Mechanical and physicochemical properties study on gellan gum thin film prepared using film casting method

NASA Astrophysics Data System (ADS)

Ismail, Nur Arifah; Razali, Mohd Hasmizam; Amin, Khairul Anuar Mat

2017-09-01

The GG thin films were prepared by film casting technique using gelzan (GG1) and kelcogel (GG2) respectively. The physical appearances of the thin films were observed and their mechanical and chemical properties were investigated. Chemical characterizations were done by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), UV-Vis Spectroscopy, and Scanning Electron Microscopy (SEM). Based on the ATR-FTIR result, GG1 and GG2 thin films show a broad peak in the range of 3600-3200 cm-1 assigned to -OH functional group. A broad peaks also was observed at 3000-2600 cm-1 and 1800-1600 cm-1 which are belong to -CH and C=O functional group, respectively. The UV-Vis Spectroscopy analysis shows that single absorption peak was observed at 260 nm for both films. For mechanical properties, GG1 thin film has high tensile strength (80±12), but low strain at break (2±1), on the other hand GG2 thin film has low tensile strength (3±0.08) but high strain at break (13±0.58). The Water Vapour Transmission Rates (WVTR) and swelling of GG1 and GG2 thin films were (422±113, 415±26) and (987±113, 902±63), respectively.

Low-temperature growth and electronic structures of ambipolar Yb-doped zinc tin oxide transparent thin films

NASA Astrophysics Data System (ADS)

Oh, Seol Hee; Ferblantier, Gerald; Park, Young Sang; Schmerber, Guy; Dinia, Aziz; Slaoui, Abdelilah; Jo, William

2018-05-01

The compositional dependence of the crystal structure, optical transmittance, and surface electric properties of the zinc tin oxide (Zn-Sn-O, shortened ZTO) thin films were investigated. ZTO thin films with different compositional ratios were fabricated on glass and p-silicon wafers using radio frequency magnetron sputtering. The binding energy of amorphous ZTO thin films was examined by a X-ray photoelectron spectroscopy. The optical transmittance over 70% in the visible region for all the ZTO films was observed. The optical band gap of the ZTO films was changed as a result of the competition between the Burstein-Moss effect and renormalization. An electron concentration in the films and surface work function distribution were measured by a Hall measurement and Kelvin probe force microscopy, respectively. The mobility of the n- and p-type ZTO thin films have more than 130 cm2/V s and 15 cm2/V s, respectively. We finally constructed the band structure which contains band gap, work function, and band edges such as valence band maximum and conduction band minimum of ZTO thin films. The present study results suggest that the ZTO thin film is competitive compared with the indium tin oxide, which is a representative material of the transparent conducting oxides, regarding optoelectronic devices applications.

Quantum-dot size and thin-film dielectric constant: precision measurement and disparity with simple models.

PubMed

Grinolds, Darcy D W; Brown, Patrick R; Harris, Daniel K; Bulovic, Vladimir; Bawendi, Moungi G

2015-01-14

We study the dielectric constant of lead sulfide quantum dot (QD) films as a function of the volume fraction of QDs by varying the QD size and keeping the ligand constant. We create a reliable QD sizing curve using small-angle X-ray scattering (SAXS), thin-film SAXS to extract a pair-distribution function for QD spacing, and a stacked-capacitor geometry to measure the capacitance of the thin film. Our data support a reduced dielectric constant in nanoparticles.

Formation and prevention of fractures in sol-gel-derived thin films.

PubMed

Kappert, Emiel J; Pavlenko, Denys; Malzbender, Jürgen; Nijmeijer, Arian; Benes, Nieck E; Tsai, Peichun Amy

2015-02-07

Sol-gel-derived thin films play an important role as the functional coatings for various applications that require crack-free films to fully function. However, the fast drying process of a standard sol-gel coating often induces mechanical stresses, which may fracture the thin films. An experimental study on the crack formation in sol-gel-derived silica and organosilica ultrathin (submicron) films is presented. The relationships among the crack density, inter-crack spacing, and film thickness were investigated by combining direct micrograph analysis with spectroscopic ellipsometry. It is found that silica thin films are more prone to fracturing than organosilica films and have a critical film thickness of 300 nm, above which the film fractures. In contrast, the organosilica films can be formed without cracks in the experimentally explored regime of film thickness up to at least 1250 nm. These results confirm that ultrathin organosilica coatings are a robust silica substitute for a wide range of applications.

Work function measurements of copper nanoparticle intercalated polyaniline nanocomposite thin films

NASA Astrophysics Data System (ADS)

Patil, U. V.; Ramgir, Niranjan S.; Bhogale, A.; Debnath, A. K.; Muthe, K. P.; Gadkari, S. C.; Kothari, D. C.

2017-05-01

The nature of contact between the electrode and the sensing material plays a crucial role in governing the sensing mechanism. Thin films of polyaniline (PANI) and copper-polyaniline nanocomposite (NC) have been deposited at room temperatures by in-situ oxidative polymerization of aniline in the presence of Cu nanoparticles. For sensing applications a thin film Au (gold) ˜100 nm is deposited and used as a conducting electrode. To understand the nature of contact (i.e., ohmic or Schottky) the work function of the conducting polyaniline and nanocomposite films were measured using Kelvin Probe method. I-V characteristics of PANI and NC films investigated at room temperatures further corroborates and confirms the formation of Ohmic contact as evident from work function measurements.

Thin Cu film resistivity using four probe techniques: Effect of film thickness and geometrical shapes

NASA Astrophysics Data System (ADS)

Choudhary, Sumita; Narula, Rahul; Gangopadhyay, Subhashis

2018-05-01

Precise measurement of electrical sheet resistance and resistivity of metallic thin Cu films may play a significant role in temperature sensing by means of resistivity changes which can further act as a safety measure of various electronic devices during their operation. Four point probes resistivity measurement is a useful approach as it successfully excludes the contact resistance between the probes and film surface of the sample. Although, the resistivity of bulk samples at a particular temperature mostly depends on its materialistic property, however, it may significantly differ in the case of thin films, where the shape and thickness of the sample can significantly influence on it. Depending on the ratio of the film thickness to probe spacing, samples are usually classified in two segments such as (i) thick films or (ii) thin films. Accordingly, the geometric correction factors G can be related to the sample resistivity r, which has been calculated here for thin Cu films of thickness up to few 100 nm. In this study, various rectangular shapes of thin Cu films have been used to determine the shape induced geometric correction factors G. An expressions for G have been obtained as a function of film thickness t versus the probe spacing s. Using these expressions, the correction factors have been plotted separately for each cases as a function of (a) film thickness for fixed linear probe spacing and (b) probe distance from the edge of the film surface for particular thickness. Finally, we compare the experimental results of thin Cu films of various rectangular geometries with the theoretical reported results.

Compositional ratio effect on the surface characteristics of CuZn thin films

NASA Astrophysics Data System (ADS)

Choi, Ahrom; Park, Juyun; Kang, Yujin; Lee, Seokhee; Kang, Yong-Cheol

2018-05-01

CuZn thin films were fabricated by RF co-sputtering method on p-type Si(100) wafer with various RF powers applied on metallic Cu and Zn targets. This paper aimed to determine the morphological, chemical, and electrical properties of the deposited CuZn thin films by utilizing a surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), UV photoelectron spectroscopy (UPS), and a 4-point probe. The thickness of the thin films was fixed at 200 ± 8 nm and the roughness of the thin films containing Cu was smaller than pure Zn thin films. XRD studies confirmed that the preferred phase changed, and this tendency is dependent on the ratio of Cu to Zn. AES spectra indicate that the obtained thin films consisted of Cu and Zn. The high resolution XPS spectra indicate that as the content of Cu increased, the intensities of Zn2+ decreased. The work function of CuZn thin films increased from 4.87 to 5.36 eV. The conductivity of CuZn alloy thin films was higher than pure metallic thin films.

Atomic layer deposition of copper thin film and feasibility of deposition on inner walls of waveguides

NASA Astrophysics Data System (ADS)

Yuqing, XIONG; Hengjiao, GAO; Ni, REN; Zhongwei, LIU

2018-03-01

Copper thin films were deposited by plasma-enhanced atomic layer deposition at low temperature, using copper(I)-N,N‧-di-sec-butylacetamidinate as a precursor and hydrogen as a reductive gas. The influence of temperature, plasma power, mode of plasma, and pulse time, on the deposition rate of copper thin film, the purity of the film and the step coverage were studied. The feasibility of copper film deposition on the inner wall of a carbon fibre reinforced plastic waveguide with high aspect ratio was also studied. The morphology and composition of the thin film were studied by atomic force microscopy and x-ray photoelectron spectroscopy, respectively. The square resistance of the thin film was also tested by a four-probe technique. On the basis of on-line diagnosis, a growth mechanism of copper thin film was put forward, and it was considered that surface functional group played an important role in the process of nucleation and in determining the properties of thin films. A high density of plasma and high free-radical content were helpful for the deposition of copper thin films.

Effects of high temperature and film thicknesses on the texture evolution in Ag thin films

NASA Astrophysics Data System (ADS)

Eshaghi, F.; Zolanvari, A.

2017-04-01

In situ high-temperature X-ray diffraction techniques were used to study the effect of high temperatures (up to 600°C) on the texture evolution in silver thin films. Ag thin films with different thicknesses of 40, 80, 120 and 160nm were sputtered on the Si(100) substrates at room temperature. Then, microstructure of thin films was determined using X-ray diffraction. To investigate the influence of temperature on the texture development in the Ag thin films with different thicknesses, (111), (200) and (220) pole figures were evaluated and orientation distribution functions were calculated. Minimizing the total energy of the system which is affected by competition between surface and elastic strain energy was a key factor in the as-deposited and post annealed thin films. Since sputtering depositions was performed at room temperature and at the same thermodynamic conditions, the competition growth caused the formation of the {122} < uvw \\rangle weak fiber texture in as-deposited Ag thin films. It was significantly observed that the post annealed Ag thin films showed {111} < uvw \\rangle orientations as their preferred orientations, but their preferred fiber texture varied with the thickness of thin films. Increasing thin film thickness from 40nm to 160nm led to decreasing the intensity of the {111} < uvw \\rangle fiber texture.

Investigation of the difficulties associated with the use of lead telluride and other II - IV compounds for thin film thermistors

NASA Technical Reports Server (NTRS)

Mclennan, W. D.

1975-01-01

The fabrication of thermistors was investigated for use as atmospheric temperature sensors in meteorological rocket soundings. The final configuration of the thin film thermistor is shown. The composition and primary functions of the six layers of the sensor are described. A digital controller for thin film deposition control is described which is capable of better than .1 A/sec rate control. The computer program modules for digital control of thin film deposition processing are included.

One-Pot Fabrication of Antireflective/Antibacterial Dual-Function Ag NP-Containing Mesoporous Silica Thin Films.

PubMed

Wang, Kaikai; He, Junhui

2018-04-04

Thin films that integrate antireflective and antibacterial dual functions are not only scientifically interesting but also highly desired in many practical applications. Unfortunately, very few studies have been devoted to the preparation of thin films with both antireflective and antibacterial properties. In this study, mesoporous silica (MSiO 2 ) thin films with uniformly dispersed Ag nanoparticles (Ag NPs) were prepared through a one-pot process, which simultaneously shows high transmittance, excellent antibacterial activity, and mechanical robustness. The optimal thin-film-coated glass substrate demonstrates a maximum transmittance of 98.8% and an average transmittance of 97.1%, respectively, in the spectral range of 400-800 nm. The growth and multiplication of typical bacteria, Escherichia coli ( E. coli), were effectively inhibited on the coated glass. Pencil hardness test, tape adhesion test, and sponge washing test showed favorable mechanical robustness with 5H pencil hardness, 5A grade adhesion, and functional durability of the coating, which promises great potential for applications in various touch screens, windows for hygiene environments, and optical apparatuses for medical uses such as endoscope, and so on.

Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

DOE PAGES

Xiao, Zhigang; Kisslinger, Kim

2015-06-17

Thin films of hafnium dioxide (HfO 2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO 2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO 2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO 2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ringmore » oscillator to test the quality of the HfO 2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO 2 thin film functioned very well as the gate oxide.« less

Growth temperature modulated phase evolution and functional characteristics of high quality Pb1-x Lax (Zr0.9Ti0.1)O3 thin films

NASA Astrophysics Data System (ADS)

Kumar, Anuj; Pawar, Shuvam; Singh, Kirandeep; Kaur, Davinder

2018-05-01

In this study, we have reported the influence of growth temperature on perovskite phase evolution in sputtered deposited high quality Pb1-x Lax (Zr0.9 Ti0.1)O3 (PLZT) thin films on Pt/Ti/SiO2/Si substrate. PLZT thin films were fabricated at substrate temperature ranging from 400 to 700 °C. We have investigated the structural, dielectric, ferroelectric and leakage current characteristics of these thin films. XRD patterns reveal that 600 °C is the optimized temperature to deposit highly (110) oriented perovskite phase PLZT thin film. The further increase in temperature (700 °) causes reappearance of additional peaks corresponding to lead deficient pyrochlore phase. All PLZT thin films show decrease in dielectric constant with frequency. However, PLZT thin film fabricated at 600 °C displays dielectric constant ˜532 at 1 MHz frequency which is relatively higher than other deposited thin films. The P-E loops of these PLZT thin films exhibit strong dependence on deposition temperature. The pure perovskite PZLT thin film shows saturation polarization of ˜51.2µC/cm2 and coercive field (2Ec) ˜67.85 kV/cm. These high quality PLZT thin films finds their applications in non-volatile memory and nano-electro-mechanical systems (NEMS).

Deposition of functional nanoparticle thin films by resonant infrared laser ablation.

NASA Astrophysics Data System (ADS)

Haglund, Richard; Johnson, Stephen; Park, Hee K.; Appavoo, Kannatessen

2008-03-01

We have deposited thin films containing functional nanoparticles, using tunable infrared light from a picosecond free-electron laser (FEL). Thin films of the green light-emitting molecule Alq3 were first deposited by resonant infrared laser ablation at 6.68 μm, targeting the C=C ring mode of the Alq3. TiO2 nanoparticles 50-100 nm diameter were then suspended in a water matrix, frozen, and transferred by resonant infrared laser ablation at 2.94 μm through a shadow mask onto the Alq3 film. Photoluminescence was substantially enhanced in the regions of the film covered by the TiO2 nanoparticles. In a second experiment, gold nanoparticles with diameters in the range of 50-100 nm were suspended in the conducting polymer and anti-static coating material PEDOT:PSS, which was diluted by mixing with N-methyl pyrrolidinone (NMP). The gold nanoparticle concentration was 8-10% by weight. The mixture was frozen and then ablated by tuning the FEL to 3.47 μm, the C-H stretch mode of NMP. Optical spectroscopy of the thin film deposited by resonant infrared laser ablation exhibited the surface-plasmon resonance characteristic of the Au nanoparticles. These experiments illustrate the versatility of matrix-assisted resonant infrared laser ablation as a technique for depositing thin films containing functionalized nanoparticles.

Layer-by-Layer Assembly of a pH-Responsive and Electrochromic Thin Film

ERIC Educational Resources Information Center

Schmidt, Daniel J.; Pridgen, Eric M.; Hammond, Paula T.; Love, J. Christopher

2010-01-01

This article summarizes an experiment on thin-film fabrication with layer-by-layer assembly that is appropriate for undergraduate laboratory courses. The purpose of this experiment is to teach students about self-assembly in the context of thin films and to expose students to the concepts of functional polymeric coatings. Students dip coat…

Optical, wetting and electrical properties of functionalized fulleropyrrolidine thin films

NASA Astrophysics Data System (ADS)

Abdulrazack, Parveen; Venkatesan, Sughanya; Chellasamy, Manoharan; Samuthira, Nagarajan

2017-12-01

Fulleropyrrolidine derivatives acts as an electron acceptor in the fabrication of solar cells and other optoelectronic devices. In this investigation thin film of functionalized fulleropyrrolidines were fabricated and studied their photo-physical properties. Surface morphology of the thin films was investigated through AFM and FE-SEM. The results suggested that large dependence on structure vs molecular packing. The long alkyl chain substituted C60 were assembled in the form of nanorods. C60- C60 intermolecular distance were measured, the films were with good absorption and exhibits n-type semiconducting behavior. The films were having high contact angle and can be effectively used for fabricating semiconducting devices with self- cleaning property.

Phase-field simulations of thickness-dependent domain stability in PbTiO3 thin films

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

Sheng, Guang; Hu, Jia-Mian; Zhang, Jinxian

Phase-field approach is used to predict the thickness effect on the domain stability in ferroelectric thin films. The strain relaxation mechanism and critical thickness for dislocation formation from both Matthews-Blakeslee (MB) and People-Bean (PB) models are employed. Thickness - strain domain stability diagrams are obtained for PbTiO3 thin films under different strain relaxation models. The relative domain fractions as a function of film thickness are also calculated and compared with experiment measurements in PbTiO3 thin films grown on SrTiO3 and KTaO3 substrates.

Templated electrochemical deposition of zirconia thin films on "recordable CDs.".

PubMed

Yu, Hua-Zhong; Rowe, Aaron W; Waugh, Damien M

2002-11-15

In this paper, we describe a practical method of using gold films constructed from recordable compact disks (CD-Rs) as simple, inexpensive, and micropatterned conductive substrates for the fabrication of inorganic material microstructures. Extending from their application for the fabrication of self-assembled monolayers (SAMs) reported recently, bare and SAM-modified CD-R gold substrates have been used for template-directed electrodeposition of zirconia (ZrO2) thin films (i.e., the controlled formation of zirconia thin films on the different areas of the prefabricated, micrometer mountain-valley CD-R gold substrate surfaces). The present results demonstrate that the variation of the functional groups of the selected SAMs combined with electrodynamic control can be very successful to "customize" the formation and microstructure of functional inorganic thin films, which hold promise for modern technological applications.

Surface Modification of Self-Assembled Graphene Oxide for Cell Culture Studies

NASA Astrophysics Data System (ADS)

Swain, John E., III

Thin films show great promise for biological applications, from in situ monitoring to pharmaceutical testing. In this study, a graphene oxide (GO) thin film is prepared with the aim to further functionalize the film for pharmaceutical toxicity screening applications. GO was selected due to its capability to be reduced into an optically transparent and electrically conductive thin film. In addition, GO is derived from carbon, a widely abundant element, in contrast to many other thin films that rely on resource-limited precious metals. Special care was taken to select GO and GO film synthesis methods that minimize the amount of organic-based solvents, maintain reactions at atmospheric pressure and moderate temperatures, and are scalable for manufacturing. Chemical oxidation of graphite flakes was carried out via a modified Hummer's Method with a pre-oxidation step. The resulting GO flakes were self-assembled using commercially available 4-sulfocalix[4]arene. Analytical characterizations (e.g., elemental analysis, XRD, FTIR, Raman, SEM, AFM) were performed to evaluate the success of graphite oxidation and formation of the self-assembled thin film. In order to gain a better understanding of the interactions between GO and sulfocalix (SCX), equilibrium conformations of the SCX molecule and truncated GO were calculated using Spartan'16 Parallels. This study demonstrates that the interaction between the GO and the SCX molecule to create a self-assembled thin film is the result of pi-pi stacking, as hypothesized by Sundramoorthy et al. (2015). The self-assembled GO film was successfully deposited on a polyethylene terephthalate (PET) substrate and functionalized with 3-aminopropyl triethoxysilane (APTES), which renders the film capable of further functionalization with proteins for yielding a three-dimensional cell culture or co-culture platform for different applications.

Fabrication of DC inorganic electroluminescent thin-film devices with novel n-p-n type structure

NASA Astrophysics Data System (ADS)

Ishimura, Takuyoshi; Matsumoto, Hironaga

2014-04-01

Inorganic electroluminescent (iEL) thin films are used in light-emitting devices and are functional under alternating current conditions only. Stable luminescent light has yet to be obtained under direct current conditions. We postulated that thin-film iEL light emission occurs when an injected electron occupies the excited state of a luminescent center and then recombines radiatively. From this perspective, we fabricated a novel stacked n-p-n type thin-film iEL device composed of indium tin oxide (ITO)-ZnO-CuAlO2-ZnS-ZnS:TbF3-Al thin films and obtained stable luminescence using a low-voltage DC power supply. The overall luminescent color of the device depended on only the dopant in the luminescent layer, not the band gap or thin-film material.

Pulsed laser deposition of functionalized Mg-Al layered double hydroxide thin films

NASA Astrophysics Data System (ADS)

Vlad, A.; Birjega, R.; Tirca, I.; Matei, A.; Mardare, C. C.; Hassel, A. W.; Nedelcea, A.; Dinescu, M.; Zavoianu, R.

2018-02-01

In this paper, magnesium-aluminium layered double hydroxide (LDH) has been functionalized with sodium dodecyl sulfate (DS) and deposited as thin film by pulsed laser deposition (PLD). Mg, Al-LDH powders were prepared by co-precipitation and used as reference material. Intercalation of DS as an anionic surfactant into the LDHs host layers has been prepared in two ways: co-precipitation (P) and reconstruction (R). DS intercalation occurred in LDH powder via both preparation methods. The films deposited via PLD, in particular at 532 and 1064 nm, preserve the organic intercalated layered structure of the targets prepared from these powders. The results reveal the ability of proposed deposition technique to produce functional composite organo-modified LDHs thin films.

Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films

PubMed Central

Glynn, Colm; Creedon, Donal; Geaney, Hugh; Armstrong, Eileen; Collins, Timothy; Morris, Michael A.; Dwyer, Colm O’

2015-01-01

Solution processed metal oxide thin films are important for modern optoelectronic devices ranging from thin film transistors to photovoltaics and for functional optical coatings. Solution processed techniques such as dip-coating, allow thin films to be rapidly deposited over a large range of surfaces including curved, flexible or plastic substrates without extensive processing of comparative vapour or physical deposition methods. To increase the effectiveness and versatility of dip-coated thin films, alterations to commonly used precursors can be made that facilitate controlled thin film deposition. The effects of polymer assisted deposition and changes in solvent-alkoxide dilution on the morphology, structure, optoelectronic properties and crystallinity of vanadium pentoxide thin films was studied using a dip-coating method using a substrate withdrawal speed within the fast-rate draining regime. The formation of sub-100 nm thin films could be achieved rapidly from dilute alkoxide based precursor solutions with high optical transmission in the visible, linked to the phase and film structure. The effects of the polymer addition was shown to change the crystallized vanadium pentoxide thin films from a granular surface structure to a polycrystalline structure composed of a high density of smaller in-plane grains, resulting in a uniform surface morphology with lower thickness and roughness. PMID:26123117

Self-Limited Growth in Pentacene Thin Films

PubMed Central

2017-01-01

Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought. PMID:28287698

Self-Limited Growth in Pentacene Thin Films.

PubMed

Pachmajer, Stefan; Jones, Andrew O F; Truger, Magdalena; Röthel, Christian; Salzmann, Ingo; Werzer, Oliver; Resel, Roland

2017-04-05

Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought.

Method of improving field emission characteristics of diamond thin films

DOEpatents

Krauss, A.R.; Gruen, D.M.

1999-05-11

A method of preparing diamond thin films with improved field emission properties is disclosed. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display. 3 figs.

Method of improving field emission characteristics of diamond thin films

DOEpatents

Krauss, Alan R.; Gruen, Dieter M.

1999-01-01

A method of preparing diamond thin films with improved field emission properties. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display.

P-doped strontium titanate grown using two target pulsed laser deposition for thin film solar cells

NASA Astrophysics Data System (ADS)

Man, Hamdi

Thin-film solar cells made of Mg-doped SrTiO3 p-type absorbers are promising candidates for clean energy generation. This material shows p-type conductivity and also demonstrates reasonable absorption of light. In addition, p-type SrTiO3 can be deposited as thin films so that the cost can be lower than the competing methods. In this work, Mg-doped SrTiO3 (STO) thin-films were synthesized and analyzed in order to observe their potential to be employed as the base semiconductor in photovoltaic applications. Mg-doped STO thin-films were grown by using pulsed laser deposition (PLD) using a frequency quadrupled Yttrium Aluminum Garnet (YAG) laser and with a substrate that was heated by back surface absorption of infrared (IR) laser light. The samples were characterized using X-ray photoelectron spectroscopy (XPS) and it was observed that Mg atoms were doped successfully in the stoichiometry. Reflection high energy electron diffraction (RHEED) spectroscopy proved that the thin films were polycrystalline. Kelvin Probe work function measurements indicated that the work function of the films were 4.167 eV after annealing. UV/Vis Reflection spectroscopy showed that Mg-doped STO thin-films do not reflect significantly except in the ultraviolet region of the spectrum where the reflection percentage increased up to 80%. Self-doped STO thin-films, Indium Tin Oxide (ITO) thin films and stainless steel foil (SSF) were studied in order to observe their characteristics before employing them in Mg-doped STO based solar cells. Self-doped STO thin films were grown using PLD and the results showed that they are capable of serving as the n-type semiconductor in solar cell applications with oxygen vacancies in their structure and low reflectivity. Indium Tin Oxide thin-films grown by PLD system showed low 25-50 ?/square sheet resistance and very low reflection features. Finally, commercially available stainless steel foil substrates were excellent substrates for the inexpensive growth of these novel solar cells.

Transferable and flexible thin film devices for engineering applications

NASA Astrophysics Data System (ADS)

Mutyala, Madhu Santosh K.; Zhou, Jingzhou; Li, Xiaochun

2014-05-01

Thin film devices can be of significance for manufacturing, energy conversion systems, solid state electronics, wireless applications, etc. However, these thin film sensors/devices are normally fabricated on rigid silicon substrates, thus neither flexible nor transferrable for engineering applications. This paper reports an innovative approach to transfer polyimide (PI) embedded thin film devices, which were fabricated on glass, to thin metal foils. Thin film thermocouples (TFTCs) were fabricated on a thin PI film, which was spin coated and cured on a glass substrate. Another layer of PI film was then spin coated again on TFTC/PI and cured to obtain the embedded TFTCs. Assisted by oxygen plasma surface coarsening of the PI film on the glass substrate, the PI embedded TFTC was successfully transferred from the glass substrate to a flexible copper foil. To demonstrate the functionality of the flexible embedded thin film sensors, they were transferred to the sonotrode tip of an ultrasonic metal welding machine for in situ process monitoring. The dynamic temperatures near the sonotrode tip were effectively measured under various ultrasonic vibration amplitudes. This technique of transferring polymer embedded electronic devices onto metal foils yield great potentials for numerous engineering applications.

Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control

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

Huang, Jingyu; Xiao, Yihan; Xu, Ting

Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules withmore » a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. Lastly, the present studies opened a viable route to achieve designer functional composite thin films via kinetic control.« less

Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control

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

Huang, Jingyu; Xiao, Yihan; Xu, Ting

Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules withmore » a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. The present studies opened a viable route to achieve designer functional composite thin films via kinetic control.« less

Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control

DOE PAGES

Huang, Jingyu; Xiao, Yihan; Xu, Ting

2017-02-20

Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules withmore » a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. Lastly, the present studies opened a viable route to achieve designer functional composite thin films via kinetic control.« less

The structural and optical properties of Y (Y  =  Al, B, Si and Ti)-doped ZnO nano thin films from the first principles calculations

NASA Astrophysics Data System (ADS)

Zhang, Wenshu; Hu, Huijun; Zhang, Caili; Li, Jianguo; Li, Yuping; Ling, Lixia; Han, Peide

2017-12-01

Based on the density functional theory, the structural stability and optical properties of undoped and Y (Y  =  Al, B, Si and Ti)-doped ZnO nano thin films are investigated. The good stability of the films based on the ZnO (0 0 0 1) can be obtained when the layer is larger than 12. Moreover, the dielectric function, refractive index, absorption, and reflectivity of doped ZnO nano thin films have been analyzed in detail. In the visible light range, the values of ZnO films from 12 to 24 layers are all smaller than those of the bulk. And with the augment of the layers, the values keep increasing. All the results signify that the nano film of 12 layers possesses the lowest reflectivity and weakest absorption. In addition, there is an evident impact of some doped element on the properties of nano films. The absorption and reflectivity of Ti, Si-doped ZnO nano thin films are higher than those of the clean films, while Al, B-doped are lower, especially B-doped. Moreover, the conductivity of the doped structure is better than that of the bulk. Thus, the B-doped ZnO nano thin films could be potential candidate materials of transparent conductive films.

Hot plate annealing at a low temperature of a thin ferroelectric P(VDF-TrFE) film with an improved crystalline structure for sensors and actuators.

PubMed

Mahdi, Rahman Ismael; Gan, W C; Abd Majid, W H

2014-10-14

Ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer 70/30 thin films are prepared by spin coating. The crystalline structure of these films is investigated by varying the annealing temperature from the ferroelectric phase to the paraelectric phase. A hot plate was used to produce a direct and an efficient annealing effect on the thin film. The dielectric, ferroelectric and pyroelectric properties of the P(VDF-TrFE) thin films are measured as a function of different annealing temperatures (80 to 140 °C). It was found that an annealing temperature of 100 °C (slightly above the Curie temperature, Tc) has induced a highly crystalline β phase with a rod-like crystal structure, as examined by X-ray. Such a crystal structure yields a high remanent polarization, Pr = 94 mC/m2, and pyroelectric constant, p = 24 μC/m2K. A higher annealing temperature exhibits an elongated needle-like crystal domain, resulting in a decrease in the crystalline structure and the functional electrical properties. This study revealed that highly crystalline P(VDF-TrFE) thin films could be induced at 100 °C by annealing the thin film with a simple and cheap method.

Control of conduction type in ferromagnetic (Zn,Sn,Mn)As2 thin films by changing Mn content and effect of annealing on thin films with n-type conduction

NASA Astrophysics Data System (ADS)

Minamizawa, Yuto; Kitazawa, Tomohiro; Hidaka, Shiro; Toyota, Hideyuki; Nakamura, Shin-ichi; Uchitomi, Naotaka

2018-04-01

The conduction type in (Zn,Sn,Mn)As2 thin films grown by molecular beam epitaxy (MBE) on InP substrates was found to be controllable from p-type to n-type as a function of Mn content. n-type (Zn,Sn,Mn)As2 thin films were obtained by Mn doping of more than approximately 11 cat.%. It is likely that Mn interstitials (MnI) incorporated by excess Mn doping are located at tetrahedral hollow spaces surrounded by Zn and Sn cation atoms and four As atoms, which are expected to act as donors in (Zn,Sn,Mn)As2, resulting in n-type conduction. The effect of annealing on the structural, electrical and magnetic properties of n-type (Zn,Sn,Mn)As2 thin films was investigated as functions of annealing temperature and time. It was revealed that even if the annealing temperature is considerably higher than the growth temperature of 320 °C, the magnetic properties of the thin films remain stable. This suggests that a MnI complex surrounded by Zn and Sn atoms is thermally stable during high-temperature annealing. The n-type (Zn,Sn,Mn)As2 thin films may be suitable for application as n-type spin-polarized injectors.

Effects of drying temperature on tomato-based thin film as self-powered UV photodetector

NASA Astrophysics Data System (ADS)

Thu, Myo Myo; Mastuda, Atsunori; Cheong, Kuan Yew

2018-07-01

In this work, tomato thin-film is used as an active natural organic layer for UV photodetector. The effects of drying temperature (60-140 °C) on structural, chemical, electrical and UV sensing properties of tomato thin-film have been investigated. The photodetector consists of a glass substrate/tomato thin-film active layer/interdigitated aluminium electrode structure. As the drying temperature increases, surface and density of tomato thin-film is smoother and denser with thinner physical thickness. Chemical functional groups as a function of drying temperature is evaluated and correlated with the electrical property of thin film. A comparison between dark and UV (B and C) illumination with respect to the electrical property has been revealed and the observation has been linked to the active chemical compounds that controlling antioxidant activity in the tomato. By drying the tomato thin-film at 120°C, a self-powered (V = 0 V) photodetector that is able to selectively detecting UV-C can be obtained with external quantum efficiency (η) of 2.53 × 10-7%. While drying it at 140 °C, the detector is better in detecting UV-B when operating at either 5 or -5 V with η of 7.7384 × 10-6% and 8.87 × 10-6%, respectively. The typical response time for raising and falling for all samples are less than 0.3 s.

The Effects of ph on Structural and Optical Characterization of Iron Oxide Thin Films

NASA Astrophysics Data System (ADS)

Tezel, Fatma Meydaneri; Özdemir, Osman; Kariper, I. Afşin

In this study, the iron oxide thin films have been produced by chemical bath deposition (CBD) method as a function of pH onto amorphous glass substrates. The surface images of the films were investigated with scanning electron microscope (SEM). The crystal structures, orientation of crystallization, crystallite sizes, and dislocation density i.e. structural properties of the thin films were analyzed with X-ray diffraction (XRD). The optical band gap (Eg), optical transmission (T%), reflectivity (R%), absorption coefficient (α), refraction index (n), extinction coefficient (k) and dielectric constant (ɛ) of the thin films were investigated depending on pH, deposition time, solution temperature, substrate temperature, thickness of the films by UV-VIS spectrometer.

Fabrication and characterization of lead-free BaTiO3 thin film for storage device applications

NASA Astrophysics Data System (ADS)

Sharma, Hakikat; Negi, N. S.

2018-05-01

The lead-free BaTiO3 (BT) thin film solution has been prepared by sol-gel method. The prepared solution spin coated on Pt/TiO2/SiO2/ Si substrate. The fabricated thin film was analyzed by XRD and Raman spectrometer for structural conformation. Uniformity of thin film was examined by Atomic force microscope (AFM). Thickness of the film was measured by cross sectional FESEM. Activation energies for both positive and negative biasing have been calculated from temperature dependent leakage current density as a function of electric field. For ferroelectric memory devices such as FRAM the hysteresis loop plays important role. Electric filed dependent polarization of BT thin film measured at different switching voltages. With increasing voltage maximum polarization increases.

Characterization of ion-assisted induced absorption in A-Si thin-films used for multivariate optical computing

NASA Astrophysics Data System (ADS)

Nayak, Aditya B.; Price, James M.; Dai, Bin; Perkins, David; Chen, Ding Ding; Jones, Christopher M.

2015-06-01

Multivariate optical computing (MOC), an optical sensing technique for analog calculation, allows direct and robust measurement of chemical and physical properties of complex fluid samples in high-pressure/high-temperature (HP/HT) downhole environments. The core of this MOC technology is the integrated computational element (ICE), an optical element with a wavelength-dependent transmission spectrum designed to allow the detector to respond sensitively and specifically to the analytes of interest. A key differentiator of this technology is it uses all of the information present in the broadband optical spectrum to determine the proportion of the analyte present in a complex fluid mixture. The detection methodology is photometric in nature; therefore, this technology does not require a spectrometer to measure and record a spectrum or a computer to perform calculations on the recorded optical spectrum. The integrated computational element is a thin-film optical element with a specific optical response function designed for each analyte. The optical response function is achieved by fabricating alternating layers of high-index (a-Si) and low-index (SiO2) thin films onto a transparent substrate (BK7 glass) using traditional thin-film manufacturing processes (e.g., ion-assisted e-beam vacuum deposition). A proprietary software and process are used to control the thickness and material properties, including the optical constants of the materials during deposition to achieve the desired optical response function. The ion-assisted deposition is useful for controlling the densification of the film, stoichiometry, and material optical constants as well as to achieve high deposition growth rates and moisture-stable films. However, the ion-source can induce undesirable absorption in the film; and subsequently, modify the optical constants of the material during the ramp-up and stabilization period of the e-gun and ion-source, respectively. This paper characterizes the unwanted absorption in the a-Si thin-film using advanced thin-film metrology methods, including spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The resulting analysis identifies a fundamental mechanism contributing to this absorption and a method for minimizing and accounting for the unwanted absorption in the thin-film such that the exact optical response function can be achieved.

Rapid fabrication of hierarchically structured supramolecular nanocomposite thin films in one minute

DOEpatents

Xu, Ting; Kao, Joseph

2016-11-08

Functional nanocomposites containing nanoparticles of different chemical compositions may exhibit new properties to meet demands for advanced technology. It is imperative to simultaneously achieve hierarchical structural control and to develop rapid, scalable fabrication to minimize degradation of nanoparticle properties and for compatibility with nanomanufacturing. The assembly kinetics of supramolecular nanocomposite in thin films is governed by the energetic cost arising from defects, the chain mobility, and the activation energy for inter-domain diffusion. By optimizing only one parameter, the solvent fraction in the film, the assembly kinetics can be precisely tailored to produce hierarchically structured thin films of supramolecular nanocomposites in approximately one minute. Moreover, the strong wavelength dependent optical anisotropy in the nanocomposite highlights their potential applications for light manipulation and information transmission. The present invention opens a new avenue in designing manufacture-friendly continuous processing for the fabrication of functional nanocomposite thin films.

Characterization of sputter deposited thin film scandate cathodes for miniaturized thermionic converter applications

NASA Astrophysics Data System (ADS)

Zavadil, Kevin R.; Ruffner, Judith H.; King, Donald B.

1999-01-01

We have successfully developed a method for fabricating scandate-based thermionic emitters in thin film form. The primary goal of our effort is to develop thin film emitters that exhibit low work function, high intrinsic electron emissivity, minimum thermal activation properties and that can be readily incorporated into a microgap converter. Our approach has been to incorporate BaSrO into a Sc2O3 matrix using rf sputtering to produce thin films. Diode testing has shown the resulting films to be electron emissive at temperatures as low as 900 K with current densities of 0.1 mA.cm-2 at 1100 K and saturation voltages. We calculate an approximate maximum work function of 1.8 eV and an apparent emission constant (Richardson's constant, A*) of 36 mA.cm-2.K-2. Film compositional and structural analysis shows that a significant surface and subsurface alkaline earth hydroxide phase can form and probably explains the limited utilization and stability of Ba and its surface complexes. The flexibility inherent in sputter deposition suggests alternate strategies for eliminating undesirable phases and optimizing thin film emitter properties.

Exciton-phonon coupling in diindenoperylene thin films

NASA Astrophysics Data System (ADS)

Heinemeyer, U.; Scholz, R.; Gisslén, L.; Alonso, M. I.; Ossó, J. O.; Garriga, M.; Hinderhofer, A.; Kytka, M.; Kowarik, S.; Gerlach, A.; Schreiber, F.

2008-08-01

We investigate exciton-phonon coupling and exciton transfer in diindenoperylene (DIP) thin films on oxidized Si substrates by analyzing the dielectric function determined by variable-angle spectroscopic ellipsometry. Since the molecules in the thin-film phase form crystallites that are randomly oriented azimuthally and highly oriented along the surface normal, DIP films exhibit strongly anisotropic optical properties with uniaxial symmetry. This anisotropy can be determined by multiple sample analysis. The thin-film spectrum is compared with a monomer spectrum in solution, which reveals similar vibronic subbands and a Huang-Rhys parameter of S≈0.87 for an effective internal vibration at ℏωeff=0.17eV . However, employing these parameters the observed dielectric function of the DIP films cannot be described by a pure Frenkel exciton model, and the inclusion of charge-transfer (CT) states becomes mandatory. A model Hamiltonian is parametrized with density-functional theory calculations of single DIP molecules and molecule pairs in the stacking geometry of the thin-film phase, revealing the vibronic coupling constants of DIP in its excited and charged states together with electron and hole transfer integrals along the stack. From a fit of the model calculation to the observed dielectric tensor, we find the lowest CT transition E00CT at 0.26±0.05eV above the neutral molecular excitation energy E00F , which is an important parameter for device applications.

Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films

NASA Astrophysics Data System (ADS)

Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

2014-04-01

In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Evaluation of space environmental effects on metals and optical thin films on EOIM-3

NASA Technical Reports Server (NTRS)

Vaughn, Jason A.; Linton, Roger C.; Finckenor, Miria M.; Kamenetzky, Rachel R.

1995-01-01

Metals and optical thin films exposed to the space environment on the Third Flight of the Evaluation of Oxygen Interactions with Materials (EOIM-3) payload, onboard Space Shuttle mission STS-46 were evaluated. The materials effects described in this paper include the effects of space exposure on various pure metals, optical thin films, and optical thin film metals. The changes induced by exposure to the space environment in the material properties were evaluated using bidirectional reflectance distribution function (BRDF), specular reflectance (250 nm to 2500 nm), ESCA, VUV reflectance (120 nm to 200 nm), ellipsometry, FTIR and optical properties. Using these analysis techniques gold optically thin film metal mirrors with nickel undercoats were observed to darken due to nickel diffusion through the gold to the surface. Also, thin film nickel mirrors formed nickel oxide due to exposure to both the atmosphere and space.

A novel nanometric DNA thin film as a sensor for alpha radiation

PubMed Central

Kulkarni, Atul; Kim, Byeonghoon; Dugasani, Sreekantha Reddy; Joshirao, Pranav; Kim, Jang Ah; Vyas, Chirag; Manchanda, Vijay; Kim, Taesung; Park, Sung Ha

2013-01-01

The unexpected nuclear accidents have provided a challenge for scientists and engineers to develop sensitive detectors, especially for alpha radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require placement in close proximity to the radiation source. Here we report the morphological changes and optical responses of artificially designed DNA thin films in response to exposure to alpha radiation as observed by an atomic force microscope, a Raman and a reflectance spectroscopes. In addition, we discuss the feasibility of a DNA thin film as a radiation sensing material. The effect of alpha radiation exposure on the DNA thin film was evaluated as a function of distance from an 241Am source and exposure time. Significant reflected intensity changes of the exposed DNA thin film suggest that a thin film made of biomolecules can be one of promising candidates for the development of online radiation sensors. PMID:23792924

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.

Magnetic damping phenomena in ferromagnetic thin-films and multilayers

NASA Astrophysics Data System (ADS)

Azzawi, S.; Hindmarch, A. T.; Atkinson, D.

2017-11-01

Damped ferromagnetic precession is an important mechanism underpinning the magnetisation processes in ferromagnetic materials. In thin-film ferromagnets and ferromagnetic/non-magnetic multilayers, the role of precession and damping can be critical for spintronic device functionality and as a consequence there has been significant research activity. This paper presents a review of damping in ferromagnetic thin-films and multilayers and collates the results of many experimental studies to present a coherent synthesis of the field. The terms that are used to define damping are discussed with the aim of providing consistent definitions for damping phenomena. A description of the theoretical basis of damping is presented from early developments to the latest discussions of damping in ferromagnetic thin-films and multilayers. An overview of the time and frequency domain methods used to study precessional magnetisation behaviour and damping in thin-films and multilayers is also presented. Finally, a review of the experimental observations of magnetic damping in ferromagnetic thin-films and multilayers is presented with the most recent explanations. This brings together the results from many studies and includes the effects of ferromagnetic film thickness, the effects of composition on damping in thin-film ferromagnetic alloys, the influence of non-magnetic dopants in ferromagnetic films and the effects of combining thin-film ferromagnets with various non-magnetic layers in multilayered configurations.

Characterization of stable, electroactive protein cage/synthetic polymer multilayer thin films prepared by layer-by-layer assembly

NASA Astrophysics Data System (ADS)

Uto, Koichiro; Yamamoto, Kazuya; Kishimoto, Naoko; Muraoka, Masahiro; Aoyagi, Takao; Yamashita, Ichiro

2013-04-01

We have fabricated electroactive multilayer thin films containing ferritin protein cages. The multilayer thin films were prepared on a solid substrate by the alternate electrostatic adsorption of (apo)ferritin and poly( N-isopropylacrylamide- co-2-carboxyisopropylacrylamide) (NIPAAm- co-CIPAAm) in pH 3.5 acetate buffer solution. The assembly process was monitored using a quartz crystal microbalance. The (apo)ferritin/poly(NIPAAm- co-CIPAAm) multilayer thin films were then cross-linked using a water-soluble carbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. The cross-linked films were stable under a variety of conditions. The surface morphology and thickness of the multilayer thin films were characterized by atomic force microscopy, and the ferritin iron cores were observed by scanning electron microscopy to confirm the assembly mechanism. Cyclic voltammetry measurements showed different electrochemical properties for the cross-linked ferritin and apoferritin multilayer thin films, and the effect of stability of the multilayer film on its electrochemical properties was also examined. Our method for constructing multilayer films containing protein cages is expected to be useful in building more complex functional inorganic nanostructures.

Laser deposition and direct-writing of thermoelectric misfit cobaltite thin films

NASA Astrophysics Data System (ADS)

Chen, Jikun; Palla-Papavlu, Alexandra; Li, Yulong; Chen, Lidong; Shi, Xun; Döbeli, Max; Stender, Dieter; Populoh, Sascha; Xie, Wenjie; Weidenkaff, Anke; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

2014-06-01

A two-step process combining pulsed laser deposition of calcium cobaltite thin films and a subsequent laser induced forward transfer as micro-pixel is demonstrated as a direct writing approach of micro-scale thin film structures for potential applications in thermoelectric micro-devices. To achieve the desired thermo-electric properties of the cobaltite thin film, the laser induced plasma properties have been characterized utilizing plasma mass spectrometry establishing a direct correlation to the corresponding film composition and structure. The introduction of a platinum sacrificial layer when growing the oxide thin film enables a damage-free laser transfer of calcium cobaltite thereby preserving the film composition and crystallinity as well as the shape integrity of the as-transferred pixels. The demonstrated direct writing approach simplifies the fabrication of micro-devices and provides a large degree of flexibility in designing and fabricating fully functional thermoelectric micro-devices.

Thin films of a ferroelectric phenazine/chloranilic acid organic cocrystal

NASA Astrophysics Data System (ADS)

Thompson, Nicholas J.; Jandl, Adam C.; Spalenka, Josef W.; Evans, Paul G.

2011-07-01

Phenazine-chloranilic acid cocrystal thin films can be formed by vacuum evaporation of the component molecules onto cooled substrates. Fluxes of phenazine and chloranilic acid were provided from separate sublimation sources, from which the cocrystalline phase can be formed under a wide range of impingement rates of the component molecules. Substrates consisted of Au or Ni thin films on Si wafers, cooled to 100-140 K during deposition. X-ray diffraction and scanning electron microscopy show that this process yields polycrystalline thin films of the cocrystal with voids between crystalline grains. The relative intensities of X-ray reflections differ from reported intensities of polycrystalline powders, suggesting that the films have an anisotropic distribution of crystallographic orientations. The cocrystalline thin films have an effective dielectric constant of 13 at room temperature, increasing at lower temperatures and exhibiting a broad maximum near 200 K. The means to grow thin films of organic ferroelectric materials will allow the integration of new functionalities into organic electronic device structures, including capacitors and field-effect transistors.

PREFACE: INERA Workshop: Transition Metal Oxide Thin Films-functional Layers in "Smart windows" and Water Splitting Devices. Parallel session of the 18th International School on Condensed Matter Physics

NASA Astrophysics Data System (ADS)

2014-11-01

The Special issue presents the papers for the INERA Workshop entitled "Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices", which was held in Varna, St. Konstantin and Elena, Bulgaria, from the 4th-6th September 2014. The Workshop is organized within the context of the INERA "Research and Innovation Capacity Strengthening of ISSP-BAS in Multifunctional Nanostructures", FP7 Project REGPOT 316309 program, European project of the Institute of Solid State Physics at the Bulgarian Academy of Sciences. There were 42 participants at the workshop, 16 from Sweden, Germany, Romania and Hungary, 11 invited lecturers, and 28 young participants. There were researchers present from prestigious European laboratories which are leaders in the field of transition metal oxide thin film technologies. The event contributed to training young researchers in innovative thin film technologies, as well as thin films characterization techniques. The topics of the Workshop cover the field of technology and investigation of thin oxide films as functional layers in "Smart windows" and "Water splitting" devices. The topics are related to the application of novel technologies for the preparation of transition metal oxide films and the modification of chromogenic properties towards the improvement of electrochromic and termochromic device parameters for possible industrial deployment. The Workshop addressed the following topics: Metal oxide films-functional layers in energy efficient devices; Photocatalysts and chemical sensing; Novel thin film technologies and applications; Methods of thin films characterizations; From the 37 abstracts sent, 21 manuscripts were written and later refereed. We appreciate the comments from all the referees, and we are grateful for their valuable contributions. Guest Editors: Assoc. Prof. Dr.Tatyana Ivanova Prof. DSc Kostadinka Gesheva Prof. DSc Hassan Chamatti Assoc. Prof. Dr. Georgi Popkirov Workshop Organizing Committee Prof.DSc Kostadinka Gesheva, Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences (CL SENES-BAS) - Chairperson Assoc. Prof. Dr Anna Szekeres - Institute of Solid State Physics- BAS Assoc. Prof Dr. Tatyana Ivanova - CL SENES -BAS Assist. Prof. Radostina Kamburova - ISSP-BAS

Photoluminescence in Spray Pyrolysis Deposited β-In2S3 Thin Films

NASA Astrophysics Data System (ADS)

Jayakrishnan, R.

2018-04-01

Spray pyrolysis deposited In2S3 thin films exhibit two prominent photoluminescent emissions. One of the emissions is green in color and centered at around ˜ 540 nm and the other is centered at around ˜ 690 nm and is red in color. The intensity of the green emission decreases when the films are subjected to annealing in air or vacuum. The intensity of red emission increases when films are air annealed and decreases when vacuum annealed. Vacuum annealing leads to an increase in work function whereas air annealing leads to a decrease in work function for this thin film system relative to the as deposited films indicating changes in space charge regions. Surface photovoltage analysis using a Kelvin probe leads to the conclusion that inversion of band bending occurs as a result of annealing. Correlating surface contact potential measurements using a Kelvin probe, x-ray photoelectron spectroscopy and photoluminescence, we conclude that the surface passivation plays a critical role in controlling the photoluminescence from the spray pyrolysis deposited for In2S3 thin films.

Structural and spectroscopic analysis of ex-situ annealed RF sputtered aluminium doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Otieno, Francis; Airo, Mildred; Erasmus, Rudolph M.; Billing, David G.; Quandt, Alexander; Wamwangi, Daniel

2017-08-01

Aluminium doped zinc oxide thin films are prepared by Radio Frequency magnetron sputtering in pure argon atmosphere at 100 W. The structural results reveal good film adhesion on a silicon substrate (001). The thin films were then subjected to heat treatment in a furnace under ambient air. The structural, morphological, and optical properties of the thin films as a function of deposition time and annealing temperatures have been investigated using Grazing incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy, and Scanning Electronic Microscopy. The photoluminescence properties of the annealed films showed significant changes in the optical properties attributed to mid gap defects. Annealing increases the crystallite size and the roughness of the film. The crystallinity of the films also improved as evident from the Raman and XRD studies.

Phase Transitions and Domain Structure in Mixed Tetragonal-Rhombohedral BiFeO3 thin films using Raman Spectroscopy and Nonlinear Optics

NASA Astrophysics Data System (ADS)

Vlahos, E.; Kumar, A.; Denev, S.; Melville, A.; Adamo, C.; Ihlefeld, J. F.; Sheng, G.; Zeches, R. J.; Zhang, J. X.; He, Q.; Yang, C. H.; Erni, R.; Rossell, M. D.; J, A.; Hatt; Chu, Y.-H.; Wang, C. H.; Ederer, C.; Gopalan, V.; Chen, L. Q.; Schlom, D. G.; Spaldin, N. A.; Martin, L. W.; Ramesh, R.; Tenne, Dmitri

2010-03-01

We have shown that biaxially strained BiFeO3 thin films can undergo an isosymmetric phase transition from a rhombohedral-like to a tetragonal-like phase. This talk discusses the evolution of the tetragonal and the mixed phases in BiFeO3/YAlO3 thin films with varying film thickness using optical second harmonic generation (SHG) and Raman spectroscopy. 25nm, 75nm, and 225 nm thick films were studied; thinner films are dominated by the tetragonal phase, whereas thicker films exhibit both tetragonal and rhombohedral phases. The evolution of these phases as function of film thickness and temperature was experimentally determined.

Role of solution structure in self-assembly of conjugated block copolymer thin films

DOE PAGES

Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; ...

2016-10-24

Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)- block-poly(diketopyrrolopyrrole–terthiophene) (P3HT- b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT- b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering.more » In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

A fatigue test method for Pb(Zr,Ti)O3 thin films by using MEMS-based self-sensitive piezoelectric microcantilevers

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Maeda, R.; Itoh, T.

2008-11-01

In the present study, we propose a new method for the fatigue test of lead zirconate titanate (PZT) thin films for MEMS devices by using self-sensitive piezoelectric microcantilevers developed in our previous study. We have deposited PZT thin films on SOI wafers and fabricated the microcantilevers through the MEMS microfabrication process. In the self-sensitive piezoelectric microcantilevers, the PZT thin films are separated in order to act as an actuator and a sensor. The fatigue characteristic of the PZT thin films can be evaluated by measuring the output voltage of the sensor as a function of time. When a sine wave of 20 Vpp and a dc bias of 10 V were applied to the PZT thin films for an actuator, the output voltage of the sensor fell down after 107 fatigue cycles. We have also investigated the influence of amplitude of the actuation sine wave and dc bias on the fatigue of the PZT thin films by using the proposed fatigue test method.

Role of solution structure in self-assembly of conjugated block copolymer thin films

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

Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.

Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)- block-poly(diketopyrrolopyrrole–terthiophene) (P3HT- b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT- b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering.more » In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

Diamond Thin-Film Thermionic Generator

NASA Astrophysics Data System (ADS)

Clewell, J. M.; Ordonez, C. A.; Perez, J. M.

1997-03-01

Since the eighteen-hundreds scientists have sought to develop the highest thermal efficiency in heat engines such as thermionic generators. Modern research in the emerging diamond film industry has indicated the work functions of diamond thin-films can be much less than one electron volt, compelling fresh investigation into their capacity as thermionic generators and inviting new methodology for determining that efficiency. Our objective is to predict the efficiency of a low-work-function, degenerate semiconductor (diamond film) thermionic generator operated as a heat engine between two constant-temperature thermal reservoirs. Our presentation will focus on a theoretical model which predicts the efficiency of the system by employing a Monte Carlo computational technique from which we report results for the thermal efficiency and the thermionic current densities of diamond thin-films.

Scavenging of oxygen from SrTiO3 by metals and its implications for oxide thin film deposition

NASA Astrophysics Data System (ADS)

Posadas, Agham; Kormondy, Kristy; Guo, Wei; Ponath, Patrick; Kremer, Jacqueline; Hadamek, Tobias; Demkov, Alexander

SrTiO3 is a widely used substrate for the growth of other functional oxide thin films. However, SrTiO3 loses oxygen very easily during oxide thin film deposition even under relatively high oxygen pressures. In some cases, there will be an interfacial layer of oxygen-deficient SrTiO3 formed at the interface with the deposited oxide film, depending on the metals present in the film. By depositing a variety of metals layer by layer and measuring the evolution of the core level spectra of both the deposited metal and SrTiO3 using x-ray photoelectron spectroscopy, we show that there are three distinct types of behavior that occur for thin metal films on SrTiO3. We discuss the implications of these types of behavior for the growth of complex oxide thin films on SrTiO3, and which oxide thin films are expected to produce an interfacial oxygen-deficient layer depending on their elemental constituents.

Single crystalline thin films as a novel class of electrocatalysts

DOE PAGES

Snyder, Joshua; Markovic, Nenad; Stamenkovic, Vojislav

2013-01-01

The ubiquitous use of single crystal metal electrodes has garnered invaluable insight into the relationship between surface atomic structure and functional electrochemical properties. But, the sensitivity of their electrochemical response to surface orientation and the amount of precious metal required can limit their use. We present here a generally applicable procedure for producing thin metal films with a large proportion of atomically flat (111) terraces without the use of an epitaxial template. Thermal annealing in a controlled atmosphere induces long-range ordering of magnetron sputtered thin metal films deposited on an amorphous substrate. The ordering transition in these thin metal filmsmore » yields characteristic (111) electrochemical signatures with minimal amount of material and provides an adequate replacement for oriented bulk single crystals. Our procedure can be generalized towards a novel class of practical multimetallic thin film based electrocatalysts with tunable near-surface compositional profile and morphology. Annealing of atomically corrugated sputtered thin film Pt-alloy catalysts yields an atomically smooth structure with highly crystalline, (111)-like ordered and Pt segregated surface that displays superior functional properties, bridging the gap between extended/bulk surfaces and nanoscale systems.« less

Fast IR laser mapping ellipsometry for the study of functional organic thin films.

PubMed

Furchner, Andreas; Sun, Guoguang; Ketelsen, Helge; Rappich, Jörg; Hinrichs, Karsten

2015-03-21

Fast infrared mapping with sub-millimeter lateral resolution as well as time-resolved infrared studies of kinetic processes of functional organic thin films require a new generation of infrared ellipsometers. We present a novel laboratory-based infrared (IR) laser mapping ellipsometer, in which a laser is coupled to a variable-angle rotating analyzer ellipsometer. Compared to conventional Fourier-transform infrared (FT-IR) ellipsometers, the IR laser ellipsometer provides ten- to hundredfold shorter measurement times down to 80 ms per measured spot, as well as about tenfold increased lateral resolution of 120 μm, thus enabling mapping of small sample areas with thin-film sensitivity. The ellipsometer, equipped with a HeNe laser emitting at about 2949 cm(-1), was applied for the optical characterization of inhomogeneous poly(3-hexylthiophene) [P3HT] and poly(N-isopropylacrylamide) [PNIPAAm] organic thin films used for opto-electronics and bioapplications. With the constant development of tunable IR laser sources, laser-based infrared ellipsometry is a promising technique for fast in-depth mapping characterization of thin films and blends.

Optical and structural properties of indium doped bismuth selenide thin films

NASA Astrophysics Data System (ADS)

Pavagadhi, Himanshu; Vyas, S. M.; Patel, Piyush; Patel, Vimal; Patel, Jaydev; Jani, M. P.

2015-08-01

In: Bi2Se3 crystals were grown by Bridgman method at a growth velocity of 0.5cm/h with temperature gradient of 650 C/cm in our laboratory. The thin films of In:Bi2se3 were grown on amorphous substrate (glass) at a room temperature under a pressure of 10-4Pa by thermal evaporation technique. Thin film were deposited at various thicknesses and optical absorption spectrum of such thin films, obtain in wave no. range 300 to 2600 cm-1. The optical energy gap calculated from this data were found to be inverse function of square of thickness, particularly for thickness about 1800 Å or less. This dependence is explained in terms of quantum size effect. For thicker films, the bandgap is found to be independent of film thickness. For the surface stud of the as grown thin film by using AFM, which shows continuous film with some step height and surface roughness found in terms of few nm and particle size varies with respect to thickness.

Polarized optical scattering by inhomogeneities and surface roughness in an anisotropic thin film

DOE PAGES

Germer, Thomas A.; Sharma, Katelynn A.; Brown, Thomas G.; ...

2017-10-18

We extend the theory for scattering by oblique columnar structure thin films to include the induced form birefringence and the propagation of radiation in those films. We generalize the 4 × 4 matrix theory to include arbitrary sources in the layer, which are necessary to determine the Green function for the inhomogeneous wave equation. We further extend first-order vector perturbation theory for scattering by roughness in the smooth surface limit, when the layer is anisotropic. Scattering by an inhomogeneous medium is approximated by a distorted Born approximation, where effective medium theory is used to determine the effective properties of themore » medium and strong fluctuation theory is used to determine the inhomogeneous sources. In this manner, we develop a model for scattering by inhomogeneous films, with anisotropic correlation functions. Here, the results are compared to Mueller matrix bidirectional scattering distribution function measurements for a glancing-angle deposition (GLAD) film. While the results are applied to the GLAD film example, the development of the theory is general enough that it can guide simulations for scattering in other anisotropic thin films.« less

Ferroelectric properties of PbxSr1-xTiO3 and its compositionally graded thin films grown on the highly oriented LaNiO3 buffered Pt /Ti/SiO2/Si substrates

NASA Astrophysics Data System (ADS)

Zhai, Jiwei; Yao, Xi; Xu, Zhengkui; Chen, Haydn

2006-08-01

Thin films of ferroelectric PbxSr1-xTiO3 (PST) with x =0.3-0.7 and graded composition were fabricated on LaNiO3 buffered Pt /Ti/SiO2/Si substrates by a sol-gel deposition method. The thin films crystallized into a single perovskite structure and exhibited highly (100) preferred orientation after postdeposition annealing at 650°C. The grain size of PST thin films systematically decreased with the increase of Sr content. Dielectric and ferroelectric properties were investigated as a function of temperature, frequency, and dc applied field. Pb0.6Sr0.4TiO3 films showed a dominant voltage dependence of dielectric constant with a high tunability in a temperature range of 25-230°C. The compositionally graded PST thin films with x =0.3-0.6 also showed the high tunability. The graded thin films exhibited a diffused phase transition accompanied by a diffused peak in the temperature variations of dielectric constants. This kind of thin films has a potential in a fabrication of a temperature stable tunable device.

