or guide the formation of a specific symmetry throughout the epitaxial film. Here, we will discuss the control of OOC in manganite heterostructures by interface-engineering. OOC driven magnetic and transport anisotropies have been realized in LSMO/NGO heterostructures. Competition between the interfacial OOC and the strain further away from the interface leads to a thickness driven sharp transition of the anisotropic properties. Furthermore, octahedral relaxation leading to a change of p-d hybridization driven by interfacial OOC appears to be the strongest factor in thickness related variations of magnetic and transport properties in epitaxial LSMO films on NGO substrates. The results unequivocally link the atomic structure near the interfaces to the macroscopic properties. The strong correlation between a controllable oxygen network and the functionalities will have significant impact on both fundamental research and technological application of correlated perovskite heterostructures. By controlling the interfacial OOC, it is possible to pattern in 3 dimensions the magnetization to achieve non-collinear magnetization in both in-plane and out of plane directions, thus making the heterostructures promising for application in orthogonal spin transfer devices, spin oscillators, and low field sensors.

Investigation of hydrogen concentration and hardness of ion irradiated organically modified silicate thin films

NASA Astrophysics Data System (ADS)

Qi, Y.; Prenzel, T.; Harriman, T. A.; Wang, Y. Q.; Lucca, D. A.; Williams, D.; Nastasi, M.; Dong, J.; Mehner, A.

2010-06-01

A study of the effects of ion irradiation of organically modified silicate thin films on the loss of hydrogen and increase in hardness is presented. NaOH catalyzed SiNa wO xC yH z thin films were synthesized by sol-gel processing from tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) precursors and spin-coated onto Si substrates. After drying at 300 °C, the films were irradiated with 125 keV H + or 250 keV N 2+ at fluences ranging from 1 × 10 14 to 2.5 × 10 16 ions/cm 2. Elastic Recoil Detection (ERD) was used to investigate resulting hydrogen concentration as a function of ion fluence and irradiating species. Nanoindentation was used to measure the hardness of the irradiated films. FT-IR spectroscopy was also used to examine resulting changes in chemical bonding. The resulting hydrogen loss and increase in hardness are compared to similarly processed acid catalyzed silicate thin films.

Structural properties of atactic polystyrene adsorbed onto solid surfaces.

PubMed

Tatek, Yergou B; Tsige, Mesfin

2011-11-07

In the present work, we are studying the local conformation of chains in a thin film of polystyrene adsorbed on a solid substrate by using atomistically detailed simulations. The simulations are carried out by using the readily available and massively parallel molecular dynamics code known as LAMMPS. In particular, a special emphasis is given to the density and orientation of side chains (which consist of phenyl groups and methylene units) at solid/polymer and polymer/vacuum interfaces. Three types of substrates were used in our study: α-quartz, graphite, and amorphous silica. Our investigation was restricted to atactic polystyrene. Our results show that the density and structural properties of side chains depend on the type of surface. An excess of phenyl rings is observed near the α-quartz substrate while the film adsorbed on graphite is depleted in C(6)H(5). Moreover, the orientation of the rings and methylene units on the substrate/film interface show a strong dependence on the type of the substrate, while the rings at the film/vacuum interface show a marked tendency to point outward, away from the film. The results we obtained are in a large part in good agreement with previous experimental and simulation results.

Mechanical properties of multilayered films using different nanoindenters.

PubMed

Fang, Te-Hua; Wang, Tong Hong; Wu, Jia-Hung

2010-07-01

The effects of interface, contact hardness, deformation, and adhesion of Al/Ni multilayered films under nanoindentation were investigated using molecular dynamics (MD) simulations. The results show that the indentation force of the sphere indenter is the largest among nanoindentations using sphere, cone, Vickers, or Berkovich type indenters at the same penetration depth. Force increasing, relaxation and adhesion took place during loading, holding depth and unloading, respectively. The interface occurred along the {111} (110) slip systems and the maximum width of the glide bands was about 1 nm. The reaction force and plastic energy of the indented films are also discussed.

Interface Modeling for Electro-Osmosis in Subgrade Structures

DTIC Science & Technology

2004-12-01

aggregate and different clays ( kaolinite , montmorillonite , limestone and quartz sands) created to simulate below grade structures. A direct current 30...Quartz Sand 100 Sieve Ca Montmorillonite Na Montmorillonite Kaolinite The test setup used a 0.45 water to cement ratio concrete cylinder... Kaolinite cell Figure 4. Measured pH for Concrete and Na Montmorillonite cell 4 Scaling occurred at the interface between the anode

Self-assembly of a thin highly reduced graphene oxide film and its high electrocatalytic activity

NASA Astrophysics Data System (ADS)

Bai, Yan-Feng; Zhang, Yong-Fang; Zhou, An-Wei; Li, Hai-Wai; Zhang, Yu; Luong, John H. T.; Cui, Hui-Fang

2014-10-01

A thin highly reduced graphene oxide (rGO) film was self-assembled at the dimethyl formamide (DMF)-air interface through evaporation-induced water-assisted thin film formation at the pentane-DMF interface, followed by complete evaporation of pentane. The thin film was transferred onto various solid substrates for film characterization and electrochemical sensing. UV-visible spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemistry techniques were used to characterize the film. An rGO film showing 82.8% of the transmittance at 550 nm corresponds to a few layers of rGO nanosheets. The rGO nanosheets cross-stack with each other, lying approximately in the plane of the film. An rGO film collected on a glassy carbon (GC) electrode exhibited improved electrical conductivity compared to GC, with the electrode charge-transfer resistance (Rct) reduced from 31 Ω to 22 Ω. The as-formed rGO/GC electrode was mechanically very stable, exhibiting significantly enhanced electrocatalytic activity to H2O2 and dopamine. Multiple layers of the rGO films on the GC electrode showed even stronger electrocatalytic activity to dopamine than that of the single rGO film layer. The controllable formation of a stable rGO film on various solid substrates has potential applications for nanoelectronics and sensors/biosensors.

Influence of Sulphur Impurities on the Interfacial Tension between Aluminium and Cryolite Alumina Melts

NASA Astrophysics Data System (ADS)

Korenko, Michal

2007-06-01

The interfacial tension (IFT) between aluminium and cryolite melts containing different salt additions (AlF3, NaF,Na2SO4) has been measured during electrolysis by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when a capillary, which is moved vertically down through the molten salt layer, passes through the metal/salt interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension is strongly dependent on the n(NaF)/n(AlF3) ratio. The addition of Na2SO4 decreases the IFT of the aluminium/electrolyte interface. We also found the different influence of the conditions of electrolysis on the IFT in systems with and without Na2SO4. In systems without Na2SO4 the IFT decreases with increasing current density, and in systems with Na2SO4 it increases.

PLASMA POLYMER FILMS AS ADHESION PROMOTING PRIMERS FOR ALUMINUM SUBSTRATES. PART I: CHARACTERIZATION OF FILMS AND FILM/SUBSTRATE INTERFACES

EPA Science Inventory

Plasma polymerized hexamethyldisiloxane (HMDSO) films (~800 Å in thickness) were deposited onto aluminum substrates (6111-T4 alloy) in radio frequency (RF) and microwave (MW) powered reactors to be used as primers for structural adhesive bonding. Processing variables such as sub...

New Cu(GeNx) film in barrierless metallization for LED heat dissipation

NASA Astrophysics Data System (ADS)

Lin, Chon-Hsin

2015-05-01

In this study, we explore new Cu(Ge) and Cu(GeNx) films for LED heat dissipation. The films are Cu-alloy seed layers, fabricated by co-sputtering Cu and Ge in an Ar or N2 atmosphere on either Ta/Al2O3 or polyimide substrates. The Cu alloy films are then annealed at 600 and 730 °C, respectively, for 1 h without notable Cu oxide formation at the Cu-Ta/Al2O3 interface. No Cu oxide is formed at the Cu-polyimide interface either after annealing the films at 310 °C for 1 h. The film formed atop an Al2O3 substrate contains a trace amount of GeNx and is thermally stable up to 730 °C, and the film formed atop a polyimide substrate is thermally stable up to 310 °C, both exhibiting a low resistivity and a high thermal conductivity. Such a thermal feature makes the Cu(GeNx) film a good candidate material in barrierless metallization for many industrial applications, such as LED heat sinks.

Communication: Distinguishing between bulk and interface-enhanced crystallization in nanoscale films of amorphous solid water.

PubMed

Yuan, Chunqing; Smith, R Scott; Kay, Bruce D

2017-01-21

The crystallization of amorphous solid water (ASW) nanoscale films was investigated using reflection absorption infrared spectroscopy. Two ASW film configurations were studied. In one case the ASW film was deposited on top of and capped with a decane layer ("sandwich" configuration). In the other case, the ASW film was deposited on top of a decane layer and not capped ("no cap" configuration). Crystallization of ASW films in the "sandwich" configuration is about eight times slower than in the "no cap." Selective placement of an isotopic layer (5% D 2 O in H 2 O) at various positions in an ASW (H 2 O) film was used to determine the crystallization mechanism. In the "sandwich" configuration, the crystallization kinetics were independent of the isotopic layer placement whereas in the "no cap" configuration the closer the isotopic layer was to the vacuum interface, the earlier the isotopic layer crystallized. These results are consistent with a mechanism whereby the decane overlayer suppresses surface nucleation and provide evidence that the observed ASW crystallization in "sandwich" films is the result of uniform bulk nucleation.

High enzymatic activity preservation with carbon nanotubes incorporated in urease-lipid hybrid Langmuir-Blodgett films.

PubMed

Caseli, Luciano; Siqueira, José Roberto

2012-03-27

The search for optimized architectures, such as thin films, for the production of biosensors has been challenged in recent decades, and thus, the understanding of molecular interactions that occur at interfaces is essential to improve the construction of nanostructured devices. In this study, we investigated the possibility of using carbon nanotubes in hybrid Langmuir-Blodgett (LB) films of lipids and urease to improve the catalytic performance of the immobilized enzyme. The molecular interactions were first investigated at the air-water interface with the enzyme adsorbed from the aqueous subphase onto Langmuir monolayers of dimyristoylphosphatidic acid (DMPA). The transfer to solid supports as LB films and the subsequent incorporation of carbon nanotubes in the hybrid film permitted us to evaluate how these nanomaterials changed the physical properties of the ultrathin film. Colorimetric measurments indicated that the presence of nanotubes preserved and enhanced the enzyme activity of the film, even after 1 month. These results show that the use of such hybrid films is promising for the development of biosensors with an optimized performance. © 2012 American Chemical Society

Protective Behavior of Poly(m-aminophenol) and Polypyrrole Coatings on Mild Steel

NASA Astrophysics Data System (ADS)

Yahaya, Sabrina M.; Harun, M. K.; Rosmamuhamadani, R.; Bonnia, N. N.; Ratim, S.

2018-01-01

Electrodeposition of polypyrrole (PPy) and poly (m-aminophenol) (PMAP) films on mild steel (MS) substrate was achieved in 0.3M oxalic acid solution and 0.3M NaOH, water:ethanol (70:30) solvent respectively using cyclic voltammetry technique. The morphology of the films constructed was determined by scanning electron microscope (SEM) while energy dispersive X-Ray analyzer (EDX) was used to establish the presence of organic PMAP and PPy film coating and its compositions. The corrosion performance of MS coated with both polymer films were investigated after 0.5 hours immersed in 0.5M NaCl aqueous solution by using polarization curves. It was found that PPy coating provides anodic protection while PMAP coating provides cathodic protection towards corrosion protection of mild steel substrate.

FAST TRACK COMMUNICATION Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbide

NASA Astrophysics Data System (ADS)

Rohrer, Jochen; Hyldgaard, Per

2010-12-01

We investigate the chemical composition and adhesion of chemical vapour deposited thin-film alumina on TiC using and extending a recently proposed nonequilibrium method of ab initio thermodynamics of deposition growth (AIT-DG) (Rohrer and Hyldgaard 2010 Phys. Rev. B 82 045415). A previous study of this system (Rohrer et al 2010 J. Phys.: Condens. Matter 22 015004) found that use of equilibrium thermodynamics leads to predictions of a non-binding TiC/alumina interface, despite its industrial use as a wear-resistant coating. This discrepancy between equilibrium theory and experiment is resolved by the AIT-DG method which predicts interfaces with strong adhesion. The AIT-DG method combines density functional theory calculations, rate-equation modelling of the pressure evolution of the deposition environment and thermochemical data. The AIT-DG method was previously used to predict prevalent terminations of growing or as-deposited surfaces of binary materials. Here we extend the method to predict surface and interface compositions of growing or as-deposited thin films on a substrate and find that inclusion of the nonequilibrium deposition environment has important implications for the nature of buried interfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Riley E.; Mangan, Niall M.; Li, Jian V.

The development of new thin-film photovoltaic (PV) absorbers is often hindered by the search for an optimal heterojunction contact; an unoptimized contact may be mistaken for poor quality of the underlying absorber, making it difficult to assess the reasons for poor performance. Therefore, quantifying the loss in device efficiency and open-circuit voltage (VOC) as a result of the interface is a critical step in evaluating a new material. In the present work, we fabricate thin-film PV devices using cuprous oxide (Cu2O), with several different n-type heterojunction contacts. Their current-voltage characteristics are measured over a range of temperatures and illumination intensitiesmore » (JVTi). We quantify the loss in VOC due to the interface and determine the effective energy gap at the interface. The effective interface gap measured by JVTi matches the gap measured by X-ray photoelectron spectroscopy, albeit with higher energy resolution and an order of magnitude faster. We discuss potential artifacts in JVTi measurements and areas where analytical models are insufficient. Applying JVTi to complete devices, rather than incomplete material stacks, suggests that it can be a quick, accurate method to assess the loss due to unoptimized interface band offsets in thin-film PV devices.« less

Direct Imaging and First Principles Studies of Si3N4/SiO2 Interface

NASA Astrophysics Data System (ADS)

Walkosz, Weronika; Klie, Robert; Ogut, Serdar; Mikijelj, Bilijana; Pennycook, Stephen; Idrobo, Juan C.

2010-03-01

It is well known that the composition of the integranular films (IGFs) in sintered polycrystalline silicon nitride (Si3N4) ceramics controls many of their physical and mechanical properties. A considerable effort has been made to characterize these films on the atomic scale using both experimental and theoretical methods. In this talk, we present results from a combined atomic-resolution Z-contrast and annular bright field imaging, electron energy-loss spectroscopy, as well as ab initio studies of the interface between β-Si3N4 (10-10) and SiO2 intergranular film. Our results show that O replaces N at the interface between the two materials in agreement with our theoretical calculations and that N is present in the SiO2 IGF. Moreover, they indicate the presence of atomic columns completing Si3N4 open rings, which have not been observed experimentally at the recently imaged Si3N4/rare-earth oxides interfaces, but have been predicted theoretically on bare Si3N4 surfaces. The structural and electronic variations at the Si3N4/SiO2 interface will be discussed in detail, focusing in particular on bonding characteristics.

High-Performance All-Solid-State Na-S Battery Enabled by Casting-Annealing Technology.

PubMed

Fan, Xiulin; Yue, Jie; Han, Fudong; Chen, Ji; Deng, Tao; Zhou, Xiuquan; Hou, Singyuk; Wang, Chunsheng

2018-04-24

Room-temperature all-solid-state Na-S batteries (ASNSBs) using sulfide solid electrolytes are a promising next-generation battery technology due to the high energy, enhanced safety, and earth abundant resources of both sodium and sulfur. Currently, the sulfide electrolyte ASNSBs are fabricated by a simple cold-pressing process leaving with high residential stress. Even worse, the large volume change of S/Na 2 S during charge/discharge cycles induces additional stress, seriously weakening the less-contacted interfaces among the solid electrolyte, active materials, and the electron conductive agent that are formed in the cold-pressing process. The high and continuous increase of the interface resistance hindered its practical application. Herein, we significantly reduce the interface resistance and eliminate the residential stress in Na 2 S cathodes by fabricating Na 2 S-Na 3 PS 4 -CMK-3 nanocomposites using melting-casting followed by stress-release annealing-precipitation process. The casting-annealing process guarantees the close contact between the Na 3 PS 4 solid electrolyte and the CMK-3 mesoporous carbon in mixed ionic/electronic conductive matrix, while the in situ precipitated Na 2 S active species from the solid electrolyte during the annealing process guarantees the interfacial contact among these three subcomponents without residential stress, which greatly reduces the interfacial resistance and enhances the electrochemical performance. The in situ synthesized Na 2 S-Na 3 PS 4 -CMK-3 composite cathode delivers a stable and highly reversible capacity of 810 mAh/g at 50 mA/g for 50 cycles at 60 °C. The present casting-annealing strategy should provide opportunities for the advancement of mechanically robust and high-performance next-generation ASNSBs.

Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

PubMed

Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

2015-07-29

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a suitable passivation layer to suppress oxidation in metal oxide thin films for enhanced lifetime in inverted organic solar cells.

Photoluminescence and anti-deliquesce of cesium iodide and its sodium-doped films deposited by thermal evaporation at high deposition rates

NASA Astrophysics Data System (ADS)

Hsu, Jin-Cherng; Chiang, Yueh-Sheng; Ma, Yu-Sheng

2013-03-01

Cesium iodide (CsI) and sodium iodide (NaI) are good scintillators due to their high luminescence efficiency. These alkali halides can be excited by ultra-violet or by ionizing radiation. In this study, CsI and its Na-doped films about 8 μm thick were deposited by thermal evaporation boat without heating substrates at high deposition rates of 30, 50, 70, 90, and 110 nm/sec, respectively. The as-deposited films were sequentially deposited a silicon dioxide film to protect from deliquesce. And, the films were also post-annealed in vacuum at 150, 200, 250, and 300 °C, respectively. We calculated the packing densities of the samples according to the measurements of Fourier transform infrared spectroscopy (FTIR) and observed the luminescence properties by photoluminescence (PL) system. The surfaces and cross sections of the films were investigated by scanning electron microscope (SEM). From the above measurements we can find the optimal deposition rate of 90 nm/sec and post-annealing temperature of 250 °C in vacuum for the asdeposited cesium iodide and its sodium-doped films.

SFG analysis of the molecular structures at the surfaces and buried interfaces of PECVD ultralow-dielectric constant pSiCOH: Reactive ion etching and dielectric recovery

NASA Astrophysics Data System (ADS)

Myers, John N.; Zhang, Xiaoxian; Huang, Huai; Shobha, Hosadurga; Grill, Alfred; Chen, Zhan

2017-05-01

Molecular structures at the surface and buried interface of an amorphous ultralow-k pSiCOH dielectric film were quantitatively characterized before and after reactive ion etching (RIE) and subsequent dielectric repair using sum frequency generation (SFG) vibrational spectroscopy and Auger electron spectroscopy. SFG results indicated that RIE treatment of the pSiCOH film resulted in a depletion of ˜66% of the surface methyl groups and changed the orientation of surface methyl groups from ˜47° to ˜40°. After a dielectric recovery process that followed the RIE treatment, the surface molecular structure was dominated by methyl groups with an orientation of ˜55° and the methyl surface coverage at the repaired surface was 271% relative to the pristine surface. Auger depth profiling indicated that the RIE treatment altered the top ˜25 nm of the film and that the dielectric recovery treatment repaired the top ˜9 nm of the film. Both SFG and Auger profiling results indicated that the buried SiCNH/pSiCOH interface was not affected by the RIE or the dielectric recovery process. Beyond characterizing low-k materials, the developed methodology is general and can be used to distinguish and characterize different molecular structures and elemental compositions at the surface, in the bulk, and at the buried interface of many different polymer or organic thin films.

Characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems.

PubMed

Bryant, M; Ward, M; Farrar, R; Freeman, R; Brummitt, K; Nolan, J; Neville, A

2014-04-01

This study presents the characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FI-IR) were utilised in order to assess the surface morphology of retrieved Metal-on-Metal Total Hip Replacements and surface chemistry of the films found on the surface. Gross slip, plastic deformation and directionality of the surface were extensively seen on the proximal surfaces of the retrievals. A more corrosive phenomenon was observed in the distal regions of the stem, demonstrating a seemingly intergranular attack. Tribochemical reactions were seen to occur within the stem-cement interfaces with tribofilms being observed on the femoral stem and counterpart PMMA bone cement. XPS, TEM-EDX and FT-IR analyses demonstrated that the films present in the stem surfaces were a complex mixture of chromium oxide and amorphous organic material. A comparison between current experimental and clinical literature has been conducted and findings from this study demonstrate that the formation and chemistry of films are drastically influenced by the type of wear or degradation mechanism. Films formed in the stem-cement interface are thought to further influence the biological environment outside the stem-cement interface due to the formation of Cr and O rich films within the interface whilst Co is free to migrate away. © 2013 Elsevier Ltd. All rights reserved.

Band alignment measurements at heterojunction interfaces in layered thin film solar cells & thermoelectrics

NASA Astrophysics Data System (ADS)

Fang, Fang

2011-12-01

Public awareness of the increasing energy crisis and the related serious environmental concerns has led to a significantly growing demand for alternative clean and renewable energy resources. Thin film are widely applied in multiple renewable energy devices owing to the reduced amount of raw materials and increase flexibility of choosing from low-cost candidates, which translates directly into reduced capital cost. This is a key driving force to make renewable technology competitive in the energy market. This thesis is focused on the measurement of energy level alignments at interfaces of thin film structures for renewable energy applications. There are two primary foci: II -VI semiconductor ZnSe/ZnTe thin film solar cells and Bi2Te3/Sb2Te3 thin film structures for thermoelectric applications. In both cases, the electronic structure and energy band alignment at interfaces usually controls the carrier transport behavior and determines the quality of the device. High-resolution photoemission spectroscopy (lab-based XPS & synchrotron-based UPS) was used to investigate the chemical and electronic properties of epitaxial Bi2Te3 and Sb2Te3 thin films, in order to validate the anticipated band alignment at interfaces in Bi 2Te3/Sb2Te3 superlattices as one favoring electron-transmission. A simple, thorough two-step treatment of a chemical etching in dilute hydrochloric acid solution and a subsequent annealing at ˜150°C under ultra-high vacuum environment is established to remove the surface oxides completely. It is an essential step to ensure the measurements on electronic states are acquired on stoichimetric, oxide-free clean surface of Bi 2Te3 and Sb2Te3 films. The direct measurement of valence band offsets (VBO) at a real Sb 2Te3/Bi2Te3 interface is designed based on the Kraut model; a special stacking film structure is prepared intentionally: sufficiently thin Sb2Te3 film on top of Bi2Te 3 that photoelectrons from both of them are collected simultaneously. From a combination of core levels and valence band ultraviolet photoemission spectra of the bulk materials as well as the heterojunction (Sb2Te 3/Bi2Te3), the VBO at p-type Sb2Te 3 and n-type Bi2Te3 is determined as 0.04 +/- 0.10 eV. Such a small energy offset is within the same magnitude of the thermal energy of kT, at room temperature. The motivation for the II-VI ZnTe-based thin film solar cell derives from the need to identify and overcome performance-limiting properties related to the processing of film deposition using close space sublimation (CSS). Chemical and electronic properties of the CSS grown ZnTe/ZnSe films were studied in x-ray diffraction, scanning electron microscopy and photoemission spectroscopy. Specifically, Se oxide was observed on the ZnSe surface, the removal of this oxide generated apparent offsets in the valence band and hence the alignment at the heterojunction energy diagram. Processing steps to mitigate oxidation yielded the best cells. Film structure was studied on the dependence of growth time; physical film damage is found during the initial stages when depositing ZnTe on a grown ZnSe film. Preliminary studies of films grown by evaporation and their characterizations are presented at last. In this thesis, a better understanding of the electronic structure at interfaces is built in two different thin film devices, and the resulting band energy diagram of the corresponding devices offered effective feedback in materials and device.The problem of energy equilibrium in the human body has received a great deal.

Polysaccharide/Surfactant complexes at the air-water interface - effect of the charge density on interfacial and foaming behaviors.

PubMed

Ropers, M H; Novales, B; Boué, F; Axelos, M A V

2008-11-18

The binding of a cationic surfactant (hexadecyltrimethylammonium bromide, CTAB) to a negatively charged natural polysaccharide (pectin) at air-solution interfaces was investigated on single interfaces and in foams, versus the linear charge densities of the polysaccharide. Besides classical methods to investigate polymer/surfactant systems, we applied, for the first time concerning these systems, the analogy between the small angle neutron scattering by foams and the neutron reflectivity of films to measure in situ film thicknesses of foams. CTAB/pectin foam films are much thicker than the pure surfactant foam film but similar for high- and low-charged pectin/CTAB systems despite the difference in structure of complexes at interfaces. The improvement of the foam properties of CTAB bound to pectin is shown to be directly related to the formation of pectin-CTAB complexes at the air-water interface. However, in opposition to surface activity, there is no specific behavior for the highly charged pectin: foam properties depend mainly upon the bulk charge concentration, while the interfacial behavior is mainly governed by the charge density of pectin. For the highly charged pectin, specific cooperative effects between neighboring charged sites along the chain are thought to be involved in the higher surface activity of pectin/CTAB complexes. A more general behavior can be obtained at lower charge density either by using a low-charged pectin or by neutralizing the highly charged pectin in decreasing pH.

Interface Energy Coupling between β-tungsten Nanofilm and Few-layered Graphene

DOE PAGES

Han, Meng; Yuan, Pengyu; Liu, Jing; ...

2017-09-22

We report the thermal conductance induced by few-layered graphene (G) sandwiched between β-phase tungsten (β-W) films of 15, 30 and 40 nm thickness. Our differential characterization is able to distinguish the thermal conductance of β-W film and β-W/G interface. The cross-plane thermal conductivity (k) of β-W films is determined at 1.69~2.41 Wm -1K -1 which is much smaller than that of α-phase tungsten (174 Wm -1K -1). This small value is consistent with the large electrical resistivity reported for β-W in literatures and in this work. The β-W/β-W and β-W/G interface thermal conductance (GW/W and GW/G) are characterized and comparedmore » using multilayered β-W films with and without sandwiched graphene layers. The average GW/W is found to be at 280 MW m -2K -1. GW/G features strong variation from sample to sample, and has a lower-limit of 84 MW m -2K -1, taking into consideration of the uncertainties. This is attributed to possible graphene structure damage and variation during graphene transfer and W sputtering. The difference between G2W/G and GW/W uncovers the finite thermal resistance induced by the graphene layer. Compared with up-to-date reported graphene interface thermal conductance, the β-W/G interface is at the high end in terms of local energy coupling.« less

Interface Energy Coupling between β-tungsten Nanofilm and Few-layered Graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Meng; Yuan, Pengyu; Liu, Jing

We report the thermal conductance induced by few-layered graphene (G) sandwiched between β-phase tungsten (β-W) films of 15, 30 and 40 nm thickness. Our differential characterization is able to distinguish the thermal conductance of β-W film and β-W/G interface. The cross-plane thermal conductivity (k) of β-W films is determined at 1.69~2.41 Wm -1K -1 which is much smaller than that of α-phase tungsten (174 Wm -1K -1). This small value is consistent with the large electrical resistivity reported for β-W in literatures and in this work. The β-W/β-W and β-W/G interface thermal conductance (GW/W and GW/G) are characterized and comparedmore » using multilayered β-W films with and without sandwiched graphene layers. The average GW/W is found to be at 280 MW m -2K -1. GW/G features strong variation from sample to sample, and has a lower-limit of 84 MW m -2K -1, taking into consideration of the uncertainties. This is attributed to possible graphene structure damage and variation during graphene transfer and W sputtering. The difference between G2W/G and GW/W uncovers the finite thermal resistance induced by the graphene layer. Compared with up-to-date reported graphene interface thermal conductance, the β-W/G interface is at the high end in terms of local energy coupling.« less

Confined methane-water interfacial layers and thickness measurements using in situ Raman spectroscopy.

PubMed

Pinho, Bruno; Liu, Yukun; Rizkin, Benjamin; Hartman, Ryan L

2017-11-07

Gas-liquid interfaces broadly impact our planet, yet confined interfaces behave differently than unconfined ones. We report the role of tangential fluid motion in confined methane-water interfaces. The interfaces are created using microfluidics and investigated by in situ 1D, 2D and 3D Raman spectroscopy. The apparent CH 4 and H 2 O concentrations are reported for Reynolds numbers (Re), ranging from 0.17 to 8.55. Remarkably, the interfaces are comprised of distinct layers of thicknesses varying from 23 to 57 μm. We found that rarefaction, mixture, thin film, and shockwave layers together form the interfaces. The results indicate that the mixture layer thickness (δ) increases with Re (δ ∝ Re), and traditional transport theory for unconfined interfaces does not explain the confined interfaces. A comparison of our results with thin film theory of air-water interfaces (from mass transfer experiments in capillary microfluidics) supports that the hydrophobicity of CH 4 could decrease the strength of water-water interactions, resulting in larger interfacial thicknesses. Our findings help explain molecular transport in confined gas-liquid interfaces, which are common in a broad range of societal applications.

Orientation Control of Interfacial Magnetism at La 0.67Sr 0.33MnO 3/SrTiO 3 Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Er-Jia; Charlton, Timothy; Ambaye, Haile

Understanding the magnetism at the interface between a ferromagnet and an insulator is essential because the commonly posited magnetic “dead” layer close to an interface can be problematic in magnetic tunnel junctions. Previously, degradation of the magnetic interface was attributed to charge discontinuity across the interface. In this paper, the interfacial magnetism was investigated using three identically prepared La 0.67Sr 0.33MnO 3 (LSMO) thin films grown on different oriented SrTiO 3 (STO) substrates by polarized neutron reflectometry. In all cases the magnetization at the LSMO/STO interface is larger than the film bulk. We show that the interfacial magnetization is largestmore » across the LSMO/STO interfaces with (001) and (111) orientations, which have the largest net charge discontinuities across the interfaces. In contrast, the magnetization of LSMO/STO across the (110) interface, the orientation with no net charge discontinuity, is the smallest of the three orientations. We show that a magnetically degraded interface is not intrinsic to LSMO/STO heterostructures. Finally, the approach to use different crystallographic orientations provides a means to investigate the influence of charge discontinuity on the interfacial magnetization.« less

Orientation Control of Interfacial Magnetism at La 0.67Sr 0.33MnO 3/SrTiO 3 Interfaces

DOE PAGES

Guo, Er-Jia; Charlton, Timothy; Ambaye, Haile; ...

2017-05-16

Understanding the magnetism at the interface between a ferromagnet and an insulator is essential because the commonly posited magnetic “dead” layer close to an interface can be problematic in magnetic tunnel junctions. Previously, degradation of the magnetic interface was attributed to charge discontinuity across the interface. In this paper, the interfacial magnetism was investigated using three identically prepared La 0.67Sr 0.33MnO 3 (LSMO) thin films grown on different oriented SrTiO 3 (STO) substrates by polarized neutron reflectometry. In all cases the magnetization at the LSMO/STO interface is larger than the film bulk. We show that the interfacial magnetization is largestmore » across the LSMO/STO interfaces with (001) and (111) orientations, which have the largest net charge discontinuities across the interfaces. In contrast, the magnetization of LSMO/STO across the (110) interface, the orientation with no net charge discontinuity, is the smallest of the three orientations. We show that a magnetically degraded interface is not intrinsic to LSMO/STO heterostructures. Finally, the approach to use different crystallographic orientations provides a means to investigate the influence of charge discontinuity on the interfacial magnetization.« less

Synthesis and characterization of sputtered titanium nitride as a nucleation layer for novel neural electrode coatings

NASA Astrophysics Data System (ADS)

Sait, R. A.; Cross, R. B. M.

