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Sample records for ferrite films grown

  1. Self-organized single crystal mixed magnetite/cobalt ferrite films grown by infrared pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    de la Figuera, Juan; Quesada, Adrián; Martín-García, Laura; Sanz, Mikel; Oujja, Mohamed; Rebollar, Esther; Castillejo, Marta; Prieto, Pilar; Muñoz-Martín, Ángel; Aballe, Lucía; Marco, José F.

    2015-12-01

    We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO3 by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.

  2. Nanocolumnar interfaces and enhanced magnetic coercivity in preferentially oriented cobalt ferrite thin films grown using oblique-angle pulsed laser deposition.

    PubMed

    Mukherjee, Devajyoti; Hordagoda, Mahesh; Hyde, Robert; Bingham, Nicholas; Srikanth, Hariharan; Witanachchi, Sarath; Mukherjee, Pritish

    2013-08-14

    Highly textured cobalt ferrite (CFO) thin films were grown on Si (100) substrates using oblique-angle pulsed laser deposition (α-PLD). X-ray diffraction and in-depth strain analysis showed that the obliquely deposited CFO films had both enhanced orientation in the (111) crystal direction as well as tunable compressive strains as a function of the film thicknesses, in contrast to the almost strain-free polycrystalline CFO films grown using normal-incidence PLD under the same conditions. Using in situ optical plume diagnostics the growth parameters in the α-PLD process were optimized to achieve smoother film surfaces with roughness values as low as 1-2 nm as compared to the typical values of 10-12 nm in the normal-incidence PLD grown films. Cross-sectional high resolution transmission electron microscope images revealed nanocolumnar growth of single-crystals of CFO along the (111) crystallographic plane at the film-substrate interface. Magnetic measurements showed larger coercive fields (∼10 times) with similar saturation magnetization in the α-PLD-grown CFO thin films as compared to those deposited using normal-incidence PLD. Such significantly enhanced magnetic coercivity observed in CFO thin films make them ideally suited for magnetic data storage applications. A growth mechanism based on the atomic shadowing effect and strain compression-relaxation mechanism was proposed for the obliquely grown CFO thin films. PMID:23829642

  3. Magnetic Properties of Polycrystalline Bismuth Ferrite Thin Films Grown by Atomic Layer Deposition.

    PubMed

    Jalkanen, Pasi; Tuboltsev, Vladimir; Marchand, Benoît; Savin, Alexander; Puttaswamy, Manjunath; Vehkamäki, Marko; Mizohata, Kenichiro; Kemell, Marianna; Hatanpää, Timo; Rogozin, Valentin; Räisänen, Jyrki; Ritala, Mikko; Leskelä, Markku

    2014-12-18

    The atomic layer deposition (ALD) method was applied to grow thin polycrystalline BiFeO3 (BFO) films on Pt/SiO2/Si substrates. The 50 nm thick films were found to exhibit high resistivity, good morphological integrity, and homogeneity achieved by the applied ALD technique. Magnetic characterization revealed saturated magnetization of 25 emu/cm(3) with temperature-dependent coercivity varying from 5 to 530 Oe within the temperature range from 300 to 2 K. Magnetism observed in the films was found to change gradually from ferromagnetic spin ordering to pinned magnetic domain interactions mixed with weak spin-glass-like behavior of magnetically frustrated antiferromagnetic/ferromagnetic (AFM-FM) spin ordering depending on the temperature and magnitude of the applied magnetic field. Antiferromagnetic order of spin cycloids was broken in polycrystalline films by crystal sizes smaller than the cycloid length (∼60 nm). Uncompensated spincycloids and magnetic domain walls were found to be the cause of the high magnetization of the BFO films. PMID:26273981

  4. Epitaxial single crystalline ferrite films for high frequency applications

    SciTech Connect

    Suzuki, Y.; Dover, R.B. van; Korenivski, V.; Werder, D.; Chen, C.H.; Felder, R.J.; Phillips, J.M.

    1996-11-01

    The successful growth of single crystal ferrites in thin film form is an important step towards their future incorporation into integrated circuits operating at microwave frequencies. The authors have successfully grown high quality single crystalline spinel ferrite thin films of (Mn,Zn)Fe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} on (100) and (110) SrTiO{sub 3} and MgAl{sub 2}O{sub 4} at low temperature. These ferrite films are buffered with spinel structure layers that are paramagnetic at room temperature. In contrast to ferrite films grown directly on the substrates, ferrite films grown on buffered substrates exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer. X-ray, RBS, AFM and TEM analysis provide a consistent picture of the structural properties of these ferrite films. The authors then use this technique to grow exchange-coupled bilayers of single crystalline CoFe{sub 2}O{sub 4} and (Mn,Zn)Fe{sub 2}O{sub 4}. In these bilayers, they observe strong exchange coupling across the interface that is similar in strength to the exchange coupling in the individual layers.

  5. Control of magnetization reversal in oriented strontium ferrite thin films

    SciTech Connect

    Roy, Debangsu Anil Kumar, P. S.

    2014-02-21

    Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al{sub 2}O{sub 3}(0001) substrate using Pulsed Laser Deposition technique. The angle dependent magnetic hysteresis, remanent coercivity, and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth.

  6. Room-temperature growth of Ni-Zn-Cu ferrite/PTFE composite thick films on PET via aerosol deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hyung-Jun; Kwon, Oh-Yun; Jang, Chan-Ick; Kim, Tae Kyoung; Oh, Jun Rok; Yoon, Young Joon; Kim, Jong-Hee; Nam, Song-Min; Koh, Jung-Hyuk

    2013-11-01

    Ni-Zn-Cu ferrite and Ni-Zn-Cu ferrite/poly-tetra-fluoro-ethylene (PTFE) composite-thick-films were grown at room temperature on polyethylene terephthalate (PET) sheets via aerosol deposition (AD) as a magnetic shielding sheet for near-field communication. An 80 µm-thick Ni-Zn-Cu ferrite/PTFE composite-thick-film was grown on the PET sheet when 2.0 wt. % PTFE starting powder was used. The real relative permeability µ r ' and the imaginary permeability µ r ″ of the Ni-Zn-Cu ferrite thick film were 10.1 and 2.1 at 13.56 MHz, respectively. In the case of the composite thick film, µ r ' and µ r ″ decreased to 3.9 and 1.3, respectively, at 13.56 MHz; with the addition of the PTFE.

  7. LPE growth of Mn, Ni- and Al-substituted copper ferrite films

    NASA Astrophysics Data System (ADS)

    van der Straten, P. J. M.; Metselaar, R.

    1980-06-01

    Single-crystalline Mn-, Ni-, and Al-substituted copper ferrite films are grown by the LPE method from a PbO-B2O3 flux on (111)-MgO substrates. Solid solutions between copper ferrite and Mn3O4, NiFe2O4, and CuAl2O4 are obtained. The segregation coefficients for Ni and Al are shown to be linearly dependent on the growth temperature. From domain-structure observations and from torque measurements it is concluded that a positive uniaxial anisotropy is present in the copper ferrite films. After stress relief at the deposition temperature a stress develops during cooling to room temperature due to a difference in thermal expansion coefficients of film and substrate. This stress is responsible for the observed anisotropy.

  8. Energy of domain walls in ferrite films

    NASA Astrophysics Data System (ADS)

    Gomez, M. E.; Prieto, P.; Mendoza, A.; Guzman, O.

    2007-03-01

    MnZn Ferrite films were deposited by RF sputtering on (001) single crystal MgO substrates. AFM images show an increment in grain size with the film thickness. Grains with diameter between φ ˜ 70 and 700 nm have been observed. The coercive field Hc as a function of the grain size reaches a maximum value of about 80 Oe for φc˜ 300 nm. The existence of a multidomain structure associated with a critical grain size was identified by Magneto-optical Kerr effect technique (MOKE). The transition of the one-domain regime to the two-domain regime was observed at a critical grain size of Dc˜ 530 nm. This value agree with values predicted previously. The Jiles-Atherton model (JAM) was used to discuss the experimental hysteresis loops. The k pinning parameter obtained from JAM shows a maximum value of k/μo = 67 Am^2 for grains with Lc˜ 529 nm. The total energy per unit area E was correlated with k and D. We found a simple phenomenological relationship given by E α kD; where D is the magnetic domain width.

  9. Nanocrystalline zinc ferrite films studied by magneto-optical spectroscopy

    SciTech Connect

    Lišková-Jakubisová, E. Višňovský, Š.; Široký, P.; Hrabovský, D.; Pištora, J.; Sahoo, Subasa C.; Prasad, Shiva; Venkataramani, N.; Bohra, Murtaza; Krishnan, R.

    2015-05-07

    Ferrimagnetic Zn-ferrite (ZnFe{sub 2}O{sub 4}) films can be grown with the ferromagnetic resonance linewidth of 40 Oe at 9.5 GHz without going through a high temperature processing. This presents interest for applications. The work deals with laser ablated ZnFe{sub 2}O{sub 4} films deposited at O{sub 2} pressure of 0.16 mbar onto fused quartz substrates. The films about 120 nm thick are nanocrystalline and their spontaneous magnetization, 4πM{sub s}, depends on the nanograin size, which is controlled by the substrate temperature (T{sub s}). At T{sub s} ≈ 350 °C, where the grain distribution peaks around ∼20–30 nm, the room temperature 4πM{sub s} reaches a maximum of ∼2.3 kG. The films were studied by magnetooptical polar Kerr effect (MOKE) spectroscopy at photon energies between 1 and 5 eV. The complementary characteristics were provided by spectral ellipsometry (SE). Both the SE and MOKE spectra confirmed ferrimagnetic ordering. The structural details correspond to those observed in MgFe{sub 2}O{sub 4} and Li{sub 0.5}Fe{sub 2.5}O{sub 4} spinels. SE experiments confirm the insulator behavior. The films display MOKE amplitudes somewhat reduced with respect to those in Li{sub 0.5}Fe{sub 2.5}O{sub 4} and MgFe{sub 2}O{sub 4} due to a lower degree of spinel inversion and nanocrystalline structure. The results indicate that the films are free of oxygen vacancies and Fe{sup 3+}-Fe{sup 2+} exchange.

  10. Structural and magnetic studies of Cr doped nickel ferrite thin films

    NASA Astrophysics Data System (ADS)

    Panwar, Kalpana; Heda, N. L.; Tiwari, Shailja; Bapna, Komal; Choudhary, R. J.; Phase, D. M.; Ahuja, B. L.

    2016-05-01

    We have studied the structural and magnetic properties of Cr doped nickel ferrite thin films deposited on Si (100) and Si (111) using pulsed laser deposition technique. The films were deposited under vacuum and substrate temperature was kept at 700˚C. X-ray diffraction analysis revealed that films on both substrates have single phase cubic spinel structure. However, the film grown on Si (111) shows better crystalline behavior. Fourier transform infrared spectroscopy suggests that films on both substrates have mixed spinel structure. These films show magnetic hysteresis behavior and magnetization value of film on Si (100) is larger than that on Si (111). It turns out that structural and magnetic properties of these two films are correlated.

  11. Magnetooptical and crystalline properties of sputtered garnet ferrite film on spinel ferrite buffer layer

    NASA Astrophysics Data System (ADS)

    Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Kagami, Osamu; Tanabe, Takaya

    2016-09-01

    The purpose of this study is to provide garnet films for volumetric magnetic holography. Volumetric magnetic holography usually employs an easily obtainable short-wavelength laser (visible light, not infrared light) with a large diffraction intensity. Bi-substituted garnet ferrite with a large Faraday rotation is promising for volumetric magnetic holography applications in the visible light region. However, a garnet film without a deteriorated layer must be obtained because a deteriorated layer (minute polycrystalline grains containing an amorphous phase) is formed during the initial deposition on a glass substrate. In particular, the required magnetooptical properties have not been obtained in a thin garnet film (100 nm or less) after annealing (1 h, 700 °C, oxygen atmosphere). Therefore, there is a need for excellent garnet films with the required magnetooptical (MO) properties even if the films are thin. By using a spinel ferrite buffer layer for garnet film deposition, we could obtain a thin garnet film with excellent MO properties. We determined the effect of the initial buffer layer on the crystallinity of the deposited garnet films by observing the film cross section. In addition, we undertook a qualitative estimation of the influence of the crystallinity and optical properties of the garnet film on a glass substrate with a spinel ferrite buffer layer.

  12. Growth and Properties of Magnetic Spinel Ferrite Thin Films and Heterostructures

    NASA Astrophysics Data System (ADS)

    Gupta, Arunava

    2013-03-01

    There is considerable interest in the growth of single crystal spinel ferrites films because of their numerous technological applications in areas such as microwave integrated devices, magnetoelectric coupling heterostructures, and potentially as an active barrier material in an emerging class of spintronic devices called spin filters. Unlike perovskites, the study of spinel ferrite films is quite limited in part due to the complex crystal structure with a large unit cell consisting of many interstitial sites and that the transition metal cations can adopt various oxidation states. We have grown high-quality, atomically smooth epitaxial ferrite (NiFe2O4, CoFe2O4 and LiFe5O8) films using chemical vapor deposition and pulsed laser deposition techniques and carried out detailed studies of their structural, magnetic and optical properties. Of particular interest are systematic studies on the formation of antiphase boundaries in epitaxial NiFe2O4 films grown on different substrates and the accurate determination of the band gap of this material using optical spectroscopy and first principles calculations. Additionally, we have grown ferrite films on piezoelectric substrates and observed large shifts in the ferromagnetic resonance profile due to magnetoelectric coupling resulting from electrostatic field-induced changes in the magnetic anisotropy field. Work done in collaboration with N. Z. Bao, W. H. Butler, R. Datta, B. S. Holinsworth, M. Iliev, S. Kanuri, S. V. Karthik, G. Kim, T. M. Klein, N. Li, M. Liu, P. R. LeClair, J. X. Ma, D. Mazumdar, T. Mewes, D. V. B. Murthy, J. L. Musfeldt, K. R. O'Neal, N. Pachauri, V. M. Petrov, H. Sato, S. Schäfer, L. Shen, H. Sims, G. Srinivasan, N. X. Sun, Q. -C. Sun, and Z. Zhou. The work was supported by ONR (Grant Number N00014-12-1-0102)

  13. Planar Millimeter Wave Notch Filters Based on Magnetostatic Wave Resonance in Barium Hexagonal Ferrite Thin Films

    NASA Astrophysics Data System (ADS)

    Lu, Lei; Song, Young-Yeal; Bevivino, Joshua; Wu, Mingzhong

    2010-10-01

    There is a critical need for planar millimeter (mm) wave devices. To meet this need, one important strategy is in the use of high-anisotropy hexagonal ferrite films. The high internal anisotropy field for the hexagonal ferrites can be used to realize low-loss devices in the 30-100 GHz regime without the need for high external magnetic fields. Previous work has demonstrated the use of M-type barium hexagonal ferrite (BaM) films and ferromagnetic resonance therein to make mm-wave notch filters. This presentation reports on a new mm-wave notch filter that uses magnetostatic wave (MSW) resonance in BaM films. The device consists of a BaM film strip positioned on the top of a coplanar waveguide (CPW), with the strip's length along the CPW signal line. The BaM strip was grown by pulsed laser deposition and had uniaxial anisotropy along the strip's length. The device showed a band-stop filtering response centered at 53 GHz in absence of external fields. One can increase this frequency with nonzero external fields. A reduction in the strip's width resulted in an enhancement in peak absorption. This filtering response resulted from MSW resonance across the BaM strip's width. The MSW modes were excited by CPW-produced non-uniform alternating magnetic fields.

  14. Epitaxy barium ferrite thin films on LiTaO3 substrate

    NASA Astrophysics Data System (ADS)

    Fang, H. C.; Ong, C. K.; Xu, S. Y.; Tan, K. L.; Lim, S. L.; Li, Y.; Liu, J. M.

    1999-08-01

    Barium hexaferrite (BaM) thin films were deposited on (0001) LiTaO3 substrates by pulsed laser deposition. Effects of the substrate temperature and oxygen gas pressure on the formation and quality of these films were studied. Films deposited at a substrate temperature of 800 °C and an oxygen pressure around 0.23 mbar showed the best c axis normal to the film plane with locked in-plane orientation. The saturation magnetization Ms and anisotropy field Ha measured by vibrating sample magnetometer were almost the same as those reported on bulk barium ferrite. Decreasing oxygen pressure hinders the formation of the Ba layer in BaM magnetoplumbite structure and gives rise to the spinel phase, which greatly decreases coercivity Hc of the films and finally destroys the whole BaM structure. Effects of the lattice mismatch and substrate-induced strains on the film structure were also studied. It was found that barium ferrite thin films grown on LiTaO3 substrates tend to choose a matching mode with compressional strains rather than shear strains.

  15. Growth, structure, morphology, and magnetic properties of Ni ferrite films

    PubMed Central

    2013-01-01

    The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

  16. On-wafer millimeter wave notch filter based on barium hexagonal ferrite thin films on platinum

    NASA Astrophysics Data System (ADS)

    Harward, Ian Roylance

    In this work, the growth of BaM and Al doped Ba M thin films on Pt templates, layered on a Si wafer, is demonstrated using a newly developed metallo-organic decomposition (MOD) process. It is shown that the BaM films are polycrystalline, with preferred perpendicular c-axis grain orientation. The magnetic properties such as anisotropy field, saturation magnetization, and remnant magnetization are studied as a function of temperature and film composition, and are shown to be correlated to the film microstructure. It is shown that these films exhibit high remnant magnetization, a property not measured in BaM single crystals, meaning a biasing magnet may not be necessary for millimeter wave device applications. Ferromagnetic resonance (FMR) studies were performed on the ferrite films using the tool developed at UCCS for the study of high frequency magnetic materials, the broadband FMR (BFMR) system. The instrument is described in great detail, and the FMR studies on BaM show that the MOD-grown films exhibit narrow FMR linewidths, on the order of 150 Oe, and are therefore of sufficient quality for use in mm wave devices. Finally, notch filters using the Pt/BaM are demonstrated. The filters are based on a microstrip design, where the Pt serves as the ground plane and the BaM is part of the dielectric. The Ba M absorbs signals at the ferromagnetic resonance frequency, which takes place in the mm wave range. The filters described were based on pure BaM, but Al doped BaM could easily be used to increase the operating frequency of the device. The operating frequency of these devices is also tunable using an externally applied magnetic field.

  17. Effect of deposition pressure on the structural and magnetic properties of cobalt ferrite thin films

    SciTech Connect

    Nongjai, R.; Khan, S.; Ahmad, H.; Khan, I.; Asokan, K.

    2013-06-03

    We present the influence of deposition pressure on the structural and magnetic properties of cobalt ferrite thin films. Thin films of Co ferrite were deposited by rf sputtering on Si (100) substrate and characterized by X - Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Vibrating Sample Magnetometer (VSM). The XRD patterns showed the formation of crystalline single phase of the films. The particle size and surface roughness of the films were strongly influence by gas pressure. Hysteresis loops measured at room temperature showed the enhancement of magnetic properties with the increase of gas pressure which is attributed to the decrease of particle size.

  18. Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2013-12-01

    Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan δ) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

  19. Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

    SciTech Connect

    Buršík, J.; Kužel, R.; Knížek, K.; Drbohlav, I.

    2013-07-15

    Thin films of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO{sub 3}(1 1 1) (ST) single crystal substrates using epitaxial SrFe{sub 12}O{sub 19} (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature ramp were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and Φ scans reveal perfect parallel in-plane alignment of SrTiO{sub 3} substrate and both hexaferrite phases. - Graphical abstract: XRD pole figure and AFM patterns of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} thin film epitaxially grown on SrTiO{sub 3}(1 1 1) single crystal using seeding layer templating. - Highlights: • Single phase Y-type hexagonal ferrite thin films were prepared by CSD method. • Seed M layer breaks into isolated single crystal islands and serves as a template. • Large seed grains grow by consuming the grains within the bulk of recoated film. • We explained the observed orientation relation of epitaxial domains. • Epitaxial growth on SrTiO{sub 3}(1 1 1) with relation (0 0 1){sub M,Y}//(1 1 1){sub ST}+[1 0 0]{sub M,Y}//[2 −1 −1]{sub ST}.

  20. Single layer porous gold films grown at different temperatures

    NASA Astrophysics Data System (ADS)

    Zhang, Renyun; Hummelgård, Magnus; Olin, Håkan

    2010-11-01

    Large area porous gold films can be used in several areas including electrochemical electrodes, as an essential component in sensors, or as a conducting material in electronics. Here, we report on evaporation induced crystal growth of large area porous gold films at 20, 40 and 60 °C. The gold films were grown on liquid surface at 20 °C, while the films were grown on the wall of beakers when temperature increased to 40 and 60 °C. The porous gold films consisted of a dense network of gold nanowires as characterized by TEM and SEM. TEM diffraction results indicated that higher temperature formed larger crystallites of gold wires. An in situ TEM imaging of the coalescence of gold nanoparticles mimicked the process of the growth of these porous films, and a plotting of the coalescence time and the neck radius showed a diffusion process. The densities of these gold films were also characterized by transmittance, and the results showed film grown at 20 °C had the highest density, while the film grown at 60 °C had the lowest consistent with SEM and TEM characterization. Electrical measurements of these gold films showed that the most conductive films were the ones grown at 40 °C. The conductivities of the gold films were related to the amount of contamination, density and the diameter of the gold nanowires in the films. In addition, a gold film/gold nanoparticle hybrid was made, which showed a 10% decrease in transmittance during hybridization, pointing to applications as chemical and biological sensors.

  1. Relations between magneto-optical properties and reactivity in cobalt-manganese ferrite thin films and powders

    NASA Astrophysics Data System (ADS)

    Bouet, Laurence; Tailhades, Philippe; Rousset, Abel

    1996-02-01

    Co-Mn spinel ferrites were prepared as submicron powders and thin films. Because of their finely divided state, these spinels could be oxidized at low temperatures to give novel cation-deficient ferrites. For these two material forms, the magneto-optical properties were found to be strongly dependent on the ferrite oxidation state. The highest coercivities and Faraday rotations were obtained when the ferrites were partially oxidized. These phenomena are attributed to the mechanical stress effect developed during the oxidation of the manganese ions. The properties of these ferrites could be of interest for magneto-optical recording applications. The first static recording tests were performed at 780 nm wavelength.

  2. Columnar grown copper films on polyimides strained beyond 100.

    PubMed

    Sun, Jeong-Yun; Lee, Hae-Ryung; Oh, Kyu Hwan

    2015-01-01

    Many flexible electronic devices contain metal films on polymer substrates to satisfy requirements for both electrical conductivity and mechanical durability. Despite numerous trials to date, the stretchability of metal interconnects remains an issue. In this paper, we have demonstrated a stretchable metal interconnect through control of the texture of a copper film with columnar grown grains on a polyimide (PI) substrate. The columnar grown copper films (CGC films) were deposited by regulating radio frequency (RF) sputtering powers. CGC films were able to sustain their electrical conductivity at strains above 100%. Instead of ultimate electrical discontinuity by channel crack propagation, CGC films maintained their conductivity by forming ligament structures, or a 'conductive net,' through trapped micro-cracks. XRD, AFM and in situ SEM analysis were used to investigate these stretchable conductors. PMID:26337668

  3. Columnar grown copper films on polyimides strained beyond 100%

    PubMed Central

    Sun, Jeong-Yun; Lee, Hae-Ryung; Hwan Oh, Kyu

    2015-01-01

    Many flexible electronic devices contain metal films on polymer substrates to satisfy requirements for both electrical conductivity and mechanical durability. Despite numerous trials to date, the stretchability of metal interconnects remains an issue. In this paper, we have demonstrated a stretchable metal interconnect through control of the texture of a copper film with columnar grown grains on a polyimide (PI) substrate. The columnar grown copper films (CGC films) were deposited by regulating radio frequency (RF) sputtering powers. CGC films were able to sustain their electrical conductivity at strains above 100%. Instead of ultimate electrical discontinuity by channel crack propagation, CGC films maintained their conductivity by forming ligament structures, or a ‘conductive net,’ through trapped micro-cracks. XRD, AFM and in situ SEM analysis were used to investigate these stretchable conductors. PMID:26337668

  4. Columnar grown copper films on polyimides strained beyond 100%

    NASA Astrophysics Data System (ADS)

    Sun, Jeong-Yun; Lee, Hae-Ryung; Hwan Oh, Kyu

    2015-09-01

    Many flexible electronic devices contain metal films on polymer substrates to satisfy requirements for both electrical conductivity and mechanical durability. Despite numerous trials to date, the stretchability of metal interconnects remains an issue. In this paper, we have demonstrated a stretchable metal interconnect through control of the texture of a copper film with columnar grown grains on a polyimide (PI) substrate. The columnar grown copper films (CGC films) were deposited by regulating radio frequency (RF) sputtering powers. CGC films were able to sustain their electrical conductivity at strains above 100%. Instead of ultimate electrical discontinuity by channel crack propagation, CGC films maintained their conductivity by forming ligament structures, or a ‘conductive net,’ through trapped micro-cracks. XRD, AFM and in situ SEM analysis were used to investigate these stretchable conductors.

  5. Synthesis and characterizations of microwave sintered ferrite powders and their composite films for practical applications

    NASA Astrophysics Data System (ADS)

    Shannigrahi, S. R.; Pramoda, K. P.; Nugroho, F. A. A.

    2012-01-01

    Phase pure single phase ferrite powders of (NixR1-x)0.5Zn0.5Fe2O4 (R=Mn, Co, Cu; x=0, 0.5) were manufactured using microwave sintering at 930 °C for 10 min in air atmosphere. The powders were characterized for their structure, microstructure, thermal, and magnetic properties. Selected powders were used as fillers to prepare their composite films using polymethyl methacrylate polymers as matrix. The composite films were prepared using the melt blending approach and were tested for their microstructure, thermal, and magnetic hysteresis loop as well as 3D magnetic field space mappings using an electromagnetic compatibility scanner. Among the studied ferrites, cobalt doped ferrites and their composites showed the best electromagnetic interference (EMI) shielding effectiveness value and have potential for practical EMI shielding applications.

  6. Chlorine gas sensing performance of palladium doped nickel ferrite thin films

    NASA Astrophysics Data System (ADS)

    Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

    2016-05-01

    NiFe2O4 and Pd:NiFe2O4 (Pd=1 w/o, 3 w/o and 5 w/o) thin films, p-type semiconducting oxides with an inverse spinel structure have been used as a gas sensor to detect chlorine. These films were prepared by spray pyrolysis technique and XRD was used to confirm the structure. The surface morphology was studied using SEM. Magnetization measurements were carried out at room temperature using SQUID VSM, which shows ferrimagnetic behavior of the samples. The reduction in optimum operating temperature and enhancement in response was observed on Pd-incorporation in nickel ferrite thin films. Faster response and recovery characteristic is observed Pd-incorporated nickel ferrite thin films. The long-term stability is evaluated over a period of six months. This feature may be regarded as a significant facet towards their practical application as gas sensors.

  7. Poisson Ratio of Epitaxial Germanium Films Grown on Silicon

    NASA Astrophysics Data System (ADS)

    Bharathan, Jayesh; Narayan, Jagdish; Rozgonyi, George; Bulman, Gary E.

    2013-01-01

    An accurate knowledge of elastic constants of thin films is important in understanding the effect of strain on material properties. We have used residual thermal strain to measure the Poisson ratio of Ge films grown on Si ⟨001⟩ substrates, using the sin2 ψ method and high-resolution x-ray diffraction. The Poisson ratio of the Ge films was measured to be 0.25, compared with the bulk value of 0.27. Our study indicates that use of Poisson ratio instead of bulk compliance values yields a more accurate description of the state of in-plane strain present in the film.

  8. Exchange coupling driven omnidirectional rotatable anisotropy in ferrite doped CoFe thin film

    PubMed Central

    Chai, Guozhi; Phuoc, Nguyen N.; Ong, C. K.

    2012-01-01

    Isotropic magnetic materials with high resonant frequencies are useful for applications in microwave devices. Undoped CoFe thin films, as common soft magnetic materials with high saturation magnetization, show isotropic characteristics but no high frequency response. Here, we use ferrite doped CoFe thin film to realize a resonant frequency higher than 4.5 GHz at all orientations. The exchange coupling between ferrimagnet and ferromagnet is assumed to play a key role on the omnidirectional rotatable anisotropy. PMID:23145323

  9. Faraday rotation of cobalt ferrite nanoparticle polymer composite films at cryogenic temperatures.

    PubMed

    Demir, Veysi; Gangopadhyay, Palash; Norwood, Robert A; Peyghambarian, Nasser

    2014-04-01

    This paper investigates the behavior of the Verdet constant for cobalt ferrite (CoFe₂O₄) nanoparticles polymer composite films at low temperatures using a 532 nm laser source. An experimental setup for Faraday rotation (FR) at low temperatures is introduced and FRs were measured at various temperatures. Verdet constants were deduced from the paramagnetic model for terbium gallium garnet glass where ~4× improvement was observed at 40° K for CoFe₂O₄ composite film. PMID:24787165

  10. Magneto-optical Kerr effect in NiZn ferrite films of variable thickness

    NASA Astrophysics Data System (ADS)

    Calle, C.; Calle, V. H.; Cuéllar, F.; Cortés, A.; Arias, D.; Lopera, W.; Prieto, P.; Guzmán, O.; Mendoza, G. A.

    2006-10-01

    NiZn ferrites films deposited by RF sputtering technique on (1 0 0)-Si substrates have been studied by the magneto-optical Kerr effect. The coercivity behavior as a function of the thickness indicates a spin reversal mainly governed by the single domain regime. The Jiles-Atherton Model was used to fit the experimental hysteresis loop. The k pinning parameter of the model increases by increasing film thicknesses

  11. Morphology in electrochemically grown conducting polymer films

    DOEpatents

    Rubinstein, Israel; Gottesfeld, Shimshon; Sabatani, Eyal

    1992-01-01

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventioonally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol.

  12. Morphology in electrochemically grown conducting polymer films

    DOEpatents

    Rubinstein, I.; Gottesfeld, S.; Sabatani, E.

    1992-04-28

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventionally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol. 2 figs.

  13. MBE grown high quality GaN films and devices

    NASA Astrophysics Data System (ADS)

    Kim, W.; Aktas, O.; Salvador, A.; Botchkarev, A.; Sverdlov, B.; Mohammad, S. N.; Morkoç, H.

    1997-02-01

    GaN films with much improved structural, transport, and optical properties have been prepared by molecular beam epitaxy using NH 3 as a nitrogen source. Films with a wide range of resistivity, including highly resistive ones, were grown with a chosen growth rate of 1.2 μm/h. The electron mobility in modulation doped structures is about 450 and 850 cm 2/Vs at 300 and 77 K, respectively, with an areal carrier concentration of about 10 13 cm -2. Low temperature luminescence shows A- and B-free-excitons as well as the excited state of the A- and B-excitons, the first known observation, attesting to the quality of the samples. These transition energies are consistent with the best MOCVD samples and represent a sizable reduction of the pandemic zincblende phase in MBE grown films. The high quality of films was demonstrated by the realization of high performance MODFETs and Schottky diodes.

  14. Silicon oxide films grown in microwave discharge

    NASA Technical Reports Server (NTRS)

    Kraitchman, J.

    1968-01-01

    Silicon oxide films thicker than 1000 angstrom are produced in the dense plasma of a microwave discharge. The oxide growth is characterized by a rate limiting diffusion process modified by sputtering effects produced by the discharge. Silicon is rapidly oxidized at temperatures estimated to be 500 degrees C or lower.

  15. Photoluminescence Spectra of thin Zno films grown by ALD technology

    NASA Astrophysics Data System (ADS)

    Akopyan, I. Kh.; Davydov, V. Yu.; Labzovskaya, M. E.; Lisachenko, A. A.; Mogunov, Ya. A.; Nazarov, D. V.; Novikov, B. V.; Romanychev, A. I.; Serov, A. Yu.; Smirnov, A. N.; Titov, V. V.; Filosofov, N. G.

    2015-09-01

    The photoluminescence of ZnO films grown by atomic layer deposition (ALD) on silicon substrates has been investigated. A new broad photoluminescence band has been revealed in the exciton region of the spectrum. The properties of the band in the spectra of the films with different crystallographic orientations of substrates have been studied in a wide temperature range at different excitation levels. A model describing the origin of the new band has been proposed.

  16. Thickness Dependence Magnetization in Laser Ablated Ni-Cu-Zn Ferrite Nanostructured Thin Films.

    PubMed

    Raghavender, A T; Hong, Nguyen Hoa; Lee, Kyu Joon; Jung, Myung-Hwa

    2016-01-01

    Ni₀.₅Cu₀.₃Zn₀.₂Fe₂O₄ thin films with thickness ranging from 25 nm to 500 nm were grown on Si substrate using pulsed laser deposition technique and their structural and magnetic properties were investigated. From the atomic force microscopy (AFM) analysis, it is observed that the film roughness (Ra) depends strongly on the thickness of the fabricated film. The magnetizations of the thin films were found to decrease when the film thickness increases. The thinner films showed a larger magnetization than the thick films. All the films showed a blocking temperature indicating their superparamagnetic behavior. PMID:27398528

  17. InSb thin films grown by electrodeposition

    SciTech Connect

    Singh, Joginder Rajaram, P.

    2014-04-24

    We have grown InSb thin films on Cu substrates using the electrodeposition technique. The electrochemical bath from which the InSb thin films were grown was made up of a mixture of aqueous solutions of 0.05 M InCl{sub 3} and 0.03M SbCl{sub 3}, 0 .20M citric acid and 0.30M sodium citrate. Citric acid and sodium citrate were used as complexing agents to bring the reduction potential of In and Sb closer to maintain binary growth. The electrodeposited films were characterized by structural, morphological and optical studies. X-ray diffraction studies show that the films are polycrystalline InSb having the zinc blende structure. Scanning electron microscopy (SEM) studies reveal that the surface of the films is uniformly covered with submicron sized spherical particles. FTIR spectra of InSb thin films show a sharp absorption peak at wave number 1022 cm{sup −1} corresponding to the band gap. Hot probe analysis shows that the InSb thin films have p type conductivity.

  18. InSb thin films grown by electrodeposition

    NASA Astrophysics Data System (ADS)

    Singh, Joginder; Rajaram, P.

    2014-04-01

    We have grown InSb thin films on Cu substrates using the electrodeposition technique. The electrochemical bath from which the InSb thin films were grown was made up of a mixture of aqueous solutions of 0.05 M InCl3 and 0.03M SbCl3, 0 .20M citric acid and 0.30M sodium citrate. Citric acid and sodium citrate were used as complexing agents to bring the reduction potential of In and Sb closer to maintain binary growth. The electrodeposited films were characterized by structural, morphological and optical studies. X-ray diffraction studies show that the films are polycrystalline InSb having the zinc blende structure. Scanning electron microscopy (SEM) studies reveal that the surface of the films is uniformly covered with submicron sized spherical particles. FTIR spectra of InSb thin films show a sharp absorption peak at wave number 1022 cm-1 corresponding to the band gap. Hot probe analysis shows that the InSb thin films have p type conductivity.

  19. Effect of quenching on the magnetic properties of Mg-ferrite thin films

    NASA Astrophysics Data System (ADS)

    Roy Dakua, Himadri; Venkataramani, N.; Prasad, Shiva

    2016-05-01

    We have investigated the microstructural and magnetic properties of the post annealed slow cooled and quenched Mg-ferrite thin films. The microstructural properties of these films were studied through XRD, TEM and SEM. The magnetic properties were studied using VSM at 300K and 10K. The quenched film showed ˜1.66 times higher magnetization at room temperature (RT) compared to the bulk and the slow cooled film (4πMS of bulk˜1880 Gauss at RT) though the crystal phase, grain size and thickness of both the films were similar. The change in the cation distribution is the plausible origin of large magnetization observed in the quenched (rapid cooled) film.

  20. Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying

    SciTech Connect

    Dom, Rekha; Sivakumar, G.; Hebalkar, Neha Y.; Joshi, Shrikant V.; Borse, Pramod H.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Highly economic solution precursor route capable of producing films/coating even for mass scale production. Black-Right-Pointing-Pointer Pure spinel phase ZnFe{sub 2}O{sub 4} porous, immobilized films deposited in single step. Black-Right-Pointing-Pointer Parameter optimization yields access to nanostructuring in SPPS method. Black-Right-Pointing-Pointer The ecofriendly immobilized ferrite films were active under solar radiation. Black-Right-Pointing-Pointer Such magnetic system display advantage w.r.t. recyclability after photocatalyst extraction. -- Abstract: Deposition of pure spinel phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor conditions (7 < pH {<=} 10) were found to favor oxide film formation. The nanostructured films produced under optimized conditions, with 500 mM solution at pH {approx} 8.0, yielded pure cubic phase ZnFe{sub 2}O{sub 4} film. Very high/low precursor concentrations yielded mixed phase, less adherent, and highly inhomogeneous thin films. Desired spinel phase was achieved in as-deposited condition under appropriately controlled spray conditions and exhibited a band gap of {approx}1.9 eV. The highly porous nature of the films favored its photocatalytic performance as indicated by methylene blue de-coloration under solar radiation. These immobilized films display good potential for visible light photocatalytic applications.

  1. Effect of hydrothermal heat treatment on magnetic properties of copper zinc ferrite rf sputtered films

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Gadipelly, Thirupathi; Singh, R.

    2016-05-01

    The hydrothermal treatment to the nano-structured films can overcome the destruction of the films. The Cu-Zn Ferrite films were fabricated by RF-sputtering on quartz substrates. Subsequently, the as deposited films were heat treated using hydrothermal process. The X-ray diffraction pattern of the as-deposited and hydrothermal treated films indicate nano-crystalline cubic spinel structure. The amorphous nature of the films is removed after hydrothermal treatment with decreased crystallite size. The field emission scanning electron micrographs showed merged columnar growth for as deposited films, which changes to well define columns after hydrothermal heating. The homogeneous cluster distribution is observed in surface view of the hydrothermal treated films. Hydrothermal treated films show merging of in-plane and out of plane magnetization plots (M(H)) whereas the M(H) plots of as deposited films show angular dependence. The strong angular dependence is observed in the FMR spectra due to the presence of a uniaxial anisotropy in the films. The ferromagnetic interactions decrease in hydrothermal heated films due to the reduced shape anisotropy and crystallite size.

  2. Effect of annealing atmosphere on phase formation and electrical characteristics of bismuth ferrite thin films

    SciTech Connect

    Simoes, A.Z.; Riccardi, C.S.; Dos Santos, M.L.; Garcia, F. Gonzalez; Longo, E.; Varela, J.A.

    2009-08-05

    Bismuth ferrite thin films were deposited on Pt/Ti/SiO{sub 2}/Si substrates by a soft chemical method and spin-coating technique. The effect of annealing atmosphere (air, N{sub 2} and O{sub 2}) on the structure and electrical properties of the films are reported. X-ray diffraction analysis reveals that the film annealed in air atmosphere is a single-phase perovskite structure. The films annealed in air showed better crystallinity and the presence of a single BFO phase leading to lower leakage current density and superior ferroelectric hysteresis loops at room temperature. In this way, we reveal that BFO film crystallized in air atmosphere by the soft chemical method can be useful for practical applications, including nonvolatile digital memories, spintronics and data-storage media.

  3. Equilibrium State and Magnetic Permeability Tensor of the Epitaxial Ferrite Films

    NASA Astrophysics Data System (ADS)

    Bobkov, V. B.; Zavislyak, I. V.

    1997-12-01

    The analysis of the equilibrium state of an arbitrarily oriented epitaxial ferrite film with basic cubic symmetry has been carried out. The equilibrium orientation of the magnetization has been shown to coincide with the direction of the applied magnetic field for (n, n, m), (m, n, 0) and (112) films that are magnetized parallel to the surface along the axes 110, 100 and 111, respectively. Conditions of the stability of the equilibrium state have been found. For (100), (110) and (111) films a simple technique for determining the magnetic parameters of the films by the use of the spectra of magnetostatic waves has been proposed. For those films the magnetic permeability tensor has been obtained. Different algorithms have been proposed for processing the MSW spectra.

  4. Fluorination of epitaxial oxides: Creating ferrite and nickelate oxyfluoride films

    NASA Astrophysics Data System (ADS)

    May, Steven; Moon, Eun; Xie, Yujun; Keavney, David; Goebel, Justin; Laird, Eric; Li, Christopher

    2013-03-01

    In ABO3 perovskites, the physical properties are directly coupled to the nominal valence state of the B-site cation. In epitaxial thin films, the dominant strategy to control B-site valence is through the selection of a di- or trivalent cation on the A-site. However, this approach is limited, particularly when electron doping on the B-site is desired. Here we report a simple method for realizing oxyfluoride films, where the substitution of F for O is expected to reduce the B-site valence, providing a new means to tune electronic, optical and magnetic properties in thin films. Fluorination is achieved by spin coating an oxygen deficient film with poly(vinylidene fluoride). The film/polymer bilayer is then annealed, promoting the diffusion of F into the film. We have used this method to synthesize SrFeO3-δFδ and LaNiO3-δFδ (δ ? 0.5) films, as confirmed by x-ray photoemission spectroscopy and x-ray absorption spectroscopy. This work is supported by the U. S. Army Research Office under grant number W911NF-12-1-0132. Work at the Advanced Photon Source is supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences under contract DE-AC02-06CH11357.

  5. thin films grown with additional NaF layers

    NASA Astrophysics Data System (ADS)

    Kim, Gee Yeong; Kim, Juran; Jo, William; Son, Dae-Ho; Kim, Dae-Hwan; Kang, Jin-Kyu

    2014-10-01

    CZTS precursors [SLG/Mo (300 nm)/ZnS (460 nm)/SnS (480 nm)/Cu (240 nm)] were deposited by RF/DC sputtering, and then NaF layers (0, 15, and 30 nm) were grown by electron beam evaporation. The precursors were annealed in a furnace with Se metals at 590°C for 20 minutes. The final composition of the CZTSSe thin-films was of Cu/(Zn + Sn) ~ 0.88 and Zn/Sn ~ 1.05, with a metal S/Se ratio estimated at ~0.05. The CZTSSe thin-films have different NaF layer thicknesses in the range from 0 to 30 nm, achieving a ~3% conversion efficiency, and the CZTSSe thin-films contain ~3% of Na. Kelvin probe force microscopy was used to identify the local potential difference that varied according to the thickness of the NaF layer on the CZTSSe thin-films. The potential values at the grain boundaries were observed to increase as the NaF thickness increased. Moreover, the ratio of the positively charged GBs in the CZTSSe thin-films with an NaF layer was higher than that of pure CZTSSe thin-films. A positively charged potential was observed around the grain boundaries of the CZTSSe thin-films, which is a beneficial characteristic that can improve the performance of a device.

  6. Different variation behaviors of resistivity for high-temperature-grown and low-temperature-grown p-GaN films

    NASA Astrophysics Data System (ADS)

    Jing, Yang; De-Gang, Zhao; De-Sheng, Jiang; Ping, Chen; Zong-Shun, Liu; Jian-Jun, Zhu; Ling-Cong, Le; Xiao-Jing, Li; Xiao-Guang, He; Li-Qun, Zhang; Hui, Yang

    2016-02-01

    Two series of p-GaN films grown at different temperatures are obtained by metal organic chemical vapor deposition (MOCVD). And the different variation behaviors of resistivity with growth condition for high- temperature(HT)-grown and low-temperature(LT)-grown p-GaN films are investigated. It is found that the resistivity of HT-grown p-GaN film is nearly unchanged when the NH3 flow rate or reactor pressure increases. However, it decreases largely for LT-grown p-GaN film. These different variations may be attributed to the fact that carbon impurities are easy to incorporate into p-GaN film when the growth temperature is low. It results in a relatively high carbon concentration in LT-grown p-GaN film compared with HT-grown one. Therefore, carbon concentration is more sensitive to the growth condition in these samples, ultimately, leading to the different variation behaviors of resistivity for HT- and LT-grown ones. Project supported by the National Natural Science Foundation of China (Grant Nos. 61474110, 61377020, 61376089, 61223005, and 61176126), the National Natural Science Fund for Distinguished Young Scholars, China (Grant No. 60925017), the One Hundred Person Project of the Chinese Academy of Sciences, and the Basic Research Project of Jiangsu Province, China (Grant No. BK20130362).

  7. Temperature dependence of FMR and magnetization in nanocrystalline zinc ferrite thin films

    NASA Astrophysics Data System (ADS)

    Sahu, B. N.; Doshi, Akash S.; Prabhu, R.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

    2016-05-01

    Single phase nano-crystalline zinc ferrite thin films were deposited by RF-magnetron sputtering on quartz substrate at room temperature (RT) in pure Argon environment and annealed (in air) at different temperatures. Temperature dependence of magnetization was studied on these films using both VSM and by observing FMR (in X band). Value of exchange stiffness constant (D) was obtained by fitting Bloch's law to the low temperature magnetization data. The value of D decreased monotonously with the annealing temperature (TA) of the samples. A film annealed at TA = 523 K, exhibited the highest magnetization value. The FMR line width of the films decreased with increase in measurement temperature. At RT (˜293 K), the lowest value of line width (ΔH) was 15 kA/m and 13 kA/m in parallel and perpendicular configuration respectively for the sample annealed at TA = 623 K.

  8. Properties of AlN film grown on Si (111)

    NASA Astrophysics Data System (ADS)

    Dai, Yiquan; Li, Shuiming; Sun, Qian; Peng, Qing; Gui, Chengqun; Zhou, Yu; Liu, Sheng

    2016-02-01

    Stress and strain in an AlN film grown on Si (111) substrate have been evaluated by measuring Raman frequency shifts. Mechanical properties and phonon deformation potentials of AlN are evaluated by first principles calculations. The calculation model is verified by comparing the calculated Raman frequencies and frequencies detected from a bulk single crystal. Results show that the two sets of frequencies agree very well with each other. Thus, with the same verified model and parameters, elastic constants and phonon deformation potentials are calculated. Additionally, we successfully develop a numerical model to verify the calculation above and the model itself is also useful to predict properties of crystal films. Finally, the stress, strain, and piezoelectric properties are analyzed and compared for films on different substrates.

  9. Characterization of graphene grown on bulk and thin film nickel.

    PubMed

    Lu, Chun-Chieh; Jin, Chuanhong; Lin, Yung-Chang; Huang, Chi-Ruei; Suenaga, Kazu; Chiu, Po-Wen

    2011-11-15

    We report on graphene films grown by atmospheric pressure chemical vapor deposition on bulk and thin film nickel. Carbon precipitation on the polycrystalline grains is controlled by the methane concentration and substrate cooling rate. It is found that graphene grows over multiple grains, with edges terminating along the grain boundaries and with dimensions directly correlated to the size of the underlying grains. This greatly restricts the resulting graphene size (<10 μm) in the thin film growth, whereas monolayer graphene with linear dimensions of hundreds of micrometers takes up the great majority of the surface overlayers on the bulk nickel (>50%). In addition, the number of layers can be better controlled in the bulk growth. Characterizations of the graphene sheets using transmission electron microscopy, Raman spectroscopy, and transport measurements in the field-effect configuration are also discussed. PMID:21967558

  10. Magnetic domain structure in nanocrystalline Ni-Zn-Co spinel ferrite thin films using off-axis electron holography

    SciTech Connect

    Zhang, D.; Ray, N. M.; Petuskey, W. T.; Smith, D. J.; McCartney, M. R.

    2014-08-28

    We report a study of the magnetic domain structure of nanocrystalline thin films of nickel-zinc ferrite. The ferrite films were synthesized using aqueous spin-spray coating at low temperature (∼90 °C) and showed high complex permeability in the GHz range. Electron microscopy and microanalysis revealed that the films consisted of columnar grains with uniform chemical composition. Off-axis electron holography combined with magnetic force microscopy indicated a multi-grain domain structure with in-plane magnetization. The correlation between the magnetic domain morphology and crystal structure is briefly discussed.

  11. Structure property relationships of carbonaceous films grown under ion enhancement

    SciTech Connect

    Weissmantel, C.; Ackermann, E.; Bewilogua, K.; Hecht, G.; Kupfer, H.; Rau, B.

    1986-11-01

    Based on our own results and in comparison with data published by other groups the structure property relationships of carbon and carbon/metal films prepared by sputtering and deposition of partially ionized species are discussed. Films grown by ion beam sputtering are dark brownish and amorphous with a small fraction of microcrystals. However, a transition to transparent and insulating layers can be effected by ion bombardment. C/Me coatings, where Me stands for Ti or Sn, were obtained by magnetron sputtering of composite targets. The films proved to be amorphous up to metal concentrations of more than 10 at. %, but metal and carbide crystals grow upon annealing. Measurements of the hardness, the electrical conductivity, and the contact behavior in dependence on the composition provided interesting information. For carbon films prepared by deposition of partially ionized benzene species it has been found that the properties depend characteristically on the ion energy; typical ''diamondlike'' i-C films are obtained by applying a bias voltage from 1--3 keV. The thermal stability of the amorphous coatings is discussed in conjunction with their electrical conductivity. Summarizing extensive structure investigations, a structure model based on tetrahedrally interlinked carbon rings is proposed. Composites of the type i-C/Me (Me: Al, Ti, Cr), which were prepared by simultaneous metal evaporation, exhibit a wide range of structure property relations.

  12. Growth of epitaxial films of iron oxide, nickel oxide, cobalt oxide, strontium hexagonal ferrite, and yttrium iron garnet by laser ablation (abstract)

    SciTech Connect

    Kennedy, R.J.

    1996-04-01

    Thin films of iron oxide, nickel oxide, cobalt oxide, strontium hexagonal ferrite, and yttrium iron garnet have been grown by laser ablation. With the exception of Co{sub 3}O{sub 4} deposited on LaAlO{sub 3}, the first three materials deposited on [100] LaAlO{sub 3}, SrTiO{sub 3}, and MgO result in high quality {ital c} axis [100] growth. Co{sub 3}O{sub 4} deposited on LaAlO{sub 3} produces highly oriented but random in-plane growth. Similar highly oriented but random in-plane growth occurs for all three materials deposited on glass. The same three materials deposited on cubic zirconia grow [111] oriented and twinned. Strontium hexagonal ferrite and yttrium iron garnet have been deposited on [111] large lattice constant garnet. Epitaxial [0001] films are obtained for the former while the latter gives [111]-oriented films. For yttrium iron garnet the closeness of lattice match to the substrate necessitates that the mosaicity (rocking curves) obtained from area maps be compared to the growth temperatures and pressures to determine the optimum growth conditions for epitaxiality. {copyright} {ital 1996 American Institute of Physics.}

  13. Investigation on two magnon scattering processes in pulsed laser deposited epitaxial nickel zinc ferrite thin film

    NASA Astrophysics Data System (ADS)

    Roy, Debangsu; Sakshath, S.; Singh, Geetanjali; Joshi, Rajeev; Bhat, S. V.; Kumar, P. S. Anil

    2015-04-01

    Ferromagnetic resonance (FMR) measurements are employed to evaluate the presence of the two magnon scattering contribution in the magnetic relaxation processes of the epitaxial nickel zinc ferrite thin films deposited using pulsed laser deposition (PLD) on the (0 0 1) MgAl2O4 substrate. Furthermore, the reciprocal space mapping reveals the presence of microstructural defects which acts as an origin for the two magnon scattering process in this thin film. The relevance of this scattering process is further discussed for understanding the higher FMR linewidth in the in-plane configuration compared to the out-of-plane configuration. FMR measurements also reveal the presence of competing uniaxial and cubic anisotropy in the studied films.

  14. Tailoring the optical bandgap and magnetization of cobalt ferrite thin films through controlled zinc doping

    NASA Astrophysics Data System (ADS)

    Sharma, Deepanshu; Khare, Neeraj

    2016-08-01

    In this report, the tuning of the optical bandgap and saturation magnetization of cobalt ferrite (CFO) thin films through low doping of zinc (Zn) has been demonstrated. The Zn doped CFO thin films with doping concentrations (0 to 10%) have been synthesized by ultrasonic assisted chemical vapour deposition technique. The optical bandgap varies from 1.48 to 1.88 eV and saturation magnetization varies from 142 to 221 emu/cc with the increase in the doping concentration and this change in the optical and magnetic properties is attributed to the change in the relative population of the Co2+ at the tetrahedral and octahedral sites. Raman study confirms the decrease in the population of Co2+ at tetrahedral sites with controlled Zn doping in CFO thin films. A quantitative analysis has been presented to explain the observed variation in the optical bandgap and saturation magnetization.

  15. Magnetoactive feature of in-situ polymerised polyaniline film developed on the surface of manganese-zinc ferrite

    NASA Astrophysics Data System (ADS)

    Babayan, V.; Kazantseva, N. E.; Sapurina, I.; Moučka, R.; Vilčáková, J.; Stejskal, J.

    2012-07-01

    A polyaniline film exhibits magnetoactive properties when deposited on the surface of multidomain particles of manganese-zinc ferrite during in-situ polymerisation of aniline. This is reflected in the increased coercivity and thermomagnetic stability of an in-situ prepared composite compared with bare ferrite and its mixed composite with polyaniline. In addition, the deposition of a polyaniline film results in a shift of the complex-permeability dispersion region towards ultrahigh frequency band. These changes in the magnetic properties of polyaniline-coated ferrite are attributed to the increased value of the inner demagnetisation factor, which results from stress-induced magnetic anisotropy due to the pinning of domain walls appearing on the surface of ferrite. This study is focused on the mechanism of pinning of domain walls and its influence on the magnetic properties of in-situ prepared composites in terms of the molecular mechanism of oxidative polymerisation of aniline. Ferrite stimulates the propagation of polyaniline chains, which start to grow on the domain walls on the ferrite surface. It leads to the pinning of domain walls and restricts their mobility in a magnetic field. The further increase in the coercivity and the resonance frequency of polyaniline-coated ferrite due to film shrinkage after deprotonation of polyaniline makes it obvious that polyaniline coating induces elastic stresses in a ferrite particle that stimulate the growth of the effective magnetic anisotropy. Stress-induced magnetic anisotropy contributes to the reorientation of the magnetisation vectors in domains with respect to the new directions of easy magnetisation, given by magnetoelastic stresses, which leads to complex changes in the magnetic properties of in-situ prepared composites.

  16. Cathodic arc grown niobium films for RF superconducting cavity applications

    NASA Astrophysics Data System (ADS)

    Catani, L.; Cianchi, A.; Lorkiewicz, J.; Tazzari, S.; Langner, J.; Strzyzewski, P.; Sadowski, M.; Andreone, A.; Cifariello, G.; Di Gennaro, E.; Lamura, G.; Russo, R.

    2006-07-01

    Experimental results on the characterization of the linear and non-linear microwave properties of niobium film produced by UHV cathodic arc deposition are presented. Surface impedance Zs as a function of RF field and intermodulation distortion (IMD) measurement have been carried out by using a dielectrically loaded resonant cavity operating at 7 GHz. The experimental data show that these samples have a lower level of intrinsic non-linearities at low temperature and low circulating power in comparison with Nb samples grown by sputtering. These results make UHV cathodic arc deposition a promising technique for the improvement of RF superconducting cavities for particle accelerators.

  17. Atomically flat nickel film grown on synthetic mica

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroyuki; Taniguchi, Masateru

    2016-07-01

    We have grown nickel heteroepitaxially on muscovite and synthetic mica in vacuo for use as substrates for scanning probe microscopy (SPM) and graphene formation. We have determined annealing conditions that could generate atomically flat surfaces (with rms surface roughness of less than 1 nm). Owing to accelerated degradation at temperatures above 600 °C, muscovite mica was unsuitable as a substrate at high growth temperatures. Thermally stable synthetic fluorophlogopite mica [KMg3(AlSi3O10)F2], on the other hand, was found to be stable at 800 °C and successfully employed for the formation of atomically flat films.

  18. Experimental and Numerical Study on the Effect of ZDDP Films on Sticking During Hot Rolling of Ferritic Stainless Steel Strip

    NASA Astrophysics Data System (ADS)

    Hao, Liang; Jiang, Zhengyi; Wei, Dongbin; Gong, Dianyao; Cheng, Xiawei; Zhao, Jingwei; Luo, Suzhen; Jiang, Laizhu

    2016-08-01

    The aim of this study is to investigate the effect of zinc dialkyl dithio phosphate (ZDDP) films on sticking during hot rolling of a ferritic stainless steel strip. The surface characterization and crack propagation of the oxide scale are very important for understanding the mechanism of the sticking. The high-temperature oxidation of one typical ferritic stainless was conducted at 1373 K (1100 °C) for understanding its microstructure and surface morphology. Hot-rolling tests of a ferritic stainless steel strip show that no obvious cracks among the oxide scale were observed with the application of ZDDP. A finite element method model was constructed with taking into consideration different crack size ratios among the oxide scale, surface profile, and ZDDP films. The simulation results show that the width of the crack tends to be reduced with the introduction of ZDDP films, which is beneficial for improving sticking.

  19. Growth and crystallographic feature-dependent characterization of spinel zinc ferrite thin films by RF sputtering

    PubMed Central

    2013-01-01

    ZnFe2O4 (ZFO) thin films exhibiting varying crystallographic features ((222)-epitaxially, (400)-epitaxially, and randomly oriented films) were grown on various substrates by radio-frequency magnetron sputtering. The type of substrate used profoundly affected the surface topography of the resulting ZFO films. The surface of the ZFO (222) epilayer was dense and exhibited small rectangular surface grains; however, the ZFO (400) epilayer exhibited small grooves. The surface of the randomly oriented ZFO thin film exhibited distinct three-dimensional island-like grains that demonstrated considerable surface roughness. Magnetization-temperature curves revealed that the ZFO thin films exhibited a spin-glass transition temperature of approximately 40 K. The crystallographic orientation of the ZFO thin films strongly affected magnetic anisotropy. The ZFO (222) epitaxy exhibited the strongest magnetic anisotropy, whereas the randomly oriented ZFO thin film exhibited no clear magnetic anisotropy. PMID:24354428

  20. Persistent conductive footprints of 109° domain walls in bismuth ferrite films

    SciTech Connect

    Stolichnov, I.; Iwanowska, M.; Colla, E.; Setter, N.; Ziegler, B.; Gaponenko, I.; Paruch, P.; Huijben, M.; Rijnders, G.