Optical spectra obtained from amorphous films of rubrene: Evidence for predominance of twisted isomer

NASA Astrophysics Data System (ADS)

Kytka, M.; Gisslen, L.; Gerlach, A.; Heinemeyer, U.; Kováč, J.; Scholz, R.; Schreiber, F.

2009-06-01

In order to investigate the optical properties of rubrene we study the vibronic progression of the first absorption band (lowest π →π∗ transition). We analyze the dielectric function ɛ2 of rubrene in solution and thin films using the displaced harmonic oscillator model and derive all relevant parameters of the vibronic progression. The findings are supplemented by density functional calculations using B3LYP hybrid functionals. Our theoretical results for the molecule in two different conformations, i.e., with a twisted or planar tetracene backbone, are in very good agreement with the experimental data obtained for rubrene in solution and thin films. Moreover, a simulation based on the monomer spectrum and the calculated transition energies of the two conformations indicates that the thin film spectrum of rubrene is dominated by the twisted isomer.

Optical spectra obtained from amorphous films of rubrene: Evidence for predominance of twisted isomer.

PubMed

Kytka, M; Gisslen, L; Gerlach, A; Heinemeyer, U; Kovác, J; Scholz, R; Schreiber, F

2009-06-07

In order to investigate the optical properties of rubrene we study the vibronic progression of the first absorption band (lowest pi-->pi( *) transition). We analyze the dielectric function epsilon(2) of rubrene in solution and thin films using the displaced harmonic oscillator model and derive all relevant parameters of the vibronic progression. The findings are supplemented by density functional calculations using B3LYP hybrid functionals. Our theoretical results for the molecule in two different conformations, i.e., with a twisted or planar tetracene backbone, are in very good agreement with the experimental data obtained for rubrene in solution and thin films. Moreover, a simulation based on the monomer spectrum and the calculated transition energies of the two conformations indicates that the thin film spectrum of rubrene is dominated by the twisted isomer.

Cytotoxicity Evaluation of Anatase and Rutile TiO₂ Thin Films on CHO-K1 Cells in Vitro.

PubMed

Cervantes, Blanca; López-Huerta, Francisco; Vega, Rosario; Hernández-Torres, Julián; García-González, Leandro; Salceda, Emilio; Herrera-May, Agustín L; Soto, Enrique

2016-07-26

Cytotoxicity of titanium dioxide (TiO₂) thin films on Chinese hamster ovary (CHO-K1) cells was evaluated after 24, 48 and 72 h of culture. The TiO₂ thin films were deposited using direct current magnetron sputtering. These films were post-deposition annealed at different temperatures (300, 500 and 800 °C) toward the anatase to rutile phase transformation. The root-mean-square (RMS) surface roughness of TiO₂ films went from 2.8 to 8.08 nm when the annealing temperature was increased from 300 to 800 °C. Field emission scanning electron microscopy (FESEM) results showed that the TiO₂ films' thickness values fell within the nanometer range (290-310 nm). Based on the results of the tetrazolium dye and trypan blue assays, we found that TiO₂ thin films showed no cytotoxicity after the aforementioned culture times at which cell viability was greater than 98%. Independently of the annealing temperature of the TiO₂ thin films, the number of CHO-K1 cells on the control substrate and on all TiO₂ thin films was greater after 48 or 72 h than it was after 24 h; the highest cell survival rate was observed in TiO₂ films annealed at 800 °C. These results indicate that TiO₂ thin films do not affect mitochondrial function and proliferation of CHO-K1 cells, and back up the use of TiO₂ thin films in biomedical science.

Reflectometric measurement of n-hexane adsorption on ZnO2 nanohybrid film modified by hydrophobic gold nanoparticles

NASA Astrophysics Data System (ADS)

Sebők, Dániel; Csapó, Edit; Ábrahám, Nóra; Dékány, Imre

2015-04-01

Zinc-peroxide/poly(styrenesulfonate) nanohybrid thin films (containing 20 bilayers: [ZnO2/PSS]20, d ∼ 500 nm) were prepared using layer-by-layer (LbL) method. The thin film surface was functionalized by different surface modifying agents (silanes, alkylthiols and hydrophobized nanoparticles). Based on the experimental results of quartz crystal microbalance (QCM) and contact angle measurements (as prequalifications) the octanethiol covered gold nanoparticles (OT-AuNPs) were selected for further vapour adsorption studies. Reflectometric interference spectroscopy (RIfS) was used to measure n-hexane vapour adsorption on the original and modified nanohybrid films in a gas flow platform. The thin film provides only the principle of the measurement (by interference phenomenon), the selectivity and hydrophobicity is controlled and enhanced by surface functionalization (by dispersion interaction between the alkyl chains). The interference pattern shift (Δλ) caused by the increase of the optical thickness of the thin film due to vapour adsorption was investigated. It was found that due to the surface functionalization by hydrophobic nanoparticles the effect of water vapour adsorption decreased significantly, while for n-hexane opposite tendency was observed (the effective refractive index and thus the interference pattern shift increased drastically). The correlation between QCM technique and optical method (RIfS) was specified: linear specific adsorbed amount vs. wavelength shift calibration curves were determined in the pr = 0-0.4 relative vapour pressure range. The thin film is suitable for sensorial application (e.g. volatile organic compound/VOC sensor).

Determination of diffusion coefficients in polypyrrole thin films using a current pulse relaxation method

NASA Technical Reports Server (NTRS)

Penner, Reginald M.; Vandyke, Leon S.; Martin, Charles R.

1987-01-01

The current pulse E sub oc relaxation method and its application to the determination of diffusion coefficients in electrochemically synthesized polypyrrole thin films is described. Diffusion coefficients for such films in Et4NBF4 and MeCN are determined for a series of submicron film thicknesses. Measurement of the double-layer capacitance, C sub dl, and the resistance, R sub u, of polypyrrole thin films as a function of potential obtained with the galvanostatic pulse method is reported. Measurements of the electrolyte concentration in reduced polypyrrole films are also presented to aid in the interpretation of the data.

Preparation of pentacene thin film deposited using organic material auto-feeding system for the fabrication of organic thin film transistor.

PubMed

Kim, Young Baek; Choi, Bum Ho; Lim, Yong Hwan; Yoo, Ha Na; Lee, Jong Ho; Kim, Jin Hyeok

2011-02-01

In this study, pentacene organic thin film was prepared using newly developed organic material auto-feeding system integrated with linear cell and characterized. The newly developed organic material auto-feeding system consists of 4 major parts: reservoir, micro auto-feeder, vaporizer, and linear cell. The deposition of organic thin film could be precisely controlled by adjusting feeding rate, main tube size, position and size of nozzle. 10 nm thick pentacene thin film prepared on glass substrate exhibited high uniformity of 3.46% which is higher than that of conventional evaporation method using point cell. The continuous deposition without replenishment of organic material can be performed over 144 hours with regulated deposition control. The grain size of pentacene film which affect to mobility of OTFT, was controlled as a function of the temperature.

Imprint control of BaTiO 3 thin films via chemically induced surface polarization pinning

DOE PAGES

Lee, Hyungwoo; Kim, Tae Heon; Patzner, Jacob J.; ...

2016-02-22

Surface-adsorbed polar molecules can significantly alter the ferroelectric properties of oxide thin films. Thus, fundamental understanding and controlling the effect of surface adsorbates are crucial for the implementation of ferroelectric thin film devices, such as ferroelectric tunnel junctions. Herein, we report an imprint control of BaTiO 3 (BTO) thin films by chemically induced surface polarization pinning in the top few atomic layers of the water-exposed BTO films. Our studies based on synchrotron X-ray scattering and coherent Bragg rod analysis demonstrate that the chemically induced surface polarization is not switchable but reduces the polarization imprint and improves the bistability of ferroelectricmore » phase in BTO tunnel junctions. Here, we conclude that the chemical treatment of ferroelectric thin films with polar molecules may serve as a simple yet powerful strategy to enhance functional properties of ferroelectric tunnel junctions for their practical applications.« less

Chemical and thermal stability of the characteristics of filtered vacuum arc deposited ZnO, SnO2 and zinc stannate thin films

NASA Astrophysics Data System (ADS)

Çetinörgü, E.; Goldsmith, S.

2007-09-01

ZnO, SnO2 and zinc stannate thin films were deposited on commercial microscope glass and UV fused silica substrates using filtered vacuum arc deposition system. During the deposition, the substrate temperature was at room temperature (RT) or at 400 °C. The film structure and composition were determined using x-ray diffraction and x-ray photoelectron spectroscopy, respectively. The transmission of the films in the VIS was 85% to 90%. The thermal stability of the film electrical resistance was determined in air as a function of the temperature in the range 28 °C (RT) to 200 °C. The resistance of ZnO increased from ~ 5000 to 105 Ω when heated to 200 °C, that of SnO2 films increased from 500 to 3900 Ω, whereas that of zinc stannate thin films increased only from 370 to 470 Ω. During sample cooling to RT, the resistance of ZnO and SnO2 thin films continued to rise considerably; however, the increase in the zinc stannate thin film resistance was significantly lower. After cooling to RT, ZnO and SnO2 thin films became practically insulators, while the resistance of zinc stannate was 680 Ω. The chemical stability of the films was determined by immersing in acidic and basic solutions up to 27 h. The SnO2 thin films were more stable in the HCl solution than the ZnO and the zinc stannate thin films; however, SnO2 and zinc stannate thin films that were immersed in the NaOH solution did not dissolve after 27 h.

New insights into the nanostructure of innovative thin film solar cells gained by positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Eijt, S. W. H.; Shi, W.; Mannheim, A.; Butterling, M.; Schut, H.; Egger, W.; Dickmann, M.; Hugenschmidt, C.; Shakeri, B.; Meulenberg, R. W.; Callewaert, V.; Saniz, R.; Partoens, B.; Barbiellini, B.; Bansil, A.; Melskens, J.; Zeman, M.; Smets, A. H. M.; Kulbak, M.; Hodes, G.; Cahen, D.; Brück, E.

2017-01-01

Recent studies showed that positron annihilation methods can provide key insights into the nanostructure and electronic structure of thin film solar cells. In this study, positron annihilation lifetime spectroscopy (PALS) is applied to investigate CdSe quantum dot (QD) light absorbing layers, providing evidence of positron trapping at the surfaces of the QDs. This enables one to monitor their surface composition and electronic structure. Further, 2D-Angular Correlation of Annihilation Radiation (2D-ACAR) is used to investigate the nanostructure of divacancies in photovoltaic-high-quality a-Si:H films. The collected momentum distributions were converted by Fourier transformation to the direct space representation of the electron-positron autocorrelation function. The evolution of the size of the divacancies as a function of hydrogen dilution during deposition of a-Si:H thin films was examined. Finally, we present a first positron Doppler Broadening of Annihilation Radiation (DBAR) study of the emerging class of highly efficient thin film solar cells based on perovskites.

Chemically derived graphene oxide: towards large-area thin-film electronics and optoelectronics.

PubMed

Eda, Goki; Chhowalla, Manish

2010-06-11

Chemically derived graphene oxide (GO) possesses a unique set of properties arising from oxygen functional groups that are introduced during chemical exfoliation of graphite. Large-area thin-film deposition of GO, enabled by its solubility in a variety of solvents, offers a route towards GO-based thin-film electronics and optoelectronics. The electrical and optical properties of GO are strongly dependent on its chemical and atomic structure and are tunable over a wide range via chemical engineering. In this Review, the fundamental structure and properties of GO-based thin films are discussed in relation to their potential applications in electronics and optoelectronics.

Crystallization, fluoridation and some properties of apatite thin films prepared through rf-sputtering from CaO-P2O5 glasses.

PubMed

Yamashita, K; Matsuda, M; Arashi, T; Umegaki, T

1998-07-01

Using calcium phosphate glass targets with the CaO/P2O5 molar ratios of 1.50-0.50, much lower than the stoichiometric value of 3.3 for hydroxyapatite, thin films of stoichiometric hydroxy-, nonstoichiometric oxyhydroxy- and Ca-deficient oxyhydroxy-apatites were prepared on alumina ceramic substrates by rf-sputtering followed by post-annealing. Based on the present results, a phase diagram for CaO-P2O5 at low temperatures in the ambience of air was depicted for thin films. The ambient H2O vapor had an influence on the phase diagram: Tricalcium phosphate was changed to apatite in the presence of H2O vapor. Dense fluorohydroxyapatite thin films were prepared by fluoridation of those apatite thin films at a low temperature such as 200 degrees C. In the present report, some functional properties of thin films thus prepared were also shown.

Strategies towards controlling strain-induced mesoscopic phase separation in manganite thin films

NASA Astrophysics Data System (ADS)

Habermeier, H.-U.

2008-10-01

Complex oxides represent a class of materials with a plethora of fascinating intrinsic physical functionalities. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by lattice effects opens a scientifically rewarding playground for both fundamental as well as application oriented research. The existence of nanoscale electronic phase separation in correlated complex oxides is one of the areas in this field whose impact on the current understanding of their physics and potential applications is not yet clear. In this paper this issue is treated from the point of view of complex oxide thin film technology. Commenting on aspects of complex oxide thin film growth gives an insight into the complexity of a reliable thin film technology for these materials. Exploring fundamentals of interfacial strain generation and strain accommodation paves the way to intentionally manipulate thin film properties. Furthermore, examples are given for an extrinsic continuous tuning of intrinsic electronic inhomogeneities in perovskite-type complex oxide thin films.

Thin-film preparation by back-surface irradiation pulsed laser deposition using metal powder targets

NASA Astrophysics Data System (ADS)

Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Yamauchi, Makiko; Suda, Yoshiaki

2017-01-01

Several kinds of functional thin films were deposited using a new thin-film preparation method named the back-surface irradiation pulsed laser deposition (BIPLD) method. In this BIPLD method, powder targets were used as the film source placed on a transparent target holder, and then a visible-wavelength pulsed laser was irradiated from the holder side to the substrate. Using this new method, titanium oxide and boron nitride thin films were deposited on the silicon substrate. Surface scanning electron microscopy (SEM) images suggest that all of the thin films were deposited on the substrate with some large droplets irrespective of the kind of target used. The deposition rate of the films prepared by using this method was calculated from film thickness and deposition time to be much lower than that of the films prepared by conventional PLD. X-ray diffraction (XRD) measurement results suggest that rutile and anatase TiO2 crystal peaks were formed for the films prepared using the TiO2 rutile powder target. Crystal peaks of hexagonal boron nitride were observed for the films prepared using the boron nitride powder target. The crystallinity of the prepared films was changed by annealing after deposition.

Growth Mechanism of Cluster-Assembled Surfaces: From Submonolayer to Thin-Film Regime

NASA Astrophysics Data System (ADS)

Borghi, Francesca; Podestà, Alessandro; Piazzoni, Claudio; Milani, Paolo

2018-04-01

Nanostructured films obtained by assembling preformed atomic clusters are of strategic importance for a wide variety of applications. The deposition of clusters produced in the gas phase onto a substrate offers the possibility to control and engineer the structural and functional properties of the cluster-assembled films. To date, the microscopic mechanisms underlying the growth and structuring of cluster-assembled films are poorly understood, and, in particular, the transition from the submonolayer to the thin-film regime is experimentally unexplored. Here we report the systematic characterization by atomic force microscopy of the evolution of the structural properties of cluster-assembled films deposited by supersonic cluster beam deposition. As a paradigm of nanostructured systems, we focus our attention on cluster-assembled zirconia films, investigating the influence of the building block dimensions on the growth mechanisms and roughening of the thin films, following the growth process from the early stages of the submonolayer to the thin-film regime. Our results demonstrate that the growth dynamics in the submonolayer regime determines different morphological properties of the cluster-assembled thin film. The evolution of the roughness with the number of deposited clusters reproduces the growth exponent of the ballistic deposition in the 2 +1 model from the submonolayer to the thin-film regime.

High Tc superconducting IR detectors from Y-Ba-Cu-O thin films

NASA Technical Reports Server (NTRS)

Lindgren, M.; Ahlberg, H.; Danerud, M.; Larsson, A.; Eng, M.

1990-01-01

A thin-film high-Tc superconducting multielement optical detector made of Y-Ba-Cu-O has been designed and evaluated using optical pulses from a diode laser (830 nm) and a Q-switched CO2-laser (10.6 microns). Different thin films have been tested. A laser deposited film showed the strongest response amplitude for short pulses and responded to an ultrafast, 50 ps wide pulse. Comparisons between dR/dT and response as a function of temperature indicated, however, a bolometric response.

Recent progress of obliquely deposited thin films for industrial applications

NASA Astrophysics Data System (ADS)

Suzuki, Motofumi; Itoh, Tadayoshi; Taga, Yasunori

1999-06-01

More than 10 years ago, birefringent films of metal oxides were formed by oblique vapor deposition and investigated with a view of their application to optical retardation plates. The retardation function of the films was explained in terms of the birefringence caused by the characteristic anisotropic nanostructure inside the films. These films are now classified in the genre of the so-called sculptured thin films. However, the birefringent films thus prepared are not yet industrialized even now due to the crucial lack of the durability and the yield of products. In this review paper, we describe the present status of application process of the retardation films to the information systems such as compact disc and digital versatile disc devices with a special emphasis on the uniformity of retardation properties in a large area and the stability of the optical properties of the obliquely deposited thin films. Finally, further challenges for wide application of the obliquely deposited thin films are also discussed.

Effect of dead layer and strain on diffuse phase transition of PLZT relaxor thin films.

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

Tong, S.; Narayanan, M.; Ma, B.

2011-02-01

Bulk relaxor ferroelectrics exhibit excellent permittivity compared to their thin film counterpart, although both show diffuse phase transition (DPT) behavior unlike normal ferroelectrics. To better understand the effect of dead layer and strain on the observed anomaly in the dielectric properties, we have developed relaxor PLZT (lead lanthanum zirconate titanate) thin films with different thicknesses and measured their dielectric properties as a function of temperature and frequency. The effect of dead layer on thin film permittivity has been found to be independent of temperature and frequency, and is governed by the Schottky barrier between the platinum electrode and PLZT. Themore » total strain (thermal and intrinsic) in the film majorly determines the broadening, dielectric peak and temperature shift in the relaxor ferroelectric. The Curie-Weiss type law for relaxors has been further modified to incorporate these two effects to accurately predict the DPT behavior of thin film and bulk relaxor ferroelectrics. The dielectric behavior of thin film is predicted by using the bulk dielectric data from literature in the proposed equation, which agree well with the measured dielectric behavior.« less

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

Laskowski, Lukasz, E-mail: lukasz.laskowski@kik.pcz.pl; Laskowska, Magdalena, E-mail: magdalena.laskowska@onet.pl; Jelonkiewicz, Jerzy, E-mail: jerzy.jelonkiewicz@kik.pcz.pl

The SBA-15 silica thin films containing copper ions anchored inside channels via propyl phosphonate groups are investigated. Such materials were prepared in the form of thin films, with hexagonally arranged pores, laying rectilinear to the substrate surface. However, in the case of our thin films, their free standing form allowed for additional research possibilities, that are not obtainable for typical thin films on a substrate. The structural properties of the samples were investigated by X-ray reflectometry, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The molecular structure was examined by Raman spectroscopy supported by numerical simulations. Magnetic measurements (SQUIDmore » magnetometry and EPR spectroscopy) showed weak antiferromagnetic interactions between active units inside silica channels. Consequently, the pores arrangement was determined and the process of copper ions anchoring by propyl phosphonate groups was verified in unambiguous way. Moreover, the type of interactions between magnetic atoms was determined. - Highlights: • Functionalized free-standing SBA-15 thin films were synthesized for a first time. • Thin films synthesis procedure was described in details. • Structural properties of the films were thoroughly investigated and presented. • Magnetic properties of the novel material was investigated and presented.« less

Atomic moments in Mn 2CoAl thin films analyzed by X-ray magnetic circular dichroism

DOE PAGES

Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; ...

2014-12-05

Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn 2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

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.

Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films.

PubMed

Kim, Seong Keun; Han, Sora; Jeon, Woojin; Yoon, Jung Ho; Han, Jeong Hwan; Lee, Woongkyu; Hwang, Cheol Seong

2012-09-26

Rutile structured Al-doped TiO(2) (ATO) and TiO(2) films were grown on bimetal electrodes (thin Ru/thick TiN, Pt, and Ir) for high-performance capacitors. The work function of the top Ru layer decreased on TiN and increased on Pt and Ir when it was thinner than ~2 nm, suggesting that the lower metal within the electrodes influences the work function of the very thin Ru layer. The use of the lower electrode with a high work function for bottom electrode eventually improves the leakage current properties of the capacitor at a very thin Ru top layer (≤2 nm) because of the increased Schottky barrier height at the interface between the dielectric and the bottom electrode. The thin Ru layer was necessary to achieve the rutile structured ATO and TiO(2) dielectric films.

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.

Multi-functional properties of CaCu3Ti4O12 thin films

NASA Astrophysics Data System (ADS)

Felix, A. A.; Rupp, J. L. M.; Varela, J. A.; Orlandi, M. O.

2012-09-01

In this work, electric transport properties of CaCu3Ti4O12 (CCTO) thin films were investigated for resistive switching, rectifying and gas sensor applications. Single phase CCTO thin films were produced by polymeric precursor method (PPM) on different substrates and their electrical properties were studied. Films produced on LNO/Si substrates have symmetrical non-ohmic current-voltage characteristics, while films deposited on Pt/Si substrates have a highly asymmetrical non-ohmic behavior which is related to a metal-semiconductor junction formed at the CCTO/Pt interface. In addition, results confirm that CCTO has a resistive switching response which is enhanced by Schottky contacts. Sensor response tests revealed that CCTO films are sensitive to oxygen gas and exhibit n-type conductivity. These results demonstrate the versatility of CCTO thin film prepared by the PPM method for gas atmosphere or bias dependent resistance applications.

Binary metal oxide nanoparticle incorporated composite multilayer thin films for sono-photocatalytic degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Gokul, Paramasivam; Vinoth, Ramalingam; Neppolian, Bernaurdshaw; Anandhakumar, Sundaramurthy

2017-10-01

We report reduced graphene oxide (rGO) supported binary metal oxide (CuO-TiO2/rGO) nanoparticle (NP) incorporated multilayer thin films based on Layer-by-Layer (LbL) assembly for enhanced sono-photocatalytic degradation of methyl orange under exposure to UV radiation. Multilayer thin films were fabricated on glass and quartz slides, and investigated using scanning electron microscopy and UV-vis spectroscopy. The loading of catalyst NPs on the film resulted in the change of morphology of the film from smooth to rough with uniformly distributed NPs on the surface. The growth of the control and NP incorporated films followed a linear regime as a function of number of layers. The%degradation of methyl orange as a function of time was investigated by UV-vis spectroscopy and total organic carbon (TOC) measurements. Complete degradation of methyl orange was achieved within 13 h. The amount of NP loading in the film significantly influenced the%degradation of methyl orange. Catalyst reusability studies revealed that the catalyst thin films could be repeatedly used for up to five times without any change in photocatalytic activity of the films. The findings of the present study support that the binary metal oxide catalyst films reported here are very useful for continuous systems, and thus, making it an option for scale up.

Epitaxial thin films of pyrochlore iridate Bi 2+xIr 2-yO 7-δ: structure, defects and transport properties

DOE PAGES

Yang, W. C.; Xie, Y. T.; Zhu, W. K.; ...

2017-08-10

While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. We report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi 2Ir 2O 7. Moreover, the films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of BiIr antisite defects,more » qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.« less

Epitaxial thin films of pyrochlore iridate Bi 2+xIr 2-yO 7-δ: structure, defects and transport properties

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

Yang, W. C.; Xie, Y. T.; Zhu, W. K.

While pyrochlore iridate thin films are theoretically predicted to possess a variety of emergent topological properties, experimental verification of these predictions can be obstructed by the challenge in thin film growth. We report on the pulsed laser deposition and characterization of thin films of a representative pyrochlore compound Bi 2Ir 2O 7. Moreover, the films were epitaxially grown on yttria-stabilized zirconia substrates and have lattice constants that are a few percent larger than that of the bulk single crystals. The film composition shows a strong dependence on the oxygen partial pressure. Density-functional-theory calculations indicate the existence of BiIr antisite defects,more » qualitatively consistent with the high Bi: Ir ratio found in the films. Both Ir and Bi have oxidation states that are lower than their nominal values, suggesting the existence of oxygen deficiency. The iridate thin films show a variety of intriguing transport characteristics, including multiple charge carriers, logarithmic dependence of resistance on temperature, antilocalization corrections to conductance due to spin-orbit interactions, and linear positive magnetoresistance.« less

Highly spectrum-selective ultraviolet photodetector based on p-NiO/n-IGZO thin film heterojunction structure.

PubMed

Li, H K; Chen, T P; Hu, S G; Li, X D; Liu, Y; Lee, P S; Wang, X P; Li, H Y; Lo, G Q

2015-10-19

Ultraviolet photodetector with p-n heterojunction is fabricated by magnetron sputtering deposition of n-type indium gallium zinc oxide (n-IGZO) and p-type nickel oxide (p-NiO) thin films on ITO glass. The performance of the photodetector is largely affected by the conductivity of the p-NiO thin film, which can be controlled by varying the oxygen partial pressure during the deposition of the p-NiO thin film. A highly spectrum-selective ultraviolet photodetector has been achieved with the p-NiO layer with a high conductivity. The results can be explained in terms of the "optically-filtering" function of the NiO layer.

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

Micropatterning of TiO2 thin films by MOCVD and study of their growth tendency.

PubMed

Hwang, Ki-Hwan; Kang, Byung-Chang; Jung, Duk Young; Kim, Youn Jea; Boo, Jin-Hyo

2015-03-23

In this work, we studied the growth tendency of TiO2 thin films deposited on a narrow-stripe area (<10 μm). TiO2 thin films were selectively deposited on OTS patterned Si(100) substrates by MOCVD. The experimental data showed that the film growth tendency was divided into two behaviors above and below a line patterning width of 4 μm. The relationship between the film thickness and the deposited area was obtained as a function of f(x) = a[1 - e((-bx))]c. To find the tendency of the deposition rate of the TiO2 thin films onto the various linewidth areas, the relationship between the thickness of the TiO2 thin film and deposited linewidth was also studied. The thickness of the deposited TiO2 films was measured from the alpha-step profile analyses and cross-sectional SEM images. At the same time, a computer simulation was carried out to reveal the relationship between the TiO2 film thickness and deposited line width. The theoretical results suggest that the mass (velocity) flux in flow direction is directly affected to the film thickness.

Structural and optical properties of gold-incorporated diamond-like carbon thin films deposited by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Majeed, Shahbaz; Siraj, K.; Naseem, S.; Khan, Muhammad F.; Irshad, M.; Faiz, H.; Mahmood, A.

2017-07-01

Pure and gold-doped diamond-like carbon (Au-DLC) thin films are deposited at room temperature by using RF magnetron sputtering in an argon gas-filled chamber with a constant flow rate of 100 sccm and sputtering time of 30 min for all DLC thin films. Single-crystal silicon (1 0 0) substrates are used for the deposition of pristine and Au-DLC thin films. Graphite (99.99%) and gold (99.99%) are used as co-sputtering targets in the sputtering chamber. The optical properties and structure of Au-DLC thin films are studied with the variation of gold concentration from 1%-5%. Raman spectroscopy, atomic force microscopy (AFM), Vickers hardness measurement (VHM), and spectroscopic ellipsometry are used to analyze these thin films. Raman spectroscopy indicates increased graphitic behavior and reduction in the internal stresses of Au-DLC thin films as the function of increasing gold doping. AFM is used for surface topography, which shows that spherical-like particles are formed on the surface, which agglomerate and form larger clusters on the surface by increasing the gold content. Spectroscopy ellipsometry analysis elucidates that the refractive index and extinction coefficient are inversely related and the optical bandgap energy is decreased with increasing gold content. VHM shows that gold doping reduces the hardness of thin films, which is attributed to the increase in sp2-hybridization.

Fabrication and characterization of functionalized surfaces with 3-amino propyltrimethoxysilane films for anti-infective therapy applications

NASA Astrophysics Data System (ADS)

Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Socol, Gabriel; Grumezescu, Alexandru Mihai; Ficai, Anton; Lazar, Veronica; Chifiriuc, Mariana Carmen; Trusca, Roxana; Iordache, Florin

2015-05-01

The purpose of this study was the fabrication of functionalized anti-adherent surfaces based on the polyvinyl chloride (PVC) coated with 3-amino propyltrimethoxysilane (APTMS) by matrix assisted pulsed laser evaporation (MAPLE) in order to improve the resistance of PVC based prosthetic devices to microbial colonization. Infrared microscopy (IRM) investigations of APTMS thin films proved the compositional homogeneity of the prepared thin film. Scanning electron microscopy (SEM) micrographs revealed a granular morphology with microspheres harboring a diameter between 15 and 60 nm. The microbiological assays proved that MAPLE deposited APTMS films inhibited the adherence capacity and biofilm development of Pseudomonas aeruginosa and Staphylococcus aureus strains. Furthermore, this material proved to be highly biocompatible, allowing the normal growth and development of human endothelial cells. These traits highlight the fact that the fabricated APTMS thin films may be efficiently used for improving different surfaces of medical use, including prostheses and implantable devices.

Energy deposition evaluation for ultra-low energy electron beam irradiation systems using calibrated thin radiochromic film and Monte Carlo simulations

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

Matsui, S., E-mail: smatsui@gpi.ac.jp; Mori, Y.; Nonaka, T.

2016-05-15

For evaluation of on-site dosimetry and process design in industrial use of ultra-low energy electron beam (ULEB) processes, we evaluate the energy deposition using a thin radiochromic film and a Monte Carlo simulation. The response of film dosimeter was calibrated using a high energy electron beam with an acceleration voltage of 2 MV and alanine dosimeters with uncertainty of 11% at coverage factor 2. Using this response function, the results of absorbed dose measurements for ULEB were evaluated from 10 kGy to 100 kGy as a relative dose. The deviation between the responses of deposit energy on the films andmore » Monte Carlo simulations was within 15%. As far as this limitation, relative dose estimation using thin film dosimeters with response function obtained by high energy electron irradiation and simulation results is effective for ULEB irradiation processes management.« less

Energy deposition evaluation for ultra-low energy electron beam irradiation systems using calibrated thin radiochromic film and Monte Carlo simulations.

PubMed

Matsui, S; Mori, Y; Nonaka, T; Hattori, T; Kasamatsu, Y; Haraguchi, D; Watanabe, Y; Uchiyama, K; Ishikawa, M

2016-05-01

For evaluation of on-site dosimetry and process design in industrial use of ultra-low energy electron beam (ULEB) processes, we evaluate the energy deposition using a thin radiochromic film and a Monte Carlo simulation. The response of film dosimeter was calibrated using a high energy electron beam with an acceleration voltage of 2 MV and alanine dosimeters with uncertainty of 11% at coverage factor 2. Using this response function, the results of absorbed dose measurements for ULEB were evaluated from 10 kGy to 100 kGy as a relative dose. The deviation between the responses of deposit energy on the films and Monte Carlo simulations was within 15%. As far as this limitation, relative dose estimation using thin film dosimeters with response function obtained by high energy electron irradiation and simulation results is effective for ULEB irradiation processes management.

Cytotoxicity Evaluation of Anatase and Rutile TiO2 Thin Films on CHO-K1 Cells in Vitro

PubMed Central

Cervantes, Blanca; López-Huerta, Francisco; Vega, Rosario; Hernández-Torres, Julián; García-González, Leandro; Salceda, Emilio; Herrera-May, Agustín L.; Soto, Enrique

2016-01-01

Cytotoxicity of titanium dioxide (TiO2) thin films on Chinese hamster ovary (CHO-K1) cells was evaluated after 24, 48 and 72 h of culture. The TiO2 thin films were deposited using direct current magnetron sputtering. These films were post-deposition annealed at different temperatures (300, 500 and 800 °C) toward the anatase to rutile phase transformation. The root-mean-square (RMS) surface roughness of TiO2 films went from 2.8 to 8.08 nm when the annealing temperature was increased from 300 to 800 °C. Field emission scanning electron microscopy (FESEM) results showed that the TiO2 films’ thickness values fell within the nanometer range (290–310 nm). Based on the results of the tetrazolium dye and trypan blue assays, we found that TiO2 thin films showed no cytotoxicity after the aforementioned culture times at which cell viability was greater than 98%. Independently of the annealing temperature of the TiO2 thin films, the number of CHO-K1 cells on the control substrate and on all TiO2 thin films was greater after 48 or 72 h than it was after 24 h; the highest cell survival rate was observed in TiO2 films annealed at 800 °C. These results indicate that TiO2 thin films do not affect mitochondrial function and proliferation of CHO-K1 cells, and back up the use of TiO2 thin films in biomedical science. PMID:28773740

Surface diffusion in homoepitaxial SrTiO3 thin films

NASA Astrophysics Data System (ADS)

Woo, Chang-Su; Chu, Kanghyun; Song, Jong-Hyun; Yang, Chan-Ho; Charm Lab Team; Nano Spintronics Lab Collaboration

The development of growth techniques such as molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) has facilitated growths of complex oxide thin films at the atomic level .... Systematic studies on surface diffusion process of adatoms using theoretical and experimental methods allow us to understand growth mechanism enabling atomically flat thin film surface. In this presentation, we introduce the synthesis of homoepitaxial SrTiO3 thin films using a PLD equipped with reflection of high energy electron diffraction (RHEED). We determine the surface diffusion time as a function of growth temperature and extract the activation energy of diffusion on the surface by in-situ monitoring the RHEED intensity recovery during the film deposition. From the extracted experimental results, we discuss the microscopic mechanism of the diffusion process

Effect of Using High Signal-to-Noise Image Intensifier Tubes on Night Vision Goggle (NVG) Aided Visual Acuity

DTIC Science & Technology

2006-05-01

tubes utilizing thin- filmed technology allowing for a higher SNR, and the F4949G goggles were tested. Twelve participants tested each goggle under six...LogMAR Visual Acuity as a Function of Illumination, Contrast, and NVG ........ 37 Repeated Measures Within-Subjects Analysis of Variance...auto-gated power supply and thin- filmed technology. The Pinnacle’sTM thin- filmed technology gave the image intensifier tube an increase in the signal-to

Highly ordered gold nanotubes using thiols at a cleavable block copolymer interface.

PubMed

Ryu, Ja-Hyoung; Park, Soojin; Kim, Bokyung; Klaikherd, Akamol; Russell, Thomas P; Thayumanavan, S

2009-07-29

We have prepared functionalized nanoporous thin films from a polystyrene-block-polyethylene oxide block copolymer, which was made cleavable due to the intervening disulfide bond. The cleavage reaction of the disulfide bond leaves behind free thiol groups inside the nanopores of polystyrene thin film. This nanoporous thin film can be used as a template for generating gold nanoring structures. This strategy can provide a facile method to form a highly ordered array of biopolymer or metal-polymer composite structures.

Substrate spacing and thin-film yield in chemical bath deposition of semiconductor thin films

NASA Astrophysics Data System (ADS)

Arias-Carbajal Reádigos, A.; García, V. M.; Gomezdaza, O.; Campos, J.; Nair, M. T. S.; Nair, P. K.

2000-11-01

Thin-film yield in the chemical bath deposition technique is studied as a function of separation between substrates in batch production. Based on a mathematical model, it is proposed and experimentally verified in the case of CdS thin films that the film thickness reaches an asymptotic maximum with increase in substrate separation. It is shown that at a separation less than 1 mm between substrates the yield, i.e. percentage in moles of a soluble cadmium salt deposited as a thin film of CdS, can exceed 50%. This behaviour is explained on the basis of the existence of a critical layer of solution near the substrate, within which the relevant ionic species have a higher probability of interacting with the thin-film layer than of contributing to precipitate formation. The critical layer depends on the solution composition and the temperature of the bath as well as the duration of deposition. An effective value for the critical layer thickness has been defined as half the substrate separation at which 90% of the maximum film thickness for the particular bath composition, bath temperature and duration of deposition is obtained. In the case of CdS thin films studied as an example, the critical layer is found to extend from 0.5 to 2.5 mm from the substrate surface, depending on the deposition conditions.

Ultrafast IR detector response in high Tc superconducting thin films

NASA Technical Reports Server (NTRS)

Lindgren, Mikael; Ahlberg, Henrik; Danerud, Martin; Larsson, Anders; Eng, Sverre T.

1991-01-01

The response from a high Tc superconducting multielement optical detector made of a laser deposited Y-Ba-Cu-O thin film has been evaluated. Several microscopic and spectroscopic techniques were used to establish the presence of the correct phase of the thin film. Optical pulses from a laser diode at 830 nm and from a Q-switched CO2-laser at 10.6 microns were used. The detector responded to 50 ps (FWHM) pulses. A comparison between dR/dT of the film and the response amplitude as a function of temperature indicated a bolometric response.

Advanced Catalysts for Fuel Cells

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram R.; Whitacre, Jay; Valdez, T. I.

2006-01-01

This viewgraph presentation reviews the development of catalyst for Fuel Cells. The objectives of the project are to reduce the cost of stack components and reduce the amount of precious metal used in fuel cell construction. A rapid combinatorial screening technique based on multi-electrode thin film array has been developed and validated for identifying catalysts for oxygen reduction; focus shifted from methanol oxidation in FY05 to oxygen reduction in FY06. Multi-electrode arrays of thin film catalysts of Pt-Ni and Pt-Ni-Zr have been deposited. Pt-Ni and have been characterized electrochemically and structurally. Pt-Ni-Zr and Pt-Ni films show higher current density and onset potential compared to Pt. Electrocatalytic activity and onset potential are found to be strong function of the lattice constant. Thin film Pt(59)Ni(39)Zr(2) can provide 10 times the current density of thin film Pt. Thin film Pt(59)Ni(39)Zr(2) also shows 65mV higher onset potential than Pt.

Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries

PubMed Central

Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M.

2015-01-01

Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g−1 and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices. PMID:26021485

Fabrication of flexible MoS2 thin-film transistor arrays for practical gas-sensing applications.

PubMed

He, Qiyuan; Zeng, Zhiyuan; Yin, Zongyou; Li, Hai; Wu, Shixin; Huang, Xiao; Zhang, Hua

2012-10-08

By combining two kinds of solution-processable two-dimensional materials, a flexible transistor array is fabricated in which MoS(2) thin film is used as the active channel and reduced graphene oxide (rGO) film is used as the drain and source electrodes. The simple device configuration and the 1.5 mm-long MoS(2) channel ensure highly reproducible device fabrication and operation. This flexible transistor array can be used as a highly sensitive gas sensor with excellent reproducibility. Compared to using rGO thin film as the active channel, this new gas sensor exhibits much higher sensitivity. Moreover, functionalization of the MoS(2) thin film with Pt nanoparticles further increases the sensitivity by up to ∼3 times. The successful incorporation of a MoS(2) thin-film into the electronic sensor promises its potential application in various electronic devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-temperature performance of MoS2 thin-film transistors: Direct current and pulse current-voltage characteristics

NASA Astrophysics Data System (ADS)

Jiang, C.; Rumyantsev, S. L.; Samnakay, R.; Shur, M. S.; Balandin, A. A.

2015-02-01

We report on fabrication of MoS2 thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS2 devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS2 thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a "memory step," was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS2 thin-film transistors demonstrated stable operation after two months of aging. The obtained results suggest new applications for MoS2 thin-film transistors in extreme-temperature electronics and sensors.

Composite films of oxidized multiwall carbon nanotube and poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) as a contact electrode for transistor and inverter devices.

PubMed

Yun, Dong-Jin; Rhee, Shi-Woo

2012-02-01

Composite films of multiwall carbon nanotube (MWNT)/poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS) were prepared by spin-coating a mixture solution. The effect of the MWNT loading and the MWNT oxidation, with acid solution or ultraviolet (UV)-ozone treatment, on the film properties such as surface roughness, work function, surface energy, optical transparency and conductivity were studied. Also pentacene thin film transistors and inverters were made with these composite films as a contact metal and the device characteristics were measured. The oxidation of MWNT reduced the conductivity of MWNT/PEDOT:PSS composite film but increased the work function and transparency. UV-ozone treated MWNT/PEDOT:PSS composite film showed higher conductivity (14000 Ω/□) and work function (4.9 eV) than acid-oxidized MWNT/PEDOT:PSS composite film and showed better performance as a source/drain electrode in organic thin film transistor (OTFT) than other types of MWNT/PEDOT:PSS composite films. Hole injection barrier of the UV-ozone treated MWNT/PEDOT:PSS composite film with pentacene was significantly lower than any other films because of the higher work function.

Structural and electrical properties of CZTS thin films by electrodeposition

NASA Astrophysics Data System (ADS)

Rao, M. C.; Basha, Sk. Shahenoor

2018-06-01

CZTS (Cu2ZnSnS4) thin films were coated on ITO glass substrates by single bath electrodeposition technique. The prepared films were subsequently characterized by XRD, SEM, FTIR, UV-visible spectroscopy and Raman studies. The thickness of the thin films was measured by wedge method. X-ray diffraction studies revealed the formation of polycrystalline phase. The morphological surface of the prepared thin films was examined by SEM and AFM and showed the presence of microcrystals on the surface of the samples. The elemental analysis and their compositional ratios present in the samples were confirmed by the energy dispersive X-ray analysis. Functional groups and the position of band structure involved in the materials were confirmed by FTIR. Optical absorption studies were performed on the prepared thin films in the wavelength ranging from 300 to 1000 nm and the energy bandgap values were found to be in the range from 1.39 to 1.60 eV. Raman spectral peak which was observed at 360 cm-1 correspond to kesterite phase, was formed due to the vibration of the molecules. Electrical measurements confirmed the nature of the thin film depending on the charge concentration present in the samples.

Influences of Indium Tin Oxide Layer on the Properties of RF Magnetron-Sputtered (BaSr)TiO3 Thin Films on Indium Tin Oxide-Coated Glass Substrate

NASA Astrophysics Data System (ADS)

Kim, Tae Song; Oh, Myung Hwan; Kim, Chong Hee

1993-06-01

Nearly stoichiometric ((Ba+Sr)/Ti=1.08-1.09) and optically transparent (BaSr)TiO3 thin films were deposited on an indium tin oxide (ITO)-coated glass substrate by means of rf magnetron sputtering for their application to the insulating layer of an electroluminescent flat panel display. The influence of the ITO layer on the properties of (BaSr)TiO3 thin films deposited on the ITO-coated substrate was investigated. The ITO layer did not affect the crystallographic orientation of (BaSr)TiO3 thin film, but enhanced the grain growth. Another effect of the ITO layer on (BaSr)TiO3 thin films was the interdiffusion phenomenon, which was studied by means of secondary ion mass spectrometry (SIMS). As the substrate temperature increased, interdiffusion intensified at the interface not only between the grown film and ITO layer but also between the ITO layer and base glass substrate. The refractive index (nf) of (BaSr)TiO3 thin film deposited on a bare glass substrate was 2.138-2.286, as a function of substrate temperature.

Thin film thermocouples for thermoelectric characterization of nanostructured materials

NASA Astrophysics Data System (ADS)

Grayson, Matthew; Zhou, Chuanle; Varrenti, Andrew; Chyung, Seung Hye; Long, Jieyi; Memik, Seda

2011-03-01

The increased use of nanostructured materials as thermoelectrics requires reliable and accurate characterization of the anisotropic thermal coefficients of small structures, such as superlattices and quantum wire networks. Thin evaporated metal films can be used to create thermocouples with a very small thermal mass and low thermal conductivity, in order to measure thermal gradients on nanostructures and thereby measure the thermal conductivity and the Seebeck coefficient of the nanostructure. In this work we confirm the known result that thin metal films have lower Seebeck coefficients than bulk metals, and we also calibrate the Seebeck coefficient of a thin-film Ni/Cr thermocouple with 50 nm thickness, showing it to have about 1/4 the bulk value. We demonstrate reproducibility of this thin-filmSeebeck coefficient on multiple substrates, and we show that this coefficient does, in fact, change as a function of film thickness. We will discuss prototype measurement designs and preliminary work as to how these thin films can be used to study both Seebeck coefficients and thermal conductivities of superlattices in various geometries. The same technology can in principle be used on integrated circuits for thermal mapping, under the name ``Integrated On-Chip Thermocouple Array'' (IOTA).

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.

Demonstration of thin film pair distribution function analysis (tfPDF) for the study of local structure in amorphous and crystalline thin films

DOE PAGES

Jensen, K. M.Ø.; Blichfeld, A. B.; Bauers, S. R.; ...

2015-07-05

By means of normal incidence, high flux and high energy x-rays, we have obtained total scattering data for Pair Distribution Function (PDF) analysis from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total scattering data through subtraction of an independently measured background signal. No angular corrections to the data are needed, as would be the case for grazing incidence measurements. We illustrate the ‘tfPDF’ method through studies of as depositedmore » (i.e. amorphous) and crystalline FeSb 3 films, where the local structure analysis gives insight into the stabilization of the metastable skutterudite FeSb 3 phase. The films were prepared by depositing ultra-thin alternating layers of Fe and Sb, which interdiffuse and after annealing crystallize to form the FeSb 3 structure. The tfPDF data show that the amorphous precursor phase consists of corner-sharing FeSb 6 octahedra with motifs highly resembling the local structure in crystalline FeSb 3. Analysis of the amorphous structure allows predicting whether the final crystalline product will form the FeSb 3 phase with or without excess Sb present. The study thus illustrates how analysis of the local structure in amorphous precursor films can help to understand crystallization processes of metastable phases and opens for a range of new local structure studies of thin films.« less

Demonstration of thin film pair distribution function analysis (tfPDF) for the study of local structure in amorphous and crystalline thin films

PubMed Central

Jensen, Kirsten M. Ø.; Blichfeld, Anders B.; Bauers, Sage R.; Wood, Suzannah R.; Dooryhée, Eric; Johnson, David C.; Iversen, Bo B.; Billinge, Simon J. L.

2015-01-01

By means of normal-incidence, high-flux and high-energy X-rays, total scattering data for pair distribution function (PDF) analysis have been obtained from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total scattering data through subtraction of an independently measured background signal. No angular corrections to the data are needed, as would be the case for grazing incidence measurements. The ‘tfPDF’ method is illustrated through studies of as-deposited (i.e. amorphous) and crystalline FeSb3 films, where the local structure analysis gives insight into the stabilization of the metastable skutterudite FeSb3 phase. The films were prepared by depositing ultra-thin alternating layers of Fe and Sb, which interdiffuse and after annealing crystallize to form the FeSb3 structure. The tfPDF data show that the amorphous precursor phase consists of corner-sharing FeSb6 octahedra with motifs highly resembling the local structure in crystalline FeSb3. Analysis of the amorphous structure allows the prediction of whether the final crystalline product will form the FeSb3 phase with or without excess Sb present. The study thus illustrates how analysis of the local structure in amorphous precursor films can help to understand crystallization processes of metastable phases and opens for a range of new local structure studies of thin films. PMID:26306190

Structural sensitivity of x-ray Bragg projection ptychography to domain patterns in epitaxial thin films

NASA Astrophysics Data System (ADS)

Hruszkewycz, S. O.; Zhang, Q.; Holt, M. V.; Highland, M. J.; Evans, P. G.; Fuoss, P. H.

2016-10-01

Bragg projection ptychography (BPP) is a coherent diffraction imaging technique capable of mapping the spatial distribution of the Bragg structure factor in nanostructured thin films. Here, we show that, because these images are projections, the structural sensitivity of the resulting images depends on the film thickness and the aspect ratio and orientation of the features of interest and that image interpretation depends on these factors. We model changes in contrast in the BPP reconstructions of simulated PbTiO3 ferroelectric thin films with meandering 180∘ stripe domains as a function of film thickness, discuss their origin, and comment on the implication of these factors on the design of BPP experiments of general nanostructured films.

Transparent Al+3 doped MgO thin films for functional applications

NASA Astrophysics Data System (ADS)

Maiti, Payel; Sekhar Das, Pradip; Bhattacharya, Manjima; Mukherjee, Smita; Saha, Biswajit; Mullick, Awadesh Kumar; Mukhopadhyay, Anoop Kumar

2017-08-01

The present work reports the utilization of a relatively simple, cost effective sol-gel technique based route to synthesize highly transparent, spin coated 4.1 at% Al+3 doped MgO thin films on quartz substrates. The films were characterized by XRD, XPS, Raman spectroscopy, and SIMS techniques. The microstructures were characterized by FESEM and TEM while the nanomechanical properties were assessed by the nanoindentation technique. Finally the optical transmittance was measured by UV-vis technique. The x-ray diffraction (XRD) study suggests the crystal facet (2 0 0) of MgO lattice to be distorted after incorporation of Al+3 into MgO lattice. From FESEM the doped films were found to have a dense microstructure with a crystallite size of about 20 nm as revealed by the TEM studies. Nanoindentation measurements indicated drastic increase of elastic modulus for the Al+3 doped MgO thin films by ~73% compared to that of the pristine MgO thin films along with retaining the nanohardness at ~8 GPa. The transmittance of Al+3 doped MgO thin films in the visible range was significantly higher (~99%) than that of pristine MgO (~90%) thin films. The films also had a relatively higher refractive index of about 1.45 as evaluated from the optical properties. The enhanced transmittance as well as the improved elastic modulus of Al+3 doped MgO thin films suggest its promising candidature in magnetic memory devices and as buffer layers of solar cells.

Structural, thermal, spectroscopic, and spectral dispersion studies of nanocrystalline methyl red thin films

NASA Astrophysics Data System (ADS)

Makhlouf, Mohamed M.; El-Denglawey, Adel

2018-04-01

Methyl red (MR) powder is polycrystalline structure as-purchased. The uniform, homogeneous and no cracks nano MR thin films are successfully prepared using thermal evaporation technique. The structural investigation for the pristine, annealed and UV irradiated MR films shows nanorods spread in amorphous medium. The part of as-prepared films exposed to UV light irradiation of wavelength 254 nm and intensity of 2000 µW/cm2 for 1 h, while the other part of films was treated by the annealing temperature at 178 °C for 1 h. The optical properties of MR thin films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the spectral range 200-2000 nm. The optical constants, dispersion parameters, and energy loss and dielectric functions of MR thin films were calculated and showed remarkable dependence on UV irradiation and annealing temperature upon the films of MR. The dependence of absorption coefficient on the photon energy were analyzed and the results showed that MR films undergo direct allowed optical transition for pristine, annealed and irradiated MR films.

Nanoindentation data analysis of loading curve performed on DLC thin films: Effect of residual stress on the elasto-plastic properties

NASA Astrophysics Data System (ADS)

Ouchabane, M.; Dublanche-Tixier, Ch.; Dergham, D.

2017-11-01

The present work is a contribution to the understanding of the mechanical behavior of DLC thin films through nanoindentation tests. DLC films of different thicknesses deposited by the PECVD process on a silicon substrate contain high residual compressive stresses when they are very thin and the stresses become relatively low and more relaxed as the film thickens. These different levels of residual stress influence the values of hardness (H) and Young's modulus (E) obtained when probing the film-substrate system by nanoindentation. It is observed that the DLC layers exhibit different mechanical behaviors even when they are deposited under the same conditions. It is proposed that the compressive stress induces structural modifications resulting in modifying the elasto-plastic properties of each thin film-substrate system. Data analysis of the loading curve can provide information on the elasto-plastic properties of DLC thin films, particularly the stiffness (S) and Er2/H, as a function of residual compressive stresses. The structural changes induced by residual stresses were probed by using Raman spectroscopy and correlated to the mechanical properties.

Nanocrystallization of LiCoO2 Cathodes for Thin Film Batteries Utilizing Pulse Thermal Processing

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

None

2009-04-01

This factsheet describes a study whose focus is on the nanocrystallization of the LiCoO2 cathode thin films on polyimide substrates and evaluate the microstructural evolution and resistance as a function of PTP processing conditions.

Atomic layer deposition synthesized TiO{sub x} thin films and their application as microbolometer active materials

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

Tanrikulu, Mahmud Yusuf, E-mail: mytanrikulu@adanabtu.edu.tr; Rasouli, Hamid Reza; Ghaffari, Mohammad

2016-05-15

This paper demonstrates the possible usage of TiO{sub x} thin films synthesized by atomic layer deposition as a microbolometer active material. Thin film electrical resistance is investigated as a function of thermal annealing. It is found that the temperature coefficient of resistance values can be controlled by coating/annealing processes, and the value as high as −9%/K near room temperature is obtained. The noise properties of TiO{sub x} films are characterized. It is shown that TiO{sub x} films grown by atomic layer deposition technique could have a significant potential to be used as a new active material for microbolometer-based applications.

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

Tesfaye, Meron; MacDonald, Andrew N.; Dudenas, Peter J.

Local gas transport limitation attributed to the ionomer thin-film in the catalyst layer is a major deterrent to widespread commercialization of polymer-electrolyte fuel cells. So far functionality and limitations of these thin-films have been assumed identical in the anode and cathode. In this study, Nafion ionomer thin-films on platinum(Pt) support were exposed to H 2 and air as model schemes, mimicking anode and cathode catalyst layers. Findings indicate decreased swelling, increased densification of ionomer matrix, and increased humidity-induced aging rates in reducing environment, compared to oxidizing and inert environments. Observed phenomenon could be related to underlying Pt-gas interaction dictating Pt-ionomermore » behavior. Presented results could have significant implications about the disparate behavior of ionomer thin-film in anode and cathode catalyst layers.« less

Nanoporous cerium oxide thin film for glucose biosensor.

PubMed

Saha, Shibu; Arya, Sunil K; Singh, S P; Sreenivas, K; Malhotra, B D; Gupta, Vinay

2009-03-15

Nanoporous cerium oxide (CeO(2)) thin film deposited onto platinum (Pt) coated glass plate using pulsed laser deposition (PLD) has been utilized for immobilization of glucose oxidase (GOx). Atomic force microscopy studies reveal the formation of nanoporous surface morphology of CeO(2) thin film. Response studies carried out using differential pulsed voltammetry (DPV) and optical measurements show that the GOx/CeO(2)/Pt bio-electrode shows linearity in the range of 25-300 mg/dl of glucose concentration. The low value of Michaelis-Menten constant (1.01 mM) indicates enhanced enzyme affinity of GOx to glucose. The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.

Optical Properties of Hybrid Inorganic/Organic Thin Film Encapsulation Layers for Flexible Top-Emission Organic Light-Emitting Diodes.

PubMed

An, Jae Seok; Jang, Ha Jun; Park, Cheol Young; Youn, Hongseok; Lee, Jong Ho; Heo, Gi-Seok; Choi, Bum Ho; Lee, Choong Hun

2015-10-01

Inorganic/organic hybrid thin film encapsulation layers consist of a thin Al2O3 layer together with polymer material. We have investigated optical properties of thin film encapsulation layers for top-emission flexible organic light-emitting diodes. The transmittance of hybrid thin film encapsulation layers and the electroluminescent spectrum of organic light-emitting diodes that were passivated by hybrid organic/inorganic thin film encapsulation layers were also examined as a function of the thickness of inorganic Al203 and monomer layers. The number of interference peaks, their intensity, and their positions in the visible range can be controlled by varying the thickness of inorganic Al2O3 layer. On the other hand, changing the thickness of monomer layer had a negligible effect on the optical properties. We also verified that there is a trade-off between transparency in the visible range and the permeation of water vapor in hybrid thin film encapsulation layers. As the number of dyads decreased, optical transparency improved while the water vapor permeation barrier was degraded. Our study suggests that, in top-emission organic light-emitting diodes, the thickness of each thin film encapsulation layer, in particular that of the inorganic layer, and the number of dyads should be controlled for highly efficient top-emission flexible organic light-emitting diodes.

Direct Observation of the BCC (100) Plane in Thin Films of Sphere-forming Diblock Copolymers

NASA Astrophysics Data System (ADS)

Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

2010-03-01

In sphere-forming diblock copolymers, periodic arrays of spheres are arranged in a body-centred cubic (BCC) lattice structure in bulk. However, in thin films different surface morphologies were observed as a function of the film thickness, and the transition from the hexagonal array to the BCC (110) arrangement of spheres on film surfaces was located with respect to the increase of the film thickness. Here we report the first direct observation of the BCC (100) plane in thin films of poly (styrene-b-methyl methacrylate) diblock copolymers on homogeneous substrates. By balancing the surface energies of both blocks, the lower energy BCC (100) plane corresponding to a square arrangement of half spheres, formed on film surfaces when the film thickness was commensurate with the spacing, L100, between (100) planes or greater than 2 L100. A hexagonal arrangement of spheres was only observed when the thickness was less than 2 L100 and incommensurate with 1 L100. Monte Carlo (MC) simulation confirmed our experimental observation and was used to investigate the transition of the arrangement of spheres as a function of the film thickness.

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.

Atmospheric Processing of Perovskite Solar Cells Using Intense Pulsed Light Sintering

NASA Astrophysics Data System (ADS)

Ankireddy, Krishnamraju; Lavery, Brandon W.; Druffel, Thad

2018-02-01

Atmospheric processing of metal-organic halide perovskite materials is highly desirable for large-scale manufacturing of solar cells. Atmospheric deposition and thermal processing of perovskite thin films for photovoltaic applications facilitated via rapid intense pulsed light (IPL) processing have been carried out. The interplay between the deposition chemistry, process, and IPL parameters to produce a functional photoactive thin film is discussed. Further addition of polyvinylpyrrolidone (PVP) as functional surfactant is explored to influence grain growth during the IPL process. Structural analysis by x-ray diffraction revealed formation of mixed-phase perovskite crystals from methylammonium chloride and lead iodide precursors. Ultraviolet-visible (UV-Vis) spectroscopy indicated that the light absorption by the perovskite films lay within a narrow band of the visible spectrum with bandgap of 2.9 eV. Scanning electron microscopy characterization of the surface morphology of the perovskite films revealed that addition of PVP to the ink chemistry assisted the IPL process in forming a fully covered surface with clearly defined grains. Functional devices with perovskite thin film processed by IPL under fully atmospheric conditions were demonstrated.

The effects of temperature on the surface resistivity of polyvinyl alcohol (PVA) thin films doped with silver nanoparticles and multi-walled carbon-nanotubes for optoelectronic and sensor applications

NASA Astrophysics Data System (ADS)

Polius, Jemilia R.

This thesis reports measurements of the temperature-dependent surface resistivity of multi-wall carbon nanotube doped polyvinyl alcohol (PVA) thin films. In the temperature range from 22°C to 40°C in a humidity controlled environment, it was found that the surface resistivity decreased initially but raised as the temperature continued to increase. I report surface resistivity measurements as a function of temperature of both multiwall and single-wall carbon nanotube doped PVA thin films, with comparison of the similarities and differences between the two types of film types. This research was conducted using the combined instrumentation of the KEITHLEY Model 6517 Electrometer and the KEITHLEY Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films.

Method for making thin polypropylene film

DOEpatents

Behymer, R.D.; Scholten, J.A.

1985-11-21

An economical method is provided for making uniform thickness polypropylene film as thin as 100 Angstroms. A solution of polypropylene dissolved in xylene is formed by mixing granular polypropylene and xylene together in a flask at an elevated temperature. A substrate, such as a glass plate or microscope slide is immersed in the solution. When the glass plate is withdrawn from the solution at a uniform rate, a thin polypropylene film forms on a flat surface area of the glass plate as the result of xylene evaporation. The actual thickness of the polypropylene film is functional of the polypropylene in xylene solution concentration, and the particular withdrawal rate of the glass plate from the solution. After formation, the thin polypropylene film is floated from the glass plate onto the surface of water, from which it is picked up with a wire hoop.

Critical Role of Surface Energy in Guiding Crystallization of Solution-Coated Conjugated Polymer Thin Films

DOE PAGES

Zhang, Fengjiao; Mohammadi, Erfan; Luo, Xuyi; ...