2017-12-01

A growing demand for chronically implantable electrodes has led to a search for the most suitable neural electrode interface material. Nobel metals such as platinum (Pt) are inadequate for electrode/neuron interfaces at small scales due to their poor electrochemical properties, low charge injection and high charge density per unit area. Titanium nitride (TiN) has been implemented in neural electrodes application due to its outstanding properties. In this work, TiNx films were deposited by non-reactive radio frequency (RF) magnetron sputtering towards the development of a novel TiN nanowires (NWs) neural interface. Although, there is substantial work on this material, its growth using non-reactive RF magnetron sputtering has not been reported previously and optimised towards the growth of TiN NWs and their use in neural interface applications. The sputtering parameters of RF power and argon (Ar) flow rate were varied in order to investigate their effects on the structural, electrical and electrochemical properties of the TiN films. A dense film morphology was observed in the scanning electron microscopy (SEM) images of TiN thin films showing a columnar structure. The film preferential orientation was changed between (200) and (111) with Ar flow rate due to the variation of the kinetic energy (KE) of the sputtered atoms. The crystallites size obtained were in the range of 13-95 nm. Surface roughness was found to increase from 0.69 to 1.95 nm as Ar flow rate increased. TiNx films showed a good electrical resistivity of 228 μΩ cm. Stoichiometry was found to vary with sputtering conditions in which the nitrogen content was found to deplete from the film at low Ar flow rate. The electrochemical behaviour of TiN films were characterised and the highest capacitance value obtained was 0.416 mF/cm2. From the results, it can be suggested that TiN thin film can be easily optimised to act as a nucleation layer for the growth of nanowires.

Graphene as a thin-film catalyst booster: graphene-catalyst interface plays a critical role.

PubMed

Chae, Sieun; Jin Choi, Won; Sang Chae, Soo; Jang, Seunghun; Chang, Hyunju; Lee, Tae Il; Kim, Youn Sang; Lee, Jeong-O

2017-12-08

Due to its extreme thinness, graphene can transmit some surface properties of its underlying substrate, a phenomenon referred to as graphene transparency. Here we demonstrate the application of the transparency of graphene as a protector of thin-film catalysts and a booster of their catalytic efficiency. The photocatalytic degradation of dye molecules by ZnO thin films was chosen as a model system. A ZnO thin film coated with monolayer graphene showed greater catalytic efficiency and long-term stability than did bare ZnO. Interestingly, we found the catalytic efficiency of the graphene-coated ZnO thin film to depend critically on the nature of the bottom ZnO layer; graphene transferred to a relatively rough, sputter-coated ZnO thin film showed rather poor catalytic degradation of the dye molecules while a smooth sol-gel-synthesized ZnO covered with monolayer graphene showed enhanced catalytic degradation. Based on a systematic investigation of the interface between graphene and ZnO thin films, we concluded the transparency of graphene to be critically dependent on its interface with a supporting substrate. Graphene supported on an atomically flat substrate was found to efficiently transmit the properties of the substrate, but graphene suspended on a substrate with a rough nanoscale topography was completely opaque to the substrate properties. Our experimental observations revealed the morphology of the substrate to be a key factor affecting the transparency of graphene, and should be taken into account in order to optimally apply graphene as a protector of catalytic thin films and a booster of their catalysis.

Photo-crystallization in a-Se layer structures: Effects of film-substrate interface-rigidity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindberg, G. P.; Gross, N.; Weinstein, B. A.

Amorphous selenium (a-Se) films deposited on rigid substrates can undergo photo-induced crystallization (PC) even at temperatures (T) well below the glass transition, T{sub g} ∼ 313 K. Substrate-generated shear strain is known to promote the PC process. In the present work, we explore the influence of different substrates (Si and glass), and different film-layer-substrate combinations, on the PC in a variety of a-Se films and film-structures. The intermediate layers (indium tin oxide and polyimide) are chosen to promote conductivity and/or to be a buffer against interface strain in structures of interest for digital imaging applications. The PC characteristics in these samples are evaluatedmore » and compared using optical microscopy, atomic-force microscopy, Raman mapping, and T-dependent Raman spectroscopy. Both the presence of a soft intermediate layer, and the thermal softening that occurs for T increasing through T{sub g}, inhibit the tendency for the onset of PC. The extensive PC mapping results in the wide range of samples studied here, as well as the suppression of PC near T{sub g} in this array of samples, strongly support the generality of this behavior. As a consequence, one may expect that the stability of a-Se films against PC can be enhanced by decreasing the rigidity of the film-substrate interface. In this regard, advanced film structures that employ flexible substrates, soft intermediate layers, and/or are designed to be operated near T{sub g} should be explored.« less

Effects of temperature, pH, and ionic strength on the adsorption of nanoparticles at liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

Ferdous, Sultana; Ioannidis, Marios A.; Henneke, Dale E.

2012-05-01

The effects of temperature, pH and sodium chloride (NaCl) concentration on the equilibrium and dynamic interfacial tension (IFT) of 4.4-nm gold nanoparticles capped with n-dodecanethiol at hydrocarbon-water interfaces was studied. The pendant drop technique was used to study the adsorption properties of these nanoparticles at the hexane-water and nonane-water interfaces. The physical size of the gold nanoparticles was determined by TEM image analysis. The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. These findings have implications for the self-assembly of functionalized gold nanoparticles at liquid-liquid interfaces.

Film bonded fuel cell interface configuration

DOEpatents

Kaufman, Arthur; Terry, Peter L.

1985-01-01

An improved interface configuration for use between adjacent elements of a fuel cell stack. The interface is impervious to gas and liquid and provides resistance to corrosion by the electrolyte of the fuel cell. A multi-layer arrangement for the interface provides bridging electrical contact with a hot-pressed resin filling the void space.

Process for making film-bonded fuel cell interfaces

DOEpatents

Kaufman, Arthur; Terry, Peter L.

1990-07-03

An improved interface configuration for use between adjacent elements of a fuel cell stack. The interface is impervious to gas and liquid and provides resistance to corrosion by the electrolyte of the fuel cell. A multi-layer arrangement for the interface provides bridging electrical contact with a hot-pressed resin filling the void space.

Interface spins in polycrystalline FeMn/Fe bilayers with small exchange bias

NASA Astrophysics Data System (ADS)

Pires, M. J. M.

2018-04-01

The magnetic moments at the interface between ferromagnetic and antiferromagnetic layers play a central role in exchange biased systems, but their behavior is still not completely understood. In this work, the FeMn/Fe interface in polycrystalline thin films has been studied using conversion electron Mössbauer spectroscopy (CEMS), magneto-optic Kerr effect (MOKE) and micromagnetic simulations. Samples were prepared with 57Fe layers at two distinct depths in order to probe the interface and bulk behaviors. At the equilibrium, the interface moments are randomly oriented while the bulk of the Fe layer has an in-plane magnetic anisotropy. Several models for the interface and anisotropies of the layers were used in the simulations of spin configurations and hysteresis loops. From the whole set of simulations, one can conclude the direct analysis of hysteresis curves is not enough to infer whether the interface has a configuration with spins tilted out of the film plane at equilibrium since different choices of parameters provide similar curves. The simulations have also shown the occurrence of spin clusters at the interface is compatible with CEMS and MOKE measurements.

Realistic absorption coefficient of ultrathin films

NASA Astrophysics Data System (ADS)

Cesaria, M.; Caricato, A. P.; Martino, M.

2012-10-01

Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film-substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film-substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films.

Antibacterial performance on plasma polymerized heptylamine films loaded with silver nanoparticles

NASA Astrophysics Data System (ADS)

Lin, Yu-Chun; Lin, Chia-Chun; Lin, Chih-Hao; Wang, Meng-Jiy

2017-01-01

The antibacterial performance of the plasma-polymerized (pp) heptylamine thin films loaded with silver nanoparticles was evaluated against the colonization of Escherichia coli and Staphylococcus aureus. The properties including the thickness and chemical composition of the as deposited HApp films were modulated by adjusting plasma parameters. The acquired results showed that the film thickness was controlled in the range of 20 to 400 nm by adjusting deposition time. The subsequent immersion of the HApp thin films in silver nitrate solutions result in the formation of amine-metal complexes, in which the silver nanoparticles were reduced directly on the matrices to form Ag@HApp. The reduction reaction of silver was facilitated by applying NaBH4 as a reducing agent. The results of physicochemical analyses including morphological analysis and ellipsometry revealed that the silver nanoparticles were successfully reduced on the HApp films, and the amount of reduced silver was closely associated which the thickness of the plasma-polymerized films, the concentration of applied metal ions solutions, and the time of immobilization. Regarding the antibacterial performance, the Ag@HApp films reduced by NaBH4 showed antibacterial abilities of 70.1 and 68.2% against E. coli and S. aureus, respectively.

Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguirre, B.; Vemuri, R. S.; Zubia, David

2011-01-01

Hafnium oxide (HfO₂) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO₂ ceramic target has been employed for sputtering while varying the Ts from room temperature to 500⁰C during deposition. The effect of Ts on the growth and microstructure of deposited HfO₂ films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition ofmore » the HfO₂ films. Structural characterization indicates that the HfO₂ films grown at Ts<200 ⁰C are amorphous while films grown at Ts>200 ⁰C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ⁰C. Nanocrystalline HfO₂ films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO₂ films. An interface layer (IL) formation occurs due to reaction at the HfO₂-Si interface for HfO₂ films deposited at Ts>200 ⁰C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO₂-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.« less

Physicochemical signatures of natural surfactant sea films from coastal Middle Adriatic stations

NASA Astrophysics Data System (ADS)

Frka, Sanja; Pogorzelski, Stanislaw; Kozarac, Zlatica; Ćosović, Božena

2013-04-01

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea surface microlayer (SSM) as a top layer of the sea surface represents natural interface between the atmosphere and ocean. Although < 1 mm in thickness the SML plays a key role in the global biogeochemical cycling because all gaseous, liquid and particulate materials must pass through this interface when exchanging between the ocean and the atmosphere. The SSM thus represents a very important driver enhancing air-water exchange processes. A variety of natural and anthropogenic organic compounds, particularly those which are surface active (SA) are generally enriched in the SML. It is widely acknowledged that the SSM is complex matrix of SA organics as carbohydrates, proteins, lipids and humic substances. Although lipid material is much less abundant than carbohydrates and proteins in the SML, their contribution to surface activity may be disproportionately large. The surfactant films at the air-sea interface change its physicochemical properties reducing air-sea exchange possesses by impeding molecular diffusion across the interface and influencing the hydrodynamic characteristics of water motion at the interface. Various biological, chemical and physical processes lead to the alteration of the film chemical composition, surface physical properties, surface concentration and spatial distribution of film-forming components. Instead of analyzing its chemical composition, it should be possible to scale the SML surface pressure-area (π-A) isotherms in terms of structural parameters which appear to be a sensitive and quantitative measure of the film physicochemical composition, surface concentration and miscibility of its film-forming components. We will present a large data set obtained by electrochemical and monolayer techniques, accompanied with the novel scaling approach for physicochemical characterization of SA substances of the natural microlayers from coastal Middle Adriatic stations including saline Rogoznica Lake and Krka river estuarine station. Higher primary production during late spring-early autumn is reflected in the presence of microlayers of higher surfactant activity containing on average molecules of lower molecular masses (Mw=0.65±0.27 kDa) and higher miscibility (y=6.46±1.33) and elasticity (E=18.33±2.02 mN/m) modulus in comparison to structural parameters (average Mw=2.15±1.58 kDa; y=3.51±1.46; E=6.41±1.97 mN/m) obtained for microlayers from period of lower organic matter production. Higher inhibition effect on the reduction process of cadmium ions is observed for natural microlayers abundant with SA material from more productive period. This kind of distribution is explained as the consequence of competitive adsorption of hydrophobic lipid-like substances of lower Mw which highly influence the surface structural properties of natural air-water interface forming there segregated surface films during more productive period. This study will offer different perspective on contemporary SML concept taking into account the lipids that act as end-members highly influencing seasonal change of SA concentration and surface structural properties of natural films at the air-water interface.

Effect of post-treatments and concentration of cotton linter cellulose nanocrystals on the properties of agar-based nanocomposite films.

PubMed

Oun, Ahmed A; Rhim, Jong-Whan

2015-12-10

Cellulose nanocrystals (CNCs) were prepared by acid hydrolysis of cotton linter pulp fibers and three different purification methods, i.e., without post purification (CNC1), dialyzed against distilled water (CNC2), and neutralized with NaOH (CNC3), and their effect on film properties was evaluated by preparation of agar/CNCs composite films. All the CNCs were rod in shape with diameter of 15-50 nm and length of 210-480 nm. FTIR result indicated that there was no distinctive differences in the chemical structure between CNCs and cotton linter cellulose fiber. No significant relationship was observed between the sulfate content and crystallinity index of CNCs. The CNC3 showed higher thermal stability than the other type of CNCs due to the less adverse effect on the thermal stability of sulfate groups induced by the neutralization with NaOH. The tensile strength (TS) of agar film increased by 15% with incorporation of 5 wt% of CNC3, on the contrary, it decreased by 10% and 15% with incorporation of CNC1 and CNC2, respectively. Other performance properties of agar/CNCs composite films such as optical and water vapor barrier properties showed that the CNC3 was more effective filler than the other CNCs. In the range of concentration of CNC3 tested (1-10 wt%), inclusion of 5 wt% of CNC3 was the maximum concentration for improving or maintaining film properties of the composite films. The neutralization of acid hydrolyzed cellulose using NaOH was simple and convenient for the preparation of CNC and bionanocomposite films. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of confinement on the crystalline microstructure of polymer: fullerene bulk heterojunctions

DOE PAGES

Ashraf, A.; Dissanayake, D. M. N. M.; Eisaman, M. D.

2015-07-01

We investigate the effect of confinement on the coherence length and the crystalline microstructure of the polymer component of polymer: fullerene bulk heterojunction thin films using grazing incidence wide angle x-ray scattering. We find that the polymer crystallite size decreases and the alignment of the molecules along the surface normal increases, as the thin-film thickness is reduced from 920nm to < 20nm and approaches the thin-film confinement regime. Furthermore, we find that the polymer crystallite size near the surface (air interface) is lower than the crystallite size in the bulk or the bottom (substrate interface) of bulk heterojunction films thickermore » than the confinement regime. Variation in polymer crystallite size can cause changes in charge carrier mobility and recombination rates, which in turn affect the performance of bulk heterojunction thin film devices such as photovoltaics and photodetectors« less

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction.

PubMed

Sokolowski-Tinten, K; Shen, X; Zheng, Q; Chase, T; Coffee, R; Jerman, M; Li, R K; Ligges, M; Makasyuk, I; Mo, M; Reid, A H; Rethfeld, B; Vecchione, T; Weathersby, S P; Dürr, H A; Wang, X J

2017-09-01

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.

Electron-lattice energy relaxation in laser-excited thin-film Au-insulator heterostructures studied by ultrafast MeV electron diffraction

PubMed Central

Sokolowski-Tinten, K.; Shen, X.; Zheng, Q.; Chase, T.; Coffee, R.; Jerman, M.; Li, R. K.; Ligges, M.; Makasyuk, I.; Mo, M.; Reid, A. H.; Rethfeld, B.; Vecchione, T.; Weathersby, S. P.; Dürr, H. A.; Wang, X. J.