    2014-03-31

    Using conductive and piezoforce microscopy, we reveal a complex picture of electronic transport at weakly conductive 109° domain walls in bismuth ferrite films. Even once initial ferroelectric stripe domains are changed/erased, persistent conductive paths signal the original domain wall position. The conduction at such domain wall “footprints” is activated by domain movement and decays rapidly with time, but can be re-activated by opposite polarity voltage. The observed phenomena represent true leakage conduction rather than merely displacement currents. We propose a scenario of hopping transport in combination with thermionic injection over interfacial barriers controlled by the ferroelectric polarization.

  1. Enhancement of rotatable anisotropy in ferrite doped FeNi thin film with oblique sputtering

    NASA Astrophysics Data System (ADS)

    Zhou, Cai; Jiang, Changjun; Zhao, Zhong

    2015-07-01

    Rotatable anisotropy of stripe domain (SD) was investigated in a ferrite doped FeNi thin film with different oblique angles. Rotation of SD under an in-plane magnetic field was observed by magnetic force microscopy, suggesting the existence of rotatable anisotropy. A rotatable anisotropy field Hrot was derived from the fitting curves of the in-plane resonance field versus the angle between the orientation of easy axis and applied field. As the oblique angle increases, an increase of Hrot from 305 Oe to 468 Oe was observed and the perpendicular anisotropy increased as well, indicating a correlation between rotatable anisotropy and perpendicular anisotropy.

  2. Electron theory of perpendicular magnetic anisotropy of Co-ferrite thin films

    SciTech Connect

    Inoue, Jun-ichiro; Yanagihara, Hideto; Kita, Eiji; Niizeki, Tomohiko; AIMR, Tohoku University, Sendai 980-8577 ; Itoh, Hiroyoshi

    2014-02-15

    We develop an electron theory for the t{sub 2g} electrons of Co{sup 2+} ions to clarify the perpendicular magnetic anisotropy (PMA) mechanism of Co-ferrite thin films by considering the spin-orbit interaction (SOI) and crystal-field (CF) potentials induced by the local symmetry around the Co ions and the global tetragonal symmetry of the film. Uniaxial and in-plane MA constants K{sub u} and K{sub 1} at 0 K, respectively, are calculated for various values of SOI and CF. We show that reasonable parameter values explain the observed PMA and that the orbital moment for the in-plane magnetization reduces to nearly half of that of the out-of-plane magnetization.

  3. Bismuth ferrite based thin films, nanofibers, and field effect transistor devices

    NASA Astrophysics Data System (ADS)

    Rivera-Beltran, Rut

    In this research an attempt has been made to explore bismuth ferrite thin films with low leakage current and nanofibers with high photoconductivity. Thin films were deposited with pulsed laser deposition (PLD) method. An attempt has been made to develop thin films under different deposition parameters with following target compositions: i) 0.6BiFeO3-0.4(Bi0.5 K0.5)TiO3 (BFO-BKT) and ii) bi-layered 0.88Bi 0.5Na0.5TiO3-0.08Bi0.5K0.5TiO 3-0.04BaTiO3/BiFeO3 (BNT-BKT-BT/BFO). BFO-BKT thin film shows suppressed leakage current by about four orders of magnitude which in turn improve the ferroelectric and dielectric properties of the films. The optimum remnant polarization is 19 muC.cm-2 at the oxygen partial pressure of 300 mtorr. The BNT-BKT-BT/BFO bi-layered thin films exhibited ferroelectric behavior as: Pr = 22.0 muC.cm-2, Ec = 100 kV.cm-1 and epsilonr = 140. The leakage current of bi-layered thin films have been reduced two orders of magnitude compare to un-doped bismuth ferrite. Bismuth ferrite nanofibers were developed by electrospinning technique and its electronic properties such as photoconductivity and field effect transistor performance were investigated extensively. Nanofibers were deposited by electrospinning of sol-gel solution on SiO2/Si substrate at driving voltage of 10 kV followed by heat treatment at 550 °C for 2 hours. The composition analysis through energy dispersive detector and electron energy loss spectroscopy revealed the heterogeneous nature of the composition with Bi rich and Fe deficient regions. X-ray photoelectron spectroscopy results confirmed the combination of Fe3+ and Fe2+ valence state in the fibers. The photoresponse result is almost hundred times higher for a fiber of 40 nm diameter compared to a fiber with 100 nm diameter. This effect is described by a size dependent surface recombination mechanism. A single and multiple BFO nanofibers field effect transistors devices were fabricated and characterized. Bismuth ferrite FET behaves

  4. Cation Engineering of Cu-ferrite Films Deposited by Alternating Target Laser Ablation Deposition

    SciTech Connect

    Yang,A.; Chen, Z.; Islam, S.; Vittoria, C.; Harris, V.

    2008-01-01

    Epitaxial copper ferrite thin films were deposited on MgO substrates by the alternating target laser ablation deposition method. A series of films was studied to explore the impact of oxygen operating pressure, substrate temperature, and the ratio of laser shots incident on each target upon the magnetic, structural, and atomic structural properties. The highest saturation magnetization, 2800?G, was achieved at a 90?mTorr oxygen pressure and at 650? C for the substrate temperature. This value is 65% higher than the room temperature magnetization for bulk equilibrium samples. The inversion parameter was measured by extended x-ray absorption fine structure analysis. The sample having the highest saturation magnetization had a corresponding inversion parameter (percentage of Cu ion octahedral site occupancy) of 51.5% compared with the bulk value of 85%.

  5. Perpendicularly oriented barium ferrite thin films with low microwave loss, prepared by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Da-Ming, Chen; Yuan-Xun, Li; Li-Kun, Han; Chao, Long; Huai-Wu, Zhang

    2016-06-01

    Barium ferrite (BaM) thin films are deposited on platinum coated silicon wafers by pulsed laser deposition (PLD). The effects of deposition substrate temperature on the microstructure, magnetic and microwave properties of BaM thin films are investigated in detail. It is found that microstructure, magnetic and microwave properties of BaM thin film are very sensitive to deposition substrate temperature, and excellent BaM thin film is obtained when deposition temperature is 910 °C and oxygen pressure is 300 mTorr (1 Torr = 1.3332 × 102 Pa). X-ray diffraction patterns and atomic force microscopy images show that the best thin film has perpendicular orientation and hexagonal morphology, and the crystallographic alignment degree can be calculated to be 0.94. Hysteresis loops reveal that the squareness ratio (M r/M s) is as high as 0.93, the saturated magnetization is 4004 Gs (1 Gs = 104 T), and the anisotropy field is 16.5 kOe (1 Oe = 79.5775 A·m‑1). Ferromagnetic resonance measurements reveal that the gyromagnetic ratio is 2.8 GHz/kOe, and the ferromagnetic resonance linewith is 108 Oe at 50 GHz, which means that this thin film has low microwave loss. These properties make the BaM thin films have potential applications in microwave devices. Project supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (Grant No. KFJJ201506), the Scientific Research Starting Foundation of Hainan University (Grant No. kyqd1539), and the Natural Science Foundation of Hainan Province (Grant No. 20165187).

  6. The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

    NASA Astrophysics Data System (ADS)

    Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

    2016-04-01

    Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

  7. Method of fabricating low-dislocation-density epitaxially-grown films with textured surfaces

    DOEpatents

    Li, Qiming; Wang, George T

    2015-01-13

    A method for forming a surface-textured single-crystal film layer by growing the film atop a layer of microparticles on a substrate and subsequently selectively etching away the microparticles to release the surface-textured single-crystal film layer from the substrate. This method is applicable to a very wide variety of substrates and films. In some embodiments, the film is an epitaxial film that has been grown in crystallographic alignment with respect to a crystalline substrate.

  8. Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

    SciTech Connect

    R, Lisha; P, Geetha; B, Aravind P.; Anantharaman, M. R.; T, Hysen; Ojha, S.; Avasthi, D. K.; Ramanujan, R. V.

    2015-06-24

    The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

  9. Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

    NASA Astrophysics Data System (ADS)

    R, Lisha; T, Hysen; P, Geetha; B, Aravind P.; Ojha, S.; Avasthi, D. K.; Ramanujan, R. V.; Anantharaman, M. R.

    2015-06-01

    The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

  10. The magnetic and magneto-optical properties of Co, Cr, Mn, and Ni substituted barium ferrite films

    NASA Astrophysics Data System (ADS)

    Carey, R.; Gago-Sandoval, P. A.; Newman, D. M.; Thomas, B. W. J.

    1994-05-01

    Using rapid thermal processing (RTP) we recently demonstrated the production of high quality well ordered barium ferrite films in times much shorter than those required by a conventional annealing process. Influence over the magnetic and structural properties developed in annealed samples was also achieved by variation of the RTP heating profile (R. Carey, P. A. Gago-Sandoval, D. M. Newman, and B. W. J. Thomas, presented at Intermag-93, Stockholm, April 13-16, 1993). It is known that the magneto-optic properties of barium ferrite can be enhanced by selective substitution of some of the Fe by Co2+ and Ti4+ albeit at the expense of reducing the magnetic anisotropy. A multitarget scanning cosputtering process has been used in conjunction with rapid thermal processing to produce a series of barium ferrite films in which Co, Cr, Mn, Ni are selectively introduced to substitute for between 5 and 20 at. % of the Fe. A corresponding percentage of Ti is also added to maintain charge compensation. The magnetic and magneto-optic properties of these films are presented and discussed with reference to their composition and treatment respect to the properties of barium ferrite.

  11. Spin-spray deposited NiZn-Ferrite films exhibiting μr' > 50 at GHz range

    NASA Astrophysics Data System (ADS)

    Obi, Ogheneyunume; Liu, Ming; Lou, Jing; Stoute, Stephen; Xing, Xing; Sun, Nian X.; Warzywoda, Juliusz; Sacco, Albert; Oates, Daniel E.; Dionne, Gerald F.

    2011-04-01

    Ni0.27ZnxFe2.73-xO4 (with x = 0.03-0.1) thin films with high real permeability μr' in the GHz range were fabricated by the spin spray process onto glass substrates in the presence of an external magnetic field of 360 Oe. These films exhibit high permeabilities that exceeded the Snoek limit for bulk NiZn-ferrite films and those previously reported for spin spray deposited ferrites. The NiZn-ferrite film with x = 0.06 is low in magnetic losses, having tanδm (μr″/μr') ˜ 0.027 from 1 to 1.5 GHz, and a high ferromagnetic resonance (FMR) frequency of 2.7 GHz, while the x = 0.1 film exhibited a high μr' of ˜50 and μr″ > 50 at 1 GHz. These properties are ideal for microwave applications such as antennas, inductors and electromagnetic interference (EMI) suppression in the GHz range.

  12. Direct evidence for the spin cycloid in strained nanoscale bismuth ferrite thin films.

    PubMed

    Bertinshaw, Joel; Maran, Ronald; Callori, Sara J; Ramesh, Vidya; Cheung, Jeffery; Danilkin, Sergey A; Lee, Wai Tung; Hu, Songbai; Seidel, Jan; Valanoor, Nagarajan; Ulrich, Clemens

    2016-01-01

    Magnonic devices that utilize electric control of spin waves mediated by complex spin textures are an emerging direction in spintronics research. Room-temperature multiferroic materials, such as bismuth ferrite (BiFeO3), would be ideal candidates for this purpose. To realize magnonic devices, a robust long-range spin cycloid with well-known direction is desired, since it is a prerequisite for the magnetoelectric coupling. Despite extensive investigation, the stabilization of a large-scale uniform spin cycloid in nanoscale (100 nm) thin BiFeO3 films has not been accomplished. Here, we demonstrate cycloidal spin order in 100 nm BiFeO3 thin films through the careful choice of crystallographic orientation, and control of the electrostatic and strain boundary conditions. Neutron diffraction, in conjunction with X-ray diffraction, reveals an incommensurate spin cycloid with a unique [11] propagation direction. While this direction is different from bulk BiFeO3, the cycloid length and Néel temperature remain equivalent to bulk at room temperature. PMID:27585637

  13. Photoresponse properties of BaSi2 film grown on Si (100) by vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Thi Trinh, Cham; Nakagawa, Yoshihiko; Hara, Kosuke O.; Takabe, Ryota; Suemasu, Takashi; Usami, Noritaka

    2016-07-01

    We have succeeded in the observation of high photoresponsivity of orthorhombic BaSi2 film grown on crystalline Si by a vacuum evaporation method, raising the prospect of its promising application in high-efficiency thin-film solar cells. Photocurrent was observed at photon energies larger than 1.28 eV, which corresponds to the band gap of evaporated BaSi2 film, indicating that the photoresponsivity originates from the BaSi2 film. The effect of the substrate temperature on the film’s properties was also investigated. The films grown at a substrate temperature larger than 500 °C are single-phase polycrystalline BaSi2 films, while those grown at a substrate temperature of 400 °C is a mixture of phases. We confirmed that undoped evaporated BaSi2 films are an n-type material with high carrier concentration. High carrier lifetime of 4.8 and 2.7 μs can be found for the films grown at 500 °C and 400 °C, respectively. BaSi2 film grown at a substrate temperature of 500 °C, which is crack-free and single-phase, shows the best photoresponsivity. The maximum value of photocurrent was obtained at photon energy of 1.9 eV, corresponding to an external quantum efficiency of 22% under reverse applied voltage of 2 V.

  14. Defect Characterization in Ge/(001)Si Epitaxial Films Grown by Reduced-Pressure Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Bharathan, Jayesh; Narayan, Jagdish; Rozgonyi, George; Bulman, Gary E.

    2013-10-01

    We studied the microstructural characteristics and electrical properties of epitaxial Ge films grown on Si(001) substrates by x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The films were grown using a two-step technique by reduced-pressure chemical vapor deposition, where the first step promotes two-dimensional growth at a lower substrate temperature. We observed a decrease in defect density with increasing film thickness. Ge films with thickness of 3.5 μm exhibited threading dislocation densities of 5 × 106 cm-2, which yielded devices with dark current density of 5 mA cm-2 (1 V reverse bias). We also noted the presence of stacking faults in the form of lines in the films and establish that this is an important defect for Ge films grown by this deposition technique.

  15. Crystal structure of thin oxide films grown on Zr-Nb alloys studied by RHEED

    NASA Astrophysics Data System (ADS)

    Khatamian, D.; Lalonde, S. D.

    1997-05-01

    The highly surface sensitive reflection high energy electron diffraction (RHEED) technique was used to determine thecrystal structure of oxide films grown on Zr-Nb alloys in air up to 673 K. The results show that the oxide films grown on Zr-2.5 wt% Nb(α-Zr + β-Zr) have a mixture of nearly-cubic-tetragona and monoclinic structures for films of 200 nm thick or less and that the outer layers of films thicker than 800 nm only have the monoclinic crystal structure. However, oxide films grown on Zr-20 wt% Nb (β-Zr) have a stabilized nearly-cubic-tetragonal structure for all film thicknesses, studied here, up to 2100 nm.

  16. Enhanced performance of room-temperature-grown epitaxial thin films of vanadium dioxide

    SciTech Connect

    Nag, Joyeeta; Payzant, E Andrew; More, Karren Leslie; HaglundJr., Richard F

    2011-01-01

    Stoichiometric vanadium dioxide in bulk, thin film and nanostructured forms exhibits an insulator-to-metal transition (IMT) accompanied by a structural phase transformation, induced by temperature, light, electric fields, doping or strain. We have grown epitaxial films of vanadium dioxide on c-plane (0001) of sapphire using two different procedures involving (1) room temperature growth followed by annealing and (2) direct high temperature growth. Strain at the film-substrate interface due to growth at different temperatures leads to interesting differences in morphologies and phase transition characteristics. Comparison of the morphologies and switching characteristics of the two films shows that contrary to conventional wisdom, the room-temperature grown films have smoother, more continuous morphologies and better switching performance, consistent with the behavior of epitaxially grown semiconductors.

  17. Mapping strain modulated electronic structure perturbations in mixed phase bismuth ferrite thin films

    SciTech Connect

    Krishnan, P.S. Sanakara R.; Aguiar, Jeffery A.; Ramasse, Q. M.; Kepaptsoglou, D. M.; Liang, W. I.; Chu, Y. H.; Browning, Nigel D.; Munroe, Paul R.; Nagarajan, Valanoor

    2015-01-01

    Strain engineering of epitaxial ferroelectrics has emerged as a powerful method to tailor the electromechanical response of these materials, although the effect of strain at the atomic scale and the interplay between lattice displacements and electronic structure changes are not yet fully understood. Here, using a combination of scanning transmission electron microscopy (STEM) and density functional theory (DFT), we systematically probe the role of epitaxial strain in mixed phase bismuth ferrite thin films. Electron energy loss O K and Fe L2,3 edge spectra acquired across the rhombohedral (R)-tetragonal (T) phase boundary reveal progressive, and systematic changes, in electronic structure going from one phase to the other. The comparison of the acquired spectra, with theoretical simulations using DFT, suggests a breakage in the structural symmetry across the boundary due to the simultaneous presence of increasing epitaxial strain and off- axial symmetry in the T phase. This implies that the imposed epitaxial strain plays a significant role in not only changing the crystal-field geometry, but also the bonding environment surrounding the central iron cation at the interface thus providing new insights and a possible link to understand how the imposed strain could perturb magnetic ordering in the T phase BFO.

  18. Temperature threshold for nanorod structuring of metal and oxide films grown by glancing angle deposition

    SciTech Connect

    Deniz, Derya; Lad, Robert J.

    2011-01-15

    Thin films of tin (Sn), aluminum (Al), gold (Au), ruthenium (Ru), tungsten (W), ruthenium dioxide (RuO{sub 2}), tin dioxide (SnO{sub 2}), and tungsten trioxide (WO{sub 3}) were grown by glancing angle deposition (GLAD) to determine the nanostructuring temperature threshold, {Theta}{sub T}, above which adatom surface diffusion becomes large enough such that nanorod morphology is no longer formed during growth. The threshold was found to be lower in metals compared to oxides. Films were grown using both dc and pulsed dc magnetron sputtering with continuous substrate rotation over the temperature range from 291 to 866 K. Film morphologies, structures, and compositions were characterized by high resolution scanning electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Films were also grown in a conventional configuration for comparison. For elemental metals, nanorod structuring occurs for films with melting points higher than that of Al (933 K) when grown at room temperature with a rotation rate of {approx}5 rpm, corresponding to a value of {Theta}{sub T}{approx_equal}0.33{+-}0.01. For the oxide films, a value of {Theta}{sub T}{approx_equal}0.5 was found, above which GLAD nanorod structuring does not occur. The existence of a nanostructuring temperature threshold in both metal and oxide GLAD films can be attributed to greater adatom mobilities as temperature is increased resulting in nonkinetically limited film nucleation and growth processes.

  19. Oxide Ceramic Films Grown on 60 Nitinol for NASA and Department of Defense Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Street, Kenneth W.; Lukco, Dorothy; Cytron, Sheldon J.

    2005-01-01

    Both the NASA Glenn Research Center and the U.S. Army Research Laboratory, Development and Engineering Center (ARDEC) have worked to develop oxide ceramic films grown on 60 nitinol (60-wt% nickel and 40-wt% titanium) to decrease friction and increase wear resistance under unlubricated conditions. In general, oxide and nonoxide ceramic films have unique capabilities as mechanical-, chemical-, and thermal-barrier materials in diverse applications, including high-temperature bearings and gas bearings requiring low friction, wear resistance, and chemical stability. All oxide ceramic films grown on 60 nitinol were furnished by ARDEC, and materials and surface characterization and tribological experiments were conducted at Glenn.

  20. Significance of microstructure for a MOCVD-grown YSZ thin film gas sensor

    SciTech Connect

    Vetrone, J.; Foster, C.; Bai, G.

    1996-11-01

    The authors report the fabrication and characterization of a low temperature (200--400 C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.

  1. Magnetic and structural properties of ultrafine Ni-Zn-Cu ferrite grown by a sol-gel method

    NASA Astrophysics Data System (ADS)

    Kim, Woo Chul; Park, Seung Iel; Kim, Sam Jin; Lee, Seung Wha; Kim, Chul Sung

    2000-05-01

    Ultrafine Ni0.65Zn0.35Cu0.2Fe1.8O4 particles were fabricated by a sol-gel method. The magnetic and structural properties of the powders were investigated with x-ray diffraction, vibrating sample magnetometer, and Mössbauer spectroscopy. Ni-Zn-Cu ferrite powders that were fired at and above 823 K have only a single phase spinel structure and behave ferrimagnetically. Powders annealed at 523, 623, and 723 K have a typical spinel structure and are simultaneously paramagnetic and ferrimagnetic in nature. The magnetic behavior of Ni-Zn-Cu ferrite powders fired at and above 623 K showed that an increase of the annealing temperature yielded a decrease of the coercivity and an increase of the saturation magnetization. The maximum coercivity and the saturation magnetization of Ni-Zn-Cu ferrite powders were Hc=96 Oe and Ms=68 emu/g. Mössbauer spectra of powder annealed at 1223 K were taken at various temperatures ranging from 12 to 675 K. As the temperature increased toward TN, a systematic line broadening effect in the Mössbauer spectra was observed and was interpreted as originating from the different temperature dependencies of the magnetic hyperfine fields at various iron sites. The isomer shifts indicated that the iron ions were ferric at the tetrahedral [A] and the octahedral site [B]. The Néel temperature was determined to be TN=675±2 K.

  2. Characterization of Nanoporous WO3 Films Grown via Ballistic Deposition

    SciTech Connect

    Smid, Bretislav; Li, Zhenjun; Dohnalkova, Alice; Arey, Bruce W.; Smith, R. Scott; Matolin, Vladimir; Kay, Bruce D.; Dohnalek, Zdenek

    2012-05-17

    We report on the preparation and characterization of high surface area, supported nanoporous tungsten oxide films prepared under different conditions on polished polycrystalline Ta and Pt(111) substrates via direct sublimation of monodispersed gas phase of cyclic (WO3)3 clusters. Scanning Electron Microscopy and Transmission Electron Microscopy were used to investigate the film morphology on a nanometer scale. The films consist of arrays of separated filaments that are amorphous. The chemical composition and the thermal stability of the films were investigated by means of X-ray Photoelectron Spectroscopy. The surface area and the distribution of binding sites on the films are measured as functions of growth temperature, deposition angle, and annealing conditions using temperature programmed desorption of Kr. Films deposited at 20 K and at an incident angle of 65{sup o} from substrate normal display the greatest specific surface area of {approx}560 m2/g.

  3. Multilayer permalloy films grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Rook, K.; Zeltser, A. M.; Artman, J. O.; Laughlin, D. E.; Kryder, M. H.

    1991-04-01

    The magnetic properties of single-layer and multilayer 111-line textured Cu and Permalloy films, deposited by MBE on 111-plane Si substrates, have been measured by both ferromagnetic resonance and M-H loop tracer; microstructural characterizations were conducted by TEM, XRD, and reflection high-energy electron diffraction. The single-layer films had lower easy-axis coercivity H(ce) and a lower in-plane anisotropy field than sputter-deposited Permalloy films of similar thickness. The five-layer, Cu-interlayer separated Permalloy structures, having a magnetic thickness in excess of 100 nm, exhibited lower H(ce) than equivalent single-layer films.

  4. Single-crystal semiconductor films grown on foreign substrates

    NASA Technical Reports Server (NTRS)

    Vohl, P.

    1966-01-01

    Intermediate alloy formed between foreign substrates and semiconductor material enable the growth of single crystal semiconductor films on the alloy layer. The melted film must not ball up on the surface of the substrate and neither chemically react nor alloy with the intermediate alloy formed on the substrate.

  5. Photoresponse in thin films of WO{sub 3} grown by pulsed laser deposition

    SciTech Connect

    Roy Moulik, Samik; Samanta, Sudeshna; Ghosh, Barnali

    2014-06-09

    We report, the photoresponse behaviour of Tungsten trioxide (WO{sub 3}) films of different surface morphology, grown by using pulsed laser deposition (PLD). The Growth parameters for PLD were changed for two substrates SiO{sub 2}/Si (SO) and SrTiO{sub 3} (STO), such a way which, result nanocrystalline film on SO and needle like structured film on STO. The photoresponse is greatly modified in these two films because of two different surface morphologies. The nanocrystalline film (film on SO) shows distinct photocurrent (PC) ON/OFF states when light was turned on/off, the enhancement of PC is ∼27%. Whereas, the film with needle like structure (film on STO) exhibits significantly enhanced persistent photocurrent even in light off condition, in this case, the enhancement of PC ∼ 50% at room temperature at lowest wavelength (λ = 360 nm) at a nominal bias voltage of 0.1 V.

  6. Surface phonons of NiO(001) ultrathin films grown pseudomorphically on Ag(001)

    NASA Astrophysics Data System (ADS)

    Kostov, K. L.; Polzin, S.; Schumann, F. O.; Widdra, W.

    2016-01-01

    For an ultrathin NiO(001) film of 4 monolayer (ML) thickness grown on Ag(001), the vibrational properties have been determined by high-resolution electron energy loss spectroscopy (HREELS). For the well-ordered pseudomorphically grown film, nine phonon modes have been identified and their dispersions have been revealed along the ΓbarΧbar high-symmetry direction. The comparison with phonon data for a 25 ML thick NiO(001) film shows that the NiO(001) phonon properties are already fully developed at 4 ML. Significant differences are found for the surface-localized phonon S6 which has an increased dispersion for the ultrathin film. The dipole-active Fuchs-Kliewer phonon-polariton exhibits a narrower lineshape than the mode found for a single-crystal surface, which might hint to a reduced antiferromagnetic coupling in the ultrathin film.

  7. Characterization of perovskite film prepared by pulsed laser deposition on ferritic stainless steel using microscopic and optical methods

    NASA Astrophysics Data System (ADS)

    Durda, E.; Jaglarz, J.; Kąc, S.; Przybylski, K.; El Kouari, Y.

    2016-06-01

    The perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF48) film was deposited on Crofer 22 APU ferritic stainless steel by pulsed laser deposition (PLD). Morphological studies of the sample were performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Information about film thickness and surface topography of the film and the steel substrate were obtained using following optical methods: spectroscopic ellipsometry (SE), bidirectional reflection distribution function (BRDF) and total integrated reflectometry (TIS). In particular, the BRDF study, being complementary to atomic force microscopy, yielded information about surface topography. Using the previously mentioned methods, the following statistic surface parameters were determined: root-mean square (rms) roughness and autocorrelation length by determining the power spectral density (PSD) function of surface irregularities.

  8. Structural and magnetic properties of zinc ferrite thin films irradiated by 90 keV neon ions

    NASA Astrophysics Data System (ADS)

    Gafton, E. V.; Bulai, G.; Caltun, O. F.; Cervera, S.; Macé, S.; Trassinelli, M.; Steydli, S.; Vernhet, D.

    2016-08-01

    The effects of 90 keV neon beam irradiation on the structure and magnetic properties of zinc ferrite thin films have been investigated through several methods, namely, X-ray diffraction technique, Vibrating Sample and SQUID magnetometers. Beforehand, the pristine have also been characterized using profilometry and microscopy techniques. In particular single-phase formation of the thin films deposited on monocrystalline Si (111) substrate by pulsed laser deposition technique was confirmed. Crystal lattice, coercivity, saturation magnetization have been studied for the first time, as a function of ion penetration depth and irradiation fluence. The chemical composition and the crystallinity of the films are not affected with the ion impact acting as a mechanical stress relief. On the contrary, both magnetization and coercivity are sensitive to Neq+ ion irradiation and exhibit different behaviours depending on the ion fluence range.

  9. Thickness-dependent optical properties in compressively strained BiFeO{sub 3}/LaAlO{sub 3} films grown by pulsed laser deposition

    SciTech Connect

    Duan, Zhihua; Jiang, Kai; Wu, Jiada; Sun, Jian; Hu, Zhigao; Chu, Junhao

    2014-03-01

    Graphical abstract: - Highlights: • BFO with various thicknesses was grown on LAO substrates by pulsed laser deposition. • The structure and compressive strains were clarified via Raman scattering. • The charge transfer excitation was blue shifted with increasing compressive strain. • The compressive strain affects the distortion of Fe{sup 3+} local environment and O 2p states. - Abstract: Bismuth ferrite (BiFeO{sub 3}) films with various thicknesses were epitaxially grown on LaAlO{sub 3} substrates by pulsed laser deposition. The X-ray diffraction and Raman scattering spectra reveal that the films were highly (11{sup ¯}1) oriented with the single phase. With increasing the thickness, the compressive strain decreases and the strain ratios between the film and bulk crystal are evaluated to be 1.75, 1.57, and 1. Moreover, the compressive strain induces band gap shrinkage from 2.7 to 2.65 eV, while the charge transfer transition energy increases from 3.5 to 4.1 eV. It could be due to the shift of O 2p states and the variation of local Fe{sup 3+} crystal field.

  10. Electrochromic behavior in CVD grown tungsten oxide films

    NASA Astrophysics Data System (ADS)

    Gogova, D.; Iossifova, A.; Ivanova, T.; Dimitrova, Zl; Gesheva, K.

    1999-03-01

    Solid state electrochemical devices (ECDs) for smart windows, large area displays and automobile rearview mirrors are of considerable technological and commercial interest. In this paper, we studied the electrochromic properties of amorphous and polycrystalline CVD carbonyl tungsten oxide films and the possibility for sol-gel thin TiO 2 film to play the role of passive electrode in an electrochromic window with solid polymer electrolyte.

  11. Influence of oxygen annealing conditions on the electronic structure, dielectric function, and charge conduction of gallium-ferrite thin films

    NASA Astrophysics Data System (ADS)

    Shin, Ran Hee; Oh, Seol Hee; Lee, Ji Hye; Jo, William; Jang, Seunghun; Han, Moonsup; Choi, Sukgeun

    2013-12-01

    Gallium-ferrite thin films were studied to investigate the effects of the oxygen annealing conditions on the electrical properties. Ga0.8Fe1.2O3- δ thin films were prepared by using a sol-gel method under different oxygen partial pressures. The structural properties of the films were studied by using X-ray diffraction. X-ray photoemission spectra of the core-levels of Ga, Fe, and O in the films were examined. The dielectric functions of the films were measured at energies from 0.73 to 6.45 eV by using spectroscopic ellipsometry. The Fe valence was changed by the oxygen vacancies, which are dominantly responsible for the dielectric function and the charge conduction. Remarkably, the leakage current of the films annealed under intermediate oxygen atmospheric conditions showed the lowest values. In the film, the oxygen vacancies, were indirectly estimated by using the ratio of Fe2+ to Fe3+, are important to reduce the leakage current, which can be explained by using a space-charge-limited model with shallow traps.

  12. Some studies on successive ionic layer adsorption and reaction (SILAR) grown indium sulphide thin films

    SciTech Connect

    Pathan, H.M.; Lokhande, C.D. . E-mail: l_chandrakant@yahoo.com; Kulkarni, S.S.; Amalnerkar, D.P.; Seth, T.; Han, Sung-Hwan . E-mail: shhan@hanyang.ac.kr

    2005-06-15

    Indium sulphide (In{sub 2}S{sub 3}) thin films were grown on amorphous glass substrate by the successive ionic layer adsorption and reaction (SILAR) method. X-ray diffraction, optical absorption, scanning electron microscopy (SEM) and Rutherford back scattering (RBS) were applied to study the structural, optical, surface morphological and compositional properties of the indium sulphide thin films. Utilization of triethanolamine and hydrazine hydrate complexed indium sulphate and sodium sulphide as precursors resulted in nanocrystalline In{sub 2}S{sub 3} thin film. The optical band gap was found to be 2.7 eV. The film appeared to be smooth and homogeneous from SEM study.

  13. Zinc oxide films chemically grown onto rigid and flexible substrates for TFT applications

    NASA Astrophysics Data System (ADS)

    Suchea, M.; Kornilios, N.; Koudoumas, E.

    2010-10-01

    This contribution presents some preliminary results regarding the use of a chemical route for the growth of good quality ZnO thin films that can be used for the fabrication of thin film transistors (TFTs). The films were grown at rather low temperature (60 °C) on glass and PET substrates using non-aqueous (zinc acetate dihydrate in methanol) precursor solution and their surface morphology, crystalline structure, optical transmittance and electrical characteristics were studied. The study indicated that good quality films with desirable ZnO structure onto rigid and flexible substrates can be obtained, using a simple, cheap, low temperature chemical growth method.

  14. Microhardness studies on thin carbon films grown on P-type, (100) silicon

    NASA Technical Reports Server (NTRS)

    Kolecki, J. C.

    1982-01-01

    A program to grow thin carbon films and investigate their physical and electrical properties is described. Characteristics of films grown by rf sputtering and vacuum arc deposition on p type, (100) silicon wafers are presented. Microhardness data were obtained from both the films and the silicon via the Vickers diamond indentation technique. These data show that the films are always harder than the silicon, even when the films are thin (of the order of 1000 A). Vacuum arc films were found to contain black carbon inclusions of the order of a few microns in size, and clusters of inclusions of the order of tens of microns. Transmission electron diffraction showed that the films being studied were amorphous in structure.

  15. Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

    SciTech Connect

    Craciun, D.; Socol, G.; Lambers, E.; McCumiskey, E. J.; Taylor, C. R.; Martin, C.; Argibay, Nicolas; Craciun, V.; Tanner, D. B.

    2015-01-17

    Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH4 pressures exhibited slightly higher nanohardness and Young modulus values than films deposited under higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.

  16. Optical and mechanical properties of nanocrystalline ZrC thin films grown by pulsed laser deposition.

    DOE PAGESBeta

    Craciun, D.; Socol, G.; Lambers, E.; McCumiskey, E. J.; Taylor, C. R.; Martin, C.; Argibay, Nicolas; Craciun, V.; Tanner, D. B.

    2015-01-17

    Thin ZrC films (<500 nm) were grown on (100) Si substrates at a substrate temperature of 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under different CH4 pressures. Glancing incidence X-ray diffraction showed that films were nanocrystalline, while X-ray reflectivity studies found out films were very dense and exhibited a smooth surface morphology. Optical spectroscopy data shows that the films have high reflectivity (>90%) in the infrared region, characteristic of metallic behavior. Nanoindentation results indicated that films deposited under lower CH4 pressures exhibited slightly higher nanohardness and Young modulus values than films deposited undermore » higher pressures. As a result, tribological characterization revealed that these films exhibited relatively high wear resistance and steady-state friction coefficients on the order of μ = 0.4.« less

  17. Exchange Bias and Unusual Initial Magnetization in Nanocrystalline Spinel Ferrite Thin Films

    NASA Astrophysics Data System (ADS)

    Alaan, Urusa; Gollapudi, Sreenivasulu; Yu, Kin Man; Shafer, Padraic; Arenholz, Elke; Srinivasan, Gopalan; Suzuki, Yuri

    2015-03-01

    We report on unconventional magnetic behavior in nanocrystalline (Mn,Zn,Fe)3O4 (MZFO) thin films grown at room temperature. Structural studies show no secondary phases, yet these films are exchange biased, with magnetic hysteresis loops shifted by as much as ~ 200 Oe at 10 K after field-cooling. The samples can be ``trained'' so that successive magnetization loops exhibit reduced exchange bias. Shifts of the hysteresis loops exist even after cooling in zero field, indicating that the MZFO is not externally biased. We attribute the exchange bias to disordered, grain-boundary-like regions that bias more ordered MZFO. Annealing experiments that improved sample crystallinity decreased the exchange bias. Higher annealing temperatures resulted in reduced coercivities, higher magnetizations, and even the elimination of the exchange bias. Annealing also removed an unusual crossover of the initial magnetization curve outside of the saturated magnetization loop. This behavior has been seen in so-called ``mictomagnetic'' alloys. Using x-ray magnetic circular dichroism measurements, we have shown that cation disorder was reduced with annealing, and correlated the atypical initial magnetization with the degree of disorder. We gratefully acknowledge the National Science Foundation for funding this research.

  18. Pyroelectric and piezoelectric responses of thin AlN films epitaxy-grown on a SiC/Si substrate

    NASA Astrophysics Data System (ADS)

    Kukushkin, S. A.; Osipov, A. V.; Sergeeva, O. N.; Kiselev, D. A.; Bogomolov, A. A.; Solnyshkin, A. V.; Kaptelov, E. Yu.; Senkevich, S. V.; Pronin, I. P.

    2016-05-01

    This paper presents the results of pyroelectric and piezoelectric studies of AlN films formed by chloride-hydride epitaxy (CHE) and molecular beam epitaxy (MBE) on epitaxial SiC nanolayers grown on Si by the atom substitution method. The surface topography and piezoelectric and pyroelecrtric responses of AlN films have been analyzed. The results of the study have shown that the vertical component of the piezoresponse in CHE-grown AlN films is more homogeneous over the film area than that in MBE-grown AlN films. However, the signal from the MBE-synthesized AlN films proved to be stronger. The inversion of the polar axis (polarization vector) on passage from MBE-grown AlN films to CHE-grown AlN films has been found experimentally. It has been shown that the polar axis in MBE-grown films is directed from the free surface of the film toward the Si substrate while, in CHE-grown films, the polarization vector is directed toward the free surface.

  19. Friction and wear performance of diamondlike carbon films grown in various source gas plasmas

    SciTech Connect

    Erdemir, A.; Nilufer, I. B.; Eryilmaz, O. L.; Beschliesser, M.; Fenske, G. R.

    2000-01-18

    In this study, the authors investigated the effects of various source gases (methane, ethane, ethylene, and acetylene) on the friction and wear performance of diamondlike carbon (DLC) films prepared in a plasma enhanced chemical vapor deposition (PECVD) system. Films were deposited on AISI H13 steel substrates and tested in a pin-on-disk machine against DLC-coated M50 balls in dry nitrogen. They found a close correlation between friction coefficient and source gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios exhibited lower friction coefficients and higher wear resistance than films grown in source gases with lower hydrogen-to-carbon (H/C) ratios. The lowest friction coefficient (0.014) was achieved with a film derived from methane with an WC ratio of 4, whereas the coefficient of films derived from acetylene (H/C = 1) was of 0.15. Similar correlations were observed for wear rates. Specifically, films derived from gases with lower H/C values were worn out and the substrate material was exposed, whereas films from methane and ethane remained intact and wore at rates that were nearly two orders of magnitude lower than films obtained from acetylene.

  20. Enhanced ionic conduction at the film/substrate interface in LiI thin films grown on sapphire(0001)

    SciTech Connect

    Lubben, D.; Modine, F.A.

    1993-12-01

    The ionic conductivity of LiI thin films grown on sapphire(0001) substrates has been studied in-situ during deposition as a function of film thickness and deposition conditions. LiI films were produced at room temperature by sublimation in an ultra-high-vacuum system. The conductivity of the LiI parallel to the film/substrate interface was determined from frequency-dependent impedance measurements as a function of film thickness using Au interdigital electrodes deposited on the sapphire surface. The measurements show a conduction of {approximately}5 times the bulk value at the interface which gradually decreases as the film thickness is increased beyond 100 nm. This interfacial enhancement is not stable but anneals out with a characteristic log of time dependence. Fully annealed films have an activation energy for conduction ({sigma}T) of {approximately}0.47{plus_minus}.03 eV, consistent with bulk measurements. The observed annealing behavior can be fit with a model based on dislocation motion which implies that the increase in conduction near the interface is not due to the formation of a space-charge layer as previously reported but to defects generated during the growth process. This explanation is consistent with the behavior exhibited by CaF{sub 2} films grown under similar conditions.

  1. Improved morphology in electrochemically grown conducting polymer films

    SciTech Connect

    Rubinstein, I.; Gottesfeld, S.; Sabatani, E.

    1990-12-31

    A conducting polymer film with an improved space filling is formed on a metal electrode surface. A self-assembling monolayer is formed directly on the metal surface where the monolayer has a first functional group that binds to the metal surface and a second chemical group that forms a chemical bonding site for molecules forming the conducting polymer. The conducting polymer is then conventionally deposited by electrochemical deposition. In one example, a conducting film of polyaniline is formed on a gold electrode surface with an intermediate monolayer of p-aminothiophenol.

  2. Effects of Seed Layer on YBa2Cu3Ox Films Grown by Liquid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Zama, Hideaki; Miyakoshi, Masayuki; Yamamoto, Hiroshi; Morishita, Tadataka

    1999-11-01

    Crack-free YBa2Cu3Ox (YBCO) films were grown by liquid phaseepitaxy (LPE) on MgO(100) substrates with a YBCO seed layer. Thecrystalline property of LPE was crucially dependent on that of theseed layer. On the purely c-axis-oriented seed layer, reasonable YBCOfilms were grown with a full-width at half maximum of the (005)reflection rocking curve, Δω, of 0.07°. In the case of the seedincluding an a-axis-oriented grain, the value of Δω of LPE films waspoor in reproducibility and larger than 0.1° on average. For thea-axis-oriented seed, no YBCO films grew under the growth conditionsin this study. X-ray topographic observations revealed that thecrystalline quality of MgO substrates limited the Δω of LPE films grownon them.

  3. Unintentional Doping Mechanisms in GaAs/Si Films Grown by Metalorganic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Deng, Can; Jia, Zhi-Gang; Wang, Yi-Fan; Wang, Qi; Huang, Yong-Qing; Ren, Xiao-Min

    2013-11-01

    To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.

  4. Electron field emission from phase pure nanotube films grown in a methane/hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Küttel, Olivier M.; Groening, Oliver; Emmenegger, Christoph; Schlapbach, Louis

    1998-10-01

    Phase pure nanotube films were grown on silicon substrates by a microwave plasma under conditions which normally are used for the growth of chemical vapor deposited diamond films. However, instead of using any pretreatment leading to diamond nucleation we deposited metal clusters on the silicon substrate. The resulting films contain only nanotubes and also onion-like structures. However, no other carbon allotropes like graphite or amorphous clustered material could be found. The nanotubes adhere very well to the substrates and do not need any further purification step. Electron field emission was observed at fields above 1.5 V/μm and we observed an emission site density up to 104/cm2 at 3 V/μm. Alternatively, we have grown nanotube films by the hot filament technique, which allows to uniformly cover a two inch wafer.

  5. Epitaxial Structure of (001)- and (111)-Oriented Perovskite Ferrate Films Grown by Pulsed-Laser Deposition.

    PubMed

    Chakraverty, Suvankar; Ohtomo, Akira; Okude, Masaki; Ueno, Kazunori; Kawasaki, Masashi

    2010-04-01

    The epitaxial structures of SrFeO(2.5) films grown on SrTiO(3) (001) and (111) substrates by PLD are reported. A layer-by-layer growth mode was achieved in the initial stage on both substrates. The films were stabilized with a monoclinic structure, where we identified the in-plane domain structures and orientation relationship. Our study presents a guide to control the heteroepitaxy of (111)-oriented noncubic perovskites. PMID:20383295

  6. Growth and properties of amorphous silicon films grown using pulsed-flow reactive plasma beam epitaxy

    NASA Technical Reports Server (NTRS)

    Dalal, Vikram L.; Knox, Ralph; Kandalaft, Nabeeh; Baldwin, Greg

    1991-01-01

    The growth and properties of a-Si:H films grown using a novel deposition technique, reactive plasma beam epitaxy, are discussed. In this technique, a remote H plasma produced in a microwave-ECR reactor is used to grow a-Si:H films at low pressures. The H ions react with SiH4 introduced near the substrate to produce the film. The flow of SiH4 is pulsed on or off, thereby achieving in-situ annealing of the film during growth by H ions and radicals. The films produced by this technique appear to have good electronic quality, and are more stable than the standard glow discharge films.

  7. Hydroxyapatite thin films grown by pulsed laser deposition and radio-frequency magnetron sputtering: comparative study

    NASA Astrophysics Data System (ADS)

    Nelea, V.; Morosanu, C.; Iliescu, M.; Mihailescu, I. N.

    2004-04-01

    Hydroxyapatite (HA) thin films for applications in the biomedical field were grown by pulsed laser deposition (PLD) and radio-frequency magnetron sputtering (RF-MS) techniques. The depositions were performed from pure hydroxyapatite targets on Ti-5Al-2.5Fe (TiAlFe) alloys substrates. In order to prevent the HA film penetration by Ti atoms or ions diffused from the Ti-based alloy during and after deposition, the substrates were pre-coated with a thin buffer layer of TiN. In both cases, TiN was introduced by reactive PLD from TiN targets in low-pressure N 2. The PLD films were grown in vacuum onto room temperature substrates. The RF-MS films were deposited in low-pressure argon on substrates heated at 550 °C. The initially amorphous PLD thin films were annealed at 550 °C for 1 h in ambient air in order to restore the initial crystalline structure of HA target. The thickness of the PLD and RF-MS films were ˜1 μm and ˜350 nm, respectively. All films were structurally studied by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray spectrometry (EDS) and white light confocal microscopy (WLCM). The mechanical properties of the films were tested by Berkovich nano-indentation. Both PLD and RF-MS films mostly contain HA phase and exhibit good mechanical characteristics. Peaks of CaO were noticed as secondary phase in the GIXRD patterns only for RF-MS films. By its turn, the sputtered films were smoother as compared to the ones deposited by PLD (50 nm versus 250 nm average roughness). The RF-MS films were harder, more mechanically resistant and have a higher Young modulus.

  8. Tungsten oxide nanowires grown on amorphous-like tungsten films.

    PubMed

    Dellasega, D; Pietralunga, S M; Pezzoli, A; Russo, V; Nasi, L; Conti, C; Vahid, M J; Tagliaferri, A; Passoni, M

    2015-09-11

    Tungsten oxide nanowires have been synthesized by vacuum annealing in the range 500-710 °C from amorphous-like tungsten films, deposited on a Si(100) substrate by pulsed laser deposition (PLD) in the presence of a He background pressure. The oxygen required for the nanowires formation is already adsorbed in the W matrix before annealing, its amount depending on deposition parameters. Nanowire crystalline phase and stoichiometry depend on annealing temperature, ranging from W18O49-Magneli phase to monoclinic WO3. Sufficiently long annealing induces the formation of micrometer-long nanowires, up to 3.6 μm with an aspect ratio up to 90. Oxide nanowire growth appears to be triggered by the crystallization of the underlying amorphous W film, promoting their synthesis at low temperatures. PMID:26292084

  9. Effect of Ge on SiC film morphology in SiC/Si films grown by MOCVD

    SciTech Connect

    Sarney, W.L.; Salamanca-Riba, L.; Zhou, P.; Spencer, M.G.; Taylor, C.; Sharma, R.P.; Jones, K.A.

    1999-07-01

    SiC/Si films generally contain stacking faults and amorphous regions near the interface. High quality SiC/Si films are especially difficult to obtain since the temperatures usually required to grow high quality SiC are above the Si melting point. The authors added Ge in the form of GeH{sub 2} to the reactant gases to promote two-dimensional CVD growth of SiC films on (111) Si substrates at 1,000 C. The films grown with no Ge are essentially amorphous with very small crystalline regions, whereas those films grown with GeH{sub 2} flow rates of 10 and 15 sccm are polycrystalline with the 3C structure. Increasing the flow rate to 20 sccm improves the crystallinity and induces growth of 6H SiC over an initial 3C layer. This study presents the first observation of spontaneous polytype transformation in SiC grown on Si by MOCVD.

  10. Epitaxially grown strained pentacene thin film on graphene membrane.

    PubMed

    Kim, Kwanpyo; Santos, Elton J G; Lee, Tae Hoon; Nishi, Yoshio; Bao, Zhenan

    2015-05-01

    Organic-graphene system has emerged as a new platform for various applications such as flexible organic photovoltaics and organic light emitting diodes. Due to its important implication in charge transport, the study and reliable control of molecular packing structures at the graphene-molecule interface are of great importance for successful incorporation of graphene in related organic devices. Here, an ideal membrane of suspended graphene as a molecular assembly template is utilized to investigate thin-film epitaxial behaviors. Using transmission electron microscopy, two distinct molecular packing structures of pentacene on graphene are found. One observed packing structure is similar to the well-known bulk-phase, which adapts a face-on molecular orientation on graphene substrate. On the other hand, a rare polymorph of pentacene crystal, which shows significant strain along the c-axis, is identified. In particular, the strained film exhibits a specific molecular orientation and a strong azimuthal correlation with underlying graphene. Through ab initio electronic structure calculations, including van der Waals interactions, the unusual polymorph is attributed to the strong graphene-pentacene interaction. The observed strained organic film growth on graphene demonstrates the possibility to tune molecular packing via graphene-molecule interactions. PMID:25565340

  11. Study of critical current density in superconducting magnesium diboride films grown by ex situ annealing of CVD boron films

    NASA Astrophysics Data System (ADS)

    Hanna, Mina

    MgB2 films have been processed by different techniques, the most successful of which include the hybrid physical-chemical vapor deposition (HPCVD) as well as the ex situ high temperature annealing of boron films in Mg vapor. The advantage of the ex situ method is that it allows the coating of MgB2 on large and complex surfaces, such as superconducting radio frequency (RF) cavities. However, it has always been realized that HPCVD films can carry higher J c than the ex situ annealed films. In this research, we succeeded in fabricating high quality MgB2 films by the ex situ annealing technique that produced a Jc value as high as 1.8 x 106 A/cm 2 for 1 mum thick film at 20 K and self-field. This high Jc value is, however, considerably reduced at higher thicknesses similar to that observed in YBCO coated conductors. In order to understand the mechanisms responsible for J c decrease with increasing film thickness, we studied the Jc behavior as a function of thickness in MgB2 films fabricated by ex situ annealing at 840°C of boron films, grown by chemical vapor deposition, in Mg vapor. The film thickness ranged between 300 nm and 10 mum. The values of Jc for these films ranged from 1.2 x 107 A/cm2 for 300 nm to 1.9 x 105 A/cm2 for 10 mum film thickness at 20 K and self-field. In addition, the results show that critical current (Ic) reaches a maximum value of 728 A/cm width at ˜1 mum thick MgB2 film at 20 K and self-field. These results of Jc and Ic behaviors with higher thickness are interpreted in terms of impurity diffusion during annealing and microstructural degradation for thicker films.

  12. Magnetic properties of hexagonal barium ferrite films on Pt/MgO(111) substrates annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Han, Mangui; Zheng, Liang; Deng, Jiangxia; Zheng, Peng; Wu, Qiong; Deng, Longjiang; Qin, Huibin

    2016-09-01

    In this work, hexagonal barium ferrite thin films have been deposited on Pt/MgO(111) substrates by pulsed laser deposition. The anneal temperature dependence of crystal structures, extents of diffusion and magnetic properties have been studied. X-ray diffraction patterns reveal that the crystal structure changes from the hexagonal to the spinel when the anneal temperature increases. The texture with c-axis perpendicular to the film plane and the small c-axis dispersion angles (△ɵc) have been obtained in the film annealed at 950 °C for 10 h. Both the X-ray photoelectron spectroscopy profiles and energy dispersive spectrometer show that the diffusions of Mg2+and Fe3+cations are more obvious when the annealing temperature is higher than 950 °C. The film annealed at 950 °C show anisotropic and hard magnetic properties. The magnetic properties of film annealed at 1050 °C are soft. In order to study the cation diffusions between thin film and substrate, the concentration profiles of cations (Ba2+, Fe3+, Mg2+) have been measured by XPS for a thin film with a thickness of 130 nm annealed at 950°C and 1050°C, as shown in Fig. 3. When Ta is 950°C, as shown in Fig. 3(a), diffusions between the film and the substrate are scarcely detected. However, obvious inter-diffusions have been found for Mg2+ cation and Fe3+ cation when it is annealed at 1050°C. An obvious diffusion has not been found for Ba2+ cation at both annealing temperatures.

  13. The influence of Cd doping on the microstructure and optical properties of nanocrystalline copper ferrite thin films

    SciTech Connect

    El-Hagary, M.; Matar, A.; Shaaban, E.R.; Emam-Ismail, M.

    2013-06-01

    Highlights: ► The structural and optical properties of Cu{sub 1−x}Cd{sub x}Fe{sub 2}O{sub 4} thin films were studied. ► The micro structural parameters of the films have been determined. ► The room temperature reflectance and transmittance data are analyzed. ► The refractive index and energy gap are determined. ► The single oscillator parameters were calculated. - Abstract: Nanocrystalline thin films of mixed Cu–Cd ferrites, Cu{sub 1−x}Cd{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.2, 0.3, 0.5, 0.7, 0.8, 0.9 and 1), were deposited by electron beam evaporation technique. The films were annealed at 450 °C for 1 h. The effect of Cd doping on the structural and optical properties of the deposited films has been investigated by using X-ray diffraction (XRD) and optical spectrophotometry. XRD patterns of the annealed films show spinal cubic structure. The lattice parameter was found to increase with the increase of cadmium concentration. The crystallite size of the films was found to vary from 8 nm to 30 nm. The optical transition was found to be direct and indirect transitions with energy gaps decrease from 2.466 (x = 0) to 2.00 (x = 1) eV and from 2.148 (x = 0) to 1.824 (x = 1) eV, respectively. The refractive index dispersion of the films was found to increase with Cd content and discussed in terms of the Wemple–DiDomenico single oscillator model.

  14. High quality CuInSe2 films grown on pseudo-lattice-matched substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Niki, S.; Fons, P. J.; Yamada, A.; Kurafuji, T.; Chichibu, S.; Nakanishi, H.; Bi, W. G.; Tu, C. W.

    1996-07-01

    CuInSe2 films have been grown by molecular beam epitaxy on pseudo-lattice-matched substrates that consist of a 1-μm-thick In0.29Ga0.71As layer grown on a linearly composition-graded InxGa1-xAs buffer (0≤x≤0.29) grown in turn on GaAs (001). The properties of these films have been compared with those of the films grown directly on GaAs (001). High resolution x-ray diffraction analysis on CuInSe2 grown on pseudo-lattice-matched substrates indicated substantial reduction on residual strain in the CuInSe2 films. A photoluminescence spectrum dominated by sharp free exciton emissions has been observed for the first time from CuInSe2 films indicative of significant improvement in crystalline quality and substantial reduction in the point defect density.

  15. Epitaxial growth of highly-crystalline spinel ferrite thin films on perovskite substrates for all-oxide devices.

    PubMed

    Moyer, Jarrett A; Gao, Ran; Schiffer, Peter; Martin, Lane W

    2015-01-01

    The potential growth modes for epitaxial growth of Fe3O4 on SrTiO3 (001) are investigated through control of the energetics of the pulsed-laser deposition growth process (via substrate temperature and laser fluence). We find that Fe3O4 grows epitaxially in three distinct growth modes: 2D-like, island, and 3D-to-2D, the last of which is characterized by films that begin growth in an island growth mode before progressing to a 2D growth mode. Films grown in the 2D-like and 3D-to-2D growth modes are atomically flat and partially strained, while films grown in the island growth mode are terminated in islands and fully relaxed. We find that the optimal structural, transport, and magnetic properties are obtained for films grown on the 2D-like/3D-to-2D growth regime boundary. The viability for including such thin films in perovskite-based all-oxide devices is demonstrated by growing a Fe3O4/La0.7Sr0.3MnO3 spin valve epitaxially on SrTiO3. PMID:26030835

  16. Epitaxial growth of highly-crystalline spinel ferrite thin films on perovskite substrates for all-oxide devices

    PubMed Central

    Moyer, Jarrett A.; Gao, Ran; Schiffer, Peter; Martin, Lane W.

    2015-01-01

    The potential growth modes for epitaxial growth of Fe3O4 on SrTiO3 (001) are investigated through control of the energetics of the pulsed-laser deposition growth process (via substrate temperature and laser fluence). We find that Fe3O4 grows epitaxially in three distinct growth modes: 2D-like, island, and 3D-to-2D, the last of which is characterized by films that begin growth in an island growth mode before progressing to a 2D growth mode. Films grown in the 2D-like and 3D-to-2D growth modes are atomically flat and partially strained, while films grown in the island growth mode are terminated in islands and fully relaxed. We find that the optimal structural, transport, and magnetic properties are obtained for films grown on the 2D-like/3D-to-2D growth regime boundary. The viability for including such thin films in perovskite-based all-oxide devices is demonstrated by growing a Fe3O4/La0.7Sr0.3MnO3 spin valve epitaxially on SrTiO3. PMID:26030835

  17. Properties of phosphorus-doped zinc oxide films grown by pulsed laser deposition

    SciTech Connect

    Li Yuanjie; Liu Zilong; Ren Jiangbo

    2011-05-15

    Electrical and chemical bonding properties of P-doped ZnO thin films grown by pulsed laser deposition on sapphire substrates were systematically characterized utilizing the Hall effect and x-ray photoelectron spectroscopy (XPS) measurements. Oxygen growth pressure and postannealing processing play a great role in the properties of these films. Increasing oxygen growth pressure from 5 to 20 Pa enhanced the resistivity of P-doped ZnO films by three orders of magnitude. P-doped ZnO films grown at 700 deg. C under 20 Pa O{sub 2} exhibited p-type conductivity with hole concentration of 5x10{sup 17} cm{sup -3} and hole mobility of 0.3 cm{sup 2}/V s. Rapid thermal annealing processing decreased the electron density in the P-doped ZnO films. XPS binding energies of P 2s and 2p peaks showed formation of P-O bonds which increased with oxygen pressure in the films. This indicates formation of defect complexes of P dopants occupying zinc sites P{sub Zn} and zinc vacancies V{sub Zn} in the P-doped ZnO films.

  18. Room Temperature Ferromagnetism in Transition Metal Doped CVD-Grown ZnO Films and Nanostructures

    NASA Astrophysics Data System (ADS)

    Hill, D. H.; Gateau, R.; Bartynski, R. A.; Wu, P.; Lu, Y.; Wielunski, L.; Poltavets, V.; Greenblatt, M.; Arena, D. A.; Dvorak, J.; Calvin, S.

    2006-03-01

    We have characterized the chemical, compositional, and magnetic properties of Mn- and Fe-ion implanted epitaxial ZnO films and single crystal nanostructures grown by MOCVD as candidate room temperature diluted magnetic semiconductors. X-ray absorption spectroscopy (SXAS) shows that Mn-implanted films contain Mn^2+ ions which convert to a mixture of Mn^3+ and Mn^4+ upon annealing. Fe-implanted films contain a mixture of Fe^2+ and Fe^3+ which converts to a higher concentration of Fe^3+ upon annealing. XAS and preliminary analysis of EXAFS data indicate that the TM ions are substitutional for Zn. SQUID magnetometry shows that as-implanted films are ferromagnetic at 5K and the annealed films are ferromagnetic at room temperature. X-ray diffraction shows that the annealed films remain epitaxial with excellent long range order. Rutherford backscattering spectrometry indicates a substantial recovery of local order upon annealing as well. The properties of in-situ Fe-doped MOCVD-grown ZnO epitaxial films and nanostructures will also be discussed.