2017-10-02

It is well-known that substrate surface properties have a profound impact on morphology of thin films solution coated atop and the resulting solid-state properties. However, design rules for guiding the substrate selection have not yet been established. Such design rules are particularly important for solution coated semiconducting polymers, as the substratedirected thin film morphology can impact charge transport properties by orders of magnitude. We hypothesize that substrate surface energies dictate the thin film morphology by modulating the free energy barrier to heterogeneous nucleation. To test this hypothesis, we systematically vary the substrate surface energy via surface functionalization techniques. We performmore » in-depth morphology and device characterizations to establish the relationship between substrate surface energy, thin film morphology and charge transport properties, employing a donor-accepter (D-A) conjugated polymer. Here, we find that decreasing the substrate surface energy progressively increases thin film crystallinity, degree of molecular ordering and extent of domain alignment. Notably, the enhanced morphology on the lowest surface energy substrate lead to a 10-fold increase in the charge carrier mobility. We further develop a free energy model relating the substrate surface energy to the penalty of heterogeneous nucleation from solution in the thin film geometry. The model correctly predicts the experimental trend, thereby validating our hypothesis. This work is a significant step towards establishing design rules and understanding the critical role of substrates in determining morphology of solution coated thin films.« less

Critical Role of Surface Energy in Guiding Crystallization of Solution-Coated Conjugated Polymer Thin Films

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

Zhang, Fengjiao; Mohammadi, Erfan; Luo, Xuyi

It is well-known that substrate surface properties have a profound impact on morphology of thin films solution coated atop and the resulting solid-state properties. However, design rules for guiding the substrate selection have not yet been established. Such design rules are particularly important for solution coated semiconducting polymers, as the substratedirected thin film morphology can impact charge transport properties by orders of magnitude. We hypothesize that substrate surface energies dictate the thin film morphology by modulating the free energy barrier to heterogeneous nucleation. To test this hypothesis, we systematically vary the substrate surface energy via surface functionalization techniques. We performmore » in-depth morphology and device characterizations to establish the relationship between substrate surface energy, thin film morphology and charge transport properties, employing a donor-accepter (D-A) conjugated polymer. Here, we find that decreasing the substrate surface energy progressively increases thin film crystallinity, degree of molecular ordering and extent of domain alignment. Notably, the enhanced morphology on the lowest surface energy substrate lead to a 10-fold increase in the charge carrier mobility. We further develop a free energy model relating the substrate surface energy to the penalty of heterogeneous nucleation from solution in the thin film geometry. The model correctly predicts the experimental trend, thereby validating our hypothesis. This work is a significant step towards establishing design rules and understanding the critical role of substrates in determining morphology of solution coated thin films.« less

PZT Thin-Film Micro Probe Device with Dual Top Electrodes

NASA Astrophysics Data System (ADS)

Luo, Chuan

Lead zirconate titanate (PZT) thin-film actuators have been studied intensively for years because of their potential applications in many fields. In this dissertation, a PZT thin-film micro probe device is designed, fabricated, studied, and proven to be acceptable as an intracochlear acoustic actuator. The micro probe device takes the form of a cantilever with a PZT thin-film diaphragm at the tip of the probe. The tip portion of the probe will be implanted in cochlea later in animal tests to prove its feasibility in hearing rehabilitation. The contribution of the dissertation is three-fold. First, a dual top electrodes design, consisting of a center electrode and an outer electrode, is developed to improve actuation displacement of the PZT thin-film diaphragm. The improvement by the dual top electrodes design is studied via a finite element model. When the dimensions of the dual electrodes are optimized, the displacement of the PZT thin-film diaphragm increases about 30%. A PZT thin-film diaphragm with dual top electrodes is fabricated to prove the concept, and experimental results confirm the predictions from the finite element analyses. Moreover, the dual electrode design can accommodate presence of significant residual stresses in the PZT thin-film diaphragm by changing the phase difference between the two electrodes. Second, a PZT thin-film micro probe device is fabricated and tested. The fabrication process consists of PZT thin-film deposition and deep reactive ion etching (DRIE). The uniqueness of the fabrication process is an automatic dicing mechanism that allows a large number of probes to be released easily from the wafer. Moreover, the fabrication is very efficient, because the DRIE process will form the PZT thin-film diaphragm and the special dicing mechanism simultaneously. After the probes are fabricated, they are tested with various possible implantation depths (i.e., boundary conditions). Experimental results show that future implantation depths should be less than 3 mm in order to guarantee the first resonant frequency above 60 kHz. Finally, a package for the PZT thin-film micro probe device is developed to ensure its proper function in an aqueous environment, such as inside of cochlea. The package is an insulation layer of parylene coating on the probe. A finite element analysis indicates that a coating thickness of less than 1 mum will reduce the PZT diaphragm displacement by less than 10%. A special fixture is designed to hold a large number of probes for parylene deposition of a thickness of 250 nm. A packaged probe is then submerged in deionized water and functions properly for at least 55 hours. Displacement and impedance of the probe are measured via a laser Doppler vibrometer and an impedance analyzer, respectively. Experimental results show that displacement of the PZT diaphragm increases about 30% in two hours, after the probe is submerged in the deionized water. The impedance measurement shows consistent trends. A hypothesis to explain this unusual phenomenon is diffusion of water molecules into the PZT thin film. High-resolution SEM images of the probe indicate presence of numerous nano-pores in the surface of the PZT thin film, indirectly confirming the hypothesis. Keywords: PZT, Thin-Film, Dual Electrodes, Parylene Coating, Aqueous Environment, Cochlear Implant

High-throughput characterization of stresses in thin film materials libraries using Si cantilever array wafers and digital holographic microscopy.

PubMed

Lai, Y W; Hamann, S; Ehmann, M; Ludwig, A

2011-06-01

We report the development of an advanced high-throughput stress characterization method for thin film materials libraries sputter-deposited on micro-machined cantilever arrays consisting of around 1500 cantilevers on 4-inch silicon-on-insulator wafers. A low-cost custom-designed digital holographic microscope (DHM) is employed to simultaneously monitor the thin film thickness, the surface topography and the curvature of each of the cantilevers before and after deposition. The variation in stress state across the thin film materials library is then calculated by Stoney's equation based on the obtained radii of curvature of the cantilevers and film thicknesses. DHM with nanometer-scale out-of-plane resolution allows stress measurements in a wide range, at least from several MPa to several GPa. By using an automatic x-y translation stage, the local stresses within a 4-inch materials library are mapped with high accuracy within 10 min. The speed of measurement is greatly improved compared with the prior laser scanning approach that needs more than an hour of measuring time. A high-throughput stress measurement of an as-deposited Fe-Pd-W materials library was evaluated for demonstration. The fast characterization method is expected to accelerate the development of (functional) thin films, e.g., (magnetic) shape memory materials, whose functionality is greatly stress dependent. © 2011 American Institute of Physics

Ultrathin Polymer Films, Patterned Arrays, and Microwells

NASA Astrophysics Data System (ADS)

Yan, Mingdi

2002-05-01

The ability to control and tailor the surface and interface properties of materials is important in microelectronics, cell growth control, and lab-on-a-chip devices. Modification of material surfaces with ultrathin polymer films is attractive due to the availability of a variety of polymers either commercially or by synthesis. We have developed two approaches to the attachment of ultrathin polymer films on solid substrates. In the first method, a silane-functionalized perfluorophenyl azide (PFPA-silane) was synthesized and used to covalently immobilize polymer thin films on silicon wafers. Silanization of the wafer surface with the PFPA-silane introduced a monolayer of azido groups which in turn covalently attached the polymer film by way of photochemically initiated insertion reactions. The thickness of the film could be adjusted by the type and the molecular weight of the polymer. The method is versatile due to the general C-H and/or N-H insertion reactions of crosslinker; and therefore, no specific reactive functional groups on the polymers are required. Using this method, a new type of microwell array was fabricated from covalently immobilized polymer thin films on flat substrates. The arrays were characterized with AFM, XPS, and TOF-SIMS. The second method describes the attachment of polymer thin films on solid substrates via UV irradiation. The procedure consisted of spin-coating a polymer film and irradiating the film with UV light. Following solvent extraction, a thin film remained. The thickness of the film, from a few to over a hundred nanometers, was controlled by varying solution concentration and the molecular weight of the polymer.

Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

NASA Astrophysics Data System (ADS)

Karaduman, Irmak; Çorlu, Tugba; Yıldırım, M. Ali; Ateş, Aytunç; Acar, Selim

2017-07-01

Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

Conformal self-assembled thin films for optical pH sensors

NASA Astrophysics Data System (ADS)

Topasna, Daniela M.; Topasna, Gregory A.; Liu, Minghanbo; Tseng, Ching-Hung

2016-04-01

Simple, reliable, lightweight, and inexpensive thin films based sensors are still in intense development and high demand in many applications such as biomedical, industrial, environmental, military, and consumer products. One important class of sensors is the optical pH sensor. In addition, conformal thin film based sensors extend the range of application for pH optical sensors. We present the results on the fabrication and characterization of optical pH sensing coatings made through ionic self-assembled technique. These thin films are based on the combination of a polyelectrolyte and water-soluble organic dye molecule Direct Yellow 4. A series of films was fabricated and characterized in order to determine the optimized parameters of the polymer and of the organic dye solutions. The optical pH responses of these films were also studied. The transparent films were immersed in solutions at various temperature and pH values. The films are stable when immersed in solutions with pH below 9.0 and temperatures below 90 °C and they maintain their performance after longer immersion times. We also demonstrate the functionality of these coatings as conformal films.

Structural and optical studied of nano structured lead sulfide thin films prepared by the chemical bath deposition technique

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

Al Din, Nasser Saad, E-mail: nsaadaldin@yahoo.com; Hussain, Nabiha, E-mail: nabihahssin@yahoo.com; Jandow, Nidhal, E-mail: nidhaljandow@yahoo.com

2016-07-25

Lead (II) Sulfide PbS thin films were deposited on glass substrates at 25°C by chemical bath deposition (CBD) method. The structural properties of the films were studied as a function of the concentration of Thiourea (CS (NH{sub 2}){sub 2}) as Source of Sulfide and deposition time. The surface morphology of the films was characterized by X-ray diffraction and SEM. The obtained results showed that the as-deposited films Polycrystalline had cubic crystalline phase that belong to S.G: Fm3m. We found that they have preferred orientation [200]. Also the thickness of thin films decrease with deposition time after certain value and, itmore » observed free sulfide had orthorhombic phase. Optical properties showed that the thin films have high transmission at visible range and low transmission at UV, IR range. The films of PbS have direct band gap (I.68 - 2.32 ev) at 300 K the values of band energy decreases with increases thickness of the Lead (II) Sulfide films.« less

Structural, electronic transport and optical properties of Cr doped PbS thin film by chemical bath deposition

NASA Astrophysics Data System (ADS)

Preetha, K. C.

2017-06-01

Incorporation of Chromium ions into Lead Sulphide thin films have been achieved by CBD technique. Effects of doping were investigated as a function of Pb/Cr ratio from o to 2 at %. X-ray diffraction patterns showed that films were polycrystalline in nature with increase in crystallite size up to an optimum doping concentration. Scanning electron microscopic study revealed excellent morphology with doping concentration. The low transmittance in the UV-VIS region offered the suitability of the samples as solar control coatings. The thin films were found to be P type and electrical conductivity enhanced on doping.

{ital In-situ} x-ray investigation of hydrogen charging in thin film bimetallic electrodes

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

Jisrawi, N.M.; Wiesmann, H.; Ruckman, M.W.

Hydrogen uptake and discharge by thin metallic films under potentiostatic control was studied using x-ray diffraction at the National Synchrotron Light Source (NSLS). The formation of metal-hydrogen phases in Pd, Pd-capped Nb and Pd/Nb multilayer electrode structures was deduced from x-ray diffraction data and correlated with the cyclic voltammetry (CV) peaks. The x-ray data was also used to construct a plot of the hydrogen concentration as a function of cell potential for a multilayered thin film. {copyright} {ital 1997 Materials Research Society.}

Measurement of incident molecular temperature in the formation of organic thin films

NASA Astrophysics Data System (ADS)

Abe, Takahiro; Matsubara, Ryosuke; Hayakawa, Munetaka; Shimoyama, Akifumi; Tanaka, Takaaki; Tsuji, Akira; Takahashi, Yoshikazu; Kubono, Atsushi

2018-03-01

To investigate the effects of incident molecular temperature on organic-thin-film growth by vacuum evaporation, quantitative analysis of molecular temperature is required. In this study, we propose a method of determining molecular temperature based on the heat exchange between a platinum filament and molecular vapor. Molecular temperature is estimated from filament temperature, which remains unchanged even under molecular vapor supply. The results indicate that our method has sufficient sensitivity to evaluate the molecular temperature under the typical growth rate used for fabrication of functional organic thin films.

Polarized optical scattering by inhomogeneities and surface roughness in an anisotropic thin film.

PubMed

Germer, Thomas A; Sharma, Katelynn A; Brown, Thomas G; Oliver, James B

2017-11-01

We extend the theory of Kassam et al. [J. Opt. Soc. Am. A12, 2009 (1995)JOAOD60740-323210.1364/JOSAA.12.002009] for scattering by oblique columnar structure thin films to include the induced form birefringence and the propagation of radiation in those films. We generalize the 4×4 matrix theory of Berreman [J. Opt. Soc. Am.62, 502 (1972)JOSAAH0030-394110.1364/JOSA.62.000502] to include arbitrary sources in the layer, which are necessary to determine the Green function for the inhomogeneous wave equation. We further extend first-order vector perturbation theory for scattering by roughness in the smooth surface limit, when the layer is anisotropic. Scattering by an inhomogeneous medium is approximated by a distorted Born approximation, where effective medium theory is used to determine the effective properties of the medium, and strong fluctuation theory is used to determine the inhomogeneous sources. In this manner, we develop a model for scattering by inhomogeneous films, with anisotropic correlation functions. The results are compared with Mueller matrix bidirectional scattering distribution function measurements for a glancing-angle deposition (GLAD) film. While the results are applied to the GLAD film example, the development of the theory is general enough that it can guide simulations for scattering in other anisotropic thin films.

Solution processable semiconductor thin films: Correlation between morphological, structural, optical and charge transport properties

NASA Astrophysics Data System (ADS)

Isik, Dilek

This Ph.D. thesis is a result of multidisciplinary research bringing together fundamental concepts in thin film engineering, materials science, materials processing and characterization, electrochemistry, microfabrication, and device physics. Experiments were conducted by tackling scientific problems in the field of thin films and interfaces, with the aim to correlate the morphology, crystalline structure, electronic structure of thin films with the functional properties of the films and the performances of electronic devices based thereon. Furthermore, novel strategies based on interfacial phenomena at electrolyte/thin film interfaces were explored and exploited to control the electrical conductivity of the thin films. Three main chemical systems were the object of the studies performed during this Ph.D., two types of organic semiconductors (azomethine-based oligomers and polymers and soluble pentacene derivatives) and one metal oxide semiconductor (tungsten trioxide, WO3). To explore the morphological properties of the thin films, atomic force microscopy was employed. The morphological properties were further investigated by hyperspectral fluorescence microscopy and tentatively correlated to the charge transport properties of the films. X-ray diffraction (Grazing incidence XRD, GIXRD) was used to investigate the crystallinity of the film and the effect of the heat treatment on such crystallinity, as well as to understand the molecular arrangement of the organic molecules in the thin film. The charge transport properties of the films were evaluated in thin film transistor configuration. For electrolyte gated thin film transistors, time dependent transient measurements were conducted, in parallel to more conventional transistor characterizations, to explore the specific effects played on the gating by the anion and cation constituting the electrolyte. The capacitances of the electrical double layers at the electrolyte/WO3 interface were obtained from electrochemical impedance spectroscopy. In the context of ARTICLE 1, thin film transistors based on soluble pentacene derivatives (prepared by the research group directed by Professor J. Anthony, at the University of Kentucky) were fabricated and characterized. GIXRD results performed on the thin films suggested a molecular arrangement favorable to charge transport in the source-drain direction, with the pi-pi stacking direction perpendicular to the channel. In ARTICLE 1, HMDS-treated SiO 2 substrates were used, to improve the surface coverage and to limit charge trapping at the dielectric surface. AFM showed good film coverage. The transistors showed ambipolar characteristics, attributed to the good matching between Au electrode work function and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the pentacene derivative. The work reported in ARTICLE 2 deals with pi-conjugated thiopheno-azomethines (both in oligomer and polymer form) and oligothiophene analogues. In the former case, couplings in the polymer are based on azomethine (-N=C-) moieties whereas in the latter case they are based on more conventional protocols (-C=C-). The effect of the coupling protocols on the corresponding thin film transistors behavior was studied. The key conclusion of this study was that thiopheno-azomethines thin films can be effectively incorporated into organic transistors: thin films of oligothiopheno-azomethines and the oligothiophenes exhibit p-type behavior whereas thin films of polythiopheno-azomethine exhibit an ambipolar behavior. The hole mobility of the heat-treated thin films of oligothiopheno-azomethines was three orders of magnitude higher compared to its oligothiophene analogue. AFM, coupled with hyperspectral fluorescence imaging, were used to investigate the micro- and nano-scale surface coverage. For the oligothiopheno-azomethine we were able to quantitatively deduce the surface coverage. To contribute to the exploration of innovative strategies for low power consuming solution based electronics and capitalizing on the expertise of the group in the synthesis of solution deposited WO3 films the electrolyte gating approach was explored in ARTICLE 3. Ionic liquids, that are molten salts at room temperature, were employed as the electrolyte. Ionic liquids are attractive for their low volatility, non-flammability, ionic conductivity and thermal and electrochemical stability. Thin films of WO3 were deposited onto pre-patterned ITO substrates (source-drain interelectrode distance, 1 mm) prepared by wet chemical etching. SEM and AFM showed an interconnected film nanostructure. Electrolyte gated WO3 thin film transistors making use of 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]), 1-butyl-3-methyl imidazolium hexafluoro phosphate ([BMIM][PF6]), and 1-ethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) showed an n-type transistor behavior. The possibility to obtain WO3 electrolyte gated transistors represents an opportunity to fabricate electronic devices working at relatively low operating voltages (about 1 V) by using simple fabrication techniques.

Direct measurement of intrinsic critical strain and internal strain in barrier films

NASA Astrophysics Data System (ADS)

Vellinga, W. P.; De Hosson, J. Th. M.; Bouten, P. C. P.

2011-08-01

Resistance measurements during uniaxial tensile deformation of very thin (10 nm) conducting oxide films deposited on 150 nm SiN films on polyethylene naphthalate are discussed. It is first shown that certain characteristics of resistance versus strain curves are representative for the fracture behavior of the SiN film and not for that of the thin conducting oxide film. Subsequently, it is shown that the hysteresis in curves of resistance as a function of strain offers a way to directly measure the intrinsic critical strain of the SiN film without the need to determine internal strains from independent (curvature) measurements that rely on knowledge of moduli and geometry. The method should be applicable, in general, to measure intrinsic critical strain and residual strains of thin brittle films on polymers. Advantages and limitations of the method are discussed.

Structural sensitivity of x-ray Bragg projection ptychography to domain patterns in epitaxial thin films

DOE PAGES

Hruszkewycz, S. O.; Zhang, Q.; Holt, M. V.; ...

2016-10-04

Bragg projection ptychography (BPP) is a coherent diffraction imaging technique capable of mapping the spatial distribution of the Bragg structure factor in nanostructured thin films. Here, we show that, because these images are projections, the structural sensitivity of the resulting images depends on the film thickness and the aspect ratio and orientation of the features of interest and that image interpretation depends on these factors. Lastly, we model changes in contrast in the BPP reconstructions of simulated PbTiO 3 ferroelectric thin films with meandering 180° stripe domains as a function of film thickness, discuss their origin, and comment on themore » implication of these factors on the design of BPP experiments of general nanostructured films.« less

Layer-by-layer assembled polyaniline nanofiber/multiwall carbon nanotube thin film electrodes for high-power and high-energy storage applications.

PubMed

Hyder, Md Nasim; Lee, Seung Woo; Cebeci, Fevzi Ç; Schmidt, Daniel J; Shao-Horn, Yang; Hammond, Paula T

2011-11-22

Thin film electrodes of polyaniline (PANi) nanofibers and functionalized multiwall carbon nanotubes (MWNTs) are created by layer-by-layer (LbL) assembly for microbatteries or -electrochemical capacitors. Highly stable cationic PANi nanofibers, synthesized from the rapid aqueous phase polymerization of aniline, are assembled with carboxylic acid functionalized MWNT into LbL films. The pH-dependent surface charge of PANi nanofibers and MWNTs allows the system to behave like weak polyelectrolytes with controllable LbL film thickness and morphology by varying the number of bilayers. The LbL-PANi/MWNT films consist of a nanoscale interpenetrating network structure with well developed nanopores that yield excellent electrochemical performance for energy storage applications. These LbL-PANi/MWNT films in lithium cell can store high volumetric capacitance (~238 ± 32 F/cm(3)) and high volumetric capacity (~210 mAh/cm(3)). In addition, rate-dependent galvanostatic tests show LbL-PANi/MWNT films can deliver both high power and high energy density (~220 Wh/L(electrode) at ~100 kW/L(electrode)) and could be promising positive electrode materials for thin film microbatteries or electrochemical capacitors. © 2011 American Chemical Society

The effect of solvent upon molecularly thin rotaxane film formation

NASA Astrophysics Data System (ADS)

Farrell, Alan A.; Kay, Euan R.; Bottari, Giovanni; Leigh, David A.; Jarvis, Suzanne P.

2007-05-01

We have investigated variations in molecularly thin rotaxane films deposited by solvent evaporation, using atomic force microscopy (AFM). Small changes in rotaxane structure result in significant differences in film morphology. The addition of exo-pyridyl moietes to the rotaxane macrocycle results in uniform domains having orientations corresponding to the underlying substrate lattice, while a larger, less symmetric molecule results in a greater lattice mismatch and smaller domain sizes. We have measured differences in film heights both as a function of the solvent of deposition and as a function of surface coverage of rotaxanes. Based on these observations we describe how the use of solvents with higher hydrogen-bond basicity results in films which are more likely to favour sub-molecular motion.

Elastic Moduli of Nanoparticle-Polymer Composite Thin Films via Buckling on Elastomeric Substrates

NASA Astrophysics Data System (ADS)

Yuan, Hongyi; Karim, Alamgir; University of Akron Team

2011-03-01

Polymeric thin films find applications in diverse areas such as coatings, barriers and packaging. The dispersion of nanoparticles into the films was proven to be an effective method to generate tunable properties, particularly mechanical strength. However, there are very few methods for mechanical characterization of the composite thin films with high accuracy. In this study, nanometric polystyrene and polyvinyl alcohol films with uniformly dispersed cobalt and Cloisite nanoparticles at varying concentrations were synthesized via flow-coating and then transferred to crosslinked polydimethylsiloxane (PDMS) flexible substrates. The technique of Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) was employed to determine the elastic moduli of the films, which were calculated from the buckling patterns generated by applying compressive stresses. Results on moduli of films as a function of the concentrations of nanoparticles and the thicknesses of the composite films will be presented. *Corresponding author: alamgir@uakron.edu

Voltage Scaling of Graphene Device on SrTiO3 Epitaxial Thin Film.

PubMed

Park, Jeongmin; Kang, Haeyong; Kang, Kyeong Tae; Yun, Yoojoo; Lee, Young Hee; Choi, Woo Seok; Suh, Dongseok

2016-03-09

Electrical transport in monolayer graphene on SrTiO3 (STO) thin film is examined in order to promote gate-voltage scaling using a high-k dielectric material. The atomically flat surface of thin STO layer epitaxially grown on Nb-doped STO single-crystal substrate offers good adhesion between the high-k film and graphene, resulting in nonhysteretic conductance as a function of gate voltage at all temperatures down to 2 K. The two-terminal conductance quantization under magnetic fields corresponding to quantum Hall states survives up to 200 K at a magnetic field of 14 T. In addition, the substantial shift of charge neutrality point in graphene seems to correlate with the temperature-dependent dielectric constant of the STO thin film, and its effective dielectric properties could be deduced from the universality of quantum phenomena in graphene. Our experimental data prove that the operating voltage reduction can be successfully realized due to the underlying high-k STO thin film, without any noticeable degradation of graphene device performance.

LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

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

Bagul, Sagar B., E-mail: nano.sbbagul@gmail.com; Upadhye, Deepak S.; Sharma, Ramphal, E-mail: rps.phy@gmail.com

Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology ofmore » Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.« less

Highly flexible electronics from scalable vertical thin film transistors.

PubMed

Liu, Yuan; Zhou, Hailong; Cheng, Rui; Yu, Woojong; Huang, Yu; Duan, Xiangfeng

2014-03-12

Flexible thin-film transistors (TFTs) are of central importance for diverse electronic and particularly macroelectronic applications. The current TFTs using organic or inorganic thin film semiconductors are usually limited by either poor electrical performance or insufficient mechanical flexibility. Here, we report a new design of highly flexible vertical TFTs (VTFTs) with superior electrical performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 10(5). The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. With large area graphene and IGZO thin film available, our strategy is intrinsically scalable for large scale integration of VTFT arrays and logic circuits, opening up a new pathway to highly flexible macroelectronics.

Observation of oscillatory relaxation in the Sn-terminated surface of epitaxial rock-salt SnSe { 111 } topological crystalline insulator

NASA Astrophysics Data System (ADS)

Jin, Wencan; Dadap, Jerry; Osgood, Richard; Vishwanath, Suresh; Lien, Huai-Hsun; Chaney, Alexander; Xing, Huili; Liu, Jianpeng; Kong, Lingyuan; Ma, Junzhang; Qian, Tian; Ding, Hong; Sadowski, Jerzy; Dai, Zhongwei; Pohl, Karsten; Lou, Rui; Wang, Shancai; Liu, Xinyu; Furdyna, Jacek

Topological crystalline insulators have been recently observed in rock-salt SnSe { 111 } thin films. Previous studies have suggested that the Se-terminated surface of this thin film with hydrogen passivation is a preferred configuration. In this work, synchrotron-based angle-resolved photoemission spectroscopy, along with density functional theory calculations, are used to demonstrate conclusively that a rock-salt SnSe { 111 } thin film has a stable Sn-terminated surface. These observations are supported by low energy electron diffraction (LEED) intensity-voltage measurements and dynamical LEED calculations, which further show that the Sn-terminated SnSe { 111 } thin film has undergone an oscillatory surface structural relaxation. In sharp contrast to the Se-terminated counterpart, the Dirac surface state in the Sn-terminated SnSe { 111 } thin film yields a high Fermi velocity, 0 . 50 ×106 m/s, which may lead to high-speed electronic device applications. DOE No. DE-FG 02-04-ER-46157.

Step-by-step fabrication of a highly oriented crystalline three-dimensional pillared-layer-type metal-organic framework thin film confirmed by synchrotron X-ray diffraction.

PubMed

Otsubo, Kazuya; Haraguchi, Tomoyuki; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

2012-06-13

Fabrication of a crystalline ordered thin film based on the porous metal-organic frameworks (MOFs) is one of the practical applications of the future functional nanomaterials. Here, we report the creation of a highly oriented three-dimensional (3-D) porous pillared-layer-type MOF thin film on a metal substrate using a step-by-step approach based on liquid-phase epitaxy. Synchrotron X-ray diffraction (XRD) study clearly indicates that the thin film is crystalline and its orientation is highly controlled in both horizontal and vertical directions relative to the substrate. This report provides the first confirmation of details of not only the crystallinity but also the orientation of 3-D MOF thin film using synchrotron XRD. Moreover, we also demonstrate its guest adsorption/desorption behavior by using in situ XRD measurements. The results presented here would promise useful insights for fabrication of MOF-based nanodevices in the future.

LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

NASA Astrophysics Data System (ADS)

Bagul, Sagar B.; Upadhye, Deepak S.; Sharma, Ramphal

2016-05-01

Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology of Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.

Silicon solar cell performance deposited by diamond like carbon thin film ;Atomic oxygen effects;

NASA Astrophysics Data System (ADS)

Aghaei, Abbas Ail; Eshaghi, Akbar; Karami, Esmaeil

2017-09-01

In this research, a diamond-like carbon thin film was deposited on p-type polycrystalline silicon solar cell via plasma-enhanced chemical vapor deposition method by using methane and hydrogen gases. The effect of atomic oxygen on the functioning of silicon coated DLC thin film and silicon was investigated. Raman spectroscopy, field emission scanning electron microscopy, atomic force microscopy and attenuated total reflection-Fourier transform infrared spectroscopy were used to characterize the structure and morphology of the DLC thin film. Photocurrent-voltage characteristics of the silicon solar cell were carried out using a solar simulator. The results showed that atomic oxygen exposure induced the including oxidation, structural changes, cross-linking reactions and bond breaking of the DLC film; thus reducing the optical properties. The photocurrent-voltage characteristics showed that although the properties of the fabricated thin film were decreased after being exposed to destructive rays, when compared with solar cell without any coating, it could protect it in atomic oxygen condition enhancing solar cell efficiency up to 12%. Thus, it can be said that diamond-like carbon thin layer protect the solar cell against atomic oxygen exposure.

Impact of nanostructured thin ZnO film in ultraviolet protection

PubMed Central

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field. PMID:28096668

Impact of nanostructured thin ZnO film in ultraviolet protection.

PubMed

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field.

Thickness-dependent structure and properties of SnS2 thin films prepared by atomic layer deposition

NASA Astrophysics Data System (ADS)

Seo, Wondeok; Shin, Seokyoon; Ham, Giyul; Lee, Juhyun; Lee, Seungjin; Choi, Hyeongsu; Jeon, Hyeongtag

2017-03-01

Tin disulfide (SnS2) thin films were deposited by a thermal atomic layer deposition (ALD) method at low temperatures. The physical, chemical, and electrical characteristics of SnS2 were investigated as a function of the film thickness. SnS2 exhibited a (001) hexagonal plane peak at 14.9° in the X-ray diffraction (XRD) results and an A1g peak at 311 cm-1 in the Raman spectra. These results demonstrate that SnS2 thin films grown at 150 °C showed a crystalline phase at film thicknesses above 11.2 nm. The crystallinity of the SnS2 thin films was evaluated by a transmission electron microscope (TEM). The X-ray photoelectron spectroscopy (XPS) analysis revealed that SnS2 consisted of Sn4+ and S2- valence states. Both the optical band gap and the transmittance of SnS2 decreased as the film thickness increased. The band gap of SnS2 decreased from 3.0 to 2.4 eV and the transmittance decreased from 85 to 32% at a wavelength of 400 nm. In addition, the resistivity of the thin film SnS2 decreased from 1011 to 106 Ω·cm as the film thickness increased.

Exploring substrate/ionomer interaction under oxidizing and reducing environments

DOE PAGES

Tesfaye, Meron; MacDonald, Andrew N.; Dudenas, Peter J.; ...

2018-02-09

Local gas transport limitation attributed to the ionomer thin-film in the catalyst layer is a major deterrent to widespread commercialization of polymer-electrolyte fuel cells. So far functionality and limitations of these thin-films have been assumed identical in the anode and cathode. In this study, Nafion ionomer thin-films on platinum(Pt) support were exposed to H 2 and air as model schemes, mimicking anode and cathode catalyst layers. Findings indicate decreased swelling, increased densification of ionomer matrix, and increased humidity-induced aging rates in reducing environment, compared to oxidizing and inert environments. Observed phenomenon could be related to underlying Pt-gas interaction dictating Pt-ionomermore » behavior. Presented results could have significant implications about the disparate behavior of ionomer thin-film in anode and cathode catalyst layers.« less

Effect of angle of deposition on the Fractal properties of ZnO thin film surface

NASA Astrophysics Data System (ADS)

Yadav, R. P.; Agarwal, D. C.; Kumar, Manvendra; Rajput, Parasmani; Tomar, D. S.; Pandey, S. N.; Priya, P. K.; Mittal, A. K.

2017-09-01

Zinc oxide (ZnO) thin films were prepared by atom beam sputtering at various deposition angles in the range of 20-75°. The deposited thin films were examined by glancing angle X-ray diffraction and atomic force microscopy (AFM). Scaling law analysis was performed on AFM images to show that the thin film surfaces are self-affine. Fractal dimension of each of the 256 vertical sections along the fast scan direction of a discretized surface, obtained from the AFM height data, was estimated using the Higuchi's algorithm. Hurst exponent was computed from the fractal dimension. The grain sizes, as determined by applying self-correlation function on AFM micrographs, varied with the deposition angle in the same manner as the Hurst exponent.

Optical Probe of the Density of Defect States in Organic Thin-Film Transistors

NASA Astrophysics Data System (ADS)

Breban, Mihaela; Romero, Danilo; Ballarotto, Vincent; Williams, Ellen

2006-03-01

We investigate the role of defect states associated with different gate dielectric materials on charge transport in organic thin film transistors. Using a modulation technique we measure the magnitude and the phase of the photocurrent^1 in pentacene thin film transistors as a function of the modulation frequency. The photocurrent generation process is modeled as exciton dissociation due to interaction with localized traps. A time domain analyses of this multi-step process allows us to extract the density of defect states. We use this technique to compare the physical mechanism underlying performances of pentacene devices fabricated with different dielectric materials. *Supported by the Laboratory for Physical Science ^1 M. Breban, et al. ``Photocurrent probe of field-dependent mobility in organic thin-film transistors'' Appl. Phys. Letts. 87, 203503 (2005)

Microstructure and ferroelectricity of BaTiO3 thin films on Si for integrated photonics

NASA Astrophysics Data System (ADS)

Kormondy, Kristy J.; Popoff, Youri; Sousa, Marilyne; Eltes, Felix; Caimi, Daniele; Rossell, Marta D.; Fiebig, Manfred; Hoffmann, Patrik; Marchiori, Chiara; Reinke, Michael; Trassin, Morgan; Demkov, Alexander A.; Fompeyrine, Jean; Abe, Stefan

2017-02-01

Significant progress has been made in integrating novel materials into silicon photonic structures in order to extend the functionality of photonic circuits. One of these promising optical materials is BaTiO3 or barium titanate (BTO) that exhibits a very large Pockels coefficient as required for high-speed light modulators. However, all previous demonstrations show a noticable reduction of the Pockels effect in BTO thin films deposited on silicon substrates compared to BTO bulk crystals. Here, we report on the strong dependence of the Pockels effect in BTO thin films on their microstructure, and provide guidelines on how to engineer thin films with strong electro-optic response. We employ several deposition methods such as molecular beam epitaxy and chemical vapor deposition to realize BTO thin films with different morphology and crystalline structure. While a linear electro-optic response is present even in porous, polycrystalline BTO thin films with an effective Pockels coefficient r eff = 6 pm V-1, it is maximized for dense, tetragonal, epitaxial BTO films (r eff = 140 pm V-1). By identifying the key structural predictors of electro-optic response in BTO/Si, we provide a roadmap to fully exploit the linear electro-optic effect in novel hybrid oxide/semiconductor nanophotonic devices.

A Parametric Assessment of the Mission Applicability of Thin-film Solar Arrays

NASA Technical Reports Server (NTRS)

Hoffman, David J.

2002-01-01

Results are presented from a parametric assessment of the applicability and spacecraft-level impacts of very lightweight thin-film solar arrays with relatively large deployed areas for representative space missions. The most and least attractive features of thin-film solar arrays are briefly discussed. A calculation is then presented illustrating that from a solar array alone mass perspective, larger arrays with less efficient but lighter thin-film solar cells can weigh less than smaller arrays with more efficient but heavier crystalline cells. However, a spacecraft-level systems assessment must take into account the additional mass associated with solar array deployed area: the propellant needed to desaturate the momentum accumulated from area-related disturbance torques and to perform aerodynamic drag makeup reboost. The results for such an assessment are presented for a representative low Earth orbit (LEO) mission, as a function of altitude and mission life, and a geostationary Earth orbit (GEO) mission. Discussion of the results includes a list of specific mission types most likely to benefit from using thin-film arrays. The presentation concludes with a list of issues to be addressed prior to use of thin-film solar arrays in space and the observation that with their unique characteristics, very lightweight arrays using efficient, thin film cells on flexible substrates may become the best array option for a subset of Earth orbiting and deep space missions.

Advanced Fabrication Method for the Preparation of MOF Thin Films: Liquid-Phase Epitaxy Approach Meets Spin Coating Method.

PubMed

Chernikova, Valeriya; Shekhah, Osama; Eddaoudi, Mohamed

2016-08-10

Here, we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method was implemented to generate MOF thin films in a high-throughput fashion. Advantageously, this approach offers a great prospective to cost-effectively construct thin-films with a significantly shortened preparation time and a lessened chemicals and solvents consumption, as compared to the conventional LPE-process. Certainly, this new spin-coating approach has been implemented successfully to construct various MOF thin films, ranging in thickness from a few micrometers down to the nanometer scale, spanning 2-D and 3-D benchmark MOF materials including Cu2(bdc)2·xH2O, Zn2(bdc)2·xH2O, HKUST-1, and ZIF-8. This method was appraised and proved effective on a variety of substrates comprising functionalized gold, silicon, glass, porous stainless steel, and aluminum oxide. The facile, high-throughput and cost-effective nature of this approach, coupled with the successful thin film growth and substrate versatility, represents the next generation of methods for MOF thin film fabrication. Therefore, paving the way for these unique MOF materials to address a wide range of challenges in the areas of sensing devices and membrane technology.

Nanoscale modeling for ultrathin liquid films: Spreading and coupled layering

NASA Astrophysics Data System (ADS)

Phillips, David Michael

The hard disk drive (HDD) industry is currently experiencing a compound annual growth rate of 100% for the areal density. Current production drives have an areal density of 80 Gbit in-2, and drives with an areal density of 100 Gbit in-2 have been recently demonstrated. While much of this growth has been fueled by the development of new read/write heads, some of this gain was achieved by reducing the spacing between the heads and the magnetic media. This in turn reduces the spacing at the head-disk interface (HDI). The HDI in a HDD system consists of a slider, which contains the read/write heads, flying over the disk surface on an air bearing. The current designed separation distance, or fly height, is less than 10 nm. This spacing is expected to reduce to a mere 5 nm within the next few years. With the reduced fly height, intermittent contacts at the HDI become more probable. Only a thin lubricant film of perfluoropolyether (PFPE) and a sputtered carbon overcoat on the disk surface protect the slider and the stored data from mechanical and thermal damage. The PFPE film is quite thin, with a thickness of less than 2 nm or about a monolayer of molecules. During an HDI contact, the PFPE film is considered sacrificial and is often depleted in the contact area. In order to maintain adequate protection for the disk surface, PFPE molecules from the surrounding film must replenish the depleted area. This replenishment ability directly opposes the requirement that the PFPE film must not spin-off of the disk surface due to the disk rotation rate, which is as high as 10,000 RPM in current drives. To balance the PFPE films to sufficiently meet both requirements, HDD manufacturers functionalized the endgroups of the PFPE molecules to allow some portion of the lubricant film to reversibly bond with the disk overcoat. The result is a lubricant film that has a slower replenishment but does not spin-off. The work presented here focuses on the replenishment ability of thin films of liquid PFPE. The experimental analogue of replenishment is the one-dimensional spreading analysis. PFPEs with functional endgroups demonstrated coupled molecular layering and dewetting phenomena during the spreading analysis, while PFPEs with nonfunctional endgroups did not. All of the PFPE thin films spread via a diffusive process and had diffusion coefficients that depended on the local film thickness. A theoretical analysis is presented here for both the governing equation and the disjoining pressure driving force for the PFPE thin film spreading. For PFPEs with non-functional endgroups, a reasonable analysis is performed on the diffusion coefficient for two classes of film: submonolayer and multilayer. The diffusion coefficient of PFPEs with functional endgroups are qualitatively linked to the gradient of the film disjoining pressure. To augment this theory, both lattice-based and off-lattice Monte Carlo simulations are conducted for PFPE film models. The lattice-based model shows the existence of a critical functional endgroup interaction strength. It is also used to study the break-up of molecular layers for a spreading film via a fractal analysis. The off-lattice model is used to calculate the anisotropic pressure tensor for the model PFPE thin film and subsequently the film disjoining pressure. The model also qualitatively analyzes of the self diffusion in the film.

Thin polymeric films for building biohybrid microrobots.

PubMed

Ricotti, Leonardo; Fujie, Toshinori

2017-03-06

This paper aims to describe the disruptive potential that polymeric thin films have in the field of biohybrid devices and to review the recent efforts in this area. Thin (thickness  <  1 mm) and ultra-thin (thickness  <  1 µm) matrices possess a series of intriguing features, such as large surface area/volume ratio, high flexibility, chemical and physical surface tailorability, etc. This enables the fabrication of advanced bio/non-bio interfaces able to efficiently drive cell-material interactions, which are the key for optimizing biohybrid device performances. Thin films can thus represent suitable platforms on which living and artificial elements are coupled, with the aim of exploiting the unique features of living cells/tissues. This may allow to carry out certain tasks, not achievable with fully artificial technologies. In the paper, after a description of the desirable chemical/physical cues to be targeted and of the fabrication, functionalization and characterization procedures to be used for thin and ultra-thin films, the state-of-the-art of biohybrid microrobots based on micro/nano-membranes are described and discussed. The research efforts in this field are rather recent and they focus on: (1) self-beating cells (such as cardiomyocytes) able to induce a relatively large deformation of the underlying substrates, but affected by a limited controllability by external users; (2) skeletal muscle cells, more difficult to engineer in mature and functional contractile tissues, but featured by a higher controllability. In this context, the different materials used and the performances achieved are analyzed. Despite recent interesting advancements and signs of maturity of this research field, important scientific and technological steps are still needed. In the paper some possible future perspectives are described, mainly concerning thin film manipulation and assembly in multilayer 3D systems, new advanced materials to be used for the fabrication of thin films, cell engineering opportunities and modelling/computational efforts.

Strain Relaxation in Si{sub 1-x}Ge{sub x} Thin Films on Si(100) Substrates: Modeling and Comparisons with Experiments

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

Kolluri, K; Zepeda-Ruiz, L A; Murthy, C S

2005-03-22

Strained semiconductor thin films grown epitaxially on semiconductor substrates of different composition, such as Si{sub 1-x}Ge{sub x}/Si, are becoming increasingly important in modern microelectronic technologies. In this paper, we report a hierarchical computational approach for analysis of dislocation formation, glide motion, multiplication, and annihilation in Si{sub 1-x}Ge{sub x} epitaxial thin films on Si substrates. Specifically, a condition is developed for determining the critical film thickness with respect to misfit dislocation generation as a function of overall film composition, film compositional grading, and (compliant) substrate thickness. In addition, the kinetics of strain relaxation in the epitaxial film during growth or thermalmore » annealing (including post-implantation annealing) is analyzed using a properly parameterized dislocation mean-field theoretical model, which describes plastic deformation dynamics due to threading dislocation propagation. The theoretical results for Si{sub 1-x}Ge{sub x} epitaxial thin films grown on Si (100) substrates are compared with experimental measurements and are used to discuss film growth and thermal processing protocols toward optimizing the mechanical response of the epitaxial film.« less

Structure-function properties of anticorrosive exopolyaccharides

USDA-ARS?s Scientific Manuscript database

Nanoscale biobased exopolymer films were shown that provide protection to metal substrates under corrosive environments and that the films could be self-repairing in aqueous environments. This work describes the fundamental properties of thin exopolymer films including thermodynamic properties, film...

Improving uniformity and nanostructure of solution-processed thin films using ultrasonic substrate vibration post treatment (SVPT).

PubMed

Wang, Qin; Eslamian, Morteza

2016-04-01

The main goal of this paper is to introduce a novel mechanical method herein terms as substrate vibration post treatment (SVPT) technique, powered by ultrasonic vibration imposed on the substrate to enhance the characteristics and functionality of spun-on thin films or thin films made by similar casting techniques, such as drop and dip coating. In this technique, the as-casted wet films are placed on a substrate vibrated by an ultrasonic transducer with controlled power and duration to improve the film characteristics, such as uniformity and nanostructure. The performance of this technique is examined on spun-on PSS thin films used in polymer and perovskite solar cells and unprecedented results are presented. We first explore the influence of the vibration duration time on the characteristics of the films made by pristine PSS solution, where it is found that the optimized vibration duration for the pristine PSS film is about 10s, resulting in significant increase in the film electrical conductivity and lowered thickness and roughness. In order to further test the generality and merit of the method, thin films made using PSS solution modified with various types of surfactants and cured by the SVPT are studied. The results show that the application of the SVPT method combined with surfactant modification leads to an impressive twelve-fold increase in the conductivity of the PSS thin films compared with that of the pristine non-vibrated PSS thin films. The sole effect of the SVPT is a four-fold increase in the conductivity of pristine PSS film compared with that of the non-vibrated film. This remarkable enhancement in conductivity is further explained by the AFM phase images of PSS films, showing that the ultrasonic energy could loosen the Coulomb forces between PEDOT and PSS chains, resulting in phase separation and localized reordering of the conducting PEDOT chains leading to an increase in the electrical conductivity of the film. Highly conductive PSS thin film is a viable candidate as electrodes in emerging solution-processed solar cells. Copyright © 2015 Elsevier B.V. All rights reserved.

High-fraction brookite films from amorphous precursors.

PubMed

Haggerty, James E S; Schelhas, Laura T; Kitchaev, Daniil A; Mangum, John S; Garten, Lauren M; Sun, Wenhao; Stone, Kevin H; Perkins, John D; Toney, Michael F; Ceder, Gerbrand; Ginley, David S; Gorman, Brian P; Tate, Janet

2017-11-09

Structure-specific synthesis processes are of key importance to the growth of polymorphic functional compounds such as TiO 2 , where material properties strongly depend on structure as well as chemistry. The robust growth of the brookite polymorph of TiO 2 , a promising photocatalyst, has been difficult in both powder and thin-film forms due to the disparity of reported synthesis techniques, their highly specific nature, and lack of mechanistic understanding. In this work, we report the growth of high-fraction (~95%) brookite thin films prepared by annealing amorphous titania precursor films deposited by pulsed laser deposition. We characterize the crystallization process, eliminating the previously suggested roles of substrate templating and Na helper ions in driving brookite formation. Instead, we link phase selection directly to film thickness, offering a novel, generalizable route to brookite growth that does not rely on the presence of extraneous elements or particular lattice-matched substrates. In addition to providing a new synthesis route to brookite thin films, our results take a step towards resolving the problem of phase selection in TiO 2 growth, contributing to the further development of this promising functional material.

Sensing of contaminants in potable water using TiO{sub 2} functional film

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

Akshatha, N.; Poonia, Monika; Gupta, R. K., E-mail: raj@pilani.bits-pilani.ac.in

2016-04-13

The piezoelectric based quartz crystal microbalance is employed for sensing contaminants in potable water. A spin coated thin layer of TiO{sub 2} nanoparticles was formed at the sensing area of a 5 MHz AT-cut quartz wafer. The thin film of TiO{sub 2} nanoparticles forms a mesoporous functional layer for the trapping of water borne contaminants. The morphology of the thin film of TiO{sub 2} nanoparticles was studied using field emission scanning electron microscope (FESEM). The surface morphology of the TiO{sub 2} nanoparticles reveals the mesoporous structures indicating large number of defects and porous sites. Such film was employed for the detectionmore » of water borne contaminants by detecting the piezoelectric response from a quartz crystal microbalance. We found the film to be very sensitive to the contaminants. The minimum detection limit was found to be 330 ppb. The effect of surface recharging was also studied by altering the physical conditions so that the film can be used for repetitive usage.« less

Pathways to Mesoporous Resin/Carbon Thin Films with Alternating Gyroid Morphology

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

Zhang, Qi; Matsuoka, Fumiaki; Suh, Hyo Seon

Three-dimensional (3D) mesoporous thin films with sub-100 nm periodic lattices are of increasing interest as templates for a number of nanotechnology applications, yet are hard to achieve with conventional top-down fabrication methods. Block copolymer self-assembly derived mesoscale structures provide a toolbox for such 3D template formation. In this work, single (alternating) gyroidal and double gyroidal mesoporous thin-film structures are achieved via solvent vapor annealing assisted co-assembly of poly(isoprene-block-styrene-block-ethylene oxide) (PI-b-PS-b-PEO, ISO) and resorcinol/phenol formaldehyde resols. In particular, the alternating gyroid thin-film morphology is highly desirable for potential template backfilling processes as a result of the large pore volume fraction. Inmore » situ grazing-incidence small-angle X-ray scattering during solvent annealing is employed as a tool to elucidate and navigate the pathway complexity of the structure formation processes. The resulting network structures are resistant to high temperatures provided an inert atmosphere. The thin films have tunable hydrophilicity from pyrolysis at different temperatures, while pore sizes can be tailored by varying ISO molar mass. A transfer technique between substrates is demonstrated for alternating gyroidal mesoporous thin films, circumventing the need to re-optimize film formation protocols for different substrates. Increased conductivity after pyrolysis at high temperatures demonstrates that these gyroidal mesoporous resin/carbon thin films have potential as functional 3D templates for a number of nanomaterials applications.« less

Electro-Caloric Properties of BT/PZT Multilayer Thin Films Prepared by Sol-Gel Method.

PubMed

Kwon, Min-Su; Lee, Sung-Gap; Kim, Kyeong-Min

2018-09-01

In this study, Barium Titanate (BT)/Lead Zirconate Titanate (PZT) multilayer thin films were fabricated by the spin-coating method on Pt (200 nm)/Ti (10 nm) SiO2 (100 nm)/P-Si (100) substrates using BaTiO3 and Pb(Zr0.90Ti0.10)O3 metal alkoxide solutions. The coating and heating procedure was repeated several times to form the multilayer thin films. All of BT/PZT multilayer thin films show X-ray diffraction patterns typical to a polycrystalline perovskite structure and a uniform and void free grain microstructure. The thickness of the BT and PZT film by one-cycle of drying/sintering was approximately 50 nm and all of the films consisted of fine grains with a flat surface morphology. The electrocaloric properties of BT/PZT thin films were investigated by indirect estimation. The results showed that the temperature change ΔT can be calculated as a function of temperature using Maxwell's relation; the temperature change reaches a maximum value of ~1.85 °C at 135 °C under an applied electric field of 260 kV/cm.

Thin-Film Solar Array Earth Orbit Mission Applicability Assessment

NASA Technical Reports Server (NTRS)

Hoffman, David J.; Kerslake, Thomas W.; Hepp, Aloysius F.; Raffaelle, Ryne P.

2002-01-01

This is a preliminary assessment of the applicability and spacecraft-level impact of using very lightweight thin-film solar arrays with relatively large deployed areas for representative Earth orbiting missions. The most and least attractive features of thin-film solar arrays are briefly discussed. A simple calculation is then presented illustrating that from a solar array alone mass perspective, larger arrays with less efficient but lighter thin-film solar cells can weigh less than smaller arrays with more efficient but heavier crystalline cells. However, a proper spacecraft-level systems assessment must take into account the additional mass associated with solar array deployed area: the propellant needed to desaturate the momentum accumulated from area-related disturbance torques and to perform aerodynamic drag makeup reboost. The results for such an assessment are presented for a representative low Earth orbit (LEO) mission, as a function of altitude and mission life, and a geostationary Earth orbit (GEO) mission. Discussion of the results includes a list of specific mission types most likely to benefit from using thin-film arrays. NASA Glenn's low-temperature approach to depositing thin-film cells on lightweight, flexible plastic substrates is also briefly discussed to provide a perspective on one approach to achieving this enabling technology. The paper concludes with a list of issues to be addressed prior to use of thin-film solar arrays in space and the observation that with their unique characteristics, very lightweight arrays using efficient, thin-film cells on flexible substrates may become the best array option for a subset of Earth orbiting missions.

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.

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

Hsu, Chih-Hao; Yue, Kan; Wang, Jing

Controlling self-assembled nanostructures in thin films allows the bottom-up fabrication of ordered nanoscale patterns. Here we report the unique thickness-dependent phase behavior in thin films of a bolaform-like giant surfactant, which consists of butyl- and hydroxyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS and DPOSS) cages telechelically located at the chain ends of a polystyrene (PS) chain with 28 repeating monomers on average. In the bulk, BPOSS-PS28-DPOSS forms a double gyroid (DG) phase. Both grazing incidence small angle X-ray scattering and transmission electron microscopy techniques are combined to elucidate the thin film structures. Interestingly, films with thicknesses thinner than 200 nm exhibit anmore » irreversible phase transition from hexagonal perforated layer (HPL) to compressed hexagonally packed cylinders (c-HEX) at 130 °C, while films with thickness larger than 200 nm show an irreversible transition from HPL to DG at 200 °C. The thickness-controlled transition pathway suggests possibilities to obtain diverse patterns via thin film self-assembly.« less

Work function and quantum efficiency study of metal oxide thin films on Ag(100)

NASA Astrophysics Data System (ADS)

Chang, V.; Noakes, T. C. Q.; Harrison, N. M.

2018-04-01

Increasing the quantum efficiency (QE) of metal photocathodes is in the design and development of photocathodes for free-electron laser applications. The growth of metal oxide thin films on certain metal surfaces has previously been shown to reduce the work function (WF). Using a photoemission model B. Camino et al. [Comput. Mater. Sci. 122, 331 (2016), 10.1016/j.commatsci.2016.05.025] based on the three-step model combined with density functional theory calculations we predict that the growth of a finite number of MgO(100) or BaO(100) layers on the Ag(100) surface increases significantly the QE compared with the clean Ag(100) surface for a photon energy of 4.7 eV. Different mechanisms for affecting the QE are identified for the different metal oxide thin films. The addition of MgO(100) increases the QE due to the reduction of the WF and the direct excitation of electrons from the Ag surface to the MgO conduction band. For BaO(100) thin films, an additional mechanism is in operation as the oxide film also photoemits at this energy. We also note that a significant increase in the QE for photons with an energy of a few eV above the WF is achieved due to an increase in the inelastic mean-free path of the electrons.

Thermal annealing induced structural and optical properties of Se{sub 72}Te{sub 25}In{sub 3} thin films

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

Pathak, H. P.; Dwivedi, D. K., E-mail: todkdwivedi@gmail.com; Shukla, Nitesh

2016-05-06

Thin films of a- Se{sub 72}Te{sub 25}In{sub 3} were prepared by vacuum evaporation technique in a base pressure of 10{sup -6} Torr on to well cleaned glass substrate. a-Se{sub 72}Te{sub 25}In{sub 3} thin films were annealed at different temperatures below their crystallization temperatures for 2h. The structural analysis of the films has been investigated using X-ray diffraction technique. The optical absorption spectra of these films were measured in the wavelength range 400-1100 nm in order to derive the absorption coefficient of these films. The optical band gap of as prepared and annealed films as a function of photon energy hasmore » been studied. It has been found that the optical band gap decreases with increasing annealing temperatures in the present system.« less

Domain structure of BiFeO3 thin films grown on patterned SrTiO3(001) substrates

NASA Astrophysics Data System (ADS)

Nakashima, Seiji; Seto, Shota; Kurokawa, Yuta; Fujisawa, Hironori; Shimizu, Masaru

2017-10-01

Recently, new functionalities of ferroelectric domain walls (DWs) have attracted much attention. To realize novel devices using the functionalities of the DWs, techniques to introduce the DWs at arbitrary positions in the ferroelectric thin films are necessary. In this study, we have demonstrated the introduction of the DWs at arbitrary positions in epitaxial BiFeO3 (BFO) thin films using the patterned surface of the SrTiO3 (STO) single-crystal substrate. On the slope pattern of the STO surface, the in-plane orientation of BFO has changed because the in-plane orientation of BFO can be controlled by the step propagation direction of the patterned surface. From the piezoresponse scanning force microscopy and X-ray diffraction reciprocal space mapping results, charged 109° DWs have been introduced into the BFO thin film at the bottom and top of the slope pattern of the STO surface. In addition, the conductivity modulation of the positively charged DW has been observed by current-sensitive atomic force microscopy imaging.

Characterization of fully functional spray-on antibody thin films

NASA Astrophysics Data System (ADS)

Figueroa, Jhon; Magaña, Sonia; Lim, Daniel V.; Schlaf, Rudy

2014-02-01

The authors recently demonstrated that fully functional Escherichia coli O157:H7 antibody thin films can be prepared using a simple pneumatic nebulizer on glass surface [1]. This paper focuses on the investigation of the morphology and physical properties of these films with the aim to better understand their performance. A series of E. coli O157:H7 antibody spray-on thin films were investigated by ellipsometry, X-ray photoelectron spectroscopy (XPS), immunoassays, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), fluorescence microscopy, atomic force microscope (AFM) and contact angle analysis. These data were compared to measurements on films prepared with the biotin-avidin covalent bonding scheme. The investigation showed that films created by a 2 min pneumatic spray deposition time can capture antigens similar as the avidin-biotin wet-chemical method. The results also suggests that an influential factor for the comparable capture cell ability between sprayed and covalent films is an increased antibody surface coverage for the sprayed films (non-equilibrium technique), which compensates for the lack of its antibody orientation. There was no significant antibody denaturation detected on any of the sprayed films. Both techniques led to the formation of cluster-aggregates, a factor that seems unavoidable due to the natural tendency of protein to cluster. The avidin-biotin bridge films generally had a higher roughness, which manifested itself in a higher wettability compared to the sprayed films.

Conduction properties of thin films from a water soluble carbon nanotube/hemicellulose complex

NASA Astrophysics Data System (ADS)

Shao, Dongkai; Yotprayoonsak, Peerapong; Saunajoki, Ville; Ahlskog, Markus; Virtanen, Jorma; Kangas, Veijo; Volodin, Alexander; Van Haesendonck, Chris; Burdanova, Maria; Mosley, Connor D. W.; Lloyd-Hughes, James

2018-04-01

We have examined the conductive properties of carbon nanotube based thin films, which were prepared via dispersion in water by non-covalent functionalization of the nanotubes with xylan, a type of hemicellulose. Measurements of low temperature conductivity, Kelvin probe force microscopy, and high frequency (THz) conductivity elucidated the intra-tube and inter-tube charge transport processes in this material. The measurements show excellent conductive properties of the as prepared thin films, with bulk conductivity up to 2000 S cm-1. The transport results demonstrate that the hemicellulose does not seriously interfere with the inter-tube conductance.

Contact-metal dependent current injection in pentacene thin-film transistors

NASA Astrophysics Data System (ADS)

Wang, S. D.; Minari, T.; Miyadera, T.; Tsukagoshi, K.; Aoyagi, Y.

2007-11-01

Contact-metal dependent current injection in top-contact pentacene thin-film transistors is analyzed, and the local mobility in the contact region was found to follow the Meyer-Neldel rule. An exponential trap distribution, rather than the metal/organic hole injection barrier, is proposed to be the dominant factor of the contact resistance in pentacene thin-film transistors. The variable temperature measurements revealed a much narrower trap distribution in the copper contact compared with the corresponding gold contact, and this is the origin of the smaller contact resistance for copper despite a lower work function.

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.

Effect of Pentacene-dielectric Affinity on Pentacene Thin Film Growth Morphology in Organic Field-effect Transistors

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

S Kim; M Jang; H Yang

2011-12-31

Organic field-effect transistors (OFETs) are fabricated by depositing a thin film of semiconductor on the functionalized surface of a SiO{sub 2} dielectric. The chemical and morphological structures of the interface between the semiconductor and the functionalized dielectric are critical for OFET performance. We have characterized the effect of the affinity between semiconductor and functionalized dielectric on the properties of the semiconductor-dielectric interface. The crystalline microstructure/nanostructure of the pentacene semiconductor layers, grown on a dielectric substrate that had been functionalized with either poly(4-vinyl pyridine) or polystyrene (to control hydrophobicity), and grown under a series of substrate temperatures and deposition rates, weremore » characterized by X-ray diffraction, photoemission spectroscopy, and atomic force microscopy. By comparing the morphological features of the semiconductor thin films with the device characteristics (field-effect mobility, threshold voltage, and hysteresis) of the OFET devices, the effect of affinity-driven properties on charge modulation, charge trapping, and charge carrier transport could be described.« less

Enhanced mechanical properties of low-surface energy thin films by simultaneous plasma polymerization of fluorine and epoxy containing polymers

NASA Astrophysics Data System (ADS)

Karaman, Mustafa; Uçar, Tuba

2016-01-01

Thin films of poly(2,2,3,4,4,4 hexafluorobutyl acrylate-glycidyl methacrylate) (P(HFBA-GMA) were deposited on different surfaces using an inductively coupled RF plasma reactor. Fluorinated polymer was used to impart hydrophobicity, whereas epoxy polymer was used for improved durability. The deposition at a low plasma power and temperature was suitable for the functionalization of fragile surfaces such as textile fabrics. The coated rough textile surfaces were found to be superhydrophobic with water contact angles greater than 150° due to the high retention of long fluorinated side chains. The hydrophobicity of the surfaces was observed to be stable after many exposures to ultrasonification tests, which is attributed to the mechanical durability of the films due to their epoxide functionality. FTIR and XPS analyses of the deposited films confirmed that the epoxide functionality of the polymers increased with increasing glycidyl methacrylate fraction in the reactor inlet. The modulus and hardness values of the films also increase with increasing epoxide functionality.