2017-01-01

We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels. PMID:28795080

Centrifugation-assisted Assembly of Colloidal Silica into Crack-Free and Transferrable Films with Tunable Crystalline Structures

PubMed Central

Fan, Wen; Chen, Min; Yang, Shu; Wu, Limin

2015-01-01

Self-assembly of colloidal particles into colloidal films has many actual and potential applications. While various strategies have been developed to direct the assembly of colloidal particles, fabrication of crack-free and transferrable colloidal film with controllable crystal structures still remains a major challenge. Here we show a centrifugation-assisted assembly of colloidal silica spheres into free-standing colloidal film by using the liquid/liquid interfaces of three immiscible phases. Through independent control of centrifugal force and interparticle electrostatic repulsion, polycrystalline, single-crystalline and quasi-amorphous structures can be readily obtained. More importantly, by dehydration of silica particles during centrifugation, the spontaneous formation of capillary water bridges between particles enables the binding and pre-shrinkage of the assembled array at the fluid interface. Thus the assembled colloidal films are not only crack-free, but also robust and flexible enough to be easily transferred on various planar and curved substrates. PMID:26159121

Tailoring of the soft magnetic property and uniaxial anisotropy of magnetostrictive films by interlayer

NASA Astrophysics Data System (ADS)

Wen, Dandan; Bai, Feiming; Wang, Yicheng; Zhong, Zhiyong; Zhang, Huaiwu

2013-05-01

Laminated amorphous FeSiBC films with various spacer layers, including Cu, Co0.45Cu0.55, Co0.8Cu0.2, and CoFe, were prepared in order to study the effect of interface structure and magnetic exchange interaction on the magnetic softness and uniaxial anisotropy of multilayered film. It is found that laminating FeSiBC film with thin nonmagnetic or weak magnetic spacers yields much lower coercivity and higher remanent magnetization than those with magnetic spacers. Optimal films with the desired properties of Hc ˜ 1.5 Oe, Mr/Ms = 95%, and Hk ˜ 16 Oe were obtained. Therefore, it is confirmed that the exchange interaction constant of spacer layer plays a more important role than that of interface structure. Furthermore, laminating FeSiBC with nonmagnetic layers only slightly changes magnetostrictive coefficient.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

DOE PAGES

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter; ...

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behavior, large changes in metal-insulator transition temperatures, or enhanced catalytic activity. Here in this paper, we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In 2O 3 films grown on ionically conducting Y 2O 3-stabilized ZrO 2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygenmore » vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behavior is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kannan Selvaraj, Sathees; Feinerman, Alan; Takoudis, Christos G., E-mail: takoudis@uic.edu

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac){sub 2}], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure,more » refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnO{sub x}–Si interface. The resistivity of the SnO{sub x} films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac){sub 2} as tin precursor to deposit conducting ALD SnO{sub x} thin films on a silicon surface, with clean interface and no formation of undesired SiO{sub 2} or other interfacial reaction products, for transparent conducting oxide applications.« less

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co{sub 20}Fe{sub 60}B{sub 20}/MgO/Ta films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Minghua, E-mail: mhli@ustb.edu.cn; Department of Electrical Engineering, University of California, Los Angeles, California 90095; Lu, Jinhui

2016-04-15

We studied the thermal stability of perpendicular magnetic anisotropy (PMA) in Ta/Mo/CoFeB/MgO/Ta films with and without inserted Mo layers. In the absence of a Mo layer, the films show PMA at annealing temperatures below 300 °C. On the other hand, the insertion of a Mo layer preserves PMA at annealing temperatures of up to 500 °C; however, a higher annealing temperature leads to the collapse of PMA. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) were used to study the microstructure of the films to understand the deterioration of PMA. The XPS results show that the segregation ofmore » Ta is partly suppressed by inserting a Mo layer. Once inserted, Mo does not remain at the interface of Ta and CoFeB but migrates to the surface of the films. The HRTEM results show that the crystallization of the MgO (001) texture is improved owing to the higher annealing temperature of the Mo inserted sample. A smooth and clear CoFeB/MgO interface is evident. The inserted Mo layer not only helps to obtain sharper and smoother interfaces but also contributes to the crystallization after the higher annealing temperature of films.« less

Investigation of Oxygen and Hydrogen Associated Charge Trapping and Electrical Characteristics of Silicon Nitride Films for Mnos Devices.

NASA Astrophysics Data System (ADS)

Xu, Dan

Silicon nitride (Si_3N _4) and silicon oxynitride (SiO _{rm x}N_ {rm y}) films in the form of metal -nitride-oxide-silicon (MNOS) structures were investigated to determine the correlation between their electrical characteristics and the nature of the chemical bonding so as to provide guidelines for the next generation of nonvolatile memory devices. The photoionization cross section of electron traps in the oxynitride films of MNOS devices were also measured as a function photon energy and oxygen concentration of the silicon oxynitride films. An effective photoionization cross section associated with electron traps was determined to be between 4.9 times 10 ^{-19} cm^2 to 10.8 times 10^ {-19} cm^2 over the photon energy of 2.06 eV to 3.1 eV for silicon oxynitride films containing 7 atomic % to 17 atomic % of oxygen. The interface state density of metal-nitride-oxide -silicon (MNOS) devices was investigated as a function of processing conditions. The interface state density around the midgap of the oxide-silicon interface of the MNOS structures for deposition temperature between 650^ circC to 850^circC increased from 1.1 to 8.2 times 10 ^{11} cm^ {-2}eV^{-1}, for as-deposited silicon nitride films; but decreased from 5.0 to 3.5 times 10^ {11} cm^{-2} eV^{-1}, for films annealed in nitrogen at 900^circC for 60 minutes; and further decreased and remained constant at 1.5 times 10^{11 } cm^{-2}eV ^{-1}, for films which were further annealed in hydrogen at 900^ circC for an additional 60 minutes. The interface state density increase was due to an increase in the loss of hydrogen at the interfacial region and also due to an increase in the thermal stress caused by differences in thermal expansion coefficients of silicon nitride and silicon dioxide films at higher deposition temperatures. The interface state density was subject to two opposing influences; an increase by thermal stress, and a reduction by hydrogen compensation of these states. The photocurrent-voltage (photoI-V) technique in combination with internal photo-electric technique were employed to determine the trapped charge density and its centroid as a function of processing conditions. Results showed that the trapped charge density was of the order of 10^{18} cm ^{-3}. However, the charge trapping density increased about 30% as the atomic percentage of hydrogen decreased from 6 to 2 atomic %.

Origin of thickness dependence of structural phase transition temperatures in BiFeO 3 thin films

DOE PAGES

Yang, Yongsoo; Beekman, Christianne; Siemons, Wolter; ...

2016-03-28

In this study, two structural phase transitions are investigated in highly strained BiFeO 3 thin films grown on LaAlO 3 substrates, as a function of film thickness and temperature via synchrotron x-ray diffraction. Both transition temperatures (upon heating: monoclinic MC to monoclinic MA, and MA to tetragonal) decrease as the film becomes thinner. The existence of an interface layer at the film-substrate interface, deduced from half-order peak intensities, contributes to this behavior only for the thinnest samples; at larger thicknesses (above a few nanometers) the temperature dependence can be understood in terms of electrostatic considerations akin to size effects inmore » ferroelectric phase transitions, but observed here for structural phase transitions within the ferroelectric phase and related to the rearrangement rather than the formation of domains. For ultra-thin films, the tetragonal structure is stable at all investigated temperatures (down to 30 K).« less

Excellent Brightness with Shortening Lifetime of Textured Zn2SiO4:Mn2+ Phosphor Films on Quartz Glass

NASA Astrophysics Data System (ADS)

Park, Jehong; Park, Kwangwon; Lee, Jaebum; Kim, Jongsu; Kim, Seongsin Margaret; Kung, Patrick

2010-04-01

Green-emissive textured Zn2SiO4:Mn2+ phosphor films were fabricated by the thermal diffusion of ZnO:Mn on quartz glass. The Zn2SiO4:Mn2+ phosphor films became textured along several hexagonal directions and their chemical composition was continuously graded at the interface. The decay time of Mn2+ was as short as 4.4 ms, and the optical transition probability of the films defined as the inverse of decay time showed a strong correlation with film texture degree as a function of annealing temperature. The brightest Zn2SiO4:Mn2+ film showed a photoluminescent brightness as high as 65% compared with a commercial Zn2SiO4:Mn2+ phosphor powder screen and a maximum absolute transparency of 70%. These excellent optical properties are explained by the combination of the unique textured structure and continuous grading of the Zn2SiO4:Mn2+ chemical composition at the interface.

X-ray photoelectron spectroscopy study of radiofrequency-sputtered refractory compound steel interfaces

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Brainard, W. A.

1978-01-01

Radiofrequency sputtering was used to deposit Mo2C, Mo2B5, and MoSi2 coatings on 440C steel substrates. Both sputter etched and preoxidized substrates were used, and the films were deposited with and without a substrate bias of -300 V. The composition of the coatings was measured as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. In the interfacial region there was evidence that bias produced a graded interface in Mo2B5 but not in Mo2C. Oxides of iron and of all film constituents except carbon were presented in all cases but the iron oxide concentration was higher and the layer thicker on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 film. The presence of mixed oxides correlates with enhanced film adhesion.

Gallium arsenide single crystal solar cell structure and method of making

NASA Technical Reports Server (NTRS)

Stirn, Richard J. (Inventor)

1983-01-01

A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films.

PubMed

Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E; Alford, Neil McN

2015-01-07

The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Mingyuan; Mead, James; Wu, Yueqin

In this study, a nanoindentation-based microcantilever bending technique was utilized to investigate the interfacial properties of a β-Mg{sub 17}Al{sub 12}/AZ91 Mg alloy film/substrate system under tensile loading conditions. Finite element analysis (FEA) was first undertaken to optimise the design of cantilever structures for inducing high tensile stresses at the interface. Cantilevers consisting of a necked region or notch at the interface were determined to be the most successful designs. Microcantilevers containing the β-Mg{sub 17}Al{sub 12}/AZ91 interface were then made using focused ion beam (FIB) milling technique. Necks were made in the cantilevers to intensify the tension at the interface andmore » notches were used to introduce a stress concentration to the interface. During bending, the cantilevers were deflected to failure. Subsequent analysis of the deformed cantilevers using electron microscopies revealed that plastic deformation, and subsequent ductile rupture, of the AZ91 phase was the dominant failure mechanism. When the β-Mg{sub 17}Al{sub 12}/AZ91 film/substrate system was subjected to tension, the softer AZ91 phase failed prior to interfacial delamination, demonstrating that the strength of the interface exceeded the stresses that caused ductile failure in the substrate material. - Highlights: •Microcantilever bending was used to study the property of film/substrate interface. •FEA was used to optimise cantilever design for achieving high interfacial tension. •The intermetallic coatings on AZ91 substrate have strong interfacial adhesion.« less

Catalyst Interface Engineering for Improved 2D Film Lift-Off and Transfer

PubMed Central

2016-01-01

The mechanisms by which chemical vapor deposited (CVD) graphene and hexagonal boron nitride (h-BN) films can be released from a growth catalyst, such as widely used copper (Cu) foil, are systematically explored as a basis for an improved lift-off transfer. We show how intercalation processes allow the local Cu oxidation at the interface followed by selective oxide dissolution, which gently releases the 2D material (2DM) film. Interfacial composition change and selective dissolution can thereby be achieved in a single step or split into two individual process steps. We demonstrate that this method is not only highly versatile but also yields graphene and h-BN films of high quality regarding surface contamination, layer coherence, defects, and electronic properties, without requiring additional post-transfer annealing. We highlight how such transfers rely on targeted corrosion at the catalyst interface and discuss this in context of the wider CVD growth and 2DM transfer literature, thereby fostering an improved general understanding of widely used transfer processes, which is essential to numerous other applications. PMID:27934130

Floating growth of large-scale freestanding TiO2 nanorod films at the gas-liquid interface for additive-free Li-ion battery applications.

PubMed

Xia, Hua-Rong; Li, Jia; Peng, Chen; Sun, Wen-Tao; Li, Long-Wei; Peng, Lian-Mao

2014-10-22

The floating growth process of large-scale freestanding TiO2 nanorod films at the gas-liquid interface was investigated. On the basis of the experiments, a self-templated growth scenario was developed to account for the self-assembly process. In the scenario, titanium complexes function not only as the Ti source for the growth of TiO2 but also as a soft template provider for the floating growth. According to the scenario, several new recipes of preparing freestanding TiO2 nanorod films at the gas-liquid interface were developed. The freestanding film was applied to a lithium ion battery as a binder-free and conducting agent-free anode, and good cyclability was obtained. This work may pave a new way to floating and freestanding TiO2 and other semiconductor materials, which has great potential not only in basic science but also in the applications such as materials engineering, Li-ion battery, photocatalyst, dye-sensitized solar cell, and flexible electronics.

A technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates.

PubMed

Fontana, Jake; Spillmann, Christopher; Naciri, Jawad; Ratna, Banahalli R

2014-05-09

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface. The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates. The flow is mediated by a surface tension gradient and creates macroscopic, high-density, monolayer nanoparticle-ligand films. This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

The role of chemical structure on the magnetic and electronic properties of Co{sub 2}FeAl{sub 0.5}Si{sub 0.5}/Si(111) interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuerbanjiang, Balati; Nedelkoski, Zlatko; Ghasemi, Arsham

2016-04-25

We show that Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} film deposited on Si(111) has a single crystal structure and twin related epitaxial relationship with the substrate. Sub-nanometer electron energy loss spectroscopy shows that in a narrow interface region there is a mutual inter-diffusion dominated by Si and Co. Atomic resolution aberration-corrected scanning transmission electron microscopy reveals that the film has B2 ordering. The film lattice structure is unaltered even at the interface due to the substitutional nature of the intermixing. First-principles calculations performed using structural models based on the aberration corrected electron microscopy show that the increased Si incorporation in the filmmore » leads to a gradual decrease of the magnetic moment as well as significant spin-polarization reduction. These effects can have significant detrimental role on the spin injection from the Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} film into the Si substrate, besides the structural integrity of this junction.« less

Effects of Electron Scattering at Metal-Nonmetal Interfaces on Electron-Phonon Equilibration in Gold Films

DTIC Science & Technology

2009-01-26

dielectrics is a major concern in thermal boundary conductance studies . This aspect of energy transfer has been extensively studied and modeled on long...electron-phonon coupling in the particle. There have been only a small number of studies looking at electron-phonon relaxation around interfaces in thin...film systems. These studies avoid complications due to nanopar- ticle geometries i.e., capillary modes on determining the electron-phonon-interfacial

Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

PubMed Central

Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

2015-01-01

Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications. PMID:26250403

Interface-Limited Spherulitic Growth of Hydroxyapatite/Chondroitin Sulfate Composite Enamel-like Films

NASA Astrophysics Data System (ADS)

Ma, Guobin; Xu, Yifei; Wang, Xiyan; Wang, Mu

2012-02-01

Understanding and mimicking the growth of hard tissues such as tooth enamel may lead to innovative approaches toward engineering novel functional materials and providing new therapeutics. Up to now, in vitro growth of enamel-like materials is still a great challenge, and the microscopic formation mechanisms are far from well understood. Here we report synthesis of large-scale hydroxyapatite (HAP) and chondroitin sulfate (ChS) composite films by an efficient solution-air interface growth method. The products have the characteristic hierarchical prism structures of enamel and the mechanical properties comparable to dentin. We demonstrate that the films are assembled by spherulites nucleated at the solution surface. The growth of the spherulites is limited by the interfaces between them as well as between the solution and air, leading to the ordered prism structure. The results are beneficial for a clearer understanding of the fundamentals of tooth enamel formation.

Engineered unique elastic modes at a BaTiO 3/2x1-Ge(001) interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumah, D. P.; Dogan, M.; Ngai, J. H.

Here, the strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO 3 where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO 3. While the complex crystal structure is predicted using first-principles theory, it is further shown that themore » details of the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO 3 induced by the symmetry of forces exerted by the germanium substrate.« less

Engineered Unique Elastic Modes at a BaTiO 3 / ( 2 × 1 ) - Ge ( 001 ) Interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumah, D. P.; Dogan, M.; Ngai, J. H.

The strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO3 where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO3. While the complex crystal structure is predicted using first-principles theory, it is further shown that the details of themore » structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO3 induced by the symmetry of forces exerted by the germanium substrate.« less

Engineered unique elastic modes at a BaTiO 3/2x1-Ge(001) interface

DOE PAGES

Kumah, D. P.; Dogan, M.; Ngai, J. H.; ...

2016-03-07

Here, the strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO 3 where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO 3. While the complex crystal structure is predicted using first-principles theory, it is further shown that themore » details of the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO 3 induced by the symmetry of forces exerted by the germanium substrate.« less

Separation and correlation of structural and magnetic roughness in a Ni thin film by polarized off-specular neutron reflectometry.