  19. Static and dynamic magnetic property of MBE-grown Co2FeAl films

    NASA Astrophysics Data System (ADS)

    Qiao, Shuang; Nie, Shuaihua; Huo, Yan; Zhao, Jianhua; Wu, Yizheng; Zhang, Xinhui

    2014-08-01

    In this work, the static and dynamic magnetic properties of Co2FeAl films grown by molecular beam epitaxy (MBE) were studied by employing the magneto-optical Kerr rotation and ferromagnetic resonance (FMR) measurements. The growth temperature dependent magnetocrystalline anisotropy of MBE-grown Co2FeAl films were first investigated by employing the rotating magneto-optical Kerr effect. Then the magnetization dynamics and Gilbert damping property for high quality Co2FeAl films were investigated in detail by combining both the FMR and time-resolved magneto-optical Kerr rotation techniques. The apparent damping parameter was found to show strong dependence on the strength of the applied magnetic field at low-field regime, but decrease drastically with increasing magnetic field and eventually become a constant value of 0.004 at high-field regime. The inhomogeneity of magnetocrystalline anisotropy and two-magnon scattering are suggested to be responsible for the observed abnormal damping properties observed especially at low field regime. The intrinsic damping parameter of 0.004 is deduced for our highly-ordered Co2FeAl film. Our results provide essential information for highly-ordered MBE-grown Co2FeA film and its possible application in spintronic devices.

  20. Structural characterization of InSb thin films grown by electrodeposition

    SciTech Connect

    Singh, Joginder Rajaram, P.

    2015-06-24

    In the present work we have grown InSb thin films on brass substrates, using the electrodeposition technique. The electrochemical baths used in the growth were made up of aqueous solutions of InCl{sub 3} and SbCl{sub 3} mixed together in various proportions. The films grown were characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Analysis of X-rays (EDAX). Compositional studies show that stoichiometric InSb films can be prepared from a bath containing 0.05M InCl{sub 3} and 0.04M SbCl{sub 3}. XRD studies reveal that the films grown are polycrystalline having the zinc blende structure with (111) orientation. Crystallite size, dislocation density and strain were calculated using the XRD results. Optical transmission spectra were recorded using an FTIR spectrophotometer. The value of direct band gap was found to be around 0.20 eV for the thin films having the best stoichiometry.

  1. Cu(In,Ga)Se 2 thin-film solar cells grown with cracked selenium

    NASA Astrophysics Data System (ADS)

    Kawamura, Masahiro; Fujita, Toshiyuki; Yamada, Akira; Konagai, Makoto

    2009-01-01

    Cu(In 1-xGa x)Se 2 (CIGS) films have been grown by using cracked selenium. In conventional evaporation system, the Se atoms were supplied as large clusters (Se x, x>5). However, the size of clusters can be reduced by the thermal cracking. The film qualities grown with small clusters (Se x, x<4) would be improved, since the smaller size molecules easily react with elemental metals, resulting in the reduction of selenium vacancies and the enhancement of surface migration. The CIGS films were deposited by the three-stage method with cracked selenium, and the films were evaluated by SEM, XRD, EDX, C- V measurement and admittance spectroscopy. It was found from the C- V characteristics that the carrier concentrations of the CIGS films grown with cracked selenium were increased with increasing the cracking temperature. The result clearly showed that the use of cracked selenium was effective for reduction of selenium vacancies. The conversion efficiency of 15.4% was obtained by using cracked selenium at a cracking temperature of 500 °C.

  2. Red photoluminescence in praseodymium-doped titanate perovskite films epitaxially grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Takashima, Hiroshi; Ueda, Kazushige; Itoh, Mitsuru

    2006-12-01

    Intense red photoluminescence (PL) under ultraviolet (UV) excitation was observed in epitaxially grown Pr-doped Ca0.6Sr0.4TiO3 perovskite films. The films were grown on SrTiO3 (100) substrates by pulsed laser deposition, and their epitaxial growth was confirmed by x-ray diffraction and reflected high-energy electron diffraction. The observed sharp PL peak centered at 610nm was assigned to the transition of Pr3+ ions from the D21 state to the H43 state. The PL intensity was markedly enhanced by postannealing treatments at 1000°C, above the film-growth temperature of 600 or 800°C. Because the excitation and absorption spectra are similar to each other, it was suggested that the UV energy absorbed by the host lattice was transferred to the Pr ions, resulting in the red luminescence.

  3. Observation of three crystalline layers in hydrothermally grown BiFeO{sub 3} thick films

    SciTech Connect

    Lee, T. K.; Sung, K. D.; Jung, J. H.; Kim, T. H.; Ko, J.-H.

    2014-11-21

    We report the observation of three different crystalline layers in hydrothermally grown BiFeO{sub 3} (BFO) thick films on SrRuO{sub 3}/SrTiO{sub 3} substrates. High-resolution X-ray diffraction and transmission electron microcopy results suggest that compressively strained, partially relaxed epitaxial layers, and a mixture of polycrystalline and amorphous BFO layers, were successively formed from the bottom to the top of the films. The resistance and capacitance of the mixed layer were significantly lower than those of the epitaxial layers. The atomic concentrations of Bi and Fe in the mixed layer were fluctuating for each point. Based on the observed three crystalline layers, we have discussed the growth mechanism and the leakage current of hydrothermally grown BFO thick films.

  4. Friction and wear properties of smooth diamond films grown in fullerene-argon plasmas

    SciTech Connect

    Erdemir, A.; Fenske, G.R.; Bindal, C.; Zuiker, C.; Krauss, A.R.; Gruen, D.M.

    1995-08-01

    In this study, we describe the growth mechanism and the ultralow friction and wear properties of smooth (20-50 nm rms) diamond films grown in a microwave plasma consisting of Ar and fullerene (the carbon source). The sliding friction coefficients of these films against Si{sub 3}N{sub 4} balls are 0.04 and 0.1 in dry N{sub 2} and air, which are comparable to that of natural diamond sliding against the same pin material, but is lower by factors of 5 to 10 than that afforded by rough diamond films grown in conventional H{sub 2}-CH{sub 4} plasmas. Furthermore, the smooth diamond films produced in this work afforded wear rates to Si{sub 3}N{sub 4} balls that were two to three orders of magnitude lower than those of H{sub 2}-CH{sub 4} grown films. Mechanistically, the ultralow friction and wear properties of the fullerene-derived diamond films correlate well with their initially smooth surface finish and their ability to polish even further during sliding. The wear tracks reach an ultrasmooth (3-6 nm rms) surface finish that results in very little abrasion and ploughing. The nanocrystalline microstructure and exceptionally pure sp{sup 3} bonding in these smooth diamond films were verified by numerous surface and structure analytical methods, including x-ray diffraction, high-resolution AF-S, EELS, NEXAFS, SEM, and TEM. An AFM instrument was used to characterize the topography of the films and rubbing surfaces.

  5. Mechanically tunable magnetic properties of Fe81Ga19 films grown on flexible substrates

    NASA Astrophysics Data System (ADS)

    Dai, Guohong; Zhan, Qingfeng; Liu, Yiwei; Yang, Huali; Zhang, Xiaoshan; Chen, Bin; Li, Run-Wei

    2012-03-01

    We investigated on magnetic properties of magnetostrictive Fe81Ga19 films grown on flexible polyethylene terephthalate (PET) substrates under various mechanical strains. The unstrained Fe81Ga19 films exhibit a significant uniaxial magnetic anisotropy due to a residual stress in PET substrates. It was found that the squareness of hysteresis loops can be tuned by an application of strains, inward/compressive or outward/tensile bending of the films. A modified Stoner-Wohlfarth model with considering a distribution of easy axes in polycrystalline films was developed to account for the mechanically tunable magnetic properties in flexible Fe81Ga19 films. These results provide an alternative way to tune mechanically magnetic properties, which is particularly important for developing flexible magnetoelectronic devices.

  6. Amorphous indium gallium zinc oxide thin film grown by pulse laser deposition technique

    NASA Astrophysics Data System (ADS)

    Mistry, Bhaumik V.; Joshi, U. S.

    2016-05-01

    Highly electrically conducting and transparent in visible light IGZO thin film were grown on glass substrate at substrate temperature of 400 C by a pulse laser deposition techniques. Structural, surface, electrical, and optical properties of IGZO thin films were investigated at room temperature. Smooth surface morphology and amorphous nature of the film has been confirmed from the AFM and GIXRD analysis. A resistivity down to 7.7×10-3 V cm was reproducibly obtained while maintaining optical transmission exceeding 70% at wavelengths from 340 to 780 nm. The carrier densities of the film was obtain to the value 1.9×1018 cm3, while the Hall mobility of the IGZO thin film was 16 cm2 V-1S-1.

  7. As-grown superconducting Bi-Sr-Ca-Cu-O thin films by coevaporation

    SciTech Connect

    Satoh, T.; Yoshitake, T.; Miura, S.; Fujita, J.; Kubo, Y.; Igarashi, H.

    1989-08-14

    Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared on (100) MgO substrates at about 600 /degree/C by coevaporation. The /ital c/-axis lattice constant of this system was controlled to the values of 24--43 A by changing film composition. Superconducting transition temperatures of these films were affected by substrate temperature and by a post-deposition annealing at a low temperature. The highest zero resistance temperature (/ital T//sub /ital c/, zero/) of the as-grown Bi/sub 2/(Sr,Ca)/sub 3/Cu/sub 2/O/sub /ital x// film was 79 K. The best Bi/sub 2/(Sr, Ca)/sub 4/Cu/sub 3/O/sub /ital x// film showed an onset temperature of 105 K and /ital T//sub /ital c/, zero/ zero of 78 K after annealing at 400 /degree/C for 1 h.

  8. Intramolecular and Intermolecular Interactions in Hybrid Organic-Inorganic Alucone Films Grown by Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Kim, Hyein; Cho, Boram; Lee, Chaeyun; Choi, Sung-Eun; Sung, Myung Mo; Lee, Jin Seok

    2016-07-13

    Investigation of molecular interactions in polymeric films is crucial for understanding and engineering multiscale physical phenomena correlated to device function and performance, but this often involves a compromise between theoretical and experimental data, because of poor film uniformity. Here, we report the intramolecular and intermolecular interactions inside the ultrathin and conformal hybrid organic-inorganic alucone films grown by molecular layer deposition, based on sequential and self-limiting surface reactions. Varying the carbon chain length of organic precursors, which affects their molecular flexibility, caused intramolecular interactions such as double reactions by bending of the molecular backbone, resulting in formation of hole vacancies in the films. Furthermore, intermolecular interactions in alucone polymeric films are dependent on the thermal kinetics of molecules, leading to binding failures and cross-linking at low and high growth temperatures, respectively. We illustrate these key interactions and identify molecular geometries and potential energies by density functional theory calculations. PMID:27314844

  9. Optical Properties Of {beta}-FeSi2 Thin Films Grown By Magnetron Sputtering

    SciTech Connect

    Tatar, B.; Kutlu, K.

    2007-04-23

    {beta}-FeSi2 semiconductor thin films have been grown on Si(100) and Si(111) substrate at room temperature by unbalanced magnetron sputtering. The thicknesses of {beta}-FeSi2 thin films have been prepared to have value between 0.3-1{mu}m. Optical characteristic of the {beta}-FeSi2 films have been deduced using Fourier Transform Infrared Spectroscopy (FT-IR) in the wavelength range 1000-2000nm. The {beta}-FeSi2 films have been determinated to have optical direct band gap from the plot of ({alpha}h{upsilon})2 vs. h{upsilon} The direct band gap values of the films have been observed to vary between 0.82-0.89 eV depending on the type of substrates.

  10. Study of high [Tc] superconducting thin films grown by MOCVD

    SciTech Connect

    Erbil, A.

    1990-01-01

    Work is described briefly, which was carried out on development of techniques to grow metal-semiconductor superlattices (artificially layered materials) and on the copper oxide based susperconductors (naturally layered materials). The current growth technique utilized is metalorganic chemical vapor deposition (MOCVD). CdTe, PbTe, La, LaTe, and Bi[sub 2]Te[sub 3] were deposited, mostly on GaAs. Several YBa[sub 2]Cu[sub 3]O[sub 7] compounds were obtained with possible superconductivity at temperatures up to 550 K (1 part in 10[sup 4]). YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] and Tl[sub 2]CaBa[sub 2]Cu[sub 2]O[sub y] thin films were deposited by MOCVD on common substrates such as glass.

  11. Thin film transistors using PECVD-grown carbon nanotubes.

    PubMed

    Ono, Yuki; Kishimoto, Shigeru; Ohno, Yutaka; Mizutani, Takashi

    2010-05-21

    Thin film transistors with a carbon nanotube (CNT) network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I-V characteristics of CNT field effect transistors (CNT-FETs). Taking advantage of the preferential growth and suppression of bundle formation, a large ON current of 170 microA mm(-1), which is among the largest in these kinds of devices with a large ON/OFF current ratio of about 10(5), has been realized in the relatively short channel length of 10 microm. The field effect mobility of the device was 5.8 cm(2) V(-1) s(-1). PMID:20418603

  12. Thin film transistors using PECVD-grown carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ono, Yuki; Kishimoto, Shigeru; Ohno, Yutaka; Mizutani, Takashi

    2010-05-01

    Thin film transistors with a carbon nanotube (CNT) network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I-V characteristics of CNT field effect transistors (CNT-FETs). Taking advantage of the preferential growth and suppression of bundle formation, a large ON current of 170 µA mm - 1, which is among the largest in these kinds of devices with a large ON/OFF current ratio of about 105, has been realized in the relatively short channel length of 10 µm. The field effect mobility of the device was 5.8 cm2 V - 1 s - 1.

  13. Superconducting YBa 2Cu 3O 7- δ thin film grown on metallic film evaporated on MgO

    NASA Astrophysics Data System (ADS)

    Verdyan, A.; Azoulay, J.; Lapsker, I.

    2001-03-01

    At present it is commonly accepted that thin film formation of YBa 2Cu 3O 7- δ (YBCO) on conducting substrate is one of the keys to further development of advanced devices in the microelectronic and other applications. We have grown YBCO thin films by resistive evaporation technique on MgO coated with metallic layers (Ni or Ag). A simple inexpensive vacuum system equipped with resistively heated boats for metal and precursor mixture of yttrium, copper and barium fluoride powders was used. X-ray diffraction (XRD) and scanning electron microscopy techniques were used for texture, morphology and surface analyses respectively. Electrical and magnetical properties were determined by a standard dc four-probe method. The way of heating process is shown to be critical parameter in the film quality. The physical and electrical properties of the YBCO films are discussed in light of the fact that XRD measurements done on the metallic buffer layers have revealed a multicrystalline structure.

  14. Thin film solar cells grown by organic vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Yang, Fan

    Organic solar cells have the potential to provide low-cost photovoltaic devices as a clean and renewable energy resource. In this thesis, we focus on understanding the energy conversion process in organic solar cells, and improving the power conversion efficiencies via controlled growth of organic nanostructures. First, we explain the unique optical and electrical properties of organic materials used for photovoltaics, and the excitonic energy conversion process in donor-acceptor heterojunction solar cells that place several limiting factors of their power conversion efficiency. Then, strategies for improving exciton diffusion and carrier collection are analyzed using dynamical Monte Carlo models for several nanostructure morphologies. Organic vapor phase deposition is used for controlling materials crystallization and film morphology. We improve the exciton diffusion efficiency while maintaining good carrier conduction in a bulk heterojunction solar cell. Further efficiency improvement is obtained in a novel nanocrystalline network structure with a thick absorbing layer, leading to the demonstration of an organic solar cell with 4.6% efficiency. In addition, solar cells using simultaneously active heterojunctions with broad spectral response are presented. We also analyze the efficiency limits of single and multiple junction organic solar cells, and discuss the challenges facing their practical implementations.

  15. Magnetic and transport properties of epitaxial thin film MgFe2O4 grown on MgO (100) by molecular beam epitaxy

    PubMed Central

    Wu, Han-Chun; Mauit, Ozhet; Coileáin, Cormac Ó; Syrlybekov, Askar; Khalid, Abbas; Mouti, Anas; Abid, Mourad; Zhang, Hong-Zhou; Abid, Mohamed; Shvets, Igor V.

    2014-01-01

    Magnesium ferrite is a very important magnetic material due to its interesting magnetic and electrical properties and its chemical and thermal stability. Here we report on the magnetic and transport properties of epitaxial MgFe2O4 thin films grown on MgO (001) by molecular beam epitaxy. The structural properties and chemical composition of the MgFe2O4 films were characterized by X-Ray diffraction and X-Ray photoelectron spectroscopy, respectively. The nonsaturation of the magnetization in high magnetic fields observed for M (H) measurements and the linear negative magnetoresistance (MR) curves indicate the presence of anti-phase boundaries (APBs) in MgFe2O4. The presence of APBs was confirmed by transmission electron microscopy. Moreover, post annealing decreases the resistance and enhances the MR of the film, suggesting migration of the APBs. Our results may be valuable for the application of MgFe2O4 in spintronics. PMID:25388355

  16. Structure and Morphology of Phthalocyanine Films Grown in Electrical Fields by Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Banks, Curtis E.; Frazier, Donald O.; Penn, Benjamin; Abdeldayem, Hossin; Hicks, Roslin

    1999-01-01

    Phthalocyanine is a very stable organic material in the atmosphere and has been used in numerous applications, such as optical switching and optical storage devices. Although this material has already been discovered for several decades and has had extensive studies conducted on it, many properties still need to be better understood, for example, the mechanisms of forming different solid phases and of changing film morphology by external forces. Phthalocyanine has two preferred solid phases (alpha and beta phases) for which the crystal structures, surface morphology and optical properties are different. In order to investigate these phenomena and the relationship among them, phthalocyanine films have been synthesized by vapor deposition on quartz substrates with and without an external electrical field. Some substrates were coated with a very thin gold film for the electrical field. These films have been characterized using x-ray diffraction, scanning electron microscopy, Fourier transfer infrared spectroscopy, and Z-scan technique. The films have excellent chemical and thermal stability. However, the surface of these films grown without the electrical field shows flower-like morphology. When films are deposited under an electrical field (approximately 3000 V/cm), an aligned structure is revealed on the surface. A comparison of the structure, morphology, optical properties, and the growth mechanism for these films with and without an electrical field will be discussed.

  17. Structural, optical and electrochromic properties of nickel oxide thin films grown from electrodeposited nickel sulphide

    NASA Astrophysics Data System (ADS)

    Uplane, M. M.; Mujawar, S. H.; Inamdar, A. I.; Shinde, P. S.; Sonavane, A. C.; Patil, P. S.

    2007-10-01

    Nickel oxide thin films were grown onto FTO-coated glass substrates by a two-step process: electrodeposition of nickel sulphide and their thermal oxidation at 425, 475 and 525 °C. The influence of thermal oxidation temperature on structural, optical, morphological and electrochromic properties was studied. The structural properties undoubtedly revealed NiO formation. The electrochromic properties were studied by means of cyclic voltammetry. The films exhibited anodic electrochromism, changing from a transparent state to a coloured state at +0.75 V versus SCE, i.e. by simultaneous ion and electron ejection. The transmittance in the coloured and bleached states was recorded to access electrochromic quality of the films. Colouration efficiency and electrochromic reversibility were found to be maximum (21 mC/cm 2 and 89%, respectively) for the films oxidized at 425 °C. The optical band gap energy of nickel oxide slightly varies with increase in annealing temperature.

  18. Highly crystalline MoS{sub 2} thin films grown by pulsed laser deposition

    SciTech Connect

    Serrao, Claudy R.; You, Long; Gadgil, Sushant; Hu, Chenming; Salahuddin, Sayeef; Diamond, Anthony M.; Hsu, Shang-Lin; Clarkson, James; Carraro, Carlo; Maboudian, Roya

    2015-02-02

    Highly crystalline thin films of MoS{sub 2} were prepared over large area by pulsed laser deposition down to a single monolayer on Al{sub 2}O{sub 3} (0001), GaN (0001), and SiC-6H (0001) substrates. X-ray diffraction and selected area electron diffraction studies show that the films are quasi-epitaxial with good out-of-plane texture. In addition, the thin films were observed to be highly crystalline with rocking curve full width half maxima of 0.01°, smooth with a RMS roughness of 0.27 nm, and uniform in thickness based on Raman spectroscopy. From transport measurements, the as-grown films were found to be p-type.

  19. Free-standing thin film Ge single crystals grown by plasma-enhanced chemical vapor deposition

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    The films, which are approximately 10 microns in thickness, are grown epitaxially on polished (100) NaCl substrates at 450 C by plasma enhanced chemical vapor deposition. Upon cooling, the films are separated from the substrate by differential shear stress, leaving free-standing films of Ge which can be handled. Growths are attained by nucleating at minimum plasma power for very brief intervals and then raising the power to 65 W to increase the growth rate to approximately 10 microns/h. It is found that substrate exposure to the plasma at too high a power for too long a time sputters and erodes the surface, thereby substantially degrading the nucleation process and the ultimate growths. It is noted that the free-standing films are visually specular and exhibit a high degree of crystalline order when examined by X-ray diffraction. Auger electron spectroscopy and energy dispersive analysis of X-rays reveal no detectable bulk contamination.

  20. Diamond thin films grown by microwave plasma assisted chemical vapor deposition

    SciTech Connect

    Leksono, M.

    1991-09-05

    Undoped and boron doped diamond thin films have been successfully grown by microwave plasma chemical vapor deposition from CH{sub 4}, H{sub 2}, and B{sub 2}H{sub 6}. The films were characterized using x- ray diffraction techniques, Raman and infrared spectroscopies, scanning electron microscopy, secondary ion mass spectrometry, and various electrical measurements. The deposition rates of the diamond films were found to increase with the CH{sub 4} concentration, substrate temperature, and/or pressure, and at 1.0% methane, 900{degrees}C, and 35 Torr, the value was measured to be 0.87 {mu}m/hour. The deposition rate for boron doped diamond films, decreases as the diborane concentration increases. The morphologies of the undoped diamond films are strongly related to the deposition parameters. As the temperature increases from 840 to 925 C, the film morphology changes from cubo-octahedron to cubic structures, while as the CH{sub 4} concentration increases from 0.5 to 1.0%, the morphology changes from triangular (111) faces with a weak preferred orientation to square (100) faces. At 2.0% Ch{sub 4} or higher the films become microcrystalline with cauliflower structures. Scanning electron microscopy analyses also demonstrate that selective deposition of undoped diamond films has been successfully achieved using a lift-off process with a resolution of at least 2 {mu}m. The x-ray diffraction and Raman spectra demonstrate that high quality diamond films have been achieved. The concentration of the nondiamond phases in the films grown at 1.0% CH{sub 4} can be estimated from the Raman spectra to be at less than 0.2% and increases with the CH{sub 4} concentration. The Raman spectra of the boron doped diamond films also indicate that the presence of boron tends to suppress the nondiamond phases in the films. Infrared spectra of the undoped diamond films show very weak CH stretch peaks which suggest that the hydrogen concentration is very low.

  1. Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Afonso, André S; Faria, Ronaldo C; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2011-12-28

    The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film

  2. Group III-nitride thin films grown using MBE and bismuth

    DOEpatents

    Kisielowski, Christian K.; Rubin, Michael

    2002-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  3. Group III-nitride thin films grown using MBE and bismuth

    DOEpatents

    Kisielowski, Christian K.; Rubin, Michael

    2000-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  4. Solution-Grown Monocrystalline Hybrid Perovskite Films for Hole-Transporter-Free Solar Cells.

    PubMed

    Peng, Wei; Wang, Lingfei; Murali, Banavoth; Ho, Kang-Ting; Bera, Ashok; Cho, Namchul; Kang, Chen-Fang; Burlakov, Victor M; Pan, Jun; Sinatra, Lutfan; Ma, Chun; Xu, Wei; Shi, Dong; Alarousu, Erkki; Goriely, Alain; He, Jr-Hau; Mohammed, Omar F; Wu, Tom; Bakr, Osman M

    2016-05-01

    High-quality perovskite monocrystalline films are successfully grown through cavitation-triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3 NH3 PbBr3 /Au, with near 100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole-transporter-free structure yield PCEs ≈6.5%, the highest among other similar-structured CH3 NH3 PbBr3 solar cells to date. PMID:26931100

  5. One-dimensional edge state of Bi thin film grown on Si(111)

    SciTech Connect

    Kawakami, Naoya; Lin, Chun-Liang; Kawai, Maki; Takagi, Noriaki; Arafune, Ryuichi

    2015-07-20

    The geometric and electronic structures of the Bi thin film grown on Si(111) were investigated by using scanning tunneling microscopy and spectroscopy. We have found two types of edges, one of which hosts an electronic state localized one-dimensionally. We also revealed the energy dispersion of the localized edge state from the evolution of quasiparticle interference patterns as a function of energy. These spectroscopic findings well reproduce those acquired for the cleaved surface of the bulk Bi crystal [I. K. Drozdov et al., Nat. Phys. 10, 664 (2014)]. The present results indicate that the deposited Bi film provides a tractable stage for further scrutiny of the one-dimensional edge state.

  6. Residual stress in AlN films grown on sapphire substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Rong, Xin; Wang, Xinqiang; Chen, Guang; Pan, Jianhai; Wang, Ping; Liu, Huapeng; Xu, Fujun; Tan, Pingheng; Shen, Bo

    2016-05-01

    Residual stress in AlN films grown by molecular beam epitaxy (MBE) has been studied by Raman scattering spectroscopy. A strain-free Raman frequency and a biaxial stress coefficient for E2(high) mode are experimentally determined to be 657.8 ± 0.3 cm-1 and 2.4 ± 0.2 cm-1 / GPa, respectively. By using these parameters, the residual stress of a series of AlN layers grown under different buffer layer conditions has been investigated. The residual compressive stress is found to be obviously decreased by increasing the Al/N beam flux ratio of the buffer layer, indicating the generation of tensile stress due to stronger coalescence of AlN grains, as also confirmed by the in-situ reflection high energy electron diffraction (RHEED) monitoring observation. The stronger coalescence does lead to improved quality of AlN films as expected.

  7. Carrier dynamics in ZnxCd1-xO films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Cheng, F. J.; Lee, Y. C.; Hu, S. Y.; Lin, Y. C.; Tiong, K. K.; Chou, W. C.

    2016-05-01

    In this work, the carrier dynamics in Zn1-xCdxO thin films with different Cd contents grown by molecular beam epitaxy system have been investigated using photoluminescence and time-resolved photoluminescence measurements. The carrier lifetime can be estimated from the PL decay curve fitted by triple exponential function. The emission energy dependence and temperature dependence of the PL decay time indicate that carrier localization dominate the luminescence mechanism of the ZnCdO alloy semiconductor.

  8. Photoinduced Br Desorption from CsBr Thin Films Grown on Cu(100)

    SciTech Connect

    Halliday, Matthew T.; Joly, Alan G.; Hess, Wayne P.; Shluger, AL

    2015-10-22

    Thin films of CsBr deposited onto metals such as copper are potential photocathode materials for light sources and other applications. We investigate desorption dynamics of Br atoms from CsBr films grown on insulator (KBr, LiF) and metal (Cu) substrates induced by sub-bandgap 6.4 eV laser pulses. The experimental results demonstrate that the peak kinetic energy of Br atoms desorbed from CsBr/Cu films is much lower than that for the hyperthermal desorption from CsBr/LiF films. Kelvin probe measurements indicate negative charge at the surface following Br desorption from CsBr/Cu films. Our ab initio calculations of excitons at CsBr surfaces demonstrate that this behavior can be explained by an exciton model of desorption including electron trapping at the CsBr surface. Trapped negative charges reduce the energy of surface excitons available for Br desorption. We examine the electron-trapping characteristics of low-coordinated sites at the surface, in particular, divacancies and kink sites. We also provide a model of cation desorption caused by Franck-Hertz excitation of F centers at the surface in the course of irradiation of CsBr/Cu films. These results provide new insights into the mechanisms of photoinduced structural evolution of alkali halide films on metal substrates and activation of metal photocathodes coated with CsBr.

  9. Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films grown by atomic layer deposition

    SciTech Connect

    Tamm, Aile Kozlova, Jekaterina; Aarik, Lauri; Aarik, Jaan; Kukli, Kaupo; Link, Joosep; Stern, Raivo

    2015-01-15

    Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films were grown by atomic layer deposition on silicon substrates. For depositing dysprosium and titanium oxides Dy(thd){sub 3}-O{sub 3} and TiCl{sub 4}-O{sub 3} were used as precursors combinations. Appropriate parameters for Dy(thd){sub 3}-O{sub 3} growth process were obtained by using a quartz crystal microbalance system. The Dy{sub 2}O{sub 3} films were deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The Dy/Ti ratio of Dy{sub 2}O{sub 3}-doped TiO{sub 2} films deposited on a planar silicon substrate ranged from 0.04 to 0.06. Magnetometry studies revealed that saturation of magnetization could not be observed in planar Dy{sub 2}O{sub 3} films, but it was observable in Dy{sub 2}O{sub 3} films on 3D substrates and in doped TiO{sub 2} films with a Dy/Ti atomic ratio of 0.06. The latter films exhibited saturation magnetization 10{sup −6} A cm{sup 2} and coercivity 11 kA/m at room temperature.

  10. Conducting (Si-doped) aluminum nitride epitaxial films grown by molecular beam epitaxy

    SciTech Connect

    Kim, J.G.; Moorthy, M.; Park, R.M.

    1999-07-01

    As a member of the III-V nitride semiconductor family, AlN, which has a direct energy-gap of 6.2eV, has received much attention as a promising material for many applications. However, despite the promising attributes of AlN for various semiconductor devices, research on AlN has been limited and n-type conducting AlN has not been reported. The objective of this research was to understand the factors impacting the conductivity of AlN and to control the conductivity of this material through intentional doping. Prior to the intentional doping study, growth of undoped AlN epilayers was investigated. Through careful selection of substrate preparation methods and growth parameters, relatively low-temperature molecular beam epitaxial growth of AlN films was established which resulted in insulating material. Intentional Si doping during epilayer growth was found to result in conducting films under specific growth conditions. Above a growth temperature of 900 C, AlN films were insulating, however, below a growth temperature of 900 C, the AlN films were conducting. The magnitude of the conductivity and the growth temperature range over which conducting AlN films could be grown were strongly influenced by the presence of a Ga flux during growth. For instance, conducting, Si-doped, AlN films were grown at a growth temperature of 940 C in the presence of a Ga flux while the films were insulating when grown in the absence of a Ga flux at this particular growth temperature. Also, by appropriate selection of the growth parameters, epilayers with n-type conductivity values as large as 0.2 {Omega}{sup {minus}1} cm{sup {minus}1} for AlN and 17 {Omega}{sup {minus}1} cm{sup {minus}1} for Al{sub 0.75}Ga{sub 0.25}N were grown in this work for the first time.

  11. Elastic properties of B-C-N films grown by N{sub 2}-reactive sputtering from boron carbide targets

    SciTech Connect

    Salas, E.; Jiménez Riobóo, R. J.; Jiménez-Villacorta, F.; Prieto, C.; Sánchez-Marcos, J.; Muñoz-Martín, A.; Prieto, J. E.; Joco, V.

    2013-12-07

    Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B{sub 4}C target and N{sub 2} as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions.

  12. Magnetic and electromagnetic properties of Pr doped strontium ferrite/polyaniline composite film

    NASA Astrophysics Data System (ADS)

    Huang, Ying; Li, Yuqing; Wang, Yan

    2014-11-01

    This paper reported three acid (including hydrochloric acid HCl, p-toluenesulfonic acid PTS and D-camphor-10-acid CSA) doped SrPr0.2Fe11.8O19/PANI composite film and the HCl-PANI film prepared by a sol-gel method and in-situ oxidative polymerization. The characteristics of the film phase structure, surface morphology, conductivity and magnetic and electromagnetic properties were studied by using XRD, XPS, FESEM, four-probe tester, VSM and Vector Network Analyzer. The resistivity of organic acid doped composite films is higher than that of the HCl doped one. The saturation and remanent magnetization of PTS and HCl doped composite films are greater than the CSA-doped one; however, the coercivity of the three acid doped composite films is basically 5546 Oe. The saturation magnetization, remanent magnetization and coercivity of SrPr0.2Fe11.8O19 film are greater than those of the SrPr0.2Fe11.8O19-PANI composite film. In the frequency range of 8-12 GHz, the dielectric loss of HCl-PANI film is the maximum, and the dielectric loss of SrPr0.2Fe11.8O19 film is the minimum; the magnetic loss of the four films is in descending order as SrPr0.2Fe11.8O19 film, PrSrM/(HCl-PANI) composite film, PrSrM/(CSA-PANI) and HCl-PANI film.

  13. Photoluminescence, electrical and structural properties of ZnO films, grown by ALD at low temperature

    NASA Astrophysics Data System (ADS)

    Przeździecka, E.; Wachnicki, Ł.; Paszkowicz, W.; Łusakowska, E.; Krajewski, T.; Łuka, G.; Guziewicz, E.; Godlewski, M.

    2009-10-01

    We report the first results of the low-temperature photoluminescence study on polycrystal zinc oxide (ZnO) films obtained by atomic layer deposition at 100 °C, 130 °C and 200 °C. These ZnO films, when studied 'as-grown', show a strong excitonic emission even at room temperature. Low-temperature (T = 9 K) photoluminescence reveals lack of defect-related bands and a sharp photoluminescence peak at 3.36 eV with full width at half maximum of 6 meV which is comparable with the value reported for good quality bulk ZnO crystals. The energy position of the excitonic peak scales with temperature according to standard formulas and give the Debye temperature of 963 ± 26 K. We show that optical properties of low-temperature 'as-grown' ZnO films are correlated with structural and electrical ones and that optical study can be a valuable tool for evaluation of quality of ZnO films for novel electronic applications.

  14. Adsorption properties of Mg-Al layered double hydroxides thin films grown by laser based techniques

    NASA Astrophysics Data System (ADS)

    Matei, A.; Birjega, R.; Vlad, A.; Filipescu, M.; Nedelcea, A.; Luculescu, C.; Zavoianu, R.; Pavel, O. D.; Dinescu, M.

    2012-09-01

    Powdered layered double hydroxides (LDHs) have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic and/or organic molecules. Assembling nano-sized LDHs onto flat solid substrates forming thin films is an expanding area of research due to the prospects of novel applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices. Continuous and adherent thin films were grown by laser techniques (pulsed laser deposition - PLD and matrix assisted pulsed laser evaporation - MAPLE) starting from targets of Mg-Al LDHs. The capacity of the grown thin films to retain a metal (Ni) from contaminated water has been also explored. The thin films were immersed in an Ni(NO3)2 aqueous solutions with Ni concentrations of 10-3% (w/w) (1 g/L) and 10-4% (w/w) (0.1 g/L), respectively. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) were the techniques used to characterize the prepared materials.

  15. Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

    SciTech Connect

    Niizeki, Tomohiko; Kikkawa, Takashi; Uchida, Ken-ichi; Oka, Mineto; Suzuki, Kazuya Z.; Yanagihara, Hideto; Kita, Eiji; Saitoh, Eiji

    2015-05-15

    The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H) dependence of the LSSE voltage (V{sub LSSE}) in the Pt/CFO(110) sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H∥[11{sup -}0] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of V{sub LSSE} has a linear relationship with the temperature difference (ΔT), giving the relatively large V{sub LSSE} /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.

  16. Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

    NASA Astrophysics Data System (ADS)

    György, E.; Pérez del Pino, A.; Sauthier, G.; Figueras, A.

    2009-12-01

    Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ =248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well as target preparation procedure.

  17. Raman spectroscopy of ZnMnO thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Orozco, S.; Riascos, H.; Duque, S.

    2016-02-01

    ZnMnO thin films were grown by Pulsed Laser Deposition (PLD) technique onto Silicon (100) substrates at different growth conditions. Thin films were deposited varying Mn concentration, substrate temperature and oxygen pressure. ZnMnO samples were analysed by using Raman Spectroscopy that shows a red shift for all vibration modes. Raman spectra revealed that nanostructure of thin films was the same of ZnO bulk, wurzite hexagonal structure. The structural disorder was manifested in the line width and shape variations of E2(high) and E2(low) modes located in 99 and 434cm-1 respectively, which may be due to the incorporation of Mn ions inside the ZnO crystal lattice. Around 570cm-1 was found a peak associated to E1(LO) vibration mode of ZnO. 272cm-1 suggest intrinsic host lattice defects. Additional mode centred at about 520cm-1 can be overlap of Si and Mn modes.

  18. Quantitative assessment of molecular dynamics-grown amorphous silicon and germanium films on silicon (111)

    NASA Astrophysics Data System (ADS)

    Käshammer, Peter; Borgardt, Nikolai I.; Seibt, Michael; Sinno, Talid

    2016-09-01

    Molecular dynamics based on the empirical Tersoff potential was used to simulate the deposition of amorphous silicon and germanium on silicon(111) at various deposition rates and temperatures. The resulting films were analyzed quantitatively by comparing one-dimensional atomic density profiles to experimental measurements. It is found that the simulations are able to capture well the structural features of the deposited films, which exhibit a gradual loss of crystalline order over several monolayers. A simple mechanistic model is used to demonstrate that the simulation temperature may be used to effectively accelerate the surface relaxation processes during deposition, leading to films that are consistent with experimental samples grown at deposition rates many orders-of-magnitude slower than possible in a molecular dynamics simulation.

  19. A study on the epitaxial Bi2Se3 thin film grown by vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Cheng; Chen, Yu-Sung; Lee, Chao-Chun; Wu, Jen-Kai; Lee, Hsin-Yen; Liang, Chi-Te; Chang, Yuan Huei

    2016-06-01

    We report the growth of high quality Bi2Se3 thin films on Al2O3 substrates by using chemical vapor deposition. From the atomic force microscope, x-ray diffraction and transmission electron microscope measurements we found that the films are of good crystalline quality, have two distinct domains and can be grown epitaxially on the Al2O3 substrate. Carrier concentration in the sample is found to be 1.1 × 1019 cm-3 between T = 2 K to T = 300 K, and electron mobility can reach 954 cm2/V s at T = 2 K. Weak anti-localization effect is observed in the low temperature magneto-transport measurement for the sample which indicates that the thin film has topological surface state.

  20. Electrochemical synthesis and properties of ceria films grown on stainless steel

    NASA Astrophysics Data System (ADS)

    Živković, Lj. S.; Lair, V.; Lupan, O.; Ringuedé, A.

    2011-12-01

    Electrochemical synthesis of ceria films was performed on a stainless steel substrate in view of Solid Oxide Fuel Cells (SOFC) applications. Films were obtained from aqueous nitrate solutions via cathodic deposition method at room temperature. A constant potential value of -0.8 V/(SCE) was applied to reduce the molecular oxygen as hydroxide precursor, leading to a formation of adherent, homogeneous and covering films in 20 min deposition time. Structure, morphology and composition of as-grown coatings were studied by X-ray diffraction, Raman and energy-dispersive X-ray spectroscopy, as well as scanning electron microscopy. Cubic fluorite-type nanostructured ceria of leaf-like particles was synthesized. Thermal annealing (600°C, 1 h) was found to enhance ceria crystallinity.

  1. Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

    NASA Astrophysics Data System (ADS)

    Miikkulainen, Ville; Leskelä, Markku; Ritala, Mikko; Puurunen, Riikka L.

    2013-01-01

    Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas-solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic-organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

  2. Epitaxial pentacene films grown on the surface of ion-beam-processed gate dielectric layer

    NASA Astrophysics Data System (ADS)

    Chou, W. Y.; Kuo, C. W.; Cheng, H. L.; Mai, Y. S.; Tang, F. C.; Lin, S. T.; Yeh, C. Y.; Horng, J. B.; Chia, C. T.; Liao, C. C.; Shu, D. Y.

    2006-06-01

    The following research describes the process of fabrication of pentacene films with submicron thickness, deposited by thermal evaporation in high vacuum. The films were fabricated with the aforementioned conditions and their characteristics were analyzed using x-ray diffraction, scanning electron microscopy, polarized Raman spectroscopy, and photoluminescence. Organic thin-film transistors (OTFTs) were fabricated on an indium tin oxide coated glass substrate, using an active layer of ordered pentacene molecules, which were grown at room temperature. Pentacene film was aligned using the ion-beam aligned method, which is typically employed to align liquid crystals. Electrical measurements taken on a thin-film transistor indicated an increase in the saturation current by a factor of 15. Pentacene-based OTFTs with argon ion-beam-processed gate dielectric layers of silicon dioxide, in which the direction of the ion beam was perpendicular to the current flow, exhibited a mobility that was up to an order of magnitude greater than that of the controlled device without ion-beam process; current on/off ratios of approximately 106 were obtained. Polarized Raman spectroscopy investigation indicated that the surface of the gate dielectric layer, treated with argon ion beam, enhanced the intermolecular coupling of pentacene molecules. The study also proposes the explanation for the mechanism of carrier transportation in pentacene films.

  3. Topological limit of ultrathin quasi-freestanding Bi2Te3 films grown on Si(111)

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wang, Huan-Hua; Bian, Guang; Bissen, Mark; Zhang, Zhan; Miller, Tom; Hong, Hawoong; Chiang, Tai-Chang

    2013-03-01

    A fundamental issue for ultrathin topological films is the thickness limit below which the topological surface states become impacted by interfacial interactions. We show that for Bi2Te3 grown on Si(111) this limit is four quintuple layers (QLs) based on angle-resolved photoemission measurements, using optimized photon energies and polarizations, of the Dirac cone warping and interaction-induced gap as a function of film thickness. The results are close to theoretical predictions for free-standing films, despite the expected strong bonding of the film with the reactive Si(111) substrate. In-situ surface X-ray scattering (SXS) study shows that a buffer layer exist on the Si(111) surface, which effectively saturates all the Si(111) dangling bonds. These interfacial properties, revealed only by diffractions from deeply penetrating X-rays, are critical in understanding the topological surface states in ultrathin films, where electronic coupling is strongly enhanced. Our SXS measurement also yields new information regarding the internal structures of these topological thin films, including layer stacking, QL-by-QL growth, relaxations, etc.

  4. Preparation and characterization of epitaxially grown unsupported yttria-stabilized zirconia (YSZ) thin films

    NASA Astrophysics Data System (ADS)

    Götsch, Thomas; Mayr, Lukas; Stöger-Pollach, Michael; Klötzer, Bernhard; Penner, Simon

    2015-03-01

    Epitaxially grown, chemically homogeneous yttria-stabilized zirconia thin films ("YSZ", 8 mol% Y2O3) are prepared by direct-current sputtering onto a single-crystalline NaCl(0 0 1) template at substrate temperatures ≥493 K, resulting in unsupported YSZ films after floating off NaCl in water. A combined methodological approach by dedicated (surface science) analytical characterization tools (transmission electron microscopy and diffraction, atomic force microscopy, angle-resolved X-ray photoelectron spectroscopy) reveals that the film grows mainly in a [0 0 1] zone axis and no Y-enrichment in surface or bulk regions takes place. In fact, the Y-content of the sputter target is preserved in the thin films. Analysis of the plasmon region in EEL spectra indicates a defective nature of the as-deposited films, which can be suppressed by post-deposition oxidation at 1073 K. This, however, induces considerable sintering, as deduced from surface morphology measurements by AFM. In due course, the so-prepared unsupported YSZ films might act as well-defined model systems also for technological applications.

  5. Spatially resolved Raman studies of diamond films grown by chemical vapor deposition

    SciTech Connect

    Ager, J.W. III; Veirs, D.K.; Rosenblatt, G.M. )

    1991-03-15

    The frequency and line shape of the diamond Raman line are examined in detail for a series of microwave-plasma-assisted chemical-vapor-deposition films grown on Si. The Raman lines in the films appear at higher frequency (shifts of up to 3 cm{sup {minus}1}) than that of natural diamond and the observed lines are symmetric with broader linewidths than that of natural diamond, ranging from 5.7 to 17.1 cm{sup {minus}1}. In addition, the line frequencies and linewidths are correlated; the films with the highest vibrational frequencies have the largest linewidths. The data include single-point measurements on eight films grown under different conditions as well as 500 data points from different positions on a single film that were obtained in a spatially resolved Raman experiment. Several mechanisms for the frequency shift and the correlation of the linewidth with frequency are considered including phonon confinement, residual stress, and defect scattering. Contrary to the observations, Raman line shapes computed from the phonon-confinement model (which has been used successfully to model Raman scattering in microcrystalline Si and GaAs), using phonon-dispersion curves for diamond from the literature, are highly asymmetric at the linewidths observed. It is concluded that the observed shifts in the diamond Raman line do not arise from phonon confinement alone and arise primarily from compressive stress. The line broadening also is not produced by phonon confinement alone and may arise from decreasing phonon lifetime associated with scattering from defects or from an inhomogeneous stress distribution in the films. The observed correlation between Raman line frequency and width suggests that the degree of compressive stress may be associated with the density of microcrystalline defects.

  6. Single-crystalline BaTiO3 films grown by gas-source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Matsubara, Yuya; Takahashi, Kei S.; Tokura, Yoshinori; Kawasaki, Masashi

    2014-12-01

    Thin BaTiO3 films were grown on GdScO3 (110) substrates by metalorganic gas-source molecular beam epitaxy. Titanium tetra-isopropoxide (TTIP) was used as a volatile precursor that provides a wide growth window of the supplied TTIP/Ba ratio for automatic adjustment of the film composition. Within the growth window, compressively strained films can be grown with excellent crystalline quality, whereas films grown outside of the growth window are relaxed with inferior crystallinity. This growth method will provide a way to study the intrinsic properties of ferroelectric BaTiO3 films and their heterostructures by precise control of the stoichiometry, structure, and purity.

  7. Perpendicular magnetic anisotropy in epitaxially strained cobalt-ferrite (001) thin films

    SciTech Connect

    Yanagihara, H. Utsumi, Y.; Niizeki, T. Inoue, J.; Kita, Eiji

    2014-05-07

    We investigated the dependencies of both the magnetization characteristics and the perpendicular magnetic anisotropy of Co{sub x}Fe{sub 3–x}O{sub 4}(001) epitaxial films (x = 0.5 and 0.75) on the growth conditions of the reactive magnetron sputtering process. Both saturation magnetization and the magnetic uniaxial anisotropy constant K{sub u} are strongly dependent on the reactive gas (O{sub 2}) flow rate, although there is little difference in the surface structures for all samples observed by reflection high-energy electron diffraction. In addition, certain dead-layer-like regions were observed in the initial stage of the film growth for all films. Our results suggest that the magnetic properties of Co{sub x}Fe{sub 3–x}O{sub 4} epitaxial films are governed by the oxidation state and the film structure at the vicinity of the interface.

  8. Impedance spectroscopy of the oxide films formed during high temperature oxidation of a cobalt-plated ferritic alloy

    NASA Astrophysics Data System (ADS)

    Velraj, S.; Zhu, J. H.; Painter, A. S.; Du, S. W.; Li, Y. T.

    2014-02-01

    Impedance spectroscopy was used to evaluate the oxide films formed on cobalt-coated Crofer 22 APU ferritic stainless steel after thermal oxidation at 800 °C in air for different times (i.e. 2, 50, 100 and 500 h). Impedance spectra of the oxide films exhibited two or three semicircles depending on the oxidation time, which correspond to the presence of two or three individual oxide layers. Coupled with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD), the individual oxide layer corresponding to each semicircle was determined unambiguously. Impedance spectrum analysis of the oxide films formed on the sample after thermal exposure at 800 °C in air for 2 h led to the identification of the low-frequency and high-frequency semicircles as being from Cr2O3 and Co3O4, respectively. SEM/EDS and XRD analysis of the 500-h sample clearly revealed the presence of three oxide layers, analyzed to be Co3-xCrxO4, CoCr2O4, and Cr2O3. Although the SEM images of the 50-h and 100-h samples did not clearly show the CoCr2O4 layer, impedance plots implied their presence. The oxide scales were assigned to their respective semicircles and the electrical properties of Co3-xCrxO4, CoCr2O4 and Cr2O3 were determined from the impedance data.

  9. High resolution transmission electron microscopy study of diamond films grown from fullerene precursors

    SciTech Connect

    Luo, J.S.; Gruen, D.M.; Krauss, A.R.

    1995-07-01

    High-resolution transmission electron microscopy (HRTEM) has been used to investigate the microstructure of diamond films grown by plasma-assisted chemical vapor deposition using fullerene precursors. HRTEM observations of as-grown films revealed an array of larger crystals (>200 nm) within a polycrystalline matrix of much smaller crystallites (<20 nm). The randomly oriented small crystallites were nearly free of structural imperfections such as stacking faults or twins, while the larger ones had preferred <110> orientations with respect to the Si (100) substrate and showed evidence of structural defects on the periphery of the crystals. The most common defects were V-shaped {Sigma}9 twin boundaries, which are generally believed to serve as re-entrant sites for diamond nucleation and growth. The observation of growth steps on both (111) and (110) surfaces seems to support a reaction model in which fragments of C{sub 60}, including C{sub 2}, are considered the growth species. In particular, the nanocrystallinity of the films is most likely due to a high carbon cluster density from C{sub 60} fragmentation at or near the diamond surface, which can serve as nucleation sites for the growth of new crystallites.

  10. Transparent conductive Al-doped ZnO thin films grown at room temperature

    SciTech Connect

    Wang Yuping; Lu Jianguo; Bie Xun; Gong Li; Li Xiang; Song Da; Zhao Xuyang; Ye Wenyi; Ye Zhizhen

    2011-05-15

    Aluminum-doped ZnO (ZnO:Al, AZO) thin films were prepared on glass substrates by dc reactive magnetron sputtering from a Zn-Al alloy target at room temperature. The effects of the Ar-to-O{sub 2} partial pressure ratios on the structural, electrical, and optical properties of AZO films were studied in detail. AZO films grown using 100:4 to 100:8 Ar-to-O{sub 2} ratio result in acceptable quality films with c-axis orientated crystals, uniform grains, 10{sup -3} {Omega} cm resistivity, greater than 10{sup 20} cm{sup -3} electron concentration, and high transmittance, 90%, in the visible region. The lowest resistivity of 4.11x10{sup -3} {Omega} cm was obtained under the Ar-to-O{sub 2} partial pressure ratio of 100:4. A relatively strong UV emission at {approx}3.26 eV was observed in the room-temperature photoluminescence spectrum. X-ray photoelectron spectroscopy analysis confirmed that Al was introduced into ZnO and substitutes for Zn and doped the film n-type.

  11. Heteroepitaxial film silicon solar cell grown on Ni-W foils

    SciTech Connect

    Wee, Sung Hun; Cantoni, Claudia; Fanning, Thomas; Teplin, Charles; Bogorin, Daniela Florentina; Bornstein, Jon; Bowers, Karen; Schroeter,; Hasoon, Falah; Branz, Howard; Paranthaman, Mariappan Parans; Goyal, Amit

    2013-01-01

    Today, silicon-wafer-based technology dominates the photovoltaic (PV) industry because it enables high efficiency, is produced from abundant, non-toxic materials and is proven in the PV marketplace.[1] However, costs associated with the wafer itself limit ultimate cost reductions.[1,2] PV based on absorber layers of crystalline Si with only 2 to 10 m thickness are a promising route to reduce these costs, while maintaining efficiencies above 15%.[3-5] With the goal of fabricating low-cost film crystalline Si (c-Si), recent research has explored wafer peeling,[6,7] crystallization of amorphous silicon films on glass,[4,8-10] and seed and epitaxy approaches.[3,5,11] In this third approach, one initially forms a seed layer that establishes the grain size and crystalline order. The Si layer is then grown heteroepitaxially on the seed layer, so that it replicates the seed crystal structure. In all of these film c-Si approaches, the critical challenge is to grow c-Si with adequate material quality: specifically, the diffusion length (LD) must be at least three times the film thickness.[12] In polycrystalline Si films, grain boundaries (GBs) are recombination-active and significantly reduce LD. This adverse effects of GBs motivates research into growth of large grained c-Si [13,14] (for a low density of GBs) and biaxially-textured c-Si [11] (for low-angle GBs).

  12. Characterization of high-quality Bi2Se3 films grown using a selenium cracker source

    NASA Astrophysics Data System (ADS)

    Ginley, Theresa; Law, Stephanie

    Topological insulators, including Bi2Se3, are becoming increasingly prevalent in research due to their unique electronic properties--these materials exhibit an insulating bulk but conducting surfaces with electron spin-momentum locking. Using Molecular Beam Epitaxy (MBE) it is possible to grow high-quality thin films of Bi2Se3. Yet these films have not lived up to their potential, in part due to significant bulk conductivity arising from material defects like selenium vacancies. Current MBE growth methods for Bi2Se3 use standard selenium sources that evaporate large selenium molecules which must then be cracked into smaller molecules to be incorporated into the film. This process is inefficient and requires very high fluxes of selenium for good quality growths. However, using a selenium cracking source results in the evaporation of monomers and dimers, facilitating incorporation into the film. We will present electrical, structural, and optical measurements demonstrating that the use of a cracker source allows films to be grown using much lower selenium:bismuth flux ratios with good mobility and low carrier density. T. G. and S. L. gratefully acknowledge funding from the University of Delaware Research Foundation Grant 15A00862.

  13. Epitaxially-Grown Europium-Doped Barium Titanate Films on Various Substrates for Red Emission.

    PubMed

    Hwang, Kyu-Seog; Jeon, Young-Sun; Lee, Young-Hwan; Hwangbo, Seung; Kim, Jin-Tae

    2015-10-01

    Intense red photoluminescence under ultraviolet excitation was observed in epitaxially-grown europium-doped perovskite BaTiO3 thin films deposited on the SrTiO3 (100), MgO (100) and sapphire (0001) substrates using metal carboxylate complexes. Precursor films prepared by spin coating were pyrolyzed at 250 °C for 120 min in argon, followed by final annealing at 850 °C for 60 min in argon. Crystallinity and epitaxy of the films were analyzed by X-ray diffraction θ-2θ scan and pole-figure analysis. Photoluminescence of the thin films at room temperature under 254 nm was confirmed by a fluorescent spectrophotometer. The obtained epitaxial BaTiO3 thin films on the SrTiO3 (100) and MgO (100) substrates show an intense red-emission lines at 615 nm corresponding to the (5)D0 --> (7)F2 transitions on Eu(3+) with broad bands at 595 and 650 nm. PMID:26726427

  14. Photoluminescence of localized excitons in ZnCdO thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, T. Y.; Huang, Y. S.; Hu, S. Y.; Lee, Y. C.; Tiong, K. K.; Chang, C. C.; Shen, J. L.; Chou, W. C.

    2016-07-01

    We have investigated the luminescence characteristics of Zn1-xCdxO thin films with different Cd contents grown by molecular beam epitaxy system. The temperature-dependent photoluminescence (PL) and excitation power-dependent PL spectra were measured to clarify the luminescence mechanisms of the Zn1-xCdxO thin films. The peak energy of the Zn1-xCdxO thin films with increasing the Cd concentration is observed as redshift and can be fitted by the quadratic function of alloy content. The broadened full-width at half-maximum (FWHM) estimated from the 15 K PL spectra as a function of Cd content shows a larger deviation between the experimental values and theoretical curve, which indicates that experimental FWHM values are affected not only by alloy compositional disorder but also by localized excitons occupying states in the tail of the density of states. The Urbach energy determined from an analysis of the lineshape of the low-energy side of the PL spectrum and the degree of localization effect estimated from the temperature-induced S-shaped PL peak position described an increasing mean exciton-localization effects in ZnCdO films with increasing the Cd content. In addition, the PL intensity and peak position as a function of excitation power are carried out to clarify the types of radiative recombination and the effects of localized exciton in the ZnCdO films with different Cd contents.

  15. Epitaxial composition-graded perovskite films grown by a dual-beam pulsed laser deposition method

    NASA Astrophysics Data System (ADS)

    Sakai, Joe; Autret-Lambert, Cécile; Sauvage, Thierry; Courtois, Blandine; Wolfman, Jérôme; Gervais, François

    2013-10-01

    We prepared SrTiO3 (STO) to Ba0.6Sr0.4TiO3 (BST06) out-of-plane composition-graded films on STO (100) substrates by means of a dual-beam dual-target pulsed laser deposition technique. In the deposition system, a sliding mirror divides one KrF excimer laser beam into two, realizing the dual-beam of controlled intensity ratio. X-ray diffraction reciprocal space mapping has revealed that the graded films deposited under oxygen pressure at or lower than 1×10-3 mbar were coherently strained with the same in-plane lattice parameter as the substrate. Their composition gradient along the growth direction was confirmed by Rutherford backscattering analysis to be uniform. We deposited BST06 top layers of various thickness on epitaxial composition-graded (ECG) buffer layers and examined their coherency and crystallinity. In comparison with the cases of STO homoepitaxial buffer layers, ECG buffer layers achieved better crystallinity of top BST06 layers, suggesting that the crystallinity of a heteroepitaxially-grown film is affected not only by the in-plane lattice matching but also by the out-of-plane lattice continuity with the substrate. ECG films that bridge compositions of substrate and top layer materials can be useful buffer layers for epitaxial growth of lattice-mismatched oxide films.

  16. Acceptor states in heteroepitaxial CdHgTe films grown by molecular-beam epitaxy

    SciTech Connect

    Mynbaev, K. D.; Shilyaev, A. V. Bazhenov, N. L.; Izhnin, A. I.; Izhnin, I. I.; Mikhailov, N. N.; Varavin, V. S.; Dvoretsky, S. A.

    2015-03-15

    The photoluminescence method is used to study acceptor states in CdHgTe heteroepitaxial films (HEFs) grown by molecular-beam epitaxy. A comparison of the photoluminescence spectra of HEFs grown on GaAs substrates (CdHgTe/GaAs) with the spectra of CdHgTe/Si HEFs demonstrates that acceptor states with energy depths of about 18 and 27 meV are specific to CdHgTe/GaAs HEFs. The possible nature of these states and its relation to the HEF synthesis conditions and, in particular, to the vacancy doping occurring under conditions of a mercury deficiency during the course of epitaxy and postgrowth processing are discussed.