Thickness Dependence of Failure in Ultra-thin Glassy Polymer Films

NASA Astrophysics Data System (ADS)

Bay, Reed; Shimomura, Shinichiro; Liu, Yujie; Ilton, Mark; Crosby, Alfred

The physical properties of polymer thin films change as the polymer chains become confined. Similar changes in mechanical properties have been observed, though these critical properties have only been explored a limited extent and with indirect methods. Here, we use a recently developed method to measure the complete uniaxial stress strain relationship of polymer thin films of polystyrene films (PS, Mw =130kg/mol, 490kg/mol, and 853kg/mol) as a function of thickness (20 nm-220nm). In this method, we hold a `dog-bone' shaped film on water between a flexible cantilever and a movable rigid boundary, measuring force-displacement from the cantilever deflection. From our measurements, we find that the modulus decreases as the PS chains become confined. The PS thin films exhibit ``ideal perfectly plastic'' behavior due to crazing, which differs from the typical brittle response of bulk PS. The draw stress due to crazing decreases with film thickness. These results provide new fundamental insight into how polymer behavior is altered due to structural changes in the entangled polymer network upon confinement. NSF DMR 1608614.

Effect of thermal annealing on structure and optical band gap of amorphous Se{sub 72}Te{sub 25}Sb{sub 3} thin films

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

Dwivedi, D. K., E-mail: dwivedidkphys@rediffmail.com; Pathak, H. P., E-mail: dwivedidkphys@rediffmail.com; Shukla, Nitesh

2014-04-24

Thin films of a−Se{sub 72}Te{sub 25}Sb{sub 3} were prepared by vacuum evaporation technique in a base pressure of 10{sup −6} Torr on to well cleaned glass substrate. a−Se{sub 72}Te{sub 25}Sb{sub 3} thin films were annealed at different temperatures below their crystallization temperatures for 2h. The structural analysis of the films has been investigated using X-ray diffraction technique. The optical band gap of as prepared and annealed films as a function of photon energy in the wavelength range 400–1100 nm has been studied. It has been found that the optical band gap decreases with increasing annealing temperatures in the present system.

Ferroelectric thin-film capacitors and piezoelectric switches for mobile communication applications.

PubMed

Klee, Mareike; van Esch, Harry; Keur, Wilco; Kumar, Biju; van Leuken-Peters, Linda; Liu, Jin; Mauczok, Rüdiger; Neumann, Kai; Reimann, Klaus; Renders, Christel; Roest, Aarnoud L; Tiggelman, Mark P J; de Wild, Marco; Wunnicke, Olaf; Zhao, Jing

2009-08-01

Thin-film ferroelectric capacitors have been integrated with resistors and active functions such as ESD protection into small, miniaturized modules, which enable a board space saving of up to 80%. With the optimum materials and processes, integrated capacitors with capacitance densities of up to 100 nF/mm2 for stacked capacitors combined with breakdown voltages of 90 V have been achieved. The integration of these high-density capacitors with extremely high breakdown voltage is a major accomplishment in the world of passive components and has not yet been reported for any other passive integration technology. Furthermore, thin-film tunable capacitors based on barium strontium titanate with high tuning range and high quality factor at 1 GHz have been demonstrated. Finally, piezoelectric thin films for piezoelectric switches with high switching speed have been realized.

An investigation of passivity and breakdown of amorphous chromium-bromine thin films for surface modification of metallic biomaterials

NASA Astrophysics Data System (ADS)

Cormier, Lyne Mercedes

1998-12-01

The objectives of this investigation of amorphous Cr-B thin films as prospective coatings for biomaterials applications were to (i) produce and characterize an amorphous Cr-B thin film coating by magnetron sputtering, (ii) evaluate its corrosion resistance in physiologically relevant electrolytes, and (iii) propose a mechanism for the formation/dissolution of the passive film formed on amorphous Cr-B in chloride-containing near-neutral salt electrolytes. Dense (zone T) amorphous Cr75B25 thin films produced by DC magnetron sputtering were found to be better corrosion barriers than nanoczystalline or porous (zone 1) amorphous Cr75B25 thin films. The growth morphology and microstructure were a function of the sputtering pressure and substrate temperature, in agreement with the structure zone model of Thornton. The passivity/loss of passivity of amorphous Cr 75B25 in near-neutral salt solutions was explained using a modified bipolar layer model. The chromate ions identified by X-Ray Photoelectron Spectroscopy (XPS) in the outer layer of the passive film were found to play a determinant role in the passive behaviour of amorphous Cr75B 25 thin films in salt solutions. In near-neutral salt solutions of pH = 5 to 7, a decrease in pH combined with an increase in chloride concentration resulted in less dissolution of the Cr75B25 thin films. The apparent breakdown potential at 240 mV (SCE) obtained by Cyclic Potentiodynamic Anodic Polarization (CPAP) was associated with oxidation of species within the passive film, but not to dissolution leading to immediate loss of passivity. Pit Propagation Rate (PPR) testing evaluated the stable pitting potential to be between 600 and 650 mV. Amorphous Cr75B25 thin films ranked the best among other Cr-based materials such as 316L stainless steel, CrB2 and Cr investigated in this study for general corrosion behaviour in NaCl and Hanks solutions by CPAP testing. In terms of corrosion resistance, amorphous Cr75B25 thin films were recognized as a promising material for surface modification of biomaterials.

Optical properties of epitaxial BiFeO3 thin film grown on SrRuO3-buffered SrTiO3 substrate.

PubMed

Xu, Ji-Ping; Zhang, Rong-Jun; Chen, Zhi-Hui; Wang, Zi-Yi; Zhang, Fan; Yu, Xiang; Jiang, An-Quan; Zheng, Yu-Xiang; Wang, Song-You; Chen, Liang-Yao

2014-01-01

The BiFeO3 (BFO) thin film was deposited by pulsed-laser deposition on SrRuO3 (SRO)-buffered (111) SrTiO3 (STO) substrate. X-ray diffraction pattern reveals a well-grown epitaxial BFO thin film. Atomic force microscopy study indicates that the BFO film is rather dense with a smooth surface. The ellipsometric spectra of the STO substrate, the SRO buffer layer, and the BFO thin film were measured, respectively, in the photon energy range 1.55 to 5.40 eV. Following the dielectric functions of STO and SRO, the ones of BFO described by the Lorentz model are received by fitting the spectra data to a five-medium optical model consisting of a semi-infinite STO substrate/SRO layer/BFO film/surface roughness/air ambient structure. The thickness and the optical constants of the BFO film are obtained. Then a direct bandgap is calculated at 2.68 eV, which is believed to be influenced by near-bandgap transitions. Compared to BFO films on other substrates, the dependence of the bandgap for the BFO thin film on in-plane compressive strain from epitaxial structure is received. Moreover, the bandgap and the transition revealed by the Lorentz model also provide a ground for the assessment of the bandgap for BFO single crystals.

Magnetic hysteresis measurements of thin films under isotropic stress.

NASA Astrophysics Data System (ADS)

Holland, Patrick; Dubey, Archana; Geerts, Wilhelmus

2000-10-01

Nowadays, ferromagnetic thin films are widely applied in devices for information technology (credit cards, video recorder tapes, floppies, hard disks) and sensors (air bags, anti-breaking systems, navigation systems). Thus, with the increase in the use of magnetic media continued investigation of magnetic properties of materials is necessary to help in determining the useful properties of materials for new or improved applications. We are currently interested in studying the effect of applied external stress on Kerr hysteresis curves of thin magnetic films. The Ni and NiFe films were grown using DC magnetron sputtering with Ar as the sputter gas (pAr=4 mTorr; Tsub=55-190 C). Seed and cap layers of Ti were used on all films for adhesion and oxidation protection, respectively. A brass membrane pressure cell was designed to apply in-plane isotropic stress to thin films. In this pressure cell, gas pressure is used to deform a flexible substrate onto which a thin magnetic film has been sputtered. The curvature of the samples could be controlled by changing the gas pressure to the cell. Magneto-Optical in-plane hysteresis curves at different values of strain were measured. The results obtained show that the stress sensitivity is dependent on the film thickness. For the 500nm NiFe films, the coercivity strongly decreased as a function of the applied stress.

Lanthanum aluminum oxide thin-film dielectrics from aqueous solution.

PubMed

Plassmeyer, Paul N; Archila, Kevin; Wager, John F; Page, Catherine J

2015-01-28

Amorphous LaAlO3 dielectric thin films were fabricated via solution processing from inorganic nitrate precursors. Precursor solutions contained soluble oligomeric metal-hydroxyl and/or -oxo species as evidenced by dynamic light scattering (DLS) and Raman spectroscopy. Thin-film formation was characterized as a function of annealing temperature using Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and an array of electrical measurements. Annealing temperatures ≥500 °C result in thin films with low leakage-current densities (∼1 × 10(-8) A·cm(-2)) and dielectric constants ranging from 11.0 to 11.5. When incorporated as the gate dielectric layer in a-IGZO thin-film transistors (TFTs), LaAlO3 thin films annealed at 600 °C in air yielded TFTs with relatively low average mobilities (∼4.5 cm(2)·V(-1)·s(-1)) and high turn-on voltages (∼26 V). Interestingly, reannealing the LaAlO3 in 5%H2/95%N2 at 300 °C before deposition of a-IGZO channel layers resulted in TFTs with increased average mobilities (11.1 cm(2)·V(-1)·s(-1)) and lower turn-on voltages (∼6 V).

Thin film metallic sensors in an alternating magnetic field for magnetic nanoparticle hyperthermia cancer therapy

NASA Astrophysics Data System (ADS)

Hussein, Z. A.; Boekelheide, Z.

In magnetic nanoparticle hyperthermia in an alternating magnetic field for cancer therapy, it is important to monitor the temperature in situ. This can be done optically or electrically, but electronic measurements can be problematic because conducting parts heat up in a changing magnetic field. Microfabricated thin film sensors may be advantageous because eddy current heating is a function of size, and are promising for further miniaturization of sensors and fabrication of arrays of sensors. Thin films could also be used for in situ magnetic field sensors or for strain sensors. For a proof of concept, we fabricated a metallic thin film resistive thermometer by photolithographically patterning a 500Å Au/100Å Cr thin film on a glass substrate. Measurements were taken in a solenoidal coil supplying 0.04 T (rms) at 235 kHz with the sensor parallel and perpendicular to the magnetic field. In the parallel orientation, the resistive thermometer mirrored the background heating from the coil, while in the perpendicular orientation self-heating was observed due to eddy current heating of the conducting elements by Faraday's law. This suggests that metallic thin film sensors can be used in an alternating magnetic field, parallel to the field, with no significant self-heating.

Study of metal/ZnO based thin film ultraviolet photodetectors: The effect of induced charges on the dynamics of photoconductivity relaxation

NASA Astrophysics Data System (ADS)

Yadav, Harish Kumar; Sreenivas, K.; Gupta, Vinay

2010-02-01

Ultraviolet photoconductivity relaxation in ZnO thin films deposited by rf magnetron sputtering are investigated. Effect of oxygen partial pressure in the reactive gas mixture and film thickness on the photoconductivity transients is studied. A different photodetector configuration comprising ZnO thin film with an ultrathin overlayer of metals like Cu, Al, Sn, Au, Cr, and Te was designed and tested. Photoresponse signal were found to be stronger (four to seven times) in these configurations than the pure ZnO thin films. Sn(30 nm)/ZnO sample exhibits highest responsivity of ˜8.57 kV/W whereas Te(20 nm)/ZnO structure presents highest sensitivity of ˜31.3×103 compared to unloaded ZnO thin film. Enhancement in the photoresponse of ZnO thin films is attributed to the change in surface conductivity due to induced charge carriers at the interface because of the difference in work function and oxygen affinity values of metal overlayer with the underlying semiconducting layer. Charge carrier transfer from the metal layer to ZnO creates a surplus of electrons at the interface; a fraction of which are captured by the defect centers (traps) at the surface whereas the remaining one represents free carriers in the conduction band and are responsible for the enhanced photoconductivity.

Transparent, flexible supercapacitors from nano-engineered carbon films.

PubMed

Jung, Hyun Young; Karimi, Majid B; Hahm, Myung Gwan; Ajayan, Pulickel M; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Transparent, flexible supercapacitors from nano-engineered carbon films

PubMed Central

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-01-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications. PMID:23105970

Transparent, flexible supercapacitors from nano-engineered carbon films

NASA Astrophysics Data System (ADS)

Jung, Hyun Young; Karimi, Majid B.; Hahm, Myung Gwan; Ajayan, Pulickel M.; Jung, Yung Joon

2012-10-01

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Thin Films of Novel Linear-Dendritic Diblock Copolymers

NASA Astrophysics Data System (ADS)

Iyer, Jyotsna; Hammond, Paula

1998-03-01

A series of diblock copolymers with one linear block and one dendrimeric block have been synthesized with the objective of forming ultrathin film nanoporous membranes. Polyethyleneoxide serves as the linear hydrophilic portion of the diblock copolymer. The hyperbranched dendrimeric block consists of polyamidoamine with functional end groups. Thin films of these materials made by spin casting and the Langmuir-Blodgett techniques are being studied. The effect of the polyethylene oxide block size and the number and chemical nature of the dendrimer end group on the nature and stability of the films formed willbe discussed.

A molecular scale perspective: Monte Carlo simulation for rupturing of ultra thin polymer film melts

NASA Astrophysics Data System (ADS)

Singh, Satya Pal

2017-04-01

Monte Carlo simulation has been performed to study the rupturing process of thin polymer film under strong confinement. The change in mean square displacement; pair correlation function; density distribution; average bond length and microscopic viscosity are sampled by varying the molecular interaction parameters such as the strength and the equilibrium positions of the bonding, non-bonding potentials and the sizes of the beads. The variation in mean square angular displacement χθ = [ < Δθ2 > - < Δθ>2 ] fits very well to a function of type y (t) = A + B *e-t/τ. This may help to study the viscous properties of the films and its dependence on different parameters. The ultra thin film annealed at high temperature gets ruptured and holes are created in the film mimicking spinodal dewetting. The pair correlation function and density profile reveal rich information about the equilibrium structure of the film. The strength and equilibrium bond length of finite extensible non-linear elastic potential (FENE) and non-bonding Morse potential have clear impact on microscopic rupturing of the film. The beads show Rouse or repetition motion forming rim like structures near the holes created inside the film. The higher order interaction as dipole-quadrupole may get prominence under strong confinement. The enhanced excluded volume interaction under strong confinement may overlap with the molecular dispersion forces. It can work to reorganize the molecules at the bottom of the scale and can imprint its signature in complex patterns evolved.

Novel antifouling nano-enhanced thin-film composite membrane containing cross-linkable acrylate-alumoxane nanoparticles for water softening.

PubMed

Ghaemi, Negin

2017-01-01

A novel thin-film composite (TFC) nanofiltration membrane was prepared using polymerization of pyrrole monomers on the PES ultrafiltration membrane. To improve the characteristics of hydrophobic polypyrrole (PPy) thin-film layer, cross-linkable acrylate-functionalized alumoxane nanoparticles with different concentrations were embedded into the thin-film during polymerization process, and thin-film nanocomposite (TFNC) membranes were prepared. The characteristics and performance of TFC and TFNC membranes were assessed through the morphological analyses (SEM, AFM), measurement of hydrophilicity and solid-liquid interfacial free energy, water permeability and Mg 2+ removal tests. Addition of proper amount of nanoparticles into the polymerization mixture led to the preparation of membranes with more hydrophilic, thinner and smoother active layer as well as higher water permeability compared to TFC control membrane. TFNC membrane prepared with 0.025g of nanoparticles was the most efficient membrane since it exhibited the highest rejection of MgCl 2 and MgSO 4 salts. Antifouling capability of membranes, in terms of flux recovery and fouling parameters, demonstrated the high tolerance of TFNC against fouling. Copyright © 2016 Elsevier Inc. All rights reserved.

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

Jin, Wencan; Vishwanath, Suresh; Liu, Jianpeng

Topological crystalline insulators have been recently predicted and observed in rock-salt structure SnSe {111} thin films. Previous studies have suggested that the Se-terminated surface of this thin film with hydrogen passivation has a reduced surface energy and is thus a preferred configuration. In this paper, synchrotron-based angle-resolved photoemission spectroscopy, along with density functional theory calculations, is used to demonstrate that a rock-salt SnSe {111} thin film epitaxially grown on Bi 2Se 3 has a stable Sn-terminated surface. These observations are supported by low-energy electron diffraction (LEED) intensity-voltage measurements and dynamical LEED calculations, which further show that the Sn-terminated SnSe {111}more » thin film has undergone a surface structural relaxation of the interlayer spacing between the Sn and Se atomic planes. In sharp contrast to the Se-terminated counterpart, the observed Dirac surface state in the Sn-terminated SnSe {111} thin film is shown to yield a high Fermi velocity, 0.50 x 10 6 m/s, which suggests a potential mechanism of engineering the Dirac surface state of topological materials by tuning the surface configuration.« less

Qualitative and quantitative differentiation of gases using ZnO thin film gas sensors and pattern recognition analysis.

PubMed

Pati, Sumati; Maity, A; Banerji, P; Majumder, S B

2014-04-07

In the present work we have grown highly textured, ultra-thin, nano-crystalline zinc oxide thin films using a metal organic chemical vapor deposition technique and addressed their selectivity towards hydrogen, carbon dioxide and methane gas sensing. Structural and microstructural characteristics of the synthesized films were investigated utilizing X-ray diffraction and electron microscopy techniques respectively. Using a dynamic flow gas sensing measurement set up, the sensing characteristics of these films were investigated as a function of gas concentration (10-1660 ppm) and operating temperature (250-380 °C). ZnO thin film sensing elements were found to be sensitive to all of these gases. Thus at a sensor operating temperature of ~300 °C, the response% of the ZnO thin films were ~68, 59, and 52% for hydrogen, carbon monoxide and methane gases respectively. The data matrices extracted from first Fourier transform analyses (FFT) of the conductance transients were used as input parameters in a linear unsupervised principal component analysis (PCA) pattern recognition technique. We have demonstrated that FFT combined with PCA is an excellent tool for the differentiation of these reducing gases.

Patterning layer-by-layer self-assembled multilayer by lithography and its applications to thin film devices

NASA Astrophysics Data System (ADS)

Hua, Feng

Nanoparticles are exciting materials because they exhibit unique electronic, catalytic, and optical properties. As a novel and promising nanobuilding block, it attracts considerable research efforts in its integration into a wide variety of thin film devices. Nanoparticles were adsorbed onto the substrate with layer-by-layer self-assembly which becomes of great interest due to its suitability in colloid particle assembly. Without extremely high temperatures and sophisticated equipment, molecularly organized films in an exactly pre-designed order can grow on almost all the substrates in nature. Two approaches generating spatially separated patterns comprised of nanoparticles are demonstrated, as well as two approaches patterning more than one type of nonoparticle on a silicon wafer. The structure of the thin film patterned by these approaches are analyzed and considered suitable to the thin film device. Finally, the combination of lithography and layer-by-layer (lbl) self-assembly is utilized to realize the microelectronic device with functional nonoparticles. The lbl self-assembly is the way to coat the nonoparticles and the lighography to pattern them. Based on the coating and patterning technique, a MOS-capacitor, a MOS field-effect-transistor and magnetic thin film cantilever are fabricated.

Effect of Target Composition and Sputtering Deposition Parameters on the Functional Properties of Nitrogenized Ag-Permalloy Flexible Thin Films Deposited on Polymer Substrates

PubMed Central

Wang, Qun; Jin, Xin

2018-01-01

We report the first results of functional properties of nitrogenized silver-permalloy thin films deposited on polyethylene terephthalic ester {PETE (C10H8O4)n} flexible substrates by magnetron sputtering. These new soft magnetic thin films have magnetization that is comparable to pure Ni81Fe19 permalloy films. Two target compositions (Ni76Fe19Ag5 and Ni72Fe18Ag10) were used to study the effect of compositional variation and sputtering parameters, including nitrogen flow rate on the phase evolution and surface properties. Aggregate flow rate and total pressure of Ar+N2 mixture was 60 sccm and 0.55 Pa, respectively. The distance between target and the substrate was kept at 100 mm, while using sputtering power from 100–130 W. Average film deposition rate was confirmed at around 2.05 nm/min for argon atmosphere and was reduced to 1.8 nm/min in reactive nitrogen atmosphere. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, vibrating sample magnetometer, and contact angle measurements were used to characterize the functional properties. Nano sized character of films was confirmed by XRD and SEM. It is found that the grain size was reduced by the formation of nitride phase, which in turns enhanced the magnetization and lowers the coercivity. Magnetic field coupling efficiency limit was determined from 1.6–2 GHz frequency limit. The results of comparable magnetic performance, lowest magnetic loss, and highest surface free energy, confirming that 15 sccm nitrogen flow rate at 115 W is optimal for producing Ag-doped permalloy flexible thin films having excellent magnetic field coupling efficiency. PMID:29562603

AFM investigation and optical band gap study of chemically deposited PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mansoor, M.; Abubakar; Asim, M. M.

2016-08-01

The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

Semiconducting boron carbide thin films: Structure, processing, and diode applications

NASA Astrophysics Data System (ADS)

Bao, Ruqiang

The high energy density and long lifetime of betavoltaic devices make them very useful to provide the power for applications ranging from implantable cardiac pacemakers to deep space satellites and remote sensors. However, when made with conventional semiconductors, betavoltaic devices tend to suffer rapid degradation as a result of radiation damage. It has been suggested that the degradation problem could potentially be alleviated by replacing conventional semiconductors with a radiation hard semiconducting material like icosahedral boron carbide. The goal of my dissertation was to better understand the fundamental properties and structure of boron carbide thin films and to explore the processes to fabricate boron carbide based devices for voltaic applications. A pulsed laser deposition system and a radio frequency (RF) magnetron sputtering deposition system were designed and built to achieve the goals. After comparing the experimental results obtained using these two techniques, it was concluded that RF magnetron sputtering deposition technique is a good method to make B4C boron carbide thin films to fabricate repeatable and reproducible voltaic devices. The B4C thin films deposited by RF magnetron sputtering require in situ dry pre-cleaning to make ohmic contacts for B4C thin films to fabricate the devices. By adding another RF sputtering to pre-clean the substrate and thin films, a process to fabricate B4C / n-Si heterojunctions has been established. In addition, a low energy electron accelerator (LEEA) was built to mimic beta particles emitted from Pm147 and used to characterize the betavoltaic performance of betavoltaic devices as a function of beta energy and beta flux as well as do accelerated lifetime testing for betavoltaic devices. The energy range of LEEA is 20 - 250 keV with the current from several nA to 50 muA. High efficiency Si solar cells were used to demonstrate the powerful capabilities of LEEA, i.e., the characterization of betavoltaic performance and the accelerated lifetime test of betavoltaic devices. Structural analysis by X-ray diffraction and high resolution transmission electron microscopy showed that the prepared B4C thin films are amorphous. The presence of icosahedrons, which account for the radiation hardness of icosahedral boron rich solids, in the amorphous B4C thin films was supported by Fourier transform infrared spectroscopy. The pair distribution functions derived from selected area diffraction pattern of amorphous B 4C thin films showed that the short range order structure of amorphous B4C thin films is similar to beta-rhombohedral boron but with a shorter distance. The investigation of electrical properties of B4 C thin films showed that the resistivity of B4C thin films ranges from 695 O-cm to 9650 O-cm depending on the deposition temperature; the direct and indirect bandgaps for B4C thin films are 2.776 - 2.898 eV and 1.148 - 1.327 eV, respectively; the effective lifetime of excess charge carrier is close to 0.1 ms for B4C thin film deposited at room temperature and approximates to 1 ms for those deposited at 175 °C to 500 °C. Based on structural characterization and electrical properties of B4C thin films, a structural model of B4C thin films was proposed and supported by nanoindenter experiments, i.e., the hardness of thin films deposited at temperature in the range of 275 °C to 350 °C is lower than that of the films deposited at RT and 650 °C. Heterojunctions of B4C / n-Si (100) possessing photovoltaic response have been fabricated. The suitable deposition temperature for B 4C thin film to fabricate photovoltaic device is from 175 °C to 350 °C. When the Si substrate surface was not pre-cleaned before depositing B4C thin film, the B4C / n-Si (100) heterojunction has better photovoltaic responses, presumably because there were no sputter-produced defects on the surface of Si (100) substrate. Until now, the best achievable photovoltaic performance is B4C / n-Si (100) heterojunction with 200 nm thick B4C thin film when the Si (100) substrate surface was not pre-cleaned by RF sputtering. When this heterojunction was characterized using solar simulator with air mass 1.5 spectra, the short circuit current density is 1.484 mA/cm2, the open circuit voltage is about 0.389 V, and the power conversion efficiency is about 0.214 %. In addition, B5C thin films deposited by plasma enhanced chemical vapor deposition were used to make some of the devices studied in this dissertation. It was found that the Si-doped BC / n-Si (111) heterojunctions also demonstrates their photovoltaic and betavoltaic responses. Even after irradiated by a 120 keV electron beam to a fluence of 4.38x1017 electrons/cm 2, the heterojunctions still posses betavoltaic behavior and their responses to the incident irradiance density are similar to that before irradiation.

Aerosol-assisted chemical vapor deposition of ultra-thin CuOx films as hole transport material for planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Zhang, Zhixin; Chen, Shuqun; Li, Pingping; Li, Hongyi; Wu, Junshu; Hu, Peng; Wang, Jinshu

This paper reports on the fabrication of CuOx films to be used as hole transporting layer (HTL) in CH3NH3PbI3 perovskite solar cells (PSCs). Ultra-thin CuOx coatings were grown onto FTO substrates for the first time via aerosol-assisted chemical vapor deposition (AACVD) of copper acetylacetonate in methanol. After incorporating into the PSCs prepared at ambient air, a highest power conversion efficiency (PCE) of 8.26% with HTL and of 3.34% without HTL were achieved. Our work represents an important step in the development of low-cost CVD technique for fabricating ultra-thin metal oxide functional layers in thin film photovoltaics.

Characterization of sputtered iridium oxide thin films on planar and laser micro-structured platinum thin film surfaces for neural stimulation applications

NASA Astrophysics Data System (ADS)

Thanawala, Sachin

Electrical stimulation of neurons provides promising results for treatment of a number of diseases and for restoration of lost function. Clinical examples include retinal stimulation for treatment of blindness and cochlear implants for deafness and deep brain stimulation for treatment of Parkinsons disease. A wide variety of materials have been tested for fabrication of electrodes for neural stimulation applications, some of which are platinum and its alloys, titanium nitride, and iridium oxide. In this study iridium oxide thin films were sputtered onto laser micro-structured platinum thin films by pulsed-DC reactive sputtering of iridium metal in oxygen-containing atmosphere, to obtain high charge capacity coatings for neural stimulation applications. The micro-structuring of platinum films was achieved by a pulsed-laser-based technique (KrF excimer laser emitting at lambda=248nm). The surface morphology of the micro-structured films was studied using different surface characterization techniques. In-vitro biocompatibility of these laser micro-structured films coated with iridium oxide thin films was evaluated using cortical neurons isolated from rat embryo brain. Characterization of these laser micro-structured films coated with iridium oxide, by cyclic voltammetry and impedance spectroscopy has revealed a considerable decrease in impedance and increase in charge capacity. A comparison between amorphous and crystalline iridium oxide thin films as electrode materials indicated that amorphous iridium oxide has significantly higher charge capacity and lower impedance making it preferable material for neural stimulation application. Our biocompatibility studies show that neural cells can grow and differentiate successfully on our laser micro-structured films coated with iridium oxide. This indicates that reactively sputtered iridium oxide (SIROF) is biocompatible.

Morphology and Surface Energy of a Si Containing Semifluorinated Di-block Copolymer Thin Films.

NASA Astrophysics Data System (ADS)

Shrestha, Umesh; Clarson, Stephen; Perahia, Dvora

2013-03-01

The structure and composition of an interface influence stability, adhesiveness and response to external stimuli of thin polymeric films. Incorporation of fluorine affects interfacial energy as well as thermal and chemical stability of the layers. The incompatibility between the fluorinated and non-fluorinated blocks induces segregation that leads to long range correlations where the tendency of the fluorine to migrate to interfaces impacts the surface tension of the films. Concurrently Si in a polymeric backbone enhances the flexibility of polymeric chains. Our previous studies of poly trifluoro propyl methyl siloxane-polystyrene thin films with SiF fraction 0.03-0.5 as a function of temperature have shown that the SiF block drives layering parallel to the surface of the diblock. Here in we report the structure and interfacial energies of SiF-PS in the plane of the films, as a function of the volume fraction of the SiF block obtained from Atomic Force microscopy and contact angle measurement studies. This work is supported by NSF DMR - 0907390

Decoupling thermal, chemical, and mechanical strain components in thin films

NASA Astrophysics Data System (ADS)

Silberstein, Meredith; Crumlin, Ethan; Shao-Horn, Yang; Boyce, Mary

2011-03-01

Many electrochemical systems have performance which is affected by internal strains due to thermal and/or chemical stimuli. The bi-material curvature method is a means to quantify these thermal and chemical strains and their coupling with mechanical stress. In this method, a thin layer of the material of interest is deposited on a substrate of intermediate thickness. The composite assumes a curvature that depends on the mismatch strains between the substrate and film. The Stoney formula provides an explicit expression for the film stress as a function of the elastic substrate properties, film and substrate thickness, and curvature. Here we study two distinct materials systems: Nafion used as the polymer electrolyte in low temperature fuel cells, and epitaxial perovskite thin films used as a catalyst for the oxygen reduction reaction in solid oxide fuel cells. The thermal, chemical, and mechanical strains are quantitatively determined as functions of temperature and atmospheric conditions by monitoring the curvature evolution with changes in these parameters. The extent of coupling of the thermal and chemical strains with mechanical stress is evaluated by conducting the experiment at multiple substrate thicknesses.

Biopolymer Green Lubricant for Sustainable Manufacturing

PubMed Central

Shi, Shih-Chen; Lu, Fu-I

2016-01-01

We report on the preparation of a biopolymer thin film by hydroxypropyl methylcellulose (HPMC), which can be used as a dry green lubricant in sustainable manufacturing. The thin films were characterized through scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy; the films showed desirable levels of thickness, controllability, and uniformity. Tribology tests also showed desirable tribological and antiwear behaviors, caused by the formation of transfer layers. Zebrafish embryo toxicity studies showed that HPMC has excellent solubility and biocompatibility, which may show outstanding potential for applications as a green lubricant. The results of the present study show that these techniques for biopolymer HPMC provide an ecologically responsible and convenient method for preparing functional thin films, which is particularly applicable to sustainable manufacturing. PMID:28773462

Nanoporous Block Polymer Thin Films Functionalized with Bio-Inspired Ligands for the Efficient Capture of Heavy Metal Ions from Water.

PubMed

Weidman, Jacob L; Mulvenna, Ryan A; Boudouris, Bryan W; Phillip, William A

2017-06-07

Heavy metal contamination of water supplies poses a serious threat to public health, prompting the development of novel and sustainable treatment technologies. One promising approach is to molecularly engineer the chemical affinity of a material for the targeted removal of specific molecules from solution. In this work, nanoporous polymer thin films generated from tailor-made block polymers were functionalized with the bio-inspired moieties glutathione and cysteamine for the removal of heavy metal ions, including lead and cadmium, from aqueous solutions. In a single equilibrium stage, the films achieved removal rates of the ions in excess of 95%, which was consistent with predictions based on the engineered material properties. In a flow-through configuration, the thin films achieved an even greater removal rate of the metal ions. Furthermore, in mixed ion solutions the capacity of the thin films, and corresponding removal rates, did not demonstrate any reduction due to competitive adsorption effects. After such experiments the material was repeatedly regenerated quickly with no observed loss in capacity. Thus, these membranes provide a sustainable platform for the efficient purification of lead- and cadmium-contaminated water sources to safe levels. Moreover, their straightforward chemical modifications suggest that they could be engineered to treat sources containing other recalcitrant environmental contaminants as well.

Grazing Incidence Cross-Sectioning of Thin-Film Solar Cells via Cryogenic Focused Ion Beam: A Case Study on CIGSe

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

Sardashti, Kasra; Haight, Richard; Anderson, Ryan

2016-06-22

Cryogenic focused ion beam (Cryo-FIB) milling at near-grazing angles is employed to fabricate cross-sections on thin Cu(In,Ga)Se2 with >8x expansion in thickness. Kelvin probe force microscopy (KPFM) on sloped cross sections showed reduction in grain boundaries potential deeper into the film. Cryo Fib-KPFM enabled the first determination of the electronic structure of the Mo/CIGSe back contact, where a sub 100 nm thick MoSey assists hole extraction due to 45 meV higher work function. This demonstrates that CryoFIB-KPFM combination can reveal new targets of opportunity for improvement in thin-films photovoltaics such as high-work-function contacts to facilitate hole extraction through the backmore » interface of CIGS.« less

Investigations in structural morphological and optical properties of Bi-Pb-S system thin films

NASA Astrophysics Data System (ADS)

Malika, Boukhalfa; Noureddine, Benramdane; Mourad, Medles; Abdelkader, Outzourhit; Attouya, Bouzidi; Hind, Tabet-derraz

Bi2S3, PbS and Bi-Pb-S system thin films were grown on glass substrates by the spray pyrolysis technique. The films growth was realized by the reaction of aqueous solutions of bismuth trichloride (BiCl3) and trihydrate Lead Acetate (TLA) (Pb(CH3COO)2.3H2O) with thiourea on heated substrates. The films study was performed as a function of the TLA volume ratio (TLA vol. ratio) in the solution obtained by the mixture of BiCl3 and thiourea used as precursor solution (PrS). X-ray diffraction (XRD), field emitting scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) were used for structural and compositional analysis of the as deposited films. With the structural investigations, Bi2S3, PbS thin films and PbS-Bi2S3 composite thin films formation was confirmed. Optical properties of the deposited films were obtained using transmittance and reflectance measurements in the wavelength range [200-2500 nm]. The absorption edge shows a shift towards low energy with the increase of the TLA vol. ratio.The optical bandgaps for the films with various TLA vol. ratio are found to lie between those of the Bi2S3 and PbS ones. The optical parameters (extinction coefficient, refractive index, real and imaginary parts if the complex dielectric constant) of the thin films are also investigated. These are found to be dependent on the TLA vol. ratio.

Interfacial mechanisms for stability of surfactant-laden films

PubMed Central

Chai, Chew; Àlvarez-Valenzuela, Marco A.; Tajuelo, Javier; Fuller, Gerald G.

2017-01-01

Thin liquid films are central to everyday life. They are ubiquitous in modern technology (pharmaceuticals, coatings), consumer products (foams, emulsions) and also serve vital biological functions (tear film of the eye, pulmonary surfactants in the lung). A common feature in all these examples is the presence of surface-active molecules at the air-liquid interface. Though they form only molecular-thin layers, these surfactants produce complex surface stresses on the free surface, which have important consequences for the dynamics and stability of the underlying thin liquid film. Here we conduct simple thinning experiments to explore the fundamental mechanisms that allow the surfactant molecules to slow the gravity-driven drainage of the underlying film. We present a simple model that works for both soluble and insoluble surfactant systems in the limit of negligible adsorption-desorption dynamics. We show that surfactants with finite surface rheology influence bulk flow through viscoelastic interfacial stresses, while surfactants with inviscid surfaces achieve stability through opposing surface-tension induced Marangoni flows. PMID:28520734

Excitation of Love waves in a thin film layer by a line source.

NASA Technical Reports Server (NTRS)

Tuan, H.-S.; Ponamgi, S. R.

1972-01-01

The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.

High-fraction brookite films from amorphous precursors

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

Haggerty, James E. S.; Schelhas, Laura T.; Kitchaev, Daniil A.

2017-11-09

Structure-specific synthesis processes are of key importance to the growth of polymorphic functional compounds such as TiO 2, where material properties strongly depend on structure as well as chemistry. The robust growth of the brookite polymorph of TiO 2, a promising photocatalyst, has been difficult in both powder and thin-film forms due to the disparity of reported synthesis techniques, their highly specific nature, and lack of mechanistic understanding. In this work, we report the growth of high-fraction (~95%) brookite thin films prepared by annealing amorphous titania precursor films deposited by pulsed laser deposition. We characterize the crystallization process, eliminating themore » previously suggested roles of substrate templating and Na helper ions in driving brookite formation. Instead, we link phase selection directly to film thickness, offering a novel, generalizable route to brookite growth that does not rely on the presence of extraneous elements or particular lattice-matched substrates. In addition to providing a new synthesis route to brookite thin films, our results take a step towards resolving the problem of phase selection in TiO 2 growth, contributing to the further development of this promising functional material.« less

Oxygen Vacancy-Tuned Physical Properties in Perovskite Thin Films with Multiple B-site Valance States

DOE PAGES

Enriquez, Erik; Chen, Aiping; Harrell, Zach; ...

2017-04-18

Controlling oxygen content in perovskite oxides with ABO 3 structure is one of most critical steps for tuning their functionality. Notably, there have been tremendous efforts to understand the effect of changes in oxygen content on the properties of perovskite thin films that are not composed of cations with multiple valance states. Here, we study the effect of oxygen vacancies on structural and electrical properties in epitaxial thin films of SrFeO 3-δ (SFO), where SFO is a compound with multiple valance states at the B site. Various annealing treatments are used to produce different oxygen contents in the films, whichmore » has resulted in significant structural changes in the fully strained SFO films. The out-of-plane lattice parameter and tetragonality increase with decreasing oxygen concentration, indicating the crystal structure is closely related to the oxygen content. Importantly, variation of the oxygen content in the films significantly affects the dielectric properties, leakage conduction mechanisms, and the resistive hysteresis of the materials. These results establish the relationship between oxygen content and structural and functional properties for a range of multivalent transition metal oxides.« less

Oxygen Vacancy-Tuned Physical Properties in Perovskite Thin Films with Multiple B-site Valance States

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

Enriquez, Erik; Chen, Aiping; Harrell, Zach

Controlling oxygen content in perovskite oxides with ABO 3 structure is one of most critical steps for tuning their functionality. Notably, there have been tremendous efforts to understand the effect of changes in oxygen content on the properties of perovskite thin films that are not composed of cations with multiple valance states. Here, we study the effect of oxygen vacancies on structural and electrical properties in epitaxial thin films of SrFeO 3-δ (SFO), where SFO is a compound with multiple valance states at the B site. Various annealing treatments are used to produce different oxygen contents in the films, whichmore » has resulted in significant structural changes in the fully strained SFO films. The out-of-plane lattice parameter and tetragonality increase with decreasing oxygen concentration, indicating the crystal structure is closely related to the oxygen content. Importantly, variation of the oxygen content in the films significantly affects the dielectric properties, leakage conduction mechanisms, and the resistive hysteresis of the materials. These results establish the relationship between oxygen content and structural and functional properties for a range of multivalent transition metal oxides.« less

Corrosion, optical and magnetic properties of flexible iron nitride nano thin films deposited on polymer substrate

NASA Astrophysics Data System (ADS)

Khan, W. Q.; Wang, Qun; Jin, Xin; Yasin, G.

2017-11-01

Iron nitride thin films of different compositions and thicknesses were deposited on flexible polymer substrate in Ar/N2 atmosphere by reactive magnetron sputtering under varying nitrogen flow rates. The nano structured films were characterized by X-ray diffraction, UV-visible spectrophotometer, electrochemical impedance (EIS), atomic force (AFM) and transmission electron microscopies. The dependence of their functional properties on coating and growth conditions was studied in detail. It was found that the thin films show a uniform permeability in the frequency range of 200 MHz to 1 Ghz and can be used in this range without appreciable changes. Decrease of nitrogen flow rate resulted in the smoother surfaces which in turn increase transmittance quality and corrosion resistance. Functional properties are dependent of nature, relative concentration of the iron nitride phases and film thickness. Surface integrity is excellent for180 nm thick sample because the films appear to be very dense and free from open pores. By keeping sputtering power stable at 110 W, nitrogen flow rate of 10 sccm was ideal to develop the ferromagnetic γʹFe4N phase at room temperature.

Work functions of hafnium nitride thin films as emitter material for field emitter arrays

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

Gotoh, Yasuhito, E-mail: gotoh.yasuhito.5w@kyoto-u.ac.jp; Fujiwara, Sho; Tsuji, Hiroshi

The work functions of hafnium nitride thin films prepared by radio-frequency magnetron sputtering were investigated in vacuum, before and after surface cleaning processes, with a view of improving the properties of as-fabricated field emitter arrays comprising hafnium nitride emitters. The measurement of the work function was first performed for the as-deposited films and then for films subjected to surface cleaning process, either thermal treatment or ion bombardment. Thermal treatment at a maximum temperature of 300 °C reduced the work function by 0.7 eV. Once the film was heated, the work function maintained the reduced value, even after cooling to room temperature. Amore » little change in the work function was observed for the second and third thermal treatments. The ion bombardment was conducted by exposing the sample to a thin plasma for different sample bias conditions and processing times. When the sample was biased at −10 V, the work function decreased by 0.6 eV. The work function reduction became saturated in the early stage of the ion bombardment. When the sample was biased at −50 V, the work function exhibited different behaviors, that is, first it decreased rapidly and then increased in response to the increase in processing time. The lowest attainable work function was found to be 4.00 eV. It should be noted that none of the work function values reported in this paper were obtained using surfaces that were demonstrated to be free from oxygen contamination. The present results suggest that the current–voltage characteristics of a field emitter array can be improved by a factor of 25–50 by the examined postprocesses.« less

Y1Ba2Cu3O(7-delta) thin film dc SQUIDs (superconducting quantum interference device)

NASA Astrophysics Data System (ADS)

Racah, Daniel

1991-03-01

Direct current superconducting quantum interferometers (SQUIDs) based on HTSC thin films have been measured and characterized. The thin films used were of different quality: (1) Granular films on Sapphire substrates, prepared either by e-gun evaporation, by laser ablation or by MOCVD (metal oxide chemical vapor deposition), (2) Epitaxial films on MgO substrates. Modulations of the voltage on the SQUIDs as a function of the applied flux have been observed in a wide range of temperatures. The nature of the modulation was found to be strongly dependent on the morphology of the film and on its critical current. The SQUIDs based on granular films were relatively noisy, hysteretic and with a complicated V-phi shape. Those devices based on low quality (lowIc) granular films could be measured only at low temperatures (much lower than 77 K). While those of higher quality (granular films with high Ic) could be measured near to the superconductive transition. The SQUID based on high quality epitaxial film was measured near Tc and showed an anomalous, time dependent behavior.

Understanding of the development of in-plane residual stress in sol-gel-derived metal oxide thin films

NASA Astrophysics Data System (ADS)

Ohno, Kentaro; Uchiyama, Hiroaki; Kozuka, Hiromitsu

2012-01-01

The in-plane residual stress in thin films greatly affects their properties and functionality as well as the substrate bending, and hence is an important factor to be controlled. In order to obtain general knowledge on the development of residual stress in sol-gel-derived oxide thin films, the in-plane residual stress was measured for yttria stabilized zirconia gel films on Si(100) wafers as a function of firing temperature by measuring the substrate curvature. The films showed a rather complex variation in residual stress, and the mechanism of the residual stress evolution was discussed, referencing the intrinsic stress and the x-ray diffraction data. At low annealing temperatures of 100-200 °C, the residual tensile stress decreased and became compressive partially due to the structural relaxation occurring during cooling. When the firing temperature was increased over 200 °C, the residual stress turned tensile, and increased with increasing annealing temperature, which was attributed to the increase in intrinsic stress due to film densification as well as to the reduced structural relaxation due to the progress of densification. The residual tensile stress slightly decreased at firing temperatures of 500-600 °C, which was attributed to the reduction in intrinsic stress due to thermally activated atomic diffusion as well as to emergence of thermal stress. At firing temperature over 600 °C, the residual tensile stress increased again, which was attributed to the increase in thermal stress generated during cooling due to the increased Young's modulus of the film. Although appearing to be complicated, the whole variation of residual stress with firing temperature could be understood in terms of film densification, structural relaxation, atomic diffusion, progress of crystallization and thermal strain. The illustration presented in the work may provide a clear insight on how the residual stress could be developed in a variety of functional sol-gel-derived, crystalline oxide thin films.

Some optical and electron microscope comparative studies of excimer laser-assisted and nonassisted molecular-beam epitaxically grown thin GaAs films on Si

NASA Technical Reports Server (NTRS)

Lao, Pudong; Tang, Wade C.; Rajkumar, K. C.; Guha, S.; Madhukar, A.; Liu, J. K.; Grunthaner, F. J.

1990-01-01

The quality of GaAs thin films grown via MBE under pulsed excimer laser irradiation on Si substrates is examined in both laser-irradiated and nonirradiated areas using Raman scattering, Rayleigh scattering, and by photoluminescence (PL), as a function of temperature, and by TEM. The temperature dependence of the PL and Raman peak positions indicates the presence of compressive stress in the thin GaAs films in both laser-irradiated and nonirradiated areas. This indicates incomplete homogeneous strain relaxation by dislocations at the growth temperature. The residual compressive strain at the growth temperature is large enough such that even with the introduction of tensile strain arising from the difference in thermal expansion coefficients of GaAs and Si, a compressive strain is still present at room temperature for these thin GaAs/Si films.

Crystalline-silicon reliability lessons for thin-film modules

NASA Technical Reports Server (NTRS)

Ross, R. G., Jr.

1985-01-01

The reliability of crystalline silicon modules has been brought to a high level with lifetimes approaching 20 years, and excellent industry credibility and user satisfaction. The transition from crystalline modules to thin film modules is comparable to the transition from discrete transistors to integrated circuits. New cell materials and monolithic structures will require new device processing techniques, but the package function and design will evolve to a lesser extent. Although there will be new encapsulants optimized to take advantage of the mechanical flexibility and low temperature processing features of thin films, the reliability and life degradation stresses and mechanisms will remain mostly unchanged. Key reliability technologies in common between crystalline and thin film modules include hot spot heating, galvanic and electrochemical corrosion, hail impact stresses, glass breakage, mechanical fatigue, photothermal degradation of encapsulants, operating temperature, moisture sorption, circuit design strategies, product safety issues, and the process required to achieve a reliable product from a laboratory prototype.

Improving Fire Resistance of Cotton Fabric through Layer-by-Layer Assembled Graphene Multilayer Nanocoating

NASA Astrophysics Data System (ADS)

Jang, Wonjun; Chung, Il Jun; Kim, Junwoo; Seo, Seongmin; Park, Yong Tae; Choi, Kyungwho

2018-05-01

In this study, thin films containing poly(vinyl alcohol) (PVA) and graphene nanoplatelets (GNPs), stabilized with poly(4-styrene-sulfonic acid) (PSS), were assembled by a simple and cost-effective layer-by-layer (LbL) technique in order to introduce the anti-flammability to cotton. These antiflammable layers were characterized by using UV-vis spectrometry and quartz crystal microbalance as a function of the number of bilayers deposited. Scanning electron microscopy was used to visualize the morphology of the thin film coatings on the cotton fabric. The graphene-polymer thin films introduced anti-flammable properties through thermally stable carbonaceous layers at a high temperature. The thermal stability and flame retardant property of graphene-coated cotton was demonstrated by thermogravimetric analysis, cone calorimetry, and vertical flame test. The results indicate that LbL-assembled graphene-polymer thin films can be applied largely in the field of flame retardant.

Thin film ferroelectric electro-optic memory

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor); Thakoor, Anilkumar P. (Inventor)

1993-01-01

An electrically programmable, optically readable data or memory cell is configured from a thin film of ferroelectric material, such as PZT, sandwiched between a transparent top electrode and a bottom electrode. The output photoresponse, which may be a photocurrent or photo-emf, is a function of the product of the remanent polarization from a previously applied polarization voltage and the incident light intensity. The cell is useful for analog and digital data storage as well as opto-electric computing. The optical read operation is non-destructive of the remanent polarization. The cell provides a method for computing the product of stored data and incident optical data by applying an electrical signal to store data by polarizing the thin film ferroelectric material, and then applying an intensity modulated optical signal incident onto the thin film material to generate a photoresponse therein related to the product of the electrical and optical signals.

Thin film composition with biological substance and method of making

DOEpatents

Campbell, Allison A.; Song, Lin

1999-01-01

The invention provides a thin-film composition comprising an underlying substrate of a first material including a plurality of attachment sites; a plurality of functional groups chemically attached to the attachment sites of the underlying substrate; and a thin film of a second material deposited onto the attachment sites of the underlying substrate, and a biologically active substance deposited with the thin-film. Preferably the functional groups are attached to a self assembling monolayer attached to the underlying substrate. Preferred functional groups attached to the underlying substrate are chosen from the group consisting of carboxylates, sulfonates, phosphates, optionally substituted, linear or cyclo, alkyl, alkene, alkyne, aryl, alkylaryl, amine, hydroxyl, thiol, silyl, phosphoryl, cyano, metallocenyl, carbonyl, and polyphosphate. Preferred materials for the underlying substrate are selected from the group consisting of a metal, a metal alloy, a plastic, a polymer, a proteic film, a membrane, a glass or a ceramic. The second material is selected from the group consisting of inorganic crystalline structures, inorganic amorphus structures, organic crystalline structures, and organic amorphus structures. Preferred second materials are phosphates, especially calcium phosphates and most particularly calcium apatite. The biologically active molecule is a protein, peptide, DNA segment, RNA segment, nucleotide, polynucleotide, nucleoside, antibiotic, antimicrobal, radioisotope, chelated radioisotope, chelated metal, metal salt, anti-inflamatory, steriod, nonsteriod anti-inflammatory, analgesic, antihistamine, receptor binding agent, or chemotherapeutic agent, or other biologically active material. Preferably the biologically active molecule is an osteogenic factor the compositions listed above.

Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion.

PubMed

Reis, Rackel; Dumée, Ludovic F; He, Li; She, Fenghua; Orbell, John D; Winther-Jensen, Bjorn; Duke, Mikel C

2015-07-15

Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.

Development of a direct patterning method for functional oxide thin films using ultraviolet irradiation and hybrid-cluster gels and its application to thin-film transistor fabrication

NASA Astrophysics Data System (ADS)

Yoshimoto, Yuuki; Li, Jinwang; Shimoda, Tatsuya

2018-04-01

A gel state exists in the solution-solid conversion process. We found that solidification can be promoted by irradiating the gel with ultraviolet (UV) light. In this study, a patterning method without using a vacuum system or employing photoresist materials has been proposed wherein solidification was applied to a gel by UV irradiation. Indium oxide gel, indium gallium oxide gel, lanthanum zirconium oxide gel, and lanthanum ruthenium oxide gels were successfully patterned by using our technique. Moreover, an oxide thin-film transistor was fabricated by our novel patterning method and was successfully operated.

Revealing topological Dirac fermions at the surface of strained HgTe thin films via quantum Hall transport spectroscopy

NASA Astrophysics Data System (ADS)

Thomas, C.; Crauste, O.; Haas, B.; Jouneau, P.-H.; Bäuerle, C.; Lévy, L. P.; Orignac, E.; Carpentier, D.; Ballet, P.; Meunier, T.

2017-12-01

We demonstrate evidences of electronic transport via topological Dirac surface states in a thin film of strained HgTe. At high perpendicular magnetic fields, we show that the electron transport reaches the quantum Hall regime with vanishing resistance. Furthermore, quantum Hall transport spectroscopy reveals energy splittings of relativistic Landau levels specific to coupled Dirac surface states. This study provides insights in the quantum Hall effect of topological insulator (TI) slabs, in the crossover regime between two- and three-dimensional TIs, and in the relevance of thin TI films to explore circuit functionalities in spintronics and quantum nanoelectronics.

Investigation of Surface Sulfurization in CuIn1-x Gax S2-y Sey Thin Films by Using Kelvin Probe Force Microscopy.

PubMed

Kim, Haeri; Park, Se Jin; Kim, Byungwoo; Hwang, Yun Jeong; Min, Byoung Koun

2018-02-05

CuIn 1-x Ga x S 2-y Se y (CIGSSe) thin films have attracted a great deal of attention as promising absorbing materials for solar cell applications, owing to their favorable optical properties (e.g. a direct band gap and high absorption coefficients) and stable structure. Many studies have sought to improve the efficiency of solar cells using these films, and it has been found that surface modification through post-heat treatment can lead to surface passivation of surface defects and a subsequent increase in efficiency. The surface properties of solution-processed CIGSSe films are considered to be particularly important in this respect, owing to the fact that they are more prone to defects. In this work, CIGSSe thin films with differing S/Se ratios at their surface were synthesized by using a precursor solution and post-sulfurization heat treatment. These CIGSSe thin films were investigated with current-voltage and Kelvin probe force microscope (KPFM) analyses. Surface photovoltage (SPV), which is the difference in the work function in the dark and under illumination, was measured by using KPFM, which can examine the screening and the modification of surface charge through carrier trapping. As the concentration of S increases on the CIGSSe film surface, higher work functions and more positive SPV values were observed. Based on these measurements, we inferred the band-bending behavior of CIGSSe absorber films and proposed reasons for the improvement in solar cell performance. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Same Precursor, Two Different Products: Comparing the Structural Evolution of In–Ga–O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

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

Wood, Suzannah R.; Woods, Keenan N.; Plassmeyer, Paul N.

Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted In2O3 and In-substituted β-Ga2O3 with different degrees of substitution. X-ray total scatteringmore » and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-Ga2O3 phase, with a minor constituent of In2O3 with significantly larger coherence lengths. This amorphous β-Ga2O3 phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure–property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.« less

Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods

DOE PAGES

Heo, Sungyeon; Kim, Jongwook; Ong, Gary K.; ...

2017-08-08

Low-temperature processed mesoporous nanocrystal thin films are platforms for fabricating functional composite thin films on flexible substrates. Using a random arrangement of anisotropic nanocrystals can be a facile solution to generate pores without templates. However, the tendency for anisotropic particles to spontaneously assemble into a compact structure must be overcome. Here in this paper, we present a method to achieve random networking of nanorods during solution phase deposition by switching their ligand-stabilized colloidal nature into a charge-stabilized nature by a ligand-stripping chemistry. Ligand-stripped tungsten suboxide (WO 2.72) nanorods result in uniform mesoporous thin films owing to repulsive electrostatic forces preventingmore » nanorods from densely packing. Porosity and pore size distribution of thin films are controlled by changing the aspect ratio of the nanorods. This template-free mesoporous structure, achieved without annealing, provides a framework for introducing guest components, therefore enabling our fabrication of inorganic nanocomposite electrochromic films on flexible substrates. Following infilling of niobium polyoxometalate clusters into pores and successive chemical condensation, a WO x–NbO x composite film is produced that selectively controls visible and near-infrared light transmittance without any annealing required. The composite shows rapid switching kinetics and can be stably cycled between optical states over 2000 times. This simple strategy of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.« less

Template-Free Mesoporous Electrochromic Films on Flexible Substrates from Tungsten Oxide Nanorods

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

Heo, Sungyeon; Kim, Jongwook; Ong, Gary K.

Low-temperature processed mesoporous nanocrystal thin films are platforms for fabricating functional composite thin films on flexible substrates. Using a random arrangement of anisotropic nanocrystals can be a facile solution to generate pores without templates. However, the tendency for anisotropic particles to spontaneously assemble into a compact structure must be overcome. Here in this paper, we present a method to achieve random networking of nanorods during solution phase deposition by switching their ligand-stabilized colloidal nature into a charge-stabilized nature by a ligand-stripping chemistry. Ligand-stripped tungsten suboxide (WO 2.72) nanorods result in uniform mesoporous thin films owing to repulsive electrostatic forces preventingmore » nanorods from densely packing. Porosity and pore size distribution of thin films are controlled by changing the aspect ratio of the nanorods. This template-free mesoporous structure, achieved without annealing, provides a framework for introducing guest components, therefore enabling our fabrication of inorganic nanocomposite electrochromic films on flexible substrates. Following infilling of niobium polyoxometalate clusters into pores and successive chemical condensation, a WO x–NbO x composite film is produced that selectively controls visible and near-infrared light transmittance without any annealing required. The composite shows rapid switching kinetics and can be stably cycled between optical states over 2000 times. This simple strategy of using anisotropic nanocrystals gives insight into mesoporous thin film fabrication with broader applications for flexible devices.« less

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

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

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

DOE PAGES

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani; ...

2017-09-26

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Development of porous metal oxide thin films by co-evaporation

NASA Astrophysics Data System (ADS)

Tesfamichael, T.; Motta, Nunzio; Bostrom, Thor; Bell, J. M.

2007-03-01

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide-tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV-vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.

Application of surface analytical methods in thin film analysis

NASA Astrophysics Data System (ADS)

Wen, Xingu

Self-assembly and the sol-gel process are two promising methods for the preparation of novel materials and thin films. In this research, these two methods were utilized to prepare two types of thin films: self-assembled monolayers of peptides on gold and SiO2 sol-gel thin films modified with Ru(II) complexes. The properties of the resulting thin films were investigated by several analytical techniques in order to explore their potential applications in biomaterials, chemical sensors, nonlinear optics and catalysis. Among the analytical techniques employed in the study, surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS) and grazing angle reflection absorption Fourier transform infrared spectroscopy (RA-FTIR), are particularly useful in providing information regarding the compositions and structures of the thin films. In the preparation of peptide thin films, monodisperse peptides were self-assembled on gold substrate via the N-terminus-coupled lipoic acid. The film compositions were investigated by XPS and agreed well with the theoretical values. XPS results also revealed that the surface coverage of the self-assembled films was significantly larger than that of the physisorbed films and that the chemisorption between the peptides and gold surface was stable in solvent. Studies by angle dependent XPS (ADXPS) and grazing angle RA-FTIR indicated that the peptides were on average oriented at a small angle from the surface normal. By using a model of orientation distribution function, both the peptide tilt angle and film thickness can be well calculated. Ru(II) complex doped SiO2 sol-gel thin films were prepared by low temperature sol-gel process. The ability of XPS coupled with Ar + ion sputtering to provide both chemical and compositional depth profile information of these sol-gel films was evaluated. This technique, together with UV-VIS and electrochemical measurements, was used to investigate the stability of Ru complexes in the composite films. The stability of Ru complexes with respect to dopant leaching was dependent on the film microstructures. Three methods aiming to improve the dopant stability were also explored. In addition, the ion exchange properties of the composite films, upon exposure to various ions in aqueous solutions, were investigated by XPS, and the ion exchange mechanism was elucidated.

Evidence of charged puddles and induced dephasing in topological insulator thin films

NASA Astrophysics Data System (ADS)

Singh, Sourabh; Gopal, R. K.; Sarkar, Jit; Roy, Subhadip; Mitra, Chiranjib

2018-05-01

We investigate the dephasing mechanism in bulk insulating topological insulator thin films. The phase coherence length is extracted from magnetoresistance measurements at different temperatures. There is a crossover of the phase coherence length as a function of temperature signifying the role of more than one dephasing mechanism in the system. The dephasing rates have been studied systematically and explained.

High-Performance Organic Vertical Thin Film Transistor Using Graphene as a Tunable Contact.

PubMed

Liu, Yuan; Zhou, Hailong; Weiss, Nathan O; Huang, Yu; Duan, Xiangfeng

2015-11-24

Here we present a general strategy for the fabrication of high-performance organic vertical thin film transistors (OVTFTs) based on the heterostructure of graphene and different organic semiconductor thin films. Utilizing the unique tunable work function of graphene, we show that the vertical carrier transport across the graphene-organic semiconductor junction can be effectively modulated to achieve an ON/OFF ratio greater than 10(3). Importantly, with the OVTFT design, the channel length is determined by the organic thin film thickness rather than by lithographic resolution. It can thus readily enable transistors with ultrashort channel lengths (<200 nm) to afford a delivering current greatly exceeding that of conventional planar TFTs, thus enabling a respectable operation frequency (up to 0.4 MHz) while using low-mobility organic semiconductors and low-resolution lithography. With this vertical device architecture, the entire organic channel is sandwiched and naturally protected between the source and drain electrodes, which function as the self-passivation layer to ensure stable operation of both p- and n-type OVTFTs in ambient conditions and enable complementary circuits with voltage gain. The creation of high-performance and highly robust OVTFTs can open up exciting opportunities in large-area organic macroelectronics.

Low temperature reactive bonding

DOEpatents

Makowiecki, D.M.; Bionta, R.M.

1995-01-17

The joining technique is disclosed that requires no external heat source and generates very little heat during joining. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process. 5 figures.

Investigation of the structural, optical and electrical transport properties of n-doped CdSe thin films

NASA Astrophysics Data System (ADS)

Ali, H. M.; Abd El-Ghanny, H. A.