PubMed

Singh, Surendra; Basu, Saibal

2009-02-04

Diffuse (off-specular) neutron and x-ray reflectometry has been used extensively for the determination of interface morphology in solids and liquids. For neutrons, a novel possibility is off-specular reflectometry with polarized neutrons to determine the morphology of a magnetic interface. There have been few such attempts due to the lower brilliance of neutron sources, though magnetic interaction of neutrons with atomic magnetic moments is much easier to comprehend and easily tractable theoretically. We have obtained a simple and physically meaningful expression, under the Born approximation, for analyzing polarized diffuse (off-specular) neutron reflectivity (PDNR) data. For the first time PDNR data from a Ni film have been analyzed and separate chemical and magnetic morphologies have been quantified. Also specular polarized neutron reflectivity measurements have been carried out to measure the magnetic moment density profile of the Ni film. The fit to PDNR data results in a longer correlation length for in-plane magnetic roughness than for chemical (structural) roughness. The magnetic interface is smoother than the chemical interface.

Specific Anion Effects on Na+ Adsorption at the Aqueous Solution-Air Interface: MD Simulations, SESSA Calculations, and Photoelectron Spectroscopy Experiments.

PubMed

Olivieri, Giorgia; Parry, Krista M; D'Auria, Raffaella; Tobias, Douglas J; Brown, Matthew A

2018-01-18

Specific ion effects of the large halide anions have been shown to moderate anion adsorption to the air-water interface (AWI), but little quantitative attention has been paid to the behavior of alkali cations. Here we investigate the concentration and local distribution of sodium (Na + ) at the AWI in dilute (<1 M) aqueous solutions of NaCl, NaBr, and NaI using a combination of molecular dynamics (MD) and SESSA simulations, and liquid jet ambient pressure photoelectron spectroscopy measurements. We use SESSA to simulate Na 2p photoelectron intensities on the basis of the atom density profiles obtained from MD simulations, and we compare the simulation results with photoelectron spectroscopy experiments to evaluate the performance of a nonpolarizable force field model versus that of an induced dipole polarizable one. Our results show that the nonpolarizable force model developed by Horinek and co-workers (Chem. Phys. Lett. 2009, 479, 173-183) accurately predicts the local concentration and distribution of Na + near the AWI for all three electrolytes, whereas the polarizable model does not. To our knowledge, this is the first interface-specific spectroscopic validation of a MD force field. The molecular origins of the unique Na + distributions for the three electrolytes are analyzed on the basis of electrostatic arguments, and shown to arise from an indirect anion effect wherein the identity of the anion affects the strength of the attractive Na + -H 2 O electrostatic interaction. Finally, we use the photoelectron spectroscopy results to constrain the range of inelastic mean free paths (IMFPs) for the three electrolyte solutions used in the SESSA simulations that are able to reproduce the experimental intensities. Our results suggest that earlier estimates of IMFPs for aqueous solutions are likely too high.

The dynamics of femtosecond pulsed laser removal of 20 nm Ni films from an interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrider, Keegan J.; Yalisove, Steven M.; Torralva, Ben

2015-09-21

The dynamics of femtosecond laser removal of 20 nm Ni films on glass substrates was studied using time-resolved pump-probe microscopy. 20 nm thin films exhibit removal at two distinct threshold fluences, removal of the top 7 nm of Ni above 0.14 J/cm{sup 2}, and removal of the entire 20 nm film above 0.36 J/cm{sup 2}. Previous work shows the top 7 nm is removed through liquid spallation, after irradiation the Ni melts and rapidly expands leading to tensile stress and cavitation within the Ni film. This work shows that above 0.36 J/cm{sup 2} the 20 nm film is removed in two distinct layers, 7 nm and 13 nm thick. The topmore » 7 nm layer reaches a speed 500% faster than the bottom 13 nm layer at the same absorbed fluence, 500–2000 m/s and 300–700 m/s in the fluence ranges studied. Significantly different velocities for the top 7 nm layer and bottom 13 nm layer indicate removal from an interface occurs by a different physical mechanism. The method of measuring film displacement from the development of Newton's rings was refined so it could be shown that the 13 nm layer separates from the substrate within 70 ps and accelerates to its final velocity within several hundred picoseconds. We propose that removal of the bottom 13 nm is consistent with heterogeneous nucleation and growth of vapor at the Ni-glass interface, but that the rapid separation and acceleration of the 13 nm layer from the Ni-glass interface requires consideration of exotic phases of Ni after excitation.« less

Interface depolarization field as common denominator of fatigue and size effect in Pb(Zr0.54Ti0.46)O3 ferroelectric thin film capacitors

NASA Astrophysics Data System (ADS)

Bouregba, R.; Sama, N.; Soyer, C.; Poullain, G.; Remiens, D.

2010-05-01

Dielectric, hysteresis and fatigue measurements are performed on Pb(Zr0.54Ti0.46)O3 (PZT) thin film capacitors with different thicknesses and different electrode configurations, using platinum and LaNiO3 conducting oxide. The data are compared with those collected in a previous work devoted to study of size effect by R. Bouregba et al., [J. Appl. Phys. 106, 044101 (2009)]. Deterioration of the ferroelectric properties, consecutive to fatigue cycling and thickness downscaling, presents very similar characteristics and allows drawing up a direct correlation between the two phenomena. Namely, interface depolarization field (Edep) resulting from interface chemistry is found to be the common denominator, fatigue phenomena is manifestation of strengthen of Edep in the course of time. Change in dielectric permittivity, in remnant and coercive values as well as in the shape of hysteresis loops are mediated by competition between degradation of dielectric properties of the interfaces and possible accumulation of interface space charge. It is proposed that presence in the band gap of trap energy levels with large time constant due to defects in small nonferroelectric regions at the electrode—PZT film interfaces ultimately governs the aging process. Size effect and aging process may be seen as two facets of the same underlying mechanism, the only difference lies in the observation time of the phenomena.

Transmission electron microscopy characterization of the interfacial structure of a galvanized dual-phase steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aslam, I., E-mail: ia31@msstate.edu

2016-10-15

Site-specific studies were carried out to characterize the interface of a galvanized dual-phase (DP) steel. Focused ion beam (FIB) was used to prepare specimens in the interface region (~ 100 nm thick) between the coating and the substrate. Transmission electron microscopy (TEM), scanning TEM (STEM), and high resolution TEM (HRTEM) were performed to resolve the phases and the structures at the interface between the zinc (Zn) coating and the steel substrate. The STEM and TEM results showed that a continuous manganese oxide (MnO) film with a thickness of ~ 20 nm was present on the surface of the substrate whilemore » no silicon (Si) oxides were resolved. Internal oxide particles were observed as well in the sub-surface region. Despite the presence of the continuous oxide film, a well-developed inhibition layer was observed right on top of the oxide film. The inhibition layer has a thickness of ~ 100 nm. Possible mechanisms for the growth of the inhibition layer were discussed. - Highlights: •Site-specific examinations were performed on the Zn/steel interface. •Continuous external MnO oxides (20 nm) were observed at the interface. •No Si oxides were observed at the interface. •Internal oxide particles were distributed in the subsurface. •A continuous inhibition layer grew on top of the external oxides.« less

Hydrogen evolution using palladium sulfide (PdS) nanocorals as photoanodes in aqueous solution.

PubMed

Barawi, M; Ferrer, I J; Ares, J R; Sánchez, C

2014-11-26

Palladium sulfide (PdS) nanostructures are proposed to be used as photoanodes in photoelectrochemical cells (PECs) for hydrogen evolution due to their adequate transport and optical properties shown in previous works. Here, a complete morphological and electrochemical characterization of PdS films has been performed by different techniques. PdS flatband potential (Vfb=-0.65±0.05 V vs NHE) was determined by electrochemical impedance spectroscopy measurements in aqueous Na2SO3 electrolyte, providing a description of the energy levels scheme at the electrolyte-semiconductor interface. This energy levels scheme confirms PdS as a compound able to photogenerate hydrogen in a PEC. At last, photogenerated hydrogen rates are measured continuously by mass spectrometry as a function of the external bias potential under illumination, reaching values up to 4.4 μmolH2/h at 0.3 V vs Ag/AgCl.

Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

DOE PAGES

Emmez, Emre; Anibal Boscoboinik, J.; Tenney, Samuel; ...

2015-06-30

Bilayer silicate films grown on metal substrates are weakly bound to the metal surfaces, which allows ambient gas molecules to intercalate the oxide/metal interface. In this work, we studied the interaction of oxygen with Ru(0001) supported ultrathin silicate and aluminosilicate films at elevated O 2 pressures (10 -5–10 mbar) and temperatures (450–923 K). The results show that the silicate films stay essentially intact under these conditions, and oxygen in the film does not exchange with oxygen in the ambient. O 2 molecules readily penetrate the film and dissociate on the underlying Ru surface underneath. Also, the silicate layer does howevermore » strongly passivate the Ru surface towards RuO 2(110) oxide formation that readily occurs on bare Ru(0001) under the same conditions. Lastly, the results indicate considerable spatial effects for oxidation reactions on metal surfaces in the confined space at the interface. Moreover, the aluminosilicate films completely suppress the Ru oxidation, providing some rationale for using crystalline aluminosilicates in anti-corrosion coatings.« less

Improved interface growth and enhanced flux pinning in YBCO films deposited on an advanced IBAD-MgO based template

NASA Astrophysics Data System (ADS)

Khan, M. Z.; Zhao, Y.; Wu, X.; Malmivirta, M.; Huhtinen, H.; Paturi, P.

2018-02-01

The growth mechanism is studied from the flux pinning point of view in small-scale YBa2Cu3O6+x (YBCO) thin films deposited on a polycrystalline hastelloy with advanced IBAD-MgO based buffer layer architecture. When compared the situation with YBCO films grown on single crystal substrates, the most critical issues that affect the suitable defect formation and thus the optimal vortex pinning landscape, have been studied as a function of the growth temperature and the film thickness evolution. We can conclude that the best critical current property in a wide applied magnetic field range is observed in films grown at relatively low temperature and having intermediate thickness. These phenomena are linked to the combination of the improved interface growth, to the film thickness related crystalline relaxation and to the formation of linear array of edge dislocations that forms the low-angle grain boundaries through the entire film thickness and thus improve the vortex pinning properties. Hence, the optimized buffer layer structure proved to be particularly suitable for new coated conductor solutions.

Mesoscale simulations of confined Nafion thin films.

PubMed

Vanya, P; Sharman, J; Elliott, J A

2017-12-07

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

Thickness dependent properties of CMR Manganite thin films on lattice mismatched substrates: Distinguishing Strain and Interface Effects

NASA Astrophysics Data System (ADS)

Davidson, Anthony, III; Kolagani, Rajeswari; Bacharova, Ellisaveta; Yong, Grace; Smolyaninova, Vera; Schaefer, David; Mundle, Rajeh

2007-03-01

Epitaxial thin films of CMR manganite materials have been known to show thickness dependent electrical and magnetic properties on lattice mismatched substrates. Below a critical thickness, insulator-metal transition is suppressed. These effects have been largely attributed to the role of bi-axial lattice mismatch strain. Our recent results of epitaxial thin films of La0.67Ca0.33MnO3 (LCMO) on two substrates with varying degrees of compressive lattice mismatch indicate that, in addition to the effect of lattice mismatch strain, the thickness dependence of the properties are influenced by other factors possibly related to the nature of the film substrate interface and defects such as twin boundaries. We have compared the properties of LCMO films on (100) oriented LaAlO3 and (001) oriented NdCaAlO4 both of which induce compressive bi-axial strain. Interestingly, the suppression of the insulator-metal transition is less in films on NCAO which has a larger lattice mismatch. We will present results correlating the electrical and magneto transport properties with the structure and morphology of the films.

Mesoscale simulations of confined Nafion thin films

NASA Astrophysics Data System (ADS)

Vanya, P.; Sharman, J.; Elliott, J. A.

2017-12-01

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow

NASA Astrophysics Data System (ADS)

Tsvelodub, O. Yu; Bocharov, A. A.

2017-09-01

The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. The paper studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. The periodic and soliton steady-state traveling solutions of this equation have been numerically found. The analysis of branching of new families of steady-state traveling solutions has been performed. In particular, it is shown that this model equation has solutions in the form of solitons-humps.

Giant Pockels effect in ZnO-F films deposited on bare glasses

NASA Astrophysics Data System (ADS)

Kityk, I. V.; Ebothe, J.; El Hichou, A.; Addou, M.; Bougrine, A.; Sahraoui, B.

2002-06-01

A giant linear electro-optics (Pockels) effect (up to 17 pm V-1) (for wavelength about 435 nm) in ZnO crystalline films doped with fluorine and deposited on bare glass has been found. For description of the observed phenomenon, a complex approach including self-consistent band structure calculations together with an appropriate molecular dynamics simulation of the interface structure was applied. Experimental ellipsometric and refractive index measurements confirm an efficiency of the mentioned approach for description of the observed interface (between the film and glass) processes. The origin of the observed effect is caused by substantial non-centrosymmetric charge density distribution between the ZnO wurtzite-like crystalline films and the bare glass substrate, as well as by additional charge density polarization caused by fluorine atoms.

A Route Towards Sustainability Through Engineered Polymeric Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeja-Jayan, B; Kovacik, P; Yang, R

2014-05-30

Chemical vapor deposition (CVD) of polymer films represent the marriage of two of the most important technological innovations of the modern age. CVD as a mature technology for growing inorganic thin films is already a workhorse technology of the microfabrication industry and easily scalable from bench to plant. The low cost, mechanical flexibility, and varied functionality offered by polymer thin films make them attractive for both macro and micro scale applications. This review article focuses on two energy and resource efficient CVD polymerization methods, initiated Chemical Vapor Deposition (iCVD) and oxidative Chemical Vapor Deposition (oCVD). These solvent-free, substrate independent techniquesmore » engineer multi-scale, multi-functional and conformal polymer thin film surfaces and interfaces for applications that can address the main sustainability challenges faced by the world today.« less

Model for the Operation of a Monolayer MoS2 Thin-Film Transistor with Charges Trapped near the Channel Interface

NASA Astrophysics Data System (ADS)

Hur, Ji-Hyun; Park, Junghak; Kim, Deok-kee; Jeon, Sanghun

2017-04-01

We propose a model that describes the operation characteristics of a two-dimensional electron gas (2DEG) in a monolayer transition-metal dichalcogenide thin-film transistor (TFT) having trapped charges near the channel interface. We calculate the drift mobility of the carriers scattered by charged defects located in the channel or near the channel interfaces. The calculated drift mobility is a function of the 2DEG areal density of interface traps. Finally, we calculate the model transfer (ID-VG S ) and output (ID-VS D ) characteristics and verify them by comparing with the experimental results performed with monolayer MoS2 TFTs. We find the modeled results to be excellently consistent with the experiments. This proposed model can be utilized for measuring the interface-trapped charge and trap site densities from the measured transfer curves directly, avoiding more complicated and expensive measurement methods.

The stability and half-metallicity of (001) surface and (001) interface based on zinc blende MnAs

NASA Astrophysics Data System (ADS)

Han, Hongpei; Feng, Tuanhui; Zhang, Chunli; Feng, Zhibo; Li, Ming; Yao, K. L.

2018-06-01

Motivated by the growth of MnAs/GaAs thin films in many experimental researches, we investigate the electronic and magnetic properties of bulk, (001) surfaces and (001) interfaces for zinc blende MnAs by means of first-principle calculations. It is confirmed that zinc blende MnAs is a nearly half-metallic ferromagnet with 4.00 μB magnetic moment. The calculated density of states show that the half-metallicity exists in As-terminated (001) surface while it is lost in Mn-terminated (001) surface. For the (001) interfaces of MnAs with semiconductor GaAs, it is found that As-Ga and Mn-As interfaces not only have higher spin polarization but also are more stable among the four considered interfaces. Our results would be helpful to grow stable and high polarized thin films or multilayers for the practical applications of spintronic devices.