  17. The magnetic and chemical structural property of the epitaxially-grown multilayered thin film

    NASA Astrophysics Data System (ADS)

    Lee, Hwachol

    L10 FePt- and Fe-related alloys such as FePtRh, FeRh and FeRhPd have been studied for the high magnetocrystalline anisotropy and magnetic phase transition property for the future application. In this work, the thin film structural and magnetic property is investigated for the selected FePtRh and FeRhPd alloys. The compositionally-modulated L10 FePtRh multilayered structure is grown epitaxially on a-plane Al2O3 with Cr and Pt buffer layer at 600degC growth temperature by DC sputtering technique and examined for the structural, interfacial and magnetic property. For the epitaxially grown L10 [Fe50Pt45Rh5 (FM) (10nm) / Fe50Pt25Rh25 (AFM) (20nm)]x8 superlattice, the magnetically and chemically sharp interface formation between layers was observed in X-ray diffraction, transmission electron microscopy and polarized neutron reflectivity measurements with the negligible exchange bias at room and a slight coupling effect at lower temperature regime. For FeRhPd, the magnetic phase transition of epitaxially-grown 111-oriented Fe46Rh48Pd6 thin film is studied. The applied Rhodium buffer layer on a-plane Al2O3 (11 20) at 600degC shows the extraordinarily high quality of epitaxial film in (111) orientation, where two broad and coherent peak in rocking curve, and Laue oscillations are observed. The epitaxially-grown Pd-doped FeRh on Pt (111) grown at 600degC, 700degC exhibits the co-existing stable L10 (111) and B2 (110) structures and magnetic phase transition around 300degC. On the other hand, the partially-ordered FeRhPd structure grown at 400degC, 500degC shows background high ferromagnetic state over 5K˜350K temperature. For the reduced thickness of Fe46Rh48Pd 6, the ferromagnetic state becomes dominant with a reduced portion of the film undergoing a magnetic phase transition. For some epitaxial FeRhPd film, the spin-glass-like disordered state is also observed in field dependent SQUID measurement. For the tri-layered FeRhPd with thin Pt spacer, the background

  18. Properties of CsI, CsBr and GaAs thin films grown by pulsed laser deposition

    SciTech Connect

    Brendel, V M; Garnov, S V; Yagafarov, T F; Iskhakova, L D; Ermakov, R P

    2014-09-30

    CsI, CsBr and GaAs thin films have been grown by pulsed laser deposition on glass substrates. The morphology and structure of the films have been studied using X-ray diffraction and scanning electron microscopy. The CsI and CsBr films were identical in stoichiometry to the respective targets and had a polycrystalline structure. Increasing the substrate temperature led to an increase in the density of the films. All the GaAs films differed in stoichiometry from the target. An explanation was proposed for this fact. The present results demonstrate that, when the congruent transport condition is not fulfilled, films identical in stoichiometry to targets can be grown by pulsed laser deposition in the case of materials with a low melting point and thermal conductivity. (interaction of laser radiation with matter)

  19. High frequency capacitance-voltage characteristics of thermally grown SiO2 films on beta-SiC

    NASA Technical Reports Server (NTRS)

    Tang, S. M.; Berry, W. B.; Kwor, R.; Zeller, M. V.; Matus, L. G.

    1990-01-01

    Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.

  20. Planar millimeter wave band-stop filters based on the excitation of confined magnetostatic waves in barium hexagonal ferrite thin film strips

    NASA Astrophysics Data System (ADS)

    Lu, Lei; Song, Young-Yeal; Bevivino, Joshua; Wu, Mingzhong

    2011-05-01

    A planar millimeter wave band-stop filter based on confined magnetostatic wave (MSW) excitations in an M-type barium hexagonal ferrite (BaM) film strip was demonstrated. The device consists of a BaM film strip on the top of a coplanar waveguide with the strip length along the signal line. For zero magnetic fields, the device shows a band-stop filtering response at 53 GHz. This response originates from the excitation of confined MSW modes across the BaM strip width. The filter operation frequency is tunable with low fields. This tuning relies on the change in the MSW dispersion with field.

  1. Continuous spin reorientation transition in epitaxially grown antiferromagnetic NiO thin films

    SciTech Connect

    Li, J.; Arenholz, E.; Meng, Y.; Tan, A.; Park, J.; Jin, E.; Son, H.; Wu, J.; Jenkins, C. A.; Scholl, A.; Hwang, Chanyong; Qiu, Z. Q.

    2011-03-01

    Fe/NiO/MgO/Ag(001) films were grown epitaxially, and the Fe and NiO spin orientations were determined using x-ray magnetic dichroism. We find that the NiO spins are aligned perpendicularly to the in-plane Fe spins. Analyzing both the in-plane and out-of-plane spin components of the NiO layer, we demonstrate unambiguously that the antiferromagnetic NiO spins undergo a continuous spin reorientation transition from the in-plane to out-of-plane directions with increasing of the MgO thickness.

  2. Synthesis and characterization of TiO2 nanostructure thin films grown by thermal CVD

    NASA Astrophysics Data System (ADS)

    Rizal, Umesh; Das, Soham; Kumar, Dhruva; Swain, Bhabani S.; Swain, Bibhu P.

    2016-04-01

    Thermal Chemical Vapor Deposition (CVD) deposited Titanium dioxide nanostructures (TiO2-NSs) were grown by using Ti powder and O2 precursors on Si/SiO2 (100) substrate. The microstructure and vibration properties of TiO2-NSs were characterized by Fourier transform infrared (FTIR), SEM, and photoluminescence (PL) spectroscopy. The role of O2 flow rate on TiO2-NSs revealed decreased deposition rate, however, surface roughness has been increased resulted into formation of nanostructure thin films.

  3. Impedance analysis of different cell monolayers grown on gold-film electrodes.

    PubMed

    Reiss, Bjoern; Wegener, Joachim

    2015-08-01

    Impedance analysis of mammalian cells grown on planar film electrodes provides a label-free, non-invasive and unbiased observation of cell-based assays addressing the biological response to drugs, toxins or stressors in general. Whereas the time course of the measured impedance at one particular frequency has been used a lot for quantitative monitoring, in-depth analysis of the frequency-dependent impedance spectra is rarely performed. This study summarizes and validates the existing model for spectral analysis by applying it to eight different cell types from different mammalian tissues. Model parameters correctly predict the functional and/or structural properties of the individual cells under study. PMID:26737923

  4. Lutetium-doped EuO films grown by molecular-beam epitaxy

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Shai, D. E.; Monkman, E. J.; Harter, J. W.; Hollaender, B.; Schubert, J.; Shen, K. M.; Mannhart, J.; Schlom, D. G.

    2012-05-28

    The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

  5. Resistive memory switching in ultrathin TiO2 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Sahu, V. K.; Misra, P.; Ajimsha, R. S.; Das, A. K.; Joshi, M. P.; Kukreja, L. M.

    2016-05-01

    Electric field controlled forming free and unipolar resistive memory switching was observed in Au/TiO2/Pt devices containing ultrathin TiO2 films of thickness ~ 4 nm grown by atomic layer deposition. These devices showed a large resistance ratio of ~ 103 between high and low resistance states along with appreciable time retention for ~ 104 seconds and endurance. The spread of reset and set voltages was from ~ 0.4-0.6 V and 1.1-1.5 V respectively with a clear window between them. The resistive switching mechanism was explained based on conductive filamentary model.

  6. Magnetic properties of MnAs thin films grown on GaAs (0 0 1) by MOVPE

    NASA Astrophysics Data System (ADS)

    Sterbinsky, G. E.; May, S. J.; Chiu, P. T.; Wessels, B. W.

    2007-01-01

    The thickness dependence of the in-plane uniaxial anisotropy and coercive field of epitaxial MnAs thin films on GaAs (0 0 1) substrates has been determined from the magneto-optic Kerr effect. The metalorganic vapor phase epitaxy grown films are single α phase at room temperature with a B-type variant orientation. The coercive field of these films increases to a maximum for a film 35 nm thick and then decreases in thicker films. An increase in magnetic anisotropy field with increasing thickness is observed and is attributed to an increasing volume contribution to the anisotropy constant.

  7. Growth and structure of MBE grown TiO2 anatase films with rutile nano-crystallites

    SciTech Connect

    Shao, Rui; Wang, Chong M.; McCready, David E.; Droubay, Timothy C.; Chambers, Scott A.

    2007-03-15

    We have grown TiO2 anatase films with rutile nanocrystalline inclusions using molecular beam epitaxy under different growth conditions. This model system is important for investigating the role of rutile/anatase interfaces in heterogeneous photocatalysis. To control the film structure, we grew a pure anatase (001) layer at a slow rate and then increased the growth rate to drive the nucleation of rutile particles. Structure analysis indicates that the rutile phase has four preferred orientations in the anatase film.

  8. In situ-grown hexagonal silicon nanocrystals in silicon carbide-based films

    PubMed Central

    2012-01-01

    Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by adjusting the flow rate of the silane gas. We suggest that this phenomenon is attributed to the quantum confinement effect of hexagonal Si-NCs in silicon carbide-based film with a change in the sizes and emission states of the NCs. PMID:23171576

  9. Structural and optical characterization of MOCVD-grown ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pagni, O.; James, G. R.; Leitch, A. W. R.

    2004-03-01

    We report on the characterization of ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) using diethyl zinc (DEZ) and tert-butanol (TBOH) as precursors. Substrate temperature proved to be a crucial factor in the crystallization process, as it vastly impacted the structural properties of the samples studied. Highly c-axis oriented films with large grain size (52 nm), low tensile strain (0.6%), uniform substrate coverage and a columnar structure devoid of hexagonal needles were successfully deposited on n-Si (100) substrates. The temperature-dependent luminescence spectra recorded confirmed the excellent quality of the material obtained in this work. Our results so far set TBOH apart as an outstanding oxygen source for the MOCVD growth of ZnO.

  10. Nanocolumnar association and domain formation in porous thin films grown by evaporation at oblique angles.

    PubMed

    Lopez-Santos, C; Alvarez, R; Garcia-Valenzuela, A; Rico, V; Loeffler, M; Gonzalez-Elipe, A R; Palmero, A

    2016-09-30

    Porous thin films grown at oblique angles by evaporation techniques are formed by tilted nanocolumnar structures which, depending on the material type and growth conditions, associate along certain preferential directions, giving rise to large domains. This arrangement, commonly denoted as bundling association, is investigated in the present work by performing fundamental experiments and growth simulations. It is proved that trapping processes of vapor species at the film surface, together with the shadowing mechanism, mediate the anisotropic widening of the nanocolumns and promote their preferential coalescence along certain directions, giving rise to domains with different shape and size. The role of these two processes is thoroughly studied in connection with the formation of these domains in materials as different as SiO2 and TiO2. PMID:27535651

  11. Raman spectra of MOCVD-grown ferroelectric PbTiO{sub 3} thin films

    SciTech Connect

    Feng, Z.C.; Kwak, B.S. |; Erbil, A.; Boatner, L.A.

    1993-12-31

    Lead titanate (PbTiO{sub 3}) has been grown on a variety of substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. The substrates employed included Si, GaAs, MgO, fused-quartz, sapphire, and KTaO{sub 3}. Raman spectra from these heterostructures are presented. All of the films exhibited the strong, narrow spectral features characteristic of PbTiO{sub 3} perovskite-oxide crystals and indicative of high crystalline quality. The temperature behavior of the Raman modes, including the so-called ``soft-mode,`` was studied. A ``difference-Raman`` technique was used to distinguish the contributions of the PbTiO{sub 3} film and the KTaO{sub 3} single-crystal substrate.

  12. STM/STS study of graphene directly grown on h-BN films on Cu foils

    NASA Astrophysics Data System (ADS)

    Jang, Won-Jun; Wang, Min; Jang, Seong-Gyu; Kim, Minwoo; Park, Seong-Yong; Kim, Sang-Woo; Kahng, Se-Jong; Choi, Jae-Young; Song, Young; Lee, Sungjoo; Sanit Collaboration; Department Of Physics, Korea University Collaboration; Graphene Research Center, Samsung Advanced Institute Of Technology Collaboration

    2013-03-01

    Graphene-based devices on standard SiO2 substrate commonly exhibit inferior characteristics relative to the expected intrinsic properties of graphene, due to the disorder existing at graphene-SiO2 interface. Recently, it has been shown that exfoliated and chemical vapor deposition (CVD) graphene transferred onto hexagonal boron nitride (h-BN) possesses significantly reduced charge inhomogeneity, and yields improved device performance. Here we report the scanning tunneling microscopy (STM) and spectroscopy (STS) results obtained from a graphene layer directly grown on h-BN insulating films on Cu foils. STS measurements illustrate that graphene/h-BN film is charge neutral without electronic perturbation from h-BN/Cu substrate. Corresponding Author

  13. Electrochemical delamination of CVD-grown graphene film: toward the recyclable use of copper catalyst.

    PubMed

    Wang, Yu; Zheng, Yi; Xu, Xiangfan; Dubuisson, Emilie; Bao, Qiaoliang; Lu, Jiong; Loh, Kian Ping

    2011-12-27

    The separation of chemical vapor deposited (CVD) graphene from the metallic catalyst it is grown on, followed by a subsequent transfer to a dielectric substrate, is currently the adopted method for device fabrication. Most transfer techniques use a chemical etching method to dissolve the metal catalysts, thus imposing high material cost in large-scale fabrication. Here, we demonstrate a highly efficient, nondestructive electrochemical route for the delamination of CVD graphene film from metal surfaces. The electrochemically delaminated graphene films are continuous over 95% of the surface and exhibit increasingly better electronic quality after several growth cycles on the reused copper catalyst, due to the suppression of quasi-periodical nanoripples induced by copper step edges. The electrochemical delamination process affords the advantages of high efficiency, low-cost recyclability, and minimal use of etching chemicals. PMID:22034835

  14. In situ-grown hexagonal silicon nanocrystals in silicon carbide-based films.

    PubMed

    Kim, Tae-Youb; Huh, Chul; Park, Nae-Man; Choi, Cheol-Jong; Suemitsu, Maki

    2012-01-01

    Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by adjusting the flow rate of the silane gas. We suggest that this phenomenon is attributed to the quantum confinement effect of hexagonal Si-NCs in silicon carbide-based film with a change in the sizes and emission states of the NCs. PMID:23171576

  15. Structural evolution of platinum thin films grown by atomic layer deposition

    SciTech Connect

    Geyer, Scott M.; Methaapanon, Rungthiwa; Bent, Stacey; Johnson, Richard; Clemens, Bruce; Brennan, Sean; Toney, Mike F.

    2014-08-14

    The structural properties of Pt films grown by atomic layer deposition (ALD) are investigated with synchrotron based x-ray scattering and x-ray diffraction techniques. Using grazing incidence small angle scattering, we measure the lateral growth rate of the Pt islands to be 1.0 Å/cycle. High resolution x-ray diffraction reveals that the in-plane strain of the Pt lattice undergoes a transition from compressive strain to tensile strain when the individual islands coalescence into a continuous film. This transition to tensile strain is attributed to the lateral expansion that occurs when neighboring islands merge to reduce their surface energy. Using 2D grazing incidence x-ray diffraction, we show that the lattice orientation becomes more (111) oriented during deposition, with a sharp transition occurring during coalescence. Pt ALD performed at a lower deposition temperature (250 °C) is shown to result in significantly more randomly oriented grains.

  16. Nanoscale magnetization reversal caused by electric field-induced ion migration and redistribution in cobalt ferrite thin films.

    PubMed

    Chen, Xinxin; Zhu, Xiaojian; Xiao, Wen; Liu, Gang; Feng, Yuan Ping; Ding, Jun; Li, Run-Wei

    2015-04-28

    Reversible nanoscale magnetization reversal controlled merely by electric fields is still challenging at the moment. In this report, first-principles calculation indicates that electric field-induced magnetization reversal can be achieved by the appearance of unidirectional magnetic anisotropy along the (110) direction in Fe-deficient cobalt ferrite (CoFe(2-x)O4, CFO), as a result of the migration and local redistribution of the Co(2+) ions adjacent to the B-site Fe vacancies. In good agreement with the theoretical model, we experimentally observed that in the CFO thin films the nanoscale magnetization can be reversibly and nonvolatilely reversed at room temperature via an electrical ion-manipulation approach, wherein the application of electric fields with appropriate polarity and amplitude can modulate the size of magnetic domains with different magnetizations up to 70%. With the low power consumption (subpicojoule) characteristics and the elimination of external magnetic field, the observed electric field-induced magnetization reversal can be used for the construction of energy-efficient spintronic devices, e.g., low-power electric-write and magnetic-read memories. PMID:25794422

  17. Thermal stability of MBE-grown epitaxial MoSe2 and WSe2 thin films

    NASA Astrophysics Data System (ADS)

    Chang, Young Jun; Choy, Byoung Ki; Phark, Soo-Hyon; Kim, Minu

    Layered transition metal dichalcogenides (TMDs) draw much attention, because of its unique optical properties and band structures depending on the layer thicknesses. However, MBE growth of epitaxial films demands information about thermal stability of stoichiometry and related electronic structure for high temperature range. We grow epitaxial MoSe2 and WSe2 ultrathin films by using molecular beam epitaxy (MBE). We characterize stoichiometry of films grown at various growth temperature by using various methods, XPS, EDX, and TOF-MEIS. We further test high temperature stability of electronic structure for those films by utilizing in-situ ellipsometry attached to UHV chamber. We discuss threshold temperatures up to 700~1000oC, at which electronic phases changes from semiconductor to metal due to selenium deficiency. This information can be useful for potential application of TMDs for fabrication of Van der Waals multilayers and related devices. This research was supported by Nano.Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning. (2009-0082580), NRF-2014R1A1A1002868.

  18. Electrochromism and photocatalysis in dendrite structured Ti:WO3 thin films grown by sputtering

    NASA Astrophysics Data System (ADS)

    Karuppasamy, A.

    2015-12-01

    Titanium doped tungsten oxide (Ti:WO3) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O2 atmosphere. Ti:WO3 thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10-3-5.0 × 10-3 mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm2) and tungsten (3 W/cm2) were kept constant. Ti:WO3 films deposited at an oxygen pressure of 5 × 10-3 mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ = 550 nm), coloration efficiency (60 cm2/C at λ = 550 nm), electron/ion storage and removal capacity (Qc: -22.01 mC/cm2, Qa: 17.72 mC/cm2), reversibility (80%) and methylene blue decomposition rate (-1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO3 films.

  19. Scaling behavior of ZnPc thin films grown on CuI interlayers

    NASA Astrophysics Data System (ADS)

    Lee, Jinho; Jin, Sung-Il; Park, Chan Ryang; Yim, Sanggyu

    2015-01-01

    The growth behavior and consequent surface morphology evolution of zinc phthalocyanine (ZnPc) thin films deposited on a CuI interlayer were studied using atomic force microscopy and height difference correlation function (HDCF) analysis. The planar phthalocyanine thin films grown on non-interacting substrates have previously been reported to show anomalous scaling behavior such as large growth exponents, ß, sometimes larger than 0.5, and small anomaly values, ρ, typically smaller than 0.6. In contrast, ZnPc thin films on a CuI interlayer (CuI/ ZnPc) in this work showed conventional scaling behavior with a ß value of 0.26 ± 0.05 and a ρ value of 0.91. The HDCF analyses and x-ray diffraction results indicate that the expected interdigitated electron donor-acceptor interface was hardly formed for the CuI/ZnPc thin film system due to the lack of surface-parallel crystallites with high step edge barriers.

  20. Characterization of strontium barium niobate optical thin film grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Liu, H.; Li, S.; Fernandez, F. E.; Jia, W.; Liu, G.

    1999-12-01

    Optical quality thin films of strontium barium niobate SrxBa1-xNb2O6 either undoped or Eu3+-doped has been successfully grown on fused quartz substrates using pulsed laser deposition (PLD) technique. The optical properties were characterized in either time domain or in frequency domain. Undoped SBN thin films show a broad-band emission at UV, extending to the visible, which attributes to the exciton luminescence of the SBN host in the film. High-resolution nonlinear optical response in the picosecond region, as well as the third-order susceptibility were characterized by degenerate four-wave-mixing (DFWM) measurements. A considerable enhancement, by 2 orders of magnitude, of the third order nonlinear susceptibility χ(3) in transverse alignment was observed with respect to the bulk values. Eu3+-doped SBN films show a significant change in optical properties with annealing process. The fine structure of 5D0 to 7F multiplet emission was well resolved in the annealed sample. In a hole-burning experiment, a hole of width 100 MHz with depth as high as 30% was burnt using laser pumping at 5774 Å. It is suggested that Eu3+ ions may substitute Nb, occupying 6-fold sites.

  1. Characterization of strontium barium niobate optical thin film grown by pulsed laser deposition

    SciTech Connect

    Liu, H.; Fernandez, F. E.; Jia, W.; Li, S.; Liu, G.

    1999-12-02

    Optical quality thin films of strontium barium niobate Sr{sub x}Ba{sub 1-x}Nb{sub 2}O{sub 6} either undoped or Eu{sup 3+}-doped has been successfully grown on fused quartz substrates using pulsed laser deposition (PLD) technique. The optical properties were characterized in either time domain or in frequency domain. Undoped SBN thin films show a broad-band emission at UV, extending to the visible, which attributes to the exciton luminescence of the SBN host in the film. High-resolution nonlinear optical response in the picosecond region, as well as the third-order susceptibility were characterized by degenerate four-wave-mixing (DFWM) measurements. A considerable enhancement, by 2 orders of magnitude, of the third order nonlinear susceptibility {chi}{sup (3)} in transverse alignment was observed with respect to the bulk values. Eu{sup 3+}-doped SBN films show a significant change in optical properties with annealing process. The fine structure of {sup 5}D{sub 0} to {sup 7}F multiplet emission was well resolved in the annealed sample. In a hole-burning experiment, a hole of width 100 MHz with depth as high as 30% was burnt using laser pumping at 5774 A. It is suggested that Eu{sup 3+} ions may substitute Nb, occupying 6-fold sites.

  2. Rain erosion behavior of germanium carbide films grown on ZnS substrates

    NASA Astrophysics Data System (ADS)

    Mackowski, Jean-Marie; Cimma, B.; Pignard, R.; Colardelle, P.; Laprat, Patrice

    1992-12-01

    Thick germanium carbine films (GeC) are successfully grown on various Zinc Sulfide and Germanium substrates at temperatures up to 350 degree(s)C by two methods: Plasma Enhanced Chemical Vapor Deposition (PECVD) in gas mixtures of methane and germane and by Reactive Radio-Frequency Sputtering (RRFS) starting from a germanium target in a sputtering medium of methane and argon. The optical and mechanical properties of the GeC coatings depend on the composition determined by the deposition parameters. The refractive index at 633 nm varies from 4.9 to 4.3 for a carbon content ranging from 3 to 25% and the correlated refractive index in the 8 to 12 micrometers range is found to be between 3.96 and 3.1. For these coatings, the absorption coefficient is ranging from 270 to 40 cm-1. All films are amorphous in nature with domains ranging from 13 to 20 angstroms. The hydrogen content varies from 2 to 25% coming from C:H, Ge:H and C:Ge:H bonding. The XPS analysis shows the Ge:C precipitation kinetic for high deposition temperature or annealed films. The rain erosion resistance of GeC films and GeC with a protective diamond like-carbon (DLC) coating on top is measured for 1.2 mm water drop with an impact velocity ranging from 210 to 265 m/s on the Saab-Scania whirling-arm rig (Linkoping, Sweden).

  3. Induced polarized state in intentionally grown oxygen deficient KTaO{sub 3} thin films

    SciTech Connect

    Mota, D. A.; Romaguera-Barcelay, Y.; Tkach, A.; Agostinho Moreira, J.; Almeida, A.; Perez de la Cruz, J.; Vilarinho, P. M.; Tavares, P. B.

    2013-07-21

    Deliberately oxygen deficient potassium tantalate thin films were grown by RF magnetron sputtering on Si/SiO{sub 2}/Ti/Pt substrates. Once they were structurally characterized, the effect of oxygen vacancies on their electric properties was addressed by measuring leakage currents, dielectric constant, electric polarization, and thermally stimulated depolarization currents. By using K{sub 2}O rich KTaO{sub 3} targets and specific deposition conditions, KTaO{sub 3-{delta}} oxygen deficient thin films with a K/Ta = 1 ratio were obtained. Room temperature X-ray diffraction patterns show that KTaO{sub 3-{delta}} thin films are under a compressive strain of 2.3% relative to KTaO{sub 3} crystals. Leakage current results reveal the presence of a conductive mechanism, following the Poole-Frenkel formalism. Furthermore, dielectric, polarization, and depolarization current measurements yield the existence of a polarized state below T{sub pol} {approx} 367 Degree-Sign C. A Cole-Cole dipolar relaxation was also ascertained apparently due to oxygen vacancies induced dipoles. After thermal annealing the films in an oxygen atmosphere at a temperature above T{sub pol}, the aforementioned polarized state is suppressed, associated with a drastic oxygen vacancies reduction emerging from annealing process.

  4. SPM Study and Growth Mechanism of Graphene Directly CVD-Grown on h-BN Film

    NASA Astrophysics Data System (ADS)

    Song, Young Jae; Kim, Minwoo; Wu, Qinke; Lee, Joohyun; Lee, Sungjoo; Wang, Min

    2014-03-01

    We present our Scanning Tunneling Microscopy (STM)/Spectroscopy (STS) and Kelvin Probe Force Microscope (KPFM) study for graphene directly CVD-grown on h-BN film. High resolution STM image shows perfect honeycomb lattice structure of graphene on top surface and Moiré pattern indicating the structural interference patter with the underlying h-BN crystal. Non-disturbed electronic structure of graphene on h-BN film is also confirmed by spatially-resolved STS measurements, which show very sharp and symmetric V shape with a Dirac point at Fermi level. To confirm the graphene growth mechanism on h-BN film/Cu foil, careful Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy (KPFM) measurements were performed on different thickness of h-BN film on a SiO2 substrate to unveil the catalytic origin of graphene growth on h-BN/Cu. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP) (Grant Numbers: 2009-0083540, 2011-0030046, 2012R1A1A2020089 and 2012R1A1A1041416).

  5. Temperature dependence of mechanical stiffness and dissipation in ultrananocrystalline diamond films grown by the HFCVD techinque.

    SciTech Connect

    Adiga, V. P.; Sumant, A. V.; Suresh, S.; Gudeman, C.; Auciello, O.; Carlisle, J. A.; Carpick, R. W.; Materials Science Division; Univ. of Pennsylvania; Innovative Micro Tech.; Advanced Diamond Tech.

    2009-06-01

    We have characterized mechanical properties of ultrananocrystalline diamond (UNCD) thin films grown using the hot filament chemical vapor deposition (HFCVD) technique at 680 C, significantly lower than the conventional growth temperature of -800 C. The films have -4.3% sp{sup 2} content in the near-surface region as revealed by near edge x-ray absorption fine structure spectroscopy. The films, -1 {micro}m thick, exhibit a net residual compressive stress of 370 {+-} 1 MPa averaged over the entire 150 mm wafer. UNCD microcantilever resonator structures and overhanging ledges were fabricated using lithography, dry etching, and wet release techniques. Overhanging ledges of the films released from the substrate exhibited periodic undulations due to stress relaxation. This was used to determine a biaxial modulus of 838 {+-} 2 GPa. Resonant excitation and ring-down measurements in the kHz frequency range of the microcantilevers were conducted under ultrahigh vacuum (UHV) conditions in a customized UHV atomic force microscope system to determine Young's modulus as well as mechanical dissipation of cantilever structures at room temperature. Young's modulus is found to be 790 {+-} 30 GPa. Based on these measurements, Poisson's ratio is estimated to be 0.057 {+-} 0.038. The quality factors (Q) of these resonators ranged from 5000 to 16000. These Q values are lower than theoretically expected from the intrinsic properties of diamond. The results indicate that surface and bulk defects are the main contributors to the observed dissipation in UNCD resonators.

  6. Effect of annealing on the properties of zinc oxide nanofiber thin films grown by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Sadananda Kumar, N.; Bangera, Kasturi V.; Shivakumar, G. K.

    2013-01-01

    Zinc oxide nanofiber thin films have been deposited on glass substrate by spray pyrolysis technique. The X-ray diffraction studies revealed that the films are polycrystalline with the hexagonal structure and a preferred orientation along (002) direction for films annealed for 1 h at 450 °C. Further increase in annealing time changes the preferred orientation to (100) direction. The scanning electron microscopic analysis showed the formation of ZnO nanofiber with an average diameter of approximately 800 nm for annealed films. The compositional analysis of nanofiber ZnO thin films were studied by time of flight secondary ion mass spectroscopy, which indicated oxygen deficiency in the films. The optical properties of annealed films have shown a variation in the band gap between 3.29 and 3.20 eV. The electrical conductivity of the as grown and annealed films showed an increase in the conductivity by two orders of magnitude with increase in annealing duration.

  7. Spatial modulation of in-plane magnetic anisotropy in epitaxial Co(111) films grown on macrostep-bunched Si(111)

    SciTech Connect

    Davydenko, A. V. Kozlov, A. G.; Chebotkevich, L. A.

    2014-10-14

    We compared magnetic properties of epitaxial Co(111) films grown on microstep- and macrostep-bunched vicinal Si(111) substrates. A surface of the microstep-bunched Si(111) substrate represents regular array of step-bunches with height of 1.7 nm divided from each other by flat microterraces with a width of 34 nm. A surface of the macrostep-bunched Si(111) substrate is constituted by macrostep bunches with a height of 75–85 nm divided by atomically flat macroterraces. The average sum width of a macrostep bunch and a macroterrace is 2.3 μm. While in-plane magnetic anisotropy was spatially uniform in Co(111) films grown on the microstep-bunched Si(111), periodic macromodulation of the topography of the Si(111) substrate induced spatial modulation of in-plane magnetic anisotropy in Co(111) film grown on the macrostep-bunched Si(111) surface. The energy of uniaxial magnetic anisotropy in the areas of the Co(111) film deposited on the Si(111) macrosteps was higher more than by the order of magnitude than the energy of the magnetic anisotropy in the areas grown on macroterraces. Magnetization reversal in the areas with different energy of the magnetic anisotropy occurred in different magnetic fields. We showed the possibility of obtaining high density of domain walls in Co(111) film grown on the macrostep-bunched Si(111) by tuning the spatial step density of the Si(111) substrate.

  8. Orientation epitaxy of Ge1–xSnx films grown on single crystal CaF2 substrates

    DOE PAGESBeta

    A. J. Littlejohn; Zhang, L. H.; Lu, T. -M.; Kisslinger, K.; and Wang, G. -C.

    2016-03-15

    Ge1–xSnx films were grown via physical vapor deposition below the crystallization temperature of Ge on single crystal (111) and (100) CaF2 substrates to assess the role of Sn alloying in Ge crystallization. By studying samples grown at several growth temperatures ranging from 250 °C to 400 °C we report temperature-dependent trends in several of the films' properties. X-ray diffraction theta vs. two-theta (θ/2θ) scans indicate single orientation Ge1–xSnx(111) films are grown on CaF2(111) substrates at each temperature, while a temperature-dependent superposition of (111) and (100) orientations are exhibited in films grown on CaF2(100) above 250 °C. This is the firstmore » report of (111) oriented Ge1–xSnx grown on a (100) oriented CaF2 substrate, which is successfully predicted by a superlattice area matching model. These results are confirmed by X-ray diffraction pole figure analysis. θ/2θ results indicate substitutional Sn alloying in each film of about 5%, corroborated by energy dispersive spectroscopy. In addition, morphological and electrical properties are measured by scanning electron microscopy, atomic force microscopy and Hall mobility measurements and are also shown to be dependent upon growth temperature.« less

  9. Effect of precursor on epitaxially grown of ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate by hydrothermal technique

    SciTech Connect

    Sahoo, Trilochan; Ju, Jin-Woo; Kannan, V.; Kim, Jin Soo; Yu, Yeon-Tae; Han, Myung-Soo; Park, Young-Sik; Lee, In-Hwan

    2008-03-04

    Single crystalline ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate, using two different precursors by hydrothermal route at a temperature of 90 deg. C were successfully grown. The effect of starting precursor on crystalline nature, surface morphology and optical emission of the films were studied. ZnO thin films were grown in aqueous solution of zinc acetate and zinc nitrate. X-ray diffraction analysis revealed that all the thin films were single crystalline in nature and exhibited wurtzite symmetry and c-axis orientation. The thin films obtained with zinc nitrate had a more pitted rough surface morphology compared to the film grown in zinc acetate. However the thickness of the films remained unaffected by the nature of the starting precursor. Sharp luminescence peaks were observed from the thin films almost at identical energies but deep level emission was slightly prominent for the thin film grown in zinc nitrate.

  10. Surface reconstructions and transport of epitaxial PtLuSb (001) thin films grown by MBE

    NASA Astrophysics Data System (ADS)

    Patel, Sahil J.; Logan, John A.; Harrington, Sean D.; Schultz, Brian D.; Palmstrøm, Chris J.

    2016-02-01

    This work presents the surface reconstructions and transport properties of the topological insulator PtLuSb grown on Al0.1In0.9Sb/GaAs (001). Two stable surface reconstructions, (1×3) and c(2×2), were observed on PtLuSb (001) surfaces. Antimony-dimerization was determined to be the nature of the (1×3) surface reconstruction as evidenced by chemical binding energy shifts in the antimony 4d core-level for surface bonding components. The two surface reconstructions were studied as a function of Sb4 overpressure and substrate temperature to create a reconstruction phase diagram. From this reconstruction phase diagram, a growth window from 320 °C to 380 °C using an antimony overpressure was identified. Within this window, the highest quality films were grown at a growth temperature of 380 °C. These films exhibited lower p-type carrier concentrations as well as relatively high hole mobilities.

  11. Extraordinarily large perpendicular magnetic anisotropy in epitaxially strained cobalt-ferrite Co{sub x}Fe{sub 3−x}O{sub 4}(001) (x = 0.75, 1.0) thin films

    SciTech Connect

    Niizeki, Tomohiko; Utsumi, Yuji; Aoyama, Ryohei; Yanagihara, Hideto; Inoue, Jun-ichiro; Kita, Eiji; Yamasaki, Yuichi; Nakao, Hironori; Koike, Kazuyuki

    2013-10-14

    Perpendicular magnetic anisotropy (PMA) of cobalt-ferrite Co{sub x}Fe{sub 3-x}O{sub 4} (x = 0.75 and 1.0) epitaxial thin films grown on MgO (001) by a reactive magnetron sputtering technique was investigated. The saturation magnetization was found to be 430 emu/cm{sup 3} for x = 0.75, which is comparable to that of bulk CoFe{sub 2}O{sub 4} (425 emu/cm{sup 3}). Torque measurements afforded PMA constants of K{sub u}{sup eff}=9.0 Merg/cm{sup 3} (K{sub u}=10.0 Merg/cm{sup 3}) and K{sub u}{sup eff}=9.7 Merg/cm{sup 3} for x = 0.75 and 1.0, respectively. The value of K{sub u}{sup eff} extrapolated using Miyajima's plot was as high as 14.7 Merg/cm{sup 3} for x = 1.0. The in-plane four-fold magnetic anisotropy was evaluated to be 1.6 Merg/cm{sup 3} for x = 0.75. X-ray diffraction measurement revealed our films to be pseudomorphically strained on MgO (001) with a Poisson ratio of 0.4, leading to a considerable in-plane tensile strain by which the extraordinarily large PMA could be accounted for.

  12. Mosaic Structure Evolution in GaN Films with Annealing Time Grown by Metalorganic Chemical Vapour Deposition

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Tao; Xu, Ke; Guo, Li-Ping; Yang, Zhi-Jian; Pan, Yao-Bo; Su, Yue-Yong; Zhang, Han; Shen, Bo; Zhang, Guo-Yi

    2006-05-01

    We investigate mosaic structure evolution of GaN films annealed for a long time at 800°C grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show that residual stress in GaN films is relaxed by generating edge-type threading dislocations (TDs) instead of screw-type TDs. Compared to as-grown GaN films, the annealed ones have larger mean twist angles corresponding to higher density of edge-type TDs but smaller mean tilt angles corresponding to lower density of screw-type TDs films. Due to the increased edge-type TD density, the lateral coherence lengths of the annealed GaN films also decrease. The results obtained from chemical etching experiment and grazing-incidence x-ray diffraction (GIXRD) also support the proposed structure evolution.

  13. Structural and magnetic properties of epitaxial CrO2 thin films grown on TiO2 (001) substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Xueyu; Zhong, Xing; Visscher, P. B.; LeClair, Patrick R.; Gupta, Arunava

    2013-04-01

    The structural and magnetic properties of epitaxial CrO2 thin films grown on (001)-oriented TiO2 substrates by atmospheric pressure chemical vapor deposition are investigated. Due to the competition between demagnetization and a relatively weak perpendicular magnetocrystalline anisotropy, the deposited CrO2 (001) films exhibit magnetic properties that are significantly different from CrO2 (100) and CrO2 (110) films grown on TiO2 substrates. Based on the thickness dependence of M-H curves, a surface anisotropy is confirmed to exist, likely originating from strain in the film. The out-of-plane hysteresis curves can be well described by a distribution of effective anisotropy that may be due to a varying local demagnetizing field and a distribution of strain across the film. For the in-plane magnetization, the hysteresis curves are consistent with stripe or vortex domain structures of an almost closed flux configuration at remanence.

  14. Growth mechanism of CuZnInSe2 thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Tseng, Ya Hsin; Yang, Chu Shou; Wu, Chia Hsing; Chiu, Jai Wei; Yang, Min De; Wu, Chih-Hung

    2013-09-01

    CuZnInSe2 (CZIS) has potential application in solar cell for absorption layer, and give an advantage to change the band gap from CuInSe2 (1.02 eV) to ZnSe (2.67 eV). Using molecular beam epitaxy technology, the CZIS thin films were grown via CuInSe (CIS) and ZnSe base. In the case of CIS, thin films were grown on Mo-coated soda lime glass with various zinc flux. CIS was transformed into chalcopyrite and sphalerite coexisting CZIS easily but it is difficult to transform into the pure sphalerite CZIS. Zn/(Zn+In+Cu) ratio has limited to approximate 36 at% and the excess-Zn played a catalyst role. In the case of ZnSe base, which was grown on GaAs (001), various In and Cu flux defined as the TIn series and TCu series, respectively. There are four types of compound in the TIn series and TCu series, including ZnSe, InxSey, ZnIn2Se4 (ZIS) and CZIS. In the TIn series under the lowest In and Cu flux, selenium (Se) were randomly combined with cations to form the CZIS. When TIn is increased in this moment, the CZIS was transformed into ZIS. In the TCu series, CZIS demonstrated via In-rich ZIS (Zn(In, Cu)Se) and InxSey base ((Zn, Cu)InSe). It is chalcopyrite and sphalerite coexisting structure in the medium TCu region. In the high TCu region, it is transformed into the Zn-poor and Cu-rich CZIS.

  15. Comparative study on the thickness-dependent properties of ITO and GZO thin films grown on glass and PET substrates

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Park, J.-K.; Baik, Y. J.; Kim, W. M.; Jeong, J.; Seong, T.-Y.

    2012-11-01

    The thickness-dependent properties of amorphous Sn-doped In2O3 (ITO) and polycrystalline Ga-doped ZnO (GZO) films grown on polyethylene terephthalate (PET) with a polymeric hard coating were compared with those deposited on Corning glass. The film thickness varied from 20 to 1310 nm. The electrical properties of the ITO films on PET were almost similar to those of the ITO films on glass. On the other hand, GZO films showed slightly poorer electrical properties when deposited on PET, but the difference was marginal. The electrical properties of amorphous ITO films were independent of film thickness, but polycrystalline GZO films exhibited monotonicallyimproving behavior with increasing thickness, mainly due to enhanced crystallinity and increased grain size with increasing film thickness. Although the air-referenced transmittance spectra of films on PET were about 2-3% lower than those on glass due to the lower transmittance of PET, the substrate-referenced optical transmittances of films on PET were higher than those on glass, reflecting the somewhat coarse structure of films on PET. Both the ITO and the GZO films on PET with a polymeric hard coating were shown to yield properties comparable to those oof both films on glass.

  16. A phase-field investigation of domain structures in ferroelectric bismuth ferrite thin films

    NASA Astrophysics Data System (ADS)

    Winchester, Benjamin

    The ferroelectric domain structure of multiferroic BiFeO3 thin films are strongly affected by the electrical boundary conditions. We employ a Ginzburg-Landau- Devonshire phase-field model to investigate the effects of the electrical boundary conditions on domain structure in BiFeO3 thin films. We examine the domain structure under short-circuit and under open-circuit boundary conditions with varying levels of compensation. As the degree of compensation changes, we find a smooth transition between the two types of domain structure. In the open-circuit case, we note small triangular nanodomains at the surface/wall interfaces that may be useful in nanoelectronic applications. The ferroelectric domain structures of epitaxial BiFeO3 thin films on miscut substrates were studied using a phase-field model. The effects of substrate vicinality towards are considered by assuming charge-compensated surface and film/substrate interface. The predicted domain structures show remarkable agreement with existing experimental observations, including domain wall orientations and local topological domain configurations. The roles of elastic, electric, and gradient energies on the domain structures were analyzed. It is shown that the substrate strain anisotropy due to the miscut largely determines the domain variant selection and domain configurations. We employ phase-field modeling to explore the elastic properties of artificiallycreated 1-D domain walls in (001)p-oriented BiFeO3 thin films. The walls are composed of a junction of the four polarization variants, all with the same out-of-plane polarization: a "vortex" is comprised of polarization variants rotating around the junction, and an "anti-vortex" is comprised of two polarization variants pointing towards the junction and two pointing away. It was found that these junctions exhibit peculiarly high electroelastic fields induced by the neighboring ferroelastic/ferroelectric domains. These fields may contribute to the segregation

  17. Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Buršík, J.; Kužel, R.; Knížek, K.; Drbohlav, I.

    2013-07-01

    Thin films of Ba2Zn2Fe12O22 (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO3(1 1 1) (ST) single crystal substrates using epitaxial SrFe12O19 (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature ramp were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and Φ scans reveal perfect parallel in-plane alignment of SrTiO3 substrate and both hexaferrite phases.

  18. Self-generation of bright microwave magnetic envelope soliton trains in ferrite films through frequency filtering

    NASA Astrophysics Data System (ADS)

    Scott, Mark M.; Kalinikos, Boris A.; Patton, Carl E.

    2001-02-01

    Resonant ring feedback with frequency filtering has been used for the self-generation of bright soliton trains. The solitons were produced from magnetostatic backward volume spin waves propagated in an in-plane magnetized magnetic film delay line as part of the resonant ring structure. The amplitude and phase time profiles, together with the power spectra of the self-generated pulses, confirm their bright soliton nature.

  19. Transparent conductive and near-infrared reflective Ga-doped ZnO/Cu bilayer films grown at room temperature

    SciTech Connect

    Lu, J. G.; Bie, X.; Wang, Y. P.; Gong, L.; Ye, Z. Z.

    2011-05-15

    Bilayer films consisting of Ga-doped ZnO (GZO) and Cu layers were grown at room temperature by magnetron sputtering. The structural, electrical, and optical properties of GZO/Cu bilayer films were investigated in detail. The crystallinity and transparent-conductive properties of the films were correlated with the Cu layer thickness. The GZO/Cu bilayer film with the Cu layer thickness of 7.8 nm exhibited a low resistivity of 7.6x10{sup -5} {Omega} cm and an average visible transmittance of 74%. The reflectance was up to 65% in the near-infrared region for this film. The transparent conductive and near-infrared reflective GZO/Cu bilayer films could be readily deposited at room temperature. The GZO/Cu bilayer films were thermally stable when annealed at temperatures as high as 500 deg. C.

  20. Structural and optical characterization of ZrO2 thin films grown on silicon and quartz substrates

    NASA Astrophysics Data System (ADS)

    Hojabri, Alireza

    2016-09-01

    Zirconium oxide thin films were grown successfully by thermal annealing of zirconium thin films deposited on quartz and silicon substrates by direct current magnetron sputtering technique. The structural and optical properties in relation to thermal annealing times were investigated. The X-ray diffraction patterns revealed that structure of films changes from amorphous to crystalline by increase of annealing times in range 60-240 min. The composition of films was determined by Rutherford back scattering spectroscopy. Atomic force microscopy results exhibited that surface morphology and roughness of films depend on the annealing time. The refractive index of the films was calculated using Swanepoel's method. The optical band gap energy of annealed films decreased from 5.50 to 5.34 eV with increasing thermal annealing time.

  1. Low-temperature-grown continuous graphene films from benzene by chemical vapor deposition at ambient pressure.

    PubMed

    Jang, Jisu; Son, Myungwoo; Chung, Sunki; Kim, Kihyeun; Cho, Chunhum; Lee, Byoung Hun; Ham, Moon-Ho

    2015-01-01

    There is significant interest in synthesizing large-area graphene films at low temperatures by chemical vapor deposition (CVD) for nanoelectronic and flexible device applications. However, to date, low-temperature CVD methods have suffered from lower surface coverage because micro-sized graphene flakes are produced. Here, we demonstrate a modified CVD technique for the production of large-area, continuous monolayer graphene films from benzene on Cu at 100-300 °C at ambient pressure. In this method, we extended the graphene growth step in the absence of residual oxidizing species by introducing pumping and purging cycles prior to growth. This led to continuous monolayer graphene films with full surface coverage and excellent quality, which were comparable to those achieved with high-temperature CVD; for example, the surface coverage, transmittance, and carrier mobilities of the graphene grown at 300 °C were 100%, 97.6%, and 1,900-2,500 cm(2) V(-1) s(-1), respectively. In addition, the growth temperature was substantially reduced to as low as 100 °C, which is the lowest temperature reported to date for pristine graphene produced by CVD. Our modified CVD method is expected to allow the direct growth of graphene in device manufacturing processes for practical applications while keeping underlying devices intact. PMID:26658923

  2. Magnetic and structural properties of Co2FeAl thin films grown on Si substrate

    NASA Astrophysics Data System (ADS)

    Belmeguenai, Mohamed; Tuzcuoglu, Hanife; Gabor, Mihai; Petrisor, Traian; Tiusan, Coriolan; Berling, Dominique; Zighem, Fatih; Mourad Chérif, Salim

    2015-01-01

    The correlation between magnetic and structural properties of Co2FeAl (CFA) thin films of different thicknesses (10 nmgrown at room temperature on MgO-buffered Si/SiO2 substrates and annealed at 600 °C has been studied. x-ray diffraction (XRD) measurements revealed an (011) out-of-plane textured growth of the films. The deduced lattice parameter increases with the film thickness. Moreover, pole figures showed no in-plane preferential growth orientation. The magneto-optical Kerr effect hysteresis loops showed the presence of a weak in-plane uniaxial anisotropy with a random easy axis direction. The coercive field, measured with the applied field along the easy axis direction, and the uniaxial anisotropy field increase linearly with the inverse of the CFA thickness. The microstrip line ferromagnetic resonance measurements for in-plane and perpendicular applied magnetic fields revealed that the effective magnetization and the uniaxial in-plane anisotropy field follow a linear variation versus the inverse CFA thickness. This allows deriving a perpendicular surface anisotropy coefficient of -1.86 erg/cm2.

  3. Continuous and nanostructured TiO2 films grown by dc sputtering magnetron.

    PubMed

    Sánchez, O; Vergara, L; Font, A Climent; de Melo, O; Sanz, R; Hernández-Vélez, M

    2012-12-01

    The growth of Anatase nanostructured films using dc reactive magnetron sputtering and post-annealing treatment is reported. TiO2 has been deposited on Porous Anodic Alumina Films used as templates which were previously grown in phosphoric acid solution and etched to modify their pore diameters. This synthesis via results in the formation of vertically aligned and spatially ordered TiO2 nanostructures replicating the underlying template. Previously, the growth optimization of TiO2 thin films deposited by dc magnetron sputtering on flat silicon substrates was done. The crystalline structure and Ti in-depth concentration profile were determined by grazing incidence X-ray diffraction and Rutherford backscattering spectrometry, respectively. The surface morphology of the samples was explored by mean of a Field Emission Gun scanning electron microscope. Optical properties of the nanostructured samples were studied by using the reflectance spectra received in the UV-visible range. In these spectra different band gap values and complex light absorption features were observed. PMID:23447970

  4. Low-temperature-grown continuous graphene films from benzene by chemical vapor deposition at ambient pressure

    PubMed Central

    Jang, Jisu; Son, Myungwoo; Chung, Sunki; Kim, Kihyeun; Cho, Chunhum; Lee, Byoung Hun; Ham, Moon-Ho

    2015-01-01

    There is significant interest in synthesizing large-area graphene films at low temperatures by chemical vapor deposition (CVD) for nanoelectronic and flexible device applications. However, to date, low-temperature CVD methods have suffered from lower surface coverage because micro-sized graphene flakes are produced. Here, we demonstrate a modified CVD technique for the production of large-area, continuous monolayer graphene films from benzene on Cu at 100–300 °C at ambient pressure. In this method, we extended the graphene growth step in the absence of residual oxidizing species by introducing pumping and purging cycles prior to growth. This led to continuous monolayer graphene films with full surface coverage and excellent quality, which were comparable to those achieved with high-temperature CVD; for example, the surface coverage, transmittance, and carrier mobilities of the graphene grown at 300 °C were 100%, 97.6%, and 1,900–2,500 cm2 V−1 s−1, respectively. In addition, the growth temperature was substantially reduced to as low as 100 °C, which is the lowest temperature reported to date for pristine graphene produced by CVD. Our modified CVD method is expected to allow the direct growth of graphene in device manufacturing processes for practical applications while keeping underlying devices intact. PMID:26658923

  5. A kinetic model for stress generation in thin films grown from energetic vapor fluxes

    NASA Astrophysics Data System (ADS)

    Chason, E.; Karlson, M.; Colin, J. J.; Magnfält, D.; Sarakinos, K.; Abadias, G.

    2016-04-01

    We have developed a kinetic model for residual stress generation in thin films grown from energetic vapor fluxes, encountered, e.g., during sputter deposition. The new analytical model considers sub-surface point defects created by atomic peening, along with processes treated in already existing stress models for non-energetic deposition, i.e., thermally activated diffusion processes at the surface and the grain boundary. According to the new model, ballistically induced sub-surface defects can get incorporated as excess atoms at the grain boundary, remain trapped in the bulk, or annihilate at the free surface, resulting in a complex dependence of the steady-state stress on the grain size, the growth rate, as well as the energetics of the incoming particle flux. We compare calculations from the model with in situ stress measurements performed on a series of Mo films sputter-deposited at different conditions and having different grain sizes. The model is able to reproduce the observed increase of compressive stress with increasing growth rate, behavior that is the opposite of what is typically seen under non-energetic growth conditions. On a grander scale, this study is a step towards obtaining a comprehensive understanding of stress generation and evolution in vapor deposited polycrystalline thin films.

  6. Growth Parameters for Thin Film InBi Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Keen, B.; Makin, R.; Stampe, P. A.; Kennedy, R. J.; Sallis, S.; Piper, L. J.; McCombe, B.; Durbin, S. M.

    2014-04-01

    The alloying of bismuth with III-V semiconductors, in particular GaAs and InAs thin films grown by molecular beam epitaxy (MBE), has attracted considerable interest due to the accompanying changes in band structure and lattice constant. Specifically, bismuth incorporation in these compounds results in both a reduction in band gap (through shifting of the valence band) and an increase in the lattice constant of the alloy. To fully understand the composition of these alloys, a better understanding of the binary endpoints is needed. At present, a limited amount of literature exists on the III-Bi family of materials, most of which is theoretical work based on density functional theory calculations. The only III-Bi material known to exist (in bulk crystal form) is InBi, but its electrical properties have not been sufficiently studied and, to date, the material has not been fabricated as a thin film. We have successfully deposited crystalline InBi on (100) GaAs substrates using MBE. Wetting of the substrate is poor, and regions of varying composition exist across the substrate. To obtain InBi, the growth temperature had to be below 100 °C. It was found that film crystallinity improved with reduced Bi flux, into an In-rich regime. Additionally, attempts were made to grow AlBi and GaBi.

  7. Low-temperature-grown continuous graphene films from benzene by chemical vapor deposition at ambient pressure

    NASA Astrophysics Data System (ADS)

    Jang, Jisu; Son, Myungwoo; Chung, Sunki; Kim, Kihyeun; Cho, Chunhum; Lee, Byoung Hun; Ham, Moon-Ho

    2015-12-01

    There is significant interest in synthesizing large-area graphene films at low temperatures by chemical vapor deposition (CVD) for nanoelectronic and flexible device applications. However, to date, low-temperature CVD methods have suffered from lower surface coverage because micro-sized graphene flakes are produced. Here, we demonstrate a modified CVD technique for the production of large-area, continuous monolayer graphene films from benzene on Cu at 100-300 °C at ambient pressure. In this method, we extended the graphene growth step in the absence of residual oxidizing species by introducing pumping and purging cycles prior to growth. This led to continuous monolayer graphene films with full surface coverage and excellent quality, which were comparable to those achieved with high-temperature CVD; for example, the surface coverage, transmittance, and carrier mobilities of the graphene grown at 300 °C were 100%, 97.6%, and 1,900-2,500 cm2 V-1 s-1, respectively. In addition, the growth temperature was substantially reduced to as low as 100 °C, which is the lowest temperature reported to date for pristine graphene produced by CVD. Our modified CVD method is expected to allow the direct growth of graphene in device manufacturing processes for practical applications while keeping underlying devices intact.

  8. Surface structure analysis of BaSi2(100) epitaxial film grown on Si(111) using CAICISS

    NASA Astrophysics Data System (ADS)

    Okasaka, Shouta; Kubo, Osamu; Tamba, Daiki; Ohashi, Tomohiro; Tabata, Hiroshi; Katayama, Mitsuhiro

    2015-05-01

    Geometry and surface structure of a BaSi2(100) film on Si(111) formed by reactive deposition epitaxy (RDE) have been investigated using coaxial impact-collision ion scattering spectroscopy and atomic force microscopy. BaSi2(100) film can be grown only when the Ba deposition rate is sufficiently fast. It is revealed that a BaSi2(100) film grown at 600 °C has better crystallinity than a film grown at 750 °C owing to the mixture of planes other than (100) in the RDE process at higher temperatures. The azimuth angle dependence of the scattering intensity from Ba shows sixfold symmetry, indicating that the minimum height of surface steps on BaSi2(100) is half of the length of unit cell. By comparing the simulated azimuth angle dependences for more than ten surface models with experimental one, it is strongly indicated that the surface of a BaSi2(100) film grown on Si(111) is terminated by Si tetrahedra.

  9. Regular and chaotic dynamics of magnetization precession in ferrite-garnet films

    NASA Astrophysics Data System (ADS)

    Shutyĭ, Anatoliy M.; Sementsov, Dmitriy I.

    2009-03-01

    By numerically solving equations of motion and constructing the spectrum of Lyapunov exponents, nonlinear dynamics of uniformly precessing magnetization in (110) thin film structures with perpendicular magnetic bias is investigated over a wide frequency range of the alternating field. Bifurcational changes in magnetization precession and the states of dynamical bistability are discovered. Conditions for the realization of high-amplitude regular and chaotic dynamic regimes are revealed. The possibility of controlling those precession regimes by using external magnetic fields is shown. The features of time analogs of the Poincaré section of trajectories in the chaotic regimes are studied.

  10. Synthesis and characterization of hexagonal ferrite Sr1.8Sm0.2Co2Ni1.50Fe10.50O22/PST thin films for high frequency application

    NASA Astrophysics Data System (ADS)

    Ali, Irshad; Islam, M. U.; Ashiq, Muhammad Naeem; Asif Iqbal, M.; Karamat, Nazia; Azhar Khan, M.; Sadiq, Imran; Ijaz, Sana; Shakir, Imran

    2015-11-01

    Y-type hexagonal ferrite (Sr1.8Sm0.2Co2Ni1.50 Fe10.50O22) was prepared by a normal microemulsion route. The ferrite/polymer composites thin films are formed at different ferrite ratios in pure polystyrene matrix. The X-ray diffraction analysis shows broad peak at low angles which is due to the PST and the peaks for Y-type ferrite are also observed in composite samples. The peaks become more intense and show less broadening with increasing concentration of ferrite which suggests that crystallinity is improved with the addition of ferrite. DC resistivity of the composites samples is lower than that of the pure PST and decreases by increasing ferrite filler into the polymer. This decrease of resistivity is mainly due to the addition of comparatively less resistive ferrite into the highly insulating polymer matrix of PST. The observed increase in the dielectric constant (permittivity) with increasing concentration ratio of ferrites is mainly due to the electron exchange between Fe2+↔Fe3++e- which consequently results in enhancement of electric polarization as well as dielectric constant. The existence of resonances peaks in the dielectric loss tangent spectra is due to the fact when the external applied frequency becomes equal to the jumping frequency of electrons between Fe2+ and Fe3+. The increasing behavior of the dielectric constant, dielectric loss and AC conductivity with increasing ferrite ratio in PST matrix proposes their versatile use in different technological applications especially for electromagnetic shielding.

  11. Structural and Magnetic Phase Transitions in Manganese Arsenide Thin-Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Jaeckel, Felix Till

    Phase transitions play an important role in many fields of physics and engineering, and their study in bulk materials has a long tradition. Many of the experimental techniques involve measurements of thermodynamically extensive parameters. With the increasing technological importance of thin-film technology there is a pressing need to find new ways to study phase transitions at smaller length-scales, where the traditional methods are insufficient. In this regard, the phase transitions observed in thin-films of MnAs present interesting challenges. As a ferromagnetic material that can be grown epitaxially on a variety of technologically important substrates, MnAs is an interesting material for spintronics applications. In the bulk, the first order transition from the low temperature ferromagnetic alpha-phase to the beta-phase occurs at 313 K. The magnetic state of the beta-phase has remained controversial. A second order transition to the paramagnetic gamma-phase takes place at 398 K. In thin-films, the anisotropic strain imposed by the substrate leads to the interesting phenomenon of coexistence of alpha- and beta-phases in a regular array of stripes over an extended temperature range. In this dissertation these phase transitions are studied in films grown by molecular beam epitaxy on GaAs (001). The films are confirmed to be of high structural quality and almost purely in the A0 orientation. A diverse set of experimental techniques, germane to thin-film technology, is used to probe the properties of the film: Temperature-dependent X-ray diffraction and atomic-force microscopy (AFM), as well as magnetotransport give insights into the structural properties, while the anomalous Hall effect is used as a probe of magnetization during the phase transition. In addition, reflectance difference spectroscopy (RDS) is used as a sensitive probe of electronic structure. Inductively coupled plasma etching with BCl3 is demonstrated to be effective for patterning MnAs. We show

  12. As-grown Y-Ba-Cu-O thin films by reactive coevaporation with oxygen plasma cooling

    NASA Astrophysics Data System (ADS)

    Matsumoto, M.; Akoh, H.; Takada, S.