2008-04-01

Thin films of (CdSe)90(In2O3)10, (CdSe)90(SnO2)10 and (CdSe)90(ZnO)10 have been grown on glass substrates by the electron beam evaporation technique. It has been found that undoped and Sn or In doped CdSe films have two direct transitions corresponding to the energy gaps Eg and Eg+Δ due to spin-orbit splitting of the valence band. The electrical resistivity for n-doped CdSe thin films as a function of light exposure time has been studied. The influence of doping on the structural, optical and electrical characteristics of In doped CdSe films has been investigated in detail. The lattice parameters, grain size and dislocation were determined from x-ray diffraction patterns. The optical transmittance and band gap of these films were determined using a double beam spectrophotometer. The DC conductivity of the films was measured in vacuum using a two-probe technique.

Kinetic Effects on Self-Assembly and Function of Protein-Polymer Bioconjugates in Thin Films Prepared by Flow Coating.

PubMed

Chang, Dongsook; Huang, Aaron; Olsen, Bradley D

2017-01-01

The self-assembly of nanostructured globular protein arrays in thin films is demonstrated using protein-polymer block copolymers based on a model protein mCherry and the polymer poly(oligoethylene glycol acrylate) (POEGA). Conjugates are flow coated into thin films on a poly(ethylene oxide) grafted Si surface, forming self-assembled cylindrical nanostructures with POEGA domains selectively segregating to the air-film interface. Long-range order and preferential arrangement of parallel cylinders templated by selective surfaces are demonstrated by controlling relative humidity. Long-range order increases with coating speed when the film thicknesses are kept constant, due to reduced nucleation per unit area of drying film. Fluorescence emission spectra of mCherry in films prepared at <25% relative humidity shows a small shift suggesting that proteins are more perturbed at low humidity than high humidity or the solution state. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic Ellipsometry Studies of Thin Film a-Si:H Solar Cell Fabrication by Multichamber Deposition in the n-i-p Substrate Configuration

NASA Astrophysics Data System (ADS)

Dahal, Lila Raj

Real time spectroscopic ellipsometry (RTSE), and ex-situ mapping spectroscopic ellipsometry (SE) are powerful characterization techniques capable of performance optimization and scale-up evaluation of thin film solar cells used in various photovoltaics technologies. These non-invasive optical probes employ multichannel spectral detection for high speed and provide high precision parameters that describe (i) thin film structure, such as layer thicknesses, and (ii) thin film optical properties, such as oscillator variables in analytical expressions for the complex dielectric function. These parameters are critical for evaluating the electronic performance of materials in thin film solar cells and also can be used as inputs for simulating their multilayer optical performance. In this Thesis, the component layers of thin film hydrogenated silicon (Si:H) solar cells in the n-i-p or substrate configuration on rigid and flexible substrate materials have been studied by RTSE and ex-situ mapping SE. Depositions were performed by magnetron sputtering for the metal and transparent conducting oxide contacts and by plasma enhanced chemical vapor deposition (PECVD) for the semiconductor doped contacts and intrinsic absorber layers. The motivations are first to optimize the thin film Si:H solar cell in n-i-p substrate configuration for single-junction small-area dot cells and ultimately to scale-up the optimized process to larger areas with minimum loss in device performance. Deposition phase diagrams for both i- and p -layers on 2" x 2" rigid borosilicate glass substrate were developed as functions of the hydrogen-to-silane flow ratio in PECVD. These phase diagrams were correlated with the performance parameters of the corresponding solar cells, fabricated in the Cr/Ag/ZnO/n/i/ p/ITO structure. In both cases, optimization was achieved when the layers were deposited in the protocrystalline phase. Identical solar cell structures were fabricated on 6" x 6" borosilicate glass with 256 cells followed by ex-situ mapping SE on each cell to achieve better statistics for solar cell optimization by correlating local structural parameters with solar cell parameters. Solar cells of similar structure were also fabricated on flexible polymer substrates in the roll-to-roll configuration. In this configuration as well, RTSE was demonstrated as an effective process monitoring and control tool for thin film photovoltaics.

Intermediate surface structure between step bunching and step flow in SrRuO3 thin film growth

NASA Astrophysics Data System (ADS)

Bertino, Giulia; Gura, Anna; Dawber, Matthew

We performed a systematic study of SrRuO3 thin films grown on TiO2 terminated SrTiO3 substrates using off-axis magnetron sputtering. We investigated the step bunching formation and the evolution of the SRO film morphology by varying the step size of the substrate, the growth temperature and the film thickness. The thin films were characterized using Atomic Force Microscopy and X-Ray Diffraction. We identified single and multiple step bunching and step flow growth regimes as a function of the growth parameters. Also, we clearly observe a stronger influence of the step size of the substrate on the evolution of the SRO film surface with respect to the other growth parameters. Remarkably, we observe the formation of a smooth, regular and uniform ``fish skin'' structure at the transition between one regime and another. We believe that the fish skin structure results from the merging of 2D flat islands predicted by previous models. The direct observation of this transition structure allows us to better understand how and when step bunching develops in the growth of SrRuO3 thin films.

Photoactive and self-sensing P3HT-based thin films for strain and corrosion monitoring

NASA Astrophysics Data System (ADS)

Ryu, Donghyeon; Loh, Kenneth J.

2014-03-01

Structural systems deteriorate due to excessive deformation and corrosive environments. If damage is left undetected, they can propagate to cause sudden collapse. However, one of the main difficulties of monitoring damage progression is that, for example, excessive/plastic deformation and corrosion are drastically different physical processes. Strain is a mechanical phenomenon, whereas corrosion is a complex electrochemical process. The current strategy for structural health monitoring (SHM) is to use either different types of sensors or to employ system identification for quantifying overall changes to the structure. In this study, an alternative SHM paradigm is proposed in that a single, multifunctional material would be able to selectively sense different but simultaneously occurring structural damage. In particular, a photoactive and self-sensing thin film was developed for monitoring strain and corrosion. Another unique aspect was that the films were self-sensing and did not depend on external electrical energy for operations. First, the thin films were fabricated using photoactive poly(3-hexylthiophene) (P3HT) and other functional polymers using spin-coating and layerby- layer assembly. Second, the fabricated thin films were interrogated using an ultraviolet-visible (UV-Vis) spectrophotometer for quantifying their optical response to applied external stimuli, such as strain and exposure to pH buffer solutions. Lastly, the multifunctional thin films were tested and validated for strain and pH sensing. Interrogation of these separate responses was achieved by illuminating the thin films different wavelengths of light and then measuring the corresponding electrical current generated.

Optimization of vertical and lateral distances between target and substrate in deposition process of CuGaSe 2 thin films using one-step sputtering

DOE PAGES

Park, Jae -Cheol; Al-Jassim, Mowafak; Kim, Tae -Won

2017-02-01

Here, copper gallium selenide (CGS) thin films were fabricated using a combinatorial one-step sputtering process without an additional selenization process. The sample libraries as a function of vertical and lateral distance from the sputtering target were synthesized on a single soda-lime glass substrate at the substrate temperature of 500 °C employing a stoichiometric CGS single target. As we increased the vertical distance between the target and substrate, the CGS thin films had more stable and uniform characteristics in structural and chemical properties. Under the optimized conditions of the vertical distance (150 mm), the CGS thin films showed densely packed grainsmore » and large grain sizes up to 1 μm in scale with decreasing lateral distances. The composition ratio of Ga/[Cu+Ga] and Se/[Cu+Ga] showed 0.50 and 0.93, respectively, in nearly the same composition as the sputtering target. X-ray diffraction and Raman spectroscopy revealed that the CGS thin films had a pure chalcopyrite phase without any secondary phases such as Cu–Se or ordered vacancy compounds, respectively. In addition, we found that the optical bandgap energies of the CGS thin films are shifted from 1.650 to 1.664 eV with decreasing lateral distance, showing a near-stoichiometric region with chalcopyrite characteristics.« less

Preparation of SiO2 Passivation Thin Film for Improved the Organic Light-Emitting Device Life Time

NASA Astrophysics Data System (ADS)

Hong, Jeong Soo; Kim, Sang Mo; Kim, Kyung-Hwan

2011-08-01

To improve the organic light-emitting diode (OLED) lifetime, we prepared a SiO2 thin film for OLED passivation using a facing target sputtering (FTS) system as a function of oxygen gas flow rate and working pressure. The properties of the SiO2 thin film were examined by Fourier transform infrared (FT-IR), photoluminescence (PL) intensity measurement, field emission scanning electron microscopy (FE-SEM), and ultraviolet-visible (UV-vis) spectrometry that As a result, we found that a SiO2 thin film is formed at a 2 sccm oxygen gas flow rate and results the minimum damage to the organic layer is observed at a 1 mTorr working pressure. Also, from the water vapor transmission rate (WVTR), we observed that all of the as-deposited SiO2 thin films showed the ability of blocking moisture. After the properties were evaluated, an optimized SiO2 thin film was applied to OLED passivation. As a result, the property of the OLED fabricated by SiO2 passivation is similar to the OLED fabricated by glass passivation. However, the performance of OLED was degraded by enhancing of SiO2 passivation. This is the organic layer of the device is exposed to plasma for a prolonged period. Therefore, a method of minimizing damage to the organic layer and optimum conditions for what are important.

Study of organic-inorganic hetero-interfaces and electrical transport in semiconducting nanostructures

NASA Astrophysics Data System (ADS)

Wagner, Sean Robert

As the electronics industry continues to evolve and move towards functional electronic devices with increasing complexity and functionality, it becomes important to explore materials outside the regime of conventional semiconductors. Organic semiconducting small molecules have received a large amount of attention due to their high degree of flexibility, the option to perform molecular synthesis to modify their electronic and magnetic properties, and their ability to organize into highly-ordered functionalized nanostructures and thin films. Being able to form complex nanostructures and thin films with molecular precision, while maintaining the ability to tune properties through modifications in the molecular chemistry could result in vast improvements in conventional device architectures. However, before this is realized, there still remains a significant lack of understanding regarding how these molecules interact with various substrate surfaces as well as their intermolecular interactions. The interplay between these interactions can produce drastic changes in the molecular orientation and ordering at the hetero-interface, which can affect the transport properties of the molecular thin film and ultimately modify the performance of the organic electronic device. This study first focuses on the growth dynamics, molecular ordering, and molecular orientation of metal phthalocyanine (MPc) molecules, particularly on Si, a substrate which is notoriously difficult to form an organized organic thin film on due to the surface dangling bonds. By deactivating these bonds, the formation of a highly ordered organic molecular thin film becomes possible. Combining scanning tunneling microscopy, scanning tunneling spectroscopy, low-energy electron diffraction, and density functional theory calculations, the growth evolution of MPc molecules ( M = Zn, Cu, Co) from the single molecule level to multilayered films on the deactivated Si(111)-B surface is investigated. Initial tests are centered around thermally evaporated ZnPc. These molecules display a highly-ordered, close-packed, tilted configuration which differs from any known bulk packing motif. The ZnPc molecules are able to diffuse rapidly on the Si surface and preferentially nucleate at Si step-edges. This is followed by the formation of highly-ordered anisotropic stripe structures which grow across the Si terraces, i.e. anisotropic step-flow growth. The step-flow growth mode further impacts the growth by reducing the allowed symmetry of the molecular domains such that thin films with an exclusive in-plane molecular ordering are formed. Additionally, the ZnPc tilted packing motif stabilizes the molecular film, allowing it to maintain this packing for multilayered films, despite the decreasing substrate influence. The strength of the MPc-substrate interaction can be modified by changing the central transition-metal ion within the molecule. Through selective p-d orbital coupling between MPc molecules and the substrate, the degree of orbital coupling can induce modifications in the molecular ordering and orientation of MPc molecules at the interface. The secondary focus of this study is to initiate preliminary experimentation towards understanding how ordered organic molecular thin films can be applied to silicon-based devices that could have a significant impact on the electronics market. Si nanomembrane is a flexible, low-dimensional nanomaterial with electronic properties that are highly sensitive to the interface condition. By merging the knowledge of MPc thin film growth on Si with Si nanomembrane technology, possibilities towards modifying the transport properties of nanomaterials through engineering the organic-inorganic hetero-interface can be explored.

4D Printed Actuators with Soft-Robotic Functions.

PubMed

López-Valdeolivas, María; Liu, Danqing; Broer, Dick Jan; Sánchez-Somolinos, Carlos

2018-03-01

Soft matter elements undergoing programed, reversible shape change can contribute to fundamental advance in areas such as optics, medicine, microfluidics, and robotics. Crosslinked liquid crystalline polymers have demonstrated huge potential to implement soft responsive elements; however, the complexity and size of the actuators are limited by the current dominant thin-film geometry processing toolbox. Using 3D printing, stimuli-responsive liquid crystalline elastomeric structures are created here. The printing process prescribes a reversible shape-morphing behavior, offering a new paradigm for active polymer system preparation. The additive character of this technology also leads to unprecedented geometries, complex functions, and sizes beyond those of typical thin-films. The fundamental concepts and devices presented therefore overcome the current limitations of actuation energy available from thin-films, thereby narrowing the gap between materials and practical applications. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection of magnetic moment in thin films with a home-made vibrating sample magnetometer

NASA Astrophysics Data System (ADS)

Jordán, D.; González-Chávez, D.; Laura, D.; León Hilario, L. M.; Monteblanco, E.; Gutarra, A.; Avilés-Félix, L.

2018-06-01

This paper explores the optimization of an array of pick-up coils in a home-made vibrating sample magnetometer for the detection of magnetic moment in thin films. Sensitivity function of a 4-coils Mallinson configuration was numerically studied for the determination of the physical dimensions that enhance the sensitivity of the magnetometer. By performing numerical simulations using the Biot-Savart law combined with the principle of reciprocity we were able to determine the maximum values of sensitivity and the influence of the separation of the coils on the sensitivity function. After the optimization of the pick-up coils, the vibrating sample magnetometer was able to detect the magnetic moment of a 100 nm-thickness Fe19 Ni81 magnetic thin film along and perpendicular to the in-plane anisotropy easy axis. The implemented vibrating sample magnetometer is able to detect changes in the magnetic moment of ∼ 2 × 10-4 emu.

Surface half-metallicity of CrS thin films and perfect spin filtering and spin diode effects of CrS/ZnSe heterostructure

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

Gao, G. Y., E-mail: guoying-gao@mail.hust.edu.cn; Yao, K. L., E-mail: klyao@mail.hust.edu.cn

2014-11-03

Recently, ferromagnetic zinc-blende Mn{sub 1−x}Cr{sub x}S thin films (above x = 0.5) were fabricated experimentally on ZnSe substrate, which confirmed the previous theoretical prediction of half-metallic ferromagnetism in zinc-blende CrS. Here, we theoretically reveal that both Cr- and S-terminated (001) surfaces of the CrS thin films retain the half-metallicity. The CrS/ZnSe(001) heterogeneous junction exhibits excellent spin filtering and spin diode effects, which are explained by the calculated band structure and transmission spectra. The perfect spin transport properties indicate the potential applications of half-metallic CrS in spintronic devices. All computational results are obtained by using the density functional theory combined with nonequilibrium Green'smore » function.« less

Ultra thin metallic coatings to control near field radiative heat transfer

NASA Astrophysics Data System (ADS)

Esquivel-Sirvent, R.

2016-09-01

We present a theoretical calculation of the changes in the near field radiative heat transfer between two surfaces due to the presence of ultra thin metallic coatings on semiconductors. Depending on the substrates, the radiative heat transfer is modulated by the thickness of the ultra thin film. In particular we consider gold thin films with thicknesses varying from 4 to 20 nm. The ultra-thin film has an insulator-conductor transition close to a critical thickness of dc = 6.4 nm and there is an increase in the near field spectral heat transfer just before the percolation transition. Depending on the substrates (Si or SiC) and the thickness of the metallic coatings we show how the near field heat transfer can be increased or decreased as a function of the metallic coating thickness. The calculations are based on available experimental data for the optical properties of ultrathin coatings.

Metal-insulator transition characteristics of VO2 thin films grown on Ge(100) single crystals

NASA Astrophysics Data System (ADS)

Yang, Z.; Ko, C.; Ramanathan, S.

2010-10-01

Phase transitions exhibited by correlated oxides could be of potential relevance to the emerging field of oxide electronics. We report on the synthesis of high-quality VO2 thin films grown on single crystal Ge(100) substrates by physical vapor deposition and their metal-insulator transition (MIT) properties. Thermally triggered MIT is demonstrated with nearly three orders of magnitude resistance change across the MIT with transition temperatures of 67 °C (heating) and 61 °C (cooling). Voltage-triggered hysteretic MIT is observed at room temperature at threshold voltage of ˜2.1 V for ˜100 nm thickness VO2 films. Activation energies for electron transport in the insulating and conducting states are obtained from variable temperature resistance measurements. We further compare the properties of VO2 thin films grown under identical conditions on Si(100) single crystals. The VO2 thin films grown on Ge substrate show higher degree of crystallinity, slightly reduced compressive strain, larger resistance change across MIT compared to those grown on Si. Depth-dependent x-ray photoelectron spectroscopy measurements were performed to provide information on compositional variation trends in the two cases. These results suggest Ge could be a suitable substrate for further explorations of switching phenomena and devices for thin film functional oxides.

Structure property relationships in gallium oxide thin films grown by pulsed laser deposition [Structure property relationships in Ga 2O 3 thin films grown by pulsed laser deposition

DOE PAGES

Garten, Lauren M.; Zakutayev, Andriy; Perkins, John D.; ...

2016-11-21

Beta-gallium oxide (β-Ga 2O 3) is of increasing interest to the optoelectronic community for transparent conductor and power electronic applications. Considerable variability exists in the literature on the growth and doping of Ga 2O 3 films, especially as a function of growth approach, temperature, and oxygen partial pressure. Here pulsed laser deposition (PLD) was used to grow high-quality β-Ga 2O 3 films on (0001) sapphire and (–201) Ga 2O 3 single crystals and to explore the growth, stability, and dopability of these films as function of temperature and oxygen partial pressure. As a result, there is a strong temperature dependencemore » to the phase formation, morphology, and electronic properties of β-Ga 2O 3 from 350 to 550 °C.« less

Investigation of physicochemical and tribological properties of transparent oxide semiconducting thin films based on Ti-V oxides

NASA Astrophysics Data System (ADS)

Mazur, M.; Sieradzka, K.; Kaczmarek, D.; Domaradzki, J.; Wojcieszak, D.; Domanowski, P.

2013-08-01

In this paper investigations of structural and optical properties of nanocrystalline Ti-V oxide thin films are described. The films were deposited onto Corning 7059 glass using a modified reactive magnetron sputtering method. Structural investigations of prepared Ti-V oxides with vanadium addition of 19 at. % revealed amorphous structure, while incorporation of 21 and 23 at. % of vanadium resulted in V2O5 formation with crystallites sizes of 12.7 and 32.4 nm, respectively. All prepared thin films belong to transparent oxide semiconductors due to their high transmission level of ca. 60-75 % in the visible light range, and resistivity in the range of 3.3·102-1.4·105 Ωcm. Additionally, wettability and hardness tests were performed in order to evaluate the usefulness of the films for functional coatings.

Nonlinear microwave response of an MgB2 thin film

NASA Astrophysics Data System (ADS)

Purnell, A. J.; Cohen, L. F.; Zhai, H. Y.; Christen, H. M.; Paranthaman, M. P.; Lowndes, D. H.; Hao, Ling; Gallop, J. C.

2004-04-01

MgB2 is a two-gap superconductor and as a result may manifest unusual physical properties. The performance of MgB2 films at microwave frequencies has so far been rather poor compared to that of Nb alloys and this may result from intrinsic behaviour related to the double-gap structure or extrinsic properties due to non-optimized thin films. Here we give a detailed report on the microwave magnetic field dependent surface impedance of an MgB2 thin film, using a parallel plate resonator, as a function of temperature. We discuss whether the framework used to analyse nonlinear behaviour for other superconductors, both low and high Tc, but single-gap, has any validity for MgB2 and whether the films are limited by intrinsic or extrinsic behaviour. The key result is the observation of junction-type switching effects at high microwave power.

Supersonic plasma outflow in a plasmochemical method of amorphous silicon thin films formation

NASA Astrophysics Data System (ADS)

Baranova, L. V.; Strunin, V. I.; Khudaibergenov, G. Zh

2018-01-01

As a result of the numerical modeling of gasdynamic functions of a nozzle of Laval there obtained its parameters which form supersonic plasma jet outflow in a process of amorphous silicon thin films deposition. According to the nozzle design parameters, there obtained amorphous silicon thin films and studied uniformity of the thickness of the synthesized coatings. It was also performed that due to a low translational temperature at the nozzle exit the relaxation losses reduce significantly, “freezing” the vibrational degrees of freedom and the degrees of freedom of the transverse motion of the particles, and increasing the energy efficiency of the film formation process. All this is caused by the fact that on the surface of a growing film only the products of primary interaction of electrons with molecules of a silicon-containing gas in the plasmatron do interact.

Electronic Structure of the Metastable Epitaxial Rock-Salt SnSe {111 } Topological Crystalline Insulator

NASA Astrophysics Data System (ADS)

Jin, Wencan; Vishwanath, Suresh; Liu, Jianpeng; Kong, Lingyuan; Lou, Rui; Dai, Zhongwei; Sadowski, Jerzy T.; Liu, Xinyu; Lien, Huai-Hsun; Chaney, Alexander; Han, Yimo; Cao, Michael; Ma, Junzhang; Qian, Tian; Wang, Shancai; Dobrowolska, Malgorzata; Furdyna, Jacek; Muller, David A.; Pohl, Karsten; Ding, Hong; Dadap, Jerry I.; Xing, Huili Grace; Osgood, Richard M.

2017-10-01

Topological crystalline insulators have been recently predicted and observed in rock-salt structure SnSe {111 } thin films. Previous studies have suggested that the Se-terminated surface of this thin film with hydrogen passivation has a reduced surface energy and is thus a preferred configuration. In this paper, synchrotron-based angle-resolved photoemission spectroscopy, along with density functional theory calculations, is used to demonstrate that a rock-salt SnSe {111 } thin film epitaxially grown on Bi2Se3 has a stable Sn-terminated surface. These observations are supported by low-energy electron diffraction (LEED) intensity-voltage measurements and dynamical LEED calculations, which further show that the Sn-terminated SnSe {111 } thin film has undergone a surface structural relaxation of the interlayer spacing between the Sn and Se atomic planes. In sharp contrast to the Se-terminated counterpart, the observed Dirac surface state in the Sn-terminated SnSe {111 } thin film is shown to yield a high Fermi velocity, 0.50 ×106 m /s , which suggests a potential mechanism of engineering the Dirac surface state of topological materials by tuning the surface configuration.

Electronic Structure of the Metastable Epitaxial Rock-Salt SnSe { 111 } Topological Crystalline Insulator

DOE PAGES

Jin, Wencan; Vishwanath, Suresh; Liu, Jianpeng; ...

2017-10-25

Topological crystalline insulators have been recently predicted and observed in rock-salt structure SnSe {111} thin films. Previous studies have suggested that the Se-terminated surface of this thin film with hydrogen passivation has a reduced surface energy and is thus a preferred configuration. In this paper, synchrotron-based angle-resolved photoemission spectroscopy, along with density functional theory calculations, is used to demonstrate that a rock-salt SnSe {111} thin film epitaxially grown on Bi 2Se 3 has a stable Sn-terminated surface. These observations are supported by low-energy electron diffraction (LEED) intensity-voltage measurements and dynamical LEED calculations, which further show that the Sn-terminated SnSe {111}more » thin film has undergone a surface structural relaxation of the interlayer spacing between the Sn and Se atomic planes. In sharp contrast to the Se-terminated counterpart, the observed Dirac surface state in the Sn-terminated SnSe {111} thin film is shown to yield a high Fermi velocity, 0.50 x 10 6 m/s, which suggests a potential mechanism of engineering the Dirac surface state of topological materials by tuning the surface configuration.« less

Molecularly thin fluoro-polymeric nanolubricant films: tribology, rheology, morphology, and applications.

PubMed

Chung, Pil Seung; Jhon, Myung S; Choi, Hyoung Jin

2016-03-21

Molecularly thin perfluoropolyether (PFPE) has been used extensively as a high-performance lubricant in various applications and, more importantly, on carbon overcoats to enhance the reliability and lubrication of micro-/nanoelectro-mechanical systems, where the tribological performance caused by its molecular architecture is a critical issue, as are its physical properties and rheological characteristics. This Highlight addresses recent trends in the development of fluoro-polymeric lubricant films with regard to their tribology, rheology, and physio-chemical properties as they relate to heat-assisted magnetic recording. Nanorheology has been employed to examine the dynamic response of nonfunctional and functional PFPEs, while the viscoelastic properties of nanoscale PFPE films and the relaxation processes as a function of molecular structure and end-group functionality were analyzed experimentally; furthermore, the characteristics of binary blends were reported.

Influence of post-deposition annealing on structural, morphological and optical properties of copper (II) acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-05-21

In this study, the effect of thermal annealing under vacuum conditions on structural, morphological and optical properties of thermally evaporated copper (II) acetylacetonate, cu(acac) 2 , thin films were investigated. The copper (II) acetylacetonate thin films were deposited using thermal evaporation technique at vacuum pressure ~1 × 10 -5  mbar. The deposited films were thermally annealed at 323, 373, 423, and 473 K for 2 h in vacuum. The thermogravimetric analysis of cu(acac) 2 powder indicated a thermal stability of cu(acac) 2 up to 423 K. The effects of thermal annealing on the structural properties of cu(acac) 2 were evaluated employing X-ray diffraction method and the analysis showed a polycrystalline nature of the as-deposited and annealed films with a preferred orientation in [1¯01] direction. Fourier transformation infrared (FTIR) technique was used to negate the decomposition of copper (II) acetylacetonate during preparation or/and annealing up to 423 K. The surface morphology of the prepared films was characterized by means of field emission scanning electron microscopy (FESEM). A significant enhancement of the morphological properties of cu(acac) 2 thin films was obtained till the annealing temperature reaches 423 K. The variation of optical constants that estimated from spectrophotometric measurements of the prepared thin films was investigated as a function of annealing temperature. The annealing process presented significantly impacted the nonlinear optical properties such as third-order optical susceptibility χ (3) and nonlinear refractive index n 2 of cu(acac) 2 thin films. Copyright © 2018 Elsevier B.V. All rights reserved.

Correlation Between Material Properties of Ferroelectric Thin Films and Design Parameters for Microwave Device Applications: Modeling Examples and Experimental Verification

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; VanKeuls, Fred W.; Subramanyam, Guru; Mueller, Carl H.; Romanofsky, Robert R.; Rosado, Gerardo

2000-01-01

The application of thin ferroelectric films for frequency and phase agile components is the topic of interest of many research groups worldwide. Consequently, proof-of-concepts (POC) of different tunable microwave components using either (HTS, metal)/ferroelectric thin film/dielectric heterostructures or (thick, thin) film "flip-chip" technology have been reported. Either as ferroelectric thin film characterization tools or from the point of view of circuit implementation approach, both configurations have their respective advantages and limitations. However, we believe that because of the progress made so far using the heterostructure (i.e., multilayer) approach, and due to its intrinsic features such as planar configuration and monolithic integration, a study on the correlation of circuit geometry aspects and ferroelectric material properties could accelerate the insertion of this technology into working systems. In this paper, we will discuss our study performed on circuits based on microstrip lines at frequencies above 10 GHz, where the multilayer configuration offers greater ease of insertion due to circuit's size reduction. Modeled results of relevant circuit parameters such as the characteristic impedance, effective dielectric constant, and attenuation as a function of ferroelectric film's dielectric constant, tans, and thickness, will be presented for SrTiO3 and Ba(x)Sr(1-x)TiO3 ferroelectric films. A comparison between the modeled and experimental data for some of these parameters will be presented.

Engineering On-Surface Spin Crossover: Spin-State Switching in a Self-Assembled Film of Vacuum-Sublimable Functional Molecule.

PubMed

Kumar, Kuppusamy Senthil; Studniarek, Michał; Heinrich, Benoît; Arabski, Jacek; Schmerber, Guy; Bowen, Martin; Boukari, Samy; Beaurepaire, Eric; Dreiser, Jan; Ruben, Mario

2018-03-01

The realization of spin-crossover (SCO)-based applications requires study of the spin-state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface-bound thin molecular film is either quenched or heavily altered due to: (i) molecule-surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self-assembly strategy is proposed to fabricate thin spin-switchable surface-bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H 2 B(pz) 2 ) 2 (bpy)] (pz = pyrazole, bpy = 2,2'-bipyridine) with a dodecyl (C 12 ) alkyl chain yields a classical amphiphile-like functional and vacuum-sublimable charge-neutral Fe II complex, [Fe(H 2 B(pz) 2 ) 2 (C 12 -bpy)] (C 12 -bpy = dodecyl[2,2'-bipyridine]-5-carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiO x surfaces of the complex show comparable spin-state switching characteristics mediated by similar lamellar bilayer like self-assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO-based applications, especially in molecular spintronics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Radiation response of cubic mesoporous silicate and borosilicate thin films

NASA Astrophysics Data System (ADS)

Manzini, Ayelén; Alurralde, Martín; Luca, Vittorio

2018-01-01

The radiation response has been studied of cubic mesoporous silicate and borosilicate thin films having different boron contents prepared using the block copolymer template Brij 58 and the dip coating technique. The degree of pore ordering of the films was analysed using low-angle X-ray diffraction and film thickness measured by X-ray reflectivity. For films calcined at 350 °C, the incorporation of boron resulted in a reproducible oscillatory variation in the d-spacing and intensity of the primary reflection as a function of boron content. A clear peak was observed in the d-spacing at 5-10 mol% boron incorporation. For borosilicate films of a given composition an overall suppression of d-spacing was observed as a function of aging time relative to films that did not contain boron. This was ascribed to a slow condensation process. The films were irradiated in pile with neutrons and with iodine ions at energies of 180 keV and 70 MeV. Neutron irradiation of the silicate thin films for periods up to 30 days and aged for 400 days resulted in little reduction in either d-spacing or intensity of the primary low-angle X-ray reflection indicating that the films retained their mesopore ordering. In contrast borosilicate films for which the B (n, α) reaction was expected to result in enhanced displacement damage showed much larger variations in X-ray parameters. For these films short irradiation times resulted in a reduction of the d-spacing and intensity of the primary reflections considerably beyond that observed through aging. It is concluded that prolonged neutron irradiation and internal α irradiation have only a small, although measurable, impact on mesoporous borosilicate thin films increasing the degree of condensation and increasing unit cell contraction. When these borosilicate films were irradiated with iodine ions, more profound changes occurred. The pore ordering of the films was significantly degraded when low energy ions were used. In some cases the degree of damage was such that no low-angle reflection could be observed. This degradation of pore ordering was confirmed in scanning electron microscopy images of the irradiated films.

Preparation, linear and NLO properties of DNA-CTMA-SBE complexes

NASA Astrophysics Data System (ADS)

Manea, Ana-Maria; Rau, Ileana; Kajzar, Francois; Meghea, Aurelia

2013-10-01

Synthesis of deoxyribonucleic acid (DNA) - was cetyltrimethylammonium (CTMA) - sea buckthorn extract (SBE) at different concentrations is decribed. The complexes were processed into good optical quality thin films by spin coating on different substrates such as: glass, silica and ITO covered glass substrates. SBE contains many bioactive substances that can be used in the treatment of several diseases, such as cardiovascular disease, cancer, and acute mountain sickness. The obtained thin films were characterized for their spectroscopic, fluorescent, linear and nonlinear optical properties as function of SBE concentration. The third-order nonlinear optical (NLO) properties of thin films were determined by the optical third-harmonic generation technique at 1 064.2 nm fundamental wavelength.

Studies on Various Functional Properties of Titania Thin Film Developed on Glazed Ceramic Wall Tiles

NASA Astrophysics Data System (ADS)

Anil, Asha; Darshana R, Bangoria; Misra, S. N.

A sol-gel based TiO2 thin film was applied on glazed wall tiles for studying its various functional properties. Thin film was deposited by spin coating on the substrate and subjected to curing at different temperatures such as 600°C, 650, 700°C, 750°C and 800°C with 10 minutes soaking. The gel powder was characterized by FTIR, DTA/TG and XRD. Microstructure of thin film was analyzed by FESEM and EDX. Surface properties of the coatings such as gloss, colour difference, stain resistance, mineral hardness and wettability were extensively studied. The antibacterial activity of the surface of coated substrate against E. coli was also examined. The durability of the coated substrate in comparison to the uncoated was tested against alkali in accordance with ISO: 10545 (Part 13):1995 standard. FESEM images showed that thin films are dense and homogeneous. Coated substrates after firing results in lustre with high gloss, which increased from 330 to 420 GU as the curing temperature increases compared to that of uncoated one (72 GU). Coated substrate cured at 800°C shows higher mineral hardness (5 Mohs’) compared to uncoated one (4 Mohs’) and films cured at all temperatures showed stain resistance. The experimental results showed that the resistance towards alkali attack increase with increase in curing temperature and alkali resistance of sample cured at 800 °C was found to be superior compared to uncoated substrate. Contact angle of water on coated surface of substrates decreased with increase in temperature. Bacterial reduction percentages of the coated surface was 97% for sample cured at 700°C and it decreased from 97% to 87% as the curing temperature increased to 800 °C when treated with E. coli bacteria.

Thin film devices used as oxygen partial pressure sensors

NASA Technical Reports Server (NTRS)

Canady, K. S.; Wortman, J. J.

1970-01-01

Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

Relation between film thickness and surface doping of MoS2 based field effect transistors

NASA Astrophysics Data System (ADS)

Lockhart de la Rosa, César J.; Arutchelvan, Goutham; Leonhardt, Alessandra; Huyghebaert, Cedric; Radu, Iuliana; Heyns, Marc; De Gendt, Stefan

2018-05-01

Ultra-thin MoS2 film doping through surface functionalization with physically adsorbed species is of great interest due to its ability to dope the film without reduction in the carrier mobility. However, there is a need for understanding how the thickness of the MoS2 film is related to the induced surface doping for improved electrical performance. In this work, we report on the relation of MoS2 film thickness with the doping effect induced by the n-dopant adsorbate poly(vinyl-alcohol). Field effect transistors built using MoS2 films of different thicknesses were electrically characterized, and it was observed that the ION/OFF ratio after doping in thin films is more than four orders of magnitudes greater when compared with thick films. Additionally, a semi-classical model tuned with the experimental devices was used to understand the spatial distribution of charge in the channel and explain the observed behavior. From the simulation results, it was revealed that the two-dimensional carrier density induced by the adsorbate is distributed rather uniformly along the complete channel for thin films (<5.2 nm) contrary to what happens for thicker films.

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

Copper Phthalocyanine Functionalized Single-Walled Carbon Nanotubes: Thin Films for Optical Detection.

PubMed

Banimuslem, Hikmat; Hassan, Aseel; Basova, Tamara; Durmuş, Mahmut; Tuncel, Sinem; Esenpinar, Aliye Asli; Gürek, Ayşe Gül; Ahsen, Vefa

2015-03-01

Thin films of non-covalently hybridized single-walled carbon nanotubes (SWCNT) and tetra-substituted copper phthalocyanine (CuPcR4) molecules have been produced from their solutions in dimethylformamide (DMF). FTIR spectra revealed the 7π-7π interaction between SWCNTs and CuPcR4 molecules. DC conductivity of films of acid-treated SWCNT/CuPcR4 hybrid has increased by more than three orders of.magnitude in comparison with conductivity of CuPcR4 films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements have shown that films obtained from the acid-treated SWCNTs/CuPcR4 hybrids demonstrated more homogenous surface which is ascribed to the highly improved solubility of the hybrid powder in DMF Using total internal reflection ellipsometry spectroscopy (TIRE), thin films of the new hybrid have been examined as an optical sensing membrane for the detection of benzo[a]pyrene in water to demonstrate the sensing properties of the hybrid.

Three-dimensional simulations of thin ferro-fluid films and drops in magnetic fields

NASA Astrophysics Data System (ADS)

Conroy, Devin; Wray, Alex; Matar, Omar

2016-11-01

We consider the interfacial dynamics of a thin, ferrofluidic film flowing down an inclined substrate, under the action of a magnetic field, bounded above by an inviscid gas. The fluid is assumed to be weakly-conducting. Its dynamics are governed by a coupled system of the steady Maxwell's, the Navier-Stokes, and continuity equations. The magnetisation of the film is a function of the magnetic field, and is prescribed by a Langevin function. We make use of a long-wave reduction in order to solve for the dynamics of the pressure, velocity, and magnetic fields inside the film. The potential in the gas phase is solved with the use of Fourier Transforms. Imposition of appropriate interfacial conditions allows for the construction of an evolution equation for the interfacial shape, via use of the kinematic condition, and the magnetic field. We consider the three-dimensional evolution of the film to spawise perturbations by solving the non-linear equations numerically. The constant flux configuration is considered, which corresponds to a thin film and drop flowing down an incline, and a parametric study is performed to understand the effect of a magnetic field on the stability and structure of the formed drops. EPSRC UK platform Grant MACIPh (EP/L020564/1) and programme Grant MEMPHIS (EP/K003976/1).

In situ preparation, electrical and surface analytical characterization of pentacene thin film transistors

PubMed Central

Lassnig, R.; Striedinger, B.; Hollerer, M.; Fian, A.; Stadlober, B.; Winkler, A.

2015-01-01

The fabrication of organic thin film transistors with highly reproducible characteristics presents a very challenging task. We have prepared and analyzed model pentacene thin film transistors under ultra-high vacuum conditions, employing surface analytical tools and methods. Intentionally contaminating the gold contacts and SiO2 channel area with carbon through repeated adsorption, dissociation, and desorption of pentacene proved to be very advantageous in the creation of devices with stable and reproducible parameters. We mainly focused on the device properties, such as mobility and threshold voltage, as a function of film morphology and preparation temperature. At 300 K, pentacene displays Stranski-Krastanov growth, whereas at 200 K fine-grained, layer-like film growth takes place, which predominantly influences the threshold voltage. Temperature dependent mobility measurements demonstrate good agreement with the established multiple trapping and release model, which in turn indicates a predominant concentration of shallow traps in the crystal grains and at the oxide-semiconductor interface. Mobility and threshold voltage measurements as a function of coverage reveal that up to four full monolayers contribute to the overall charge transport. A significant influence on the effective mobility also stems from the access resistance at the gold contact-semiconductor interface, which is again strongly influenced by the temperature dependent, characteristic film growth mode. PMID:25814770

In situ preparation, electrical and surface analytical characterization of pentacene thin film transistors

NASA Astrophysics Data System (ADS)

Lassnig, R.; Striedinger, B.; Hollerer, M.; Fian, A.; Stadlober, B.; Winkler, A.

2014-09-01

The fabrication of organic thin film transistors with highly reproducible characteristics presents a very challenging task. We have prepared and analyzed model pentacene thin film transistors under ultra-high vacuum conditions, employing surface analytical tools and methods. Intentionally contaminating the gold contacts and SiO2 channel area with carbon through repeated adsorption, dissociation, and desorption of pentacene proved to be very advantageous in the creation of devices with stable and reproducible parameters. We mainly focused on the device properties, such as mobility and threshold voltage, as a function of film morphology and preparation temperature. At 300 K, pentacene displays Stranski-Krastanov growth, whereas at 200 K fine-grained, layer-like film growth takes place, which predominantly influences the threshold voltage. Temperature dependent mobility measurements demonstrate good agreement with the established multiple trapping and release model, which in turn indicates a predominant concentration of shallow traps in the crystal grains and at the oxide-semiconductor interface. Mobility and threshold voltage measurements as a function of coverage reveal that up to four full monolayers contribute to the overall charge transport. A significant influence on the effective mobility also stems from the access resistance at the gold contact-semiconductor interface, which is again strongly influenced by the temperature dependent, characteristic film growth mode.

Formation of diamond nanoparticle thin films by electrophoretic deposition

NASA Astrophysics Data System (ADS)

Goto, Yosuke; Ohishi, Fujio; Tanaka, Kuniaki; Usui, Hiroaki

2016-03-01

Thin films of diamond nanoparticles were prepared by electrophoretic deposition (EPD) using 0.5 wt % dispersions in water, ethanol, and 2-propanol. The film growth rate increased with increasing voltage applied to the electrodes. However, an excessive increase in voltage caused the degradation of film morphology. The optimum voltage was 4 V with an electrode separation of 5 mm. The film growth rate was higher in organic solvents than in water. The deposited film had a smooth surface with an average surface roughness comparable to the size of primary particles of the source material. It is notable that the EPD films had a considerably higher physical stability than spin-coated and cast films. The stability was further improved by thermally annealing the films. IR analysis revealed that the diamond nanoparticles have carboxy and amino groups on their surfaces. It is considered that the stability of the EPD films originate from a chemical reaction between these functional groups.

Structural, optical and NO2 gas sensing properties of ZnMgO thin films prepared by the sol gel method

NASA Astrophysics Data System (ADS)

Chebil, W.; Boukadhaba, M. A.; Madhi, I.; Fouzri, A.; Lusson, A.; Vilar, C.; Sallet, V.

2017-01-01

In this present work, ZnO and ZnMgO thin films prepared by a sol-gel process were deposited on glass substrates via spin coating technique. The structural, morphological and optical properties of the obtained films were investigated. X-ray diffraction study revealed that all layers exhibit a hexagonal wurtzite structure without any secondary phase segregation. The atomic force microscopy (AFM) depicts that the grains size of ours samples decreases as magnesium content increases. The absorption spectra obtained on ZnMgO thin films show a band gap tuning from 3.19 to 3.36 eV, which is also consistent with blue shifting of near-band edge PL emission, measured at low temperature. The incorporated amount of magnesium was calculated and confirmed by EDX. The gas sensing performances were tested in air containing NO2 for different operating temperatures. The experimental result exhibited that ZnMgO sensors shows a faster response and recovery time than the ZnO thin films. The resistivity and the sensor response as function of Mg content were also investigated.

Thickness Dependency of Thin Film Samaria Doped Ceria for Oxygen Sensing

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

Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T

High temperature oxygen sensors are widely used for exhaust gas monitoring in automobiles. This particular study explores the use of thin film single crystalline samaria doped ceria as the oxygen sensing material. Desired signal to noise ratio can be achieved in a material system with high conductivity. From previous studies it is established that 6 atomic percent samarium doping is the optimum concentration for thin film samaria doped ceria to achieve high ionic conductivity. In this study, the conductivity of the 6 atomic percent samaria doped ceria thin film is measured as a function of the sensing film thickness. Hysteresismore » and dynamic response of this sensing platform is tested for a range of oxygen pressures from 0.001 Torr to 100 Torr for temperatures above 673 K. An attempt has been made to understand the physics behind the thickness dependent conductivity behavior of this sensing platform by developing a hypothetical operating model and through COMSOL simulations. This study can be used to identify the parameters required to construct a fast, reliable and compact high temperature oxygen sensor.« less

Reversible tuning of magnetocaloric Ni-Mn-Ga-Co films on ferroelectric PMN-PT substrates.

PubMed

Schleicher, Benjamin; Niemann, Robert; Schwabe, Stefan; Hühne, Ruben; Schultz, Ludwig; Nielsch, Kornelius; Fähler, Sebastian

2017-10-31

Tuning functional properties of thin caloric films by mechanical stress is currently of high interest. In particular, a controllable magnetisation or transition temperature is desired for improved usability in magnetocaloric devices. Here, we present results of epitaxial magnetocaloric Ni-Mn-Ga-Co thin films on ferroelectric Pb(Mg 1/3 Nb 2/3 ) 0.72 Ti 0.28 O 3 (PMN-PT) substrates. Utilizing X-ray diffraction measurements, we demonstrate that the strain induced in the substrate by application of an electric field can be transferred to the thin film, resulting in a change of the lattice parameters. We examined the consequences of this strain on the magnetic properties of the thin film by temperature- and electric field-dependent measurements. We did not observe a change of martensitic transformation temperature but a reversible change of magnetisation within the austenitic state, which we attribute to the intrinsic magnetic instability of this metamagnetic Heusler alloy. We demonstrate an electric field-controlled entropy change of about 31 % of the magnetocaloric effect - without any hysteresis.

Formation of Indium-Doped Zinc Oxide Thin Films Using Ultrasonic Spray Pyrolysis: The Importance of the Water Content in the Aerosol Solution and the Substrate Temperature for Enhancing Electrical Transport.

PubMed

Biswal, Rajesh; Castañeda, Luis; Moctezuma, Rosario; Vega-Pérez, Jaime; Olvera, María De La Luz; Maldonado, Arturo

2012-03-12

Indium doped zinc oxide [ZnO:In] thin films have been deposited at 430°C on soda-lime glass substrates by the chemical spray technique, starting from zinc acetate and indium acetate. Pulverization of the solution was done by ultrasonic excitation. The variations in the electrical, structural, optical, and morphological characteristics of ZnO:In thin films, as a function of both the water content in the starting solution and the substrate temperature, were studied. The electrical resistivity of ZnO:In thin films is not significantly affected with the increase in the water content, up to 200 mL/L; further increase in water content causes an increase in the resistivity of the films. All films show a polycrystalline character, fitting well with the hexagonal ZnO wurtzite-type structure. No preferential growth in samples deposited with the lowest water content was observed, whereas an increase in water content gave rise to a (002) growth. The surface morphology of the films shows a consistency with structure results, as non-geometrical shaped round grains were observed in the case of films deposited with the lowest water content, whereas hexagonal slices, with a wide size distribution were observed in the other cases. In addition, films deposited with the highest water content show a narrow size distribution.

Electrical conduction mechanism and phase transition studies using dielectric properties and Raman spectroscopy in ferroelectric Pb0.76Ca0.24TiO3 thin films

NASA Astrophysics Data System (ADS)

Pontes, F. M.; Pontes, D. S. L.; Leite, E. R.; Longo, E.; Chiquito, A. J.; Pizani, P. S.; Varela, J. A.

2003-12-01

We have studied the phase transition behavior of Pb0.76Ca0.24TiO3 thin films using Raman scattering and dielectric measurement techniques. We also have studied the leakage current conduction mechanism as a function of temperature for these thin films on platinized silicon substrates. A Pb0.76Ca0.24TiO3 thin film was prepared using a soft chemical process, called the polymeric precursor method. The results showed that the dependence of the dielectric constant upon the frequency does not reveal any relaxor behavior. However, a diffuse character-type phase transition was observed upon transformation from a cubic paraelectric phase to a tetragonal ferroelectric phase. The temperature dependency of Raman scattering spectra was investigated through the ferroelectric phase transition. The soft mode showed a marked dependence on temperature and its disappearance at about 598 K. On the other hand, Raman modes persist above the tetragonal to cubic phase transition temperature, although all optical modes should be Raman inactive above the phase transition temperature. The origin of these modes must be interpreted in terms of a local breakdown of cubic symmetry by some kind of disorder. The lack of a well-defined transition temperature suggested a diffuse-type phase transition. This result corroborate the dielectric constant versus temperature data, which showed a broad ferroelectric phase transition in the thin film. The leakage current density of the PCT24 thin film was studied at elevated temperatures, and the data were well fitted by the Schottky emission model. The Schottky barrier height of the PCT24 thin film was estimated to be 1.49 eV.

Characterization of thin solid films and surfaces by infrared spectroscopy

NASA Astrophysics Data System (ADS)

Grosse, Peter

Thin solid films and surfaces are characterized by means of IR-spectroscopy. Properties under consideration are geometric structures of layers and stacks of layers, chemical composition and incorporation of impurities, and parameters of free electrons and holes. The method is based on reflectance and transmittance measurements, in particular with polarized light at oblique incidence. Thus the interaction of the electromagnetic waves with thin films is enhanced and two independent data sets for s- and p-polarization are available. The interpretation of the measured spectra is carried out by a fit procedure, simulating the observed spectra by an adequate model. For fitting we use an ansatz of a dielectric function which is a sum of susceptibilities taking into account the contributions of valence electrons, optical phonons, free carriers, and of impurities. As examples for the method we discuss the following systems: insulating and percolating films of Ag deposited on glass, epitactic III-V-heterostructures, oxide films as used for MOS-structures, diffusion and implantation profiles, and adsorbates on metals. All examples are relevant for application in technology, as microelectronics, thin film technology, catalysis e.g. The reliability of the non-destructive IR-method is compared with other relevant analytic methods as SIMS, RBS, and AES.

Optical and structural properties of Al-doped ZnO thin films by sol gel process.

PubMed

Jun, Min-Chul; Koh, Jung-Hyuk

2013-05-01

Transparent conducting oxide (TCO) materials with high transmittance and good electrical conductivity have been attracted much attention due to the development of electronic display and devices such as organic light emitting diodes (OLEDs), and dye-sensitized solar cells (DSSCs). Aluminum doped zinc oxide thin films (AZO) have been well known for their use as TCO materials due to its stability, cost-effectiveness, good optical transmittance and electrical properties. Especially, AZO thin film, which have low resistivity of 2-4 x 10(-4) omega x cm which is similar to that of ITO films with wide band gap semiconductors. The AZO thin films were deposited on glass substrates by sol-gel spin-coating process. As a starting material, zinc acetate dihydrate (Zn(CH3COO)2 x 2H2O) and aluminum chloride hexahydrate (AlCl3 6H2O) were used. 2-methoxyethanol and monoethanolamine (MEA) were used as solvent and stabilizer, respectively. After deposited, the films were preheated at 300 degrees C on a hotplate and post-heated at 650 degrees C for 1.5 hrs in the furnace. We have studied the structural and optical properties as a function of Al concentration (0-2.5 mol.%).

Surface roughening and scaling behavior of vacuum-deposited SnCl{sub 2}Pc organic thin films on different substrates

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

Obaidulla, Sk. Md.; Giri, P. K., E-mail: giri@iitg.ernet.in; Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039

2015-11-30

The evolution of surface morphology and scaling behavior of tin (IV) phthalocyanine dichloride (SnCl{sub 2}Pc) thin films grown on Si(100) and glass substrates have been studied using atomic force microscopy (AFM) and height-height correlation function analysis. X-ray diffraction measurement confirms the crystalline nature of the SnCl{sub 2}Pc thin film on glass substrate, while no crystallographic ordering is present for the film grown on Si substrate. The growth exponent β is found to be much larger for the film on glass substrate (0.48 ± 0.07) as compared to that on Si substrate (0.21 ± 0.08), which may be due to the high step-edge barrier, so-calledmore » Ehrlich-Schwöbel barrier, resulting in the upward dominant growth on glass substrate. From the 2D fast Fourier transform of AFM images and derived scaling exponents, we conclude that the surface evolution follows a mound like growth. These results imply the superiority of glass substrate over the Si substrate for the growth of device quality SnCl{sub 2}Pc thin film.« less

In situ measurements of thin films in bovine serum lubricated contacts using optical interferometry.

PubMed

Vrbka, Martin; Křupka, Ivan; Hartl, Martin; Návrat, Tomáš; Gallo, Jiří; Galandáková, Adéla

2014-02-01

The aim of this study is to consider the relevance of in situ measurements of bovine serum film thickness in the optical test device that could be related to the function of the artificial hip joint. It is mainly focussed on the effect of the hydrophobicity or hydrophilicity of the transparent surface and the effect of its geometry. Film thickness measurements were performed using ball-on-disc and lens-on-disc configurations of optical test device as a function of time. Chromatic interferograms were recorded with a high-speed complementary metal-oxide semiconductor digital camera and evaluated with thin film colorimetric interferometry. It was clarified that a chromium layer covering the glass disc has a hydrophobic behaviour which supports the adsorption of proteins contained in the bovine serum solution, thereby a thicker lubricating film is formed. On the contrary, the protein film formation was not observed when the disc was covered with a silica layer having a hydrophilic behaviour. In this case, a very thin lubricating film was formed only due to the hydrodynamic effect. Metal and ceramic balls have no substantial effect on lubricant film formation although their contact surfaces have relatively different wettability. It was confirmed that conformity of contacting surfaces and kinematic conditions has fundamental effect on bovine serum film formation. In the ball-on-disc configuration, the lubricant film is formed predominantly due to protein aggregations, which pass through the contact zone and increase the film thickness. In the more conformal ball-on-lens configuration, the lubricant film is formed predominantly due to hydrodynamic effect, thereby the film thickness is kept constant during measurement.

Ovonic type switching in tin selenide thin films

NASA Technical Reports Server (NTRS)

Baxter, C. R.; Mclennan, W. D.

1975-01-01

Amorphous tin selenide thin films which possess Ovonic type switching properties are fabricated using vacuum deposition techniques. The devices are fabricated in a planar configuration and consist of amorphous tin selenide deposited over silver contacts. Results obtained indicate that Ovonic type memory switching does occur in these films with the energy density required for switching from a high impedance to a low impedance state being dependent on the spacing between the electrodes of the device. There is also a strong implication that the switching is a function of the magnitude of the applied voltage pulse.

Electrical properties of CZTS thin films

NASA Astrophysics Data System (ADS)

Rao, M. C.; Kumar, M. Seshu; Lakshmi, K.; Rao, K. Koteswara; Parimala, M. P. D.; Basha, S. K. Shahenoor

2018-05-01

CZTS (Cu2ZnSnS4) thin films have been coated on to FTO and MO glass substrates by single step electro deposition process. Different characterization techniques were performed on to the prepared samples such as DSC and Raman studies. The Phase transition and weight loss of the precursors can be measured by DSC analysis. Raman spectrum is used to identify the functional groups and chemical structure involved in the materials. Electrical measurements confirm the nature of the film and also depend on the charge concentration present in the samples.

Nanomechanical and nanotribological properties of Nb substituted TiN thin films

NASA Astrophysics Data System (ADS)

Krishna, M. Ghanashyam; Vasu, K.; Padmanabhan, K. A.

2012-06-01

Nanomechanical and nanotribological properties of Ti1-xNbxN (0≤x≤1) thin films were investigated as a function x. The films were deposited onto polycrystalline nuclear grade 316LN stainless steel (SS) substrate by radio frequency magnetron sputtering in 100% N2 plasma. The hardness and Young's modulus increased while the friction coefficient and wear volume decreased with increasing Nb substitution. The highest hardness achieved was 31GPa for x=0.77. At the same Nb concentration, the friction coefficient was 0.15 and the elastic recovery was 60%.

Topological, chemical and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

NASA Astrophysics Data System (ADS)

Gnapareddy, Bramaramba; Dugasani, Sreekantha Reddy; Son, Junyoung; Park, Sung Ha

2018-02-01

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films were constructed using substrate-assisted growth and drop-casting methods, respectively, and their topological, chemical and electro-optical characteristics were evaluated. The critical doping concentrations of RF ([RF]C, approx. 5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analysing the atomic force microscopy images for DX-DNA and current, absorbance and photoluminescence (PL) for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, using the Fourier transform infrared spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA and PL to analyse the energy transfer between the RF and DNA. The current and UV absorption band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. By contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorption behaviour as a function of the varying [RF]. Owing to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices.

Topological, chemical and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

PubMed Central

Gnapareddy, Bramaramba; Son, Junyoung

2018-01-01

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films were constructed using substrate-assisted growth and drop-casting methods, respectively, and their topological, chemical and electro-optical characteristics were evaluated. The critical doping concentrations of RF ([RF]C, approx. 5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analysing the atomic force microscopy images for DX-DNA and current, absorbance and photoluminescence (PL) for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, using the Fourier transform infrared spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA and PL to analyse the energy transfer between the RF and DNA. The current and UV absorption band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. By contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorption behaviour as a function of the varying [RF]. Owing to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices. PMID:29515837

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

NASA Astrophysics Data System (ADS)

Shepley, Philippa M.; Tunnicliffe, Harry; Shahbazi, Kowsar; Burnell, Gavin; Moore, Thomas A.

2018-04-01

We study the magnetic properties of perpendicularly magnetized Pt/Co/Ir thin films and investigate the domain-wall creep method of determining the interfacial Dzyaloshinskii-Moriya (DM) interaction in ultrathin films. Measurements of the Co layer thickness dependence of saturation magnetization, perpendicular magnetic anisotropy, and symmetric and antisymmetric (i.e., DM) exchange energies in Pt/Co/Ir thin films have been made to determine the relationship between these properties. We discuss the measurement of the DM interaction by the expansion of a reverse domain in the domain-wall creep regime. We show how the creep parameters behave as a function of in-plane bias field and discuss the effects of domain-wall roughness on the measurement of the DM interaction by domain expansion. Whereas modifications to the creep law with DM field and in-plane bias fields have taken into account changes in the energy barrier scaling parameter α , we find that both α and the velocity scaling parameter v0 change as a function of in-plane bias field.

Fabrication of ZnO Thin Films by Sol-Gel Spin Coating and Their UV and White-Light Emission Properties

NASA Astrophysics Data System (ADS)

Kumar, Mirgender; Dubey, Sarvesh; Rajendar, Vanga; Park, Si-Hyun

2017-10-01

ZnO thin films have been fabricated by the sol-gel spin-coating technique and annealed under different conditions, and their ultraviolet (UV) and white-light emission properties investigated. Different ambient conditions including oxygen, nitrogen, zinc-rich nitrogen, and vacuum were used to tune the main properties of the ZnO thin films. The resistivity varied from the conductive to semi-insulating regime, and the luminescence emission from fairly intense UV to polychromatic. The emission intensity was also found to be a function of the annealing conditions. Possible routes to compensate the loss of emission characteristics are discussed. X-ray photoelectron spectroscopy (XPS) analysis was carried out to detect the chemical states of the zinc/oxygen species. The changes in the electrical and emission properties are explained based on annihilation/formation of inherent donor/acceptor-type defects. Such ZnO thin films could have potential applications in solid-state lighting.

Electrochemical Properties of RuO2 Electrodes as a Function of Thin Film Thickness

NASA Astrophysics Data System (ADS)

Li, Xiang; Xiong, Jian; Luo, Yuan; Luo, Yongmei

2018-01-01

A thin film RuO2 electrode was prepared by spin coating thermal decomposition methods. Precursor containing RuCl3·nH2O and isopropyl alcohol was coated on tantalum substrate and annealed at 250-260°C for 3 h to form a thin film RuO2 electrode of about 2.5 μm, 5.6 μm, 11.4 μm, and 14.5 μm in thickness. X-ray diffraction revealed that peak intensities of those electrodes were similar and close to each other. Scanning electron microscopy showed that thin film of 5.6 μm in thickness was dense and free of cracks. Electrochemical performances of electrodes were examined by cyclic voltammetry, galvanostatic charge/discharge as well as equivalent series resistance. The highest specific capacitance value of 725 F g-1 was registered for the electrode of 5.6 μm in thickness with good constant current charge/discharge and equivalent series resistance of 0.36 Ω as well as cyclic stability.

Synthesis and characterization of binary ZnO-SnO2 (ZTO) thin films by e-beam evaporation technique

NASA Astrophysics Data System (ADS)

Bibi, Shagufta; Shah, A.; Mahmood, Arshad; Ali, Zahid; Raza, Qaisar; Aziz, Uzma; Haneef; Waheed, Abdul; Shah, Ziaullah

2018-04-01

The binary ZnO-SnO2 (ZTO) thin films with varying SnO2 concentrations (5, 10, 15, and 20 wt%) were grown on glass substrate by e-beam evaporation technique. The prepared ZTO films were annealed at 400 °C in air. These films were then characterized to investigate their structural, optical, and electrical properties as a function of SnO2 concentration. XRD analysis reveals that the crystallinity of the film decreases with the addition of SnO2 and it transforms to an amorphous structure at a composition of 40% SnO2 and 60% ZnO. Morphology of the films was examined by atomic force microscopy which points out that surface roughness of the films decreases with the increasing of SnO2 in the film. Optical properties such as optical transparency, band-gap energy, and optical constants of these films were examined by spectrophotometer and spectroscopic Ellipsometer. It was observed that the average optical transmission of mixed films improves with incorporation of SnO2. In addition, the band-gap energy of the films was determined to be in the range of 3.37-3.7 eV. Furthermore, it was found that the optical constants (n and k) decrease with the addition of SnO2. Similarly, it is observed that the electrical resistivity increases nonlinearly with the increase in SnO2 in ZnO-SnO2 thin films. However, it is noteworthy that the highest figure of merit (FOM) value, i.e., 55.87 × 10-5 Ω-1, is obtained for ZnO-SnO2 (ZTO) thin film with 40 wt% of SnO2 composition. Here, we suggest that ZnO-SnO2 (ZTO) thin film with composition of 60:40 wt% can be used as an efficient TCO film due to the improved transmission, and reduced RMS value and highest FOM value.

Sputter deposition of PZT piezoelectric films on thin glass substrates for adjustable x-ray optics.