Engineering of the chemical reactivity of the Ti/HfO₂ interface for RRAM: experiment and theory.

PubMed

Calka, Pauline; Sowinska, Malgorzata; Bertaud, Thomas; Walczyk, Damian; Dabrowski, Jarek; Zaumseil, Peter; Walczyk, Christian; Gloskovskii, Andrei; Cartoixà, Xavier; Suñé, Jordi; Schroeder, Thomas

2014-04-09

The Ti/HfO2 interface plays a major role for resistance switching performances. However, clear interface engineering strategies to achieve reliable and reproducible switching have been poorly investigated. For this purpose, we present a comprehensive study of the Ti/HfO2 interface by a combined experimental-theoretical approach. Based on the use of oxygen-isotope marked Hf*O2, the oxygen scavenging capability of the Ti layer is clearly proven. More importantly, in line with ab initio theory, the combined HAXPES-Tof-SIMS study of the thin films deposited by MBE clearly establishes a strong impact of the HfO2 thin film morphology on the Ti/HfO2 interface reactivity. Low-temperature deposition is thus seen as a RRAM processing compatible way to establish the critical amount of oxygen vacancies to achieve reproducible and reliable resistance switching performances.

Passively mode-locking induced by gold nanorods in erbium-doped fiber lasers

NASA Astrophysics Data System (ADS)

Kang, Zhe; Xu, Yang; Zhang, Lei; Jia, Zhixu; Liu, Lai; Zhao, Dan; Feng, Yan; Qin, Guanshi; Qin, Weiping

2013-07-01

We demonstrated a passively mode-locked erbium-doped fiber laser by using gold nanorods as a saturable absorber. The gold nanorods (GNRs) were mixed with sodium carboxymethylcellulose (NaCMC) to form GNRs-NaCMC films. By inserting one of the GNRs-NaCMC films into an EDFL cavity pumped by a 980 nm laser diode, stable passively mode-locking was achieved with a threshold pump power of ˜54 mW, and 12 ps pulses at 1561 nm with a repetition rate of 34.7 MHz and a maximum average power of ˜2.05 mW were obtained for a pump power of ˜62 mW.

Molecular dynamics shows that ion pairing and counterion anchoring control the properties of triflate micelles: a comparison with triflate at the air/water interface.

PubMed

Lima, Filipe S; Chaimovich, Hernan; Cuccovia, Iolanda M; Horinek, Dominik

2014-02-11

Micellar properties of dodecyltrimethylammonium triflate (DTA-triflate, DTATf) are very different from those of DTA-bromide (DTAB). DTATf aggregates show high aggregation numbers (Nagg), low degree of counterion dissociation (α), disk-like shape, high packing, ordering, and low hydration. These micellar properties and the low surface tension of NaTf aqueous solutions point to a high affinity of Tf(-) to the micellar and air/water interfaces. Although the micellar properties of DTATf are well defined, the source of the Tf(-) effect upon the DTA aggregates is unclear. Molecular dynamics (MD) simulations of Tf(-) (and Br(-)) at the air/water interface and as counterion of a DTA aggregate were performed to clarify the nature of Tf(-) preferences for these interfaces. The effect of NaTf or NaBr on surface tension calculated from MD simulations agreed with the reported experimental values. From the MD simulations a high affinity of Tf(-) toward the interface, which occurred in a specific orientation, was calculated. The micellar properties calculated from the MD simulations for DTATf and DTAB were consistent with experimental data: in MD simulations, the DTATf aggregate was more ordered, packed, and dehydrated than the DTAB aggregate. The Tf(-)/alkyltrimethylammonium interaction energies, calculated from the MD simulations, suggested ion pair formation at the micellar interface, stabilized by the preferential orientation of the adsorbed Tf(-) at the micellar interface.

Molecular dynamics study of salt-solution interface: solubility and surface charge of salt in water.

PubMed

Kobayashi, Kazuya; Liang, Yunfeng; Sakka, Tetsuo; Matsuoka, Toshifumi

2014-04-14

The NaCl salt-solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt-solution interface system, and calculated the solubility of the salt using the direct method and free energy calculations, which are kinetic and thermodynamic approaches, respectively. The direct method calculation uses a salt-solution combined system. When the system is equilibrated, the concentration in the solution area is the solubility. In the free energy calculation, we separately calculate the chemical potential of NaCl in two systems, the solid and the solution, using thermodynamic integration with MD simulations. When the chemical potential of NaCl in the solution phase is equal to the chemical potential of the solid phase, the concentration of the solution system is the solubility. The advantage of using two different methods is that the computational methods can be mutually verified. We found that a relatively good estimate of the solubility of the system can be obtained through comparison of the two methods. Furthermore, we found using microsecond time-scale MD simulations that the positively charged NaCl surface was induced by a combination of a sodium-rich surface and the orientation of the interfacial water molecules.

Molecular dynamics study of salt–solution interface: Solubility and surface charge of salt in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Kazuya; Liang, Yunfeng, E-mail: y-liang@earth.kumst.kyoto-u.ac.jp, E-mail: matsuoka@earth.kumst.kyoto-u.ac.jp; Matsuoka, Toshifumi, E-mail: y-liang@earth.kumst.kyoto-u.ac.jp, E-mail: matsuoka@earth.kumst.kyoto-u.ac.jp

2014-04-14

The NaCl salt–solution interface often serves as an example of an uncharged surface. However, recent laser-Doppler electrophoresis has shown some evidence that the NaCl crystal is positively charged in its saturated solution. Using molecular dynamics (MD) simulations, we have investigated the NaCl salt–solution interface system, and calculated the solubility of the salt using the direct method and free energy calculations, which are kinetic and thermodynamic approaches, respectively. The direct method calculation uses a salt–solution combined system. When the system is equilibrated, the concentration in the solution area is the solubility. In the free energy calculation, we separately calculate the chemicalmore » potential of NaCl in two systems, the solid and the solution, using thermodynamic integration with MD simulations. When the chemical potential of NaCl in the solution phase is equal to the chemical potential of the solid phase, the concentration of the solution system is the solubility. The advantage of using two different methods is that the computational methods can be mutually verified. We found that a relatively good estimate of the solubility of the system can be obtained through comparison of the two methods. Furthermore, we found using microsecond time-scale MD simulations that the positively charged NaCl surface was induced by a combination of a sodium-rich surface and the orientation of the interfacial water molecules.« less

Diffusion, swelling, cross linkage study and mechanical properties of ZnO doped PVA/NaAlg blend polymer nanocomposite

NASA Astrophysics Data System (ADS)

Guruswamy, B.; Ravindrachary, V.; Shruthi, C.; Hegde, Shreedatta; Sagar, Rohan N.

2018-04-01

ZnO nano particles were synthesized using a chemical precipitation method. Pure and ZnO nano particle doped PVA-NaAlg blend composite films were prepared using solution casing method. Structural information of these composites was studied using FTIR. Diffusion kinetics of these polymer blend composite were studied using Flory-Huggins theory. Using these diffusion studies, cross-linking density and swelling properties of the films were analyzed. Mechanical properties of these composite are also studied.

Defects in paramagnetic Co-doped ZnO films studied by transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kovacs, Andras; Ney, A.; Duchamp, Martial

2013-12-23

We have studied planar defects in epitaxial Co:ZnO dilute magnetic semiconductor thin films deposited on c-plane sapphire (Al2O3) and the Co:ZnO/Al2O3 interface structure at atomic resolution using aberration-corrected transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). Comparing Co:ZnO samples deposited by pulsed laser deposition and reactive magnetron sputtering, both exhibit extrinsic stacking faults, incoherent interface structures, and compositional variations within the first 3-4 Co:ZnO layers at the interface.. In addition, we have measured the local strain which reveals the lattice distortion around the stacking faults.

Sharp chemical interface in epitaxial Fe{sub 3}O{sub 4} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gálvez, S.; Rubio-Zuazo, J., E-mail: rubio@esrf.fr; Salas-Colera, E.

Chemically sharp interface was obtained on single phase single oriented Fe{sub 3}O{sub 4} (001) thin film (7 nm) grown on NiO (001) substrate using oxygen assisted molecular beam epitaxy. Refinement of the atomic structure, stoichiometry, and oxygen vacancies were determined by soft and hard x-ray photoelectron spectroscopy, low energy electron diffraction and synchrotron based X-ray reflectivity, and X-ray diffraction. Our results demonstrate an epitaxial growth of the magnetite layer, perfect iron stoichiometry, absence of oxygen vacancies, and the existence of an intermixing free interface. Consistent magnetic and electrical characterizations are also shown.

Probing surface states in PbS nanocrystal films using pentacene field effect transistors: controlling carrier concentration and charge transport in pentacene.

PubMed

Park, Byoungnam; Whitham, Kevin; Bian, Kaifu; Lim, Yee-Fun; Hanrath, Tobias

2014-12-21

We used a bilayer field effect transistor (FET) consisting of a thin PbS nanocrystals (NCs) film interfaced with vacuum-deposited pentacene to probe trap states in NCs. We interpret the observed threshold voltage shift in context of charge carrier trapping by PbS NCs and relate the magnitude of the threshold voltage shift to the number of trapped carriers. We explored a series of NC surface ligands to modify the interface between PbS NCs and pentacene and demonstrate the impact of interface chemistry on charge carrier density and the FET mobility in a pentacene FET.

Nanoscaled Na3PS4 Solid Electrolyte for All-Solid-State FeS2/Na Batteries with Ultrahigh Initial Coulombic Efficiency of 95% and Excellent Cyclic Performances.

PubMed

Wan, Hongli; Mwizerwa, Jean Pierre; Qi, Xingguo; Xu, Xiaoxiong; Li, Hong; Zhang, Qiang; Cai, Liangting; Hu, Yong-Sheng; Yao, Xiayin

2018-04-18

Nanosized Na 3 PS 4 solid electrolyte with an ionic conductivity of 8.44 × 10 -5 S cm -1 at room temperature is synthesized by a liquid-phase reaction. The resultant all-solid-state FeS 2 /Na 3 PS 4 /Na batteries show an extraordinary high initial Coulombic efficiency of 95% and demonstrate high energy density of 611 Wh kg -1 at current density of 20 mA g -1 at room temperature. The outstanding performances of the battery can be ascribed to good interface compatibility and intimate solid-solid contact at FeS 2 electrode/nanosized Na 3 PS 4 solid electrolytes interface. Meanwhile, excellent cycling stability is achieved for the battery after cycling at 60 mA g -1 for 100 cycles, showing a high capacity of 287 mAh g -1 with the capacity retention of 80%.

Film bonded fuel cell interface configuration

DOEpatents

Kaufman, Arthur; Terry, Peter L.

1989-01-01

The present invention relates to improved elements for use in fuel cell stacks, and more particularly, to a stack having a corrosion-resistant, electrally conductive, fluid-impervious interface member therein.

Electron-stimulated reactions in nanoscale water films adsorbed on (alpha)-Al2O3(0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrik, Nikolay G.; Kimmel, Gregory A.

2018-05-11

The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D2O) films adsorbed on -Al2O3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products ( D2, O2 and D¬2O) and the total sputtering yield increased with increasing D2O coverage up to ~15 water monolayers (i.e. ~15 1015 cm-2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D2O and H2O) demonstrated that the highest water decomposition yields occurred at the interfaces of the nanoscalemore » water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO2(110) interfaces. We propose that the relatively low activity of Al2O3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the molecular hydrogen.« less

Creation and Ordering of Oxygen Vacancies at WO 3-δ and Perovskite Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kelvin H. L.; Li, Guoqiang; Spurgeon, Steven R.

Changes in structure and composition resulting from oxygen deficiency can strongly impact the physical and chemical properties of transition metal oxides, which may lead to new functionalities for novel electronic devices. Oxygen vacancies (V o) can be readily formed to accomodate the lattice mismatch during epitixial thin film growth. In this paper, the effects of substrate strain and oxidizing power on the creation and distribution of V o in WO 3-δ thin films are investigated in detail. An 18O 2 isotope labeled time-of-flight secondary ion mass spectrometry study reveals that WO 3-δ films grown on SrTiO 3 substrates display amore » significantly larger oxygen vacancy gradient along the growth direction compared to those grown on LaAlO 3 substrates. This result is corroborated by scanning transmission electron microscopy imaging which reveals a large number of defects close to the interface to accommodate interfacial tensile strain, leading to the ordering of V o and the formation of semi-aligned Magnéli phases. The strain is gradually released and tetragonal phase with much better crystallinity is observed at the film/vacuum interface. The changes in structure resulting from oxygen defect creation are shown to have a direct impact on the electronic and optical properties of the films.« less

Electron-stimulated reactions in nanoscale water films adsorbed on α-Al 2 O 3 (0001)

DOE PAGES

Petrik, Nikolay G.; Kimmel, Greg A.

2018-04-11

The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D 2O) films adsorbed on an α-Al 2O 3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products (D 2, O 2 and D 2O) and the total sputtering yield increased with increasing D 2O coverage up to ~15 water monolayers (i.e. ~15 x 10 15 cm -2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D 2O and H 2O) demonstrated thatmore » the highest water decomposition yields occurred at the interfaces of the nanoscale water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO 2(110) interfaces. Here, we propose that the relatively low activity of Al 2O 3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the formation of molecular hydrogen.« less

Electron-stimulated reactions in nanoscale water films adsorbed on α-Al 2 O 3 (0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrik, Nikolay G.; Kimmel, Greg A.

The radiation-induced decomposition and desorption of nanoscale amorphous solid water (D 2O) films adsorbed on an α-Al 2O 3(0001) surface was studied at low temperature in ultrahigh vacuum using temperature programmed desorption (TPD) and electron stimulated desorption (ESD) with a mono-energetic, low energy electron source. ESD yields of molecular products (D 2, O 2 and D 2O) and the total sputtering yield increased with increasing D 2O coverage up to ~15 water monolayers (i.e. ~15 x 10 15 cm -2) to a coverage-independent level for thicker water films. Experiments with isotopically-layered water films (D 2O and H 2O) demonstrated thatmore » the highest water decomposition yields occurred at the interfaces of the nanoscale water films with the alumina substrate and vacuum. However, the increased reactivity of the water/alumina interface is relatively small compared to the enhancements in the non-thermal reactions previously observed at the water/Pt(111) and water/TiO 2(110) interfaces. Here, we propose that the relatively low activity of Al 2O 3(0001) for the radiation-induced production of molecular hydrogen is associated with lower reactivity of this surface with hydrogen atoms, which are likely precursors for the formation of molecular hydrogen.« less

Silicon Cations Intermixed Indium Zinc Oxide Interface for High-Performance Thin-Film Transistors Using a Solution Process.

PubMed

Na, Jae Won; Rim, You Seung; Kim, Hee Jun; Lee, Jin Hyeok; Hong, Seonghwan; Kim, Hyun Jae

2017-09-06

Solution-processed amorphous metal-oxide thin-film transistors (TFTs) utilizing an intermixed interface between a metal-oxide semiconductor and a dielectric layer are proposed. In-depth physical characterizations are carried out to verify the existence of the intermixed interface that is inevitably formed by interdiffusion of cations originated from a thermal process. In particular, when indium zinc oxide (IZO) semiconductor and silicon dioxide (SiO 2 ) dielectric layer are in contact and thermally processed, a Si 4+ intermixed IZO (Si/IZO) interface is created. On the basis of this concept, a high-performance Si/IZO TFT having both a field-effect mobility exceeding 10 cm 2 V -1 s -1 and a on/off current ratio over 10 7 is successfully demonstrated.

A novel X-ray photoelectron spectroscopy study of the Al/SiO2 interface

NASA Technical Reports Server (NTRS)

Hecht, M. H.; Vasquez, R. P.; Grunthaner, F. J.; Zamani, N.; Maserjian, J.