    1989-10-01

    We have developed a new fabrication process of as-grown Y-Ba-Cu-O thin films using a reactive coevaporation method specially with the rf-plasma cooling in the low oxygen pressure of 0.4 mTorr. By this O2 plasma cooling process, the transition temperature Tc is improved from 40 to 81 K for the film with a thickness of 1000 Å. The x-ray diffraction analysis shows that the activated oxygen species generated by the rf plasma make Y-Ba-Cu-O films oxidize sufficiently even in the low pressure of oxygen. In addition, we have studied the thickness dependence of Tc for as-grown films with various thicknesses of 60-2000 Å.

  13. As-grown Y-Ba-Cu-O thin films by reactive coevaporation with oxygen plasma cooling

    SciTech Connect

    Matsumoto, M.; Akoh, H.; Takada, S. )

    1989-10-15

    We have developed a new fabrication process of as-grown Y-Ba-Cu-O thin films using a reactive coevaporation method specially with the rf-plasma cooling in the low oxygen pressure of 0.4 mTorr. By this O{sub 2} plasma cooling process, the transition temperature {ital T}{sub {ital c}} is improved from 40 to 81 K for the film with a thickness of 1000 A. The x-ray diffraction analysis shows that the activated oxygen species generated by the rf plasma make Y-Ba-Cu-O films oxidize sufficiently even in the low pressure of oxygen. In addition, we have studied the thickness dependence of {ital T}{sub {ital c}} for as-grown films with various thicknesses of 60--2000 A.

  14. Ordered 1,6-bis(2-hydroxyphenyl) pyridine boron complex films grown on Ag(110): From submonolayer to multilayer

    SciTech Connect

    Zhong, D.Y.; Lin, F.; Fuchs, H.; Chi, L.F.; Wang, Y.

    2005-03-15

    Ordered molecular films of a blue-light-emitting material, 1,6-bis(2-hydroxyphenyl) pyridine boron complex [(dppy)BF], grown on the Ag(110) surface by means of organic molecular beam epitaxy, were investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) under an ultrahigh vacuum. Two commensurate structures exist in the monolayer film grown at 300 K, as found by STM. In the monolayer film, two types of hydrogen bonds are formed between the molecules, which, in addition to the molecule-substrate interaction, essentially determine the monolayer structures. The structural evolution of the (dppy)BF films from submonolayer to three monolayers was monitored by LEED in situ and in real time. The results indicate that the growth of the first two monolayers is affected by the periodic potential on the substrate surface, while such a template effect is weakened beyond the second monolayer.

  15. Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Li, Bin; Zhang, Qin-Jian; Shi, Yan-Chao; Li, Jia-Jun; Li, Hong; Lu, Fan-Xiu; Chen, Guang-Chao

    2014-08-01

    A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

  16. Enhanced Carrier Generation in Nb-Doped SnO2 Thin Films Grown on Strain-Inducing Substrates

    NASA Astrophysics Data System (ADS)

    Nakao, Shoichiro; Yamada, Naoomi; Hirose, Yasushi; Hasegawa, Tetsuya

    2012-06-01

    We report the effect of lattice strain from the substrate on carrier generation in Nb-doped SnO2 (NTO) transparent conductive oxide (TCO) thin films. The carrier activation efficiency of Nb was strongly affected by in-plane tensile strain, and the NTO films grown on c-Al2O3 and anatase TiO2 seed layers had carrier density (ne) as high as 3×1020 cm-3. In contrast, strain-free NTO films grown on glass exhibited much smaller ne due to the formation of deep impurity levels. These results imply that NTO has potential as a practical TCO in the presence of substrate-film epitaxial interaction.

  17. Ultrafast structural dynamics of LaVO3 thin films grown by hybrid molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Brahlek, Matthew; Lapano, Jason; Stoica, Vladimir; Zhang, Lei; Zhang, Hai-Tian; Akamatsu, Hirofumi; Eaton, Craig; Gopalan, Venkatraman; Freeland, John; Wen, Haidan; Engel-Herbert, Roman

    LaVO3, with a partially full d-shell is expected to be metallic, but due to electron-electron interactions a gap emerges and the ground state is a Mott insulator. Such effects are a strong function of the bonding geometry, and particularly the V-O-V bond angle. Controlling these structural effects on the ultrafast time scale can lead to control over the underlying electronic ground state. Here we report the ultrafast structural dynamics of 25 and 50 nm thick LaVO3 thin films grown by the hybrid molecular beam epitaxy technique on SrTiO3 when excited across the bandgap by 800 nm light. Using time-resolved x-ray diffraction on the 100 ps time scale at Sector 7 of the Advanced Photon Source, we directly measured the structural changes with atomic accuracy by monitoring integer Bragg diffraction peaks and find a large out-of-plane strain of 0.18% upon optical excitation; the recovery time is ~1 ns for the 25 nm film and ~2 ns for the 50 nm film, consistent with the thermal transport from the film to the substrate. Further, we will discuss the response of the oxygen octahedral rotation patterns indicated by changes of the half-order diffraction peaks. Understanding such ultrafast structural deformation is important for optimizing optical excitations to create new metastable phases starting from a Mott insulator. This work was supported by the Department of Energy under Grant DE-SC0012375, and DE-AC02-06CH11357.

  18. Hardness and Young's modulus of high-quality cubic boron nitride films grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jiang, X.; Philip, J.; Zhang, W. J.; Hess, P.; Matsumoto, S.

    2003-02-01

    The elastic and mechanical properties of high-quality cubic boron nitride (cBN) films with a few microns thickness and submicron grain size grown on silicon substrates by chemical vapor deposition were determined by measuring the dispersion of surface acoustic waves propagating along the surface of the layered system. The values are compared with those obtained with an ultralow load indenter (Triboscope). Specifically, the hardness, Young's modulus and density of the film were measured.

  19. Biomass yield and composition of sweetpotato grown in a nutrient film technique system.

    PubMed

    Almazan, A M; Zhou, X

    1997-01-01

    Sweetpotato cultivar TU-82-155 grown in a nutrient film technique system and separated into foliage, tips, fibrous, string and storage roots at harvest had a total dry biomass of 89.9 g per plant with 38.4% inedible portion. Tips and storage roots, the traditional edible parts, were analyzed for dry matter, protein, fat, ash, minerals (Ca, Fe, K, Mg, Na, Zn), vitamins (carotene, ascorbic acid, thiamin), oxalic and tannic acids, and trypsin and chymotrypsin inhibitors to determine their nutritional quality. Water soluble matter, minerals (Ca, Fe, K, Mg, Na, Zn), cellulose, hemicellulose and lignin concentrations in the edible and inedible parts were obtained to provide information needed for the selection of appropriate bioconversion processes of plant wastes into food or forms suitable for crop production in a controlled biological life support system. PMID:9373876

  20. High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy

    SciTech Connect

    Miyashita, Naoya; Ahsan, Nazmul; Monirul Islam, Muhammad; Okada, Yoshitaka; Inagaki, Makoto; Yamaguchi, Masafumi

    2012-11-26

    We report the highest mobility values above 2000 cm{sup 2}/Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.

  1. Epitaxially grown polycrystalline silicon thin-film solar cells on solid-phase crystallised seed layers

    NASA Astrophysics Data System (ADS)

    Li, Wei; Varlamov, Sergey; Xue, Chaowei

    2014-09-01

    This paper presents the fabrication of poly-Si thin film solar cells on glass substrates using seed layer approach. The solid-phase crystallised P-doped seed layer is not only used as the crystalline template for the epitaxial growth but also as the emitter for the solar cell structure. This paper investigates two important factors, surface cleaning and intragrain defects elimination for the seed layer, which can greatly influence the epitaxial grown solar cell performance. Shorter incubation and crystallisation time is observed using a simplified RCA cleaning than the other two wet chemical cleaning methods, indicating a cleaner seed layer surface is achieved. Cross sectional transmission microscope images confirm a crystallographic transferal of information from the simplified RCA cleaned seed layer into the epi-layer. RTA for the SPC seed layer can effectively eliminate the intragrain defects in the seed layer and improve structural quality of both of the seed layer and the epi-layer. Consequently, epitaxial grown poly-Si solar cell on the RTA treated seed layer shows better solar cell efficiency, Voc and Jsc than the one on the seed layer without RTA treatment.

  2. Characterization of Epitaxial Film Silicon Solar Cells Grown on Seeded Display Glass: Preprint

    SciTech Connect

    Young, D. L.; Grover, S.; Teplin, C.; Stradins, P.; LaSalvia, V.; Chuang, T. K.; Couillard, J. G.; Branz, H. M.

    2012-06-01

    We report characterizations of epitaxial film crystal silicon (c-Si) solar cells with open-circuit voltages (Voc) above 560 mV. The 2-um absorber cells are grown by low-temperature (<750 degrees C) hot-wire CVD (HWCVD) on Corning EAGLE XG display glass coated with a layer-transferred (LT) Si seed. The high Voc is a result of low-defect epitaxial Si (epi-Si) growth and effective hydrogen passivation of defects. The quality of HWCVD epitaxial growth on seeded glass substrates depends on the crystallographic quality of the seed and the morphology of the epitaxial growth surface. Heterojunction devices consist of glass/c-Si LT seed/ epi n+ Si:P/epi n- Si:P/intrinsic a-Si:H/p+ a-Si:H/ITO. Similar devices grown on electronically 'dead' n+ wafers have given Voc {approx}630 mV and {approx}8% efficiency with no light trapping features. Here we study the effects of the seed surface polish on epi-Si quality, how hydrogenation influences the device character, and the dominant junction transport physics.

  3. Highly Crystalline CVD-grown Multilayer MoSe2 Thin Film Transistor for Fast Photodetector

    PubMed Central

    Jung, Chulseung; Kim, Seung Min; Moon, Hyunseong; Han, Gyuchull; Kwon, Junyeon; Hong, Young Ki; Omkaram, Inturu; Yoon, Youngki; Kim, Sunkook; Park, Jozeph

    2015-01-01

    Hexagonal molybdenum diselenide (MoSe2) multilayers were grown by chemical vapor deposition (CVD). A relatively high pressure (>760 Torr) was used during the CVD growth to achieve multilayers by creating multiple nuclei based on the two-dimensional crystal growth model. Our CVD-grown multilayer MoSe2 thin-film transistors (TFTs) show p-type-dominant ambipolar behaviors, which are attributed to the formation of Se vacancies generated at the decomposition temperature (650 °C) after the CVD growth for 10 min. Our MoSe2 TFT with a reasonably high field-effect mobility (10 cm2/V · s) exhibits a high photoresponsivity (93.7 A/W) and a fast photoresponse time (τrise ~ 0.4 s) under the illumination of light, which demonstrates the practical feasibility of multilayer MoSe2 TFTs for photodetector applications. PMID:26477744

  4. Properties of MgB2 films grown at various temperatures by hybrid physical chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Veldhorst, Menno; Lee, Che-Hui; Lamborn, Daniel R.; DeFrain, Raymond; Redwing, Joan M.; Li, Qi; Xi, X. X.

    2008-09-01

    A hybrid physical-chemical vapour deposition (HPCVD) system consisting of separately controlled Mg-source heater and substrate heater is used to grow MgB2 thin films and thick films at various temperatures. We are able to grow superconducting MgB2 thin films at temperatures as low as 350 °C with a Tc0 of 35.5 K. MgB2 films up to 4 µm in thickness grown at 550 °C have Jc over 106 A cm-2 at 5 K and zero applied field. The low deposition temperature of MgB2 films is desirable for all-MgB2 tunnel junctions and MgB2 thick films are important for applications in coated conductors.

  5. Synthesis of nanocrystalline Cu2ZnSnS4 thin films grown by the spray-pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Chandel, Tarun; Singh, Joginder; Rajaram, P.

    2015-08-01

    Spray pyrolysis was used to deposit Cu2ZnSnS4 (CZTS) thin films on soda lime glass substrates at 300 °C. Aqueous solutions of copper chloride, zinc chloride, stannous chloride and thiourea were mixed together to form the spray liquid. The sprayed films were annealed under vacuum at 350 °C, 400 °C and 450 °C. Structural and optical characterization was performed on the CZTS films using X-ray diffraction (XRD) and UV-VIS spectrophotometry. XRD results indicate that the films are single phase nanocrystalline CZTS. Optical studies show that the optical gap values are 1.44 eV for the as-grown film and 1.46 eV, 1.48 eV and 1.49 eV for the films annealed at 350 °C, 400 °C and 450 °C, respectively.

  6. Reversible Change in Electrical and Optical Properties in Epitaxially Grown Al-Doped ZnO Thin Films

    SciTech Connect

    Noh, J. H.; Jung, H. S.; Lee, J. K.; Kim, J. Y; Cho, C. M.; An, J.; Hong, K. S.

    2008-01-01

    Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01 x 10{sup -4} {Omega} cm. However, after annealing at 450 C in air, the electrical resistivity of the AZO films increased to 1.97 x 10{sup -1} {Omega} cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H{sub 2} recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H{sub 2} annealing. A photoluminescence study showed that oxygen interstitial (O{sub i}) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films.

  7. Interface properties and reliability of ultrathin oxynitride films grown on strained Si1-xGex substrates

    NASA Astrophysics Data System (ADS)

    Samanta, S. K.; Chatterjee, S.; Maikap, S.; Bera, L. K.; Banerjee, H. D.; Maiti, C. K.

    2003-03-01

    The role of nitrogen in improving the interface properties and the reliability of oxynitride/SiGe interfaces and the dielectric properties of oxynitride films has been studied using constraint theory. Ultrathin (<3 nm) oxynitride films were grown using N2O followed by N2 annealing on strained Si0.82Ge0.18 layers. Silicon dioxide films grown on strained Si0.82Ge0.18 layers were also nitrided in N2O by rapid thermal processing. The nitrogen distribution in the oxynitride films was investigated by time-of-flight secondary ion mass spectrometry. The interface state density, charge trapping properties, and interface state generation with constant current and voltage stressing were studied. It is observed that dielectric films grown in N2O ambient and subsequently annealed in N2 have excellent electrical properties. A low stress-induced leakage current and a high time dependent dielectric breakdown are also observed in these films. Improvements in the electrical properties are shown to be due to the creation of a large number of strong Si-N bonds both in bulk and in the SiON-Si1-xGex interface region of the dielectric.

  8. The finite size effect on the metal-insulator transition of MOCVD grown VO{sub 2} films

    SciTech Connect

    Kim, Hyung Kook; Chiarello, R.P.; You, Hoydoo; Chang, M.H.L.; Zhang, T.J.; Lam, D.J.

    1991-11-01

    We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO{sub 2} films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO{sub 2} films with out-of-plane particle size ranging from 60--310 {Angstrom}. Each Vo{sub 2} film was grown on a thin TiO{sub 2} buffer layer, which in turn was grown by MOCVD on a polished sapphire (112) substrate. The transition was found to be first order. As the out-of-plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60{Angstrom} film the transition was observed at {approximately}61{degrees}C with a transition width if {approximately}10{degrees}C, while for the 310{Angstrom} film the transition temperature was {approximately}59{degrees}C and the transition width {approximately} 2{degree}C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.

  9. The finite size effect on the metal-insulator transition of MOCVD grown VO sub 2 films

    SciTech Connect

    Kim, Hyung Kook; Chiarello, R.P.; You, Hoydoo; Chang, M.H.L.; Zhang, T.J.; Lam, D.J.

    1991-11-01

    We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO{sub 2} films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO{sub 2} films with out-of-plane particle size ranging from 60--310 {Angstrom}. Each Vo{sub 2} film was grown on a thin TiO{sub 2} buffer layer, which in turn was grown by MOCVD on a polished sapphire (112) substrate. The transition was found to be first order. As the out-of-plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60{Angstrom} film the transition was observed at {approximately}61{degrees}C with a transition width if {approximately}10{degrees}C, while for the 310{Angstrom} film the transition temperature was {approximately}59{degrees}C and the transition width {approximately} 2{degree}C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.

  10. Composition and Bonding in Amorphous Carbon Films Grown by Ion Beam Assisted Deposition: Influence of the Assistance Voltage

    SciTech Connect

    Albella, J.M.; Banks, J.C.; Climent-Font, A.; Doyle, B.L.; Gago, R.; Jimenez, I.; Terminello, L.J.

    1998-11-12

    Amorphous carbon films have been grown by evaporation of graphite with concurrent Ar+ ions bombardment assistance. The ion energy has been varied between 0-800 V while keeping a constant ion to carbon atom arrival ratio. Film composition and density were determined by ion scattering techniques (RBS and ERDA), indicating a negligible hydrogen content and a density dependence with the assistance voltage. The bonding structure of the films has been studied by Raman and X-ray Absorption Near-Edge (XANES) spectroscopy. Different qualitative effects have been found depending on the ion energy range. For ion energies below 300 eV, there is a densification of the carbon layer due to the increase in the sp3 content. For ion energies above 300 eV sputtering phenomena dominate over densification, and thinner films are found with increasing assistance voltage until no film is grown over 600 V. The films with the highest SP3 content are grown with intermediate energies between 200-300 V.

  11. Characteristics of Fluorine-doped tin oxide thin films grown by Streaming process for Electrodeless Electrochemical Deposition

    NASA Astrophysics Data System (ADS)

    Yusuf, Gbadebo; Khalilzadeh-Rezaie, Farnood; Cleary, Justin W.; Oladeji, Isaiah O.; Suu, Koukou; Schoenfeld, Winston V.; Peale, Robert E.; Awodugba, Ayodeji O.

    2015-04-01

    This work investigated the characteristics of SnO2: F films grown by Streaming Process for Electrodeless Electrochemical Deposition (SPEED). Stannic chloride (SnCl4) and ammonium fluoride (NH4 F) was dissolved in a mixture of deionized water and organic solvents. The preheated substrate temperature was varied between 450 and 530° C. High quality SnO2: F films were grown at all the substrate temperatures studied. The typical film thickness was 250 nm. XRD shows that the grown films are polycrystalline SnO2 with a tetragonal crystal structure. The average optical transmission of the films was around 93% throughout the wavelength of 400 to 1000 nm. The lowest electrical resistivity achieved was 6 x 10-4 Ω cm. The Hall measurements showed that the film is an n-type semiconductor, with the highest carrier mobility of 8.3 cm2/V.s, and concentration of 1 x 1021 cm-3. The direct band gap was determined to be 4 eV from the transmittance spectrum.

  12. Combined effects of bilayer structure and ion substitutions on bismuth ferrite thin films

    NASA Astrophysics Data System (ADS)

    Wu, Jiagang; Wang, John; Xiao, Dingquan; Zhu, Jianguo

    2011-04-01

    To understanding the combined effects of bilayer structure and ion substitutions on electrical behavior of BiFeO3 thin films, the Bi0.90La0.10Fe0.90Zn0.10O3/Bi0.90La0.10Fe0.90Sn0.10O3 bilayers with different thickness ratios were fabricated on SrRuO3/Pt/TiO2/SiO2/Si(100) substrates by radio frequency sputtering. Their dielectric constant increases and the fatigue endurance becomes better with increasing Bi0.90La0.10Fe0.90Zn0.10O3 thickness ratios. The bilayer with the thickness ratio of 210: 90 exhibits a high remanent polarization, and a better fatigue behavior is induced by higher driving electric fields and frequencies.

  13. Electric control of magnon frequencies and magnetic moment of bismuth ferrite thin films at room temperature

    PubMed Central

    Kumar, Ashok; Scott, J. F.; Katiyar, R. S.

    2011-01-01

    Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu∕cm3 at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO3 (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (−E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10−12 sm−1. PMID:21901050

  14. Comparison of stress states in GaN films grown on different substrates: Langasite, sapphire and silicon

    NASA Astrophysics Data System (ADS)

    Park, Byung-Guon; Saravana Kumar, R.; Moon, Mee-Lim; Kim, Moon-Deock; Kang, Tae-Won; Yang, Woo-Chul; Kim, Song-Gang

    2015-09-01

    We demonstrate the evolution of GaN films on novel langasite (LGS) substrate by plasma-assisted molecular beam epitaxy, and assessed the quality of grown GaN film by comparing the experimental results obtained using LGS, sapphire and silicon (Si) substrates. To study the substrate effect, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectra were used to characterize the microstructure and stress states in GaN films. Wet etching of GaN films in KOH solution revealed that the films deposited on GaN/LGS, AlN/sapphire and AlN/Si substrates possess Ga-polarity, while the film deposited on GaN/sapphire possess N-polarity. XRD, Raman and PL analysis demonstrated that a compressive stress exist in the films grown on GaN/LGS, AlN/sapphire, and GaN/sapphire substrates, while a tensile stress appears on AlN/Si substrate. Comparative analysis showed the growth of nearly stress-free GaN films on LGS substrate due to the very small lattice mismatch (~3.2%) and thermal expansion coefficient difference (~7.5%). The results presented here will hopefully provide a new framework for the further development of high performance III-nitride-related devices using GaN/LGS heteroepitaxy.

  15. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    SciTech Connect

    Kushvaha, S. S. Pal, P.; Shukla, A. K.; Joshi, Amish G.; Gupta, Govind; Kumar, M.; Singh, S.; Gupta, Bipin K.; Haranath, D.

    2014-02-15

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm thick GaN epi-layer on sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 10{sup 8} cm{sup −2} at 750 °C) than that of the low temperature grown sample (1.1 × 10{sup 9} cm{sup −2} at 730 °C). A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  16. Comparative study of ITO and FTO thin films grown by spray pyrolysis

    SciTech Connect

    Ait Aouaj, M.; Diaz, R.; Belayachi, A.; Rueda, F.; Abd-Lefdil, M.

    2009-07-01

    Tin doped indium oxide (ITO) and fluorine doped tin oxide (FTO) thin films have been prepared by one step spray pyrolysis. Both film types grown at 400 deg. C present a single phase, ITO has cubic structure and preferred orientation (4 0 0) while FTO exhibits a tetragonal structure. Scanning electron micrographs showed homogeneous surfaces with average grain size around 257 and 190 nm for ITO and FTO respectively. The optical properties have been studied in several ITO and FTO samples by transmittance and reflectance measurements. The transmittance in the visible zone is higher in ITO than in FTO layers with a comparable thickness, while the reflectance in the infrared zone is higher in FTO in comparison with ITO. The best electrical resistivity values, deduced from optical measurements, were 8 x 10{sup -4} and 6 x 10{sup -4} {Omega} cm for ITO (6% of Sn) and FTO (2.5% of F) respectively. The figure of merit reached a maximum value of 2.15 x 10{sup -3} {Omega}{sup -1} for ITO higher than 0.55 x 10{sup -3} {Omega}{sup -1} for FTO.

  17. Low temperature electron transport in phosphorus-doped ZnO films grown on Si substrates

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Hao, M. R.; Guo, W.; Heeg, T.; Schlom, D. G.; Shen, W. Z.; Pan, X. Q.

    2012-07-01

    Low temperature magneto-transport properties and electron dephasing mechanisms of phosphorus-doped ZnO thin films grown on (1 1 1) Si substrates with Lu2O3 buffer layers using pulsed laser deposition were investigated in detail by quantum interference and weak localization theories under magnetic fields up to 10 T. The dephasing length follows the temperature dependence with an index p≈1.6 at higher temperatures indicating electron-electron interaction, yet becomes saturated at lower temperatures. Consistent with photoluminescence measurements and the multi-band simulation of the electron concentration, such behavior was associated with the dislocation densities obtained from x-ray diffraction and mobility fittings, where charged edge dislocations acting as inelastic Coulomb scattering centers were affirmed responsible for electron dephasing. Owing to the temperature independence of the dislocation density, the phosphorus-doped ZnO film maintained a Hall mobility of 4.5 cm2 V-1 s-1 at 4 K.

  18. Anisotropic properties of molecular beam epitaxy-grown colossal magnetoresistance manganite thin films

    SciTech Connect

    ODonnell, J.; Onellion, M.; Rzchowski, M.S.; Eckstein, J.N.; Bozovic, I.

    1997-04-01

    We show that both the magnetoresistance and magnetism in tetragonal MBE-grown films of La{sub 1{minus}x}Ca{sub x}MnO{sub 3} show anisotropic effects that depend on both temperature and magnetic field. We show that the {open_quotes}colossal{close_quotes} magnetoresistance depends on the angle between the magnetization and the transport current and that the size of this effect is temperature-dependent. Below the Curie temperature this results in an unusual upturn in the magnetoresistance for small magnetic fields normal to the plane of the film as the magnetization rotates out of the plane. Low-field hysteresis of the in-plane magnetoresistance is also observed, and also shows an anisotropy with respect to the current and magnetization directions. We also find an in-plane biaxial magnetocrystalline anisotropy with easy axes along the {l_brace}100{r_brace} (Mn{endash}O) crystal directions, and evidence for {ital c}-axis magnetocrystalline anisotropy. {copyright} {ital 1997 American Institute of Physics.}

  19. The annealing effects of V-doped GaN thin films grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Souissi, M.; Bouzidi, M.; El Jani, B.

    2012-02-01

    We have investigated the annealing effect of V-doped GaN (GaN:V) epitaxial layers grown on sapphire by metal organic chemical vapor deposition (MOCVD). The film was annealed at a temperature of 1075 °C for 30 min in N 2 ambient after growth. The structural, surface morphology and optical properties of GaN:V films were studied by high resolution X-ray diffraction (HRXRD), atomic force microscope (AFM) and photoluminescence (PL). The results show that the annealing makes for the destruction in the crystal quality and surface morphology. After thermal annealing, the photoluminescence (PL) measurement showed a reduction of the blue luminescence (BL) band observed in GaN:V at room temperature (RT). The phenomenon is attributed to vanadium diffusion or to the V-related complex dissociation. Near-band-edge (NBE) peak exhibited a red shift after 1075 °C anneal. This is due to the decrease in the level of strain. In the infrared region, we observed the emergence of the line 0.93 eV accompanied by a decrease in the intensity of the 0.82 eV emission. Their possible origins are discussed.

  20. Low-temperature, vapor-liquid-solid, laterally grown silicon films using alloyed catalysts

    NASA Astrophysics Data System (ADS)

    LeBoeuf, Jerome L.; Brodusch, Nicolas; Gauvin, Raynald; Quitoriano, Nathaniel J.

    2014-12-01

    Using amorphous oxide templates known as micro-crucibles which confine a vapor-liquid-solid catalyst to a specific geometry, two-dimensional silicon thin-films of a single orientation have been grown laterally over an amorphous substrate and defects within crystals have been necked out. The vapor-liquid-solid catalysts consisted nominally of 99% gold with 1% titanium, chromium, or aluminum, and each alloy affected the processing of micro-crucibles and growth within them significantly. It was found that chromium additions inhibited the catalytic effect of the gold catalysts, titanium changed the morphology of the catalyst during processing and aluminum stabilized a potential third phase in the gold-silicon system upon cooling. Two mechanisms for growing undesired nanowires were identified both of which hindered the VLS film growth, fast silane cracking rates and poor gold etching, which left gold nanoparticles near the gold-vapor interface. To reduce the silane cracking rates, growth was done at a lower temperature while an engineered heat and deposition profile helped to reduce NWs caused by the second mechanism. Through experimenting with catalyst compositions, the fundamental mechanisms which produce concentration gradients across the gold-silicon alloy within a given micro-crucible have been proposed. Using the postulated mechanisms, micro-crucibles were designed which promote high-quality, single crystal growth of semiconductors.

  1. Effect of residual stress on the microstructure of GaN epitaxial films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Wang, Haiyan; Wang, Wenliang; Yang, Weijia; Zhu, Yunnong; Lin, Zhiting; Li, Guoqiang

    2016-04-01

    The stress-free GaN epitaxial films have been directly grown by pulsed laser deposition (PLD) at 850 °C, and the effect of different stress on the microstructure of as-grown GaN epitaxial films has been explored in detail. The as-grown stress-free GaN epitaxial films exhibit very smooth surface without any particles and grains, which is confirmed by the smallest surface root-mean-square roughness of 2.3 nm measured by atomic force microscopy. In addition, they also have relatively high crystalline quality, which is proved by the small full-width at half maximum values of GaN(0002) and GaN (10 1 bar 2) X-ray rocking curves as 0.27° and 0.68°, respectively. However, when the growth temperature is lower or higher than 850 °C, internal or thermal stress would be increased in as-grown GaN epitaxial films. To release the larger stress, a great number of dislocations are generated. Many irregular particulates, hexagonal GaN gains and pits are therefore produced on the films surface, and the crystalline quality is greatly reduced consequently. This work has demonstrated the direct growth of stress-free GaN epitaxial films with excellent surface morphology and high crystalline quality by PLD, and presented a comprehensive study on the origins and the effect of stress in GaN layer. It is instructional to achieve high-quality nitride films by PLD, and shows great potential and broad prospect for the further development of high-performance GaN-based devices.

  2. Structural transitions in different monolayers of cobalt phthalocyanine film grown on Bi(1 1 1)

    NASA Astrophysics Data System (ADS)

    Tao, Min-Long; Tu, Yu-Bing; Sun, Kai; Zhang, Yao; Zhang, Xin; Li, Zhao-Bing; Hao, Shao-Jie; Xiao, Hua-Fang; Ye, Juan; Wang, Jun-Zhong

    2016-01-01

    The structural evolution of cobalt phthalocyanine (CoPc) thin films grown on a Bi(1 1 1) surface from the sub-monolayer to the third layer has been investigated with low-temperature scanning tunneling microscopy (STM). Two crucial transitions have been identified during the film epitaxial growth: one is the structural transition from zigzag chains to linear dimerized chains in the monolayer regime; the other is the molecular orientational transition from a flat-lying to a standing-up configuration in the multilayer regime. These results are helpful in understanding the growth mechanism of transition-metal phthalocyanine films on semi-metallic surfaces.

  3. Laser MBE-grown yttrium iron garnet films on GaN: characterization of the crystal structure and magnetic properties

    NASA Astrophysics Data System (ADS)

    Kaveev, A. K.; Bursian, V. E.; Gastev, S. V.; Krichevtsov, B. B.; Suturin, S. M.; Volkov, M. P.; Sokolov, N. S.

    2016-07-01

    Yttrium iron garnet (YIG) films were grown on GaN substrates using the laser molecular beam epitaxy method. X-ray diffraction data showed polycrystalline YIG layers without additional structural modifications. The magnetic properties of the YIG films were studied at room temperature with the aid of a vibration sample magnetometer, the magneto-optical Kerr effect and ferromagnetic resonance methods. ‘Easy-plane’-type magnetic anisotropy was found in the films. The gyromagnetic ratio and 4 πMS value were calculated.

  4. Optical, Electrical, and UV Photoresponse Properties of Fluorine-Doped ZnO Thin Films Grown on Flexible Mica Substrates

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-12-01

    Fluorine-doped ZnO (FZO) thin films have several potential applications, for instance, in low-cost optoelectronic devices; understanding how their optical, electrical, and photoresponse properties depend on and can be controlled via the synthesis conditions is essential for application of these systems. In this study, FZO thin films with different annealing temperatures were grown on muscovite mica substrates via sol-gel spin-coating. In photoluminescence measurements, a strong peak in the ultraviolet (UV) region and a broad peak in the visible region were observed for all films, being strongly dependent on the annealing temperature. The transmittance of the annealed films was slightly higher than that of as-grown film, and the absorption edges in the transmittance spectra red-shifted with increasing annealing temperature. The optical bandgap and Urbach energy of the films were calculated from the absorption coefficient values, using the Tauc and Urbach relations, respectively. Finally, the electrical (i.e., resistivity and carrier concentration) and photoresponse properties of the films were investigated to assess their applicability for use in FZO-based UV detectors.

  5. In-situ superconducting YBa2Cu3O7 thin films grown by ion beam co-deposition

    NASA Astrophysics Data System (ADS)

    James, J. H.; Kellett, B. J.; Gauzzi, A.; Dwir, B.; Pavuna, D.

    1989-12-01

    We present superconducting YBa2C3O7 (YBCO) thin films grown in-situ by three-ion-beam sputtering. Y, Y2O3, Cu, Cu2O, BaF2 and BaCO3 sputter targets have been investigated. The highest quality films were prepared using a BaCO3 target. Auger analysis of films grown using a BaCO3 target show no carbon content. Y2O3 and Cu2O are more suitable than the native metals as sputter targets for YBCO growth as they are much less prone to sputter rate variations with oxygen partial pressure. They also supply oxygen to the growing film. As-deposited YBCO films are metallic (resistivity 240 μΩ cm at 100 K), reflective, and of highly homogeneous composition with TCO transition temperatures of 73 K and transition widths of 15 K. Post-annealing in flowing oxygen improves TCO's to 82 K. Critical currents are in excess of 105 A cm-2 at 77 K. Films are textured with c-axis orientation perpendicular to the (100) SrTiO3 substrate surface. As-deposited superconducting YBCO films have also been prepared on SiO2 and Y2O3 buffer layers on Si wafers.

  6. Investigation of composition-induced strain effect in FexPt1-x films grown on different substrates

    NASA Astrophysics Data System (ADS)

    Dong, K. F.; Li, H. H.; Chen, J. S.

    2013-12-01

    Different composition FexPt1-x films were fabricated on three typical single crystal substrates (MgO, KTaO3, and SrTiO3), and the composition-induced strain evolution of FexPt1-x films was systematically investigated. The study showed that different Fe compositions in Fe-Pt films resulted in different strain status and crystallographic textures, and thus influenced the magnetic properties. Under the tensile strain between the Fe-Pt and (MgO, KTaO3, and SrTiO3) substrates, Fe-Pt films preferred to form ordered Fe-Pt (001) texture. Decrease of the Fe atom concentration caused the Fe-Pt films to be further relaxed, and an obvious increase of lattice constant c. Moreover, with reducing the mismatch between Fe-Pt and substrate from MgO to KTaO3 and SrTiO3, the strain status of Fe-Pt films changed from completely strained to partially relaxed. The perpendicular anisotropy of Fe55Pt45 films grown on STO was larger than that grown on MgO and KTO, which was attributed to better epitaxial quality of the FePt (001) texture induced by less lattice mismatch.

  7. Microstructures of InN film on 4H-SiC (0001) substrate grown by RF-MBE

    NASA Astrophysics Data System (ADS)

    Jantawongrit, P.; Sanorpim, S.; Yaguchi, H.; Orihara, M.; Limsuwan, P.

    2015-08-01

    InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF-MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ∼5.5 nm was grown on the substrate. Surface morphology, microstructure and structural quality of InN film were investigated. Micro-structural defects, such as stacking faults and anti-phase domain in InN film were carefully investigated using transmission electron microscopy (TEM). The results show that a high density of line contrasts, parallel to the growth direction (c-axis), was clearly observed in the grown InN film. Dark field TEM images recorded with diffraction vectors g=11\\bar{2}0 and g = 0002 revealed that such line contrasts evolved from a coalescence of the adjacent misoriented islands during the initial stage of the InN nucleation on the substrate surface. This InN nucleation also led to a generation of anti-phase domains. Project supported by the Thailand Center of Excellence in Physics (ThEP) and the King Mongkut's University of Technology Thonburi under The National Research University Project. One of the authors (S. Sanorpim) was supported by the National Research Council of Thailand (NRCT) and the Thai Government Stimulus Package 2 (TKK2555), under the Project for Establishment of Comprehensive Center for Innovative Food, Health Products and Agriculture.

  8. A comparative study of physico-chemical properties of CBD and SILAR grown ZnO thin films

    SciTech Connect

    Jambure, S.B.; Patil, S.J.; Deshpande, A.R.; Lokhande, C.D.

    2014-01-01

    Graphical abstract: Schematic model indicating ZnO nanorods by CBD (Z{sub 1}) and nanograins by SILAR (Z{sub 2}). - Highlights: • Simple methods for the synthesis of ZnO thin films. • Comparative study of physico-chemical properties of ZnO thin films prepared by CBD and SILAR methods. • CBD outperforms SILAR method. - Abstract: In the present work, nanocrystalline zinc oxide (ZnO) thin films have been successfully deposited onto glass substrates by simple and economical chemical bath deposition (CBD) and successive ionic layer adsorption reaction (SILAR) methods. These films were further characterized for their structural, optical, surface morphological and wettability properties. The X-ray diffraction (XRD) patterns for both CBD and SILAR deposited ZnO thin films reveal the highly crystalline hexagonal wurtzite structure. From optical studies, band gaps obtained are 2.9 and 3.0 eV for CBD and SILAR deposited thin films, respectively. The scanning electron microscope (SEM) patterns show growth of well defined randomly oriented nanorods and nanograins on the CBD and SILAR deposited samples, respectively. The resistivity of CBD deposited films (10{sup 2} Ω cm) is lower than that of SILAR deposited films (10{sup 5} Ω cm). Surface wettability studies show hydrophobic nature for both films. From the above results it can be concluded that CBD grown ZnO thin films show better properties as compared to SILAR method.

  9. RBS and PIXE analysis of chlorine contamination in ALD-Grown TiN films on silicon

    SciTech Connect

    Meersschaut, J.; Witters, T.; Kaeyhkoe, M.; Lenka, H. P.; Vandervorst, W.; Zhao, Q.; Vantomme, A.

    2013-04-19

    The performance, strengths and limitations of RBS and PIXE for the characterization of trace amounts of Cl in TiN thin films are critically compared. The chlorine atomic concentration in ALD grown TiN thin films on Si is determined for samples grown at temperatures ranging from 350 Degree-Sign C to 550 Degree-Sign C. We show that routine Rutherford backscattering spectrometry measurements (1.5 MeV He{sup +}) and PIXE measurements (1.5 MeV H{sup +}) on 20 nm thick TiN films allow one to determine the Cl content down to 0.3 at% with an absolute statistical accuracy reaching 0.03 at%. Possible improvements to push the sensitivity limit for both approaches are proposed.

  10. X-ray Investigation of Ferromagnetic MnAs Thin Films Grown on GaAs(001) by MBE

    NASA Astrophysics Data System (ADS)

    Huang, S.; Ming, Z. H.; Soo, Y. L.; Kao, Y. H.; Tanaka, M.; Munekata, H.

    1996-03-01

    Quantitative characterization of the microstructures in epitaxial layers grown by MBE is essential for understanding the dynamical processes of epitaxy and surface morphology. In the present study, various x-ray techniques including grazing incidence x-ray scattering (GIXS), x-ray diffraction (XRD), and extended x-ray absorption fine structure (EXAFS) have been employed to investigate the microstructures of two MnAs thin films grown on GaAs(001) by using two different growth templates. The film structures are compared in terms of the interfacial roughness, lattice constants, epilayer thickness, local environment surrounding the Mn atoms, coordination number, and local disorder. These results provide quantitative evidence for the effects of template on the local structure and crystallinity of the MnAs films which can be correlated with the observed difference in their physical properties such as the easy magnetization direction, etc.. * Research is supported in part by DOE.

  11. Epitaxial metallic β-Nb2N films grown by MBE on hexagonal SiC substrates

    NASA Astrophysics Data System (ADS)

    Katzer, D. Scott; Nepal, Neeraj; Meyer, David J.; Downey, Brian P.; Wheeler, Virginia D.; Storm, David F.; Hardy, Matthew T.

    2015-08-01

    RF-plasma MBE was used to epitaxially grow 4- to 100-nm-thick metallic β-Nb2N thin films on hexagonal SiC substrates. When the N/Nb flux ratios are greater than one, the most critical parameter for high-quality β-Nb2N is the substrate temperature. The X-ray characterization of films grown between 775 and 850 °C demonstrates β-Nb2N phase formation. The (0002) and (21\\bar{3}1) X-ray diffraction measurements of a β-Nb2N film grown at 850 °C reveal a 0.68% lattice mismatch to the 6H-SiC substrate. This suggests that β-Nb2N can be used for high-quality metal/semiconductor heterostructures that cannot be fabricated at present.

  12. Fe films grown on GaAs(110) in a two-step process: Improved structural and magnetic properties

    SciTech Connect

    Winking, L.; Wenderoth, M.; Homoth, J.; Siewers, S.; Ulbrich, R. G.

    2008-05-12

    Fe films of up to 10 ML thickness were grown on cleaved GaAs(110) in a two-step process that associates low-temperature deposition at 130 K with a subsequent annealing to room temperature. Low-energy electron diffraction, scanning tunneling microscopy, and in situ magneto-optical Kerr effect were combined to study these films. The observed magnetic and structural properties are distinctly different from the characteristics of conventionally grown Fe films on GaAs. We found no indication of interface compound formation. The applied two-step growth process is a promising technique to further increase spin-injection and detection efficiencies of Fe/GaAs hybrid structures.

  13. Nanomechanical properties of SiC films grown from C{sub 60} precursors using atomic force microscopy

    SciTech Connect

    Morse, K.; Balooch, M.; Hamza, A.V.; Belak, J.

    1994-12-01

    The mechanical properties of SiC films grown via C{sub 60} precursors were determined using atomic force microscopy (AFM). Conventional silicon nitride and modified diamond cantilever AFM tips were employed to determine the film hardness, friction coefficient, and elastic modulus. The hardness is found to be between 26 and 40 GPa by nanoindentation of the film with the diamond tip. The friction coefficient for the silicon nitride tip on the SiC film is about one third that for silicon nitride sliding on a silicon substrate. By combining nanoindentation and AFM measurements an elastic modulus of {approximately}300 GPa is estimated for these SiC films. In order to better understand the atomic scale mechanisms that determine the hardness and friction of SiC, we simulated the molecular dynamics of a diamond indenting a crystalline SiC substrate.

  14. Nanoscale characterization of TiO(2) films grown by atomic layer deposition on RuO(2) electrodes.

    PubMed

    Murakami, Katsuhisa; Rommel, Mathias; Hudec, Boris; Rosová, Alica; Hušeková, Kristína; Dobročka, Edmund; Rammula, Raul; Kasikov, Aarne; Han, Jeong Hwan; Lee, Woongkyu; Song, Seul Ji; Paskaleva, Albena; Bauer, Anton J; Frey, Lothar; Fröhlich, Karol; Aarik, Jaan; Hwang, Cheol Seong

    2014-02-26

    Topography and leakage current maps of TiO2 films grown by atomic layer deposition on RuO2 electrodes using either a TiCl4 or a Ti(O-i-C3H7)4 precursor were characterized at nanoscale by conductive atomic force microscopy (CAFM). For both films, the leakage current flows mainly through elevated grains and not along grain boundaries. The overall CAFM leakage current is larger and more localized for the TiCl4-based films (0.63 nm capacitance equivalent oxide thickness, CET) compared to the Ti(O-i-C3H7)4-based films (0.68 nm CET). Both films have a physical thickness of ∼20 nm. The nanoscale leakage currents are consistent with macroscopic leakage currents from capacitor structures and are correlated with grain characteristics observed by topography maps and transmission electron microscopy as well as with X-ray diffraction. PMID:24483129

  15. Epitaxial strontium titanate films grown by atomic layer deposition on SrTiO{sub 3}-buffered Si(001) substrates

    SciTech Connect

    McDaniel, Martin D.; Posadas, Agham; Ngo, Thong Q.; Dhamdhere, Ajit; Smith, David J.; Demkov, Alexander A.; Ekerdt, John G.

    2013-01-15

    Epitaxial strontium titanate (STO) films have been grown by atomic layer deposition (ALD) on Si(001) substrates with a thin STO buffer layer grown by molecular beam epitaxy (MBE). Four unit cells of STO grown by MBE serve as the surface template for ALD growth. The STO films grown by ALD are crystalline as-deposited with minimal, if any, amorphous SiO{sub x} layer at the STO-Si interface. The growth of STO was achieved using bis(triisopropylcyclopentadienyl)-strontium, titanium tetraisopropoxide, and water as the coreactants at a substrate temperature of 250 Degree-Sign C. In situ x-ray photoelectron spectroscopy (XPS) analysis revealed that the ALD process did not induce additional Si-O bonding at the STO-Si interface. Postdeposition XPS analysis also revealed sporadic carbon incorporation in the as-deposited films. However, annealing at a temperature of 250 Degree-Sign C for 30 min in moderate to high vacuum (10{sup -6}-10{sup -9} Torr) removed the carbon species. Higher annealing temperatures (>275 Degree-Sign C) gave rise to a small increase in Si-O bonding, as indicated by XPS, but no reduced Ti species were observed. X-ray diffraction revealed that the as-deposited STO films were c-axis oriented and fully crystalline. A rocking curve around the STO(002) reflection gave a full width at half maximum of 0.30 Degree-Sign {+-} 0.06 Degree-Sign for film thicknesses ranging from 5 to 25 nm. Cross-sectional transmission electron microscopy revealed that the STO films were continuous with conformal growth to the substrate and smooth interfaces between the ALD- and MBE-grown STO. Overall, the results indicate that thick, crystalline STO can be grown on Si(001) substrates by ALD with minimal formation of an amorphous SiO{sub x} layer using a four-unit-cell STO buffer layer grown by MBE to serve as the surface template.

  16. Structural and magnetic properties of SmCo-based magnetic films grown by electron-beam evaporation

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Vinod, V. T. P.; Černík, Miroslav; Vishnuraj, R.; Arout Chelvane, J.; Kamat, S. V.; Hsu, Jen-Hwa

    2015-07-01

    Sub-micron thick Sm-Co films (200 and 300 nm) with selective phase composition are grown on Si (100) substrates by electron-beam evaporation using Sm-lean alloy targets such as Sm4Co96 and Sm8Co92. The structural and magnetic properties of Sm-Co films are characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and super-conducting quantum interference device (SQUID) magnetometer. The Sm-Co films obtained with the Sm4Co96 target exhibit Sm2Co17 as a prominent phase; while the films produced with the Sm8Co92 target show Sm2Co7 as a major phase. Both the Sm-Co films reveal granular morphology; however, the estimated grain size values are slightly lower in the case of Sm2Co7 films, irrespective of their thicknesses. Coercivity (Hc) values of 1.48 and 0.9 kOe are achieved for the as-grown 200-nm thick Sm2Co17 and Sm2Co7-films. Temperature-dependent magnetization studies confirm that the demagnetization behaviors of these films are consistent with respect to the identified phase composition. Upon rapid thermal annealing, maximum Hc value of 8.4 kOe is achieved for the 200 nm thick Sm2Co17-films. As far as e-beam evaporated Sm-Co films are concerned, this Hc value is one of the best values reported so far.

  17. Comparative study of magnetite (Fe3O4) thin films grown by pulsed laser ablation and sputtering

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Varun Karthik Y., S.; Haveesh, G.; Tarun Y. S., N.; Prasad, D. V. B.; Chowdhury, D. Roy; Prasad, K. Eswar

    2016-05-01

    Comparative study of magnetite (Fe3O4) thin films grown by pulsed laser ablation (PLD) and radio frequency (RF)-sputtering of α-Fe2O3 target have been investigated. We have found strong correlation between RF power (P) of sputtering and substrate temperature (Ts) of PLD films on their structural and magnetic properties. Films grown at low P and Ts are dominated by antiferromagnetic α-Fe2O3 phase while ferrimagnetic Fe3O4 phase is dominant at high P and Ts Post-annealing in H2/H2O atmosphere at 450 °C, these films show single phase Fe3O4 but RF power and substrate temperature still play a significant role. With increasing P and Ts values, the orientation of Fe3O4 films change from (110) to (111) followed by complete randomizations. These (110) to (111) orientations affect magnetic properties differently above Verwey transition temperature of 120 K. The RF-power and substrate temperature have the same influence on the physical properties of Fe3O4 films, as both are related to thermal energy.

  18. Semipolar and nonpolar GaN epi-films grown on m-sapphire by plasma assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Mukundan, Shruti; Mohan, Lokesh; Chandan, Greeshma; Roul, Basanta; Krupanidhi, S. B.

    2014-11-01

    We hereby report the development of non-polar epi-GaN films of usable quality, on an m-plane sapphire. Generally, it is difficult to obtain high-quality nonpolar material due to the planar anisotropic nature of the growth mode. However, we could achieve good quality epi-GaN films by involving controlled steps of nitridation. GaN epilayers were grown on m-plane (10-10) sapphire substrates using plasma assisted molecular beam epitaxy. The films grown on the nitridated surface resulted in a nonpolar (10-10) orientation while without nitridation caused a semipolar (11-22) orientation. Room temperature photoluminescence study showed that nonpolar GaN films have higher value of compressive strain as compared to semipolar GaN films, which was further confirmed by room temperature Raman spectroscopy. The room temperature UV photodetection of both films was investigated by measuring the I-V characteristics under UV light illumination. UV photodetectors fabricated on nonpolar GaN showed better characteristics, including higher external quantum efficiency, compared to photodetectors fabricated on semipolar GaN. X-ray rocking curves confirmed better crystallinity of semipolar as compared to nonpolar GaN which resulted in faster transit response of the device.

  19. Semipolar and nonpolar GaN epi-films grown on m-sapphire by plasma assisted molecular beam epitaxy

    SciTech Connect

    Mukundan, Shruti; Mohan, Lokesh; Chandan, Greeshma; Krupanidhi, S. B.; Roul, Basanta

    2014-11-28

    We hereby report the development of non-polar epi-GaN films of usable quality, on an m-plane sapphire. Generally, it is difficult to obtain high-quality nonpolar material due to the planar anisotropic nature of the growth mode. However, we could achieve good quality epi-GaN films by involving controlled steps of nitridation. GaN epilayers were grown on m-plane (10-10) sapphire substrates using plasma assisted molecular beam epitaxy. The films grown on the nitridated surface resulted in a nonpolar (10-10) orientation while without nitridation caused a semipolar (11-22) orientation. Room temperature photoluminescence study showed that nonpolar GaN films have higher value of compressive strain as compared to semipolar GaN films, which was further confirmed by room temperature Raman spectroscopy. The room temperature UV photodetection of both films was investigated by measuring the I-V characteristics under UV light illumination. UV photodetectors fabricated on nonpolar GaN showed better characteristics, including higher external quantum efficiency, compared to photodetectors fabricated on semipolar GaN. X-ray rocking curves confirmed better crystallinity of semipolar as compared to nonpolar GaN which resulted in faster transit response of the device.

  20. Interfacially engineered oxygen octahedral rotations and their impact on strain relief in coherently grown SrRu O3 films

    NASA Astrophysics Data System (ADS)

    Kan, Daisuke; Wakabayashi, Yusuke; Tajiri, Hiroo; Shimakawa, Yuichi

    2016-07-01

    We report synchrotron x-ray diffraction investigations of interfacially engineered oxygen octahedral rotations and their impact on strain relief in perovskite SrRu O3 films. We show that octahedral rotations with distinct patterns and magnitudes can be accommodated into coherently grown films. The SrRu O3 film grown directly on the GdSc O3 substrate has the Ru O6 octahedral rotation with the a-b+c- pattern in the Glazer notation and the rotation angles of αrot=6.6 ±0 .2∘ , βrot=5.5 ±0 .2∘ , and γrot=3.6 ±0 .2∘ . On the other hand, when a 1-nm-thick BaTi O3 layer without Ti O6 rotations is inserted between the SrRu O3 and GdSc O3 , the SrRu O3 has the Ru O6 rotation with a-b0c+ , and αrot=5.6 ±0 .8∘ and γrot=3.6 ±0 .8∘ . These results indicate that there are some degrees of freedom in the octahedral rotations accommodated in SrRu O3 depending on the interface structure and that the γrot rotations play the important roles in the film's structural properties when the rotation about the [010] pc axis is blocked. We also found that the strain relief in the film is influenced by the interfacially engineered octahedral rotations. The interfacial BaTi O3 layer results in the in-plane periodic lattice modulation in the t-SRO film, allowing for the anisotropic relief of the substrate-induced strain. The results highlight the importance of the interface structure as a factor, determining not only octahedral rotations in coherently grown SRO films but also the strain reliefs in them.

  1. (110)-oriented indium tin oxide films grown on m- and r-plane sapphire substrates

    NASA Astrophysics Data System (ADS)

    Chern, Ming-Yau; Lu, Tso-Wen; Xu, Wei-Lun

    2015-04-01

    Indium tin oxide (ITO) thin films have been deposited by pulsed laser deposition on m-plane (100) and r-plane (012) sapphire substrates. For both substrates, the films were grown with their [110] direction perpendicular to the substrate planes under the conditions of high growth temperature and high oxygen pressure. Their in-plane epitaxial relations with the substrates were identified to be ITO[001] ∥ Al2O3[020] and \\text{ITO}[1\\bar{1}0]\\parallel \\text{Al}2\\text{O}3[001] for the m-plane substrate. For the r-plane substrate, two types of lattice matching were observed: one being \\text{ITO}[001]\\parallel \\text{Al}2\\text{O}3[2,1, - 1/2] and \\text{ITO}[1\\bar{1}0]\\parallel \\text{Al}2\\text{O}3[4/3, - 4/3,2/3], the other being \\text{ITO}[001]\\parallel \\text{Al}2\\text{O}3[1, - 1,1/2] and \\text{ITO}[1\\bar{1}0]/\\text{Al}2\\text{O}3[8/3,4/3, - 2/3]. The electrical properties were measured by the Hall effect and van der Pauw methods at room temperature. All of the samples have low electrical resistivity on the order of 3.0 × 10-4 Ω cm, high carrier concentration of about 2.5 × 1020 cm-3, and mobility ranging from 70 to 90 cm2 V-1 s-1.

  2. Spectroscopic Ellipsometry of 3C-SiC Thin Films Grown on Si Substrates Using Organosilane Sources

    NASA Astrophysics Data System (ADS)

    Kubo, Naoki; Moritani, Akihiro; Kitahara, Kuninori; Asahina, Shuichi; Kanayama, Nobuyuki; Tsutsumi, Koichi; Suzuki, Michio; Nishino, Shigehiro

    2005-06-01

    Dielectric function spectra of 3C-SiC films on Si substrates in the energy region of 0.73-6.43 eV were measured by spectroscopic ellipsometry. Hexamethyldisilane (Si2(CH3)6) and tetraethylsilane (Si(C2H5)4) were used as safe organosilane sources for the growth of SiC films. The measured spectra were compared with those of 3C-SiC on a Si(001) substrate grown with disilane (Si2H6). First, the pseudodielectric function spectra gave a shoulder structure corresponding to the direct X5-X1 interband transition in the Brillouin zone. Secondly, the dielectric function of 3C-SiC was determined by applying a four-layer model in which we took into account the surface roughness and mixed crystals of a carbonized interface layer. Finally, the third-derivative lineshape of the imaginary part \\varepsilon2 of the complex-dielectric function provided the values of the interband transition energy Eg and the broadening parameter Γ for the X5-X1 interband transition. The measured values of Γ indicated that the crystalline quality of SiC films grown using organosilane sources is comparable to that of SiC films grown using Si2H6.

  3. Comparative studies of nonpolar (10-10) ZnO films grown by using atomic layer deposition and radio-frequency magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Choi, Nak-Jung; Son, Hyo-Soo; Choi, Hyun-Jun; Kim, Kyoung-Kook; Lee, Sung-Nam

    2014-08-01

    We comparatively investigated the crystal and the optical properties of nonpolar (10-10) ZnO films grown on m-plane sapphire substrates by using atomic layer deposition (ALD) and radio frequency (RF) magnetron sputtering. From high-resolution X-ray ω/2 θ scans, the (100) peak of the ALD-grown ZnO film was clearly developed at ~ 15.9 ° while that of the RF sputter-grown ZnO was broadly observed at 15.6 ~ 15.9 °, indicating that a nonpolar (10-10) ZnO film would be preferentially grown on an m-plane sapphire substrate. The photoluminescence bandedge emission intensity of the ALD-grown (10-10) ZnO film was ten times higher than that of the RF sputtergrown ZnO film. In addition, the electroluminescence intensity of a semipolar (11-22) GaN-based light-emitting diode (LED) with an ALD-grown (10-10) ZnO film as a transparent conductive oxide material was much higher than that of a semipolar (11-22) GaN-based LED with RF sputter-grown (10-10) ZnO film.

  4. 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

  5. Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity

    SciTech Connect

    Chen, Xinchun Kato, Takahisa

    2014-01-28

    Growth mechanism and ion energy dependence of composition of ultrasmooth a-C:H:Si films grown from ionization of tetramethylsilane (TMS) and toluene mixture at a fixed gas ratio have been investigated by varying the applied bias voltage. The dynamic scaling theory is employed to evaluate the roughness evolution of a-C:H:Si films, and to extract roughness and growth exponents of α ∼ 0.51 and β ∼ 0, respectively. The atomically smooth surface of a-C:H:Si films with Ra ∼ 0.1 nm is thermally activated by the energetic ion-impact induced subsurface “polishing” process for ion dominated deposition. The ion energy (bias voltage) plays a paramount role in determining the hydrogen incorporation, bonding structure and final stoichiometry of a-C:H:Si films. The hydrogen content in the films measured by ERDA gradually decreases from 36.7 to 17.3 at. % with increasing the bias voltage from 0.25 to 3.5 kV, while the carbon content in the films increases correspondingly from 52.5 to 70.1 at. %. The Si content is kept almost constant at ∼9–10 at. %. Depending on the ion-surface interactions, the bonding structure of a-C:H:Si films grown in different ion energy regions evolves from chain-developed polymer-like to cross-linked diamond-like to sp{sup 2}-bonded a–C as revealed by XPS, Raman, and FTIR analysis. Such a structural evolution is reflected in their measured nanomechanical properties such as hardness, modulus, and compressive stress. An enhanced viscoplastic behavior (i.e., viscoplastic exponent of ∼0.06) is observed for polymeric a-C:H:Si films. A hydrogen content threshold (H > 20 at. %) exists for the as-grown a-C:H:Si films to exhibit superlow friction in dry N{sub 2} atmosphere. An extremely low friction coefficient of ∼0.001 can be obtained for polymer-like a-C:H:Si film. These near-frictionless a-C:H:Si films are strongly promising for applications in industrial lubricating systems.