PubMed

Wilke, Rudeger H T; Johnson-Wilke, Raegan L; Cotroneo, Vincenzo; Davis, William N; Reid, Paul B; Schwartz, Daniel A; Trolier-McKinstry, Susan

2013-05-10

Piezoelectric PbZr(0.52)Ti(0.48)O(3) (PZT) thin films deposited on thin glass substrates have been proposed for adjustable optics in future x-ray telescopes. The light weight of these x-ray optics enables large collecting areas, while the capability to correct mirror figure errors with the PZT thin film will allow much higher imaging resolution than possible with conventional lightweight optics. However, the low strain temperature and flexible nature of the thin glass complicate the use of chemical-solution deposition due to warping of the substrate at typical crystallization temperatures for the PZT. RF magnetron sputtering enabled preparation of PZT films with thicknesses up to 3 μm on Schott D263 glass substrates with much less deformation. X-ray diffraction analysis indicated that the films crystallized with the perovskite phase and showed no indication of secondary phases. Films with 1 cm(2) electrodes exhibited relative permittivity values near 1100 and loss tangents below 0.05. In addition, the remanent polarization was 26 μC/cm(2) with coercive fields of 33 kV/cm. The transverse piezoelectric coefficient was as high as -6.1±0.6 C/m(2). To assess influence functions for the x-ray optics application, the piezoelectrically induced deflection of individual cells was measured and compared with finite-element-analysis calculations. The good agreement between the results suggests that actuation of PZT thin films can control mirror figure errors to a precision of about 5 nm, allowing sub-arcsecond imaging.

Electronic and Optical Properties of Atomic Layer-Deposited ZnO and TiO2

NASA Astrophysics Data System (ADS)

Ates, H.; Bolat, S.; Oruc, F.; Okyay, A. K.

2018-05-01

Metal oxides are attractive for thin film optoelectronic applications. Due to their wide energy bandgaps, ZnO and TiO2 are being investigated by many researchers. Here, we have studied the electrical and optical properties of ZnO and TiO2 as a function of deposition and post-annealing conditions. Atomic layer deposition (ALD) is a novel thin film deposition technique where the growth conditions can be controlled down to atomic precision. ALD-grown ZnO films are shown to exhibit tunable optical absorption properties in the visible and infrared region. Furthermore, the growth temperature and post-annealing conditions of ZnO and TiO2 affect the electrical properties which are investigated using ALD-grown metal oxide as the electron transport channel on thin film field-effect devices.

Thin-film cadmium telluride photovoltaic cells

NASA Astrophysics Data System (ADS)

Compaan, A. D.; Bohn, R. G.

1994-09-01

This report describes work to develop and optimize radio-frequency (RF) sputtering for the deposition of thin films of cadmium telluride (CdTe) and related semiconductors for thin-film solar cells. Pulsed laser physical vapor deposition was also used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. The sputtering work utilized a 2-in diameter planar magnetron sputter gun. The film growth rate by RF sputtering was studied as a function of substrate temperature, gas pressure, and RF power. Complete solar cells were fabricated on tin-oxide-coated soda-lime glass substrates. Currently, work is being done to improve the open-circuit voltage by varying the CdTe-based absorber layer, and to improve the short-circuit current by modifying the CdS window layer.

Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

NASA Technical Reports Server (NTRS)

Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

1991-01-01

Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

Structural and optical properties of electron beam evaporated yttria stabilized zirconia thin films

NASA Astrophysics Data System (ADS)

Kirubaharan, A. Kamalan; Kuppusami, P.; Singh, Akash; Dharini, T.; Ramachandran, D.; Mohandas, E.

2015-06-01

Yttria stabilized zirconia (10 mole % Y2O3) thin films were deposited on quartz substrates using electron beam physical vapor deposition at the substrate temperatures in the range 300 - 973 K. XRD analysis showed cubic crystalline phase of YSZ films with preferred orientation along (111). The surface roughness was found to increase with the increase of deposition temperatures. The optical band gap of ˜5.7 eV was calculated from transmittance curves. The variation in the optical properties is correlated with the changes in the microstructural features of the films prepared as a function of substrate temperature.

Scanning thermal probe microscope method for the determination of thermal diffusivity of nanocomposite thin films

NASA Astrophysics Data System (ADS)

Varandani, Deepak; Agarwal, Khushboo; Brugger, Juergen; Mehta, Bodh Raj

2016-08-01

A commercial scanning thermal microscope has been upgraded to facilitate its use in estimating the radial thermal diffusivity of thin films close to room temperature. The modified setup includes a microcontroller driven microhotplate coupled with a Bluetooth module for wireless control. The microcontroller board (Arduino Leonardo) is used to generate a bias of suitable voltage amplitude and pulse duration which is applied across the microhotplate contact pads. A corresponding heat pulse from the Pt heating element (1 mm2) embedded within the microhotplate is delivered to the lower surface of the thin film (25 mm2) deposited over it. The large difference in the dimensions of the heating source and the thin film surface causes heat to flow radially outwards on the top surface of the latter. The decay of this radial heat wave as it flows outwards is recorded by the scanning thermal microscope in terms of temperature-time (T-t) profiles at varying positions around the central heating zone. A fitting procedure is suggested to extract the thermal diffusivity value from the array of T-t profiles. The efficacy of the above setup has been established by evaluating the thermal diffusivities of Bi2Te3 and Bi2Te3:Si thin film samples. Further, with only minor alterations in design the capabilities of the above setup can be extended to estimate the axial thermal diffusivity and specific heat of thin films, as a function of temperature.

Intrinsic hydrophilic nature of epitaxial thin-film of rare-earth oxide grown by pulsed laser deposition.

PubMed

Prakash, Saurav; Ghosh, Siddhartha; Patra, Abhijeet; Annamalai, Meenakshi; Motapothula, Mallikarjuna Rao; Sarkar, Soumya; Tan, Sherman J R; Zhunan, Jia; Loh, Kian Ping; Venkatesan, T

2018-02-15

Herein, we report a systematic study of water contact angle (WCA) of rare-earth oxide thin-films. These ultra-smooth and epitaxial thin-films were grown using pulsed laser deposition and then characterized using X-Ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and atomic force microscopy (AFM). Through both the traditional sessile drop and the novel f-d method, we found that the films were intrinsically hydrophilic (WCA < 10°) just after being removed from the growth chamber, but their WCAs evolved with an exposure to the atmosphere with time to reach their eventual saturation values near 90° (but always stay 'technically' hydrophilic). X-Ray photoelectron spectroscopy analysis was used to further investigate qualitatively the nature of hydrocarbon contamination on the freshly prepared as well as the environmentally exposed REO thin-film samples as a function of the exposure time after they were removed from the deposition chamber. A clear correlation between the carbon coverage of the surface and the increase in WCA was observed for all of the rare-earth films, indicating the extrinsic nature of the surface wetting properties of these films and having no relation to the electronic configuration of the rare-earth atoms as proposed by Azimi et al.

Analysis of the Sensing Properties of a Highly Stable and Reproducible Ozone Gas Sensor Based on Amorphous In-Ga-Zn-O Thin Film.

PubMed

Wu, Chiu-Hsien; Jiang, Guo-Jhen; Chang, Kai-Wei; Deng, Zu-Yin; Li, Yu-Ning; Chen, Kuen-Lin; Jeng, Chien-Chung

2018-01-09

In this study, the sensing properties of an amorphous indium gallium zinc oxide (a-IGZO) thin film at ozone concentrations from 500 to 5 ppm were investigated. The a-IGZO thin film showed very good reproducibility and stability over three test cycles. The ozone concentration of 60-70 ppb also showed a good response. The resistance change (Δ R ) and sensitivity ( S ) were linearly dependent on the ozone concentration. The response time ( T 90-res ), recovery time ( T 90-rec ), and time constant (τ) showed first-order exponential decay with increasing ozone concentration. The resistance-time curve shows that the maximum resistance change rate (dRg/dt) is proportional to the ozone concentration during the adsorption. The results also show that it is better to sense rapidly and stably at a low ozone concentration using a high light intensity. The ozone concentration can be derived from the resistance change, sensitivity, response time, time constant (τ), and first derivative function of resistance. However, the time of the first derivative function of resistance is shorter than other parameters. The results show that a-IGZO thin films and the first-order differentiation method are promising candidates for use as ozone sensors for practical applications.

Analysis of the Sensing Properties of a Highly Stable and Reproducible Ozone Gas Sensor Based on Amorphous In-Ga-Zn-O Thin Film

PubMed Central

Wu, Chiu-Hsien; Jiang, Guo-Jhen; Chang, Kai-Wei; Deng, Zu-Yin; Li, Yu-Ning; Chen, Kuen-Lin; Jeng, Chien-Chung

2018-01-01

In this study, the sensing properties of an amorphous indium gallium zinc oxide (a-IGZO) thin film at ozone concentrations from 500 to 5 ppm were investigated. The a-IGZO thin film showed very good reproducibility and stability over three test cycles. The ozone concentration of 60–70 ppb also showed a good response. The resistance change (ΔR) and sensitivity (S) were linearly dependent on the ozone concentration. The response time (T90-res), recovery time (T90-rec), and time constant (τ) showed first-order exponential decay with increasing ozone concentration. The resistance–time curve shows that the maximum resistance change rate (dRg/dt) is proportional to the ozone concentration during the adsorption. The results also show that it is better to sense rapidly and stably at a low ozone concentration using a high light intensity. The ozone concentration can be derived from the resistance change, sensitivity, response time, time constant (τ), and first derivative function of resistance. However, the time of the first derivative function of resistance is shorter than other parameters. The results show that a-IGZO thin films and the first-order differentiation method are promising candidates for use as ozone sensors for practical applications. PMID:29315218

Anisotropic imprint of amorphization and phase separation in manganite thin films via laser interference irradiation.

PubMed

Ding, Junfeng; Lin, Zhipeng; Wu, Jianchun; Dong, Zhili; Wu, Tom

2015-02-04

Materials with mesoscopic structural and electronic phase separation, either inherent from synthesis or created via external means, are known to exhibit functionalities absent in the homogeneous counterparts. One of the most notable examples is the colossal magnetoresistance discovered in mixed-valence manganites, where the coexistence of nano- to micrometer-sized phase-separated domains dictates the magnetotransport. However, it remains challenging to pattern and process such materials into predesigned structures and devices. In this work, a direct laser interference irradiation (LII) method is employed to produce periodic stripes in thin films of a prototypical phase-separated manganite Pr0.65 (Ca0.75 Sr0.25 )0.35 MnO3 (PCSMO). LII induces selective structural amorphization within the crystalline PCSMO matrix, forming arrays with dimensions commensurate with the laser wavelength. Furthermore, because the length scale of LII modification is compatible to that of phase separation in PCSMO, three orders of magnitude of increase in magnetoresistance and significant in-plane transport anisotropy are observed in treated PCSMO thin films. Our results show that LII is a rapid, cost-effective and contamination-free technique to tailor and improve the physical properties of manganite thin films, and it is promising to be generalized to other functional materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100)

NASA Astrophysics Data System (ADS)

Al-Mahboob, Abdullah; Sadowski, Jerzy T.; Vescovo, Elio

2013-03-01

Metal phthalocyanines are attracting significant attention, owing to their potential for applications in chemical sensors, solar cells and organic magnets. As the electronic properties of molecular films are determined by their crystallinity and molecular packing, the optimization of film quality is important for improving the performance of organic devices. Here, we present the results of in situ low-energy electron microscopy / photoemission electron microscopy (LEEM/PEEM) studies of incorporation-limited growth of manganese-phthalocyanine (MnPc) on Ag(100) surfaces. MnPc thin films were grown on both, bulk Ag(100) surface and thin Ag(100)/Fe(100) films, where substrate spin-polarized electronic states can be modified through tuning the thickness of the Ag film. We also discuss the electronic structure and magnetic ordering in MnPc thin films, investigated by angle- and spin-resolved photoemission spectroscopy. Research carried out at the Center for Functional Nanomaterials and National Synchrotron Light Source, Brookhaven National Laboratory, which are supported by the U.S. Dept. of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

Deposition of Nanostructured CdS Thin Films by Thermal Evaporation Method: Effect of Substrate Temperature

PubMed Central

Memarian, Nafiseh; Rozati, Seyeed Mohammad; Concina, Isabella

2017-01-01

Nanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10−5 Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11–2.2 × 104 Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application. PMID:28773133

Controlling plasmonic properties of epitaxial thin films of indium tin oxide in the near-infrared region

NASA Astrophysics Data System (ADS)

Kamakura, R.; Fujita, K.; Murai, S.; Tanaka, K.

2015-06-01

Epitaxial thin films of indium tin oxide (ITO) were grown on yttria-stabilized zirconia single-crystal substrates by using a pulsed laser deposition to examine their plasmonic properties. The dielectric function of ITO was characterized by spectroscopic ellipsometry. Through the concentration of SnO2 in the target, the carrier concentration in the films was modified, which directly leads to the tuning of the dielectric function in the near-infrared region. Variable-angle reflectance spectroscopy in the Kretschmann geometry shows the dip in the reflection spectrum of p-polarized light corresponding to the excitation of surface plasmon polaritions (SPPs) in the near-infrared region. The excitation wavelength of the SPPs was shifted with changing the dielectric functions of ITO, which is reproduced by the calculation using transfer matrix method.

[Modification and luminescence properties of transparent Lu2SiO5 : Ce3+ thin-film phosphors].

PubMed

Fan, Yang-Yang; Liu, Xiao-Lin; Gu, Mu; Ni, Chen; Huang, Shi-Ming; Liu, Bo

2011-02-01

To achieve high-spatial-resolution for X-ray imaging and flat panel display, transparent thin-film phosphors have been attracted much attention in recent years. In comparison with conventional powder phosphors, the transparent thin-film phosphors have some outstanding advantages such as high contrast and resolution, superior thermal conductivity and better adhesion. Cerium-doped lutetium oxyorthosilicate Lu2 SiO5 (LSO) is one promising candidate due to its high density (7.4 g x cm(-3)), high light yield (27 300 photons x MeV(-1)), short decay time (40 ns), and excellent chemical stability. The sol-gel method is one of the most important techniques for deposition of functional thin films, because it possesses a number of advantages over conventional film formation techniques, such as low processing temperature, easy coating of large surfaces, homogenous multicomponent films, and cheap equipments. In X-ray imaging application, the thickness of the thin-film phosphor is the most important factor, which can increase X-ray absorption of the film and then strengthen its luminescence intensity. In the present work, transparent LSO : Ce film was successfully prepared using sol-gel method and spin-coating technique by using inorganic salts as raw materials, 2-methoxyethanol as solvent, and poly (ethylene glycol) (PEG) as modifier without inert atmosphere. The effect of PEG on the luminescence properties of the film was investigated in detail. The results indicated that PEG200 played an important role in the formation of LSO : Ce film, improving its quality and luminescent intensity. The film thickness of 0.9 microm was achieved after 5 times of coating. The luminescence properties of the film were studied. Their performances were good, which implied that the film would have promising applications in high-spatial-resolution X-ray imaging and flat panel display devices.

Reactive thin polymer films as platforms for the immobilization of biomolecules.

PubMed

Feng, Chuan Liang; Zhang, Zhihong; Förch, Renate; Knoll, Wolfgang; Vancso, G Julius; Schönherr, Holger

2005-01-01

Spin-coated thin films of poly(N-hydroxysuccinimidyl methacrylate) (PNHSMA) on oxidized silicon and gold surfaces were investigated as reactive layers for obtaining platforms for biomolecule immobilization with high molecular loading. The surface reactivity of PNHSMA films in coupling reactions with various primary amines, including amine-terminated poly(ethylene glycol) (PEG-NH2) and fluoresceinamine, was determined by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), fluorescence microscopy, and ellipsometry measurements, respectively. The rate constants of PEG-NH2 attachment on the PNHSMA films were found to be significantly increased compared to the coupling on self-assembled monolayers (SAMs) of 11,11'-dithiobis(N-hydroxysuccinimidylundecanoate) (NHS-C10) on gold under the same conditions. More significantly, the PEG loading observed was about 3 times higher for the polymer thin films. These data indicate that the coupling reactions are not limited to the very surface of the polymer films, but proceed into the near-surface regions of the films. PNHSMA films were shown to be stable in contact with aqueous buffer; the swelling analysis, as performed by atomic force microscopy (AFM), indicated a film thickness independent swelling of approximately 2 nm. An increased loading was also observed by surface plasmon resonance for the covalent immobilization of amino-functionalized probe DNA. Hybridization of fluorescently labeled target DNA was successfully detected by fluorescence microscopy and surface plasmon resonance enhanced fluorescence spectroscopy (SPFS), thereby demonstrating that thin films of PNHSMA comprise an attractive and simple platform for the immobilization of biomolecules with high densities.

Spin-waves in thin films with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Diep, H. T.; El Hog, Sahbi; Puszkarski, Henryk

2018-05-01

Using the Green's function method, we calculate the spin-wave (SW) spectrum in a thin film with quantum Heisenberg spins interacting with each other via an exchange interaction J and a Dzyaloshinskii-Moriya interaction of magnitude D. Due to the competition between J and D, the ground state is non collinear. We show that for large D, the first mode in the SW spectrum is proportional to the in plane wave-vector k at the limit k tending to zero. For small D, it is proportional to k2. We show that the surface modes may occur depending on the surface exchange interaction. We calculate the layer magnetizations at temperature T and the transition temperature as a function of the film thickness.

Flexible pressure sensor based on graphene aerogel microstructures functionalized with CdS nanocrystalline thin film

NASA Astrophysics Data System (ADS)

Plesco, Irina; Dragoman, Mircea; Strobel, Julian; Ghimpu, Lidia; Schütt, Fabian; Dinescu, Adrian; Ursaki, Veaceslav; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

2018-05-01

In this paper, we report on functionalization of graphene aerogel with a CdS thin film deposited by magnetron sputtering and on the development of flexible pressure sensors based on ultra-lightweight CdS-aerogel nanocomposite. Analysis by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis disclose the uniform deposition of nanocrystalline CdS films with quasi-stoichiometric composition. The piezoresistive response of the aforementioned nanocomposite in the pressure range from 1 to 5 atm is found to be more than one order of magnitude higher than that inherent to suspended graphene membranes, leading to an average sensitivity as high as 3.2 × 10-4 kPa-1.

Acridine orange as a biosensitive photovoltaic material

NASA Astrophysics Data System (ADS)

Sharifi, Faranak; Bauld, Reg; Fanchini, Giovanni

2013-10-01

Acridine orange (AO), a biosensitive molecule that is customarily used for labeling nucleic acids including DNA and RNA, is here investigated as a cost effective, water soluble, and photoactive material for the fabrication of potentially biosensitive organic photovoltaics. The electronic energy levels of AO are determined using Kelvin Probe Force Microscopy (KPFM) and UV-Visible spectroscopy. The effect of anticrystallization agents, as well as low-temperature annealing, on the work function of AO is investigated: amorphous AO films are shown to possess a significantly higher work function than microcrystalline AO films and the work function also increases by annealing. Photo-induced processes in AO films are investigated by considering the changes of the KPFM signal under illumination. We demonstrate that acridine orange is able to photogenerate electron-hole pairs at rates comparable to the most commonly used solar-grade photovoltaic materials, including polythiophenes. In addition, the effect of the morphology of different types of AO thin films spun from different solvents is studied in bilayer photovoltaic devices fabricated from stacks of AO and phenyl-C61-butyric acid methyl ester thin films.

Optimization of high quality Cu2ZnSnS4 thin film by low cost and environment friendly sol-gel technique for thin film solar cells applications

NASA Astrophysics Data System (ADS)

Chaudhari, J. J.; Joshi, U. S.

2018-05-01

In this study kesterite Cu2ZnSnS4 (CZTS) thin films suitable for absorber layer in thin film solar cells (TFSCs) were successfully fabricated on glass substrate by sol-gel method. The effects of complexing agent on formation of CZTS thin films have been investigated. X-ray diffraction (XRD) analysis confirms formation of polycrystalline CZTS thin films with single phase kesterite structure. XRD and Raman spectroscopy analysis of CZTS thin films with optimized concentration of complexing agent confirmed formation of kesterite phase in CZTS thin films. The direct optical band gap energy of CZTS thin films is found to decrease from 1.82 to 1.50 eV with increase of concentration of complexing agent triethanolamine. Morphological analysis of CZTS thin films shows smooth, uniform and densely packed CZTS grains and increase in the grain size with increase of concentration of complexing agent. Hall measurements revealed that concentration of charge carrier increases and resistivity decreases in CZTS thin films as amount of complexing agent increases.

Two-dimensional models for the optical response of thin films

NASA Astrophysics Data System (ADS)

Li, Yilei; Heinz, Tony F.

2018-04-01

In this work, we present a systematic study of 2D optical models for the response of thin layers of material under excitation by normally incident light. The treatment, within the framework of classical optics, analyzes a thin film supported by a semi-infinite substrate, with both the thin layer and the substrate assumed to exhibit local, isotropic linear response. Starting from the conventional three-dimensional (3D) slab model of the system, we derive a two-dimensional (2D) sheet model for the thin film in which the optical response is described by a sheet optical conductivity. We develop criteria for the applicability of this 2D sheet model for a layer with an optical thickness far smaller than the wavelength of the light. We examine in detail atomically thin semi-metallic and semiconductor van-der-Waals layers and ultrathin metal films as representative examples. Excellent agreement of the 2D sheet model with the 3D slab model is demonstrated over a broad spectral range from the radio frequency limit to the near ultraviolet. A linearized version of system response for the 2D model is also presented for the case where the influence of the optically thin layer is sufficiently weak. Analytical expressions for the applicability and accuracy of the different optical models are derived, and the appropriateness of the linearized treatment for the materials is considered. We discuss the advantages, as well as limitations, of these models for the purpose of deducing the optical response function of the thin layer from experiment. We generalize the theory to take into account in-plane anisotropy, layered thin film structures, and more general substrates. Implications of the 2D model for the transmission of light by the thin film and for the implementation of half- and totally absorbing layers are discussed.

Chalcogenide thin films deposited by rfMS technique using a single quaternary target

NASA Astrophysics Data System (ADS)

Prepelita, P.; Stavarache, I.; Negrila, C.; Garoi, F.; Craciun, V.

2017-12-01

Thin films of chalcogenide, Cu(In,Ga)Se2 have been obtained using a single quaternary target by radio frequency magnetron sputtering method, with thickness in the range 750 nm to 1200 nm. X-ray photoelectron spectroscopy investigations showed, that the composition of Cu(In,Ga)Se2 thin films was very similar to that of the used target CuIn0.75Ga0.25Se2. Identification of the chemical composition of Cu(In,Ga)Se2 thin films by XPS performed in high vacuum, emphasized that the samples exhibit surface features suitable to be integrated into the structure of solar cells. Atomic Force Microscopy and Scanning Electron Microscopy investigations showed that surface morphology was influenced by the increase in thickness of the Cu(In,Ga)Se2 layer. From X-Ray Diffraction investigations it was found that all films were polycrystalline, having a tetragonal lattice with a preferential orientation along the (112) direction. The optical reflectance as a function of wavelength was measured for the studied samples. The increase in thickness of the Cu(In,Ga)Se2 absorber determined a decrease of its optical bandgap value from 1.53 eV to 1.44 eV. The results presented in this paper showed an excellent alternative of obtaining Cu(In,Ga)Se2 compound thin films from a single target.

Solid state dewetting of thin plasmonic films under focused cw-laser irradiation

DOE PAGES

Abbott, William M.; Corbett, Simon; Cunningham, Graeme; ...

2017-12-21

Elevated temperatures and large thermal gradients are a significant source of component failure in microelectronics, and is the limiting factor in heat-assisted magnetic recording (HAMR). Here, we have investigated the effect of solid-state dewetting in Au thin films, as a function of local temperature, film thickness, and substrate adhesion. In this work, a localised temperature rise is induced in thin (≤ 50 nm) polycrystalline Au films on SiO 2 substrates via focused continuous-wave laser irradiation at 488 nm. The magnitude and distribution of the total temperature rise is measured using CCD-based thermoreflectance. This also allows a sensitive measurement of themore » temperature at which dewetting occurs, showing that for thin (≤ 50 nm) Au films without adhesion layers, rapid dewetting can occur at temperatures as low as 50° C. The time decay of the reflected light from the illuminating laser is used to monitor locally the dynamics of solid state dewetting. TEM diffraction analysis shows significant changes in the microstructure and crystallographic texture of the films as far as 10 µm away from the illuminated area. The use of a thin metallic adhesion layer (such as Ti or Cr) is shown to significantly improve the adhesion of the Au to the substrate and reduce the tendency towards dewetting, but does not entirely protect it from changes to the crystallographic texture.« less

Solid state dewetting of thin plasmonic films under focused cw-laser irradiation

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

Abbott, William M.; Corbett, Simon; Cunningham, Graeme

Elevated temperatures and large thermal gradients are a significant source of component failure in microelectronics, and is the limiting factor in heat-assisted magnetic recording (HAMR). Here, we have investigated the effect of solid-state dewetting in Au thin films, as a function of local temperature, film thickness, and substrate adhesion. In this work, a localised temperature rise is induced in thin (≤ 50 nm) polycrystalline Au films on SiO 2 substrates via focused continuous-wave laser irradiation at 488 nm. The magnitude and distribution of the total temperature rise is measured using CCD-based thermoreflectance. This also allows a sensitive measurement of themore » temperature at which dewetting occurs, showing that for thin (≤ 50 nm) Au films without adhesion layers, rapid dewetting can occur at temperatures as low as 50° C. The time decay of the reflected light from the illuminating laser is used to monitor locally the dynamics of solid state dewetting. TEM diffraction analysis shows significant changes in the microstructure and crystallographic texture of the films as far as 10 µm away from the illuminated area. The use of a thin metallic adhesion layer (such as Ti or Cr) is shown to significantly improve the adhesion of the Au to the substrate and reduce the tendency towards dewetting, but does not entirely protect it from changes to the crystallographic texture.« less

Thin film cell development workshop report

NASA Technical Reports Server (NTRS)

Woodyard, James R.

1991-01-01

The Thin Film Development Workshop provided an opportunity for those interested in space applications of thin film cells to debate several topics. The unique characteristics of thin film cells as well as a number of other issues were covered during the discussions. The potential of thin film cells, key research and development issues, manufacturing issues, radiation damage, substrates, and space qualification of thin film cells were discussed.

Effect of deposition temperature on the structural and optical properties of CdSe QDs thin films deposited by CBD method

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

Laatar, F., E-mail: fakher8laatar@gmail.com; Harizi, A.; Smida, A.

2016-06-15

Highlights: • Synthesis of CdSe QDs with L-Cysteine capping agent for applications in nanodevices. • The films of CdSe QDs present uniform and good dispersive particles at the surface. • Effect of bath temperature on the structural and optical properties of CdSe QDs thin films. • Investigation of the optical constants and dispersion parameters of CdSe QDs thin films. - Abstract: Cadmium selenide quantum dots (CdSe QDs) thin films were deposited onto glass substrates by a chemical bath deposition (CBD) method at different temperatures from an aqueous solution containing L-Cysteine (L-Cys) as capping agent. The evolution of the surface morphologymore » and elemental composition of the CdSe films were studied by AFM, SEM, and EDX analyses. Structural and optical properties of CdSe thin films were investigated by XRD, UV–vis and PL spectroscopy. The dispersion behavior of the refractive index is described using the single oscillator Wemple-DiDomenico (W-D) model, and the physical dispersion parameters are calculated as a function of deposition temperature. The dispersive optical parameters such as average oscillator energy (E{sub o}), dispersion energy (E{sub d}), and static refractive index (n{sub o}) were found to vary with the deposition temperature. Besides, the electrical free carrier susceptibility (χ{sub e}) and the carrier concentration of the effective mass ratio (N/m*) were evaluated according to the Spitzer-Fan model.« less

Composite polymeric film and method for its use in installing a very-thin polymeric film in a device

DOEpatents

Duchane, D.V.; Barthell, B.L.

1982-04-26

A composite polymeric film and a method for its use in forming and installing a very thin (< 10 ..mu..m) polymeric film are disclosed. The composite film consists of a thin film layer and a backing layer. The backing layer is soluble in a solvent in which the thin film layer is not soluble. In accordance with the method, the composite film is installed in a device in the same position in which it is sought to finally emplace the thin film. The backing layer is then selectiely dissolved in the solvent to leave the insoluble thin film layer as an unbacked film. The method permits a very thin film to e successfully installed in devices where the fragility of the film would preclude handling and installation by conventional methods.

Composite polymeric film and method for its use in installing a very thin polymeric film in a device

DOEpatents

Duchane, David V.; Barthell, Barry L.

1984-01-01

A composite polymeric film and a method for its use in forming and installing a very thin (<10 .mu.m) polymeric film are disclosed. The composite film consists of a thin film layer and a backing layer. The backing layer is soluble in a solvent in which the thin film layer is not soluble. In accordance with the method, the composite film is installed in a device in the same position in which it is sought to finally emplace the thin film. The backing layer is then selectively dissolved in the solvent to leave the insoluble thin film layer as an unbacked film. The method permits a very thin film to be successfully installed in devices where the fragility of the film would preclude handling and installation by conventional methods.

High-Temperature, Thin-Film Ceramic Thermocouples Developed

NASA Technical Reports Server (NTRS)

Sayir, Ali; Blaha, Charles A.; Gonzalez, Jose M.

2005-01-01

To enable long-duration, more distant human and robotic missions for the Vision for Space Exploration, as well as safer, lighter, quieter, and more fuel efficient vehicles for aeronautics and space transportation, NASA is developing instrumentation and material technologies. The high-temperature capabilities of thin-film ceramic thermocouples are being explored at the NASA Glenn Research Center by the Sensors and Electronics Branch and the Ceramics Branch in partnership with Case Western Reserve University (CWRU). Glenn s Sensors and Electronics Branch is developing thin-film sensors for surface measurement of strain, temperature, heat flux, and surface flow in propulsion system research. Glenn s Ceramics Branch, in conjunction with CWRU, is developing structural and functional ceramic technology for aeropropulsion and space propulsion.

Charge retention behavior of preferentially oriented and textured Bi3.25La0.75Ti3O12 thin films by electrostatic force microscopy

NASA Astrophysics Data System (ADS)

Kim, T. Y.; Lee, J. H.; Oh, Y. J.; Choi, M. R.; Jo, W.

2007-02-01

The authors report charge retention in preferentially (117) oriented and textured c-axis oriented ferroelectric Bi3.25La0.75Ti3O12 thin films by electrostatic force microscopy. Surface charges of the films were observed as a function of time in a selected area which consists of a single-poled region and a reverse-poled region. The highly (117) oriented film shows the extended exponential decay with characteristic scaling exponents, n =1.5-1.6. The preferentially c-axis oriented film shows a remarkable retained behavior regardless of the poling. Decay and retention mechanisms of the regions are explained by space-charge redistribution and trapping of defects in the films.

Mechanical design of thin-film diamond crystal mounting apparatus with optimized thermal contact and crystal strain for coherence preservation x-ray optics

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

Shu, Deming; Shvydko, Yury; Stoupin, Stanislav

A method and mechanical design for a thin-film diamond crystal mounting apparatus for coherence preservation x-ray optics with optimized thermal contact and minimized crystal strain are provided. The novel thin-film diamond crystal mounting apparatus mounts a thin-film diamond crystal supported by a thick chemical vapor deposition (CVD) diamond film spacer with a thickness slightly thicker than the thin-film diamond crystal, and two groups of thin film thermal conductors, such as thin CVD diamond film thermal conductor groups separated by the thick CVD diamond spacer. The two groups of thin CVD film thermal conductors provide thermal conducting interface media with themore » thin-film diamond crystal. A piezoelectric actuator is integrated into a flexural clamping mechanism generating clamping force from zero to an optimal level.« less

Investigation on single walled carbon nanotube thin films deposited by Langmuir Blodgett method

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

Vishalli,, E-mail: vishalli-2008@yahoo.com; Dharamvir, Keya; Kaur, Ramneek

2015-05-15

Langmuir Blodgett is a technique to deposit a homogeneous film with a fine control over thickness and molecular organization. Thin films of functionalized SWCNTs have been prepared by Langmuir Blodgett method. The good surface spreading properties of SWCNTs at air/water interface are indicated by surface pressure-area isotherm and the monolayer formed on water surface is transferred onto the quartz substrate by vertical dipping. A multilayer film is thus obtained in a layer by layer manner. The film is characterized by Atomic Force Microscope (AFM), UV-Vis-NIR spectroscopy and FTIR.AFM shows the surface morphology of the deposited film. UV-Vis-NIR spectroscopy shows themore » characteristic peaks of semiconducting SWCNTs. The uniformity of LB film can be used further in understanding the optical and electrical behavior of these materials.« less

Thermal, Structural, AC Conductivity, and Dielectric Properties of Ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate Thin Films

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-05-01

Thermal, structural, alternating-current (AC) conductivity (σ AC), and dielectric properties of ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate (HPQC) thin films have been studied. Thermogravimetry analysis and differential scanning calorimetry confirmed the thermal stability of HPQC over a wide temperature range. Fourier-transform infrared spectroscopy and x-ray diffraction analysis were carried out on HPQC in powder form and as-deposited thin film. The crystal system and space group type were determined for HPQC in powder form. The AC conductivity and dielectric properties were determined in the frequency range from 0.5 kHz to 5 MHz and temperature range from 296 K to 443 K. The AC electrical conduction of HPQC thin film was found to be governed by the small-polaron tunneling mechanism. The polaron hopping energy (W H), tunneling distance (R), and density of states (N) near the Fermi level were determined as functions of temperature and frequency. The dielectric properties of HPQC thin film were studied by analysis of Nyquist diagrams, the dissipation factor (tan δ), and real (ɛ') and imaginary (ɛ″) parts of the dielectric constant.

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

NASA Astrophysics Data System (ADS)

Subramanyam, Guru; Cole, M. W.; Sun, Nian X.; Kalkur, Thottam S.; Sbrockey, Nick M.; Tompa, Gary S.; Guo, Xiaomei; Chen, Chonglin; Alpay, S. P.; Rossetti, G. A.; Dayal, Kaushik; Chen, Long-Qing; Schlom, Darrell G.

2013-11-01

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.

Electrochemical characterization of organosilane-functionalized nanostructured ITO surfaces

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

Pruna, R., E-mail: rpruna@el.ub.edu; Palacio, F.; López, M.

2016-08-08

The electroactivity of nanostructured indium tin oxide (ITO) has been investigated for its further use in applications such as sensing biological compounds by the analysis of redox active molecules. ITO films were fabricated by using electron beam evaporation at different substrate temperatures and subsequently annealed for promoting their crystallization. The morphology of the deposited material was monitored by scanning electron microscopy, confirming the deposition of either thin films or nanowires, depending on the substrate temperature. Electrochemical surface characterization revealed a 45 % increase in the electroactive surface area of nanostructured ITO with respect to thin films, one third lower than themore » geometrical surface area variation determined by atomic force microscopy. ITO surfaces were functionalized with a model organic molecule known as 6-(ferrocenyl)hexanethiol. The chemical attachment was done by means of a glycidoxy compound containing a reactive epoxy group, the so-called 3-glycidoxypropyltrimethoxy-silane. ITO functionalization was useful for determining the benefits of nanostructuration on the surface coverage of active molecules. Compared to ITO thin films, an increase in the total peak height of 140 % was observed for as-deposited nanostructured electrodes, whereas the same measurement for annealed electrodes resulted in an increase of more than 400 %. These preliminary results demonstrate the ability of nanostructured ITO to increase the surface-to-volume ratio, conductivity and surface area functionalization, features that highly benefit the performance of biosensors.« less

Ultrasonic Attenuation of Surface Acoustic Waves in Thin Films of High Transition Temperature Superconducting Niobium-Tin and Niobium-Nitride

NASA Astrophysics Data System (ADS)

Fredricksen, Hans Peter

The ultrasonic attenuation of 600-700 MHz surface acoustic waves by two high T(,c), cubic crystal structure, superconducting thin films has been investigated. The films studied were two, 0.5 (mu) thin, Nb(,3)Sn samples, electron-beam codeposited on LiNbO(,3) and Quartz, and eleven NbN samples from 3 x 10('3) (ANGSTROM) to <(, )200 (ANGSTROM) thin, sputter deposited on LiNbO(,3). The Nb(,3)Sn (Al5 structure) film on Quartz was difficult to measure due to defects in the Quartz caused by the high deposition temperature ((DBLTURN)700(DEGREES)C) used to make the high T(,c) form of the compound. The Nb(,3)Sn film on LiNbO(,3), however, provided information about the transition temperature and energy gap at T = 0 K when the attenuation was measured as a function of temperature in zero magnetic field. A theory is developed to predict the electron-phonon produced normal state attenuation of surface acoustic waves by a thin, loss producing film on a nonattenuating substrate. Using a viscous drag model for the attenuation, the predictions of the theory are compared to the measured normal state attenuation to find the electron mean-free-path for the Nb(,3)Sn film on LiNbO(,3). The attenuation measured for this film as a function of applied magnetic field for four temperatures below T(,c) showed the sample to be an impurity rich type II superconductor with H(,c(,2)) (T = 0 K) = 85 KG, having GLAG theory constants: (kappa)(,2)(t=1) = 28.5 and (kappa)(t=1) = 29.2. The attenuation curves of the nine thickest NbN samples were non-BCS-like and very similar. Measured as a function of temperature only, because we could not reach the high critical fields of the samples, the attenuation showed an initial drop at T(,c) of about 1-2 dB which then leveled off until the temperature was below 0.5 T(,c), where the rate of decrease was much slower than the initial drop. A qualitative description of this behavior is derived from the Kosterlitz-Thouless vortex-antivortex theory. Although the thinnest NbN film did not show an attenuation change at T(,c), the next thinnest did. In this case, the measured decrease of nearly 40 dB is explained by the change in boundary condition when the substrate surface changes from "open" to "shortened" when the film becomes superconducting.

Microwave Hybrid Integrated Circuit Applicatins of High Transition Temperature Superconductor

NASA Astrophysics Data System (ADS)

Lu, Shih-Lin

This research work involves microwave characterization of high Tc superconducting (HTS) thin film using microstrip ring resonators, studying the nonlinear properties of HTS thin film transmission lines using two-tone intermodulation technique, coupling mechanisms and coupling factors of microstrip ring resonators side coupled to a microstrip line, two-port S-parameters measurements of GaAs MESFET at low temperature, and the design and implementation of hybrid ring resonator stabilized microwave oscillator using both metal films and superconducting films. A microstrip ring resonators operating at 10 GHz have been fabricated from YBCO HTS thin films deposited on one side of LaAl_2O_3 substrates. Below 60^circ Kelvin the measured unloaded Q of the HTS thin film microstrip ring resonators are more than 1.5 times that of gold film resonators. The two distinct but very close resonance peaks of a ring resonator side coupled to a microstrip line are experimentally identified as due to odd-mode and even-mode coupling. These two mechanisms have different characteristic equivalent circuit models and lead to different coupling coefficients and loaded resonance frequencies. The coupling factors for the two coupling modes are calculated using piecewise coupled line approximations. The two-port S-parameters measurement techniques and GaAs MESFET low temperature DC and microwave characteristics have been investigated. A system errors model including the errors caused by the line constriction at low temperature has been proposed and a temperature errors correction procedure has been developed for the two-port microwave S-parameters measurements at low temperature. The measured GaAs MESFET DC characteristics shows a 20% increase in transconductance at 77^circ K. There is also a 2 db increase in /S21/ at 77^circ K. The microwave oscillator stabilized with both metal and HTS thin film ring resonators have been studied. The tuning ability of the oscillator by a varactor diode has also been investigated. The phase noise performance of one side of the high Tc film oscillator does not show appreciable improvement over the gold film oscillator. With a varactor diode, the oscillator tuning range can be 300 MHz more. Two-tone intermodulation distortion (IMD) at 6.3 GHz in an HTS YBCO superconducting thin film microstrip transmission line on LaAl_2O _3 substrates are experimentally studied. At fixed input power, the 3rd order IMD power as function of temperature shows a minimum at a temperature around 60^circ Kelvin. With DC current applied, the second order IMD is observed and shows a strong functional dependance to the applied DC current and input power.

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa2Cu3O7 thin films

NASA Technical Reports Server (NTRS)

Xing, W.; Heinrich, B.; Zhou, HU; Fife, A. A.; Cragg, A. R.; Grant, P. D.

1995-01-01

Mapping of the magnetic flux density B(sub z) (perpendicular to the film plane) for a YBa2Cu3O7 thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B(sub z) distributions. From the known sheet magnetization, the tangential (B(sub x,y)) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B(sub x,y)/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

Properties of dielectric dead layers for SrTiO3 thin films on Pt electrodes

NASA Astrophysics Data System (ADS)

Finstrom, Nicholas H.; Cagnon, Joel; Stemmer, Susanne

2007-02-01

Dielectric measurements as a function of temperature were used to characterize the properties of the dielectric dead layers in parallel-plate capacitors with differently textured SrTiO3 thin films and Pt electrodes. The apparent thickness dependence of the permittivity was described with low-permittivity passive (dead) layers at the interfaces connected in series with the bulk of the SrTiO3 film. Interfacial capacitance densities changed with the film microstructure and were weakly temperature dependent. Estimates of the dielectric dead layer thickness and permittivity were limited by the film surface roughness (˜5nm ). The consequences for the possible origins of dielectric dead layers that have been proposed in the literature are discussed.

Influence of Metallic Indium Concentration on the Properties of Indium Oxide Thin Films

NASA Astrophysics Data System (ADS)

Kalkan, N.

2016-10-01

Current-voltage characteristics of indium-embedded indium oxide thin films (600-850 Å), with Ag electrodes approximately 1000 Å thick, prepared by reactive evaporation of pure metallic indium in partial air pressure have been studied for substrate temperatures between 50 and 125°C. The optical properties of these films have also been investigated as a function of metallic indium concentration and substrate temperature. I-V characteristics of all the samples are non-ohmic, independent of metallic indium concentration. The conductivity of the films increases but the optical transmission decreases with increasing metallic indium concentration. Metallic indium concentration was found to be an important parameter affecting the film properties. Furthermore, two possible conduction mechanisms are proposed.

Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography.

PubMed

Agrawal, Anant; Chen, Chao-Wei; Baxi, Jigesh; Chen, Yu; Pfefer, T Joshua

2013-07-01

In optical coherence tomography (OCT), axial resolution is one of the most critical parameters impacting image quality. It is commonly measured by determining the point spread function (PSF) based on a specular surface reflection. The contrast transfer function (CTF) provides more insights into an imaging system's resolving characteristics and can be readily generated in a system-independent manner, without consideration for image pixel size. In this study, we developed a test method for determination of CTF based on multi-layer, thin-film phantoms, evaluated using spectral- and time-domain OCT platforms with different axial resolution values. Phantoms representing six spatial frequencies were fabricated and imaged. The fabrication process involved spin coating silicone films with precise thicknesses in the 8-40 μm range. Alternating layers were doped with a specified concentration of scattering particles. Validation of layer optical properties and thicknesses were achieved with spectrophotometry and stylus profilometry, respectively. OCT B-scans were used to calculate CTFs and results were compared with convetional PSF measurements based on specular reflections. Testing of these phantoms indicated that our approach can provide direct access to axial resolution characteristics highly relevant to image quality. Furthermore, tissue phantoms based on our thin-film fabrication approach may have a wide range of additional applications in optical imaging and spectroscopy.

Materials Study of NbN and Ta x N Thin Films for SNS Josephson Junctions

DOE PAGES

Missert, Nancy; Brunke, Lyle; Henry, Michael D.; ...

2017-02-15

We investigated properties of NbN and Ta xN thin films grown at ambient temperatures on SiO 2/Si substrates by reactive-pulsed laser deposition and reactive magnetron sputtering (MS) as a function of N 2 gas flow. Both techniques produced films with smooth surfaces, where the surface roughness did not depend on the N 2 gas flow during growth. High crystalline quality, (111) oriented NbN films with T c up to 11 K were produced by both techniques for N contents near 50%. The low temperature transport properties of the Ta xN films depended upon both the N 2 partial pressure usedmore » during growth and the film thickness. Furthermore, the root mean square surface roughness of Ta xN films grown by MS increased as the film thickness decreased down to 10 nm.« less

Tuning optical properties of CdTe films with nanocolumnar morphology grown using OAD for improving light absorption in thin-film solar cells

NASA Astrophysics Data System (ADS)

Daza, L. G.; Canché-Caballero, V.; Chan y Díaz, E.; Castro-Rodríguez, R.; Iribarren, A.

2017-11-01

CdTe films with transversal morphology in form of tilted nanocolumns were obtained by sublimation method using a rotating vapour source combined with the oblique angle deposition technique. The tilt angles of the nanocolumnar structures increases as the substrate inclination also increase. CdTe films exhibited cubic zinc blend lattice under compressive strain. Morphological and x-ray diffractometry analysis indicated that the nanocolumns are grains stacked in the nanocolumn preferential growth direction, except for the films with non-inclined substrate. We found an interesting dependence of band gap energy and the refractive index as functions of the microstrain distribution due to the nanocolumn tilt in the films from 0° to about 25°. These facts evidence the possibility of carried out film strain engineering for optimizing optoelectronics devices as we propose for the case of thin-film solar cells.

Integrated Temperature and Hydrogen Sensors with MEMS Technology

PubMed Central

Jiang, Hongchuan; Huang, Min; Yu, Yibing; Tian, Xiaoyu; Zhang, Wanli; Zhang, Jianfeng; Huang, Yifan; Yu, Kun

2017-01-01

In this work, a PdNi thin film hydrogen gas sensor with integrated Pt thin film temperature sensor was designed and fabricated using the micro-electro-mechanical system (MEMS) process. The integrated sensors consist of two resistors: the former, based on Pt film, is used as a temperature sensor, while the latter had the function of hydrogen sensing and is based on PdNi alloy film. The temperature coefficient of resistance (TCR) in both devices was measured and the output response of the PdNi film hydrogen sensor was calibrated based on the temperature acquired by the Pt temperature sensor. The SiN layer was deposited on top of Pt film to inhibit the hydrogen diffusion and reduce consequent disturbance on temperature measurement. The TCR of the PdNi film and the Pt film was about 0.00122/K and 0.00217/K, respectively. The performances of the PdNi film hydrogen sensor were investigated with hydrogen concentrations from 0.3% to 3% on different temperatures from 294.7 to 302.2 K. With the measured temperature of the Pt resistor and the TCR of the PdNi film, the impact of the temperature on the performances of the PdNi film hydrogen sensor was reduced. The output response, response time and recovery time of the PdNi film hydrogen sensors under the hydrogen concentration of 0.5%, 1.0%, 1.5% and 2.0% were measured at 313 K. The output response of the PdNi thin film hydrogen sensors increased with increasing hydrogen concentration while the response time and recovery time decreased. A cycling test between pure nitrogen and 3% hydrogen concentration was performed at 313 K and PdNi thin film hydrogen sensor demonstrated great repeatability in the cycling test. PMID:29301220

Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

NASA Technical Reports Server (NTRS)

Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

2014-01-01

We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

Permanent laser conditioning of thin film optical materials

DOEpatents

Wolfe, C. Robert; Kozlowski, Mark R.; Campbell, John H.; Staggs, Michael; Rainer, Frank

1995-01-01

The invention comprises a method for producing optical thin films with a high laser damage threshold and the resulting thin films. The laser damage threshold of the thin films is permanently increased by irradiating the thin films with a fluence below an unconditioned laser damage threshold.

Electromagnetic properties of thin-film transformer-coupled superconducting tunnel junctions

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

Finnegan, T.F.; Lacquaniti, V.; Vaglio, R.

1981-09-01

Multisection superconducting microstrip transformers with designed output impedances below 0.1 ..cap omega.. have been fabricated via precise photolithographic techniques to investigate the electromagnetic properties of Nb-Nb oxide-Pb tunnel junctions. The low-impedance transformer sections incorporate a rf sputtered thin-film Ta-oxide dielectric, and the reproducible external coupling achievable with this type of geometry makes possible the systematic investigation of electromagnetic device parameters as a function of tunneling oxide thickness.

Variation of microstructural and optical properties in SILAR grown ZnO thin films by thermal treatment.

PubMed

Valanarasu, S; Dhanasekaran, V; Chandramohan, R; Kulandaisamy, I; Sakthivelu, A; Mahalingam, T

2013-08-01

The influence of thermal treatment on the structural and morphological properties of the ZnO films deposited by double dip Successive ionic layer by adsorption reaction is presented. The effect of annealing temperature and time in air ambient is presented in detail. The deposited films were annealed from 200 to 400 degrees C in air and the structural properties were determined as a function of annealing temperature by XRD. The studies revealed that films were exhibiting preferential orientation along (002) plane. The other structural parameters like the crystallite size (D), micro strain (epsilon), dislocation density (delta) and stacking fault (alpha) of as-deposited and annealed ZnO films were evaluated and reported. The optical properties were also studied and the band gap of the ZnO thins films varied from 3.27 to 3.04 eV with the annealing temperature. SEM studies revealed that the hexagonal shaped grains with uniformly distributed morphology in annealed ZnO thin films. It has been envisaged using EDX analysis that the near stoichiometric composition of the film can be attained by thermal treatment during which microstructural changes do occur.

Retention of Antibacterial Activity in Geranium Plasma Polymer Thin Films

PubMed Central

Al-Jumaili, Ahmed; Bazaka, Kateryna

2017-01-01

Bacterial colonisation of biomedical devices demands novel antibacterial coatings. Plasma-enabled treatment is an established technique for selective modification of physicochemical characteristics of the surface and deposition of polymer thin films. We investigated the retention of inherent antibacterial activity in geranium based plasma polymer thin films. Attachment and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was significantly reduced on the surfaces of samples fabricated at 10 W radio frequency (RF) power, compared to that of control or films fabricated at higher input power. This was attributed to lower contact angle and retention of original chemical functionality in the polymer films fabricated under low input power conditions. The topography of all surfaces was uniform and smooth, with surface roughness of 0.18 and 0.69 nm for films fabricated at 10 W and 100 W, respectively. Hardness and elastic modules of films increased with input power. Independent of input power, films were optically transparent within the visible wavelength range, with the main absorption at ~290 nm and optical band gap of ~3.6 eV. These results suggest that geranium extract-derived polymers may potentially be used as antibacterial coatings for contact lenses. PMID:28902134

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

Sandoval-Paz, M.G., E-mail: myrnasandoval@udec.cl; Rodríguez, C.A.; Porcile-Saavedra, P.F.

Copper (I) selenide thin films with orthorhombic and cubic structure were deposited on glass substrates by using the chemical bath deposition technique. The effects of the solution pH on the films growth and subsequently the structural, optical and electrical properties of the films were studied. Films with orthorhombic structure were obtained from baths wherein both metal complex and hydroxide coexist; while films with cubic structure were obtained from baths where the metal hydroxide there is no present. The structural modifications are accompanied by changes in bandgap energy, morphology and electrical resistivity of the films. - Graphical abstract: “Study of themore » crystallographic phase change on copper (I) selenide thin films prepared through chemical bath deposition by varying the pH of the solution” by M. G. Sandoval-Paz, C. A. Rodríguez, P. F. Porcile-Saavedra, C. Trejo-Cruz. Display Omitted - Highlights: • Copper (I) selenide thin films were obtained by chemical bath deposition. • Orthorhombic to cubic phase change was induced by varying the reaction solution pH. • Orthorhombic phase is obtained mainly from a hydroxides cluster mechanism. • Cubic phase is obtained mainly from an ion by ion mechanism. • Structural, optical and electrical properties are presented as a function of pH.« less

Microscopic image processing systems for measuring nonuniform film thickness profiles

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

Liu, A.H.; Plawsky, J.L.; DasGupta, S.

1994-01-01

In very thin liquid films. transport processes are controlled by the temperature and the interfacial intermolecular force field which is a function of the film thickness profile and interfacial properties. The film thickness profile and interfacial properties can be measured most efficiently using a microscopic image processing system. IPS, to record the intensity pattern of the reflected light from the film. There are two types of IPS: an image analyzing interferometer (IAI) and/or an image scanning ellipsometer (ISE). The ISE is a novel technique to measure the two dimensional thickness profile of a nonuniform, thin film, from 1 nm upmore » to several {mu}m, in a steady state as well as in a transient state. It is a full field imaging technique which can study every point on the surface simultaneously with high spatial resolution and thickness sensitivity, i.e., it can measure and map the 2-D film thickness profile. Using the ISE, the transient thickness profile of a draining thin liquid film was measured and modeled. The interfacial conditions were determined in situ by measuring the Hamaker constant. The ISE and IAI systems are compared.« less

Effect of deposition temperature on the properties of Al-doped ZnO films prepared by pulsed DC magnetron sputtering for transparent electrodes in thin-film solar cells

NASA Astrophysics Data System (ADS)

Kim, Doo-Soo; Park, Ji-Hyeon; Shin, Beom-Ki; Moon, Kyeong-Ju; Son, Myoungwoo; Ham, Moon-Ho; Lee, Woong; Myoung, Jae-Min

2012-10-01

A simple but scalable approach to the production of surface-textured Al-doped ZnO(AZO) films for low-cost transparent electrode applications in thin-film solar cells is introduced in this study by combining pulsed dc magnetron sputtering (PDMS) with wet etching in sequence. First, structural, electrical, and optical properties of the AZO films prepared by a PDMS were investigated as functions of deposition temperature to obtain transparent electrode films that can be used as indium-free alternative to ITO electrodes. Increase in the deposition temperature to 230 °C accompanied the improvement in crystalline quality and doping efficiency, which enabled the lowest electrical resistivity of 4.16 × 10-4 Ω cm with the carrier concentration of 1.65 × 1021 cm-3 and Hall mobility of 11.3 cm2/V s. The wet etching of the films in a diluted HCl solution resulted in surface roughening via the formation of crater-like structures without significant degradation in the electrical properties, which is responsible for the enhanced light scattering capability required for anti-reflective electrodes in thin film solar cells.

Measurement of thin films using very long acoustic wavelengths

NASA Astrophysics Data System (ADS)

Clement, G. T.; Nomura, H.; Adachi, H.; Kamakura, T.

2013-12-01

A procedure for measuring material thickness by means of necessarily long acoustic wavelengths is examined. The approach utilizes a temporal phase lag caused by the impulse time of wave momentum transferred through a thin layer that is much denser than its surrounding medium. In air, it is predicted that solid or liquid layers below approximately 1/2000 of the acoustic wavelength will exhibit a phase shift with an arctangent functional dependence on thickness and layer density. The effect is verified for thin films on the scale of 10 μm using audible frequency sound (7 kHz). Soap films as thin as 100 nm are then measured using 40 kHz air ultrasound. The method's potential for imaging applications is demonstrated by combining the approach with near-field holography, resulting in reconstructions with sub-wavelength resolution in both the depth and lateral directions. Potential implications at very high and very low acoustic frequencies are discussed.

Self Healing Coating/Film Project

NASA Technical Reports Server (NTRS)

Summerfield, Burton; Thompson, Karen; Zeitlin, Nancy; Mullenix, Pamela; Calle, Luz; Williams, Martha

2015-01-01

Kennedy Space Center (KSC) has been developing self healing materials and technologies. This project seeks to further develop self healing functionality in thin films for applications such as corrosion protective coatings, inflatable structures, space suit materials, and electrical wire insulation.

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.

Effects of annealing temperature on the physicochemical, optical and photoelectrochemical properties of nanostructured hematite thin films prepared via electrodeposition method

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

Phuan, Yi Wen; Chong, Meng Nan, E-mail: Chong.Meng.Nan@monash.edu; Sustainable Water Alliance, Advanced Engineering Platform, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway 46150 Selangor DE

2015-09-15

Highlights: • Nanostructured hematite thin films were synthesized via electrodeposition method. • Effects of annealing on size, grain boundary and PEC properties were examined. • Photocurrents generation was enhanced when the thin films were annealed at 600 °C. • The highest photocurrent density of 1.6 mA/cm{sup 2} at 0.6 V vs Ag/AgCl was achieved. - Abstract: Hematite (α-Fe{sub 2}O{sub 3}) is a promising photoanode material for hydrogen production from photoelectrochemical (PEC) water splitting due to its wide abundance, narrow band-gap energy, efficient light absorption and high chemical stability under aqueous environment. The key challenge to the wider utilisation of nanostructuredmore » hematite-based photoanode in PEC water splitting, however, is limited by its low photo-assisted water oxidation caused by large overpotential in the nominal range of 0.5–0.6 V. The main aim of this study was to enhance the performance of hematite for photo-assisted water oxidation by optimising the annealing temperature used during the synthesis of nanostructured hematite thin films on fluorine-doped tin oxide (FTO)-based photoanodes prepared via the cathodic electrodeposition method. The resultant nanostructured hematite thin films were characterised using field emission-scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-visible spectroscopy and Fourier transform infrared spectroscopy (FTIR) for their elemental composition, average nanocrystallites size and morphology; phase and crystallinity; UV-absorptivity and band gap energy; and the functional groups, respectively. Results showed that the nanostructured hematite thin films possess good ordered nanocrystallites array and high crystallinity after annealing treatment at 400–600 °C. FE-SEM images illustrated an increase in the average hematite nanocrystallites size from 65 nm to 95 nm when the annealing temperature was varied from 400 °C to 600 °C. As the crystallites size increases, the grain boundaries reduce and this suppresses the recombination rate of electron–hole pairs on the nanostructured hematite thin films. As a result, the measured photocurrent densities of nanostructured hematite thin films also increased. The highest measured photocurrent density of 1.6 mA/cm{sup 2} at 0.6 V vs Ag/AgCl in 1 M NaOH electrolyte was achieved for the nanostructured hematite thin film annealed at 600 °C. This study had confirmed that strong interdependencies exist between the average hematite nanocrystallites size and grain boundaries with annealing temperature on the eventual PEC water splitting performance of nanostructured hematite thin films. The annealed hematite thin films at a higher temperature will enhance the nanocrystals growth and thus, suppressing the electron–hole pairs recombination rate, lowering the grain boundary resistance and enabling higher photocurrent flow at the molecular level. As a result, the photocurrent density and thus, the overall PEC water splitting performance of the nanostructured hematite thin films are significantly enhanced.« less

Processing effects on the microstructure and dielectric properties of hydrothermal barium titanate and (barium,strontium)titanate thin films

NASA Astrophysics Data System (ADS)

McCormick, Mark Alan

The goal of this work was to produce BaTiO3 and BaxSr (1-x)TiO3 (BST) thin films with high dielectric constants, using a low-temperature (<100°C) hydrothermal synthesis route. To accomplish this, titanium metal-organic precursor films were spin-cast onto metal-coated glass substrates and converted to polycrystalline BaTiO3 or BST upon reacting in aqueous solutions of Ba(OH)2 or Ba(OH)2 and Sr(OH)2. The influences of solution molarity, processing temperature, and reaction time on thin film reaction kinetics, microstructure, and dielectric properties were examined for BaTiO3 films. Post-deposition annealing at temperatures as low as 200°C substantially affected the lattice parameter, dielectric constant, and dielectric loss. This behavior is explained in terms of hydroxyl defect incorporation during film formation. Current-voltage (I-V) measurements were performed to determine the dominant conduction mechanism(s) during application of a do field, and to extract the metal/ceramic barrier height. In particular, Schottky barrier-limited conduction and Poole-Frenkel conduction were investigated as potential leakage mechanisms. For BST thin films, film stoichiometry deviated from the initial solution composition, with a preferred incorporation of Sr2+ into the perovskite lattice. The dielectric constant of the BST films was measured as a function of composition (Ba:Sr ratio) and temperature over the range 25--150°C. Finally, capacitance-voltage (C-V) measurements were made for BST films to determine the influence of film composition on dielectric tunability.

Voltage-Controlled Spray Deposition of Multiwalled Carbon Nanotubes on Semiconducting and Insulating Substrates

NASA Astrophysics Data System (ADS)

Maulik, Subhodip; Sarkar, Anirban; Basu, Srismrita; Daniels-Race, Theda

2018-05-01

A facile, cost-effective, voltage-controlled, "single-step" method for spray deposition of surfactant-assisted dispersed carbon nanotube (CNT) thin films on semiconducting and insulating substrates has been developed. The fabrication strategy enables direct deposition and adhesion of CNT films on target samples, eliminating the need for substrate surface functionalization with organosilane binder agents or metal layer coatings. Spray coating experiments on four types of sample [bare silicon (Si), microscopy-grade glass samples, silicon dioxide (SiO2), and polymethyl methacrylate (PMMA)] under optimized control parameters produced films with thickness ranging from 40 nm to 6 μm with substantial surface coverage and packing density. These unique deposition results on both semiconducting and insulator target samples suggest potential applications of this technique in CNT thin-film transistors with different gate dielectrics, bendable electronics, and novel CNT-based sensing devices, and bodes well for further investigation into thin-film coatings of various inorganic, organic, and hybrid nanomaterials on different types of substrate.