1985-01-01

The nondestructive measurement of the chemical and physical characteristics of the interface between bulk SiO2 and thick aluminum films is reported. Both X-ray phototelectron spectroscopy (XPS) and electrical measurements of unannealed, resistively evaporated Al films on thermal SiO2 indicate an atomically abrupt interface. Post metallization annealing at 450 C induces reduction of the SiO2 by the aluminum, at a rate consistent with the bulk reaction rate. The XPS measurement is performed from the SiO2 side after the removal of the Si substrate with XeF2 gas and thinning of the SiO2 layer with HF:ETOH. This represents a powerful new approach to the study of metal-insulator and related interfaces.

Two-scale homogenization to determine effective parameters of thin metallic-structured films

PubMed Central

Marigo, Jean-Jacques

2016-01-01

We present a homogenization method based on matched asymptotic expansion technique to derive effective transmission conditions of thin structured films. The method leads unambiguously to effective parameters of the interface which define jump conditions or boundary conditions at an equivalent zero thickness interface. The homogenized interface model is presented in the context of electromagnetic waves for metallic inclusions associated with Neumann or Dirichlet boundary conditions for transverse electric or transverse magnetic wave polarization. By comparison with full-wave simulations, the model is shown to be valid for thin interfaces up to thicknesses close to the wavelength. We also compare our effective conditions with the two-sided impedance conditions obtained in transmission line theory and to the so-called generalized sheet transition conditions. PMID:27616916

Investigation of the poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene]/indium tin oxide interface using photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Lägel, B.; Beerbom, M. M.; Doran, B. V.; Lägel, M.; Cascio, A.; Schlaf, R.

2005-07-01

The interface between the luminescent polymer poly [2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and sputter-cleaned indium tin oxide (ITO) was investigated using photoemission spectroscopy in combination with in situ thin film deposition. MEH-PPV was deposited in high vacuum directly from toluene solution on the ITO substrate using a home-built electrospray thin-film deposition system. The deposition was carried out in multiple steps without breaking the vacuum. In between deposition steps the sample was characterized with x-ray and ultraviolet photoemission spectroscopy. The evaluation of the spectra sequence allowed the determination of the orbital lineup (charge injection barriers) at the interface, as well as the MEH-PPV growth mode at the interface.

Determination of selenium at trace levels in geologic materials by energy-dispersive X-ray fluorescence spectrometry

USGS Publications Warehouse

Wahlberg, J.S.

1981-01-01

Low levels of selenium (0.1-500 ppm) in both organic and inorganic geologic materials can be semiquantitatively measured by isolating Se as a thin film for presentation to an energy-dispersive X-ray fluorescence spectrometer. Suitably pulverized samples are first digested by fusing with a mixture of Na2CO3 and Na2O2. The fusion cake is dissolved in distilled water, buffered with NH4Cl, and filtered to remove Si and the R2O3 group. A carrier solution of Na2TeO4, plus solid KI, hydrazine sulfate and Na2SO3, is added to the filtrate. The solution is then vacuum-filtered through a 0.45-??m pore-size filter disc. The filter, with the thin film of precipitate, is supported between two sheets of Mylar?? film for analysis. Good agreement is shown between data reported in this study and literature values reported by epithermal neutron-activation analysis and spectrofluorimetry. The method can be made quantitative by utilizing a secondary precipitation to assure complete recovery of the Se. The X-ray method offers fast turn-around time and a reasonably high production rate. ?? 1981.

Nucleation and growth of apatite on NaOH-treated PEEK, HDPE and UHMWPE for artificial cornea materials.

PubMed

Pino, M; Stingelin, N; Tanner, K E

2008-11-01

The skirt of an artificial cornea must integrate the implant to the host sclera, a major failure of present devices. Thus, it is highly desirable to encourage the metabolic activity of the cornea by using more bioactive, flexible skirt materials. Here we describe attempts to increase the bioactivity of polyether ether ketone (PEEK), high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE) films. The effectiveness of different strength NaOH pre-treatments to initiate apatite deposition on PEEK, HDPE and UHMWPE is investigated. We find that exposure of PEEK, HDPE and UHMWPE films to NaOH solutions induces the formation of potential nuclei for apatite (calcium phosphate), from which the growth of an apatite coating is stimulated when subsequently immersing the polymer films in 1.5 strength Simulated Body Fluid (SBF). As immersion time in SBF increases, further nucleation and growth produces a thicker and more compact apatite coating that can be expected to be highly bioactive. Interestingly, the apatite growth is found to also be dependent on both the concentration of NaOH solution and the structure of the polymer surface.

Adsorption-induced conformational changes of antifreeze glycoproteins at the ice/water interface.

PubMed

Uda, Yukihiro; Zepeda, Salvador; Kaneko, Fumitoshi; Matsuura, Yoshiki; Furukawa, Yoshinori

2007-12-27

The conformation of antifreeze glycoprotein (AFGP) molecules adsorbed at the ice/water interface was studied by attenuated total reflection (ATR)-FTIR spectroscopy. Measurements were carried out for AFGP/D2O solution films formed on the surface of an ATR prism as a function of temperature. Using the FTIR spectrum from the O-D stretching band of D2O molecules, we monitored the supercooled and frozen states of the film and measured the thickness of the quasi-liquid layer (QLL) at the ice/prism interfaces. The AFGP structure was determined for the liquid, supercooled, and frozen states of the solution film using the amide I band spectra. No noticeable differences in conformation were observed in the solution conformation from room temperature down to the 15 K supercooling studied, whereas the alpha-helical content of AFGP suddenly increased when the supercooled solution film froze at -15 degrees C. This change in conformation can increase the overall interaction between the AFGP molecules and ice surface and allow a stronger adsorption. In contrast, the alpha-helical content of AFGP in the frozen film gradually decreased with increasing temperature and finally returned to its solution-state level at the melting point of D2O ice. This gradual decrease in the alpha-helix content directly correlates with the measured increase in QLL thickness. Finally, we conclude that the differences in the alpha-helix signals between the frozen and supercooled states indicate the conformational change of AFGP molecules upon adsorption at the ice/water interface, emphasizing the importance of the structure-function relationship, even for this highly flexible antifreeze.

Attenuated total reflection fourier transform infrared spectroscopy towards disclosing mechanism of bacterial adhesion on thermally stabilized titanium nano-interfaces.

PubMed

Gopal, Judy; Chun, Sechul; Doble, Mukesh

2016-08-01

Titanium is widely used as medical implant material and as condenser material in the nuclear industry where its integrity is questioned due to its susceptibility to bacterial adhesion. A systematic investigation on the influence of thermally (50-800 °C) stabilized titanium (TS-Ti) nano oxide towards bacterial adhesion was carried out. The results showed that below 350 °C significant bacterio-phobicity was observed, while above 500 °C significant affinity towards bacterial cells was recorded. Conventional characterization tools such as HR-TEM and XRD did not provide much insight on the changes occurring on the oxide film with heat treatment, however, attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) of the surface showed significant changes in the spectral pattern as a function of increasing heat treatment. It was observed that elevated OH, N-H and C=O groups and rutile titania on the TS-Ti oxide films led to higher affinity for bacterial adhesion. On the other hand low temperature TS-Ti nanooxide films (<350 °C) showed high C-H groups and decreased OH groups on their surface, which possibly contributed towards their bacterio-phobicity. The TS-Ti nanooxide film grown at 50 °C was observed to be the most efficient anti-bacterial adhesion interface, while the 800 °C interface was the one showing highest affinity towards bacterial adhesion. This study confirms the successful application of ATR-FTIR technique for nano-oxide film characterization and towards understanding the variations in bacterial interaction of such nano interfaces.

An XPS study on the chemical bond structure at the interface between SiO{sub x}N{sub y} and N doped polyethylene terephthalate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding Wanyu; Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024; Li Li

2013-03-14

The super-thin silicon oxynitride (SiO{sub x}N{sub y}) films were deposited onto the N doped polyethylene terephthalate (PET) surface. Varying the N doping parameters, the different chemical bond structures were obtained at the interface between the SiO{sub x}N{sub y} film and the PET surface. X-ray photoelectron spectra results showed that at the initial stage of SiO{sub x}N{sub y} film growth, the C=N bonds could be broken and C-N-Si crosslink bonds could be formed at the interface of SiO{sub x}N{sub y}/PET, which C=N bonds could be formed onto the PET surface during the N doping process. At these positions, the SiO{sub x}N{submore » y} film could be crosslinked well onto the PET surface. Meanwhile, the doped N could crosslink the [SiO{sub 4}] and [SiN{sub 4}] tetrahedrons, which could easily form the dense layer structure at the initial stage of SiO{sub x}N{sub y} film growth, instead of the ring and/or chain structures of [SiO{sub 4}] tetrahedrons crosslinked by O. Finally, from the point of applying SiO{sub x}N{sub y}/PET complex as the substrate, the present work reveals a simple way to crosslink them, as well as the crosslink model and physicochemical mechanism happened at the interface of complex.« less

Controllable crystal growth and fast reversible crystallization-to-amorphization in Sb2Te-TiO2 films

PubMed Central

Wang, Guoxiang; Li, Chao; Shi, Daotian; Nie, Qiuhua; Wang, Hui; Shen, Xiang; Lu, Yegang

2017-01-01

The structure evolution and crystallization processes of Sb2Te-TiO2 films have been investigated. The Sb2Te-rich nanocrystals, surrounded by TiO2 amorphous phases, are observed in the annealed Sb2Te-TiO2 composite films. The segregated domains exhibit obvious chalcogenide/TiOx interfaces, which elevate crystallization temperature, impede the grain growth and increase crystalline resistance. Compared with that in conventional Ge2Sb2Te5 film, the shorter time for onset crystallization (25 ns) and amorphization (100 ns) has been achieved in as-deposited (Sb2Te)94.7(TiO2)5.3 film under 60 mW laser irradiation. The corresponding recrystallization and re-amorphization can also be realized in the film. From Johnson-Mehl-Avrami (JMA) analysis, it is further found that the one-dimensional grain growth with controlled interface is dominant for the film during the fast phase-change process. Therefore, (Sb2Te)94.7(TiO2)5.3 film with improved crystallization mechanism is promising for high-stable and fast-speed memory applications. PMID:28397858

Controllable crystal growth and fast reversible crystallization-to-amorphization in Sb2Te-TiO2 films.

PubMed

Wang, Guoxiang; Li, Chao; Shi, Daotian; Nie, Qiuhua; Wang, Hui; Shen, Xiang; Lu, Yegang

2017-04-11

The structure evolution and crystallization processes of Sb 2 Te-TiO 2 films have been investigated. The Sb 2 Te-rich nanocrystals, surrounded by TiO 2 amorphous phases, are observed in the annealed Sb 2 Te-TiO 2 composite films. The segregated domains exhibit obvious chalcogenide/TiO x interfaces, which elevate crystallization temperature, impede the grain growth and increase crystalline resistance. Compared with that in conventional Ge 2 Sb 2 Te 5 film, the shorter time for onset crystallization (25 ns) and amorphization (100 ns) has been achieved in as-deposited (Sb 2 Te) 94.7 (TiO 2 ) 5.3 film under 60 mW laser irradiation. The corresponding recrystallization and re-amorphization can also be realized in the film. From Johnson-Mehl-Avrami (JMA) analysis, it is further found that the one-dimensional grain growth with controlled interface is dominant for the film during the fast phase-change process. Therefore, (Sb 2 Te) 94.7 (TiO 2 ) 5.3 film with improved crystallization mechanism is promising for high-stable and fast-speed memory applications.

Temperature-assisted photochemical construction of CdS-based ordered porous films with photocatalytic activities on solution surfaces.

PubMed

Huang, Zhenxun; Sun, Fengqiang; Zhang, Yu; Gu, Kaiyuan; Zou, Xueqiong; Huang, Yuying; Wu, Qingsong; Zhang, Zihe

2011-04-15

Taking a colloidal monolayer floating on the surface of a precursor solution as template, free-standing CdS/Cd composites and pure CdS (CdS-based) ordered porous films had been prepared by a temperature-assisted photochemical strategy. After irradiation with UV-light and heat treatment, the films formed hemi-spherical pores due to the preferable deposition of CdS and Cd onto the PS spheres during the photochemical and interfacial reactions. When the temperature increased from 15 to 60°C, the air/water interface gradually changed into a vapor/water interface on the surface of the solution, resulting in variations of the final compositions. The optical properties of the films were hence changed. Because of the free-standing characteristic, the ordered porous films were first transferred on surface of polluted solutions as photocatalysts, which was a new mode in application of photocatalysts. The photocatalytic activities of films showed regular variations with the compositions in photodegradation of Rhodamine B. This method provides a simple route for tuning the properties of porous films through control of its composition and a flexible application of films on any surface. Copyright © 2011 Elsevier Inc. All rights reserved.

Investigation of Artificial Forced Cooling in the Bridgman Crystal Growth of Cadmium Zinc Telluride

NASA Astrophysics Data System (ADS)

Liu, Juncheng; Li, Jiao; Zhang, Guodong; Li, Changxing; Lennon, Craig; Sivananthan, Siva

2007-08-01

The effects of artificial forced cooling on the solid liquid interface and on solute segregation were investigated by modeling the vertical Bridgman method for the single-crystal growth of CdZnTe, taking into consideration effects such as increasing the axial outward heat flux from the crucible bottom, the radial outward heat flux from the crucible wall, and the carbon film thickness on the crucible inner wall. Axial artificially forced cooling noticeably increases convection and the temperature gradient in the melt next to the solid liquid interface, and substantially reduces interface concavity at the initial solidification stage. Interface concavity increases a little when the solidification proceeds further, however. Axial artificially forced cooling reduces radial solute segregation of the initial segment of the grown crystal and slightly increases the solute iso-concentration segment. Radial artificially forced cooling enhances melt convection substantially, affects solid liquid interface concavity only slightly, and hardly affects solute segregation in the grown crystal. Doubling the carbon film thickness weakens convection of the melt in front of the interface, substantially increases interface concavity, and hardly affects solute segregation in the grown crystal.

Ferroelectric, piezoelectric, and leakage current properties of (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 thin films grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Wang, D. Y.; Lin, D. M.; Kwok, K. W.; Chan, N. Y.; Dai, J. Y.; Li, S.; Chan, H. L. W.

2011-01-01

Lead-free (K0.48Na0.48Li0.04)(Nb0.775Ta0.225)O3 (KNLNT) thin films were deposited on Pt(111)/Ti/SiO2/Si(001) substrates using pulsed laser deposition. The film exhibited a well-defined ferroelectric hysteresis loop with a remnant polarization 2Pr of 22.6 μC/cm2 and a coercive field Ec of 10.3 kV/mm. The effective piezoelectric coefficient d33,f of the KNLNT thin films was found to be about 49 pm/V by piezoelectric force microscope. The dominant conduction mechanisms of Au/KNLNT/Pt thin film capacitor were determined to be bulk-limited space-charge-limited-current and Poole-Frenkle emission at low and high electric field strengths, respectively, within a measured temperature range of 130-370 K.

Effect of manganese doping on remnant polarization and leakage current in (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 epitaxial thin films on SrTiO3

NASA Astrophysics Data System (ADS)

Abazari, M.; Akdoǧan, E. K.; Safari, A.

2008-05-01

Single phase, epitaxial, ⟨001⟩ oriented, undoped and 1mol% Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10μC /cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1mol% Mn doped films is 13kV/cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50kV/cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors.

Crystallization Mechanism and Charge Carrier Transport in MAPLE-Deposited Conjugated Polymer Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Ban Xuan; Strzalka, Joseph; Jiang, Zhang

Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show thatmore » MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. Furthermore, the evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.« less

Crystallization Mechanism and Charge Carrier Transport in MAPLE-Deposited Conjugated Polymer Thin Films

DOE PAGES

Dong, Ban Xuan; Strzalka, Joseph; Jiang, Zhang; ...

2017-11-23

Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show thatmore » MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. Furthermore, the evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.« less

BONDING ALUMINUM METALS

DOEpatents

Noland, R.A.; Walker, D.E.

1961-06-13

A process is given for bonding aluminum to aluminum. Silicon powder is applied to at least one of the two surfaces of the two elements to be bonded, the two elements are assembled and rubbed against each other at room temperature whereby any oxide film is ruptured by the silicon crystals in the interface; thereafter heat and pressure are applied whereby an aluminum-silicon alloy is formed, squeezed out from the interface together with any oxide film, and the elements are bonded.