  6. Growth mechanism and composition of ultrasmooth a-C:H:Si films grown from energetic ions for superlubricity

    NASA Astrophysics Data System (ADS)

    Chen, Xinchun; Kato, Takahisa

    2014-01-01

    Growth mechanism and ion energy dependence of composition of ultrasmooth a-C:H:Si films grown from ionization of tetramethylsilane (TMS) and toluene mixture at a fixed gas ratio have been investigated by varying the applied bias voltage. The dynamic scaling theory is employed to evaluate the roughness evolution of a-C:H:Si films, and to extract roughness and growth exponents of α ˜ 0.51 and β ˜ 0, respectively. The atomically smooth surface of a-C:H:Si films with Ra ˜ 0.1 nm is thermally activated by the energetic ion-impact induced subsurface "polishing" process for ion dominated deposition. The ion energy (bias voltage) plays a paramount role in determining the hydrogen incorporation, bonding structure and final stoichiometry of a-C:H:Si films. The hydrogen content in the films measured by ERDA gradually decreases from 36.7 to 17.3 at. % with increasing the bias voltage from 0.25 to 3.5 kV, while the carbon content in the films increases correspondingly from 52.5 to 70.1 at. %. The Si content is kept almost constant at ˜9-10 at. %. Depending on the ion-surface interactions, the bonding structure of a-C:H:Si films grown in different ion energy regions evolves from chain-developed polymer-like to cross-linked diamond-like to sp2-bonded a-C as revealed by XPS, Raman, and FTIR analysis. Such a structural evolution is reflected in their measured nanomechanical properties such as hardness, modulus, and compressive stress. An enhanced viscoplastic behavior (i.e., viscoplastic exponent of ˜0.06) is observed for polymeric a-C:H:Si films. A hydrogen content threshold (H > 20 at. %) exists for the as-grown a-C:H:Si films to exhibit superlow friction in dry N2 atmosphere. An extremely low friction coefficient of ˜0.001 can be obtained for polymer-like a-C:H:Si film. These near-frictionless a-C:H:Si films are strongly promising for applications in industrial lubricating systems.

  7. Electronic properties of passive films grown on Al 7075 in solutions containing oxalate and chromate

    SciTech Connect

    Kobotiatis, L.; Kioupis, N.; Koutsoukos, P.G.

    1997-07-01

    Electronic properties of passive layers grown anodically on Al 7075 (UNS A97075) in chromate and oxalate solutions during polarization at 500 mV{sub SCE} were investigated using electrochemical impedance spectroscopy. Impedance results were analyzed in terms of capacitance-vs-frequency plots during reverse polarization from 500 mV{sub SCE} to more negative potentials. Plots yielded capacitance values dependent upon both frequency and applied potential. Increases in capacitance with decreasing potential were attributed to width variations of a space charge inside the passive film. Mott-Schottky plots gave slopes and intersection potentials dependent upon the imposed alternating current signal frequency. Data were interpreted on the basis of the amorphous semiconductor/electrolyte junction theory. Differences were found in semiconducting properties of the passive layers formed in solutions containing chromate and oxalate ions. These differences were related to the anticorrosive resistance toward pitting, since it is well known that chromate is a more effective inhibitor than oxalate. The oxide developed in the presence of chromate ions exhibited less noble flat-band potentials and lower average densities of states.

  8. Surface cleaning procedures for thin films of indium gallium nitride grown on sapphire

    NASA Astrophysics Data System (ADS)

    Douglass, K.; Hunt, S.; Teplyakov, A.; Opila, R. L.

    2010-12-01

    Surface preparation procedures for indium gallium nitride (InGaN) thin films were analyzed for their effectiveness for carbon and oxide removal as well as for the resulting surface roughness. Aqua regia (3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid, AR), hydrofluoric acid (HF), hydrochloric acid (HCl), piranha solution (1:1 mixture of sulfuric acid and 30% H 2O 2) and 1:9 ammonium sulfide:tert-butanol were all used along with high temperature anneals to remove surface contamination. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were utilized to study the extent of surface contamination and surface roughness, respectively. The ammonium sulfide treatment provided the best overall removal of oxygen and carbon. Annealing over 700 °C after a treatment showed an even further improvement in surface contamination removal. The piranha treatment resulted in the lowest residual carbon, while the ammonium sulfide treatment leads to the lowest residual oxygen. AFM data showed that all the treatments decreased the surface roughness (with respect to as-grown specimens) with HCl, HF, (NH 4) 2S and RCA procedures giving the best RMS values (˜0.5-0.8 nm).

  9. Dynamics of surface evolution in semiconductor thin films grown from a chemical bath.

    PubMed

    Gupta, Indu; Mohanty, Bhaskar Chandra

    2016-01-01

    Dynamics of surface evolution in CdS thin films grown by chemical bath deposition technique has been studied from time sequence of atomic force micrographs. Detailed scaling analysis of surface fluctuation in real and Fourier space yielded characteristic exponents αloc = 0.78 ± 0.07, α = 2.20 ± 0.08, αs = 1.49 ± 0.22, β = 0.86 ± 0.05 and βloc = 0.43 ± 0.10, which are very different from those predicted by the local growth models and are not related to any known universality classes. The observed anomalous scaling pattern, characterized by power law scaling dependence of interface width on deposition time differently at local and global scale, with rapid roughening of the growth front has been discussed to arise as a consequence of a nonlocal effect in the form of diffusional instability. PMID:27615367

  10. Electrical properties of scandium nitride epitaxial films grown on (100) magnesium oxide substrates by molecular beam epitaxy

    SciTech Connect

    Ohgaki, Takeshi; Watanabe, Ken; Adachi, Yutaka; Sakaguchi, Isao; Hishita, Shunichi; Ohashi, Naoki; Haneda, Hajime

    2013-09-07

    Scandium nitride (ScN) films were grown on (100) MgO single crystals by a molecular beam epitaxy method. The effects of growth conditions, including [Sc]/[N] ratio, growth temperature, and nitrogen radical state, on the electrical properties of the ScN films were studied. The ScN films comprised many small columnar grains. Hall coefficient measurements confirmed that the ScN films were highly degenerate n-type semiconductors and that the carrier concentration of the ScN films was sensitive to the growth temperature and the nitrogen radical states during the film growth. The carrier concentrations of the ScN films ranged from 10{sup 19}–10{sup 21} cm{sup −3} while the Hall mobilities ranged from 50–130 cm{sup 2}·V{sup −1}·s{sup −1} for undoped films. The temperature-dependent Hall coefficient measurements showed that the carrier concentration is nearly independent of temperature, indicating that the change in resistivity with temperature is explained by a change in the Hall mobility. The temperature-dependence of the Hall mobility was strongly affected by the growth conditions.

  11. Study of optical and structural properties of CZTS thin films grown by co-evaporation and spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Ramirez, E. A.; Gordillo Guzmán, G.

    2016-02-01

    Results regarding optical and structural properties of Cu2ZnSnS4 (CZTS) thin films prepared by co-evaporation using a novel procedure are compared with those obtained with CZTS films grown using a solution based route. The lattice strain ε and crystallite size D of CZTS films prepared by co-evaporation and by spray pyrolysis were estimated through X-ray diffraction (XRD) measurements using Williamson-Hall-isotropic strain model. The results of estimated average crystallite size of CZTS films by Scherrer and Williamson-Hall plot methods were compared with AFM (atomic force microscopy) measurements. It was found that the average crystallite size measured by Williamson-Hall plot methods agree quite well with AFM results. Further, information regarding the influence of preparation method on both, crystalline phases and the formation of structural defects was achieved through Raman and Urbach energy measurements.

  12. Correlation of Crystalline and Structural Properties of C60 Thin Films Grown at Various Temperature with Charge Carrier Mobility

    SciTech Connect

    Singh,T.; Sarciftci, N.; Yang, H.; Yang, L.; Plochberger, B.; Sitter, H.

    2007-01-01

    Transistors fabricated from C{sub 60} films grown by hot wall epitaxy at higher substrate temperature, showed an order of magnitude increased charge carrier mobility up to 6 cm{sup 2}/V s. In this letter, the authors present an extensive study of morphology and crystallinity of the fullerene films using atomic force microscopy and grazing-incidence x-ray diffraction. A clear correlation of crystalline quality of the C{sub 60} film and charge carrier mobility was found. A higher substrate temperature leads to a single crystal-like faceted fullerene crystals. The high crystalline quality solely brings a drastic improvement in the charge carrier mobility. A gate voltage independent mobility is also observed in these devices which can be attributed to the highly conjugated nature of the C{sub 60} thin film.

  13. The microstructure, optical and electrical property of CdZnTe thick films grown from a CSS method

    NASA Astrophysics Data System (ADS)

    Zhang, Yuelu; Wang, Linjun; Xu, Run; Huang, Jian; Meng, Hua; Tao, Jun; Zhang, Jijun; Min, Jiahua; Shen, Yue

    2015-12-01

    Polycrystalline CdZnTe thick films with an average grain size of 30 μm and thickness of 270 μm were successfully grown on SnO2:F (FTO)-coated glass substrates by close-spaced sublimation method. Electrical properties and UV response of CdZnTe thick films after Br-MeOH etching and ZnCl2 annealing treatment were investigated. By means of the photo-current measurements, the value of mobility-lifetime (μτ) products for CdZnTe films were firstly reported. The results showed that Br-MeOH etching significantly improved UV detection sensitivity of CdZnTe thick films, and made the surface distribution of UV sensitivity more homogeneous. It was also found that a ZnCl2 annealing process did not improve the electrical properties.

  14. Critical thickness and strain relaxation in molecular beam epitaxy-grown SrTiO3 films

    NASA Astrophysics Data System (ADS)

    Wang, Tianqi; Ganguly, Koustav; Marshall, Patrick; Xu, Peng; Jalan, Bharat

    2013-11-01

    We report on the study of the critical thickness and the strain relaxation in epitaxial SrTiO3 film grown on (La0.3Sr0.7)(Al0.65Ta0.35)O3 (001) (LSAT) substrate using the hybrid molecular beam epitaxy approach. No change in the film's lattice parameter (both the in-plane and the out-of-plane) was observed up to a film thickness of 180 nm, which is in sharp contrast to the theoretical critical thickness of ˜12 nm calculated using the equilibrium theory of strain relaxation. For film thicknesses greater than 180 nm, the out-of-plane lattice parameter was found to decrease hyperbolically in an excellent agreement with the relaxation via forming misfit dislocations. Possible mechanisms are discussed by which the elastic strain energy can be accommodated prior to forming misfit dislocations leading to such anomalously large critical thickness.

  15. Electric fatigue in Pb(Nb,Zr,Sn,Ti)O3 thin films grown by a sol-gel process

    NASA Astrophysics Data System (ADS)

    Zhai, Jiwei; Chen, Haydn

    2003-08-01

    Antiferroelectric Pb(Nb,Zr,Sn,Ti)O3 (PNZST) thin films were deposited via a sol-gel process on LaNiO3-buffered Pt/Ti/SiO2/Si substrates. The highly (100)-oriented LaNiO3 buffer layer facilitated the formation of high-quality PNZST films with a strong (100) preferred orientation. These films showed improved electric fatigue properties than those grown on Pt/Ti/SiO2/Si substrates. With increasing cycling field, the remanent polarization increases but the saturated polarization decreases. Fatigue properties of PNZST antiferroelectric thin films might be closely related to the nonuniform strain buildup due to switching that tends to stabilize the ferroelectric phase.

  16. Low-relaxation spin waves in laser-molecular-beam epitaxy grown nanosized yttrium iron garnet films

    NASA Astrophysics Data System (ADS)

    Lutsev, L. V.; Korovin, A. M.; Bursian, V. E.; Gastev, S. V.; Fedorov, V. V.; Suturin, S. M.; Sokolov, N. S.

    2016-05-01

    Synthesis of nanosized yttrium iron garnet (Y3Fe5O12, YIG) films followed by the study of ferromagnetic resonance (FMR) and spin wave propagation in these films is reported. The YIG films were grown on gadolinium gallium garnet substrates by laser molecular beam epitaxy. It has been shown that spin waves propagating in YIG deposited at 700 °C have low damping. At the frequency of 3.29 GHz, the spin-wave damping parameter is less than 3.6 × 10-5. Magnetic inhomogeneities of the YIG films give the main contribution to the FMR linewidth. The contribution of the relaxation processes to the FMR linewidth is as low as 1.2%.

  17. Effects of growth temperature on the properties of atomic layer deposition grown ZrO2 films

    NASA Astrophysics Data System (ADS)

    Scarel, G.; Ferrari, S.; Spiga, S.; Wiemer, C.; Tallarida, G.; Fanciulli, M.

    2003-07-01

    Zirconium dioxide films are grown in 200 atomic layer deposition cycles. Zirconium tetrachloride (ZrCl4) and water (H2O) are used as precursors. A relatively high dielectric constant (κ=22), wide band gap, and conduction band offset (5.8 and 1.4 eV, respectively) indicate that zirconium dioxide is a most promising substitute for silicon dioxide as a dielectric gate in complementary metal-oxide-semiconductor devices. However, crystallization and chlorine ions in the films might affect their electrical properties. These ions are produced during atomic layer deposition in which the ZrCl4 precursor reacts with the growth surface. It is desirable to tune the composition, morphology, and structural properties in order to improve their benefit on the electrical ones. To address this issue it is necessary to properly choose the growth parameters. This work focuses on the effects of the growth temperature Tg. ZrO2 films are grown at different substrate temperatures: 160, 200, 250, and 350 °C. Relevant modification of the film structure with a change in substrate temperature during growth is expected because the density of reactive sites [mainly Si+1-(OH)-1 bonds] decreases with an increase in temperature [Y. B. Kim et al., Electrochem. Solid-State Lett. 3, 346 (2000)]. The amorphous film component, for example, that develops at Si+1-(OH)-1 sites on the starting growth surface, is expected to decrease with an increase in growth temperature. The size and consequences of film property modifications with the growth temperature are investigated in this work using x-ray diffraction and reflectivity, and atomic force microscopy. Time of flight-secondary ion mass spectrometry is used to study contaminant species in the films. From capacitance-voltage (CV) and current-voltage (IV) measurements, respectively, the dielectric constant κZrO2 and the leakage current are studied as a function of the film growth temperature.

  18. Nonlinear optical dynamics and Eu3+ spectral holeburning in strontium barium niobate thin film grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Liu, H.; Liu, G. K.; Li, S. T.; Beitz, J. V.; Fernandez, F. E.

    2002-01-01

    Optical quality SrxBa1-xNb2O6 (SBN) thin films, both undoped and Eu3+-doped, of thickness less than 0.5 μm have been successfully grown on fused quartz substrates using a pulsed laser deposition technique. Optical properties of these films were characterized in high-resolution spectroscopic experiments in time and frequency domains. For undoped SBN thin films, broadband emission in the UV region extending to the visible was observed following excitation at 355 nm. This emission is attributed to exciton luminescence of the SBN film. Nonlinear optical response in the picosecond regime and the third-order nonlinear susceptibility, χ(3), were studied using degenerate four-wave-mixing methods. In transverse alignment, χ(3) is enhanced by two orders of magnitude in comparison with its bulk counterpart. A thermal annealing process, monitored via changes in spectral properties of Eu3+, was employed to convert the as-grown amorphous film into a polycrystalline film. High-resolution spectroscopic measurements in the frequency domain were conducted on a 200-nm-thick film of Eu3+-doped SBN. Our spectroscopic results suggest that Eu3+ ions may substitute for Nb, thereby occupying a normally six-fold coordinated lattice site. At liquid helium temperature, spectral holes in the 7F0-5D0 optical transition were burned in the thermally annealed films. Typical observed hole widths were 70-100 MHz and hole depths were as large as 30% of the peak fluorescence intensity.

  19. High Stability Electron Field Emitters Synthesized via the Combination of Carbon Nanotubes and N₂-Plasma Grown Ultrananocrystalline Diamond Films.

    PubMed

    Chang, Ting-Hsun; Hsieh, Ping-Yen; Kunuku, Srinivasu; Lou, Shiu-Cheng; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan; Tai, Nyan-Hwa

    2015-12-16

    An electron field emitter with superior electron field emission (EFE) properties and improved lifetime stability is being demonstrated via the combination of carbon nanotubes and the CH4/N2 plasma grown ultrananocrystalline diamond (N-UNCD) films. The resistance of the carbon nanotubes to plasma ion bombardment is improved by the formation of carbon nanocones on the side walls of the carbon nanotubes, thus forming strengthened carbon nanotubes (s-CNTs). The N-UNCD films can thus be grown on s-CNTs, forming N-UNCD/s-CNTs carbon nanocomposite materials. The N-UNCD/s-CNTs films possess good conductivity of σ = 237 S/cm and marvelous EFE properties, such as low turn-on field of (E0) = 3.58 V/μm with large EFE current density of (J(e)) = 1.86 mA/cm(2) at an applied field of 6.0 V/μm. Moreover, the EFE emitters can be operated under 0.19 mA/cm(2) for more than 350 min without showing any sign of degradation. Such a superior EFE property along with high robustness characteristic of these combination of materials are not attainable with neither N-UNCD films nor s-CNTs films alone. Transmission electron microscopic investigations indicated that the N-UNCD films contain needle-like diamond grains encased in a few layers of nanographitic phase, which enhanced markedly the transport of electrons in the N-UNCD films. Moreover, the needle-like diamond grains were nucleated from the s-CNTs without the necessity of forming the interlayer that facilitate the transport of electrons crossing the diamond-to-Si interface. Both these factors contributed to the enhanced EFE behavior of the N-UNCD/s-CNTs films. PMID:26600097

  20. Deposition temperature dependence of the deep defect density for a-Si:H films grown by electron cyclotron resonance microwave plasma

    NASA Technical Reports Server (NTRS)

    Essick, J. M.; Pool, F. S.; Shing, Y. H.

    1992-01-01

    The dependence on deposition temperature of the mobility gap density of states has been determined for hydrogenated amorphous silicon (a-Si:H) films grown by electron cyclotron resonance (ECR) microwave plasma CVD. A minimum in the integrated deep defect density of 1 x 10 exp 16/cu cm was found to occur at a temperature of approximately 250 C, while an Urbach slope minimum of 52 meV was observed at 175 C under our deposition conditions. Based on these measurements the ECR-grown films were found to be of excellent device quality and comparable to a-Si:H films grown by RF plasma-enhanced CVD.

  1. Photoconductivity in Magnetic Field of p-Type Cadmium - Mercury - Tellurium Films Grown by Liquid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Kostyuchenko, V. Ya.; Protasov, D. Yu.; Andrusov, Yu. B.; Denisov, I. A.; Voitsekhovskii, A. V.

    2016-04-01

    Photoconductivity in a magnetic field is studied for Faraday geometry on the p-type cadmium - mercury -tellurium films grown by liquid-phase epitaxy on cadmium - zinc - tellurium substrates. From the magnetic-field dependence of the photoconductivity signal under the film illumination from the side of the substrate or from the side of free surface, different values of mobility of minority carriers (electrons) are obtained. It is shown that for the mathematical description of the photoconductivity signal in a magnetic field, two types of electrons - "fast" and "slow" electrons, as well as "heavy" holes can be used.

  2. Strain effects in epitaxial Mn{sub 2}O{sub 3} thin film grown on MgO(100)

    SciTech Connect

    Dang Duc Dung; Duong Van Thiet; Duong Anh Tuan; Cho, Sunglae

    2013-05-07

    We report on the epitaxial growth and magnetic properties of Mn{sub 2}O{sub 3} thin films grown on MgO(001) substrate by molecular beam epitaxy. We observed the reduction in binding energy of Mn valence states, the increase in satellite separation up to 12.7 eV, and the smaller band gap of 3.32 eV. In addition, the antiferromagnetic ordering below 90 K in bulk changed to ferrimagnetic up to 175 K. The results were possibly to be explained by a lattice mismatch strain on Mn{sub 2}O{sub 3} film on MgO(001) substrate.

  3. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    SciTech Connect

    Roberts, J.G.

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  4. Room temperature weak ferromagnetism in Sn1-xMnxSe2 2D films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dong, Sining; Liu, Xinyu; Li, Xiang; Kanzyuba, Vasily; Yoo, Taehee; Rouvimov, Sergei; Vishwanath, Suresh; Xing, Huili G.; Jena, Debdeep; Dobrowolska, Margaret; Furdyna, Jacek K.

    2016-03-01

    We discuss growth and magnetic properties of high-quality two dimensional (2D) Sn1-xMnxSe2 films. Thin films of this 2D ternary alloy with a wide range of Mn concentrations were successfully grown by molecular beam epitaxy. Mn concentrations up to x ≈ 0.60 were achieved without destroying the crystal structure of the parent SnSe2 2D system. Most important, the specimens show clear weak ferromagnetic behavior above room temperature, which should be of interest for 2D spintronic applications.

  5. Effect of Sn atoms on incorporation of vacancies in epitaxial Ge1-xSnx film grown at low temperature

    NASA Astrophysics Data System (ADS)

    Kamiyama, Eiji; Nakagawa, Satoko; Sueoka, Koji; Ohmura, Takuma; Asano, Takanori; Nakatsuka, Osamu; Taoka, Noriyuki; Zaima, Shigeaki; Izunome, Koji; Kashima, Kazuhiko

    2014-02-01

    The anomalous increase and decrease in the S-parameters of Doppler broadening spectroscopy in positron annihilation spectroscopy in a narrow range of Sn atom content were detected in a Ge1-xSnx thin film grown by MBE at low temperatures. The increase can be explained in terms of vacancies when the target content of 1.7% Sn atoms is incorporated in a Ge matrix, owing to the binding nature between them. However, the S-parameters were markedly decreased when the target content of Sn atoms in the film grown at the same temperature was 0.1%. These changes in the S-parameters correspond to the carrier concentrations obtained by Hall measurements.

  6. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  7. Defect study in molecular beam epitaxy-grown HgCdTe films with activated and unactivated arsenic

    SciTech Connect

    Izhnin, I. I.; Dvoretsky, S. A.; Mikhailov, N. N.; Varavin, V. S.; Mynbaev, K. D.; Fitsych, O. I.; Pociask-Bialy, M.; Sheregii, E.; Voitsekhovskii, A. V.

    2014-04-28

    A defect study was performed on molecular beam epitaxy-grown HgCdTe films in situ doped with arsenic. Doping was performed from either effusion cell or cracker cell, and studied were both as-grown samples and samples subjected to arsenic activation annealing. Electrical properties of the films were investigated with the use of ion milling as a means of “stirring” defects in the material. As a result of the study, it was confirmed that the most efficient incorporation of electrically active arsenic occurs at the cracking zone temperature of 700 °C. Interaction between arsenic and tellurium during the growth was observed and is discussed in the paper.

  8. Analysis of copper (I) oxide thin films grown in a photo-assisted chemical vapor deposition reactor for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Mohiuddin, Omar H.

    Copper (I) oxide (Cu2O) has enormous potenetial for photovoltaic applications. Cu2O is a p-type semiconductor with a direct band gap of 2.2 eV. When grown on silicon, thin film Cu2O has the potential to increase photovoltaic eciency. Cu2O is a suitable photovoltaic material because it is inexpensive, non-toxic and abundant in the earth's crust. A model was developed based on a stagnation flow reactor with a reduction in activation energy for the precursor decomposition due to the light irradiation to model the light irradiation. The parameters that were tested were substrate temperature (200 to 700° C), gas temperature (100 and 150 °C) and carrier gas flow rate (25 to 100 sccm). The model was tested with a 480 nm and 172 nm light irradiation source and without any light irradiation source. This thesis utilizes a photo assisted chemical vapor deposition reactor to deposit films of Cu2O on silicon. The films were grown with a surface temperature of 700 °C, a gas temperature of 150 °C and an oxygen gas flow rate of 100 sccm. One deposition was done without the use of any light irradiation and another deposition was done with a 480 nm light irradiation source. X-ray diffraction, ellipsometry and transmission electron microscopy (TEM) were used to investigate the light irradiation eect on the lm growth and morphology. When grown with light irradiation, the ellipsometer showed that the film thickness increased to 98 +/- 6 nm from 74 +/- 10 nm, which shows that there is greater uniformity with a higher thickness when grown with light irradiation. The XRD results showed an increase in crystallinity in Cu2O grown with light irradiation, and the TEM results showed the grain sizes double when grown with light irradiation. The UV irradiation has been shown to increase the copper (I) oxide film quality and lm thickness. The model showed that the effect of the light irradiation was maximized at a surface temperature of 400 °C After this temperature the thermal eects become

  9. Co2FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Tuzcuoglu, H.; Gabor, M. S.; Petrisor, T.; Tiusan, C.; Zighem, F.; Chérif, S. M.; Moch, P.

    2014-01-01

    10 nm and 50 nm Co2FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing Ta, while the uniaxial anisotropy field is nearly unaffected by Ta within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with Ta. Finally, the FMR linewidth decreases when increasing Ta, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10-3 and 1.3×10-3 for films of 50 nm thickness annealed at 615 °C grown on MgO and on Si, respectively).

  10. Nucleation and stochiometry dependence of rutile-TiO2 thin films grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Constantin, Costel; Sun, Kai; Feenstra, R. M.

    2008-03-01

    Considerable interest has been shown of late in transition-metal oxides. One case is the titanium dioxide system, which can have applications as a high-k dielectric gate insulator for Si-based devicesootnotetextZ. J. Luo et al., Appl. Phys. Lett. 79, 2803. In this study, rutile-TiO2 thin films were grown on GaN(0001) substrates by oxygen plasma-assisted molecular beam epitaxy. Two sets of films were grown, one in which the initial GaN surface is prepared WITH the pseudo 1x1 Ga-rich surface reconstruction, and the other set, WITHOUT the pseudo 1x1. On top of these two type of surfaces, the rutile-TiO2 thin films were grown at Ts˜ 600 ^oC, and with a thickness ˜ 40 - 50 nm. During growth, reflection high-energy electron diffraction indicated a reversible stoichiometry transition from O-rich to Ti-rich growth. Post-growth x-ray diffraction measurements performed on the samples WITHOUT the GaN pseudo 1x1, show the presence of additional peaks at 2θ = 52.9^o, which implies the existence of additional phases. In addition, the high-resolution transmission electron microscopy performed on these samples show a high degree of disorder, as compared to the samples prepared WITH the pseudo 1x1. Work supported by ONR.

  11. Magnetorefractive effect in the La1-xKxMnO3 thin films grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Bessonov, V. D.; Gan'shina, E. A.; Kaul', A. R.; Korsakov, I. E.; Perov, N. S.; Fetisov, L. Yu.; Yurasov, A. N.

    2014-10-01

    Thin epitaxial La1-хKхMnO3 films were grown using two-stage procedure. Influence of substitution of La3+ ions with K+ ions on the optical and electrical properties of La1-xKxMnO3 films (х=0.05, 0.10, 0.15 и 0.18) has been studied in detail. A noticeable magnetorefractive effect in the films under study was detected in the infrared range. Magnetorefractive effect as well as transverse magneto-optical Kerr effect and magnetoresistance have the maximum in optimally doped sample with x=0.18 corresponding to the highest Curie temperature. The experimental data for compositions close to optimally doped films are in good agreement with the data calculated in the framework of a theory developed for manganites. The resonance-like contribution to magnetoreflection spectra of manganite films has been observed in the vicinity of the phonon bands. It is shown that magnetic and charge inhomogeneities strongly influence on the magneto-optical effects in films. Thin films of La1-xKxMnO3 with the large values of Kerr and magnetorefractive effect are promising magneto-optical material in the infrared range.

  12. Stoichiometry of LaAlO3 films grown on SrTiO3 by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Golalikhani, M.; Lei, Q. Y.; Chen, G.; Spanier, J. E.; Ghassemi, H.; Johnson, C. L.; Taheri, M. L.; Xi, X. X.

    2013-07-01

    We have studied the stoichiometry of epitaxial LaAlO3 thin films on SrTiO3 substrate grown by pulsed laser deposition as a function of laser energy density and oxygen pressure during the film growth. Both x-ray diffraction (θ-2θ scan and reciprocal space mapping) and transmission electron microscopy (geometric phase analysis) revealed a change of lattice constant in the film with the distance from the substrate. Combined with composition analysis using x-ray fluorescence we found that the nominal unit-cell volume expanded when the LaAlO3 film was La-rich, but remained near the bulk value when the film was La-poor or stoichiometric. La excess was found in all the films deposited in oxygen pressures lower than 10-2 Torr. We conclude that the discussion of LaAlO3/SrTiO3 interfacial properties should include the effects of cation off-stoichiometry in the LaAlO3 films when the deposition is conducted under low oxygen pressures.

  13. Nanopatterning and Characterization of Inorganic Films Grown by Atomic Layer Deposition on Silicon and Graphene Substrates

    NASA Astrophysics Data System (ADS)

    Alaboson, Justice M. P.

    The research presented in this dissertation examines the incorporation, nanopatterning and characterization of atomic layer deposited (ALD) films on existing and new materials, motivated by relevance to current Si microelectronics technology and to inform future efforts beyond Si. ALD provides two key benefits. First, the atomic monolayer precision and conformal nature of ALD growth provides an ease of integration with non-planar and complex substrates, and architectures, which is found to be increasingly relevant to microelectronics and nanotechnology in general. In addition, surface templating permits spatially selective ALD growth, enabling three-dimensional surface engineering of materials. Surface templating strategies relying on atomic force microscope (AFM) nanopatterning and self-assembled monolayers are investigated. Control over ALD growth was first demonstrated on Si by tuning the surface hydroxyl concentration via hydroxylation, hydrogenation, and alkylation with organic self-assembled monolayers. The differences in ALD nucleation on these surfaces were exploited to achieve selective ALD by spatially defining hydroxyl regions via AFM field induced oxidation. Graphene, though promising as an electronic material, is highly hydrophobic and inert. Control over surface chemistry and lithographic engineering of graphene is therefore crucial for incorporation with complementary electronic materials. First, surface modification of graphene was demonstrated with conductive AFM (cAFM) nanopatterning. cAFM nanopatterning locally oxidizes epitaxial graphene, with the oxidation kinetics dependent on the surface, interface, and bulk structure of epitaxial graphene. This surface functionalization by cAFM nanopatterning enabled the selective growth of ALD ZnO. Next, non-covalent organic self- assembled monolayers was used to seed the growth of ALD high- k dielectric films on graphene, an important challenge to the realization of graphene-based field effect transistors

  14. Determination of thicknesses of oxide films grown on titanium under argon irradiation by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Do, Ngoc-Long; Garcia-Caurel, Enric; Bérerd, Nicolas; Moncoffre, Nathalie; Gorse-Pomonti, Dominique

    2014-04-01

    In this article we present a study of the oxidation of pure titanium bulk samples under argon ion irradiation at 500 °C under rarefied air. In particular we follow the dependence of the oxide thickness as a function of the energy of argon ions. The novelty of this study consists in the range of ion energy explored, from 1 to 9 MeV. Until very recently it was commonly accepted that metal surfaces were transparent to ion beams in this low energy range (few MeV), and no surface modifications were expected. In a previous paper by the authors of this work, the formation of shallow craters in the surface of titanium was reported as a result of argon ion bombardment with energies of 2, 4 and 9 MeV under the same environmental conditions. We show here that around 3 MeV the oxide growth is unexpectedly enhanced. We think that an interplay of electronic excitations and nuclear ballistic collisions could possibly explain this enhanced oxide growth. We have used spectroscopic visible ultraviolet ellipsometry and XPS to determine the thickness of the oxide layers and characterize their optical properties. From the optical properties of the oxides we observed that for ion energies below 3-4 MeV the oxides show a dielectric-like behavior, whereas for ion energies above 3-4 MeV the oxides show a metal-like behavior. These findings indicate also that ion bombardment in this energy range may change substantially the oxygen-to-titanium ratio in the oxide films grown under irradiation leading to the formation of titanium sub-oxides.

  15. KCl ultra-thin films with polar and non-polar surfaces grown on Si(111)7 × 7

    PubMed Central

    Beinik, Igor; Barth, Clemens; Hanbücken, Margrit; Masson, Laurence

    2015-01-01

    The growth of ultra-thin KCl films on the Si(111)7 × 7 reconstructed surface has been investigated as a function of KCl coverage and substrate temperature. The structure and morphology of the films were characterized by means of scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. Detailed analysis of the atomically resolved STM images of islands grown at room and high temperatures (400 K–430 K) revealed the presence of KCl(001) and KCl(111) islands with the ratio between both structures depending on the growth temperature. At room temperature, the growth of the first layer, which covers the initial Si(111)7 × 7 surface, contains double/triple atomic layers of KCl(001) with a small fraction of KCl(111) islands. The high temperature growth promotes the appearance of large KCl(111) areas, which are built up by three atomic layers. At room and high temperatures, flat and atomically well-defined ultra-thin KCl films can be grown on the Si(111)7 × 7 substrate. The formation of the above mentioned (111) polar films is interpreted as a result of the thermally activated dissociative adsorption of KCl molecules on Si(111)7 × 7, which produces an excess of potassium on the Si surface. PMID:25650038

  16. Orientation and morphology of chloroaluminum phthalocyanine films grown by vapor deposition: Electrical field-induced molecular alignment

    NASA Astrophysics Data System (ADS)

    Basova, Tamara V.; Kiselev, Vitaly G.; Plyashkevich, Vladimir A.; Cheblakov, Pavel B.; Latteyer, Florian; Peisert, Heiko; Chassè, Thomas

    2011-02-01

    The electric field influence on the molecular orientation and the surface morphology of the chloroaluminum(III) phthalocyanine (AlClPc) films has been studied using polarization dependent Raman spectroscopy and atomic force microscopy. The experimental studies were supported by DFT quantum chemical computations of the AlClPc vibrational spectra and 15N isotopic shifts. The electric field of 1.4 kV mm -1 applied parallel to the substrate plane during the physical vapour deposition modified the film structure noticeable. The AlClPc molecules were aligned nearly perpendicular to the substrate surface (the mean tilt angle increased to ˜80° from ˜20° in the films grown without the electric field). The AFM images of the AlClPc films grown in the absence of electric field revealed a predominant amount of crystallites of polyhedron shape, whereas in the case of the applied electric field the surface was more ordered and consisted of the crystallites of a smoother shape.

  17. Semiconductor-insulator transition in VO{sub 2} (B) thin films grown by pulsed laser deposition

    SciTech Connect

    Rúa, Armando; Díaz, Ramón D.; Lysenko, Sergiy; Fernández, Félix E.

    2015-09-28

    Thin films of B-phase VO{sub 2} were grown by pulsed-laser deposition on glass and (100)-cut MgO substrates in a temperature range from 375 to 425 °C and at higher gas pressures than usual for this technique. The films were strongly oriented, with ab-planes parallel to the substrate surface. Detailed study of surface morphology through Atomic Force Microscopy images suggest significant differences in evolution as a function of growth temperature for films on the two types of substrates. Measurements of electrical conductivities through cooling-heating cycles from room temperature to 120 K showed changes of five orders of magnitude, with steeper changes between room temperature and ∼150 K, which corresponds with the extended and reversible phase transition known to occur for this material. At lower temperatures conductivities exhibited Arrhenius behavior, indicating that no further structural change was occurring and that conduction is thermally activated. In this lower temperature range, conductivity of the samples can be described by the near-neighbor hopping model. No hysteresis was found between the cooling and heating braches of the cycles, which is at variance with previous results published for VO{sub 2} (B). This apparent lack of hysteresis for thin films grown in the manner described and the large conductivity variation as a function of temperature observed for the samples suggests this material could be of interest for infrared sensing applications.

  18. Room temperature ferromagnetism in epitaxial Cr{sub 2}O{sub 3} thin films grown on r-sapphire

    SciTech Connect

    Punugupati, Sandhyarani Narayan, Jagdish; Hunte, Frank

    2015-05-21

    We report on the epitaxial growth and magnetic properties of Cr{sub 2}O{sub 3} thin films grown on r-sapphire substrate using pulsed laser deposition. The X-ray diffraction (XRD) (2θ and Φ) and TEM characterization confirm that the films are grown epitaxially. The r-plane (011{sup ¯}2) of Cr{sub 2}O{sub 3} grows on r-plane of sapphire. The epitaxial relations can be written as [011{sup ¯}2] Cr{sub 2}O{sub 3} ‖ [011{sup ¯}2] Al{sub 2}O{sub 3} (out-of-plane) and [1{sup ¯}1{sup ¯}20] Cr{sub 2}O{sub 3} ‖ [1{sup ¯}1{sup ¯}20] Al{sub 2}O{sub 3} (in-plane). The as-deposited films showed ferromagnetic behavior up to 400 K but ferromagnetism almost vanishes with oxygen annealing. The Raman spectroscopy data together with strain measurements using high resolution XRD indicate that ferromagnetism in r-Cr{sub 2}O{sub 3} thin films is due to the strain caused by defects, such as oxygen vacancies.

  19. A TEM investigation of the nucleation, growth and structure of HWE grown lead-tin telluride films

    NASA Astrophysics Data System (ADS)

    Snyman, H. C.; Gouws, G. J.; Muller, R. J.

    1984-12-01

    The epitaxial growth of thin films is usually explained in terms of the interfacial energy of the critical nucleus. In a systematic TEM study of the nucleation and growth of (PbSn)Te on (111) BaF 2 substrates strong evidence is found that the post nucleation stage of recrystallisation and reorientation, rather than nucleation, is dominant in determining the degree of epitaxy. Thin films of various thicknesses were grown, in a hot wall epitaxial (HWE) system, onto (111) BaF 2 substrates at 250°C. Using dark field techniques and microdiffraction the recrystallisation processes and degree of epitaxy were studied as a function of overgrowth thickness. It was found that the degree of epitaxy was critically dependent on the film thickness. Films grown on pre-baked substrates changed from completely polycrystalline at an average thickness of 10 nm to a good epitaxially oriented overgrowth at 150 nm. The driving force for this recrystallisation process is explained in terms of the relative stability of (001) and (111) islands. Electron microscopy and microdiffraction provides direct confirmation of the proposed mechanism and its direction.

  20. Studies of zinc-blende type MnAs thin films grown on InP(001) substrates by XRD

    NASA Astrophysics Data System (ADS)

    Oomae, H.; Irizawa, S.; Jinbo, Y.; Toyota, H.; Kambayashi, T.; Uchitomi, N.

    2013-09-01

    The detailed crystalline structure of molecular beam epitaxially grown MnAs thin films on InP(001) substrate has been investigated using high resolution X-ray diffraction techniques. Reciprocal space mapping of the MnAs/InP(001) samples indicates that the MnAs has a cubic zinc-blende (zb) structure with the epitaxial relationship zb-MnAs[110]|InP[110]. The lattice constant of zb-MnAs is ˜6.06 Å. The MnAs lattice is relaxed and is mosaic-like likely due to large lattice mismatch between the film and InP substrate. The isotropic nature of the magnetic properties supported our conjecture that the MnAs epitaxial film under study has indeed a cubic structure.

  1. Role of native defects in nitrogen flux dependent carrier concentration of InN films grown by molecular beam epitaxy

    SciTech Connect

    Tangi, Malleswararao; Kuyyalil, Jithesh; Shivaprasad, S. M.

    2012-10-01

    We address the carrier concentration, strain, and bandgap issue of InN films grown on c-sapphire at different N-flux by molecular beam epitaxy using x-ray diffraction and x-ray photoelectron spectroscopy. We demonstrate that the strain in InN films arises due to point defects like nitrogen interstitials and nitrogen antisites. We report minimal biaxial strain due to relaxed growth morphology and a minimal hydrostatic strain arising due to interstitial nitrogen atoms being partially compensated by nitrogen antisites. We find that the variation in absorption edge can be attributed to defect induced carrier concentration and that nitrogen interstitials and nitrogen antisites act as donors that yield the respective absorption edge and Moss-Burstein shift. Our studies are a step towards the ability to form low carrier concentration strain-relaxed films and to determine the intrinsic band gap value for this technologically important material.

  2. High indium content InGaN films grown by pulsed laser deposition using a dual-compositing target.

    PubMed

    Shen, Kun-Ching; Wang, Tzu-Yu; Wuu, Dong-Sing; Horng, Ray-Hua

    2012-07-01

    High indium compositions InGaN films were grown on sapphires using low temperature pulse laser deposition (PLD) with a dual-compositing target. This target was used to overcome the obstacle in the InGaN growth by PLD due to the difficulty of target preparation, and provided a co-deposition reaction, where InGaN grains generated from the indium and GaN vapors deposit on sapphire surface and then act as nucleation seeds to promote further InGaN growth. The effects of co-deposition on growth mechanisms, surface morphology, and electrical properties of films were thoroughly investigated and the results clearly show promise for the development of high indium InGaN films using PLD technique with dual-compositing targets. PMID:22772213

  3. Unconventional magnetization of Fe3O4 thin film grown on amorphous SiO2 substrate

    NASA Astrophysics Data System (ADS)

    Yin, Jia-Xin; Liu, Zhi-Guo; Wu, Shang-Fei; Wang, Wen-Hong; Kong, Wan-Dong; Richard, Pierre; Yan, Lei; Ding, Hong

    2016-06-01

    High quality single crystal Fe3O4 thin films with (111) orientation had been prepared on amorphous SiO2 substrate by pulsed laser deposition. The magnetization properties of the films are found to be unconventional. The Verwey transition temperature derived from the magnetization jump is around 140K, which is higher than the bulk value and it can be slightly suppressed by out-plane magnetic field; the out-of-plane magnetization, which is unexpectedly higher than the in-plane value, is also significantly increased as compared with the bulk value. Our findings highlight the unusual magnetization of Fe3O4 thin film grown on the amorphous SiO2 substrate.

  4. Conducting Si-doped γ-Ga2O3 epitaxial films grown by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Oshima, Takayoshi; Matsuyama, Keitaro; Yoshimatsu, Kohei; Ohtomo, Akira

    2015-07-01

    We report structural, electrical, and optical properties of Si-doped γ-Ga2O3 films epitaxially grown on (100) MgAl2O4 substrate by pulsed-laser deposition. The γ-Ga2O3:Si films of a metastable spinel phase had neither secondary phase nor rotation domain. A highly doped film exhibited n-type conductivity with a carrier concentration of 1.8×1019 cm-3 and a Hall mobility of 1.6 cm2 V-1 s-1 at 300 K. Donor activation energy was estimated to be less than 7 meV from nearly temperature-independent transport properties down to 77 K. The successful impurity doping indicates that γ-Ga2O3 can be used as an n-type wide-band-gap semiconductor.

  5. Structure of Stoichiometric and Oxygen-Rich Ultrathin FeO(111) Films Grown on Pd(111)

    SciTech Connect

    Zeuthen, Helene; Kudernatsch, Wilhelmine; Peng, Guowen; Merte, Lindsay R.; Ono, Luis K.; Lammich, Lutz; Bai, Yunhai; Grabow, Lars C.; Mavrikakis, Manos; Wendt, Stefan; Besenbacher, Flemming

    2013-07-25

    Monolayer thin FeO(111) films were grown on Pd(111) and oxidized by atomic oxygen (O). The stoichiometric and oxidized films were studied in detail by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Compared to the previously studied FeO(111)/Pt(111) system, small structural differences were observed for stoichiometric FeO monolayer films. Upon O exposure, the stoichiometric FeO film reconstructs, leading to the formation of new O-rich structures incorporating increasing amounts of additional O atoms. At low O exposures, the STM images exhibit bright features of regularly sized triangular structures assigned to O-adatom dislocation loops. A model of this O-rich structure composed of four-fold O-coordinated Fe atoms is proposed and confirmed by DFT calculations. Furthermore, these O dislocation loops induce the inversion of the FeO film and enclose portions of the film in which the order of the high-symmetry domains is inverted. For higher O exposures, the formation of FeO2–x islands coexisting with O-adatom dislocations and stoichiometric FeO patches was observed. Finally, these FeO2–x islands are reminiscent of the O-rich structures previously reported for FeO supported on Pt(111) and are catalytically active toward CO oxidation.

  6. Engineering the Mechanical Properties of Ultrabarrier Films Grown by Atomic Layer Deposition for the Encapsulation of Printed Electronics

    SciTech Connect

    Bulusu, Anuradha; Singh, Ankit K.; Wang, Cheng-Yin; Dindar, Amir; Fuentes-Hernandez, Canek; Kim, Hyungchul; Cullen, David A.; Kippelen, Bernard; Graham, Samuel

    2015-08-28

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion (CTE) mismatch, elastic mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al2O3)/hafnium oxide (HfO2) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50{degree sign}C/85% RH. Inserting a SiNx layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  7. Structural, electrical, and optical properties of CoxNi1-xO films grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Roffi, Teuku Muhammad; Uchida, Kazuo; Nozaki, Shinji

    2015-03-01

    Thin films of cobalt-nickel oxide (CoxNi1-xO, x=0.01, 0.02, 0.08, 0.17, 0.22, 0.35, 0.56, 0.72) were grown on Al2O3 substrate by atmospheric pressure metalorganic chemical vapor deposition (APMOCVD). The effect of the cobalt composition on the structural, morphological, optical, and electrical properties of the films was investigated. X-ray diffraction (XRD) analysis revealed that all of the films grew with a preferred orientation towards [1 1 1]NiO and a twinned structure. Cobalt was well dispersed in the NiO structure up to x=0.08. CoxNi1-xO alloys were formed from x=0.17 to x=0.22, while phase-separated NiO and CoxNi1-xO formed when x≥0.35. The bandgap of the CoxNi1-xO film was found to decrease with increasing cobalt composition. Four-point probe measurements showed that the resistivity of the film also decreased with increasing cobalt composition, reaching a minimum of 0.006 Ωcm. Hall measurements of the films revealed n-type conductivity. The correlation between the presence of cobalt in different ionization states and the observed decrease in resistivity as well as the type of conductivity in CoxNi1-xO is discussed.

  8. Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

    SciTech Connect

    Bulusu, A.; Singh, A.; Kim, H.; Wang, C. Y.; Dindar, A.; Fuentes-Hernandez, C.; Kippelen, B.; Cullen, D.; Graham, S.

    2015-08-28

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al{sub 2}O{sub 3})/hafnium oxide (HfO{sub 2}) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiN{sub x} layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  9. Engineering the Mechanical Properties of Ultrabarrier Films Grown by Atomic Layer Deposition for the Encapsulation of Printed Electronics

    DOE PAGESBeta

    Bulusu, Anuradha; Singh, Ankit K.; Wang, Cheng-Yin; Dindar, Amir; Fuentes-Hernandez, Canek; Kim, Hyungchul; Cullen, David A.; Kippelen, Bernard; Graham, Samuel

    2015-08-28

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion (CTE) mismatch, elastic mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition.more » We present the impact of architecture on the performance of aluminum oxide (Al2O3)/hafnium oxide (HfO2) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50{degree sign}C/85% RH. Inserting a SiNx layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.« less

  10. Magnetic properties of nano-patterned GaMnAs films grown on ZnCdSe buffer layers

    NASA Astrophysics Data System (ADS)

    Dong, Sining; Li, Xiang; Kanzyuba, Vasily; Yoo, Taehee; Liu, Xinyu; Dobrowolska, Malgorzata; Furdyna, Jacek

    Magnetic semiconductor nanostructures are attracting intense attention, both because of their fundamental physical properties, and because of the promise which they hold for building smaller, faster and more energy-efficient devices. In this study we report successful MBE growth of GaMnAs films on the GaAs (100) substrates with ZnCdSe buffer layers, which results in perpendicular magnetic easy axis in the GaMnAs films. The GaMnAs/ZnCdSe films have been etched into nano-stripe shapes with various widths below 200nm by e-beam lithography, which resulted in a new geometry of interest for perpendicular magnetic recording. Magnetic anisotropy of as-grown GaMnAs films and nano-stripes was then studied by SQUID magnetometry. The results indicate that the GaMnAs films consist of magnetic domains with magnetization normal to the film plane, having rather high coercivety, which survives after nanofabrication. This is also confirmed by the dynamics of the domain motion as shown by AC susceptibility measurements. These findings are of interest for understanding the magnetic anisotropy mechanisms in GaMnAs and its domain structures, as well as for designing of nano-sized spintronic devices which require hard ferromagnetic behavior with perpendicular easy axes. This work was supported by the National Science Foundation Grant DMR1400432.

  11. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    NASA Astrophysics Data System (ADS)

    Sokolov, N. S.; Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Maksimova, K. Yu.; Grunin, A. I.; Bursian, V. E.; Lutsev, L. V.; Tabuchi, M.

    2016-01-01

    Pulsed laser deposition has been used to grow thin (10-84 nm) epitaxial layers of Yttrium Iron Garnet Y3Fe5O12 (YIG) on (111)-oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  12. Titanium Isopropoxide Precursor Volume Consumption as a Function of Temperature for Titanium Dioxide Thin Films Grown by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Constantin, Costel

    2012-02-01

    Atomic layer deposition (ALD) offers tremendous opportunities for controlling material synthesis on an atomic level and for creating nanolayers with unique new functionalities. ALD is a chemical gas phase thin film deposition method based on alternating surface reactions that employs two or more precursors. ALD is often used for growth of high k dielectric constant oxide films. Titanium dioxide material have a k value of 80, and a band gap of ˜ 3 eV, and due to strong oxidizing properties thin films coated on construction materials and glass have fog proof, and self cleaning properties. Our ALD reactor employs liquid Titanium Isopropoxide [TiOCH(CH3)24] as a metal precursor and distilled H2O as an oxygen source to grow thin films of titanium dioxide [TiO2] on silicon [Si], gallium nitride [GaN], and Aluminium foil [Al-foil] substrates. Titanium Isopropoxide exhibit a vapor pressure surge above 40^o C and we report the volume precursor consumption as a function of precursor temperature and thin film thickness for ALD grown TiO2 on Si, GaN, and Al-foil substrates. We will also present dielectric constants of the TiO2 thin films measured with a variable angle spectroscopic ellipsometer.

  13. Comparison of morphology evolution of Ge(001) homoepitaxial films grown by pulsed laser deposition and molecular-beam epitaxy

    SciTech Connect

    Shin Byungha; Leonard, John P.; McCamy, James W.; Aziz, Michael J.

    2005-10-31

    Using a dual molecular-beam epitaxy (MBE)-pulsed laser deposition (PLD) ultrahigh vacuum chamber, we have conducted the first experiments under identical thermal, background, and surface preparation conditions to compare Ge(001) homoepitaxial growth morphology in PLD and MBE. We find that in PLD with low kinetic energy and in MBE the film morphology evolves in a similar fashion: initially irregularly shaped mounds form, followed by pyramidal mounds with edges of the square-base along the <100> directions; the film roughness and mound separation increase with film thickness. In PLD with high kinetic energy, well-defined pyramidal mounds are not observed and the morphology rather resembles that of an ion-etched Ge(001) surface. The areal feature density is higher for PLD films than for MBE films grown at the same average growth rate and temperature. Furthermore, the dependence upon film thickness of roughness and feature separation differ for PLD and MBE. We attribute these differences to the higher yield of defect generation by energetic species in PLD.

  14. Magnetic properties of Sm-Co thin films grown on MgO(100) deposited from a single alloy target

    SciTech Connect

    Verhagen, T. G. A.; Boltje, D. B.; Ruitenbeek, J. M. van; Aarts, J.

    2014-08-07

    We have grown epitaxial Sm-Co thin films by sputter deposition from a single alloy target with a nominal SmCo{sub 5} composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo{sub 5}-like to a Sm{sub 2}Co{sub 7}-like phase. The composition, crystal structure, morphology, and magnetic properties of these films have been determined using Rutherford Backscattering, X-ray diffraction, and magnetization measurements. We find that we can grow films with, at room temperature, coercive fields as high as 3.3 T, but with a remanent magnetization which is lower than can be expected from the texturing. This appears to be due to the Sm content of the films, which is higher than expected from the content of the target, even at the lowest possible sputtering pressures. Moreover, we find relatively large variations of film properties using targets of nominally the same composition. At low temperatures, the coercive fields increase, as expected for these hard magnets, but in the magnetization, we observe a strong background signal from the paramagnetic impurities in the MgO substrates.

  15. Engineering the mechanical properties of ultrabarrier films grown by atomic layer deposition for the encapsulation of printed electronics

    NASA Astrophysics Data System (ADS)

    Bulusu, A.; Singh, A.; Wang, C. Y.; Dindar, A.; Fuentes-Hernandez, C.; Kim, H.; Cullen, D.; Kippelen, B.; Graham, S.

    2015-08-01

    Direct deposition of barrier films by atomic layer deposition (ALD) onto printed electronics presents a promising method for packaging devices. Films made by ALD have been shown to possess desired ultrabarrier properties, but face challenges when directly grown onto surfaces with varying composition and topography. Challenges include differing nucleation and growth rates across the surface, stress concentrations from topography and coefficient of thermal expansion mismatch, elastic constant mismatch, and particle contamination that may impact the performance of the ALD barrier. In such cases, a polymer smoothing layer may be needed to coat the surface prior to ALD barrier film deposition. We present the impact of architecture on the performance of aluminum oxide (Al2O3)/hafnium oxide (HfO2) ALD nanolaminate barrier films deposited on fluorinated polymer layer using an optical calcium (Ca) test under damp heat. It is found that with increasing polymer thickness, the barrier films with residual tensile stress are prone to cracking resulting in rapid failure of the Ca sensor at 50 °C/85% relative humidity. Inserting a SiNx layer with residual compressive stress between the polymer and ALD layers is found to prevent cracking over a range of polymer thicknesses with more than 95% of the Ca sensor remaining after 500 h of testing. These results suggest that controlling mechanical properties and film architecture play an important role in the performance of direct deposited ALD barriers.

  16. Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures.

    PubMed

    Wang, Wenliang; Yang, Weijia; Lin, Yunhao; Zhou, Shizhong; Li, Guoqiang

    2015-01-01

    2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices. PMID:26563573

  17. Small high directivity ferrite antennas

    NASA Astrophysics Data System (ADS)

    Wright, T. M. B.

    A centimeter-wavelength antenna of millimetric dimensions, which uses the intrinsic angular sensitivity of ferrites, is described, with an emphasis on the modification of the material's permeability. The construction of both the ferrite film lens antenna and the ferrite film cassegrain antenna are detailed; both can be devised in a number of configurations for appropriate beam positioning and rf filtering. The antenna design, discussed primarily in the context of smart missiles, electronic warfare, and satellite systems, presents the possibility of magnetically switching between the transmit and receive modes within the antenna structure itself. Finally, it is noted that for a simple 2-dipole array the angular resolution can be two orders of magnitude higher than with the conventional techniques.

  18. The effect of deposition parameters on the phase of TiO2 films grown by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lim, Ji Chon; Song, Kyu Jeong; Park, Chan

    2014-12-01

    TiO2 thin films were deposited on Si substrates by using conventional radio-frequency (RF) magnetron sputtering with either metallic Ti or TiO2 targets, and the effect of the deposition parameters (substrate temperature ( T s ), RF sputtering power, gas flow ratio of O2/(Ar+O2) and deposition time) on the phase of the film was investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to obtain information on the phase of the films and on the surface image/thickness of films, respectively. TiO2 films deposited at a T s higher than 300 °C by using a metallic Ti target showed the dominant presence of the rutile phase. For films grown at a constant T s of 300 °C with different gas flow ratios of O2/(Ar+O2), the amount of the rutile phase gradually decreased as the oxygen gas flow was decreased. The anatase phase, however, was formed when the O2/(Ar+O2) was 0.2. On the other hand, for TiO2 films deposited at T s 's between 50 °C and 200 °C with an O2/(Ar+O2) of 0.1 by using a TiO2 target, both the anatase and the rutile phases gradually decreased as the T s was increased. For TiO2 films deposited with various gas flow ratios of O2/(Ar+O2) between 0 and 0.4 at a constant T s of 200 °C by using a TiO2 target, the anatase phase gradually decreased, but the rutile phase gradually increased, as the gas flow ratio was increased.

  19. Electrical resistivity of CuAlMo thin films grown at room temperature by dc magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Birkett, Martin; Penlington, Roger

    2016-07-01

    We report on the thickness dependence of electrical resistivity of CuAlMo films grown by dc magnetron sputtering on glass substrates at room temperature. The electrical resistance of the films was monitored in situ during their growth in the thickness range 10–1000 nm. By theoretically modelling the evolution of resistivity during growth we were able to gain an insight into the dominant electrical conduction mechanisms with increasing film thickness. For thicknesses in the range 10–25 nm the electrical resistivity is found to be a function of the film surface roughness and is well described by Namba’s model. For thicknesses of 25–40 nm the experimental data was most accurately fitted using the Mayadas and Shatkes model which accounts for grain boundary scattering of the conduction electrons. Beyond 40 nm, the thickness of the film was found to be the controlling factor and the Fuchs–Sonheimer (FS) model was used to fit the experimental data, with diffuse scattering of the conduction electrons at the two film surfaces. By combining the Fuchs and Namba (FN) models a suitable correlation between theoretical and experimental resistivity can be achieved across the full CuAlMo film thickness range of 10–1000 nm. The irreversibility of resistance for films of thickness >200 nm, which demonstrated bulk conductivity, was measured to be less than 0.03% following subjection to temperature cycles of ‑55 and +125 °C and the temperature co-efficient of resistance was less than ±15 ppm °C‑1.

  20. Magnetoelastic coupling in epitaxial cobalt ferrite/barium titanate heterostructures

    NASA Astrophysics Data System (ADS)

    Gräfe, Joachim; Welke, Martin; Bern, Francis; Ziese, Michael; Denecke, Reinhard

    2013-08-01

    Ultra-thin cobalt ferrite films have been synthesised on ferroelectric barium titanate crystals. The cobalt ferrite films exhibit a magnetic response to strain induced by structural changes in the barium titanate substrate, suggesting a pathway to multiferroic coupling. These structural changes are achieved by heating through the phase transition temperatures of barium titanate. In addition the ferromagnetic signal of the substrate itself is taken into account, addressing the influence of impurities or defects in the substrate. The cobalt ferrite/barium titanate heterostructure is a suitable oxidic platform for future magnetoelectric applications with an established ferroelectric substrate and widely tuneable magnetic properties by changing the transition metal in the ferrite film.

  1. Temperature dependent electrical properties of polyaniline film grown on paper through aniline vapor polymerization

    NASA Astrophysics Data System (ADS)

    Deb, K.; Bhowmik, K. L.; Bera, A.; Chattopadhyay, K. K.; Saha, B.