MISSE 5 Thin Films Space Exposure Experiment

NASA Technical Reports Server (NTRS)

Harvey, Gale A.; Kinard, William H.; Jones, James L.

2007-01-01

The Materials International Space Station Experiment (MISSE) is a set of space exposure experiments using the International Space Station (ISS) as the flight platform. MISSE 5 is a co-operative endeavor by NASA-LaRC, United Stated Naval Academy, Naval Center for Space Technology (NCST), NASA-GRC, NASA-MSFC, Boeing, AZ Technology, MURE, and Team Cooperative. The primary experiment is performance measurement and monitoring of high performance solar cells for U.S. Navy research and development. A secondary experiment is the telemetry of this data to ground stations. A third experiment is the measurement of low-Earth-orbit (LEO) low-Sun-exposure space effects on thin film materials. Thin films can provide extremely efficacious thermal control, designation, and propulsion functions in space to name a few applications. Solar ultraviolet radiation and atomic oxygen are major degradation mechanisms in LEO. This paper is an engineering report of the MISSE 5 thm films 13 months space exposure experiment.

High performance sandwich structured Si thin film anodes with LiPON coating

NASA Astrophysics Data System (ADS)

Luo, Xinyi; Lang, Jialiang; Lv, Shasha; Li, Zhengcao

2018-06-01

The sandwich structured silicon thin film anodes with lithium phosphorus oxynitride (LiPON) coating are synthesized via the radio frequency magnetron sputtering method, whereas the thicknesses of both layers are in the nanometer range, i.e. between 50 and 200 nm. In this sandwich structure, the separator simultaneously functions as a flexible substrate, while the LiPON layer is regarded as a protective layer. This sandwich structure combines the advantages of flexible substrate, which can help silicon release the compressive stress, and the LiPON coating, which can provide a stable artificial solid-electrolyte interphase (SEI) film on the electrode. As a result, the silicon anodes are protected well, and the cells exhibit high reversible capacity, excellent cycling stability and good rate capability. All the results demonstrate that this sandwich structure can be a promising option for high performance Si thin film lithium ion batteries.

Dynamics in thin folded polymer films

NASA Astrophysics Data System (ADS)

Croll, Andrew; Rozairo, Damith

Origami and Kirigami inspired structures depend on a complex interplay between geometry and material properties. While clearly important to the overall function, very little attention has focused on how extreme curvatures and singularities in real materials influence the overall dynamic behaviour of folded structures. In this work we use a set of three polymer thin films in order to closely examine the interaction of material and geometry. Specifically, we use polydimethylsiloxane (PDMS), polystyrene (PS) and polycarbonate (PC) thin films which we subject to loading in several model geometries of varying complexity. Depending on the material, vastly different responses are noted in our experiments; D-cones can annihilate, cut or lead to a crumpling cascade when pushed through a film. Remarkably, order can be generated with additional perturbation. Finally, the role of adhesion in complex folded structures can be addressed. AFOSR under the Young Investigator Program (FA9550-15-1-0168).

High performance sandwich structured Si thin film anodes with LiPON coating

NASA Astrophysics Data System (ADS)

Luo, Xinyi; Lang, Jialiang; Lv, Shasha; Li, Zhengcao

2018-04-01

The sandwich structured silicon thin film anodes with lithium phosphorus oxynitride (LiPON) coating are synthesized via the radio frequency magnetron sputtering method, whereas the thicknesses of both layers are in the nanometer range, i.e. between 50 and 200 nm. In this sandwich structure, the separator simultaneously functions as a flexible substrate, while the LiPON layer is regarded as a protective layer. This sandwich structure combines the advantages of flexible substrate, which can help silicon release the compressive stress, and the LiPON coating, which can provide a stable artificial solidelectrolyte interphase (SEI) film on the electrode. As a result, the silicon anodes are protected well, and the cells exhibit high reversible capacity, excellent cycling stability and good rate capability. All the results demonstrate that this sandwich structure can be a promising option for high performance Si thin film lithium ion batteries.

Laser-induced dewetting of silver-doped chalcogenide glasses

NASA Astrophysics Data System (ADS)

Douaud, Alexandre; Messaddeq, Sandra Helena; Boily, Olivier; Messaddeq, Younès

2018-07-01

We report the observation of laser-induced dewetting responsible for the formation of periodic relief structures in silver-based chalcogenide thin-films. By varying the concentration of silver in the Agx(As20S80)100-x system (with x = 0, 4, 9 and 36), different surface relief structures are formed. The evolution of the surface changes as a function of laser parameters (power density, duration of exposure, and polarisation) as well as film thickness and silver concentration has been investigated. The scanning electron microscopy and atomic force microscopy images of irradiated spots show periodic ripples aligned perpendicularly to the electric field of incident light. Our results show that addition of silver into sulphur-rich chalcogenide thin-films improves the dewetting when compared to pure As20S80 thin-films. The changes in surface morphology were attributable to photo-induced chemical modifications and a laser-driven molecular rearrangement.

Functionalized copper(II)-phthalocyanine in solution and as thin film: photochemical and morphological characterization toward applications.

PubMed

Ingrosso, Chiara; Curri, M Lucia; Fini, Paola; Giancane, Gabriele; Agostiano, Angela; Valli, Ludovico

2009-09-01

This article reports on an extensive investigation on a functionalized phthalocyanine, namely, copper(II) tetrakis-(isopropoxy-carbonyl)-phthalocyanine (TIPCuPc). The self-association of the molecules is extensively described in solution in different solvents (DMSO, DMF, CHCl(3), pyridine) by means of UV-vis steady state spectroscopy at the air/water interface by Brewster angle microscopy (BAM) and in thin films by using atomic force microscopy (AFM). We investigated the morphology of TIPCuPc as thin film by evaluating different factors: temperature, solvent, concentration, transferring procedure (spin-coating and Langmuir-Schafer technique), and nature of the substrate (mica and quartz). The behavior of the molecules under UV light irradiation and their thermal stability were studied as well. Such a detailed study can allow a suitable processing of this phthalocyanine derivative for future applications. Here the photoelectrochemical activity of the phthalocyanine was investigated when suitably combined as sensitizer with rodlike TiO(2) nanocrystals (NCs) in hybrid junctions integrated in a photoelectrochemical cell.

PREFACE: Proceedings Symposium G of E-MRS Spring Meeting on Fundamentals and Technology of Multifunctional Oxide Thin Films

NASA Astrophysics Data System (ADS)

2010-07-01

Oxide materials exhibit a large variety of functional properties that are useful in a plethora of applications. Symposium G focused on oxide thin films that include dielectric or switching properties. Its program mirrored very well the strong worldwide search for high-K thin films for gate, memory, and on-chip capacitors, as well as the emerging field of functional thin films for MEMS. A complete session was devoted to the colossal effect of dielectric response in (Ca,Cu)TiO3, representing the major European research groups in this field. A comprehensive overview on this phenomenon was given by D Sinclair J Wolfman presented the latest results on CCTO thin films obtained by wafer scale pulsed laser deposition. A Loidl showed the analytical power of dielectric spectroscopy when covering the complete frequency range from 1-1012 Hz, i.e. from space charge to phonon contributions at the example of CCTO. Another session was devoted to applications in non-volatile memories, covering various effects including ferroelectric and resistive switching, the complex behavior of oxide tunnel junctions (H Kohlstedt), the possibility to manipulate the magnetic state of a 2d-electron gas by the polarization of an adjacent ferroelectric gate (I Stolitchnov). Latest advancements in ALD processing for high-K thin films in dynamic RAM were reported by S Ramanathan. The advancement of piezoelectric PZT thin film MEMS devices was well documented by outstanding talks on their developments in industry (M Klee, F Tyholdt), new possibilities in GHz filters (T Matshushima), advancements in sol-gel processing (B Tuttle, H Suzuki), and low temperature integration approaches by UV light curing (S Trolier-McKinstry). Recent advances in incipient ferroelectric thin films and nano composites for tunable capacitors in microwave applications were present by A Vorobiev and T Yamada. Integrated electro-optics is another field to be conquered by thin film structures. The impressive progress made in this field was highlighted by P Günter. Many contributions were devoted to processing techniques, showing the increasing importance of CVD techniques to deposit for instance perovskite thin films (G Malandrino). Nevertheless, stunning results were obtained by a sophisticated MBE tool allowing for precise compositional control of individual oxide monolayers and thus enabling High-Tc supraconductivity in individual monolayers to be addressed (I Bosovic). Oxides do not only gleam with giant dielectric properties, giant electronic conduction (superconductivity), there is also a giant electro-caloric effect, as explained by Z Kutnjak. The symposium could take advantage of the EU projects NUOTO and CAMELIA that organized a joint session on giant K dielectrics to present their project results to the scientific and industrial community. The symposium organizers Paul Muralt, EPFL, Lausanne, Switzerland Marija Kosec, Josef Stefan Institute, Ljubljana, Slovenia Vito Raineri, IMM-CNR, Catania, Italy Sebastiano Ravesi, STMicroelectronics, Catania, Italy Scientific Committee Robert Blinc (Josef Stefan Inst., Slovenia) Wolfgang Kleemann (Univ. Duisburg, Germany) Raffaella Lo Nigro (IMM-CNR, Italy) Ian M Reaney (Univ. Sheffield, Great Britain) T Metzger (EPCOS, Germany) Rainer Waser (TH Aachen, Germany)

Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells.

PubMed

Park, Jinjoo; Shin, Chonghoon; Park, Hyeongsik; Jung, Junhee; Lee, Youn-Jung; Bong, Sungjae; Dao, Vinh Ai; Balaji, Nagarajan; Yi, Junsin

2015-03-01

We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (σ(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with σ(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively.

YSZ thin films with minimized grain boundary resistivity

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

Mills, Edmund M.; Kleine-Boymann, Matthias; Janek, Juergen

2016-03-31

In recent years, interface engineering of solid electrolytes has been explored to increase their ionic conductivity and improve the performance of solid oxide fuel cells and other electrochemical power sources. It has been observed that the ionic conductivity of epitaxially grown thin films of some electrolytes is dramatically enhanced, which is often attributed to effects (e. g. strain-induced mobility changes) at the heterophase boundary with the substrate. Still largely unexplored is the possibility of manipulation of grain boundary resistivity in polycrystalline solid electrolyte films, clearly a limiting factor in their ionic conductivity. Here we report that the ionic conductivity ofmore » yttria stabilized zirconia thin films with nano-­ columnar grains grown on a MgO substrate nearly reaches that of the corresponding single crystal when the thickness of the films becomes less than roughly 8 nm (smaller by a factor of three at 500°C). Using impedance spectroscopy, the grain boundary resistivity was probed as a function of film thickness. The resistivity of the grain boundaries near the film- substrate interface and film surface (within 4 nm of each) was almost entirely eliminated. This minimization of grain boundary resistivity is attributed to Mg2+ diffusion from the MgO substrate into the YSZ grain boundaries, which is supported by time of flight secondary ion mass spectroscopy measurements. We suggest grain boundary “design” as an attractive method to obtain highly conductive solid electrolyte thin films.« less

Formation of Indium-Doped Zinc Oxide Thin Films Using Ultrasonic Spray Pyrolysis: The Importance of the Water Content in the Aerosol Solution and the Substrate Temperature for Enhancing Electrical Transport

PubMed Central

Biswal, Rajesh; Castañeda, Luis; Moctezuma, Rosario; Vega-Pérez, Jaime; De La Luz Olvera, María; Maldonado, Arturo

2012-01-01

Indium doped zinc oxide [ZnO:In] thin films have been deposited at 430°C on soda-lime glass substrates by the chemical spray technique, starting from zinc acetate and indium acetate. Pulverization of the solution was done by ultrasonic excitation. The variations in the electrical, structural, optical, and morphological characteristics of ZnO:In thin films, as a function of both the water content in the starting solution and the substrate temperature, were studied. The electrical resistivity of ZnO:In thin films is not significantly affected with the increase in the water content, up to 200 mL/L; further increase in water content causes an increase in the resistivity of the films. All films show a polycrystalline character, fitting well with the hexagonal ZnO wurtzite-type structure. No preferential growth in samples deposited with the lowest water content was observed, whereas an increase in water content gave rise to a (002) growth. The surface morphology of the films shows a consistency with structure results, as non-geometrical shaped round grains were observed in the case of films deposited with the lowest water content, whereas hexagonal slices, with a wide size distribution were observed in the other cases. In addition, films deposited with the highest water content show a narrow size distribution. PMID:28817056

Thin Film Photovoltaic Partnership Project | Photovoltaic Research | NREL

Science.gov Websites

Thin Film Photovoltaic Partnership Project Thin Film Photovoltaic Partnership Project NREL's Thin Film Photovoltaic (PV) Partnership Project led R&D on emerging thin-film solar technologies in the National Laboratory developed low-cost transparent encapsulation schemes for CIGS cells that reduced power

Permanent laser conditioning of thin film optical materials

DOEpatents

Wolfe, C.R.; Kozlowski, M.R.; Campbell, J.H.; Staggs, M.; Rainer, F.

1995-12-05

The invention comprises a method for producing optical thin films with a high laser damage threshold and the resulting thin films. The laser damage threshold of the thin films is permanently increased by irradiating the thin films with a fluence below an unconditioned laser damage threshold. 9 figs.

Ordered organic-organic multilayer growth

DOEpatents

Forrest, Stephen R.; Lunt, Richard R.

2016-04-05

An ordered multilayer crystalline organic thin film structure is formed by depositing at least two layers of thin film crystalline organic materials successively wherein the at least two thin film layers are selected to have their surface energies within .+-.50% of each other, and preferably within .+-.15% of each other, whereby every thin film layer within the multilayer crystalline organic thin film structure exhibit a quasi-epitaxial relationship with the adjacent crystalline organic thin film.

Ordered organic-organic multilayer growth

DOEpatents

Forrest, Stephen R; Lunt, Richard R

2015-01-13

An ordered multilayer crystalline organic thin film structure is formed by depositing at least two layers of thin film crystalline organic materials successively wherein the at least two thin film layers are selected to have their surface energies within .+-.50% of each other, and preferably within .+-.15% of each other, whereby every thin film layer within the multilayer crystalline organic thin film structure exhibit a quasi-epitaxial relationship with the adjacent crystalline organic thin film.

Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

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

DeBlase, Catherine R.; Hernández-Burgos, Kenneth; Silberstein, Katharine E.

2015-03-24

Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COFmore » films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.« less

Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

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

DeBlase, Catherine R.; Hernández-Burgos, Kenneth; Silberstein, Katharine E.

2015-02-17

Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COFmore » films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.« less

Functional patterned coatings by thin polymer film dewetting.

PubMed

Telford, Andrew M; Thickett, Stuart C; Neto, Chiara

2017-12-01

An approach for the fabrication of functional polymer surface coatings is introduced, where micro-scale structure and surface functionality are obtained by means of self-assembly mechanisms. We illustrate two main applications of micro-patterned polymer surfaces obtained through dewetting of bilayers of thin polymer films. By tuning the physical and chemical properties of the polymer bilayers, micro-patterned surface coatings could be produced that have applications both for the selective attachment and patterning of proteins and cells, with potential applications as biomaterials, and for the collection of water from the atmosphere. In all cases, the aim is to achieve functional coatings using approaches that are simple to realize, use low cost materials and are potentially scalable. Copyright © 2017 Elsevier Inc. All rights reserved.

Subnanopore filling during water vapor adsorption on microporous silica thin films as seen by low-energy positron annihilation

NASA Astrophysics Data System (ADS)

Ito, Kenji; Yoshimoto, Shigeru; O'Rourke, Brian E.; Oshima, Nagayasu; Kumagai, Kazuhiro

2018-02-01

Positron annihilation lifetime spectroscopy (PALS) using a low-energy positron microbeam extracted into air was applied to elucidating molecular-level pore structures formed in silicon-oxide-backboned microporous thin films under controlled humidity conditions; as a result, a direct observation of the interstitial spaces in the micropores filled with water molecules was achieved. It was demonstrated that PALS using a microbeam extracted into air in combination with water vapor adsorption is a powerful tool for the in-situ elucidation of both open and closed subnanoscaled pores of functional thin materials under practical conditions.

Pore orientation effects on the kinetics of mesostructure loss in surfactant templated titania thin films

DOE PAGES

Das, Saikat; Nagpure, Suraj; Garlapalli, Ravinder K.; ...

2016-12-17

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle x-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonallymore » oriented (o-HCP) thin films (~60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ/mol -1) than on unmodified (128 kJ/mol -1), which implies that the rate difference stems a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (~250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ/mol -1) due to the mix of orientations found in the films. Thus, in conclusion, this kinetic study shows that thin P123- templated o-HCP titania films are not only better able to achieve good orthogonal alignment of 3 the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.« less

Pore orientation effects on the kinetics of mesostructure loss in surfactant templated titania thin films

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

Das, Saikat; Nagpure, Suraj; Garlapalli, Ravinder K.

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle x-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonallymore » oriented (o-HCP) thin films (~60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ/mol -1) than on unmodified (128 kJ/mol -1), which implies that the rate difference stems a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (~250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ/mol -1) due to the mix of orientations found in the films. Thus, in conclusion, this kinetic study shows that thin P123- templated o-HCP titania films are not only better able to achieve good orthogonal alignment of 3 the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.« less

Quantitative Raman characterization of cross-linked collagen thin films as a model system for diagnosing early osteoarthritis

NASA Astrophysics Data System (ADS)

Wang, Chao; Durney, Krista M.; Fomovsky, Gregory; Ateshian, Gerard A.; Vukelic, Sinisa

2016-03-01

The onset of osteoarthritis (OA)in articular cartilage is characterized by degradation of extracellular matrix (ECM). Specifically, breakage of cross-links between collagen fibrils in the articular cartilage leads to loss of structural integrity of the bulk tissue. Since there are no broadly accepted, non-invasive, label-free tools for diagnosing OA at its early stage, Raman spectroscopyis therefore proposed in this work as a novel, non-destructive diagnostic tool. In this study, collagen thin films were employed to act as a simplified model system of the cartilage collagen extracellular matrix. Cross-link formation was controlled via exposure to glutaraldehyde (GA), by varying exposure time and concentration levels, and Raman spectral information was collected to quantitatively characterize the cross-link assignments imparted to the collagen thin films during treatment. A novel, quantitative method was developed to analyze the Raman signal obtained from collagen thin films. Segments of Raman signal were decomposed and modeled as the sum of individual bands, providing an optimization function for subsequent curve fitting against experimental findings. Relative changes in the concentration of the GA-induced pyridinium cross-links were extracted from the model, as a function of the exposure to GA. Spatially resolved characterization enabled construction of spectral maps of the collagen thin films, which provided detailed information about the variation of cross-link formation at various locations on the specimen. Results showed that Raman spectral data correlate with glutaraldehyde treatment and therefore may be used as a proxy by which to measure loss of collagen cross-links in vivo. This study proposes a promising system of identifying onset of OA and may enable early intervention treatments that may serve to slow or prevent osteoarthritis progression.

Elastic and dielectric anisotropy in barium strontium titanate thin films on orthorhombic neodymium gallate substrates

NASA Astrophysics Data System (ADS)

Simon, William Kurt

Functional oxide thin films often focus on standard cubic substrates that impose an equal biaxial plane stress condition (sigma11 = sigma22) to the film. These internal stresses in thin films reach magnitudes not easily achieved in bulk materials and represent an important influence on the properties of thin films. Equal biaxial plane stress is a small sub-set of stress conditions. Anisotropic stress (sigma11 ≠ sigma 22) represents a wide range of influences that can be utilized to manipulate the properties of thin films. To investigate these conditions, heteroepitaxial thin films of paraelectric Ba0.6Sr0.4TiO3 (BST) were deposited on [100] and [110] oriented single crystal NdGaO 3 (NGO) substrates. Films were grown in the thickness range of 25 to 1200 nm by Pulsed Laser Deposition. The films grown on [100]NGO substrates were [110] oriented, while [110]NGO substrates resulted in [100] oriented BST films. The [100]BST films exhibit a small variation of the epitaxial misfit with direction: -2.6% and -2.8% along the [010]BST and [001 ]BST directions respectively. The epitaxial misfit for the [110]BST films show a greater variation with direction; -1.9% and -2.8% along the [1¯10]BST, and [001]BST directions respectively. The interfacial dislocations that form to relieve stress are found to be dependant on the growth orientation of the film and to contribute to the degree of elastic and dielectric anisotropy. The variation of the residual strains, with thickness and direction are correlated to the non-linear dielectric permittivity at 10 GHz. The relative permittivity is seen to vary from 150 to 500 with in-plane direction of a single [110]BST film. Tunabilities in the same film vary from 30 to 54%, with the greater tunability occurring along the directions with greater permittivity. Analysis of the non-linear polarization curves illustrate that the higher order permittivity terms, which are responsible for tunability, are all adversely affected by strain and reach an elastically saturated limit regardless of growth orientation or in-plane direction. Through the use of unequal epitaxial strains, anisotropy is imparted to the otherwise spherically symmetric permittivity tensor. This asymmetry allows a single film to have a variable response and fill a variety of performance requirements in microwave passive devices.

Transverse spin Seebeck effect versus anomalous and planar Nernst effects in Permalloy thin films.

PubMed

Schmid, M; Srichandan, S; Meier, D; Kuschel, T; Schmalhorst, J-M; Vogel, M; Reiss, G; Strunk, C; Back, C H

2013-11-01

Transverse magnetothermoelectric effects are studied in Permalloy thin films grown on MgO and GaAs substrates and compared to those grown on suspended SiN(x) membranes. The transverse voltage along platinum strips patterned on top of the Permalloy films is measured versus the external magnetic field as a function of the angle and temperature gradients. After the identification of the contribution of the planar and anomalous Nernst effects, we find an upper limit for the transverse spin Seebeck effect, which is several orders of magnitude smaller than previously reported.

Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

DOEpatents

Babcock, W.C.; Friesen, D.T.

1988-11-01

Novel semipermeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

DOEpatents

Babcock, Walter C.; Friesen, Dwayne T.

1988-01-01

Novel semiperimeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

Resistance switching in polyvinylidene fluoride (PVDF) thin films

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

Pramod, K.; Sahu, Binaya Kumar; Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in

2015-06-24

Polyvinylidene fluoride (PDVF), one of the best electrically active polymer material & an interesting candidate to address the electrical control of its functional properties like ferroelectricity, piezoelectricity, pyroelectricity etc. In the current work, with the help of spin coater and DC magnetron sputtering techniques, semi-crystallized PVDF thin films prominent in alpha phase is prepared in capacitor like structure and their electrical characterization is emphasized. In current-voltage (I-V) and resistance-voltage (R-V) measurements, clear nonlinearity and resistance switching has been observed for films prepared using 7 wt% 2-butanone and 7 wt% Dimethyl Sulfoxide (DMSO) solvents.

Temperature evolution of the structural properties of monodomain ferroelectric thin film

NASA Astrophysics Data System (ADS)

Janolin, Pierre-Eymeric; Le Marrec, Françoise; Chevreul, Jacques; Dkhil, Brahim

2007-05-01

The structural evolution of epitaxial monodomain (only 180° domains) ferroelectric PbTiO3 thin film has been investigated, using high-resolution, temperature-dependent, x-ray diffraction. The full set of lattice parameters was obtained from room temperature up to 850K. It allowed the calculation of the different strains stored in the film at room temperature, underlying the difference between the mechanical strain and the misfit strain. The evolution of the misfit strain as a function of temperature was also calculated and was found to be consistent with the theoretical temperature-misfit strain phase diagram. These data strongly suggest that the film remains ferroelectric and tetragonal up to 940K.

Bulk photovoltaic effect in epitaxial (K, Nb) substituted BiFeO3 thin films

NASA Astrophysics Data System (ADS)

Agarwal, Radhe; Zheng, Fan; Sharma, Yogesh; Hong, Seungbum; Rappe, Andrew; Katiyar, Ram

We studied the bulk photovoltaic effect in epitaxial (K, Nb) modified BiFeO3 (BKFNO) thin films using theoretical and experimental methods. Epitaxial BKFNO thin films were grown by pulsed laser deposition (PLD). First, we have performed first principles density function theory (DFT) using DFT +U method to calculate electronic band structure, including Hubbard-Ueff (Ueff =U-J) correction into Hamiltonian. The electronic band structure calculations showed a direct band gap at 1.9 eV and a defect level at 1.7 eV (in a 40 atom BKFNO supercell), sufficiently lower in comparison to the experimentally observed values. Furthermore, the piezoforce microscopy (PFM) measurements indicated the presence of striped polydomains in BKFNO thin films. Angle-resolved PFM measurements were also performed to find domain orientation and net polarization directions in these films. The experimental studies of photovoltaic effect in BKNFO films showed a short circuit current of 59 micro amp/cm2 and open circuit voltage of 0.78 V. We compared our experimental results with first principles shift current theory calculations of bulk photovoltaic effect (BPVE).The synergy between theory and experimental results provided a realization of significant role of BPVE in order to understand the photovoltaic mechanism in ferroelectrics.

Domain growth of carbon nanotubes assisted by dewetting of thin catalyst precursor films

NASA Astrophysics Data System (ADS)

Srivastava, Alok Kumar; Sachan, Priyanka; Samanta, Chandan; Mukhopadhyay, Kingsuk; Sharma, Ashutosh

2014-01-01

We explore self-organized dewetting of ultrathin films of a novel metal complex as a one step surface patterning method to create nanoislands of iron, using which spatially separated carbon nanostructures were synthesized. Dewetting of ultrathin metal complex films was induced by two different methods: liquid solvent exposure and thermal annealing to engender surface patterning. For thermal dewetting, thin films of the iron oleate complex were dewetted at high temperature. In the case of liquid solvent assisted dewetting, the metal complex, mixed with a sacrificial polymer (polystyrene) was spin coated as thin films (<40 nm) and then dewetted under an optimal solution mixture consisting of methyl ethyl ketone, acetone and water. The carrier polymer was then selectively removed to produce the iron metal islands. These metal islands were used for selective growth of discrete patches of multiwall CNTs and CNFs by a chemical vapor deposition (CVD) process. Solvent induced dewetting showed clear advantages over thermal dewetting owing to reduced size of catalyst domains formed by dewetting, an improved control over CNT growth as well as in its ability to immobilize the seed particles. The generic solution mediated dewetting and pattern generation in thin films of various catalytic precursors can thus be a powerful method for selective domain growth of a variety of functional nanomaterials.

Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material

NASA Astrophysics Data System (ADS)

Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

2016-01-01

In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material.

PubMed

Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

2016-12-01

In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size.

PubMed

Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

2018-02-16

The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb 2 Te 3 ) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb 2 Te 3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb 2 Te 3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb 2 Te 3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size

NASA Astrophysics Data System (ADS)

Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

2018-02-01

The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb2Te3) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb2Te3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb2Te3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb2Te3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

Resonant infrared matrix-assisted pulsed laser evaporation of TiO2 nanoparticle films

NASA Astrophysics Data System (ADS)

Mayo, Daniel C.; Paul, Omari; Airuoyo, Idemudia J.; Pan, Zhengda; Schriver, Kenneth E.; Avanesyan, Sergey M.; Park, Hee K.; Mu, Richard R.; Haglund, Richard F.

2013-03-01

The successful development of flexible, high performance thin films that are competitive with silicon-based technology will likely require fabricating films of hybrid materials that incorporate nanomaterials, glasses, ceramics, polymers, and thin films. Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is an ideal method for depositing organic materials and nanoparticles with minimal photochemical or photothermal damage to the deposited material. Furthermore, there are many nonhazardous solvents containing chemical functional groups with infrared absorption bands that are accessible using IR lasers. We report here results of recent work in which RIR-MAPLE has been employed successfully to deposit thin films of TiO2 nanoparticles on Si substrates. Using an Er:YAG laser ( λ=2.94 μm), we investigated a variety of MAPLE matrices containing -OH moieties, including water and all four isomers of butyl alcohol. The alcohol isomers are shown to provide effective and relatively nontoxic solvents for use in the RIR-MAPLE process. In addition, we examine the effects of varying concentration and laser fluence on film roughness and surface coverage.

Producing CCD imaging sensor with flashed backside metal film

NASA Technical Reports Server (NTRS)

Janesick, James R. (Inventor)

1988-01-01

A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

CCD imaging sensor with flashed backside metal film

NASA Technical Reports Server (NTRS)

Janesick, James R. (Inventor)

1991-01-01

A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

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

Core-Shell Double Gyroid Structure Formed by Linear ABC Terpolymer Thin Films.

PubMed

Antoine, Ségolène; Aissou, Karim; Mumtaz, Muhammad; Telitel, Siham; Pécastaings, Gilles; Wirotius, Anne-Laure; Brochon, Cyril; Cloutet, Eric; Fleury, Guillaume; Hadziioannou, Georges

2018-05-01

The synthesis and self-assembly in thin-film configuration of linear ABC triblock terpolymer chains consisting of polystyrene (PS), poly(2-vinylpyridine) (P2VP), and polyisoprene (PI) are described. For that purpose, a hydroxyl-terminated PS-b-P2VP (45 kg mol -1 ) building block and a carboxyl-terminated PI (9 kg mol -1 ) are first separately prepared by anionic polymerization, and then are coupled via a Steglich esterification reaction. This quantitative and metal-free catalyst synthesis route reveals to be very interesting since functionalization and purification steps are straightforward, and well-defined terpolymers are produced. A solvent vapor annealing (SVA) process is used to promote the self-assembly of frustrated PS-b-P2VP-b-PI chains into a thin-film core-shell double gyroid (Q 230 , space group: Ia3¯d) structure. As terraces are formed within PS-b-P2VP-b-PI thin films during the SVA process under a CHCl 3 vapor, different plane orientations of the Q 230 structure ((211), (110), (111), and (100)) are observed at the polymer-air interface depending on the film thickness. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low stress polysilicon film and method for producing same

NASA Technical Reports Server (NTRS)

Heuer, Arthur H. (Inventor); Kahn, Harold (Inventor); Yang, Jie (Inventor)

2001-01-01

Multi-layer assemblies of polysilicon thin films having predetermined stress characteristics and techniques for forming such assemblies are disclosed. In particular, a multi-layer assembly of polysilicon thin film may be produced that has a stress level of zero, or substantially so. The multi-layer assemblies comprise at least one constituent thin film having a tensile stress and at least one constituent thin film having a compressive stress. The thin films forming the multi-layer assemblies may be disposed immediately adjacent to one another without the use of intermediate layers between the thin films.

Low stress polysilicon film and method for producing same

NASA Technical Reports Server (NTRS)

Heuer, Arthur H. (Inventor); Kahn, Harold (Inventor); Yang, Jie (Inventor)

2002-01-01

Multi-layer assemblies of polysilicon thin films having predetermined stress characteristics and techniques for forming such assemblies are disclosed. In particular, a multi-layer assembly of polysilicon thin film may be produced that has a stress level of zero, or substantially so. The multi-layer assemblies comprise at least one constituent thin film having a tensile stress and at least one constituent thin film having a compressive stress. The thin films forming the multi-layer assemblies may be disposed immediately adjacent to one another without the use of intermediate layers between the thin films.

Dynamic studies of nano-confined polymer thin films

NASA Astrophysics Data System (ADS)

Geng, Kun

Polymer thin films with the film thickness (h0 ) below 100 nm often exhibit physical properties different from the bulk counterparts. In order to make the best use of polymer thin films in applications, it is important to understand the physical origins of these deviations. In this dissertation, I will investigate how different factors influence dynamic properties of polymer thin films upon nano-confinement, including glass transition temperature (Tg), effective viscosity (etaeff) and self-diffusion coefficient (D ). The first part of this dissertation concerns the impacts of the molecular weight (MW) and tacticity on the Tg's of nano-confined polymer films. Previous experiments showed that the Tg of polymer films could be depressed or increased as h0 decreases. While these observations are usually attributed to the effects of the interfaces, some experiments suggested that MW's and tacticities might also play a role. To understand the effects of these factors, the Tg's of silica-based poly(alpha-methyl styrene) (PalphaMS/SiOx) and poly(methyl methacrylate) (PMMA/SiOx) thin films were studied, and the results suggested that MW's and tacticities influence Tg in nontrivial ways. The second part concerns an effort to resolve the long-standing controversy about the correlation between different dynamics of polymer thin films upon nano-confinement. Firstly, I discuss the experimental results of Tg, D and etaeff of poly(isobutyl methacrylate) films supported by silica (PiBMA/SiOx). Both T g and D were found to be independent of h 0, but etaeff decreased with decreasing h 0. Since both D and etaeff describe transport phenomena known to depend on the local friction coefficient or equivalently the local viscosity, it is questionable why D and etaeff displayed seemingly inconsistent h 0 dependencies. We envisage the different h0 dependencies to be caused by Tg, D and etaeff being different functions of the local T g's (Tg,i) or viscosities (eta i). By assuming a three-layer model, we were able to account for the experimental data and resolve the inconsistency. By extending the same ideas to the analogous data of silica-based polystyrene films (PS/SiOx), we found a resolution to the inconsistency regarding the effects of nano-confinement on the dynamics of polymer thin films.

Miniature hybrid microwave IC's using a novel thin-film technology

NASA Astrophysics Data System (ADS)

Eda, Kazuo; Miwa, Tetsuji; Taguchi, Yutaka; Uwano, Tomoki

1990-12-01

A novel thin-film technology for miniature hybrid microwave ICs is presented. All passive components, such as resistors and capacitors, are fully integrated on ordinary alumina ceramic substrates using the thin-film technology with very high yield. The numbers of parts and wiring processes were significantly reduced. This technology was applied to the fabrication of Ku-band solid-state power amplifiers. This thin-film technology offers the following advantages: (1) a very high yield fabrication process of thin-film capacitor having excellent electrical characteristics in the gigahertz range (Q = 230 at 12 GHz) and reliability: (2) two kinds of thin-film resistors having different temperature coefficients of resistivity and a lift-off process to integrate them with thin-film capacitors; and (3) a matching method using the thin-film capacitor.

Biomimetic Mineralization of Gold Nanoclusters as Multifunctional Thin Films for Glass Nanopore Modification, Characterization, and Sensing.

PubMed

Cao, Sumei; Ding, Shushu; Liu, Yingzi; Zhu, Anwei; Shi, Guoyue

2017-08-01

Hurdles of nanopore modification and characterization restrain the development of glass capillary-based nanopore sensing platforms. In this article, a simple but effective biomimetic mineralization method was developed to decorate glass nanopore with a thin film of bovine serum albumin-protected Au nanocluster (BSA-Au NC). The BSA-Au NC film emitted a strong red fluorescence whereby nondestructive characterization of Au film decorated at the inner surface of glass nanopore can be facilely achieved by a fluorescence microscopy. Besides, the BSA molecules played dual roles in the fabrication of functionalized Au thin film in glass nanopore: they not only directed the synthesis of fluorescent Au thin film but also provided binding sites for recognition, thus achieving synthesis-modification integration. This occurred due to the ionized carboxyl groups (-COO - ) of a BSA coating layer on Au NCs which can interacted with arginine (Arg) via guanidinium groups. The added Arg selectively led to the change in the charge and ionic current of BSA-Au NC film-decorated glass nanopore. Such ionic current responses can be used for quantifying Arg with a detection limit down to 1 fM, which was more sensitive than that of previous sensing systems. Together, the designed method exhibited great promise in providing a facile and controllable solution for glass nanopore modification, characterization, and sensing.

Processing-Structure-Property Relationships in Laser-Annealed PbSe Nanocrystal Thin Films.

PubMed

Treml, Benjamin E; Robbins, Andrew B; Whitham, Kevin; Smilgies, Detlef-M; Thompson, Michael O; Hanrath, Tobias

2015-01-01

As nanocrystal (NC) synthesis techniques and device architectures advance, it becomes increasingly apparent that new ways of connecting NCs with each other and their external environment are required to realize their considerable potential. Enhancing inter-NC coupling by thermal annealing has been a long-standing challenge. Conventional thermal annealing approaches are limited by the challenge of annealing the NC at sufficiently high temperatures to remove surface-bound ligands while at the same time limiting the thermal budget to prevent large-scale aggregation. Here we investigate nonequilibrium laser annealing of NC thin films that enables separation of the kinetic and thermodynamic aspects of nanocrystal fusion. We show that laser annealing of NC assemblies on nano- to microsecond time scales can transform initially isolated NCs in a thin film into an interconnected structure in which proximate dots "just touch". We investigate both pulsed laser annealing and laser spike annealing and show that both annealing methods can produce "confined-but-connected" nanocrystal films. We develop a thermal transport model to rationalize the differences in resulting film morphologies. Finally we show that the insights gained from study of nanocrystal mono- and bilayers can be extended to three-dimensional NC films. The basic processing-structure-property relationships established in this work provide guidance to future advances in creating functional thin films in which constituent NCs can purposefully interact.

Hybrid Surface Acoustic Wave-Electrohydrodynamic Atomization (SAW-EHDA) For the Development of Functional Thin Films.

PubMed

Choi, Kyung Hyun; Kim, Hyun Bum; Ali, Kamran; Sajid, Memoon; Uddin Siddiqui, Ghayas; Chang, Dong Eui; Kim, Hyung Chan; Ko, Jeong Beom; Dang, Hyun Woo; Doh, Yang Hoi

2015-10-19

Conventional surface acoustic wave - electrostatic deposition (SAW-ED) technology is struggling to compete with other thin film fabrication technologies because of its limitation in atomizing high density solutions or solutions with strong inter-particle bonding that requires very high frequency (100 MHz) and power. In this study, a hybrid surface acoustic wave - electrohydrodynamic atomization (SAW-EHDA) system has been introduced to overcome this problem by integrating EHDA with SAW to achieve the deposition of different types of conductive inks at lower frequency (19.8 MHZ) and power. Three materials, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV), Zinc Oxide (ZnO), and Poly(3, 4-ethylenedioxythiophene):Polystyrene Sulfonate ( PSS) have been successfully deposited as thin films through the hybrid SAW-EHDA. The films showed good morphological, chemical, electrical, and optical characteristics. To further evaluate the characteristics of deposited films, a humidity sensor was fabricated with active layer of PSS deposited using the SAW-EHDA system. The response of sensor was outstanding and much better when compared to similar sensors fabricated using other manufacturing techniques. The results of the device and the films' characteristics suggest that the hybrid SAW-EHDA technology has high potential to efficiently produce wide variety of thin films and thus predict its promising future in certain areas of printed electronics.

Growth, characterization and post-processing of inorganic and hybrid organic-inorganic thin films deposited using atomic and molecular layer deposition techniques

NASA Astrophysics Data System (ADS)

Abdulagatov, Aziz Ilmutdinovich

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are advanced thin film coating techniques developed for deposition of inorganic and hybrid organic-inorganic films respectively. Decreasing device dimensions and increasing aspect ratios in semiconductor processing has motivated developments in ALD. The beginning of this thesis will cover study of new ALD chemistry for high dielectric constant Y 2O3. In addition, the feasibility of conducting low temperature ALD of TiN and TiAlN is explored using highly reactive hydrazine as a new nitrogen source. Developments of these ALD processes are important for the electronics industry. As the search for new materials with more advanced properties continues, attention has shifted toward exploring the synthesis of hierarchically nanostructured thin films. Such complex architectures can provide novel functions important to the development of state of the art devices for the electronics industry, catalysis, energy conversion and memory storage as a few examples. Therefore, the main focus of this thesis is on the growth, characterization, and post-processing of ALD and MLD films for fabrication of novel composite (nanostructured) thin films. Novel composite materials are created by annealing amorphous ALD oxide alloys in air and by heat treatment of hybrid organic-inorganic MLD films in inert atmosphere (pyrolysis). The synthesis of porous TiO2 or Al2O3 supported V2O5 for enhanced surface area catalysis was achieved by the annealing of inorganic TiVxOy and AlV xOy ALD films in air. The interplay between phase separation, surface energy difference, crystallization, and melting temperature of individual oxides were studied for their control of film morphology. In other work, a class of novel metal oxide-graphitic carbon composite thin films was produced by pyrolysis of MLD hybrid organic-inorganic films. For example, annealing in argon of titania based hybrid films enabled fabrication of thin films of intimately mixed TiO2 and nanographitized carbon. The graphitized carbon in the film was formed as a result of the removal of hydrogen by pyrolysis of the organic constituency of the MLD film. The presence of graphitic carbon allowed a 14 orders of magnitude increase in the electrical conductivity of the composite material compared fully oxidized rutile TiO 2.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker.

PubMed

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Marty, Jean Louis; Hayat, Akhtar

2016-10-06

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett- Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker

PubMed Central

Nawaz, Muhammad Azhar Hayat; Rauf, Sajid; Catanante, Gaelle; Nawaz, Mian Hasnain; Nunes, Gilvanda; Louis Marty, Jean; Hayat, Akhtar

2016-01-01

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications. PMID:27782067

Probing molecular orientations in thin films by x-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Li, Y.; Li, P.; Lu, Z.-H.

2018-03-01

A great number of functional organic molecules in active thin-film layers of optoelectronic devices have highly asymmetric structures, such as plate-like, rod-like, etc. This makes molecular orientation an important aspect in thin-films as it can significantly affect both the optical and electrical performance of optoelectronic devices. With a combination of in-situ ultra violet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS) investigations for organic molecules having a broad range of structural properties, we discovered a rigid connection of core levels and frontier highest occupied molecular orbital levels at organic interfaces. This finding opens up opportunities of using X-ray photoemission spectroscopy as an alternative tool to UPS for providing an easy and unambiguous data interpretation in probing molecular orientations.

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

Evolution of diffraction and self-diffraction phenomena in thin films of Gelite Bloom/Hibiscus Sabdariffa

NASA Astrophysics Data System (ADS)

Cano-Lara, Miroslava; Severiano-Carrillo, Israel; Trejo-Durán, Mónica; Alvarado-Méndez, Edgar

2017-09-01

In this work, we present a study of non-linear optical response in thin films elaborated with Gelite Bloom and extract of Hibiscus Sabdariffa. Non-linear refraction and absorption effects were studied experimentally (Z-scan technique) and numerically, by considering the transmittance as non-linear absorption and refraction contribution. We observe large phase shifts to far field, and diffraction due to self-phase modulation of the sample. Diffraction and self-diffraction effects were observed as time function. The aim of studying non-linear optical properties in thin films is to eliminate thermal vortex effects that occur in liquids. This is desirable in applications such as non-linear phase contrast, optical limiting, optics switches, etc. Finally, we find good agreement between experimental and theoretical results.

Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T

NASA Astrophysics Data System (ADS)

Niu, Wei; Wang, Xuefeng; Gao, Ming; Xia, Zhengcai; Du, Jun; Nie, Yuefeng; Song, Fengqi; Xu, Yongbing; Zhang, Rong

2017-05-01

We report on the temperature and field dependence of resistance of La0.7Sr0.3MnO3 thin films over a wide temperature range and in pulsed magnetic fields up to 60 T. The epitaxial La0.7Sr0.3MnO3 thin films were deposited by laser molecular beam epitaxy. High magnetic field magnetoresistance curves were fitted by the Brillouin function, which indicated the existence of magnetically polarized regions and the underlying hopping mechanism. The unsaturated magnetoconductance was the most striking finding observed in pulsed magnetic fields up to 60 T. These observations can deepen the fundamental understanding of the colossal magnetoresistance in manganites with strong correlation of transport properties and magnetic ordering.

Development of nanostructured ZnO thin film via electrohydrodynamic atomization technique and its photoconductivity characteristics.

PubMed

Duraisamy, Navaneethan; Kwon, Ki Rin; Jo, Jeongdai; Choi, Kyung-Hyun

2014-08-01

This article presents the non-vacuum technique for the preparation of nanostructured zinc oxide (ZnO) thin film on glass substrate through electrohydrodynamic atomization (EHDA) technique. The detailed process parameters for achieving homogeneous ZnO thin films are clearly discussed. The crystallinity and surface morphology of ZnO thin film are investigated by X-ray diffraction and field emission scanning electron microscopy. The result shows that the deposited ZnO thin film is oriented in the wurtzite phase with void free surface morphology. The surface roughness of deposited ZnO thin film is found to be ~17.8 nm. The optical properties of nanostructured ZnO thin films show the average transmittance is about 90% in the visible region and the energy band gap is found to be 3.17 eV. The surface chemistry and purity of deposited ZnO thin films are analyzed by fourier transform infrared and X-ray photoelectron spectroscopy, conforming the presence of Zn-O in the deposited thin films without any organic moiety. The photocurrent measurement of nanostructured ZnO thin film is examined in the presence of UV light illumination with wavelength of 365 nm. These results suggest that the deposited nanostructured ZnO thin film through EHDA technique possess promising applications in the near future.

Universal Pinning Energy Barrier for Driven Domain Walls in Thin Ferromagnetic Films

NASA Astrophysics Data System (ADS)

Jeudy, V.; Mougin, A.; Bustingorry, S.; Savero Torres, W.; Gorchon, J.; Kolton, A. B.; Lemaître, A.; Jamet, J.-P.

2016-07-01

We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes.

Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates

DTIC Science & Technology

2014-09-01

function of heating rate. The FWHM of the Ill PZT texture components is sim 2978 Journal of the American Ceramic Society Mhin et al. Vol. 97, No. 9...Z39.18 ABSTRACT Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates Report Title The crystallization of lead zirconate...phase influencing texture evolution. The results suggest that PZT nucleates directly on Pt, which explains the observation of a more highly oriented

Coarsening and pattern formation during true morphological phase separation in unstable thin films under gravity

NASA Astrophysics Data System (ADS)

Kumar, Avanish; Narayanam, Chaitanya; Khanna, Rajesh; Puri, Sanjay

2017-12-01

We address in detail the problem of true morphological phase separation (MPS) in three-dimensional or (2 +1 )-dimensional unstable thin liquid films (>100 nm) under the influence of gravity. The free-energy functionals of these films are asymmetric and show two points of common tangency, which facilitates the formation of two equilibrium phases. Three distinct patterns formed by relative preponderance of these phases are clearly identified in "true MPS". Asymmetricity induces two different pathways of pattern formation, viz., defect and direct pathway for true MPS. The pattern formation and phase-ordering dynamics have been studied using statistical measures such as structure factor, correlation function, and growth laws. In the late stage of coarsening, the system reaches into a scaling regime for both pathways, and the characteristic domain size follows the Lifshitz-Slyozov growth law [L (t ) ˜t1 /3] . However, for the defect pathway, there is a crossover of domain growth behavior from L (t ) ˜t1 /4→t1 /3 in the dynamical scaling regime. We also underline the analogies and differences behind the mechanisms of MPS and true MPS in thin liquid films and generic spinodal phase separation in binary mixtures.

On the interplay between phonon-boundary scattering and phonon-point-defect scattering in SiGe thin films

NASA Astrophysics Data System (ADS)

Iskandar, A.; Abou-Khalil, A.; Kazan, M.; Kassem, W.; Volz, S.

2015-03-01

This paper provides theoretical understanding of the interplay between the scattering of phonons by the boundaries and point-defects in SiGe thin films. It also provides a tool for the design of SiGe-based high-efficiency thermoelectric devices. The contributions of the alloy composition, grain size, and film thickness to the phonon scattering rate are described by a model for the thermal conductivity based on the single-mode relaxation time approximation. The exact Boltzmann equation including spatial dependence of phonon distribution function is solved to yield an expression for the rate at which phonons scatter by the thin film boundaries in the presence of the other phonon scattering mechanisms. The rates at which phonons scatter via normal and resistive three-phonon processes are calculated by using perturbation theories with taking into account dispersion of confined acoustic phonons in a two dimensional structure. The vibrational parameters of the model are deduced from the dispersion of confined acoustic phonons as functions of temperature and crystallographic direction. The accuracy of the model is demonstrated with reference to recent experimental investigations regarding the thermal conductivity of single-crystal and polycrystalline SiGe films. The paper describes the strength of each of the phonon scattering mechanisms in the full temperature range. Furthermore, it predicts the alloy composition and film thickness that lead to minimum thermal conductivity in a single-crystal SiGe film, and the alloy composition and grain size that lead to minimum thermal conductivity in a polycrystalline SiGe film.

Determination and analysis of non-linear index profiles in electron-beam-deposited MgOAl2O3ZrO2 ternary composite thin-film optical coatings

NASA Astrophysics Data System (ADS)

Sahoo, N. K.; Thakur, S.; Senthilkumar, M.; Das, N. C.

2005-02-01

Thickness-dependent index non-linearity in thin films has been a thought provoking as well as intriguing topic in the field of optical coatings. The characterization and analysis of such inhomogeneous index profiles pose several degrees of challenges to thin-film researchers depending upon the availability of relevant experimental and process-monitoring-related information. In the present work, a variety of novel experimental non-linear index profiles have been observed in thin films of MgOAl2O3ZrO2 ternary composites in solid solution under various electron-beam deposition parameters. Analysis and derivation of these non-linear spectral index profiles have been carried out by an inverse-synthesis approach using a real-time optical monitoring signal and post-deposition transmittance and reflection spectra. Most of the non-linear index functions are observed to fit polynomial equations of order seven or eight very well. In this paper, the application of such a non-linear index function has also been demonstrated in designing electric-field-optimized high-damage-threshold multilayer coatings such as normal- and oblique-incidence edge filters and a broadband beam splitter for p-polarized light. Such designs can also advantageously maintain the microstructural stability of the multilayer structure due to the low stress factor of the non-linear ternary composite layers.

Hydrogen anion and subgap states in amorphous In-Ga-Zn-O thin films for TFT applications

NASA Astrophysics Data System (ADS)

Bang, Joonho; Matsuishi, Satoru; Hosono, Hideo

2017-06-01

Hydrogen is an impurity species having an important role in the physical properties of semiconductors. Despite numerous studies, the role of hydrogen in oxide semiconductors remains an unsolved puzzle. This situation arises from insufficient information about the chemical state of the impurity hydrogen. Here, we report direct evidence for anionic hydrogens bonding to metal cations in amorphous In-Ga-Zn-O (a-IGZO) thin films for thin-film transistors (TFT) applications and discuss how the hydrogen impurities affect the electronic structure of a-IGZO. Infrared absorption spectra of self-standing a-IGZO thin films prepared by sputtering reveal the presence of hydrogen anions as a main hydrogen species (concentration is ˜1020 cm-3) along with the hydrogens in the form of the hydroxyl groups (˜1020 cm-3). Density functional theory calculations show that bonds between these hydride ions with metal centers give rise to subgap states above the top of the valence band, implying a crucial role of anionic hydrogen in the negative bias illumination stress instability commonly observed in a-IGZO TFTs.

Local dynamics of glass-forming polystyrene thin films from atomistic simulation

NASA Astrophysics Data System (ADS)

Zhou, Yuxing; Milner, Scott

Despite a wide technological application ranging from protective coatings to organic solar cells, there still no consensus on the mechanism for the glass transition in polymer thin films a manifestation of the infamous glass problem under confinement. Many experimental and computational studies have observed a large deviation of nanoscale dynamical properties in thin films from the corresponding properties in bulk. In this work, we perform extensive united-atom simulations on atactic polystyrene free-standing thin films near the glass transition temperature and focus on the effect of free surface on the local dynamics. We study the segmental dynamics as a function of distance from the surface for different temperatures, from which relaxation time and thereby local Tg is obtained for each layer. We find the dynamics near free surface is not only enhanced but becomes less strongly temperature dependent as Tg is approached compared to the bulk. We find an increasing length scale associated with mobility propagation from the free surface as temperature decreases, but no correlation between local structure and enhanced relaxation rates near the surface, consistent with studies on bead-spring chains.

First-principles Studies of Ferroelectricity in BiMnO3 Thin Films

NASA Astrophysics Data System (ADS)

Wang, Yun-Peng; Cheng, Hai-Ping

The ferroelectricity in BiMnO3 thin films is a long-standing problem. We employed a first-principles density functional theory with inclusion of the local Hubbard Coulomb (U) and exchange (J) terms. The parameters U and J are optimized to reproduce the atomic structure and the energy gap of bulk C2/c BiMnO3. With these optimal U and J parameters, the calculated ferromagnetic Curie temperature and lattice dynamics properties agree with experiments. We then studied the ferroelectricity in few-layer BiMnO3 thin films on SrTiO3(001) substrates. Our calculations identified ferroelectricity in monolayer, bilayer and trilayer BiMnO3 thin films. We find that the energy barrier for 90° rotation of electric polarization is about 3 - 4 times larger than that of conventional ferroelectric materials. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences (BES), under Contract No. DE-FG02-02ER45995. Computations were done using the utilities of the National Energy Research Scientific Computing Center (NERSC).

Compositional dependence of magnetic anisotropy in chemically synthesized Co3- x Fe x O4 (0 ≤ x ≤ 2)

NASA Astrophysics Data System (ADS)

Hayashi, Kensuke; Yamada, Keisuke; Shima, Mutsuhiro

2018-01-01

Magnetic anisotropy of Co3- x Fe x O4 (CFO, 0 ≤ x ≤ 2) thin-film and powder samples prepared by a sol-gel method has been investigated as a function of Fe composition x. Structural analyses by X-ray diffraction show that CFO powder samples exhibit diffraction peaks associated with the spinel structure when x < 2, while CFO thin-film samples with thickness of 130-510 nm yield the peaks when 0 ≤ x ≤ 2. CFO thin-film samples are highly (111)-oriented with the Lotgering factor greater than 0.9 when 0.6 ≤ x ≤ 1.3. The magnetic anisotropy constant K 1 of CFO powder samples estimated from their room-temperature hysteresis loops yields a minimum when x = 0.9. Relatively large in-plane magnetic anisotropy (K eff = 5.7 × 105 erg/cm3) is observed for the CFO thin-film sample when x = 1.3. With increasing x, the magnetic easy axis of the spinel CFO changes from 〈111〉 to 〈100〉 when x = 0.9.

Biocompatible cephalosporin-hydroxyapatite-poly(lactic-co-glycolic acid)-coatings fabricated by MAPLE technique for the prevention of bone implant associated infections

NASA Astrophysics Data System (ADS)

Rădulescu, Dragoş; Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Grumezescu, Alexandru Mihai; Socol, Gabriel; Oprea, Alexandra Elena; Rădulescu, Marius; Surdu, Adrian; Trusca, Roxana; Rădulescu, Radu; Chifiriuc, Mariana Carmen; Stan, Miruna S.; Constanda, Sabrina; Dinischiotu, Anca

2016-06-01

In this study we aimed to obtain functionalized thin films based on hydroxyapatite/poly(lactic-co-glycolic acid) (HAp/PLGA) containing ceftriaxone/cefuroxime antibiotics (ATBs) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The prepared thin films were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), selected area electron diffraction (SAED), and infra red (IR) analysis. HAp/PLGA/ATBs thin films sustained the growth of human osteoblasts, proving their good biocompatibility. The microscopic evaluation and the culture-based quantitative assay of the E. coli biofilm development showed that the thin films inhibited the initial step of microbial attachment as well as the subsequent colonization and biofilm development on the respective surfaces. This study demonstrates that MAPLE technique could represent an appealing technique for the fabrication of antibiotics-containing polymeric implant coatings. The bioevaluation results recommend this type of surfaces for the prevention of bone implant microbial contamination and for the enhanced stimulation of the implant osseointegration process.

Reduction of Defects on Microstructure Aluminium Nitride Using High Temperature Annealing Heat Treatment

NASA Astrophysics Data System (ADS)

Tanasta, Z.; Muhamad, P.; Kuwano, N.; Norfazrina, H. M. Y.; Unuh, M. H.

2018-03-01

Aluminium Nitride (AlN) is a ceramic 111-nitride material that is used widely as components in functional devices. Besides good thermal conductivity, it also has a high band gap in emitting light which is 6 eV. AlN thin film is grown on the sapphire substrate (0001). However, lattice mismatch between both materials has caused defects to exist along the microstructure of AlN thin films. The defects have affected the properties of Aluminium Nitride. Annealing heat treatment has been proved by the previous researcher to be the best method to improve the microstructure of Aluminium Nitride thin films. Hence, this method is applied at four different temperatures for two hour. The changes of Aluminium Nitride microstructures before and after annealing is observed using Transmission Electron Microscope. It is observed that inversion domains start to occur at temperature of 1500 °C. Convergent Beam Electron Diffraction pattern simulation has confirmed the defects as inversion domain. Therefore, this paper is about to extract the matters occurred during the process of producing high quality Aluminium Nitride thin films and the ways to overcome this problem.

Ligand-surface interactions and surface oxidation of colloidal PbSe quantum dots revealed by thin-film positron annihilation methods

NASA Astrophysics Data System (ADS)

Shi, Wenqin; Eijt, Stephan W. H.; Suchand Sandeep, C. S.; Siebbeles, Laurens D. A.; Houtepen, Arjan J.; Kinge, Sachin; Brück, Ekkes; Barbiellini, Bernardo; Bansil, Arun

2016-02-01

Positron Two Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) measurements reveal modifications of the electronic structure and composition at the surfaces of PbSe quantum dots (QDs), deposited as thin films, produced by various ligands containing either oxygen or nitrogen atoms. In particular, the 2D-ACAR measurements on thin films of colloidal PbSe QDs capped with oleic acid ligands yield an increased intensity in the electron momentum density (EMD) at high momenta compared to PbSe quantum dots capped with oleylamine. Moreover, the EMD of PbSe QDs is strongly affected by the small ethylenediamine ligands, since these molecules lead to small distances between QDs and favor neck formation between near neighbor QDs, inducing electronic coupling between neighboring QDs. The high sensitivity to the presence of oxygen atoms at the surface can be also exploited to monitor the surface oxidation of PbSe QDs upon exposure to air. Our study clearly demonstrates that positron annihilation spectroscopy applied to thin films can probe surface transformations of colloidal semiconductor QDs embedded in functional layers.

Chemical bath deposited and dip coating deposited CuS thin films - Structure, Raman spectroscopy and surface study

NASA Astrophysics Data System (ADS)

Tailor, Jiten P.; Khimani, Ankurkumar J.; Chaki, Sunil H.

2018-05-01

The crystal structure, Raman spectroscopy and surface microtopography study on as-deposited CuS thin films were carried out. Thin films deposited by two techniques of solution growth were studied. The thin films used in the present study were deposited by chemical bath deposition (CBD) and dip coating deposition techniques. The X-ray diffraction (XRD) analysis of both the as-deposited thin films showed that both the films possess covellite phase of CuS and hexagonal unit cell structure. The determined lattice parameters of both the films are in agreement with the standard JCPDS as well as reported data. The crystallite size determined by Scherrer's equation and Hall-Williamsons relation using XRD data for both the as-deposited thin films showed that the respective values were in agreement with each other. The ambient Raman spectroscopy of both the as-deposited thin films showed major emission peaks at 474 cm-1 and a minor emmision peaks at 265 cm-1. The observed Raman peaks matched with the covellite phase of CuS. The atomic force microscopy of both the as-deposited thin films surfaces showed dip coating thin film to be less rough compared to CBD deposited thin film. All the obtained results are presented and deliberated in details.

Synthesis and characterization of cobalt doped nickel oxide thin films by spray pyrolysis method

NASA Astrophysics Data System (ADS)

Sathisha, D.; Naik, K. Gopalakrishna

2018-05-01

Cobalt (Co) doped nickel oxide (NiO) thin films were deposited on glass substrates at a temperature of about 400 °C by spray pyrolysis method. The effect of Co doping concentration on structural, optical and compositional properties of NiO thin films was investigated. X-ray diffraction result shows that the deposited thin films are polycrystalline in nature. Surface morphologies of the deposited thin films were observed by FESEM and AFM. EDS spectra showed the incorporation of Co dopants in NiO thin films. Optical properties of the grown thin films were characterized by UV-visible spectroscopy. It was found that the optical band gap energy and transmittance of the films decrease with increasing Co doping concentration.

Insight into the epitaxial encapsulation of Pd catalysts in an oriented metalloporphyrin network thin film for tandem catalysis.

PubMed

Vohra, M Ismail; Li, De-Jing; Gu, Zhi-Gang; Zhang, Jian

2017-06-14

A palladium catalyst (Pd-Cs) encapsulated metalloporphyrin network PIZA-1 thin film with bifunctional properties has been developed through a modified epitaxial layer-by-layer encapsulation approach. Combining the oxidation activity of Pd-Cs and the acetalization activity of the Lewis acidic sites in the PIZA-1 thin film, this bifunctional catalyst of the Pd-Cs@PIZA-1 thin film exhibits a good catalytic activity in a one-pot tandem oxidation-acetalization reaction. Furthermore, the surface components can be controlled by ending the top layer with different precursors in the thin film preparation procedures. The catalytic performances of these thin films with different surface composites were studied under the same conditions, which showed different reaction conversions. The result revealed that the surface component can influence the catalytic performance of the thin films. This epitaxial encapsulation offers a good understanding of the tandem catalysis for thin film materials and provides useful guidance to develop new thin film materials with catalytic properties.