Preparation of smooth, flexible and stable silver nanowires- polyurethane composite transparent conductive films by transfer method

NASA Astrophysics Data System (ADS)

Bai, Shengchi; Wang, Haifeng; Yang, Hui; Zhang, He; Guo, Xingzhong

2018-02-01

Silver nanowires (AgNWs)-polyurethane (PU) composite transparent conductive films were fabricated via transfer method using AgNWs conductive inks and polyurethane as starting materials, and the effects of post-treatments including heat treatment, NaCl solution bath and HCl solution bath for AgNWs film on the sheet resistance and transmittance of the composite films were respectively investigated in detail. AgNWs networks are uniformly embedded in the PU layer to improve the adhesion and reduce the surface roughness of AgNWs-PU composite films. Heat treatment can melt and weld the nanowires, and NaCl and HCl solution baths promote the dissolution and re-deposition of silver and the dissolving of the polymer, both which form conduction pathways and improve contact of AgNWs for reducing the sheet resistance. Smooth and flexible AgNWs-PU composite film with a transmittance of 85% and a sheet resistance of 15 Ω · sq‑1 is obtained after treated in 0.5 wt% HCl solution bath for 60 s, and the optoelectronic properties of the resultant composite film can maintain after 1000 cycles of bending and 100 days.

Rough Electrode Creates Excess Capacitance in Thin-Film Capacitors

PubMed Central

2017-01-01

The parallel-plate capacitor equation is widely used in contemporary material research for nanoscale applications and nanoelectronics. To apply this equation, flat and smooth electrodes are assumed for a capacitor. This essential assumption is often violated for thin-film capacitors because the formation of nanoscale roughness at the electrode interface is very probable for thin films grown via common deposition methods. In this work, we experimentally and theoretically show that the electrical capacitance of thin-film capacitors with realistic interface roughness is significantly larger than the value predicted by the parallel-plate capacitor equation. The degree of the deviation depends on the strength of the roughness, which is described by three roughness parameters for a self-affine fractal surface. By applying an extended parallel-plate capacitor equation that includes the roughness parameters of the electrode, we are able to calculate the excess capacitance of the electrode with weak roughness. Moreover, we introduce the roughness parameter limits for which the simple parallel-plate capacitor equation is sufficiently accurate for capacitors with one rough electrode. Our results imply that the interface roughness beyond the proposed limits cannot be dismissed unless the independence of the capacitance from the interface roughness is experimentally demonstrated. The practical protocols suggested in our work for the reliable use of the parallel-plate capacitor equation can be applied as general guidelines in various fields of interest. PMID:28745040

Rough Electrode Creates Excess Capacitance in Thin-Film Capacitors.

PubMed

Torabi, Solmaz; Cherry, Megan; Duijnstee, Elisabeth A; Le Corre, Vincent M; Qiu, Li; Hummelen, Jan C; Palasantzas, George; Koster, L Jan Anton

2017-08-16

The parallel-plate capacitor equation is widely used in contemporary material research for nanoscale applications and nanoelectronics. To apply this equation, flat and smooth electrodes are assumed for a capacitor. This essential assumption is often violated for thin-film capacitors because the formation of nanoscale roughness at the electrode interface is very probable for thin films grown via common deposition methods. In this work, we experimentally and theoretically show that the electrical capacitance of thin-film capacitors with realistic interface roughness is significantly larger than the value predicted by the parallel-plate capacitor equation. The degree of the deviation depends on the strength of the roughness, which is described by three roughness parameters for a self-affine fractal surface. By applying an extended parallel-plate capacitor equation that includes the roughness parameters of the electrode, we are able to calculate the excess capacitance of the electrode with weak roughness. Moreover, we introduce the roughness parameter limits for which the simple parallel-plate capacitor equation is sufficiently accurate for capacitors with one rough electrode. Our results imply that the interface roughness beyond the proposed limits cannot be dismissed unless the independence of the capacitance from the interface roughness is experimentally demonstrated. The practical protocols suggested in our work for the reliable use of the parallel-plate capacitor equation can be applied as general guidelines in various fields of interest.

Interface-enhanced high-temperature superconductivity in single-unit-cell FeT e1 -xS ex films on SrTi O3

NASA Astrophysics Data System (ADS)

Li, Fangsen; Ding, Hao; Tang, Chenjia; Peng, Junping; Zhang, Qinghua; Zhang, Wenhao; Zhou, Guanyu; Zhang, Ding; Song, Can-Li; He, Ke; Ji, Shuaihua; Chen, Xi; Gu, Lin; Wang, Lili; Ma, Xu-Cun; Xue, Qi-Kun

2015-06-01

Recently discovered high-temperature superconductivity in single-unit-cell (UC) FeSe films on SrTi O3 (STO) substrate has stimulated tremendous research interest, both experimental and theoretical. Whether this scenario could be extended to other superconductors is vital in both identifying the enhanced superconductivity mechanism and further raising the critical transition temperature (Tc). Here we successfully prepared single-UC FeT e1 -xS ex(0.1 ≤x ≤0.6 ) films on STO substrates by molecular beam epitaxy and observed U -shaped superconducting gaps (Δ ) up to ˜16.5 meV , nearly ten times the gap value (Δ ˜1.7 meV ) of the optimally doped bulk FeT e0 .6S e0 .4 single crystal (Tc˜14.5 K ). No superconducting gap has been observed on the second UC and thicker FeT e1 -xS ex films at 5.7 K, indicating the important role of the interface. This interface-enhanced high-temperature superconductivity is further confirmed by ex situ transport measurements, which revealed an onset superconducting transition temperature above 40 K, nearly two times higher than that of the optimally doped bulk FeT e0 .6S e0 .4 single crystal. This work demonstrates that interface engineering is a feasible way to discover alternative superconductors with higher Tc.

Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution.

PubMed

Ishizaki, Takahiro; Masuda, Yoshitake; Sakamoto, Michiru

2011-04-19

The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed. © 2011 American Chemical Society

Characterization of biofilm formation by Salmonella enterica at the air-liquid interface in aquatic environments.

PubMed

Medrano-Félix, José Andrés; Chaidez, Cristóbal; Mena, Kristina D; Soto-Galindo, María Del Socorro; Castro-Del Campo, Nohelia

2018-03-15

Survival of bacterial pathogens in different environments is due, in part, to their ability to form biofilms. Four wild-type Salmonella enterica strains, two Oranienburg and two Saintpaul isolated from river water and animal feces, were tested for biofilm formation at the air-liquid interface under stressful conditions (pH and salinity treatments such as pH 3, NaCl 4.5 w/v; pH 7, NaCl 4.5 w/v; pH 10, NaCl 4.5 w/v; pH 3, Nacl 0.5 w/v; pH 7, NaCl 0.5 w/v; and pH 10, NaCl 0.5 w/v); Salmonella Typhimurium DT104 was used as a control strain. Salmonella Oranienburg and Saintpaul from feces were moderately hydrophobic and motile, while S. Saintpaul from water and the control strain S. Typhimurium showed high hydrophobicity, which helped them form more resistant biofilms than S. Oranienburg. Under stressful conditions, all strains experienced difficulties in forming biofilms. Salmonella Saintpaul and Typhimurium expressed the red dry and rough (RDAR) morphotype and were able to form biofilm at air-liquid interface, contrarily to Oranienburg that showed incomplete rough morphology. This study contributes to the knowledge of biofilm formation as a survival strategy for Salmonella in aquatic environments.

Dynamic delamination of patterned thin films

NASA Astrophysics Data System (ADS)

Kandula, Soma S. V.; Tran, Phuong; Geubelle, Philippe H.; Sottos, Nancy R.

2008-12-01

We investigate laser-induced dynamic delamination of a patterned thin film on a substrate. Controlled delamination results from our insertion of a weak adhesion region beneath the film. The inertial forces acting on the weakly bonded portion of the film lead to stable propagation of a crack along the film/substrate interface. Through a simple energy balance, we extract the critical energy for interfacial failure, a quantity that is difficult and sometimes impossible to characterize by more conventional methods for many thin film/substrate combinations.

Simultaneous Formation of Artificial SEI Film and 3D Host for Stable Metallic Sodium Anodes.

PubMed

Zhang, Di; Li, Bin; Wang, Shuai; Yang, Shubin

2017-11-22

Metallic sodium is a promising anode for sodium-based batteries, owing to its high theoretical capacity (1165 mAh g -1 ) and low potential (-2.714 V vs standard hydrogen electrode). However, the growth of sodium dendrites and the infinite volume change of metallic sodium during sodium striping/plating result in a low Coulombic efficiency and poor cycling stability, generating a safety hazard of sodium-based batteries. Here, an efficient approach was proposed to simultaneously generate an artificial SEI film and 3D host for metallic sodium based on a conversion reaction (CR) between sodium and MoS 2 (4Na + MoS 2 = 2Na 2 S + Mo) at room temperature. In the resultant sodium-MoS 2 hybrid after the conversion reaction (Na-MoS 2 (CR)), the production Na 2 S is homogeneously dispersed on the surface of metallic sodium, which can act as an artificial SEI film, efficiently preventing the growth of sodium dendrites; the residual MoS 2 nanosheets can construct a 3D host to confine metallic sodium, accommodating largely the volume change of sodium. Consequently, the Na-MoS 2 (CR) hybrid exhibits very low overpotential of 25 mV and a very long cycle stability more than 1000 cycles. This novel strategy is promising to promote the development of metal (lithium, sodium, zinc)-based electrodes.

Complex oxide thin films for microelectronics

NASA Astrophysics Data System (ADS)

Suvorova, Natalya

The rapid scaling of the device dimensions, namely in metal oxide semiconductor field effect transistor (MOSFET), is reaching its fundamental limit which includes the increase in allowable leakage current due to direct tunneling with decrease of physical thickness of SiO2 gate dielectric. The significantly higher relative dielectric constant (in the range 9--25) of the gate dielectric beyond the 3.9 value of silicon dioxide will allow increasing the physical thickness. Among the choices for the high dielectric constant (K) materials for future generation MOSFET application, barium strontium titanate (BST) and strontium titanate (STO) possess one of the highest attainable K values making them the promising candidates for alternative gate oxide. However, the gate stack engineering does not imply the simple replacement of the SiO2 with the new dielectric. Several requirements should be met for successful integration of a new material. The major one is a production of high level of interface states (Dit) compared to that of SiO 2 on Si. An insertion of a thin SiO2 layer prior the growth of high-K thin film is a simple solution that helps to limit reaction with Si substrate and attains a high quality interface. However, the combination of two thin films reduces the overall K of the dielectric stack. An optimization of the SiO2 underlayer in order to maintain the interface quality yet minimize the effect on K is the focus of this work. The results from our study are presented with emphasis on the key process parameters that improve the dielectric film stack. For in-situ growth characterization of BST and STO films sputter deposited on thermally oxidized Si substrates spectroscopic ellipsometry in combination with time of flight ion scattering and recoil spectrometry have been employed. Studies of material properties have been complemented with analytical electron microscopy. To evaluate the interface quality the electrical characterization has been employed using capacitance-voltage and conductance-voltage measurements. Special attention was given to the extraction of static dielectric constant of BST and STO from the multiple film stack. The K value was found to be sensitive to the input parameters such as dielectric constant and thickness of interface layers.

Thin Films and Interfaces of AN Organic Semiconductor: Perylenetetracarboxylic Dianhydride

NASA Astrophysics Data System (ADS)

Hirose, Yutaka

Structural and electronic properties of thin films of an archetype organic molecular semiconductor, 3,4,9,10 -perylenetetracarboxylic dianhydride, (PTCDA) and of their interfaces are investigated. The first part of the thesis focuses on the growth of PTCDA thin films on graphite and GaAs. Molecular order in the direction parallel to the substrate is found to depend critically on the substrate surface properties, as revealed by marked differences in the crystallinity of films grown on graphite and Se-passivated GaAs surfaces (long range order), on the c(4 x 4) GaAs surface (medium range order), and on the (2 x 4)-c(2 x 8) GaAs surface (short range order). These results are discussed in terms of interface bonding between molecules and the substrate. The second part deals with the electronic and chemical structure of PTCDA thin films and the band lineup of the PTCDA/GaAs heterojunction investigated by Ultraviolet - and X-ray Photoemission Spectroscopies. A basic understanding of the valence band structure and chemical states is obtained with the help of a semi-empirical molecular orbital calculation. At the PTCDA/GaAs interface, the PTCDA highest occupied molecular orbital is found to be ~0.7 eV below the GaAs valence band maximum. This result is discussed in light of previous electrical measurements. Third, chemistry of metal deposition on PTCDA is investigated by synchrotron radiation photoemission spectroscopy. Al, Ti, In, and Sn are found to be highly reactive against PTCDA, yielding a considerable interfacial layer with a large density of states in the PTCDA gap. Ag and Au are found to be inert against PTCDA, producing abrupt interfaces. These results are found to be directly correlated with the electrical properties. Finally, chemistry of contacts formed by reversing the sequence of deposition, i.e. PTCDA on reactive metals (In, Sn, and Ti) is explored. The interfacial layers are found to be considerably smaller than for metals on PTCDA, in accordance with the reverse order of heats of adsorption of the two materials. The resulting interfaces are more abrupt presumably leading to more rectifying character of the electrical contacts.

Experimental design and analysis of activators regenerated by electron transfer-atom transfer radical polymerization experimental conditions for grafting sodium styrene sulfonate from titanium substrates.

PubMed

Foster, Rami N; Johansson, Patrik K; Tom, Nicole R; Koelsch, Patrick; Castner, David G

2015-09-01

A 2 4 factorial design was used to optimize the activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) grafting of sodium styrene sulfonate (NaSS) films from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate (ester ClSi) functionalized titanium substrates. The process variables explored were: (1) ATRP initiator surface functionalization reaction time; (2) grafting reaction time; (3) CuBr 2 concentration; and (4) reducing agent (vitamin C) concentration. All samples were characterized using x-ray photoelectron spectroscopy (XPS). Two statistical methods were used to analyze the results: (1) analysis of variance with [Formula: see text], using average [Formula: see text] XPS atomic percent as the response; and (2) principal component analysis using a peak list compiled from all the XPS composition results. Through this analysis combined with follow-up studies, the following conclusions are reached: (1) ATRP-initiator surface functionalization reaction times have no discernable effect on NaSS film quality; (2) minimum (≤24 h for this system) grafting reaction times should be used on titanium substrates since NaSS film quality decreased and variability increased with increasing reaction times; (3) minimum (≤0.5 mg cm -2 for this system) CuBr 2 concentrations should be used to graft thicker NaSS films; and (4) no deleterious effects were detected with increasing vitamin C concentration.

Elucidating doping driven microstructure evolution and optical properties of lead sulfide thin films grown from a chemical bath

NASA Astrophysics Data System (ADS)

Mohanty, Bhaskar Chandra; Bector, Keerti; Laha, Ranjit

2018-03-01

Doping driven remarkable microstructural evolution of PbS thin films grown by a single-step chemical bath deposition process at 60 °C is reported. The undoped films were discontinuous with octahedral-shaped crystallites after 30 min of deposition, whereas Cu doping led to a distinctly different surface microstructure characterized by densely packed elongated crystallites. A mechanism, based on the time sequence study of microstructural evolution of the films, and detailed XRD and Raman measurements, has been proposed to explain the contrasting microstructure of the doped films. The incorporation of Cu forms an interface layer, which is devoid of Pb. The excess Cu ions in this interface layer at the initial stages of film growth strongly interact and selectively stabilize the charged {111} faces containing either Pb or S compared to the uncharged {100} faces that contain both Pb and S. This interaction interferes with the natural growth habit resulting in the observed surface features of the doped films. Concurrently, the Cu-doping potentially changed the optical properties of the films: A significant widening of the bandgap from 1.52 eV to 1.74 eV for increase in Cu concentration from 0 to 20% was observed, making it a highly potential absorber layer in thin film solar cells.