    2016-05-01

    Polyaniline thin film has been prepared on paper by aniline vapor deposition technique. Ferric chloride has been used as polymerizing agent in this approach. The prepared films were studied through electrical resistivity and optical properties measurements. The electrical resistivity of the polyaniline film shows significant temperature dependence. The resistance sharply falls with the increase in temperature. The optical absorbance measurements shows characteristics absorbance peak indicating the formation of conducting emeraldine salt form of polyaniline. The optical energy band gap of the film was calculated from the transmittance spectra. The optical energy band gap and electrical conductivity of the polyaniline film is well suited for their applications in electronic devices.

  2. Synthesis and properties of ZnS-EuS films grown from volatile complex compounds

    SciTech Connect

    Bessergenev, V.G.; Ivanova, E.N.; Kovalevskaya, Y.A.

    1997-10-01

    Deposition and characterization of films of ZnS, EuS and ZnS:Eu are described. The films have been prepared by chemical vapor deposition using new volatile complex compounds, dithiocarbamates of Zn and Eu, as precursors. Characterization includes X-ray diffraction, chemical analysis of the film composition, Raman spectroscopy, ellipsometry, and spectrophotometry. The spatial chemical homogeneity of the films has been determined using a recently developed method of differential dissolution and found to be uniform. Doping of ZnS by Eu with dopant concentration up to 0.3 at.% has been achieved. Effects of Eu doping on structural and optical properties of the films are presented.

  3. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    NASA Astrophysics Data System (ADS)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2016-07-01

    To study the role of novel Gd_2 Zr_2 O_7 /Ce_{0.9} La_{0.1} O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2 Cu_3 O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  4. Production and characterization of Nd,Cr:GSGG thin films on Si(001) grown by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Willmott, P. R.; Manoravi, P.; Holliday, K.

    Nd,Cr:Gd3Sc2Ga3O12 (GSGG) thin films have been produced for the first time. They were grown on Si(001) substrates at 650 °C by pulsed laser ablation at 248 nm of a crystalline Nd,Cr:GSGG target rod. The laser plume was analyzed using time-of-flight quadrupole mass spectroscopy, and consisted of elemental and metal oxide fragments with kinetic energies typically in the range 10 to 40 eV, though extending up to 100 eV. Although films deposited in vacuum using laser fluences of 0.8+/-0.1 Jcm-2 reproduced the Nd,Cr:GSGG bulk stoichiometry, those deposited using fluences above 3 Jcm-2 resulted in noncongruent material transfer and were deficient in Ga and Cr. Attempts to grow films using synchronized oxygen or oxygen/argon pulses yielded mixed oxide phases. Under optimal growth conditions, the films were heteroepitaxial, with GSGG(001)[100]∥Si(001)[100], and exhibited Volmer-Weber-type growth. Room-temperature emission spectra of the films suggest efficient non-radiative energy transfer between Cr3+ and Nd3+ ions, similar to that of the bulk crystal.

  5. Polarization and lattice strains in epitaxial BaTiO3 films grown by high-pressure sputtering

    NASA Astrophysics Data System (ADS)

    Petraru, A.; Pertsev, N. A.; Kohlstedt, H.; Poppe, U.; Waser, R.; Solbach, A.; Klemradt, U.

    2007-06-01

    High-quality BaTiO3 films with thicknesses ranging from 2.9to175nm were grown epitaxially on SrRuO3-covered (001)-oriented SrTiO3 substrates by high-pressure sputtering. The crystal structure of these films was studied by conventional and synchrotron x-ray diffraction. The in-plane and out-of-plane lattice parameters were determined as a function of film thickness by x-ray reciprocal space mapping around the asymmetric (1¯03) Bragg reflection. BaTiO3 films were found to be fully strained by the SrTiO3 substrate up to a thickness of about 30nm. Ferroelectric capacitors were then fabricated by depositing SrRuO3 top electrodes, and the polarization-voltage hysteresis loops were recorded at the frequencies 1-30kHz. The observed thickness effect on the lattice parameters and polarization in BaTiO3 films was analyzed in the light of strain and depolarizing-field effects using the nonlinear thermodynamics theory. The theoretical predictions are in reasonable agreement with the measured thickness dependences, although the maximum experimental values of the spontaneous polarization and the out-of-plane lattice parameter exceed the theoretical estimates (43μC /cm2 vs 35μC/cm2 and 4.166Å vs 4.143Å). Possible origins of the revealed discrepancy between theory and experiment are discussed.

  6. Structural study and ferroelectricity of epitaxial BaTiO3 films on silicon grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Mazet, L.; Bachelet, R.; Louahadj, L.; Albertini, D.; Gautier, B.; Cours, R.; Schamm-Chardon, S.; Saint-Girons, G.; Dubourdieu, C.

    2014-12-01

    Integration of epitaxial complex ferroelectric oxides such as BaTiO3 on semiconductor substrates depends on the ability to finely control their structure and properties, which are strongly correlated. The epitaxial growth of thin BaTiO3 films with high interfacial quality still remains scarcely investigated on semiconductors; a systematic investigation of processing conditions is missing although they determine the cationic composition, the oxygen content, and the microstructure, which, in turn, play a major role on the ferroelectric properties. We report here the study of various relevant deposition parameters in molecular beam epitaxy for the growth of epitaxial tetragonal BaTiO3 thin films on silicon substrates. The films were grown using a 4 nm-thick epitaxial SrTiO3 buffer layer. We show that the tetragonality of the BaTiO3 films, the crystalline domain orientations, and SiO2 interfacial layer regrowth strongly depend on the oxygen partial pressure and temperature during the growth and on the post-deposition anneal. The ferroelectricity of the films, probed using piezoresponse force microscopy, is obtained in controlled temperature and oxygen pressure conditions with a polarization perpendicular to the surface.

  7. Structural, morphological, and optoelectrical characterization of Bi2S3 thin films grown by co-evaporation

    NASA Astrophysics Data System (ADS)

    Mesa, F.; Arredondo, C. A.; Vallejo, W.

    2016-03-01

    This work presents the results of synthesis and characterization of polycrystalline n-type Bi2S3 thin films. The films were grown through a chemical reaction from co-evaporation of their precursor elements in a soda-lime glass substrate. The effect of the experimental conditions on the optical, morphological structural properties, the growth rate, and the electrical conductivity (σ) was studied through spectral transmittance, X-ray diffraction (XRD), atomic force microscopy (AFM) and σ versus T measurements, respectively. The results showed that the films grow only in the orthorhombic Bi2S3 bismuthinite phase. It was also found that the Bi2S3 films present an energy band gap (Eg) of about 1.38 eV. In addition to these results, the electrical conductivity of the Bi2S3 films was affected by both the transport of free carriers in extended states of the conduction band and for variable range hopping transport mechanisms, each one predominating in a different temperature range.

  8. Oxygen-dependent phosphorus networking in ZnO thin films grown by low temperature rf sputtering

    NASA Astrophysics Data System (ADS)

    Pugel, D. Elizabeth; Vispute, R. D.; Hullavarad, S. S.; Venkatesan, T.; Varughese, B.

    2007-03-01

    Radio frequency (rf) sputtered films of 10at.% P2O5-doped zinc oxide (ZnO) were deposited at temperatures (Td) below the sublimation point of P2O5 (Td<350°C) and at a range of oxygen pressures p(O2). Ultraviolet-visible optical transmission measurements, x-ray photoelectron spectroscopy (XPS), and x-ray diffraction were used to examine the effects of p(O2) during deposition on the band gap and on the bonding behavior of phosphorus. At both deposition temperatures studied (room temperature with unintentional heating and 125°C), an increase in phosphorus concentration with increasing p(O2) was observed. However, the dependence of the band gap behavior on p(O2) was observed to be dramatically different for the two deposition temperatures: room-temperature-deposited films show a redshift while films deposited at 125°C show a blueshift. Analysis of the oxygen 1s XPS peak shows a progressive formation of nonbridging (Zn-O-P) bond networks for room temperature films, whereas films grown at 125°C show increased (P-O-P) bond networks with increasing p(O2). This indicates that a small degree of thermal activation considerably modifies the bonding behavior of phosphorus in ZnO. Implications of these results for the use of phosphorus as a p-type dopant for ZnO are discussed.

  9. Annealing effect on the optical and electrical properties of ZnO thin film grown on inp substrate

    NASA Astrophysics Data System (ADS)

    Ghosh, K.; Majumdar, S.; Bhunia, S.

    2012-06-01

    ZnO thin films have been fabricated by sublimation process on indium phosphide (InP) (111) substrates. These films were annealed at various temperatures in order to study the annealing effect on the optical and electrical properties of ZnO thin film grown on InP substrate. From photoluminescence study it was observed that the near band edge peak, i.e., excitonic peak, decreases drastically with the increase of annealing temperature. This indicates that at higher annealing temperature the recombinations are taking place in non-radiative way. It was also observed that the defect related broad peak around 500 nm, i.e., green luminescence peak for ZnO, increases at higher annealing temperatures. As O vacancy is responsible for the green luminescence, so more oxygen vacancies have been introduced at higher annealing temperatures. The electrical characterization of ZnO film revealed that the resistivity of the film increases with the increasing annealing temperatures. Ionised Zn interstitials contribute to carrier concentration in ZnO. Evaporation of Zn interstitials at higher annealing temperatures may have decreased the carrier concentration which in tern had increased the resistivity.

  10. Microstructural and conductivity comparison of Ag films grown on amorphous TiO2 and polycrystalline ZnO

    SciTech Connect

    Dannenberg, Rand; Stach, Eric; Glenn, Darin; Sieck, Peter; Hukari, Kyle

    2001-03-26

    8 nm thick Ag films were sputter deposited onto amorphous TiO{sub 2} underlayers 25 nm thick, and also amorphous TiO{sub 2} (25 nm)/ZnO (5 nm) multiunderlayers. The substrates were back-etched Si with a 50 nm thick LPCVD Si{sub 3}N{sub 4} electron transparent membrane. The ZnO, sputtered onto amorphous TiO{sub 2}, formed a continuous layer with a grain size of 5 nm in diameter, on the order of the film thickness. There are several microstructural differences in the Ag dependent on the underlayers, revealed by TEM. First a strong {l_brace}0001{r_brace} ZnO to {l_brace}111{r_brace} Ag fibre-texture relationship exists. On TiO{sub 2} the Ag microstructure shows many abnormal grains whose average diameter is about 60-80 nm, whereas the films on ZnO show few abnormal grains. The background matrix of normal grains on the TiO{sub 2} is roughly 15 nm, while the normal grain size on the ZnO is about 25 nm. Electron diffraction patterns show that the film on ZnO has a strong {l_brace}111{r_brace} orientation, and dark field images with this diffraction condition have a grain size of about 30 nm. In a region near the center of the TEM grid where there is the greatest local heating during deposition, Ag films grown on amorphous TiO{sub 2} are discontinuous, whereas on ZnO, the film is continuous. When films 8 nm films are grown on solid glass substrates, those with ZnO underlayers have sheet resistances of 5.68 {Omega}/, whereas those on TiO{sub 2} are 7.56 {Omega}/, and when 16 nm thick, the corresponding sheet resistances are 2.7 {Omega}/ and 3.3 {Omega}/. The conductivity difference is very repeatable. The improved conductivity is thought to be a combined effect of reduced grain boundary area per unit volume, the predominance of low grain boundary resistivity Coincidence Site Lattice boundaries from the Ag {l_brace}111{r_brace} orientation, and Ag planarization on ZnO resulting in less groove formation on deposition, concluded from atomic force microscopy.

  11. Ionization potentials of transparent conductive indium tin oxide films covered with a single layer of fluorine-doped tin oxide nanoparticles grown by spray pyrolysis deposition

    SciTech Connect

    Fukano, Tatsuo; Motohiro, Tomoyoshi; Ida, Takashi; Hashizume, Hiroo

    2005-04-15

    Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7 nm in average size show an ionization potential of 5.01 eV, as compared with {approx}4.76 and {approx}4.64 eV in ITO and FTO films, respectively, which decreases as the FTO particle size increases. The ionization potentials are practically invariant against oxidation and reduction treatments, promising a wide application of the films to transparent conducting oxide electrodes in organic electroluminescent devices and light-emitting devices of high efficiencies.

  12. Ionization potentials of transparent conductive indium tin oxide films covered with a single layer of fluorine-doped tin oxide nanoparticles grown by spray pyrolysis deposition

    NASA Astrophysics Data System (ADS)

    Fukano, Tatsuo; Motohiro, Tomoyoshi; Ida, Takashi; Hashizume, Hiroo

    2005-04-01

    Indium tin oxide (ITO) films deposited with single layers of monodispersive fluorine-doped tin oxide (FTO) nanoparticles of several nanometers in size were grown on glass substrates by intermittent spray pyrolysis deposition using conventional atomizers. These films have significantly higher ionization potentials than the bare ITO and FTO films grown using the same technique. The ITO films covered with FTO particles of 7nm in average size show an ionization potential of 5.01eV, as compared with ˜4.76 and ˜4.64eV in ITO and FTO films, respectively, which decreases as the FTO particle size increases. The ionization potentials are practically invariant against oxidation and reduction treatments, promising a wide application of the films to transparent conducting oxide electrodes in organic electroluminescent devices and light-emitting devices of high efficiencies.

  13. Structure disorder degree of polysilicon thin films grown by different processing: Constant C from Raman spectroscopy

    SciTech Connect

    Wang, Quan; Zhang, Yanmin; Hu, Ran; Ren, Naifei; Ge, Daohan

    2013-11-14

    Flat, low-stress, boron-doped polysilicon thin films were prepared on single crystalline silicon substrates by low pressure chemical vapor deposition. It was found that the polysilicon films with different deposition processing have different microstructure properties. The confinement effect, tensile stresses, defects, and the Fano effect all have a great influence on the line shape of Raman scattering peak. But the effect results are different. The microstructure and the surface layer are two important mechanisms dominating the internal stress in three types of polysilicon thin films. For low-stress polysilicon thin film, the tensile stresses are mainly due to the change of microstructure after thermal annealing. But the tensile stresses in flat polysilicon thin film are induced by the silicon carbide layer at surface. After the thin film doped with boron atoms, the phenomenon of the tensile stresses increasing can be explained by the change of microstructure and the increase in the content of silicon carbide. We also investigated the disorder degree states for three polysilicon thin films by analyzing a constant C. It was found that the disorder degree of low-stress polysilicon thin film larger than that of flat and boron-doped polysilicon thin films due to the phase transformation after annealing. After the flat polysilicon thin film doped with boron atoms, there is no obvious change in the disorder degree and the disorder degree in some regions even decreases.

  14. Nanostructured and wide bandgap CdS:O thin films grown by reactive RF sputtering

    SciTech Connect

    Islam, M. A.; Rahman, K. S.; Haque, F.; Rashid, M. J.; Akhtaruzzaman, M.; Sopian, K.; Sulaiman, Y.; Amin, N.

    2015-05-15

    In this study, CdS:O thin films were prepared from a 99.999% CdS target by reactive sputtering in a Ar:O{sub 2} (99:1) ambient with different RF power at room temperature. The deposited films were studied by means of XRD, SEM, EDX, Hall Effect and UV-Vis spectrometry. The incorporations of O{sub 2} into the films were observed to increase with the decrease of deposition power. The cryatallinity of the films were reduced, whereas the band gaps of the films were increased by the increase of O{sub 2} content on the films. The films were found in nano-structured grains with a compact surface. It has been seen that the highest carrier density is observed in the film with O{sub 2} at.% 21.10, while the values decreased with the further increase or decrease of O{sub 2} content on the films; indicating that specific amount of donor like O{sub 2} atoms substitute to the S atoms can improve the carrier density of the CdS:O thin film.

  15. Ferroelectric properties and crystalline structures of BaMgF{sub 4} thin films grown on Pt(111)/SiO{sub 2}/Si(100)

    SciTech Connect

    Moriwaki, Masashi; Aizawa, Koji; Tokumitsu, Eisuke; Ishiwara, Hiroshi

    1997-07-01

    Crystalline quality and ferroelectric properties of (120)-oriented BaMgF{sub 4}(BMF) films grown on Pt(111)/SiO{sub 2}/Si(100) and n-Si(111) substrates have been investigated. The BaMgF{sub 4} films grown on Pt(111) have large and flat grains, while the films on Si(111) have small grains. The C-V curve of BaMgF{sub 4}/Pt(111)/SiO{sub 2}/Si(100) diodes showed a hysteresis loop with a memory window of 3.8V.

  16. X-ray analysis of strain distribution in two-step grown epitaxial SrTiO{sub 3} thin films

    SciTech Connect

    Panomsuwan, Gasidit E-mail: g.panomsuwan@gmail.com; Takai, Osamu; Saito, Nagahiro

    2014-08-04

    Epitaxial SrTiO{sub 3} (STO) thin films were grown on (001)-oriented LaAlO{sub 3} (LAO) substrates using a two-step growth method by ion beam sputter deposition. An STO buffer layer was initially grown on the LAO substrate at a low temperature of 150 °C prior to growing the STO main layer at 750 °C. The thickness of the STO buffer layer was varied at 3, 6, and 10 nm, while the total film thickness was kept constant at approximately 110 nm. According to x-ray structural analysis, we show that the STO buffer layer plays an essential role in controlling the strain in the STO layer grown subsequently. It is found that the strains in the STO films are more relaxed with an increase in buffer layer thickness. Moreover, the strain distribution in two-step grown STO films becomes more homogeneous across the film thickness when compared to that in directly grown STO film.

  17. Anomalous thickness-dependent strain states and strain-tunable magnetization in Zn-doped ferrite epitaxial films

    NASA Astrophysics Data System (ADS)

    Yang, Y. J.; Yang, M. M.; Luo, Z. L.; Hu, C. S.; Bao, J.; Huang, H. L.; Zhang, S.; Wang, J. W.; Li, P. S.; Liu, Y.; Zhao, Y. G.; Chen, X. C.; Pan, G. Q.; Jiang, T.; Liu, Y. K.; Li, X. G.; Gao, C.

    2014-05-01

    A series of ZnxFe3-xO4 (ZFO, x = 0.4) thin films were epitaxially deposited on single-crystal (001)-SrTiO3 (STO) substrates by radio frequency magnetron sputtering. The anomalous thickness-dependent strain states of ZFO films were found, i.e., a tensile in-plane strain exists in the thinner ZFO film and which monotonously turns into compressive in the thicker films. Considering the lattice constant of bulk ZFO is bigger than that of STO, this strain state cannot be explained in the conventional framework of lattice-mismatch-induced strain in the hetero-epitaxial system. This unusual phenomenon is proposed to be closely related to the Volmer-Weber film growth mode in the thinner films and incorporation of the interstitial atoms into the island's boundaries during subsequent epitaxial growth of the thicker films. The ZFO/STO epitaxial film is found in the nature of magnetic semiconductor by transport measurements. The in-plane magnetization of the ZFO/STO films is found to increase as the in-plane compressive strain develops, which is further proved in the (001)-ZFO/PMN-PT film where the film strain state can be in situ controlled with applied electric field. This compressive-strain-enhanced magnetization can be attributed to the strain-mediated electric-field-induced in-plane magnetic anisotropy field enhancement. The above results indicate that strain engineering on magnetic oxide semiconductor ZFO films is promising for novel oxide-electronic devices.

  18. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Chen, W. J.; Yang, C. S.; Tsai, Y. H.; Wang, H. H.; Chen, R. H.; Shen, J. L.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 °C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  19. Surface morphology of grown thin films of the quasi one-dimensional organic conductor TTF-TCNQ studied by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.; Caro, J.; Figueras, A.; Gorostiza, P.; Sanz, F.

    1998-01-01

    Thin films of the quasi one-dimensional organic conductor TTF-TCNQ grown on KCl (001) substrates by Chemical Vapor Deposition has been analyzed with Atomic Force Microscopy. The films are polycrystalline, composed of microcrystals with rectangular shape with the c∗ crystallographic axis perpendicular to the substrate. The stepped surface morphology of the microcrystals has been studied. The growth of the films is strongly dominated by an oriented nucleation and the one-dimensional nature of the compound.

  20. Microstructure investigation and magnetic study of permalloy thin films grown by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Lamrani, Sabrina; Guittoum, Abderrahim; Schäfer, Rudolf; Pofahl, Stefan; Neu, Volker; Hemmous, Messaoud; Benbrahim, Nassima

    2016-06-01

    We study the effect of thickness on the structural and magnetic properties of permalloy thin films, evaporated on glass substrate. The films thicknesses range from 16 to 90 nm. From X-ray diffraction spectra analysis, we show that the thinner films present a "1,1,1" preferred orientation. However, the thicker films exhibit a random orientation. The grains size increases and the lattice parameter decreases with increasing thickness. The magnetic force microscopy observations display cross-tie walls features only for the two thicker films (60 and 90 nm thick films). The magnetic microstructure, carried out by Kerr microscopy technique, shows the presence of magnetic domains changing with the direction of applied magnetic field. The coercive field, Hc, was found to decrease from 6.5 for 16 to 1.75 Oe for 90 nm. All these results will be discussed and correlated.

  1. Post-annealing effects on ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Um, Youngho

    2015-09-01

    Herein, the structural, morphological, and optical properties of zinc sulfide (ZnS) thin films deposited via the chemical bath deposition method are reported. These films were deposited on soda-lime glass (SLG) substrates by using ZnSO4, thiourea, and 25% ammonia at 90 °C. The effect of changing the annealing temperature from 100 °C to 300 °C on the properties of the ZnS thin films was investigated. X-ray diffraction (XRD) patterns showed that the ZnS thin film annealed at 100 °C had an amorphous structure; however, as the annealing temperature was increased, the crystalline quality of the thin film was enhanced. Moreover, transmission measurements showed that the optical transmittance was about 80% for wavelengths above 500 nm. The band gap energy (E g ) value of the film annealed at 300 °C was decreased to about 3.82 eV.

  2. Magnetic and structural properties of CoFe 2O 4 thin films synthesized via a sol-gel process

    NASA Astrophysics Data System (ADS)

    dos S. Duque, J. G.; Macêdo, M. A.; Moreno, N. O.; Lopez, J. L.; Pfanes, H.-D.

    2001-05-01

    Using a sol-gel process having the coconut water as a precursor of organic chain, we synthesized thin films of cobalt ferrite. The films were characterized by using a SQUID magnetometer, an X-ray diffractometer, an X-ray spectrophotometer, Mössbauer spectroscopy and atomic force microscope. Co ferrite films annealed at 500°C for 2 h show grain sizes between 10 and 20 nm, grown as single-phase spinel structure and exhibit high coercivity and a moderate saturation magnetization (above 30 kOe).

  3. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    NASA Astrophysics Data System (ADS)

    Kundu, Asish K.; Menon, Krishnakumar S. R.

    2016-05-01

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  4. Thermally Driven Stability of Octadecylphosphonic Acid Thin Films Grown on SS316L

    PubMed Central

    Lim, Min Soo; Smiley, Katelyn J.; Gawalt, Ellen S.

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF and water flushes while untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a three hour period while the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface. PMID:20648546

  5. Investigation of thin films of organic-based magnets grown by physical vapor deposition

    SciTech Connect

    Kao, C. Y.; Lu, Y.; Li, B.; Yoo, J.-W.; Epstein, A. J.

    2014-10-06

    Thin films of organic-based magnet, V[TCNE]{sub x} (TCNE: tetracyanoethylene), were deposited by physical vapor deposition (PVD) based reactive evaporation. The growth conditions were studied in detail. A saturated composition of V[TCNE]{sub ∼1.9} was determined by optimizing the growth condition. Two sets of films with different V to TCNE ratios were characterized. Both films were magnetic ordered up to 400 K and held coercive field of 60 Oe at room temperature. With the presence of excess vanadium within the film, the increase of defects created by PVD results in significant change in electronic property.

  6. Thermally driven stability of octadecylphosphonic acid thin films grown on SS316L.

    PubMed

    Lim, Min Soo; Smiley, Katelyn J; Gawalt, Ellen S

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF, and water flushes, whereas untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a 3-hour period, whereas the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface. PMID:20648546

  7. LPE grown LSO:Tb scintillator films for high-resolution X-ray imaging applications at synchrotron light sources

    NASA Astrophysics Data System (ADS)

    Cecilia, A.; Rack, A.; Douissard, P.-A.; Martin, T.; Dos Santos Rolo, T.; Vagovič, P.; Hamann, E.; van de Kamp, T.; Riedel, A.; Fiederle, M.; Baumbach, T.

    2011-08-01

    Within the project ScinTAX of the 6th framework program (FP6) of the European Commission (SCINTAX—STRP 033 427) we have developed a new thin single crystal scintillator for high-resolution X-ray imaging. The scintillator is based on a Tb-doped Lu2SiO5 (LSO) film epitaxially grown on an adapted substrate. The high density, effective atomic number and light yield of the scintillating LSO significantly improves the efficiency of the X-ray imaging detectors currently used in synchrotron micro-imaging applications. In this work we present the characterization of the scintillating LSO films in terms of their spatial resolution performance and we provide two examples of high spatial and high temporal resolution applications.

  8. Electrical property measurements of Cr-N codoped TiO2 epitaxial thin films grown by pulsed laser deposition

    SciTech Connect

    Jacimovic, J; Gaal, R; Magrez, Arnaud; Forro, Laszlo; Regmi, Murari; Eres, Gyula

    2013-01-01

    The temperature dependent resistivity and thermo-electric power of Cr-N codoped TiO2 were compared with that of single element N and Cr doped and undoped TiO2 using epitaxial anatase thin films grown by pulsed laser deposition on (100) LaAlO3 substrates. The resistivity plots and especially the thermoelectric power data confirm that codoping is not a simple sum of single element doping. However, the negative sign of the Seebeck coefficient indicates electron dominated transport independent of doping. The narrowing distinction among the effects of different doping methods combined with increasing resistivity of the films with improving crystalline quality of TiO2 suggest that structural defects play a critical role in the doping process.

  9. Canted stripe phase evolution due to a spin reorientation transition in Fe films grown on Ag(001) vicinal surface

    NASA Astrophysics Data System (ADS)

    Dąbrowski, M.; Cinal, M.; Przybylski, M.; Chen, G.; N'Diaye, A. T.; Schmid, A. K.; Kirschner, J.

    2016-02-01

    The evolution of the domain structure with the thickness of bcc Fe films deposited on the Ag(116) vicinal surface is studied by spin-polarized low-energy electron microscopy. We show that a spin reorientation transition proceeds via two mechanisms: continuous rotation of magnetization within the vertical plane perpendicular to the steps and discontinuous reorientation of the in-plane component of magnetization, leading to splitting of the domains. In contrast to previously investigated systems with stripe domains, we reveal that in the case of a vicinal ferromagnetic surface, the domain width increases while changing the orientation of the magnetization from a canted out-of-plane state into an in-plane state. A theoretical model developed in this work successfully describes the domain structure behavior observed in our experiments and can be equally applied to other ferromagnetic films grown on vicinal surfaces.

  10. Comparison of AlN films grown by RF magnetron sputtering and ion-assisted molecular beam epitaxy

    SciTech Connect

    Chan, J.; Fu, T.; Cheung, N.W.; Ross, J.; Newman, N.; Rubin, M.

    1993-04-01

    Crystalline aluminum nitride (AlN) thin films were formed on various substrates by using RF magnetron sputtering of an A1 target in a nitrogen plasma and also by ion-assisted molecular beam epitaxy (IAMBE). Basal-oriented AlN/(111) Si showed a degradation of crystallinity with increased substrate temperature from 550 to 770 C, while the crystallinity of AlN/(0001) A1{sub 2}O{sub 3} samples improved from 700 to 850 C. The optical absorption characteristics of the AlN/(0001) A1{sub 2}O{sub 3} films as grown by both deposition methods revealed a decrease in subbandgap absorption with increased substrate temperature.

  11. Phase-coherent electron transport in (Zn, Al)O{sub x} thin films grown by atomic layer deposition

    SciTech Connect

    Saha, D. E-mail: pmisra@rrcat.gov.in; Misra, P. E-mail: pmisra@rrcat.gov.in; Ajimsha, R. S.; Joshi, M. P.; Kukreja, L. M.

    2014-11-24

    A clear signature of disorder induced quantum-interference phenomena leading to phase-coherent electron transport was observed in (Zn, Al)O{sub x} thin films grown by atomic layer deposition. The degree of static-disorder was tuned by varying the Al concentration through periodic incorporation of Al{sub 2}O{sub 3} sub-monolayer in ZnO. All the films showed small negative magnetoresistance due to magnetic field suppressed weak-localization effect. The temperature dependence of phase-coherence length (l{sub φ}∝T{sup −3/4}), as extracted from the magnetoresistance measurements, indicated electron-electron scattering as the dominant dephasing mechanism. The persistence of quantum-interference at relatively higher temperatures up to 200 K is promising for the realization of ZnO based phase-coherent electron transport devices.

  12. Impact of low temperature annealing on structural, optical, electrical and morphological properties of ZnO thin films grown by RF sputtering for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Purohit, Anuradha; Chander, S.; Sharma, Anshu; Nehra, S. P.; Dhaka, M. S.

    2015-11-01

    This paper presents effect of low temperature annealing on the physical properties of ZnO thin films for photovoltaic applications. The thin films of thickness 50 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing radio frequency magnetron sputtering technique followed by thermal annealing within low temperature range 150-450 °C. These as-grown and annealed films were subjected to the X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) for structural, optical, electrical and surface morphological analysis respectively. The compositional analysis of the as-grown ZnO film was also carried out using energy dispersive spectroscopy (EDS). The XRD patterns reveal that the films have wurtzite structure of hexagonal phase with preferred orientation (1 0 0) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in detail. The optical band gap was found in the range 3.30-3.52 eV and observed to decrease with annealing temperature except 150 °C. The current-voltage characteristics show that the films exhibit approximately ohmic behavior. The SEM studies show that the films are uniform, homogeneous and free from crystal defects and voids. The experimental results reveal that ZnO thin films may be used as alternative materials for eco-friendly buffer layer to the thin film solar cell applications.

  13. Structural properties and metallic conductivity of Ti1-x Nb x O2 films grown by atomic layer deposition on crystalline substrates

    NASA Astrophysics Data System (ADS)

    Luka, Grzegorz; Wachnicki, Lukasz; Jakiela, Rafal; Lusakowska, Elzbieta

    2015-12-01

    Niobium-doped titanium dioxide (Ti1-x Nb x O2, x  ≈  0.04, TNO) films were grown by atomic layer deposition (ALD) at a low growth temperature (220 °C) on LaAlO3(1 0 0) (LAO) and Al2O3(0 0 0 1) (c-sapphire) substrates. The films were without any post-deposition annealing. The films grown on both kinds of substrates have anatase structure. However, the films grown on LAO substrates have (0 0 1) predominant orientation compared to a higher content of (1 1 2) orientation in the films grown on sapphire. TNO/LAO films showed low resistivities (~10-3 Ω cm at room temperature) and a metallic-type electrical conductivity as opposed to higher resistivities (~10-2 Ω cm) and a thermally activated conductivity of TNO/sapphire layers. ALD growth mechanisms of TNO films on crystalline substrates were described.

  14. Reflective films and expression of light-regulated genes in field-grown apple

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reflective films are used in orchard management to improve fruit coloration. Numerous physiological studies on the effects of application of these films have been conducted, including variation of angles of light incidence and reflection, spectral determination of reflected light and effects on pho...

  15. Investigation of nanostructured transparent conductive films grown by rotational-sequential-sputtering

    SciTech Connect

    Lu, Jong-Hong Chen, Bo-Ying; Wang, Chih-Hsuan

    2014-03-15

    This study fabricates three types of nanostructured conductive transparent films using a rotational-sequential-sputtering method. These films include (1) TiO{sub 2}/indium-tin oxide (ITO) and SiO{sub x}/ITO nanomultilayer films, the optical refractive indices of which can be manipulated in the range of 2.42–1.63 at a wavelength of 550 nm with a controlled resistivity range of 1 × 10{sup −3} to 2 × 10{sup −4} Ω·cm. (2) Multilayer ITO films are deposited on polyethylene terephthalate substrates, providing good flexibility and resistivity as low as 5 × 10{sup −4} Ω·cm. Finally, (3) ultrathin ITO films ranging from subnanometer to a few nanometers in thickness enable exploration of ITO film growth and thermal stability. X-ray reflection characterization provides a rapid, non-destructive method to measure the single-layer thicknesses of the nanomultilayer films and ultrathin ITO films at subnanoscale resolution.

  16. Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method

    PubMed Central

    2011-01-01

    Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate. PMID:21711601

  17. Growth parameters effect on the electric and thermoelectric characteristics of Bi 2Se 3 thin films grown by MOCVD system

    NASA Astrophysics Data System (ADS)

    Al Bayaz, A.; Giani, A.; Artaud, M. C.; Foucaran, A.; Pascal-Delannoy, F.; Boyer, A.

    2002-06-01

    Bi 2Se 3 thin films were grown by metal organic chemical vapour deposition (MOCVD) on pyrex substrate in an horizontal reactor using Trimethylbismuth (TMBi) and Diethylselinium (DESe) as metal-organic sources. The effect of the growth parameters such as substrate temperature, Tg, and TMBi partial pressure, PTMBi, on the structural, electrical and thermoelectrical properties of Bi 2Se 3 films, has been investigated. We noticed that a high growth temperature is very important for a good orientation of crystallites, which can be directly related to the best values of Hall mobility and Seebeck coefficient found. Therefore, a large stability of the reactions over the substrates with following growth conditions: 455°C⩽ Tg⩽485°C,0.5×10 -4⩽ PTMBi⩽1×10 -4 atm and a total hydrogen flow rate DT=3 slm, is achieved. In these optimal growth conditions, we found a better crystalline structure of Bi 2Se 3 thin films using X-ray diffraction. Thus, these layers always displayed n-type conduction using Hall effect, with carrier concentration close to 2×10 19 cm -3 and maximum values of Hall mobility and Seebeck coefficient of μ=247 cm 2/V s and | α|=120 μV/K respectively. Then, these films appear to be very promising for thermoelectric applications.

  18. Structural and Magnetotransport Study of SrTiO3-δ/Si Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Currie, Alex; Cottier, Ryan; Villarreal, Oscar; Cantu, Jesus; Ponce, Arturo; Theodoropoulou, Nikoleta; Texas State University, San Marcos Collaboration; University of Texas, San Antonio Collaboration

    2014-03-01

    SrTiO3 (STO) films were grown on p-Si (001) substrates using molecular beam epitaxy (MBE). Oxygen vacancies were introduced by controlling the Oxygen resulting in SrTiO3-δ with δ ~ 0.02% for the lowest pressure. The single phase STO/Si films were of high crystalline quality as verified by x-ray diffraction, transmission electron microscopy, and had an rms roughness of less than 0.5nm measured by atomic force microscopy. Transport measurements were performed on the STO/Si structures in a Van der Pauw configuration. We measured resistance as a function of temperature, T = 3K-300K and as a function of an applied magnetic field , H =0 to +/- 9T. The resistivity decreased from 1 Ohm cm to 3x10-2 Ohm cm as the film thickness increased (3nm-60nm) for all temperatures. The magnetoresistance (MR) shows a reproducible trend for all films, the MR is positive at 300K, becomes negative between 200K and 100K and at low temperatures T =3-20K the MR is positive at low H =0 to +/- 2T but at high fields, it starts decreasing again. The MR behavior combined with the Hall effect data indicates the presence of localized electrons that delocalize with H and T. This research was supported by NSF Carrer Award DMR-1255629.

  19. Critical thickness and strain relaxation in molecular beam epitaxy-grown SrTiO{sub 3} films

    SciTech Connect

    Wang, Tianqi; Ganguly, Koustav; Marshall, Patrick; Xu, Peng; Jalan, Bharat

    2013-11-18

    We report on the study of the critical thickness and the strain relaxation in epitaxial SrTiO{sub 3} film grown on (La{sub 0.3}Sr{sub 0.7})(Al{sub 0.65}Ta{sub 0.35})O{sub 3} (001) (LSAT) substrate using the hybrid molecular beam epitaxy approach. No change in the film's lattice parameter (both the in-plane and the out-of-plane) was observed up to a film thickness of 180 nm, which is in sharp contrast to the theoretical critical thickness of ∼12 nm calculated using the equilibrium theory of strain relaxation. For film thicknesses greater than 180 nm, the out-of-plane lattice parameter was found to decrease hyperbolically in an excellent agreement with the relaxation via forming misfit dislocations. Possible mechanisms are discussed by which the elastic strain energy can be accommodated prior to forming misfit dislocations leading to such anomalously large critical thickness.

  20. Boron nitride phosphide thin films grown on quartz substrate by hot-filament and plasma-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, X. W.; Xu, S. Y.; Han, G. R.

    2004-10-01

    Boron nitride phosphide films are, for the first time, grown on transparent quartz substrate by hot filament and radio-frequency plasma co-assisted chemical vapor deposition technique. XPS, XRD, SEM, and UV measurements are performed to study the chemical composition, crystallization, microstructure, and optical absorption, respectively. A centipede-like microstructure and undulating ground morphology on the film surface are observed, and their growth mechanism is speculated upon. The chemical composition is determined as BN1-xPx, whose characteristic XRD peak is preliminarily identified. The optical band gap can be modulated between 5.52 eV and 3.74 eV, simply by adjusting the phosphorus content in BN1-xPx through modifying the PH3 flux during the film-deposition process. The merits of the BN1-xPx film, such as high ultraviolet photoelectric sensitivity with negligible sensitivity in the visible region, modifiable wide optical band gap, and good adhesion on transparent substrate, suggest potential applications for ultraviolet photo-electronics.

  1. SiO2 Film Grown On Glass In Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Kawahara, Hideo; Goda, Takuji; Nagayama, Hirotsugu; Honda, Hisao; Hishinuma, Akihiro

    1989-12-01

    Si02 film deposition on a glass was made by LPD method (Liquid Phase Deposition). This process involes the deposition and growth of Si02 layer on glass surface while immersing it in hexafluorosilicic acid (H2SiF6) solution supersaturated with silica. In this study, the influence of the impurities and H2SiF6 concentration in the solution on Si02 film properties was investigated by use of SIMS, ICP, Ellipsometry,IRRS and etch rate measurement. The results showed that LPD based Si02 film composition was scarcely affected by the concentration of such impurities as Na, K and Ca contained in the solution. Furthermore it was found that higher H2SiF6 concentration led to Si02 film with lower refractive index and lower etch rate. To have proper understanding of these apparently inconsistent results, the specific role of fluorine contained in the solution and the film was discussed.

  2. ECR Nb Films Grown on Amorphous and Crystalline Cu Substrates: Influence of Ion Energy

    SciTech Connect

    Valente, Anne-Marie; Eremeev, Grigory V.; Spradlin, Joshua K.; Phillips, H. Lawrence; Reece, Charles E.; Cao, C.; Proslier, Thomas; Tao, T.

    2014-02-01

    In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. Using energetic condensation of ions extracted from plasma generated by Electron Cyclotron Resonance, it has been demonstrated that Nb films with good structural properties and RRR comparable to bulk values can be produced on metallic substrates. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. Particular attention is given to the nucleation conditions to create a favourable template for growing the final surface exposed to SRF fields. The influence of the deposition energy on film growth on copper substrates is investigated with the characterization of the film surface, structure, superconducting properties and RF performance.

  3. Wet chemically grown composite thin film for room temperature LPG sensor

    NASA Astrophysics Data System (ADS)

    Birajadar, Ravikiran; Desale, Dipalee; Shaikh, Shaheed; Mahajan, Sandip; Upadhye, Deepak; Ghule, Anil; Sharma, Ramphal

    2014-04-01

    We have synthesized thin film of zinc oxide-polyaniline (ZnO/PANI) composite using a simple wet chemical approach. As-synthesized ZnO/PANI composite thin film studied using different characterization techniques. The optical study reveals the penetration and interaction of PANI molecules with ZnO thin film. Prominent blue shift in UV-vis due to interaction between ZnO and PANI indicate presence of zinc oxide in polyaniline matrix. It is observed that ZnO thin film is not sensitive to LPG (liquefied petroleum gas) at room temperature. On the other hand ZnO/PANI composite thin film shows good response and recovery behaviors at room temperature.

  4. Structural and morphological properties of metallic thin films grown by pulsed laser deposition for photocathode application

    NASA Astrophysics Data System (ADS)

    Lorusso, A.; Gontad, F.; Caricato, A. P.; Chiadroni, E.; Broitman, E.; Perrone, A.

    2016-03-01

    In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density, while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed.

  5. Heteroepitaxial Film Silicon Solar Cell Grown on Ni-W Foils

    SciTech Connect

    Wee, S. H.; Cantoni, C.; Fanning, T. R.; Teplin, C. W.; Bogorin, D. F.; Bornstein, J.; Bowers, K.; Schroeter, P.; Hasoon, F.; Branz, H. M.; Paranthaman, M. P.; Goyal, A.

    2012-03-01

    Heteroepitaxial semiconductor films on low-cost, flexible metal foil templates are a potential route to inexpensive, high-efficiency solar cells. Here, we report epitaxial growth of Si films on low-cost, flexible, biaxially-textured Ni-W substrates. A robust buffer architecture comprised of multiple epitaxial oxide layers has been developed to grow high quality, heteroepitaxial Si films without any undesired reaction between the Si film and the metal substrate and with a single biaxial texture. XRD analysis including {omega}-scans, {phi}-scans, and pole figures confirms that the buffers and silicon are all epitaxial, with excellent cube-on-cube epitaxy. A photo-conversion efficiency of 1.1% is demonstrated from a proof-of-concept heteroepitaxial film Si solar cell.

  6. Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

    SciTech Connect

    Chebil, W.; Fouzri, A.; Fargi, A.; Azeza, B.; Zaaboub, Z.; and others

    2015-10-15

    Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

  7. Photoreflectance analysis of annealed vanadium-doped GaAs thin films grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Fitouri, H.; Bilel, C.; Zaied, I.; Bchetnia, A.; Rebey, A.; El Jani, B.

    2015-09-01

    In this study, we investigate the optical properties of annealed vanadium-doped GaAs films grown on GaAs substrates by metalorganic vapor phase epitaxy. The temperature dependence of the photoreflectance (PR) of as-grown GaAs:V films has been studied. We used the fit with Third-Derivative Functional Form model to evaluate the physical parameters. The temperature dependence of band gap and spin-orbit energies can be described by the Bose-Einstein statistical expression. The PR spectra of the samples are measured after thermal annealing in order to check any improvement in the optical quality of the material. The PR signal amplitude of GaAs:V samples decreased after thermal annealing. Degradation of the PR signal for annealing temperature at about 850 °C is observed revealing a poor quality of the layer surface states and an important density of the recombination centers. The lock-in phase analysis of PR spectra allows to determine the time constant for GaAs:V sample before and after thermal annealing.

  8. Investigation of NbNx thin films and nanoparticles grown by pulsed laser deposition and thermal diffusion

    NASA Astrophysics Data System (ADS)

    Hassan Farha, Ashraf

    Niobium nitride films (NbNx) were grown on Nb and Si (100) substrates using pulsed laser deposition (PLD), laser heating, and thermal diffusion methods. Niobium nitride films were deposited on Nb substrates using PLD with a Q-switched Nd: YAG laser (lambda = 1064 nm, 40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, different nitrogen background pressures and deposition temperatures. The effect of changing PLD parameters for films done by PLD was studied. The seen observations establish guidelines for adjusting the laser parameters to achieve the desired morphology and phase of the grown NbNx films. When the fabrication parameters are fixed, except for laser fluence, surface roughness, deposition rate, nitrogen content, and grain size increases with increasing laser fluence. Increasing nitrogen background pressure leads to change in the phase structure of the NbNx films from mixed -Nb 2N and cubic delta-NbN phases to single hexagonal beta- Nb 2N. A change in substrate temperature led to a pronounced change in the preferred orientation of the crystal structure, the phase transformation, surface roughness, and composition of the films. The structural, electronic, and nanomechanical properties of niobium nitride PLD deposited at different nitrogen pressures (26.7-66.7 Pa) on Si(100) were investigated. The NbNx, films exhibited a cubic delta-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The highly-textured delta-NbN films have a Tc up to 15.07 K. The film was deposited at a nitrogen background pressure of 66.7 Pa exhibited improved superconducting properties and showed higher hardness values as compared to films deposited at lower nitrogen pressures. NbN nanoclusters that were deposited on carbon coated Cu-grids using PLD at laser fluence of 8 J/cm2 were observed. Niobium nitride is prepared by heating of Nb sample in a reactive nitrogen atmosphere (133 Pa

  9. High electron mobility thin-film transistors based on Ga{sub 2}O{sub 3} grown by atmospheric ultrasonic spray pyrolysis at low temperatures

    SciTech Connect

    Thomas, Stuart R. E-mail: thomas.anthopoulos@imperial.ac.uk; Lin, Yen-Hung; Faber, Hendrik; Anthopoulos, Thomas D. E-mail: thomas.anthopoulos@imperial.ac.uk; Adamopoulos, George; Sygellou, Labrini; Stratakis, Emmanuel; Pliatsikas, Nikos; Patsalas, Panos A.

    2014-09-01

    We report on thin-film transistors based on Ga{sub 2}O{sub 3} films grown by ultrasonic spray pyrolysis in ambient atmosphere at 400–450 °C. The elemental, electronic, optical, morphological, structural, and electrical properties of the films and devices were investigated using a range of complementary characterisation techniques, whilst the effects of post deposition annealing at higher temperature (700 °C) were also investigated. Both as-grown and post-deposition annealed Ga{sub 2}O{sub 3} films are found to be slightly oxygen deficient, exceptionally smooth and exhibit a wide energy bandgap of ∼4.9 eV. Transistors based on as-deposited Ga{sub 2}O{sub 3} films show n-type conductivity with the maximum electron mobility of ∼2 cm{sup 2}/V s.

  10. High-quality Bi{sub 2}Te{sub 3} thin films grown on mica substrates for potential optoelectronic applications

    SciTech Connect

    Wang, K.; Bao, L. H.; Liu Yanwen; Wang Weiyi; Xiu Faxian; Meyer, N.; Che, X. Y.; He, L.; Lang, M. R.; Wang, K. L.; Chen, Z. G.; Post, K.; Basov, D. N.; Zou, J.

    2013-07-15

    We report high-quality topological insulator Bi{sub 2}Te{sub 3} thin films grown on muscovite mica substrates by molecular beam epitaxy. The topographic and structural analysis revealed that the Bi{sub 2}Te{sub 3} thin films exhibited atomically smooth terraces over a large area and a high crystalline quality. Both weak antilocalization effect and quantum oscillations were observed in the magnetotransport of the relatively thin samples. A phase coherence length of 277 nm for a 6 nm thin film and a high surface mobility of 0.58 m{sup 2} V{sup -1} s{sup -1} for a 4 nm thin film were achieved. These results confirm that the thin films grown on mica are of high quality.

  11. Polycrystalline SrFe12O19 thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Garcia, Tupac; de Posada, E.; Jimenez, Ernesto; Sanchez Ll., J. L.; Diaz Castanon, S.; Bartolo-Perez, Pascual; Cauich, W.; Oliva, I.; Pena, J. L.; Ceh, O.

    1999-07-01

    Polycrystalline SrFe12O19 thin films were deposited on Si (100) substrates by PLD using a Nd-YAG laser ((lambda) equals 1064 nm). During the deposition process substrates were kept at room temperature. As-deposited films were annealed in air at temperatures between 600 degree(s)C and 840 degree(s)C. Samples were characterized by AES, ESCA, SEM, AFM, x-ray diffraction and VSM. It is presented the relevance of the preparation of the target surface on the film quality. Some differences in the chemical composition of as-deposited films, compared with the target and the annealed films, were observed. The x-ray diffraction spectra show a textured as- deposited films. Samples annealed at 600 degree(s)C, and below, showed a very weak magnetic response. In contrast annealing in the temperature range 700 degree(s)C - 840 degree(s)C led to the formation of a nanocrystalline particle system (average particle size 150 - 350 nm) which behave as a single domain in the thermally demagnetized state. The obtained coercivities (5750 - 6850 Oe) are among the highest values reported for films, powders and sintered samples.

  12. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Santra, T. S.; Liu, C. H.; Bhattacharyya, T. K.; Patel, P.; Barik, T. K.

    2010-06-01

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of CC, CH, SiC, and SiH bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio ID/IG. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  13. Surface-Morphology-Induced Hydrophobicity of Fluorocarbon Films Grown by a Simultaneous Etching and Deposition Process

    NASA Astrophysics Data System (ADS)

    Fang, J. S.; Lin, C. S.; Huang, Y. Y.; Chin, T. S.

    2015-08-01

    Development of facile methods to prepare hydrophobic films is of great important. We report fluorocarbon films deposited by a simple plasma-assisted chemical vapor deposition method using C3F8 and C2H2 with extra Ar and/or O2 gases. The surface characteristics of the films were examined by scanning electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy. The hydrophobic and oleophobic properties of the films were evaluated by measurements of static contact angle. The results showed that the film deposited with C3F8, C2H2, Ar, and O2 exhibited a water contact angle of 114°, hexadecane contact angle of 45°, and transmittance of 94.5%. Photoelectron spectra further revealed that the films contained mainly CF and CF2 bonds and thus a high F/C ratio. Introduction of O2 increased the F/C ratio, which combined with the stripe-like surface of the films achieved better hydrophobicity.

  14. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    SciTech Connect

    Santra, T. S.; Liu, C. H.; Bhattacharyya, T. K.; Patel, P.; Barik, T. K.

    2010-06-15

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of C-C, C-H, Si-C, and Si-H bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio I{sub D}/I{sub G}. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  15. Transport properties of Bi2Se3 thin films grown by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wei, Z. T.; Zhang, M.; Yan, Y.; Kan, X.; Yu, Z.; Chen, Y. L.; Yang, X. S.; Zhao, Y.

    2015-11-01

    Epitaxial growth of Bi2Se3 thin films is of great current interest due to the advantages in spintronics and thermoelectrical applications. In this paper, Bi2Se3 thin films on Si (111) substrate have been prepared via magnetron sputtering deposition with post-annealing treatment and their microstructures and electrical transport properties were studied. Good quality with highly c-axis oriented films could be obtained after post-annealing treatment. The annealing temperature (Ta) obviously affected the phase structures and electrical properties. The crystallinity and the lattice parameters c of the Bi2Se3 thin-films increased with increasing Ta. The relative atomic ratio of Se/Bi decreased with increasing Ta and large number of Se vacancies was discovered in films with Ta = 350°C. The resistivity of films decreased monotonously and showed weakly metallic resistivity with the increase of Ta. Non-saturated high-field linear magnetoresistance and weak antilocalization were found in films with higher Ta.

  16. Amorphization and recrystallization of epitaxial ReSi2 films grown on Si(100)

    NASA Technical Reports Server (NTRS)

    Kim, Kun HO; Bai, G.; Nicolet, MARC-A.; Mahan, John E.; Geib, Kent M.

    1991-01-01

    The effects of implantation damage and the chemical species of the implant on structural and electrical properties of epitaxial ReSi2 films on Si(100) implanted with Si-28 or Ar-40 ions, at doses ranging from 10 to the 13th/sq cm to 10 to the 15th/sq cm, were investigated using the backscattering spectrometry, XRD, and the van der Pauw techniques. Results showed that ion implantation produces damage in the film, which increases monotonically with dose; the resistivity of the film decreases monotonically with dose.

  17. High-quality, faceted cubic boron nitride films grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, W. J.; Jiang, X.; Matsumoto, S.

    2001-12-01

    Thick cubic boron nitride (cBN) films showing clear crystal facets were achieved by chemical vapor deposition. The films show the highest crystallinity of cBN films ever achieved from gas phase. Clear evidence for the growth via a chemical route is obtained. A growth mechanism is suggested, in which fluorine preferentially etches hBN and stabilizes the cBN surface. Ion bombardment of proper energy activates the cBN surface bonded with fluorine so as to enhance the bonding probability of nitrogen-containing species on the F-stabilized B (111) surface.

  18. Field emission from bias-grown diamond thin films in a microwave plasma

    DOEpatents

    Gruen, Dieter M.; Krauss, Alan R.; Ding, Ming Q.; Auciello, Orlando

    2002-01-01

    A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.

  19. Electrochemical properties of Si film electrodes grown on current collectors with CuO nanostructures for thin-film microbatteries.

    PubMed

    Cho, Gyu-Bong; Lee, Won-Rak; Choi, Hyun-Kwang; Kim, Kyeong-Hee; Nam, Tae-Hyun; Kim, Guk-Tae; Noh, Jung-Pil; Kim, Ki-Won

    2014-12-01

    Si film electrodes were deposited onto Cu foil current collectors fabricated with well-formed CuO nanostructures. The structural and electrochemical properties of the Cu foils oxidized for 1, 3, and 6 h and of the Si film electrodes were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), and charge/discharge tests. The morphologies and XRD profiles suggested that the oxidized Cu foils consisted of a top CuO layer and a bottom Cu2O layer. The surface roughness of the Cu foils decreased with increasing oxidation time since the flower-like CuO nanostructures weakly adhered to the surface were easily detached by ultrasonic cleaning. The cycle performance of the Si film electrode with the rougher CuO layer rapidly deteriorated, whereas the flat Cu2O layer showing a relatively high electric conductivity induced the formation of a dense Si film and improved the electrochemical performance of the Si film electrode. PMID:25971055

  20. Flexible cadmium telluride thin films grown on electron-beam-irradiated graphene/thin glass substrates

    SciTech Connect

    Seo, Won-Oh; Kim, Jihyun; Koo, Yong Hwan; Kim, Byungnam; Lee, Byung Cheol; Kim, Donghwan

    2014-08-25

    We demonstrate the close-spaced sublimation growth of polycrystalline cadmium telluride (CdTe) thin films on a flexible graphene electrode/thin glass substrate structure. Prior to the growth of CdTe films, chemical-vapor-deposited graphene was transferred onto a flexible glass substrate and subjected to electron-beam irradiation at an energy of 0.2 MeV in order to intentionally introduce the defects into it in a controlled manner. Micro-Raman spectroscopy and sheet resistance measurements were employed to monitor the damage and disorder in the electron-beam irradiated graphene layers. The morphology and optical properties of the CdTe thin films deposited on a graphene/flexible glass substrate were systematically characterized. The integration of the defective graphene layers with a flexible glass substrate can be a useful platform to grow various thin-film structures for flexible electronic and optoelectronic devices.

  1. Growth mechanism of graphene on graphene films grown by chemical vapor deposition.

    PubMed

    Kang, Cheong; Jung, Da Hee; Lee, Jin Seok

    2015-03-01

    We report an approach for the synthesis of mono- or bilayer graphene films by atmospheric-pressure chemical vapor deposition that can achieve a low defect density through control over the growth time. Different heating ramp rates were found to lead to variation in the smoothness and grain size of the Cu foil substrate, which directly influenced the density of the graphene domains. The rough Cu surface induced by rapid heating creates a high density of graphene domains in the initial stage, ultimately resulting in a graphene film with a high defect density due to an increased overlap between domains. Conversely, a slow heating rate resulted in a smooth and flat Cu surface, thereby lowering the density of the initial graphene domains and ensuring a uniform monolayer film. From this, we demonstrate that the growth mechanism of graphene on existing graphene films is dependent on the density of the initial graphene domains, which is affected by the heating ramp rate. PMID:25655906

  2. Pseudo capacitive performance of copper oxide thin films grown by RF sputtering

    SciTech Connect

    Reddy, B. Purusottam; Ganesh, K. Sivajee; Hussain, O. M.

    2015-06-24

    Thin films of Copper Oxide were prepared by radio frequency magnetron sputtering on steel substrates maintained at 250°C under different RF powers ranging from 150W to 250W by keeping the sputtering pressure at 5.7×10{sup −3} mbar and O{sub 2}:Ar ratio of 1:7. The influence of RF power on the pseudo capacitive performance of thin films was studied. The X-ray diffraction studies and Raman studies indicates that all the thin films exhibits CuO phase. The electrochemical studies was done by using three electrode configuration with platinum as reference electrode. From the cyclic voltammetry studies a high rate pseudocapacitance of 227 mFcm{sup −2} at 0.5 mVs{sup −1} and 77% of capacity retention after 1000 cycles was obtained for the CuO thin films prepared at an RF power of 220W.

  3. Optical properties of Sm-doped ceria nanostructured films grown by electrodeposition at low temperature

    NASA Astrophysics Data System (ADS)

    Ursaki, V. V.; Lair, V.; Żivković, L.; Cassir, M.; Ringuedé, A.; Lupan, O.

    2012-09-01

    Nanostructured undoped and samarium doped ceria thin nanocolumnar films are electrodeposited onto (FTO) glass substrates at low-temperature (30 °C) with a subsequent thermal annealing at 600 °C for 1 h. Films are obtained from mixed Sm3+/Ce3+ aqueous nitrate solutions, applying a -0.8 V/(SCE) potential for 1 h. Cubic fluorite type ceria nanostructured films of high crystal quality are synthesized as confirmed by X-ray diffraction and Raman spectroscopy. SEM analysis demonstrates that doping with Sm improves the quality of the film with respect to crack formation. The incorporation and activation of the Sm3+ ions in the ceria host as well as the Stark splitting of the manifolds responsible for emission in the red-orange spectral range are investigated by means of photoluminescence spectroscopy.

  4. Structural, optical and magnetic properties of Fe-doped barium stannate thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    James, K. K.; Aravind, Arun; Jayaraj, M. K.

    2013-10-01

    Barium stannate is a wide band gap semiconductor with cubic perovskite structure. Polycrystalline bulk samples of BaSn1-xFexO3d (BFS), with x = 0.00, 0.02, 0.03, 0.05 and 0.10 were prepared by solid-state reaction. In this paper, we report the growth of undoped and Fe doped barium stannate thin films on fused silica substrate using pulsed laser deposition (PLD) technique at a relatively high substrate temperature and low oxygen pressure. The deposited films have wide bandgap and are transparent in the visible region. The X-ray diffraction analysis of the films confirmed the cubic structure. Microstructural studies were carried out using micro-Raman spectroscopy and AFM analysis. Defect induced Raman shifts were observed in the samples. Magnetic studies revealed an increase in magnetic properties for films doped with 10 at% Fe doped samples.