Exciting transition metal doped dilute magnetic thin films: MgO:Er and ZnO:Er

NASA Astrophysics Data System (ADS)

Ćakıcı, T.; Sarıtaş, S.; Muǧlu, G. Merhan; Yıldırım, M.

2017-02-01

Erbium doped MgO and doped ZnO thin films have reasonably important properties applications in spintronic devices. These films were synthesized on glass substrates by Chemical Spray Pyrolysis (CSP) method. In the literature there has been almost no report on preparation of MgO:Er dilute magnetic thin films by means of CSP. Because doped thin films show different magnetic behaviors, depending upon the type of magnetic material ions, concentration of them, synthesis route and experimental conditions, synthesized MgO:Er and ZnO:Er films were compared to thin film properties. Optical analyses of the synthesized thin films were examined spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. Structural analysis of the thin films was examined by using XRD, Raman Analysis, FE-SEM, EDX and AFM techniques. Also, magnetic properties of the MgO:Er and ZnO:Er films were investigated by vibrating sample magnetometer (VSM) which show that diamagnetic behavior of the MgO:Er thin film and ferromagnetic (FM) behavior of the ZnO:Er film were is formed.

Piezoelectric response and electrical properties of Pb(Zr1-xTix)O3 thin films: The role of imprint and composition

NASA Astrophysics Data System (ADS)

Cornelius, T. W.; Mocuta, C.; Escoubas, S.; Merabet, A.; Texier, M.; Lima, E. C.; Araujo, E. B.; Kholkin, A. L.; Thomas, O.

2017-10-01

The compositional dependence of the piezoelectric properties of self-polarized PbZr1-xTixO3 (PZT) thin films deposited on Pt/TiO2/SiO2/Si substrates (x = 0.47, 0.49 and 0.50) was investigated by in situ synchrotron X-ray diffraction and electrical measurements. The latter evidenced an imprint effect in the studied PZT films, which is pronounced for films with the composition of x = 0.50 and tends to disappear for x = 0.47. These findings were confirmed by in situ X-ray diffraction along the crystalline [100] and [110] directions of the films with different compositions revealing asymmetric butterfly loops of the piezoelectric strain as a function of the electric field; the asymmetry is more pronounced for the PZT film with a composition of x = 0.50, thus indicating a higher built-in electric field. The enhancement of the dielectric permittivity and the effective piezoelectric coefficient at compositions around the morphotropic phase boundary were interpreted in terms of the polarization rotation mechanism and the monoclinic phase in the studied PZT thin films.

Improved performance of Mg-Y alloy thin film switchable mirrors after coating with a superhydrophobic surface

NASA Astrophysics Data System (ADS)

La, Mao; Zhou, Huaijuan; Li, Ning; Xin, Yunchuan; Sha, Ren; Bao, Shanhu; Jin, Ping

2017-05-01

The magnesium based switchable mirrors can reversibly change their optical properties between the transparent and the reflective state as a result of hydrogenation and dehydrogenation. These films can potentially be applied as new energy-saving windows, by controlling the transmittance of solar radiation through the regulation of their reflective state. In this study, magnesium-yttrium (Mg-Y) alloy thin films were prepared using a DC magnetron sputtering method. However, the luminous transmittance in the transparent state and the switching durability of switchable mirrors are too poor to satisfy practical demands. In order to improve the films switching durability, luminous transmittance and the surface functionalization, polytetrafluoroethylene (PTFE) was coated with thermal vacuum deposition for use as the top layer of Mg-Y/Pd switchable mirrors. The PTFE layer had a porous network structure and exhibited a superhydrophobic surface with a water contact angle of approximately 152°. By characterization, PTFE thin films shows the excellent protection role against the oxidization of Mg, the switching durability of the films were improved 3 times, and also shows the antireflection role the luminous transmission of films was enhanced by 7% through the top covered with PTFE.

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1992-01-01

Thin film ferroelectric capacitors comprising a ferroelectric film sandwiched between electrodes for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode. The anneal is done so as to form the interface between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550 to 600 C for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the nonswitching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the nonswitching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1994-01-01

Thin film ferroelectric capacitors (10) comprising a ferroelectric film (18) sandwiched between electrodes (16 and 20) for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode (20). The anneal is done so as to form the interface (22) between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550.degree. to 600.degree. C. for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the non-switching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the non-switching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Preparation and properties of sol-gel derived PZT thin films for decoupling capacitor applications

NASA Astrophysics Data System (ADS)

Schwartz, R. W.; Dimos, D.; Lockwood, S. J.; Torres, V. M.

The use of ceramic thin films as decoupling capacitors offers the possibility of capacitor integration within the integrated circuit (IC) package and, potentially, directly onto the IC itself. Since these configurations minimize series inductance, higher operational speeds are possible. In the present study, the authors have investigated the dielectric and leakage characteristics of sol-gel PZT films. For compositions near the morphotropic phase boundary, dielectric constants of 1000, and loss tangents of about 0.02, are observed. The current-voltage behavior of the capacitors is characterized by a non-linear response, and significant asymmetry in both the leakage and breakdown characteristics as a function of bias sign is observed. Breakdown fields for PZT 53/47 thin films are typically approximately 800 kV/cm at 25 C. The authors have also studied the effects of La and Nb dopant additions and alternate firing strategies on film leakage characteristics. Donor doping at 2 - 5 mol % lowers leakage currents by a factor of 10(exp 3). For films prepared by a multilayering approach, firing each layer to crystallization results in leakage currents that are a factor of 10(exp 2) lower than films prepared by the standard process.

Plasma polymerized high energy density dielectric films for capacitors

NASA Technical Reports Server (NTRS)

Yamagishi, F. G.

1983-01-01

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

SU-E-T-163: Thin-Film Organic Photocell (OPV) Properties in MV and KV Beams for Dosimetry Applications.

PubMed

Ng, S K; Hesser, J; Zhang, H; Gowrisanker, S; Yakushevich, S; Shulhevich, Y; Abkai, C; Wack, L; Zygmanski, P

2012-06-01

To characterize dosimetric properties of low-cost thin film organic-based photovoltaic (OPV) cells to kV and MV x-ray beams for their usage as large area dosimeter for QA and patient safety monitoring device. A series of thin film OPV cells of various areas and thicknesses were irradiated with MV beams to evaluate the stability and reproducibility of their response, linearity and sensitivity to absorbed dose. The OPV response to x-rays of various linac energies were also characterized. Furthermore the practical (clinical) sensitivity of the cells was determined using IMRT sweeping gap test generated with various gap sizes. To evaluate their potential usage in the development of low cost kV imaging device, the OPV cells were irradiated with kV beam (60-120 kVp) from a fluoroscopy unit. Photocell response to the absorbed dose was characterized as a function of the organic thin film thickness and size, beam energy and exposure for kV beams as well. In addition, photocell response was determined with and without thin plastic scintillator. Response of the OPV cells to the absorbed dose from kV and MV beams are stable and reproducible. The photocell response was linearly proportional to the size and about slightly decreasing with the thickness of the organic thin film, which agrees with the general performance of the photocells in visible light. The photocell response increases as a linear function of absorbed dose and x-ray energy. The sweeping gap tests performed showed that OPV cells have sufficient practical sensitivity to measured MV x-ray delivery with gap size as small as 1 mm. With proper calibration, the OPV cells could be used for online radiation dose measurement for quality assurance and patient safety purposes. Their response to kV beam show promising potential in development of low cost kV radiation detection devices. © 2012 American Association of Physicists in Medicine.

YSZ thin films with minimized grain boundary resistivity

DOE PAGES

Mills, Edmund M.; Kleine-Boymann, Matthias; Janek, Juergen; ...

2016-03-31

In recent years, interface engineering of solid electrolytes has been explored to increase their ionic conductivity and improve the performance of solid oxide fuel cells and other electrochemical power sources. It has been observed that the ionic conductivity of epitaxially grown thin films of some electrolytes is dramatically enhanced, which is often attributed to effects (e.g. strain-induced mobility changes) at the heterophase boundary with the substrate. Still largely unexplored is the possibility of manipulation of grain boundary resistivity in polycrystalline solid electrolyte films, clearly a limiting factor in their ionic conductivity. Here in this paper, we report that the ionicmore » conductivity of yttria stabilized zirconia thin films with nano-columnar grains grown on a MgO substrate nearly reaches that of the corresponding single crystal when the thickness of the films becomes less than roughly 8 nm (smaller by a factor of three at 500 °C). Using impedance spectroscopy, the grain boundary resistivity was probed as a function of film thickness. The resistivity of the grain boundaries near the film–substrate interface and film surface (within 4 nm of each) was almost entirely eliminated. This minimization of grain boundary resistivity is attributed to Mg 2+ diffusion from the MgO substrate into the YSZ grain boundaries, which is supported by time of flight secondary ion mass spectroscopy measurements. We suggest grain boundary “design” as an attractive method to obtain highly conductive solid electrolyte thin films.« less

Phonon scattering mechanisms dictating the thermal conductivity of lead zirconate titanate (PbZr 1- xTi xO 3) thin films across the compositional phase diagram

DOE PAGES

Foley, Brian M.; Paisley, Elizabeth A.; DiAntonio, Christopher; ...

2017-05-23

This paper represents a thorough investigation of the thermal conductivity (κ) in both thin film and bulk PbZr 1–xTi xO 3 (PZT) across the compositional phase diagram. Given the technological importance of PZT as a superb piezoelectric and ferroelectric material in devices and systems impacting a wide array of industries, this research serves to fill the gap in knowledge regarding the thermal properties. The thermal conductivities of both thin film and bulk PZT are found to vary by a considerable margin as a function of composition x. Additionally, we observe a discontinuity in κ in the vicinity of the morphotropicmore » phase boundary (MPB, x = 0.48) where there is a 20%–25% decrease in κ in our thin film data, similar to that found in literature data for bulk PZT. The comparison between bulk and thin film materials highlights the sensitivity of κ to size effects such as film thickness and grain size even in disordered alloy/solid-solution materials. A model for the thermal conductivity of PZT as a function of composition (κ(x)) is presented, which enables the application of the virtual crystal approximation for alloy-type material systems with very different crystals structures, resulting in differing temperature trends for κ. We show that in the case of crystalline solid-solutions where the thermal conductivity of one of the parent materials exhibits glass-like temperature trends the compositional dependence of thermal conductivity is relatively constant for most values of x. Finally, this is in stark contrast with the typical trends of thermal conductivity with x in alloys, where the thermal conductivity increases dramatically as the composition of the alloy or solid-solution approaches that of a pure parent materials (i.e., as x = 0 or 1).« less

Phonon scattering mechanisms dictating the thermal conductivity of lead zirconate titanate (PbZr 1- xTi xO 3) thin films across the compositional phase diagram

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

Foley, Brian M.; Paisley, Elizabeth A.; DiAntonio, Christopher

This paper represents a thorough investigation of the thermal conductivity (κ) in both thin film and bulk PbZr 1–xTi xO 3 (PZT) across the compositional phase diagram. Given the technological importance of PZT as a superb piezoelectric and ferroelectric material in devices and systems impacting a wide array of industries, this research serves to fill the gap in knowledge regarding the thermal properties. The thermal conductivities of both thin film and bulk PZT are found to vary by a considerable margin as a function of composition x. Additionally, we observe a discontinuity in κ in the vicinity of the morphotropicmore » phase boundary (MPB, x = 0.48) where there is a 20%–25% decrease in κ in our thin film data, similar to that found in literature data for bulk PZT. The comparison between bulk and thin film materials highlights the sensitivity of κ to size effects such as film thickness and grain size even in disordered alloy/solid-solution materials. A model for the thermal conductivity of PZT as a function of composition (κ(x)) is presented, which enables the application of the virtual crystal approximation for alloy-type material systems with very different crystals structures, resulting in differing temperature trends for κ. We show that in the case of crystalline solid-solutions where the thermal conductivity of one of the parent materials exhibits glass-like temperature trends the compositional dependence of thermal conductivity is relatively constant for most values of x. Finally, this is in stark contrast with the typical trends of thermal conductivity with x in alloys, where the thermal conductivity increases dramatically as the composition of the alloy or solid-solution approaches that of a pure parent materials (i.e., as x = 0 or 1).« less

Thin-film optical initiator

DOEpatents

Erickson, Kenneth L.

2001-01-01

A thin-film optical initiator having an inert, transparent substrate, a reactive thin film, which can be either an explosive or a pyrotechnic, and a reflective thin film. The resultant thin-film optical initiator system also comprises a fiber-optic cable connected to a low-energy laser source, an output charge, and an initiator housing. The reactive thin film, which may contain very thin embedded layers or be a co-deposit of a light-absorbing material such as carbon, absorbs the incident laser light, is volumetrically heated, and explodes against the output charge, imparting about 5 to 20 times more energy than in the incident laser pulse.

Phase diagrams of nonionic foam films: construction by means of disjoining pressure versus thickness curves.

PubMed

Stubenrauch, Cosima; Kashchiev, Dimo; Strey, Reinhard

2004-12-01

The thickness h of foam films can be measured as a function of the disjoining pressure Pi using a thin film pressure balance. Experimental Pi-h curves of foam films stabilized with nonionic surfactants measured at various concentrations resemble the p-V(m) isotherms of real gases measured at various temperatures (p is the pressure and V(m) is the molar volume of the gas). This observation led us to adopt the van der Waals approach for describing real gases to thin foam films, where the thickness h takes the role of V(m) and the disjoining pressure Pi replaces the ordinary pressure p. Our analysis results in a phase diagram for a thin foam film with spinodal, binodal as well as a critical point. The thicker common black film corresponds to the gas phase and the compact Newton black film for which the two surfaces are in direct contact corresponds to the dense liquid. We show that the tuning parameter for the phase behavior of the film is the surface charge density, which means that Pi-h curves should not be referred to as isotherms. In addition to the equilibrium properties the driving force for the phase transition from a common black film to a Newton black film or vice versa is calculated. We discuss how this transition can be controlled experimentally.

Fabrication and etching processes of silicon-based PZT thin films

NASA Astrophysics Data System (ADS)

Zhao, Hongjin; Liu, Yanxiang; Liu, Jianshe; Ren, Tian-Ling; Liu, Li-Tian; Li, Zhijian

2001-09-01

Lead-zirconate-titanate (PZT) thin films on silicon were prepared by a sol-gel method. Phase characterization and crystal orientation of the films were investigated by x-ray diffraction analysis (XRD). It was shown that the PZT thin films had a perfect perovskite structure after annealed at a low temperature of 600 degrees C. PZT thin films were chemically etched using HCl/HF solution through typical semiconductor lithographic process, and the etching condition was optimized. The scanning electron microscopy results indicated that the PZT thin film etching problem was well solved for the applications of PZT thin film devices.

Photocurrent spectroscopy of pentacene thin film transistors

NASA Astrophysics Data System (ADS)

Breban, Mihaela

We demonstrate the application of photocurrent modulation spectroscopy in characterizing the performance of organic thin-film transistors. A parallel analysis of the direct current and photocurrent voltage characteristics provides a model free determination of the field-effect mobility and the density of free carriers in the transistor channel as a function of the applied gate voltage. Applying this technique to pentacene thin-film transistors demonstrates that the mobility increases as V1/3g . The free-carrier density is approximately 1/10 of the expected capacitive charge, and the mobility increases monotonically with the free carrier density, consistent with the trap and release model of transport. Also, the modulated photocurrent spectroscopy can be used as a probe of defect states in pentacene thin film transistors, measuring simultaneously the magnitude and the phase of the photocurrent as a function of the modulation frequency. This is accomplished by modeling the photo-carrier generation process as exciton dissociation via interaction with localized traps. Experimental data reveal a Gaussian distribution of localized states centered around 0.3 eV above the highest occupied molecular orbital. We also investigated the effect of the gate dielectric material with our probe and found that the position of the extracted Gaussian slightly shifts, consistent with the expected image charge effect for Pn through the dielectric substrate. Also shifts in the Gaussian position for samples fabricated with variable deposition conditions are correlated with changes in Pn morphology. The morphological differences between Pn films were also detected in current-voltage characteristics and photocurrent spectra. However, the origin of the ubiquitous 0.3 eV defect in Pn seems to be unrelated to structural differences in Pn films.

A mechanism of Cu work function reduction in CsBr/Cu photocathodes

DOE PAGES

Halliday, M. T. E.; Hess, W. P.; Shluger, A. L.

2016-02-15

Thin films of CsBr deposited on Cu(100) have been proposed as next-generation photocathode materials for applications in particle accelerators and free-electron lasers. However, the mechanisms underlying an improved photocathode performance remain poorly understood. We present density Functional Theory (DFT) calculations of the work function reduction following the application of CsBr thin film coatings to Cu photocathodes. The effects of structure and van der Waals forces are examined. Calculations suggest that CsBr films can reduce the work function by around 1.5 eV, which would explain the exponential increase in quantum efficiency (QE) of coated vs. uncoated photocathodes. In conclusion, a modelmore » explaining experimentally observed laser activation of photocathode is provided whereby the photo-induced creation of di-vacancies at the surface, and their subsequent diffusion throughout the lattice and segregation at the interface leads to a further increase in QE after a period of laser irradiation.« less

Investigations of Si Thin Films as Anode of Lithium-Ion Batteries

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

Wu, Qingliu; Shi, Bing; Bareño, Javier

Amorphous silicon thin films having various thicknesses were investigated as a negative electrode material for lithium-ion batteries. Electrochemical characterization of the 20 nm thick thin silicon film revealed a very low first cycle Coulombic efficiency, which can be attributed to the silicon oxide layer formed on both the surface of the as-deposited Si thin film and the interface between the Si and the substrate. Among the investigated films, the 100 nm Si thin film demonstrated the best performance in terms of first cycle efficiency and cycle life. Observations from scanning electron microscopy demonstrated that the generation of cracks was inevitablemore » in the cycled Si thin films, even as the thickness of the film was as little as 20 nm, which was not predicted by previous modeling work. However, the cycling performance of the 20 and 100 nm silicon thin films was not detrimentally affected by these cracks. The poor capacity retention of the 1 mu m silicon thin film was attributed to the delamination.« less

Pentacene-based organic thin film transistors, integrated circuits, and active matrix displays on polymeric substrates

NASA Astrophysics Data System (ADS)

Sheraw, Christopher Duncan

2003-10-01

Organic thin film transistors are attractive candidates for a variety of low cost, large area commercial electronics including smart cards, RF identification tags, and flat panel displays. Of particular interest are high performance organic thin film transistors (TFTs) that can be fabricated on flexible polymeric substrates allowing low-cost, lightweight, rugged electronics such as flexible active matrix displays. This thesis reports pentacene organic thin film transistors fabricated on flexible polymeric substrates with record performance, the fastest photolithographically patterned organic TFT integrated circuits on polymeric substrates reported to date, and the fabrication of the organic TFT backplanes used to build the first organic TFT-driven active matrix liquid crystal display (AMLCD), also the first AMLCD on a flexible substrate, ever reported. In addition, the first investigation of functionalized pentacene derivatives used as the active layer in organic thin film transistors is reported. A low temperature (<110°C) process technology was developed allowing the fabrication of high performance organic TFTs, integrated circuits, and large TFT arrays on flexible polymeric substrates. This process includes the development of a novel water-based photolithographic active layer patterning process using polyvinyl alcohol that allows the patterning of organic semiconductor materials for elimination of active layer leakage current without causing device degradation. The small molecule aromatic hydrocarbon pentacene was used as the active layer material to fabricate organic TFTs on the polymeric material polyethylene naphthalate with field-effect mobility as large as 2.1 cm2/V-s and on/off current ratio of 108. These are the best values reported for organic TFTs on polymeric substrates and comparable to organic TFTs on rigid substrates. Analog and digital integrated circuits were also fabricated on polymeric substrates using pentacene TFTs with propagation delay as low as 38 musec and clocked digital circuits that operated at 1.1 kHz. These are the fastest photolithographically patterned organic TFT circuits on polymeric substrates reported to date. Finally, 16 x 16 pentacene TFT pixel arrays were fabricated on polymeric substrates and integrated with polymer dispersed liquid crystal to build an AMLCD. The pixel arrays showed good optical response to changing data signals when standard quarter-VGA display waveforms were applied. This result marks the first organic TFT-driven active matrix liquid crystal display ever reported as well as the first active matrix liquid crystal display on a flexible polymeric substrate. Lastly, functionalized pentacene derivatives were used as the active layer in organic thin film transistor materials. Functional groups were added to the pentacene molecule to influence the molecular ordering so that the amount of pi-orbital overlap would be increased allowing the potential for improved field-effect mobility. The functionalization of these materials also improves solubility allowing for the possibility of solution-processed devices and increased oxidative stability. Organic thin film transistors were fabricated using five different functionalized pentacene active layers. Devices based on the pentacene derivative triisopropylsilyl pentacene were found to have the best performance with field-effect mobility as large as 0.4 cm 2/V-s.

System for measuring film thickness

DOEpatents

Batishko, Charles R.; Kirihara, Leslie J.; Peters, Timothy J.; Rasmussen, Donald E.

1990-01-01

A system for determining the thicknesses of thin films of materials exhibiting fluorescence in response to exposure to excitation energy from a suitable source of such energy. A section of film is illuminated with a fixed level of excitation energy from a source such as an argon ion laser emitting blue-green light. The amount of fluorescent light produced by the film over a limited area within the section so illuminated is then measured using a detector such as a photomultiplier tube. Since the amount of fluorescent light produced is a function of the thicknesses of thin films, the thickness of a specific film can be determined by comparing the intensity of fluorescent light produced by this film with the intensity of light produced by similar films of known thicknesses in response to the same amount of excitation energy. The preferred embodiment of the invention uses fiber optic probes in measuring the thicknesses of oil films on the operational components of machinery which are ordinarily obscured from view.

Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

PubMed Central

Buck, Maren E.

2010-01-01

We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example, onto the surfaces of planar substrates containing holes or pores) to fabricate suspended polymer membranes and other film-functionalized interfaces. In addition to planar, two-dimensional freestanding films, this approach can be used to fabricate and isolate three-dimensional freestanding membranes (e.g., curved films or tubes) by layer-by-layer assembly on, and subsequent lift-off from, the surfaces of topologically complex substrates (e.g., the curved ends of glass tubing, etc.). The results of this investigation, when combined, suggest the basis of methods for the fabrication of stable, chemically-reactive, and flexible polymer thin films and membranes of potential utility in a variety of fundamental and applied contexts. PMID:20857952

Understanding the Formation of Kinetically Stable Compounds and the Development of Thin Film Pair Distribution Function Analysis

NASA Astrophysics Data System (ADS)

Wood, Suzannah Rebecca

Navigating the synthesis landscape poses many challenges when developing novel solid state materials. Advancements in both synthesis and characterization are necessary to facilitate the targeting of specific materials. This dissertation discusses the formation of chalcogenide heterostructures and their properties in the first part and the development of thin film pair distribution function analysis (tfPDF) in the second part. The heterostructures were formed by the self-assembly of designed precursors deposited by physical vapor deposition in a modulated elemental reactants approach, which provides the control and predictability to synthesis. Specifically, a series of (BiSe)1+delta(TiSe2) n, where n = 2,3,&4, were synthesized to explore the extent of charge transfer from the BiSe to TiSe2 layers. To further explore the role Bi plays in charge donation, a family of structurally similar compounds, (Bix Sn1-xSe)1+deltaTiSe2, where 0≥x≥1, were synthesized and characterized. Electrical measurements show doping efficiency decreases as x increases, correlated with the structural distortion and the formation of periodic antiphase boundaries containing Bi-Bi pairs. The first heterostructures composed of three unique structural types were synthesized and Bi2Se3 layer thickness was used to tune electrical properties and further explore charge transfer. To better understand the potential energy landscape on which these kinetically stable compounds exist, two investigations were undertaken. The first was a study of the formation and subsequent decomposition of [(BiSe)1+delta]n(TiSe2)n compounds, where n= 2&3, the second an investigation of precursor structure for thermodynamically stable FeSb2 and kinetically stable FeSb3. The second section describes the development of thin film pair distribution function analysis, a technique in which total scattering data for pair distribution function (PDF) analysis is obtained from thin films, suitable for local structure analysis. This study illustrates how analysis of the local structure in amorphous precursor films can help to understand the crystallization processes of metastable phases and enables a range of new local structure studies of thin films. tfPDF was then demonstrated on In-Ga-O film materials and compared to traditional powder PDF analysis. This highlights differences between the products, and the utility of tfPDF to determined structural features of amorphous materials. This dissertation includes previously published and unpublished co-authored materials.

Low-Cost Detection of Thin Film Stress during Fabrication

NASA Technical Reports Server (NTRS)

Nabors, Sammy A.

2015-01-01

NASA's Marshall Space Flight Center has developed a simple, cost-effective optical method for thin film stress measurements during growth and/or subsequent annealing processes. Stress arising in thin film fabrication presents production challenges for electronic devices, sensors, and optical coatings; it can lead to substrate distortion and deformation, impacting the performance of thin film products. NASA's technique measures in-situ stress using a simple, noncontact fiber optic probe in the thin film vacuum deposition chamber. This enables real-time monitoring of stress during the fabrication process and allows for efficient control of deposition process parameters. By modifying process parameters in real time during fabrication, thin film stress can be optimized or controlled, improving thin film product performance.

A thin film nitinol heart valve.

PubMed

Stepan, Lenka L; Levi, Daniel S; Carman, Gregory P

2005-11-01

In order to create a less thrombogenic heart valve with improved longevity, a prosthetic heart valve was developed using thin film nitinol (NiTi). A "butterfly" valve was constructed using a single, elliptical piece of thin film NiTi and a scaffold made from Teflon tubing and NiTi wire. Flow tests and pressure readings across the valve were performed in vitro in a pulsatile flow loop. Bio-corrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material's in vivo biocompatibility, thin film nitinol was implanted in pigs using stents covered with thin film NiTi. Flow rates and pressure tracings across the valve were comparable to those through a commercially available 19 mm Perimount Edwards tissue valve. No signs of corrosion were present on thin film nitinol samples after immersion in Hank's solution for one month. Finally, organ and tissue samples explanted from four pigs at 2, 3, 4, and 6 weeks after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation. Although long term testing is still necessary, thin film NiTi may be very well suited for use in artificial heart valves.

The effect of thin film morphology on the electrochemical performance of Cu-Sn anode for lithium rechargeable batteries.

PubMed

Polat, B D; Keleş, O

2014-05-01

We investigate the anode performance of non ordered and ordered nanostructured Cu-Sn thin films deposited via electron beam deposition technique. The ordered nanostructured Cu-Sn thin film having nano-porosities was fabricated using an oblique (co)deposition technique. Our results showed that the nano structured Cu-Sn thin film containing Cu-Sn nanorods had higher initial anodic capacity (790 mA h g(-)) than that of the non ordered thin film (330 mA h g(-)). But the capacity of the ordered nanostructured Cu-Sn thin film diminished after the first cycle and a steady state capacity value around 300 mA h g(-) is sustainable in following up to 80th cycle, which is attributed to the composition and morphology of the thin film. The presence of copper containing Sn nanorods leading to form nano-porosities as interstitial spaces among them, enhanced lithium ions movement within thin film and increased the thin film tolerance against the stress generated because of the drastic volume change occurred during lithiation-delithiation processes; hence, homogenously distributed porosities increased the cycle life of the thin film.

Specific considerations for obtaining appropriate La1-xSrxGa1-yMgyO3-δ thin films using pulsed-laser deposition and its influence on the performance of solid-oxide fuel cells

NASA Astrophysics Data System (ADS)

Hwang, Jaeyeon; Lee, Heon; Lee, Jong-Ho; Yoon, Kyung Joong; Kim, Hyoungchul; Hong, Jongsup; Son, Ji-Won

2015-01-01

To obtain La1-xSrxGa1-yMgyO3-δ (LSGM) thin films with the appropriate properties, pulsed-laser deposition (PLD) is employed, and specific considerations regarding control of the deposition parameters is investigated. It is demonstrated that with a target of stoichiometric composition, appropriate LSGM thin films cannot be produced because of the deviation of the composition from the target to the thin film. Only after adjusting the target composition an LSGM thin film with an appropriate composition and phase can be obtained. The optimized LSGM thin film possesses an electrical conductivity close to that of the bulk LSGM. In contrast, non-optimized thin films do not yield any measurable electrical conductivity. The impact of the optimization of the LSGM thin-film electrolyte on the cell performance is quite significant, in that a solid-oxide fuel cell (SOFC) with an optimized LSGM thin-film electrolyte produces a maximum power density of 1.1 W cm-2 at 600 °C, whereas an SOFC with a non-optimal LSGM thin-film electrolyte is not operable.

Ultra Uniform Pb0.865La0.09(Zr0.65Ti0.35)O3 Thin Films with Tunable Optical Properties Fabricated via Pulsed Laser Deposition

PubMed Central

Jiang, Shenglin; Huang, Chi; Gu, Honggang; Liu, Shiyuan; Zhu, Shuai; Li, Ming-Yu; Yao, Lingmin; Wu, Yunyi; Zhang, Guangzu

2018-01-01

Ferroelectric thin films have been utilized in a wide range of electronic and optical applications, in which their morphologies and properties can be inherently tuned by a qualitative control during growth. In this work, we demonstrate the evolution of the Pb0.865La0.09(Zr0.65Ti0.35)O3 (PLZT) thin films on MgO (200) with high uniformity and optimized optical property via the controls of the deposition temperatures and oxygen pressures. The perovskite phase can only be obtained at the deposition temperature above 700 °C and oxygen pressure over 50 Pa due to the improved crystallinity. Meanwhile, the surface morphologies gradually become smooth and compact owing to spontaneously increased nucleation sites with the elevated temperatures, and the crystallization of PLZT thin films also sensitively respond to the oxygen vacancies with the variation of oxygen pressures. Correspondingly, the refractive indices gradually develop with variations of the deposition temperatures and oxygen pressures resulted from the various slight loss, and the extinction coefficient for each sample is similarly near to zero due to the relatively smooth morphology. The resulting PLZT thin films exhibit the ferroelectricity, and the dielectric constant sensitively varies as a function of electric filed, which can be potentially applied in the electronic and optical applications. PMID:29596398

Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

NASA Astrophysics Data System (ADS)

Huang, Chieh-Szu; Chang, Ming-Chuan; Huang, Cheng-Liang; Lin, Shih-kang

2016-12-01

Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu2+ and Ce2+, are commonly used for red-emitting phosphors. Mg2TiO4 inverse spinel has been reported as a promising matrix material for "RE-free" red light luminescent material. In this paper, Mg2TiO4 inverse spinel is investigated using both experimental and theoretical approaches. The Mg2TiO4 thin films were deposited on Si (100) substrates using either spin-coating with the sol-gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg2TiO4 thin films were characterized. In addition, the atomistic model of the Mg2TiO4 inverse spinel was constructed, and the electronic band structure of Mg2TiO4 was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg2TiO4 luminance material as well as its optimal thin-film processing conditions were comprehensively reported.

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

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

Subramanyam, Guru, E-mail: gsubramanyam1@udayton.edu; Cole, M. W., E-mail: melanie.w.cole.civ@mail.mil; Sun, Nian X.

2013-11-21

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstratedmore » in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.« less

Preparation of nickel oxide thin films at different annealing temperature by sol-gel spin coating method

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

Abdullah, M. A. R., E-mail: ameerridhwan89@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com

2016-07-06

Preparation of NiO thin films at different annealing temperature by sol-gel method was conducted to synthesize the quality of the surface thin films. The effects of annealing temperature on the surface topology were systematically investigated. Our studies confirmed that the surface roughness of the thin films was increased whenever annealing temperature was increase. NiO thin films morphology structure analysis was confirmed by field emission scanning electron microscope. Surface roughness of the thin films was investigated by atomic force microscopy.

Thin-film metal coated insulation barrier in a Josephson tunnel junction. [Patent application

DOEpatents

Hawkins, G.A.; Clarke, J.

1975-10-31

A highly stable, durable, and reproducible Josephson tunnel junction consists of a thin-film electrode of a hard superconductor, a thin oxide insulation layer over the electrode constituting a Josephson tunnel junction barrier, a thin-film layer of stabilizing metal over the barrier, and a second thin-film hard superconductive electrode over the stabilizing film. The thin stabilizing metal film is made only thick enough to limit penetration of the electrode material through the insulation layer so as to prevent a superconductive short.

[Spectral emissivity of thin films].

PubMed

Zhong, D

2001-02-01

In this paper, the contribution of multiple reflections in thin film to the spectral emissivity of thin films of low absorption is discussed. The expression of emissivity of thin films derived here is related to the thin film thickness d and the optical constants n(lambda) and k(lambda). It is shown that in the special case d-->infinity the emissivity of thin films is equivalent to that of the bulk material. Realistic numerical and more precise general numerical results for the dependence of the emissivity on d, n(lambda) and k(lambda) are given.

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition.

PubMed

Yoo, Young Jin; Lee, Gil Ju; Jang, Kyung-In; Song, Young Min

2017-08-29

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.  We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.  Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

Temperature dependent optical properties of ZnO thin film using ellipsometry and photoluminescence

NASA Astrophysics Data System (ADS)

Bouzourâa, M.-B.; Battie, Y.; Dalmasso, S.; Zaïbi, M.-A.; Oueslati, M.; En Naciri, A.

2018-05-01

We report the temperature dependence of the dielectric function, the exciton binding energy and the electronic transitions of crystallized ZnO thin film using spectroscopic ellipsometry (SE) and photoluminescence (PL). ZnO layers were prepared by sol-gel method and deposited on crystalline silicon (Si) by spin coating technique. The ZnO optical properties were determined between 300 K and 620 K. Rigorous study of optical responses was achieved in order to demonstrate the quenching exciton of ZnO as a function of temperature. Numerical technique named constrained cubic splines approximation (CCS), Tauc-Lorentz (TL) and Tanguy dispersion models were selected for the ellipsometry data modeling in order to obtain the dielectric function of ZnO. The results reveals that the exciton bound becomes widely flattening at 470 K on the one hand, and on the other that the Tanguy dispersion law is more appropriate for determining the optical responses of ZnO thin film in the temperature range of 300 K-420 K. The Tauc-Lorentz, for its part, reproduces correctly the ZnO dielectric function in 470 K-620 K temperature range. The temperature dependence of the electronic transition given by SE and PL shows that the exciton quenching was observed in 420 K-∼520 K temperature range. This quenching effect can be explained by the equilibrium between the Coulomb force of exciton and its kinetic energy in the film. The kinetic energy was found to induce three degrees of freedom of the exciton.

Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

NASA Technical Reports Server (NTRS)

Parmar, D. S.; Holmes, H. K.

1993-01-01

Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

Giant surfactants of poly(ethylene oxide)- b-polystyrene-(molecular nanoparticle): nanoparticle-driven self-assembly with sub-10-nm nanostructures in thin films

NASA Astrophysics Data System (ADS)

Hsu, Chih-Hao; Lin, Zhiwei; Dong, Xue-Hui; Hsieh, I.-Fan; Cheng, Stephen Z. D.

2014-03-01

Giant surfactants are built upon precisely attaching shape- and volume-persistent molecular nanoparticles (MNP) to polymeric flexible tails. The unique class of self-assembling materials, giant surfactants, has been demonstrated to form self-assembled ordered nanostructures, and their self-assembly behaviors are remarkably sensitive to primary chemical structures. In this work, two sets of giant surfactants with functionalized MNP attached to diblock copolymer tails were studied in thin films. Carboxylic acid-functionalized [60]fullerene (AC60) tethered with PEO- b-PS (PEO-PS-AC60) represents an ABA' (hydrophilic-hydrophobic-hydrophilic) giant surfactant, and fluoro-functionalized polyhedral oligomeric silsesquioxane (FPOSS) tethered with PEO- b-PS (PEO-PS-FPOSS) represents an ABC (hydrophilic-hydrophobic-omniphobic) one. The dissimilar chemical natures of the MNPs result in different arrangement of MNPs in self-assembled structures, the dispersion of AC60 in PEO domain and the single domain of FPOSS. Moreover, the chemically bonded MNPs could induce the originally disordered small molecular PEO- b-PS to form ordered cylindrical and lamellar structure, as evidenced by TEM and GISAXS, leading to sub-10-nm nanostructures of copolymer in the thin film state.

Effect of Substrate Roughness on Adhesion and Structural Properties of Ti-Ni Shape Memory Alloy Thin Film.

PubMed

Kim, Donghwan; Lee, Hyunsuk; Bae, Joohyeon; Jeong, Hyomin; Choi, Byeongkeun; Nam, Taehyun; Noh, Jungpil

2018-09-01

Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

The Tuning of Optical Properties of Nanoscale MOFs-Based Thin Film through Post-Modification.

PubMed

Yin, Wenchang; Tao, Cheng-An; Zou, Xiaorong; Wang, Fang; Qu, Tianlian; Wang, Jianfang

2017-08-29

Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH₂-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH₂-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index ( n eff ) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices.

The Tuning of Optical Properties of Nanoscale MOFs-Based Thin Film through Post-Modification

PubMed Central

Zou, Xiaorong; Wang, Fang; Qu, Tianlian; Wang, Jianfang

2017-01-01

Optical properties, which determine the application of optical devices in different fields, are the most significant properties of optical thin films. In recent years, Metal-organic framework (MOF)-based optical thin films have attracted increasing attention because of their novel optical properties and important potential applications in optical and photoelectric devices, especially optical thin films with tunable optical properties. This study reports the first example of tuning the optical properties of a MOF-based optical thin film via post-modification. The MOF-based optical thin film was composed of NH2-MIL-53(Al) nanorods (NRs) (MIL: Materials from Institute Lavoisier), and was constructed via a spin-coating method. Three aldehydes with different lengths of carbon chains were chosen to modify the MOF optical thin film to tune their optical properties. After post-modification, the structural color of the NH2-MIL-53(Al) thin film showed an obvious change from purple to bluish violet and cyan. The reflection spectrum and the reflectivity also altered in different degrees. The effective refractive index (neff) of MOFs thin film can also be tuned from 1.292 to 1.424 at a wavelength of 750 nm. The success of tuning of the optical properties of MOFs thin films through post-modification will make MOFs optical thin films meet different needs of optical properties in various optical and optoelectronic devices. PMID:28850057

Surface Functionalization of WO3 Thin Films with (3-Aminopropyl)triethoxysilane and Succinic Anhydride

NASA Astrophysics Data System (ADS)

Ta, Thi Kieu Hanh; Tran, Thi Nhu Hoa; Tran, Quang Minh Nhat; Pham, Duy Phong; Pham, Kim Ngoc; Cao, Thi Thanh; Kim, Yong Soo; Tran, Dai Lam; Ju, Heongkyu; Phan, Bach Thang

2017-06-01

We report effects of oxygen plasma treatment on the surface functionalization of WO3 thin films with (3-aminopropyl)triethoxysilane (APTES) and succinic anhydride (SA). X-ray diffraction and x-ray photoelectron spectroscopy results indicate the existence of the WO3 phase. Fourier transform infrared spectroscopy measurement shows clear bands at 1040 cm-1 (Si-O-Si), 1556 cm-1 (N-H), 1655 cm-1 (C=O), 2937 cm-1 (C-H) and 3298 cm-1 (N-H), confirming the surface functionalization efficiency enhanced by prior treatment of oxygen plasma. It thus follows that the prior oxygen plasma treatment activates hydroxylation with more -OH groups on the WO3 surface, which can pave a highly efficient way to the surface functionalization by APTES and SA.

Temperature dependence of LRE-HRE-TM thin films

NASA Astrophysics Data System (ADS)

Li, Zuoyi; Cheng, Xiaomin; Lin, Gengqi; Li, Zhen; Huang, Zhixin; Jin, Fang; Wang, Xianran; Yang, Xiaofei

2003-04-01

Temperature dependence of the properties of RE-TM thin films is very important for MO recording. In this paper, we studied the temperature dependence of the magnetic and magneto-optical properties of the amorphous LRE-HRE-TM single layer thin films and LRE-HRE-TM/HRE-TM couple-bilayered thin films. For LRE-HRE-TM single layer thin films, the temperature dependence of the magnetization was investigated by using the mean field theory. The experimental and theoretical results matched very well. With the LRE substitution in HRE-TM thin film, the compensation temperature Tcomp decreased and the curie temperature Tc remained unchanged. Kerr rotation angle became larger and the saturation magnetization Ms at room temperature increased. For LRE-HRE-TM/HRE-TM couple-bilayered thin films, comparisons of the temperature dependences of the coercivities and Kerr rotation angles were made between isolated sublayers and couple-bilayered thin film.

Surface proton transport of fully protonated poly(aspartic acid) thin films on quartz substrates

NASA Astrophysics Data System (ADS)

Nagao, Yuki; Kubo, Takahiro

2014-12-01

Thin film structure and the proton transport property of fully protonated poly(aspartic acid) (P-Asp100) have been investigated. An earlier study assessed partially protonated poly(aspartic acid), highly oriented thin film structure and enhancement of the internal proton transport. In this study of P-Asp100, IR p-polarized multiple-angle incidence resolution (P-MAIR) spectra were measured to investigate the thin film structure. The obtained thin films, with thicknesses of 120-670 nm, had no oriented structure. Relative humidity dependence of the resistance, proton conductivity, and normalized resistance were examined to ascertain the proton transport property of P-Asp100 thin films. The obtained data showed that the proton transport of P-Asp100 thin films might occur on the surface, not inside of the thin film. This phenomenon might be related with the proton transport of the biological system.

Thin film superconductor magnetic bearings

DOEpatents

Weinberger, Bernard R.

1995-12-26

A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

Structural, optical and vibrational properties of Cr2O3 with ferromagnetic and antiferromagnetic order: A combined experimental and density functional theory study

NASA Astrophysics Data System (ADS)

Larbi, T.; Ouni, B.; Gantassi, A.; Doll, K.; Amlouk, M.; Manoubi, T.

2017-12-01

Chromium oxide (Cr2O3) thin films have been synthesized on glass substrates by the spray pyrolysis technique. The structural, morphological and optical properties of the sample have been studied by X-ray diffraction (XRD), Raman spectroscopy, FTIR spectroscopy, scanning probe microscopy and UV-vis spectroscopy respectively. X-ray diffraction results reveal that as deposited film is polycrystalline with a rhombohedral corundum structure and a preferential orientation of the crystallites along the (1 0 4) direction. IR and Raman spectra were recorded in the 100-900 cm-1 range and the observed modes were analysed and assigned to different normal modes of vibration. The direct optical band gap energy value calculated from the transmittance spectra of as-deposited thin film is about 3.38 eV. We employ first principles calculations based on density functional theory (DFT) with the B3LYP hybrid functional and a coupled perturbed Hartree-Fock/Kohn-Sham approach (CPHF/KS). We study the electronic structure, optimum geometry, and IR and Raman spectra of ferromagnetically and antiferromagnetically ordered Cr2O3. The computed results are consistent with the experimental measurements, and provide complete vibrational assignment, for the characterization of Cr2O3 thin film materials which can be used in photocatalysis and gas sensors.

Metal Induced Growth of Si Thin Films and NiSi Nanowires

DTIC Science & Technology

2010-02-25

Zinc Oxide Over MIG Silicon- We have been studying the formation of ZnO films by RF sputtering. Part of this study deals with...about 50 nm. 15. SUBJECT TERMS Thin film silicon, solar cells, thin film transistors , nanowires, metal induced growth 16. SECURITY CLASSIFICATION...to achieve, µc-Si is more desirable than a-Si due to its increased mobility. Thin film µc-Si is also a popular material for thin film transistors

NMR characterization of thin films

DOEpatents

Gerald II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

2010-06-15

A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

NMR characterization of thin films

DOEpatents

Gerald, II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

2008-11-25

A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

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.

Sensitivity control of optical fiber biosensors utilizing turnaround point long period gratings with self-assembled polymer coatings

NASA Astrophysics Data System (ADS)

Gifford, Erika; Wang, Z.; Ramachandran, S.; Heflin, J. R.

2007-09-01

Ionic self-assembled multilayers (ISAMs) adsorbed on long period fiber gratings (LPGs) can serve as an inexpensive, robust, portable, biosensor platform. The ISAM technique is a layer-by-layer deposition technique that creates thin films on the nanoscale level. The combination of ISAMs with LPGs yields exceptional sensitivity of the optical fiber transmission spectrum. We have shown theoretically that the resonant wavelength shift for a thin-film coated LPG can be caused by the variation of the film's refractive index and/or the variation of the thickness of the film. We have experimentally demonstrated that the deposition of nm-thick ISAM films on LPGs induces shifts in the resonant wavelength of > 1.6 nm per nm of thin film. It has also been shown that the sensitivity of the LPG to the thickness of the ISAM film increases with increased film thickness. We have further demonstrated that ISAM-coated LPGs can function effectively as biosensors by using the biotin-streptavidin system and by using the Bacillus anthracis (Anthrax) antibody- PA (Protective Antigen) system. Experiments have been successfully performed in both air and solution, which illustrates the versatility of the biosensor. The results confirm that ISAM-LPGs yield a reusable, thermally-stable, and robust platform for designing and building efficient optical biosensors.

Thermally Switchable Thin Films of an ABC Triblock Copolymer of Poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate)

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

Zhang, Shanju; Liu, Zhan; Bucknall, David G.

2011-01-01

The thermo-responsive behavior of polymer films consisting of novel linear triblock copolymers of poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) (PnBuMA-PMMA-P2FEMA) are reported using differential scanning calorimetry (DSC), atomic forcing microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contacting angle (CA) measurements. The surface morphology, wettability and chemical structure of thin films of these triblock copolymers on silicon wafers as a function of temperature have been investigated. It has been shown that the wettability of the films is thermally switchable. Detailed structural analysis shows that thermo-responsive surface composition changes are produced. The underlying mechanism of the thermoresponsive behavior is discussed.

Bandgap tuning in highly c-axis oriented Zn1-xMgxO thin films

NASA Astrophysics Data System (ADS)

Kumar, Parmod; Malik, Hitendra K.; Ghosh, Anima; Thangavel, R.; Asokan, K.

2013-06-01

We propose Mg doping in zinc oxide (ZnO) films for realizing wider optical bandgap in highly c-axis oriented Zn1-xMgxO (0 ≤ x ≤ 0.3) thin films. A remarkable enhancement of 25% in the bandgap by 30% Mg doping was achieved. The bandgap was tuned between 3.25 eV (ZnO) and 4.06 eV (Zn0.7Mg0.3O), which was further confirmed by density functional theory based wien2k simulation employing a combined generalized gradient approximation with scissor corrections. The change of stress and crystallite size in these films were found to be the causes for the observed blueshift in the bandgap.

Linear Arrangement of Motor Protein on a Mechanically Deposited Fluoropolymer Thin Film

NASA Astrophysics Data System (ADS)

Suzuki, Hitoshi; Oiwa, Kazuhiro; Yamada, Akira; Sakakibara, Hitoshi; Nakayama, Haruto; Mashiko, Shinro

1995-07-01

Motor protein molecules such as heavy meromyosin (HMM), one of the major components of skeletal muscle, were arranged linearly on a mechanically deposited fluoropolymer thin film substrate in order to regulate the direction of movement generated by the motor protein. The fluoropolymer film consisted of many linear parallel ridges whose heights and widths were 10 to 20 nm and 10 to 100 nm, respectively. The fluoropolymer ridges adsorbed HMM molecules that were applied onto the film. Actin filaments labeled with rhodamine-phalloidin were observed under a fluorescence microscope moving linearly on the HMM-coated ridges. The observation indicates that HMM molecules were aligned on the fluoropolymer ridges while retaining their function. The velocity of actin movement was measured in this system.

Effect of mechanical strain on mobility of polycrystalline silicon thin-film transistors fabricated on stainless steel foil

NASA Astrophysics Data System (ADS)

Kuo, Po-Chin; Jamshidi-Roudbari, Abbas; Hatalis, Miltiadis

2007-12-01

The effect of uniaxial tensile strain parallel to the channel on mobility of polycrystalline silicon thin-film transistors (TFTs) on stainless steel foil has been investigated. The electron mobility increases by 20% while the hole mobility decreases by 6% as the strain increases to 0.5%, and both followed by saturation as the strain increases further. The off current decreases for both types of TFTs under strain. All TFTs remained functional at the applied strain of 1.13%.

A general strategy for hybrid thin film fabrication and transfer onto arbitrary substrates.

PubMed

Zhang, Yong; Magan, John J; Blau, Werner J

2014-04-28

The development of thin film-based structures/devices often requires thin films to be transferred onto arbitrary substrates/surfaces. Controllable and non-destructive transfer method, although highly desired, remains quite challenging. Here we report a general method for fabrication and transfer of hybrid (ultra)thin films. The proposed solution-based in-situ transfer method shows not only its robust ability for thin film transfer onto arbitrary substrates but also its highly controlled and non-destructive characteristic. With a hole structure as the support, fully-stretched free-standing thin film is prepared. The successful transfer to a curved surface demonstrates the possibility for production of thin film-coated complex optical components. Ultrathin (35 nm) hybrid film transferred onto PET (50 μm thick) shows high transparency (>90% in visible range), conductivity (1.54 × 10(4) S/m), and flexibility (radius of curvature down to mm scale). The reported transfer method would provide a powerful route towards complex thin film-based structures/devices.

A General Strategy for Hybrid Thin Film Fabrication and Transfer onto Arbitrary Substrates

PubMed Central

Zhang, Yong; Magan, John J.; Blau, Werner J.

2014-01-01

The development of thin film-based structures/devices often requires thin films to be transferred onto arbitrary substrates/surfaces. Controllable and non-destructive transfer method, although highly desired, remains quite challenging. Here we report a general method for fabrication and transfer of hybrid (ultra)thin films. The proposed solution-based in-situ transfer method shows not only its robust ability for thin film transfer onto arbitrary substrates but also its highly controlled and non-destructive characteristic. With a hole structure as the support, fully-stretched free-standing thin film is prepared. The successful transfer to a curved surface demonstrates the possibility for production of thin film-coated complex optical components. Ultrathin (35 nm) hybrid film transferred onto PET (50 μm thick) shows high transparency (>90% in visible range), conductivity (1.54 × 104 S/m), and flexibility (radius of curvature down to mm scale). The reported transfer method would provide a powerful route towards complex thin film-based structures/devices. PMID:24769689

Fabrication of VO2 thin film by rapid thermal annealing in oxygen atmosphere and its metal—insulator phase transition properties

NASA Astrophysics Data System (ADS)

Liang, Ji-Ran; Wu, Mai-Jun; Hu, Ming; Liu, Jian; Zhu, Nai-Wei; Xia, Xiao-Xu; Chen, Hong-Da

2014-07-01

Vanadium dioxide thin films have been fabricated through sputtering vanadium thin films and rapid thermal annealing in oxygen. The microstructure and the metal—insulator transition properties of the vanadium dioxide thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and a spectrometer. It is found that the preferred orientation of the vanadium dioxide changes from (1¯11) to (011) with increasing thickness of the vanadium thin film after rapid thermal annealing. The vanadium dioxide thin films exhibit an obvious metal—insulator transition with increasing temperature, and the phase transition temperature decreases as the film thickness increases. The transition shows hysteretic behaviors, and the hysteresis width decreases as the film thickness increases due to the higher concentration carriers resulted from the uncompleted lattice. The fabrication of vanadium dioxide thin films with higher concentration carriers will facilitate the nature study of the metal—insulator transition.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

Metallic Thin-Film Bonding and Alloy Generation

NASA Technical Reports Server (NTRS)

Peotter, Brian S. (Inventor); Fryer, Jack Merrill (Inventor); Campbell, Geoff (Inventor); Droppers, Lloyd (Inventor)

2016-01-01

Diffusion bonding a stack of aluminum thin films is particularly challenging due to a stable aluminum oxide coating that rapidly forms on the aluminum thin films when they are exposed to atmosphere and the relatively low meting temperature of aluminum. By plating the individual aluminum thin films with a metal that does not rapidly form a stable oxide coating, the individual aluminum thin films may be readily diffusion bonded together using heat and pressure. The resulting diffusion bonded structure can be an alloy of choice through the use of a carefully selected base and plating metals. The aluminum thin films may also be etched with distinct patterns that form a microfluidic fluid flow path through the stack of aluminum thin films when diffusion bonded together.

Modified hyperbolic sine model for titanium dioxide-based memristive thin films

NASA Astrophysics Data System (ADS)

Abu Bakar, Raudah; Syahirah Kamarozaman, Nur; Fazlida Hanim Abdullah, Wan; Herman, Sukreen Hana

2018-03-01

Since the emergence of memristor as the newest fundamental circuit elements, studies on memristor modeling have been evolved. To date, the developed models were based on the linear model, linear ionic drift model using different window functions, tunnelling barrier model and hyperbolic-sine function based model. Although using hyperbolic-sine function model could predict the memristor electrical properties, the model was not well fitted to the experimental data. In order to improve the performance of the hyperbolic-sine function model, the state variable equation was modified. On the one hand, the addition of window function cannot provide an improved fitting. By multiplying the Yakopcic’s state variable model to Chang’s model on the other hand resulted in the closer agreement with the TiO2 thin film experimental data. The percentage error was approximately 2.15%.

Fully integrated carbon nanotube composite thin film strain sensors on flexible substrates for structural health monitoring

NASA Astrophysics Data System (ADS)

Burton, A. R.; Lynch, J. P.; Kurata, M.; Law, K. H.

2017-09-01

Multifunctional thin film materials have opened many opportunities for novel sensing strategies for structural health monitoring. While past work has established methods of optimizing multifunctional materials to exhibit sensing properties, comparatively less work has focused on their integration into fully functional sensing systems capable of being deployed in the field. This study focuses on the advancement of a scalable fabrication process for the integration of multifunctional thin films into a fully integrated sensing system. This is achieved through the development of an optimized fabrication process that can create a broad range of sensing systems using multifunctional materials. A layer-by-layer deposited multifunctional composite consisting of single walled carbon nanotubes (SWNT) in a polyvinyl alcohol and polysodium-4-styrene sulfonate matrix are incorporated with a lithography process to produce a fully integrated sensing system deposited on a flexible substrate. To illustrate the process, a strain sensing platform consisting of a patterned SWNT-composite thin film as a strain-sensitive element within an amplified Wheatstone bridge sensing circuit is presented. Strain sensing is selected because it presents many of the design and processing challenges that are core to patterning multifunctional thin film materials into sensing systems. Strain sensors fabricated on a flexible polyimide substrate are experimentally tested under cyclic loading using standard four-point bending coupons and a partial-scale steel frame assembly under lateral loading. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with linearity and sensitivity exceeding 0.99 and 5 {{V}}/{ε }, respectively. The thin film strain sensors are robust and are capable of high strain measurements beyond 3000 μ {ε }.

Morphological Evolution of Gyroid-Forming Block Copolymer Thin Films with Varying Solvent Evaporation Rate.

PubMed

Wu, Yi-Hsiu; Lo, Ting-Ya; She, Ming-Shiuan; Ho, Rong-Ming

2015-08-05

In this study, we aim to examine the morphological evolution of block copolymer (BCP) nanostructured thin films through solvent evaporation at different rates for solvent swollen polystyrene-block-poly(l-lactide) (PS-PLLA). Interesting phase transitions from disorder to perpendicular cylinder and then gyroid can be found while using a partially selective solvent for PS to swell PS-PLLA thin film followed by solvent evaporation. During the transitions, gyroid-forming BCP thin film with characteristic crystallographic planes of (111)G, (110)G, and (211)G parallel to air surface can be observed, and will gradually transform into coexisting (110)G and (211)G planes, and finally transforms to (211)G plane due to the preferential segregation of constituted block to the surface (i.e., the thermodynamic origin for self-assembly) that affects the relative amount of each component at the air surface. With the decrease on the evaporation rate, the disorder phase will transform to parallel cylinder and then directly to (211)G without transition to perpendicular cylinder phase. Most importantly, the morphological evolution of PS-PLLA thin films is strongly dependent upon the solvent removal rate only in the initial stage of the evaporation process due to the anisotropy of cylinder structure. Once the morphology is transformed back to the isotropic gyroid structure after long evaporation, the morphological evolution will only relate to the variation of the surface composition. Similar phase transitions at the substrate can also be obtained by controlling the ratio of PLLA-OH to PS-OH homopolymers to functionalize the substrate. As a result, the fabrication of well-defined nanostructured thin films with controlled orientation can be achieved by simple swelling and deswelling with controlled evaporation rate.

"One-sample concept" micro-combinatory for high throughput TEM of binary films.

PubMed

Sáfrán, György

2018-04-01

Phases of thin films may remarkably differ from that of bulk. Unlike to the comprehensive data files of Binary Phase Diagrams [1] available for bulk, complete phase maps for thin binary layers do not exist. This is due to both the diverse metastable, non-equilibrium or instable phases feasible in thin films and the required volume of characterization work with analytical techniques like TEM, SAED and EDS. The aim of the present work was to develop a method that remarkably facilitates the TEM study of the diverse binary phases of thin films, or the creation of phase maps. A micro-combinatorial method was worked out that enables both preparation and study of a gradient two-component film within a single TEM specimen. For a demonstration of the technique thin Mn x Al 1- x binary samples with evolving concentration from x = 0 to x = 1 have been prepared so that the transition from pure Mn to pure Al covers a 1.5 mm long track within the 3 mm diameter TEM grid. The proposed method enables the preparation and study of thin combinatorial samples including all feasible phases as a function of composition or other deposition parameters. Contrary to known "combinatorial chemistry", in which a series of different samples are deposited in one run, and investigated, one at a time, the present micro-combinatorial method produces a single specimen condensing a complete library of a binary system that can be studied, efficiently, within a single TEM session. That provides extremely high throughput for TEM characterization of composition-dependent phases, exploration of new materials, or the construction of phase diagrams of binary films. Copyright © 2018 Elsevier B.V. All rights reserved.

A new concept in polymeric thin-film composite nanofiltration membranes with antibacterial properties.

PubMed

Mollahosseini, Arash; Rahimpour, Ahmad

2013-01-01

A new, thin film, biofouling resistant, nanofiltration (NF) membrane was fabricated with two key characteristics, viz. a low rate of silver (Ag) release and long-lasting antibacterial properties. In the new approach, nanoparticles were embedded completely in a polymeric thin-film layer. A comparison was made between the new thin-film composite (TFC), NF membrane and thin-film nanocomposite (TFN), and antibacterial NF membranes. Both types of NF membrane were fabricated by interfacial polymerization on a polysulphone sublayer using m-phenylenediamine and trimesoyl chloride as an amine monomer and an acid chloride monomer, respectively. Energy dispersive X-ray (EDX) microanalysis demonstrated the presence of Ag nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the cross-sectional and surface morphological properties of the NF membranes. Permeability and salt rejection were tested using a dead-end filtration cell. Ag leaching from the membranes was measured using inductively coupled mass spectrometry (ICP-MS). Morphological studies showed that the TFC NF membranes had better thin-film formation (a more compact structure and a smoother surface) than TFN NF membranes. Performance experiments on TFC NF membranes revealed that permeability was good, without sacrificing salt rejection. The antibacterial properties of the fabricated membranes were tested using the disk diffusion method and viable plate counts. The antibiofouling properties of the membranes were examined by measuring the quantity of bacterial cells released from the biofilm formed (as a function of the amount of biofilm present). A more sensitive surface was observed compared to that of a typical antibacterial NF membrane. The Ag leaching rates were low, which will likely result in long-lasting antibacterial and biofouling resistant properties.

Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions

NASA Technical Reports Server (NTRS)

Martin, Lisa C.; Fralick, Gustave C.; Taylor, Keith F.

1999-01-01

Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

Effects of air annealing on CdS quantum dots thin film grown at room temperature by CBD technique intended for photosensor applications

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

Shaikh, Shaheed U.; Desale, Dipalee J.; Siddiqui, Farha Y.

2012-11-15

Graphical abstract: The effect of different intensities (40, 60 100 and 200 W) of light on CdS quantum dots thin film annealed at 350 °C indicating enhancement in (a) photo-current and (b) photosensitivity. Highlights: ► The preparation of CdS nanodot thin film at room temperature by M-CBD technique. ► Study of air annealing on prepared CdS nanodots thin film. ► The optimized annealing temperature for CdS nanodot thin film is 350 °C. ► Modified CdS thin films can be used in photosensor application. -- Abstract: CdS quantum dots thin-films have been deposited onto the glass substrate at room temperature usingmore » modified chemical bath deposition technique. The prepared thin films were further annealed in air atmosphere at 150, 250 and 350 °C for 1 h and subsequently characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, electrical resistivity and I–V system. The modifications observed in morphology and opto-electrical properties of the thin films are presented.« less