  5. Dielectric anomaly in Li-doped zinc oxide thin films grown by sol gel route

    NASA Astrophysics Data System (ADS)

    Dhananjay; Singh, Satyendra; Nagaraju, J.; Krupanidhi, S. B.

    2007-08-01

    Sol gel route was employed to grow polycrystalline thin films of Li-doped ZnO thin films (Zn1-xLixO, x=0.15). Polycrystalline films were obtained at a growth temperature of 400 500 °C. Ferroelectricity in Zn0.85Li0.15O was verified by examining the temperature variation of the real and imaginary parts of dielectric constant, and from the C V measurements. The phase transition temperature was found to be 330 K. The room-temperature dielectric constant and dissipation factor were 15.5 and 0.09 respectively, at a frequency of 100 kHz. The films exhibited well-defined hysteresis loop, and the values of spontaneous polarization (Ps) and coercive field were 0.15 μC/cm2 and 20 kV/cm, respectively, confirming the presence of ferroelectricity.

  6. Characterization of CdZnS thin film grown by using different capping agents

    NASA Astrophysics Data System (ADS)

    Shrivastava, R.; Shrivastava, S. C.; Singh, R. S.; Singh, A. K.

    2015-03-01

    In this paper, a comparative study of CdZnS nano-crystalline films with two different capping agents, CTAB and TSC, deposited by chemical bath deposition method has been made using x-ray diffraction, scanning electron microscope, transmission electron microscopy and atomic frequency microscopy. The structure of CdZnS nano-crystalline films with capping agents CTAB and TSC was observed by XRD technique and found to be both hexagonal and cubic. SEM micrographs show the cabbage-like structure of CdZnS nano-crystalline films when prepared in the presence of capping agents. The AFM image shows the presence of nanorods in the samples. The TEM diffraction pattern indicates a nano-crystalline structure with the presence of various crystal planes. Elemental analysis has also been made and it has been found that no impurity was present in the film.

  7. Crystallization kinetics of GeTe phase-change thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Sun, Xinxing; Thelander, Erik; Gerlach, Jürgen W.; Decker, Ulrich; Rauschenbach, Bernd

    2015-07-01

    Pulsed laser deposition was employed to the growth of GeTe thin films on Silicon substrates. X-ray diffraction measurements reveal that the critical crystallization temperature lies between 220 and 240 °C. Differential scanning calorimetry was used to investigate the crystallization kinetics of the as-deposited films, determining the activation energy to be 3.14 eV. Optical reflectivity and in situ resistance measurements exhibited a high reflectivity contrast of ~21% and 3-4 orders of magnitude drop in resistivity of the films upon crystallization. The results show that pulsed laser deposited GeTe films can be a promising candidate for phase-change applications.

  8. X-ray photoelectron spectroscopy study of the growth kinetics of biomimetically grown hydroxyapatite thin-film coatings

    NASA Astrophysics Data System (ADS)

    McLeod, K.; Kumar, S.; Dutta, N. K.; Smart, R. St. C.; Voelcker, N. H.; Anderson, G. I.

    2010-09-01

    Hydroxyapatite (HA) thin-film coatings grown biomimetically using simulated body fluid (SBF) are desirable for a range of applications such as improved fixation of fine- and complex-shaped orthopedic and dental implants, tissue engineering scaffolds and localized and sustained drug delivery. There is a dearth of knowledge on two key aspects of SBF-grown HA coatings: (i) the growth kinetics over short deposition periods, hours rather than weeks; and (ii) possible difference between the coatings deposited with and without periodic SBF replenishment. A study centred on these aspects is reported. X-ray photoelectron spectroscopy (XPS) has been used to study the growth kinetics of SBF-grown HA coatings for deposition periods ranging from 0.5 h to 21 days. The coatings were deposited with and without periodic replenishment of SBF. The XPS studies revealed that: (i) a continuous, stable HA coating fully covered the titanium substrate after a growth period of 13 h without SBF replenishment; (ii) thicker HA coatings about 1 μm in thickness resulted after a growth period of 21 days, both with and without SBF replenishment; and (iii) the Ca/P ratio at the surface of the HA coating was significantly lower than that in its bulk. No significant difference between HA grown with and without periodic replenishment of SBF was found. The coatings were determined to be carbonated, a characteristic desirable for improved implant fixation. The atomic force and scanning electron microscopies results suggested that heterogeneous nucleation and growth are the primary deposition mode for these coatings. Primary osteoblast cell studies demonstrated the biocompatibility of these coatings, i.e., osteoblast colony coverage of approximately 80%, similar to the control substrate (tissue culture polystyrene).

  9. Conductivity of Thin Films Based on Single-Walled Carbon Nanotubes Grown by Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Rybakov, M. S.; Kosobutsky, A. V.; Sevostyanov, O. G.; Russakov, D. M.; Lomakin, M. V.; Chirkova, I. M.; Shandakov, S. D.

    2015-03-01

    Electrical and optical properties of thin films of single-walled carbon nanotubes (SWCNT) obtained by aerosol chemical vapor deposition using ethanol, ferrocene, and sulfur are studied. Structural and geometrical characteristics of the synthesis products are determined by the methods of Raman spectroscopy and transmission electron microscopy. The effect of sulfur on the properties of the SWCNTs and thin films based on them is found.

  10. Influences of growth parameters on the film formation of hexagonal boron nitride thin films grown on sapphire substrates by low-pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Umehara, Naoki; Masuda, Atsushi; Shimizu, Takaki; Kuwahara, Iori; Kouno, Tetsuya; Kominami, Hiroko; Hara, Kazuhiko

    2016-05-01

    Hexagonal boron nitride (h-BN) films were grown on c-plane sapphire substrates by low-pressure chemical vapor deposition with BCl3 and NH3 as the boron and nitrogen sources, respectively, and the influences of growth parameters on the film quality were investigated for samples with a thickness of about 1 µm. The dependence of X-ray diffraction on the growth temperature (T g) indicated that the crystalline quality is most improved in the sample grown at 1200 °C, in which the epitaxial relationship of {100}h-BN ∥ {110}sapphire and {001}h-BN ∥ {001}sapphire was confirmed. This condition enhanced lateral growth, resulting in the formation of grains with flat top surfaces. The T g dependence was discussed in relation to the amorphous AlN formed on the substrate surface and the reaction between BCl3 and NH3 in the vapor phase. The correlation between the structural and luminescent properties, which was found from the T g dependence of CL, was also discussed.

  11. Negative Magnetoresistance of Indium Tin Oxide Nanoparticle Thin Films Grown by Chemical Thermolysis

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Yoshida, Kota; Higaki, Tomohiro; Kimura, Yuta; Nakamoto, Masami; Kashiwagi, Yukiyasu; Yamamoto, Mari; Saitoh, Masashi; Ohno, Toshinobu; Furuta, Shinya

    2013-02-01

    To clarify the electrical transport properties of nanostructured thin films, tin-doped indium oxide (ITO) nanoparticle (NP) solution-processed films were fabricated. An air-atmosphere, simple chemical thermolysis method was used to grow the ITO NPs, and the structural and electrical properties of spin-coated granular ITO NP films were investigated. X-ray diffraction measurements showed clear observation of the cubic indium oxide (222) diffraction peak, and films with a smaller Sn concentration were shown to have a better crystalline quality. We further explored the physical origin of the sign of the magnetoresistance (MR) in the variable-range hopping (VRH) region. A negative MR under a magnetic field perpendicular to the film surface increases with decreasing Sn concentration, and these results can be explained by the forward interference model in the VRH region. A larger negative MR is attributed to longer localization and hopping lengths, and better crystallinity. Thus, ITO NP thin films produced by this method are attractive candidates for oxide-based diluted magnetic semiconductors and other electronic devices.

  12. Atomically-Smooth MgO films grown on Epitaxial Graphene by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Stuart, Sean; Sandin, Andreas; Rowe, Jack; Dougherty, Dan; Ulrich, Marc

    2013-03-01

    The growth of high quality insulating films on graphene is a crucial materials science task for graphene electronic and spintronic applications. It has been demonstrated that direct spin injection from a magnetic electrode to graphene is possible using MgO tunnel barriers of sufficient quality. We have used pulsed laser deposition (PLD) to grow thin magnesium oxide films directly on epitaxial graphene on SiC(0001). We observe very smooth film morphologies (typical rms roughness of ~ 0.4 nm) that are nearly independent of film thickness and conform to the substrate surface which had ~ 0.2 nm rms roughness. Surface roughness of 0.04 nm have been recorded for ~ 1nm films with no pinholes seen by AFM. XPS and XRD data show non crystalline, hydroxylated MgO films with uniform coverage. This work shows that PLD is a good technique to produce graphene-oxide interfaces without pre-deposition of an adhesion layer or graphene functionalization. The details and kinetics of the deposition process will be described with comparisons being made to other dielectric-on-graphene deposition approaches. Funded by ARO Staff Research Contract # W911NF.

  13. MBE Grown In x Ga1- x N Thin Films with Bright Visible Emission Centered at 550 nm

    NASA Astrophysics Data System (ADS)

    Dasari, K.; Thapa, B.; Wang, J.; Wright, J.; Kaya, S.; Jadwisienczak, W. M.; Palai, R.

    2016-04-01

    The In x Ga1- x N thin films with indium content of x = 14-18 at.% were successfully grown by using molecular beam epitaxy (MBE) at high growth temperatures from 650°C to 800°C. In situ reflection high-energy electron diffraction (RHEED) of the In x Ga1- x N films confirmed the Stranski-Krastanov growth mode. X-ray diffraction (XRD) of the films confirmed their highly crystalline nature having c-axis orientation with a small fraction of secondary InN phase admixture. High-resolution cross-sectional scanning electron microscopy images showed two-dimensional epilayers growth with thickness of about ˜260 nm. The high growth temperature of In x Ga1- x N epilayers is found to be favorable to facilitate more GaN phase than InN phase. All the fundamental electronic states of In, Ga, and N were identified by x-ray photoelectron spectroscopy (XPS) and the indium composition has been calculated from the obtained XPS spectra with CASAXPS software. The composition calculations from XRD, XPS and photoluminescence closely match each other. The biaxial strain has been calculated and found to be increasing with the In content. Growing In x Ga1- x N at high temperatures resulted in the reduction in stress/strain which affects the radiative electron-hole pair recombination. The In x Ga1- x N film with lesser strain showed a brighter and stronger green emission than films with the larger built-in strain. A weak S-shaped near band edge emission profile confirms the relatively homogeneous distribution of indium.

  14. Compact magnetooptical isolator with cobalt ferrite on silicon photonic circuits

    NASA Astrophysics Data System (ADS)

    Yanaga, Megumi; Shoji, Yuya; Takamura, Yota; Nakagawa, Shigeki; Mizumoto, Tetsuya

    2015-08-01

    In the telecom wavelength range, the magnetooptical effect of cobalt ferrites is approximately 10 times larger than that of conventional magnetooptical materials such as yttrium iron garnets. In this study, we focus on an application of cobalt ferrite to a magnetooptical isolator that is to be miniaturized and made suitable for integration. First, we prepare polycrystalline cobalt ferrite films deposited on a silicon substrate using a MgO buffer layer. Next, we fabricate a waveguide optical isolator of silicon waveguides by the partial deposition of the cobalt ferrite films. An optical isolation ratio of 5.5 dB is demonstrated.

  15. High-Jc YBa2Cu3O7-δ superconducting film grown by laser-assisted chemical vapor deposition using a single liquid source and its microstructure

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Kato, Takeharu; Yokoe, Daisaku; Hirayama, Tsukasa; Goto, Takashi

    2013-09-01

    A YBa2Cu3O7-δ (YBCO) film was prepared on a multilayer-coated Hastelloy C276 substrate by laser-assisted metalorganic chemical vapor deposition using a single liquid source precursor. A c-axis-oriented YBCO film was grown epitaxially on a (100) CeO2 layer at a deposition rate of 11 μm h-1. A screw dislocation and stacking faults were observed in the cross-section of the YBCO film. The critical current density of the YBCO film reached 2.7 MA cm-2.

  16. Effects of Precursor Concentration on Structural and Optical Properties of ZnO Thin Films Grown on Muscovite Mica Substrates by Sol-Gel Spin-Coating.

    PubMed

    Kim, Younggyu; Leem, Jae-Young

    2016-05-01

    The structural and optical properties of the ZnO thin films grown on mica substrates for different precursor concentrations were investigated. The surface morphologies of all the samples indicated that they consisted of granular structures with spherical nano-sized crystallites. The thickness of the ZnO thin films increased significantly and the optical band gap exhibited a blue shift with an increase in the precursor concentration. It is remarkable that the highest I(NBE)/I(DLE) ratio was observed for the ZnO thin film with 0.8 M precursor concentration, even though cracks formed on the surface of this film. PMID:27483897

  17. Conduction-type control of Ge films grown on (NH 4) 2S-treated GaAs by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Inada, M.; Fujishima, T.; Umezu, I.; Sugimura, A.; Yamada, S.

    2001-07-01

    We have performed epitaxial growth of Ge films on (NH 4) 2S-treated GaAs (0 0 1) substrates under various growth temperatures using molecular beam epitaxy. We confirmed that this sulfur passivation is quite effective for preventing the oxidation of GaAs surface. Thus, the Ge films were grown epitaxially on GaAs substrate without thermal cleaning. The electric properties of Ge films were investigated using Hall measurement and it was found that the conduction type of Ge films can be controlled by growth temperature. The Ga-S bond is thought to be the key for conduction type control, although the details are not identified yet.

  18. Composition dependence of the photochemical reduction of Ag+ by as-grown Pb(ZrxTi1-x)O3 films on indium tin oxide electrode

    NASA Astrophysics Data System (ADS)

    Zhang, Man; Jiang, Chunxiang; Dong, Wen; Zheng, Fengang; Fang, Liang; Su, Xiaodong; Shen, Mingrong

    2013-09-01

    Photochemical growth of metal particles on ferroelectric films has usually been found to depend on polarization effect solely. This research exploits the interplay of the film/electrode interface barrier and depolarization field on the photoreduction of Ag+ to Ag onto Pb(Zr,Ti)O3 (PZT) films deposited on indium tin oxide (ITO) electrodes. Ag nanoparticles are observed on the as-grown polycrystalline PZT films without poling, while the particle size and density are closely related to the concentration of Zr in PZT and the poling direction. The enhancement on the photoelectrochemical properties of the ITO/PZT photocathode by the decoration of Ag nanoparticles is finally demonstrated.

  19. Epitaxial growth of Ge1-xSnx films with x up to 0.14 grown on Ge (00l) at low temperature

    NASA Astrophysics Data System (ADS)

    Tao, Ping; Huang, Lei; Cheng, H. H.; Wang, Huan-Hua; Wu, Xiao-Shan

    2014-08-01

    We characterize the structures of Ge1-xSnx films with x up to 0.14 grown on Ge (00l) by molecular-beam epitaxy at low temperature. The results show that Ge1-xSnx films are fully strained even at high Sn composition. The in-plane lattice parameters remain exactly the same as that of the substrate. Depth sensitivity analysis of the lattice parameters indicates that the strains of the epitaxial films are all in homogeneity. The films are fully strained. Poisson ratios, the force constants for the bonds between Ge and Sn are estimated and discussed in the present paper. Raman results show Ge—Ge, Ge—Sn, Sn—Sn vibrational modes. The Sn—Sn bond aggregation may respond to the high quality of our films. The fully strained epitaxy films with high content of Sn may be useful in designing the high quality GeSn films.

  20. Strain Relaxation in Thin Films of La1.85Sr0.15CuO4 Grown by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Zaytseva, I.; Cieplak, M. Z.; Abal'Oshev, A.; Berkowski, M.; Domukhovski, V.; Paszkowicz, W.; Shalimov, A.

    2007-01-01

    X-ray diffraction, resistivity, and susceptibility measurements are used to examine the effects of film thickness d (from 17 to 250 nm) on the structural and superconducting properties of La1.85Sr0.15CuO4 films grown by pulsed laser deposition on SrLaAlO4 substrates. For each d the film sgrow with a variable strain, ranging from a large compressive strain in the thinnest films to a negligible or tensile strain in thick films. Our results indicate that the tensile strain is not caused by the off-stoichiometric layer at the substrate-film interface. Instead, it may be caused by the extreme oxygen deficiency in some of the films.

  1. On-wafer magnetically tunable millimeter wave notch filter using M-phase Ba hexagonal ferrite/Pt thin films on Si

    NASA Astrophysics Data System (ADS)

    Harward, I.; Camley, R. E.; Celinski, Z.

    2014-10-01

    A prototype of a fully integrated on-wafer, magnetically tunable band-stop filter operating at millimeter wave frequencies is demonstrated on a Si substrate. In contrast to earlier studies, the filter uses a very thin barium hexagonal ferrite film incorporated into the dielectric layer of a microstrip transmission line to filter the signal. The zero-field operational frequency is about 34 GHz, increasing linearly with the strength of a static, perpendicularly applied magnetic field at a rate of about 2.7 GHz/kOe. Experimentally, high signal attenuation (33-67 dB/cm) at the resonance frequency and insertion losses as low as 4.5 dB were simultaneously observed, while the 3 dB device bandwidths were generally below 1 GHz. Our calculations are in quantitative agreement with the experimental results. We also find an important result that the thickness and conductivity of the Pt ground plane plays a key role in insertion losses, indicating directions for further improvements.

  2. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D.

    2013-09-15

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  3. Microstructures and growth mechanisms of GaN films epitaxially grown on AlN/Si hetero-structures by pulsed laser deposition at different temperatures

    PubMed Central

    Wang, Wenliang; Yang, Weijia; Lin, Yunhao; Zhou, Shizhong; Li, Guoqiang

    2015-01-01

    2 inch-diameter GaN films with homogeneous thickness distribution have been grown on AlN/Si(111) hetero-structures by pulsed laser deposition (PLD) with laser rastering technique. The surface morphology, crystalline quality, and interfacial property of as-grown GaN films are characterized in detail. By optimizing the laser rastering program, the ~300 nm-thick GaN films grown at 750 °C show a root-mean-square (RMS) thickness inhomogeneity of 3.0%, very smooth surface with a RMS surface roughness of 3.0 nm, full-width at half-maximums (FWHMs) for GaN(0002) and GaN(102) X-ray rocking curves of 0.7° and 0.8°, respectively, and sharp and abrupt AlN/GaN hetero-interfaces. With the increase in the growth temperature from 550 to 850 °C, the surface morphology, crystalline quality, and interfacial property of as-grown ~300 nm-thick GaN films are gradually improved at first and then decreased. Based on the characterizations, the corresponding growth mechanisms of GaN films grown on AlN/Si hetero-structures by PLD with various growth temperatures are hence proposed. This work would be beneficial to understanding the further insight of the GaN films grown on Si(111) substrates by PLD for the application of GaN-based devices. PMID:26563573

  4. Thermoelectric transport and Hall measurements of low defect Sb2Te3 thin films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Zastrow, S.; Gooth, J.; Boehnert, T.; Heiderich, S.; Toellner, W.; Heimann, S.; Schulz, S.; Nielsch, K.

    2013-03-01

    Sb2Te3 has recently been an object of intensive research since its promising applicability in thermoelectric, in phase-change memory devices and as a topological insulator. In this work, we report highly textured Sb2Te3 thin films, grown by atomic layer deposition on Si/SiO2 wafers based on the reaction of SbCl3 and (Et3Si)2Te. The low deposition temperature at 80 °C allows the pre-patterning of the Sb2Te3 by standard lithography processes. A platform to characterize the Seebeck coefficient S, the electrical conductivity σ as well as the Hall coefficient RH on the same film has been developed. Comparing all temperature-dependent transport properties, three different conductive regions in the temperature range of 50-400 K are found. Room temperature values of S = 146 × 10-6 VK-1, σ = 104 Sm-1 and mobility µ = 270.5 × 10-4 m2 V-1 s-1 are determined. The low carrier concentration in the range of n = 2.4 × 1018 cm-3 at 300 K quantifies the low defect content of the Sb2Te3 thin films.

  5. Enhanced photocatalytic performance in atomic layer deposition grown TiO{sub 2} thin films via hydrogen plasma treatment

    SciTech Connect

    Sasinska, Alexander; Singh, Trilok; Wang, Shuangzhou; Mathur, Sanjay; Kraehnert, Ralph

    2015-01-15

    The authors report the effect of hydrogen plasma treatment on TiO{sub 2} thin films grown by atomic layer deposition as an effective approach for modifying the photoanode materials in order to enhance their photoelectrochemical performance. Hydrogen plasma treated TiO{sub 2} thin films showed an improved absorption in the visible spectrum probably due to surface reduction. XPS analysis confirmed the formation of Ti{sup 3+} states upon plasma treatment. Hydrogen plasma treatment of TiO{sub 2} films enhanced the measured photocurrent densities by a factor of 8 (1 mA/cm{sup 2} at 0.8 V versus normal hydrogen electrode) when compared to untreated TiO{sub 2} (0.12 mA/cm{sup 2}). The enhancement in photocurrent is attributed to the formation of localized electronic states in mid band-gap region, which facilitate efficient separation and transportation of photo excited charge carriers in the UV region of electromagnetic spectrum.

  6. Investigation on the structural properties of GaN films grown on La0.3Sr1.7AlTaO6 substrates

    NASA Astrophysics Data System (ADS)

    Wang, Wenliang; Zhou, Shizhong; Liu, Zuolian; Yang, Weijia; Lin, Yunhao; Qian, Huirong; Gao, Fangliang; Li, Guoqiang

    2014-04-01

    Gallium nitride (GaN) films with excellent structural, electrical and optical properties have been epitaxially grown on La0.3Sr1.7AlTaO6 (LSAT) (111) substrates by radio-frequency molecular beam epitaxy at low temperature. The GaN films grown at 500 °C exhibits high crystalline quality with the (0002) and (10-12) full width at half maximum of 0.056° and 0.071°. There is a maximum of 1.1-nm-thick interfacial layer existing between the as-grown GaN and LSAT (111) substrate, and the as-grown about 300-nm-thick GaN films are almost fully relaxed only with a 0.0094% in-plane tensile strain. Hall and photoluminescence (PL) measurements also reveal outstanding electrical and optical properties of the as-grown GaN films on LSAT. This achievement brings the prospect for achieving highly-efficient GaN-based optoelectronic devices on LSAT (111) substrates.

  7. Space-charge behavior of 'Thin-MOS' diodes with MBE-grown silicon films

    NASA Technical Reports Server (NTRS)

    Lieneweg, U.; Bean, J. C.

    1984-01-01

    Basic theoretical and experimental characteristics of a novel 'Thin-MOS' technology, which has promising aspects for integrated high-frequency devices up to several hundred gigahertz are presented. The operation of such devices depends on charge injection into undoped silicon layers of about 1000-A thickness, grown by molecular beam epitaxy on heavily doped substrates, and isolation by thermally grown oxides of about 100-A thickness. Capacitance-voltage characteristics measured at high and low frequencies agree well with theoretical ones derived from uni and ambipolar space-charge models. It is concluded that after oxidation the residual doping in the epilayer is less than approximately 10 to the 16th/cu cm and rises by 3 orders of magnitude at the substrate interface within less than 100 A and that interface states at the oxide interface can be kept low.

  8. Oxygen measurements in thin ribbon silicon. [edge-defined film-fed grown

    NASA Technical Reports Server (NTRS)

    Hyland, S. L.; Ast, D. G.; Baghdadi, A.

    1987-01-01

    The oxygen content of thin silicon ribbons grown by the dendritic web technique was measured using a modification of the ASTM method based on Fourier transform infrared spectroscopy. Web silicon was found to have a high oxygen content, ranging from 13 to 19 ppma, calculated from the absorption peak associated with interstitial oxygen and using the new ASTM conversion coefficient. The oxygen concentration changed by about 10 percent along the growth direction of the ribbon. In some samples, a shoulder was detected on the absorption peak. A similar shoulder in Czochralski grown material has been variously interpreted in the literature as due to a complex of silicon, oxygen, and vacancies, or to a phase of SiO2 developed along dislocations in the material. In the case of web silicon, it is not clear which is the correct interpretation.

  9. Electrochromism in surface modified crystalline WO3 thin films grown by reactive DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Karuppasamy, A.

    2013-10-01

    In the present work, tungsten oxide thin films were deposited at various oxygen chamber pressures (1.0-5.0 × 10-3 mbar) by maintaining the sputtering power density and argon pressure constant at 3.0 W/cm2 and 1.2 × 10-2 mbar, respectively. The role of surface morphology and porosity on the electrochromic properties of crystalline tungsten oxide thin films has been investigated. XRD and Raman studies reveal that all the samples post annealed at 450 ̊C in air for 3.0 h settle in monoclinic crystal system of tungsten oxide (W18O49). Though the phase of material is indifferent to oxygen pressure variations (PO2), morphology and film density shows a striking dependence on PO2. A systematic study on plasma (OES), morphology, optical and electrochromic properties of crystalline tungsten oxide reveal that the films deposited at PO2 of 2.0 × 10-3 mbar exhibit better coloration efficiency (58 cm2/C), electron/ion capacity (Qc: -25 mC/cm2), and reversibility (92%). This is attributed to the enhanced surface properties like high density of pores and fine particulates (100 nm) and to lesser bulk density of the film (ρ/ρo = 0.84) which facilitates the process of intercalation/de-intercalation of protons and electrons. These results show good promise toward stable and efficient crystalline tungsten oxide based electrochromic device applications.

  10. Characterization of ZnO film grown on polycarbonate by atomic layer deposition at low temperature

    SciTech Connect

    Lee, Gyeong Beom; Han, Gwon Deok; Shim, Joon Hyung; Choi, Byoung-Ho

    2015-01-15

    ZnO is an attractive material for use in various technological products such as phosphors, gas sensors, and transparent conductors. Recently, aluminum-doped zinc oxide has received attention as a potential replacement for indium tin oxide, which is one of the transparent conductive oxides used in flat panel displays, organic light-emitting diodes, and organic solar cells. In this study, the characteristics of ZnO films deposited on polycarbonate (PC) substrates by atomic layer deposition (ALD) are investigated for various process temperatures. The growth mechanism of these films was investigated at low process temperatures using x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). XRD and XPS were used to determine the preferred orientation and chemical composition of the films, respectively. Furthermore, the difference of the deposition mechanisms on an amorphous organic material, i.e., PC substrate and an inorganic material such as silicon was discussed from the viewpoint of the diffusion and deposition of precursors. The structure of the films was also investigated by chemical analysis in order to determine the effect of growth temperature on the films deposited by ALD.

  11. Etching Technique to Reveal Dislocations in Thin GaAs Films Grown on Si Substrates

    NASA Astrophysics Data System (ADS)

    Nishikawa, Hironobu; Soga, Tetsuo; Mikuriya, Nobuo; Jimbo, Takashi; Umeno, Masayoshi

    1988-02-01

    Dislocations in GaAs and GaAs/Si are revealed by the etching technique at room temperature. The etchant is composed of H2O, K2Cr2O7, HNO3, HCl and H2SO4. The dislocation density of GaAs grown on Si by MOCVD using GaP and strained layer superlattices is about 1× 106 cm-2.

  12. Superconductor-insulator phase transition in single-crystal La2-xSrxCuO4 films grown by the liquid-phase epitaxy method

    NASA Astrophysics Data System (ADS)

    Islam, A. T. M. Nazmul; Hitosugi, T.; Dudzik, E.; Hasegawa, T.; Ueda, S.; Takano, Y.; Islam, F. N.; Khan, M. K. R.; Islam, M. N.; Islam, A. K. M. A.; Watauchi, S.; Tanaka, I.

    2009-07-01

    We have studied epitaxial strain effect on superconductivity in single-crystal La2-xSrxCuO4 films grown by liquid-phase epitaxy method on (001) La2CuO4 substrates. Due to lattice mismatch the as-grown films suffer a compressive strain in the c axis and an orthorhombic tensile strain on the ab plane with almost no relaxation up to several micrometers thickness. Our results show that La2-xSrxCuO4 (0.10≤x≤0.15) , which is superconducting in the bulk at low temperatures, transforms to an insulating state under such strain.

  13. Resistance switching in a single-crystalline NiO thin film grown on a Pt0.8Ir0.2 electrode

    NASA Astrophysics Data System (ADS)

    Kawai, Masanori; Ito, Kimihiko; Shimakawa, Yuichi

    2009-07-01

    A single-crystalline NiO thin film was grown epitaxially on an atomically flat Pt0.8Ir0.2 bottom electrode layer grown epitaxially on a SrTiO3(100) substrate. The memory cells of the single-crystalline NiO thin film with Pt top electrodes showed unipolar resistance switching behaviors. The result demonstrates that a unipolar resistance switching is not a characteristic phenomenon in the polycrystalline NiO but it can also occur in the single-crystalline NiO.

  14. Properties of SnS thin films grown by physical vapour deposition

    NASA Astrophysics Data System (ADS)

    Ganchev, M.; Vitanov, P.; Sendova-Vassileva, M.; Popkirov, G.; Dikov, H.

    2016-02-01

    Thin films of tin sulfide (SnS) were prepared by thermal evaporation technique on glass substrates and on n-type Si substrate and their physical properties were studied. The phase of the obtained thin films before and after thermal treatment was confirmed by X-ray diffraction analysis and Raman spectra. Optical transmission and reflection spectra were measured in the wavelength range 300-1800 nm, and the data were used to determine the direct and indirect optical band gaps. Four-point measurements have revealed that SnS thin film exhibits p-type conduction. Current-voltage characteristics of the SnS/ n-Si structures demonstrate strong photosensitivity and photovoltaic effect. However, in order to be able to evaluate the potential applicability of this heterojunction for photovoltaic or electronic devices, further study and technological optimization has to be conducted.

  15. Photonic bandgap amorphous chalcogenide thin films with multilayered structure grown by pulsed laser deposition method

    NASA Astrophysics Data System (ADS)

    Zhang, Shao-qian; Němec, Petre; Nazabal, Virginie; Jin, Yu-qi

    2016-05-01

    Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication wavelength. The prepared multilayered thin films for reflectors show good compatibility. The microcavity structure consists of Ge25Ga5Sb10S65 (doped with Er3+) spacer layer surrounded by two 5-layer As40Se60/Ge25Sb5S70 reflectors. Scanning/transmission electron microscopy results show good periodicity, great adherence and smooth interfaces between the alternating dielectric layers, which confirms a suitable compatibility between different materials. The results demonstrate that the chalcogenides can be used for preparing vertical Bragg reflectors and microcavity with high quality.

  16. Ferromagnetic resonance of patterned chromium dioxide thin films grown by selective area chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Durrant, C. J.; Jokubaitis, M.; Yu, W.; Mohamad, H.; Shelford, L. R.; Keatley, P. S.; Xiao, Gang; Hicken, R. J.

    2015-05-01

    A selective area chemical vapour deposition technique has been used to fabricate continuous and patterned epitaxial CrO2 thin films on (100)-oriented TiO2 substrates. Precessional magnetization dynamics were stimulated both electrically and optically, and probed by means of time-resolved Kerr microscopy and vector network analyser ferromagnetic resonance techniques. The dependence of the precession frequency and the effective damping parameter upon the static applied magnetic field were investigated. All films exhibited a large in-plane uniaxial anisotropy. The effective damping parameter was found to exhibit strong field dependence in the vicinity of the hard axis saturation field. However, continuous and patterned films were found to possess generally similar dynamic properties, confirming the suitability of the deposition technique for fabrication of future spintronic devices.

  17. Structural properties of Cu2O epitaxial films grown on c-axis single crystal ZnO by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Gan, J.; Gorantla, S.; Riise, H. N.; Fjellvâg, Ø. S.; Diplas, S.; Løvvik, O. M.; Svensson, B. G.; Monakhov, E. V.; Gunnæs, A. E.

    2016-04-01

    Epitaxial Cu2O films grown by reactive and ceramic radio frequency magnetron sputtering on single crystalline ZnO (0001) substrates are investigated. The films are grown on both O- and Zn-polar surface of the ZnO substrates. The Cu2O films exhibit a columnar growth manner apart from a ˜5 nm thick CuO interfacial layer. In comparison to the reactively sputtered Cu2O, the ceramic-sputtered films are less strained and appear to contain nanovoids. Irrespective of polarity, the Cu2O grown by reactive sputtering is observed to have (111)Cu2O||(0001)ZnO epitaxial relationship, but in the case of ceramic sputtering the films are found to show additional (110)Cu2O reflections when grown on O-polar surface. The observed CuO interfacial layer can be detrimental for the performance of Cu2O/ZnO heterojunction solar cells reported in the literature.

  18. Multiferroic YCrO3 thin films grown on glass substrate: Resistive switching characteristics

    NASA Astrophysics Data System (ADS)

    Seo, Jeongdae; Ahn, Yoonho; Son, Jong Yeog

    2016-01-01

    Polycrystalline YCrO3 thin films were deposited on (111) Pt/Ta/glass substrates by pulsed laser deposition. The YCrO3 thin films exhibited good ferroelectric properties with remnant polarization of about 5 µC/cm2. Large leakage current was observed by I- V curve and ferroelectric hysteresis loop. The YCrO3 resistive random access memory (RRAM) capacitor showed unipolar switching behaviors with SET and RESET voltages higher than those of general NiO RRAM capacitors. [Figure not available: see fulltext.

  19. Tunable magnetic anisotropy in permalloy thin films grown on holographic relief gratings

    NASA Astrophysics Data System (ADS)

    Berendt, J.; Teixeira, J. M.; García-García, A.; Raposo, M.; Ribeiro, P. A.; Dubowik, J.; Kakazei, G. N.; Schmool, D. S.

    2014-02-01

    The aim of the present work is to show a simple method that combines conventional laser interferometry and standard thin film deposition techniques to fabricate modulated magnetic nanostructures with lateral periodicity, and to tailor the magnetic properties by varying geometrical parameters. Well defined Ni80Fe20 magnetic thin films with sinusoidal grating profiles were obtained with a periodicity of 1.2 μm and different grating depths. Magnetic studies via ferromagnetic resonance and magneto optical Kerr effect demonstrate the tunability of the induced in-plane magnetic anisotropy with depth profile.

  20. Stress generation in thermally grown oxide films. [oxide scale spalling from superalloy substrates

    NASA Technical Reports Server (NTRS)

    Kumnick, A. J.; Ebert, L. J.

    1981-01-01

    A three dimensional finite element analysis was conducted, using the ANSYS computer program, of the stress state in a thin oxide film thermally formed on a rectangular piece of NiCrAl alloy. The analytical results indicate a very high compressive stress in the lateral directions of the film (approximately 6200 MPa), and tensile stresses in the metal substrate that ranged from essentially zero to about 55 MPa. It was found further that the intensity of the analytically determined average stresses could be approximated reasonably well by the modification of an equation developed previously by Oxx for stresses induced into bodies by thermal gradients.

  1. Surface electronic structure of polar NiO thin film grown on Ag(111)

    NASA Astrophysics Data System (ADS)

    Das, Jayanta; Menon, Krishnakumar S. R.

    2015-06-01

    The growth and structure of NiO thin films on top of Ag(111) substrate were studied where the formation of faceted surface was confirmed by Low Energy Electron Diffraction. The electronic structure of polar NiO(111) surface has been probed using photoemission techniques. The core energy levels and the valence band electronic structure were excited by x-ray and ultraviolet photons respectively. The modifications in physical structure and valence band electronic structure of the film under vacuum annealing have also been enlightened.

  2. Thermal oxidation-grown vanadium dioxide thin films on FTO (Fluorine-doped tin oxide) substrates

    NASA Astrophysics Data System (ADS)

    Tong, Guoxiang; Li, Yi; Wang, Feng; Huang, Yize; Fang, Baoying; Wang, Xiaohua; Zhu, Huiqun; Li, Liu; Shen, Yujian; Zheng, Qiuxin; Liang, Qian; Yan, Meng; Qin, Yuan; Ding, Jie

    2013-11-01

    By deposition of metallic vanadium on FTO substrate in Argon atmosphere at room temperature, the sample was then annealed in furnace for 2 h at the temperature of 410 °C in air ambient. (1 1 0) -orientated vanadium dioxide films were prepared on the FTO surface. A maximum transmittance of ˜40% happened at 900-1250 nm region at room temperature. The change of optical transmittance at this region was ˜25% between semiconducting and metallic states. In particular, vanadium dioxide thin films on FTO exhibit semiconductor-metal phase transition at ˜51 °C, the width of the hysteresis loop is ˜8 °C.

  3. Surface electronic structure of polar NiO thin film grown on Ag(111)

    SciTech Connect

    Das, Jayanta; Menon, Krishnakumar S. R.

    2015-06-24

    The growth and structure of NiO thin films on top of Ag(111) substrate were studied where the formation of faceted surface was confirmed by Low Energy Electron Diffraction. The electronic structure of polar NiO(111) surface has been probed using photoemission techniques. The core energy levels and the valence band electronic structure were excited by x-ray and ultraviolet photons respectively. The modifications in physical structure and valence band electronic structure of the film under vacuum annealing have also been enlightened.

  4. Influence of a TiN interlayer on the microstructure and mechanical properties of hydroxyapatite films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Nelea, Valentin D.; Ristoscu, Carmen; Colis, Silviu; Arens, Simona; Pelletier, Herve; Mihailescu, Ion N.; Mille, Pierre

    2001-04-01

    Crystalline hydroxyapatite (HA) thin films grown on metallic substrates is the best choice for bone restoration. This is due to the good biological compatibility of the hydroxyapatite material combined with the good mechanical characteristics of the substrates. We deposit HA thin films by Pulsed Laser Deposition (PLD) in vacuum at room temperature using a KrF* excimer laser ((lambda) equals 248 nm, (tau) FWHM >= 20 ns). The depositions were performed directly on Ti-5Al-2.5Fe or on substrates previously coated with a TiN buffer layer. The HA deposited structures were characterized by complementary techniques: GIXRD, SEM, TEM, SAED, EDS and nanoindentation. Properties of the HA films grown with and without the TiN buffer were discussed in term of microstructure and mechanical behavior. The films with interlayer preserve the stoichiometry, are completely recrystallized and present better mechanical characteristics as compared with those without buffer.

  5. Electrophysical properties of Cd x Hg1- x Te ( x = 0.3) films grown by molecular beam epitaxy on Si(013) substrates

    NASA Astrophysics Data System (ADS)

    Varavin, V. S.; Marin, D. V.; Yakushev, M. V.

    2016-04-01

    The electrophysical properties of Cd x Hg1- x Te ( x ≈ 0.3) films undoped and doped with indium during their growth were investigated. The as-grown films were subjected to heat treatment in mercury vapor. The magnetic field dependences of the Hall effect in the magnetic field range of 0.05-1.0 T at 77 K were explained by the fact that, in the films, there are two types of electrons with high and low mobilities. The analysis of the temperature dependences of the minority carrier lifetime in the range of 77-300 K revealed that the as-grown films contain two types of traps with different energies. It was found that annealing at a saturated mercury vapor pressure increases the minority carrier lifetime due to the suppression of recombination centers, which can be associated with growth defects in Cd x Hg1- x Te/CdTe/Si heterostructures.

  6. Magnetically modulated refractive index of a magnetic fluid film based on cigar-shaped ferrite submicron particles

    NASA Astrophysics Data System (ADS)

    Mormile, P.; Petti, L.; Rippa, M.; Guo, J.; Song, W.; Zhou, J.

    2010-10-01

    Light beam propagation at a prism-magnetic fluid film interface is experimentally studied. The magnetic fluid is made through dispersion of synthesized cigar-shaped sub-micron particles of Fe2O3 in an oil solution. This was injected into a glass cell with an active area of 10mm2 and a depth ranging from 10 microns to 30 microns whose base is a glass microscope slide and on the top it was covered with a glass prism. The set up was developed by one of the authors to measure light switching at a prism-liquid crystal interface in a previous publication.1 Polarized Light (TE or TM) from a He-Ne laser impinges at the prism-magnetic film interface. The external reflected light is detected by a photodiode connected to a data acquisition system. Since the properties of the magnetic fluid can be modulated by external magnetic fields, we investigated the effects of the magnetic field on the refractive index of the magnetic fluid. For our magnetic fluid, the reflection of light has been investigated as a function of particles concentration and thickness of the films with a wavelength of 633nm and both TE and TM polarization, and applied magnetic fields up to 25 Oe. It was found that the intensity of reflected light increases with increasing magnetic field up to 4 times the initial value, and saturates at 20 Oe for TE light, while decreases with increasing magnetic field up to 4 times less for TM light with the same saturation value. Moreover, under a given magnetic field, the output light increases with the increasing film thickness in TE polarization, and decreases with the increasing film thickness in TM case. The refractive index of the magnetic fluid depends on the concentration of the dilute oil-based magnetic fluid under zero field. These behaviors are explained in terms of the organization of the submicron particles when the magnetic field is applied.2 The cigar-shaped sub-micron particles are oriented along their long axis to form an organized mesostructure. The

  7. A comparative investigation on structure and multiferroic properties of bismuth ferrite thin films by multielement co-doping

    SciTech Connect

    Dong, Guohua; Tan, Guoqiang Luo, Yangyang; Liu, Wenlong; Xia, Ao; Ren, Huijun

    2014-12-15

    Highlights: • Multielement (Tb, Cr and Mn) co-doped BiFeO{sub 3} films were fabricated by CSD method. • Multielement co-doping induces a structural transition. • It is found effective to stabilize the valence of Fe ions at +3 by the strategy. • The co-doping at A/B-sites gives rise to the superior multiferroic properties. - Abstract: (Tb, Cr and Mn) multielement co-doped BiFeO{sub 3} (BTFCMO) thin films were prepared by the chemical solution deposition method on fluorine doped tin oxide (FTO) substrates. X-ray diffraction, Rietveld refinement and Raman analyses revealed that a phase transition from rhombohedral to triclinic structure occurs in the multielement co-doped BiFeO{sub 3} films. It is found that the doping is conducive to stabilizing the valence of Fe ions and reducing leakage current. In addition, the highly enhanced ferroelectric properties with a huge remanent polarization (2P{sub r}) of 239.6 μC/cm{sup 2} and a low coercive field (2E{sub c}) of 615.6 kV/cm are ascribed to the well film texture, the structure transition and the reduced leakage current by the co-doping. Moreover, the structure transition is the dominant factor resulting in the significant enhancement observed in magnetization (M{sub s} ∼ 10.5 emu/cm{sup 3}), owing to the collapse of the space-modulated spin structure. In this contribution, these results demonstrate that the multielement co-doping is in favor of the enhanced multiferroic properties of the BFO films for possible multifunctional applications.

  8. ZnO film with ultra-low background electron concentration grown by plasma-assisted MBE using Mg film as the buffer layer

    SciTech Connect

    Chen, Mingming; Zhang, Quanlin; Su, Longxing; Su, Yuquan; Cao, Jiashi; Zhu, Yuan; Wu, Tianzhun; Gui, Xuchun; Yang, Chunlei; Xiang, Rong; Tang, Zikang

    2012-09-15

    Highlights: ► High quality ZnO film with ultra-low background electron concentration is grown by plasma-assisted molecular beam epitaxy using Mg film as a buffer layer. ► High resolution X-ray diffraction and photoluminescence (PL) spectroscopy indicate a high degree of crystallization. ► Hall measurement shows a carrier concentration as low as ∼10{sup 14} cm{sup −3}. ► The mechanism of the improved crystallinity is discussed in detail. -- Abstract: High quality ZnO epilayer with background electron concentration as low as 2.6 × 10{sup 14} cm{sup −3} was obtained by plasma-assisted MBE on c-sapphire using a thin Mg film as the buffer layer. High-resolution XRD measurement shows a sharp (0 0 2) peak with full width at half maximum (FWHM) of only 0.029°. Photoluminescence spectroscopy presents a weak defect-related near-edge emission. A metal–semiconductor–metal (MSM) typed photodetector based on the material demonstrates a response of ∼43 A/W under the bias of 1 V and an ON/OFF ratio of 10{sup 4}. This un-doped ZnO with ultra-low background electron concentration could be a promising starting material for p-type doping.

  9. Local Structures and Interface Morphology of InGaAsN Thin Films Grown on GaAs

    SciTech Connect

    Allerman, A.A.; Chen, J.G.; Geisz, J.F.; Huang, S.; Hulbert, S.L.; Jones, E.D.; Kao, Y.H.; Kurtz, S.; Kurtz, S.R.; Olson, J.M.; Soo, Y.L.

    1999-02-23

    The compound semiconductor system InGaAsN exhibits many intriguing properties which are particularly useful for the development of innovative high efficiency thin film solar cells and long wavelength lasers. The bandgap in these semiconductors can be varied by controlling the content of N and In and the thin films can yet be lattice-matched to GaAs. In the present work, x-ray absorption fine structure (XAFS) and grazing incidence x-ray scattering (GIXS) techniques have been employed to probe the local environment surrounding both N and In atoms as well as the interface morphology of InGaAsN thin films epitaxially grown on GaAs. The soft x-ray XAFS results around nitrogen K-edge reveal that N is in the sp{sup 3} hybridized bonding configuration in InGaAsN and GaAsN, suggesting that N impurities most likely substitute for As sites in these two compounds. The results of In K-edge XAFS suggest a possible trend of a slightly larger coordination number of As nearest neighbors around In atoms in InGaAsN samples with a narrower bandgap whereas the In-As interatomic distance remains practically the same as in InAs within the experimental uncertainties. These results combined suggest that N-substitution of the As sites plays an important role of bandgap-narrowing while in the meantime counteracting the compressive strain caused by In-doping. Grazing incidence x-ray scattering (GIXS) experiments verify that InGaAsN thin films can indeed form very smooth interfaces with GaAs yielding an average interfacial roughness of 5-20{angstrom}.

  10. Positron beam and RBS studies of thermally grown oxide films on stainless steel grade 304

    NASA Astrophysics Data System (ADS)

    Horodek, P.; Siemek, K.; Kobets, A. G.; Kulik, M.; Meshkov, I. N.

    2015-04-01

    The formation of oxide films on surfaces of stainless steel 304 AISI annealed at 800 °C in vacuum, air and in flow N2 atmospheres was studied using variable energy positron beam technique (VEP) and Rutherford backscattering/nuclear reaction (RBS/NR) methods. In frame of these studies, Doppler broadening of annihilation line (DB) measurements were performed. For a sample heated in vacuum the oxide film ca. 8 nm is observed. For specimens oxidized in air and N2 the multi-layered oxide films of about a few hundred nanometers are recognized. The RBS/NR measurements have shown that the sample annealed in vacuum contains a lower quantity of oxygen while for samples heated in the air and N2 non-linear and rather linear time-dependency are observed, respectively. The thicknesses of total oxide films obtained from RBS/NR tests are in good agreement with the VEP results. Time evolution of the oxide growing was studied as well.

  11. Graphene synthesis from graphite/Ni composite films grown by sputtering

    NASA Astrophysics Data System (ADS)

    Shin, Dong Hee; Yang, Seung Bum; Shin, Dong Yeol; Kim, Chang Oh; Kim, Sung; Choi, Suk-Ho; Paek, Sang-Hyon

    2012-08-01

    Graphite/Ni composite films have been deposited on SiO2/Si (100) wafers by varying their graphite concentration ( n G ) and thickness (t) from 2 to 12 wt% and 40 to 400 nm, respectively, in a RF sputtering system, subsequently annealed at 900 °C for 4 min, and then slowly cooled to room temperature to form graphene layers on Ni surfaces. Several structural-analysis techniques reveal the optimum n G (˜8 wt%) and t (˜160 nm) of the composite films for the synthesis of fewest-layer, defect-minimized graphene. At the annealing temperature, carbon atoms diffuse out from the composite film, followed by their precipitation as graphene on the Ni layer as the carbon solubility limit in Ni is reached during the cooling period. Based on this mechanism, the optimum conditions are explained. Our approach provides an advantage in that the number of layers can be simply tuned by varying n G and t of the composite films.

  12. Interface study between nanostructured tantalum nitride films and carbon nanotubes grown by chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Bouchet-Fabre, B.; Pinault, M.; Foy, E.; Hugon, M. C.; Minéa, T.; Mayne-L'Hermite, M.

    2014-10-01

    We present the role of nitrogen content in tantalum nitride ultra-thin buffers, on the carbon nanotubes (CNTs) growth by chemical vapour deposition at 850 °C, assisted by ferrocene as catalyst source. Tantalum nitride (TaNx) films with a very large range of concentration x = [0, 1.8] and various nanostructures, from amorphous Ta(N) to Ta3N5, were deposited by Highly Pulsed Plasma Magnetron Sputtering. The buffer films are characterized after heat treatment at 850 °C, and after the CNT growth, by wide angle X-ray scattering in grazing incidence and scanning electron microscopy. The CNT diameter explored by transition electron microscopy shows an all-out value for under stoichiometric thin films (Ta1-N1-δ, Ta3-N5-δ) and a minimum value just above the stoichiometric phases (Ta1-N1+δ, Ta3-N5+δ). Firstly one shows that the buffer films under the heat treatment present surface modification highly dependent on their initial state, which influences the catalyst particles diffusion. Secondly at the stoichiometric TaN phase we show that a specific ternary phase FeTa2O6 is formed at the interface CNT/buffer, not present in the other cases, leading to a special CNT growth condition.

  13. Antimony-Doped Tin Oxide Thin Films Grown by Home Made Spray Pyrolysis Technique

    NASA Astrophysics Data System (ADS)

    Yusuf, Gbadebo; Babatola, Babatunde Keji; Ishola, Abdulahi Dimeji; Awodugba, Ayodeji O.; Solar cell Collaboration

    2016-03-01

    Transparent conducting antimony-doped tin oxide (ATO) films have been deposited on glass substrates by home made spray pyrolysis technique. The structural, electrical and optical properties of the ATO films have been investigated as a function of Sb-doping level and annealing temperature. The optimum target composition for high conductivity and low resistivity was found to be 20 wt. % SnSb2 + 90 wt. ATO. Under optimized deposition conditions of 450oC annealing temperature, electrical resistivity of 5.2×10-4 Ω -cm, sheet resistance of 16.4 Ω/sq, average optical transmittance of 86% in the visible range, and average optical band-gap of 3.34eV were obtained. The film deposited at lower annealing temperature shows a relatively rough, loosely bound slightly porous surface morphology while the film deposited at higher annealing temperature shows uniformly distributed grains of greater size. Keywords: Annealing, Doping, Homemade spray pyrolysis, Tin oxide, Resistivity

  14. Magnetic Properties of FePt based Nanocomposite Thin Films Grown on Low Cost Substrates

    NASA Astrophysics Data System (ADS)

    Gayen, A.; Biswas, B.; Singh, A. K.; Saravanan, P.; Perumal, A.

    We report a systematic investigation of temperature dependent magnetic properties of FePt single and FePt(30)/M/Fe(5) nanocomposite thin films prepared by sputtering technique on low cost substrates at ambient temperature and post annealed at different temperatures. With increasing annealing temperature, L10 ordering, hard magnetic properties and thermal stability of FePt films are improved. The formation of interlayer exchange coupling between hard and soft magnetic layers in FePt/M(Al,Cu,C)/Fe films depends strongly on interlayer materials and interface morphology. A strong interlayer exchange coupling was achieved when the C interlayer thickness was about 0.5 nm, which enhances saturation magnetization largely. Also, the magnetization reversal process changes from incoherent to coherent switching process, which results a single hysteresis loop. High temperature magnetic studies revealed that the effective reduction in the coercivity decreases from 34 Oe/K to 13 Oe/K by the introduction of a thin C(0.5 nm) layer in FePt/C/Fe film. This reveals a promising approach to improve the stability of hard magnetic properties at high temperatures, suitable for high temperature magnetic applications.

  15. Microstructure comparison between KNbO 3 thin films grown by polymeric precursors and PLD methods

    NASA Astrophysics Data System (ADS)

    Weber, I. T.; Rousseau, A.; Guilloux-Viry, M.; Bouquet, V.; Perrin, A.

    2005-11-01

    KNbO 3 (KN) thin films were prepared by both Pulsed Laser Deposition (PLD) and Polymeric Precursor Route (PPR) onto polycrystalline alumina (Al 2O 3) and single-crystalline (100) SrTiO 3 substrates. Structural and microstructural characteristics of the thin films were determined by X-ray diffraction, field emission scanning electronic microscopy and electron channeling patterns in order to establish a correlation between the preparation method and the samples characteristics. It was evidenced that both methods are able to produce well crystallized single phase films presenting an epitaxial growth along 110 direction onto (100) SrTiO 3 substrates. PLD led to a highest crystalline quality ( Δω˜0.25° for PLD and Δω˜1° for PPR), while PPR provides crystallization at lower temperatures, without the appearance of secondary phases. The most remarkable difference between the methods concerns the film morphology (grain size and shape). In fact, deposition by these two routes gives access to various microstructures which open the way to specific study of physical behavior which currently depends on it.

  16. Photovoltaic properties of Bi2FeCrO6 films epitaxially grown on (100)-oriented silicon substrates

    NASA Astrophysics Data System (ADS)

    Nechache, R.; Huang, W.; Li, S.; Rosei, F.

    2016-02-01

    We demonstrate the promising potential of using perovskite Bi2FeCrO6 (BFCO) for niche applications in photovoltaics (PV) (e.g. self-powered sensors that simultaneously exploit PV conversion and multiferroic properties) or as a complement to mature PV technologies like silicon. BFCO thin films were epitaxially grown on silicon substrates using an MgO buffer layer. Piezoresponse force microscopy measurements revealed that the tensile strained BFCO phase exhibits a polarization predominantly oriented through the in-plane direction. The semiconducting bandgap of the ordered BFCO phase combined with ferroelectric properties, opens the possibility of a ferroelectric PV efficiency above 2% in a thin film device and the use of ferroelectric materials simultaneously as solar absorber layers and carrier separators in PV devices. A large short circuit photocurrent density of 13.8 mA cm-2 and a photovoltage output of 0.5 V are typically obtained at FF of 38% for BFCO devices fabricated on silicon. We believe that the reduced photovoltage is due to the low diffusion length of photogenerated charge carriers in the BFCO material where the ferroelectric domains are predominately oriented in-plane and thus do not contribute efficiently to the photocharge separation process.We demonstrate the promising potential of using perovskite Bi2FeCrO6 (BFCO) for niche applications in photovoltaics (PV) (e.g. self-powered sensors that simultaneously exploit PV conversion and multiferroic properties) or as a complement to mature PV technologies like silicon. BFCO thin films were epitaxially grown on silicon substrates using an MgO buffer layer. Piezoresponse force microscopy measurements revealed that the tensile strained BFCO phase exhibits a polarization predominantly oriented through the in-plane direction. The semiconducting bandgap of the ordered BFCO phase combined with ferroelectric properties, opens the possibility of a ferroelectric PV efficiency above 2% in a thin film device and the

  17. Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates

    NASA Astrophysics Data System (ADS)

    Braccini, V.; Kawale, S.; Reich, E.; Bellingeri, E.; Pellegrino, L.; Sala, A.; Putti, M.; Higashikawa, K.; Kiss, T.; Holzapfel, B.; Ferdeghini, C.

    2013-10-01

    We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF2(001) substrate. High critical current density values - larger than 1 MA/cm2 in self field and liquid helium - are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through transmission electron microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what was observed on SrTiO3, where defects parallel to the c-axis enhance pinning in that direction.

  18. Enzyme biosensor based on plasma-polymerized film-covered carbon nanotube layer grown directly on a flat substrate.

    PubMed

    Muguruma, Hitoshi; Hoshino, Tatsuya; Matsui, Yasunori

    2011-07-01

    We report a novel approach to fabrication of an amperometric biosensor with an enzyme, a plasma-polymerized film (PPF), and carbon nanotubes (CNTs). The CNTs were grown directly on an island-patterned Co/Ti/Cr layer on a glass substrate by microwave plasma enhanced chemical vapor deposition. The as-grown CNTs were subsequently treated by nitrogen plasma, which changed the surface from hydrophobic to hydrophilic in order to obtain an electrochemical contact between the CNTs and enzymes. A glucose oxidase (GOx) enzyme was then adsorbed onto the CNT surface and directly treated with acetonitrile plasma to overcoat the GOx layer with a PPF. This fabrication process provides a robust design of CNT-based enzyme biosensor, because of all processes are dry except the procedure for enzyme immobilization. The main novelty of the present methodology lies in the PPF and/or plasma processes. The optimized glucose biosensor revealed a high sensitivity of 38 μA mM(-1) cm(-2), a broad linear dynamic range of 0.25-19 mM (correlation coefficient of 0.994), selectivity toward an interferent (ascorbic acid), and a fast response time of 7 s. The background current was much smaller in magnitude than the current due to 10 mM glucose response. The low limit of detection was 34 μM (S/N = 3). All results strongly suggest that a plasma-polymerized process can provide a new platform for CNT-based biosensor design. PMID:21678995

  19. Atomic probe microscopy of 3C SiC films grown on 6H SiC substrates

    NASA Technical Reports Server (NTRS)

    Steckl, A. J.; Roth, M. D.; Powell, J. A.; Larkin, D. J.

    1993-01-01

    The surface of 3C SiC films grown on 6H SiC substrates has been studied by atomic probe microscopy in air. Atomic-scale images of the 3C SiC surface have been obtained by STM which confirm the 111 line type orientation of the cubic 3C layer grown on the 0001 plane type surface of the hexagonal 6H substrate. The nearest-neighbor atomic spacing for the 3C layer has been measured to be 3.29 +/- 0.2 A, which is within 7 percent of the bulk value. Shallow terraces in the 3C layer have been observed by STM to separate regions of very smooth growth in the vicinity of the 3C nucleation point from considerably rougher 3C surface regions. These terraces are oriented at right angles to the growth direction. Atomic force microscopy has been used to study etch pits present on the 6H substrate due to high temperature HCl cleaning prior to CVD growth of the 3C layer. The etch pits have hexagonal symmetry and vary in depth from 50 nm to 1 micron.

  20. Electrical and physicochemical properties of atomic-layer-deposited HfO2 film on Si substrate with interfacial layer grown by nitric acid oxidation

    NASA Astrophysics Data System (ADS)

    Kim, Seung Hyun; Seok, Tae Jun; Jin, Hyun Soo; Kim, Woo-Byoung; Park, Tae Joo

    2016-03-01

    The ultrathin SiO2 interfacial layer (IL) was adopted at the interface between atomic-layer-deposited HfO2 gate dielectric film and a Si substrate, which was grown using nitric acid oxidation (NAO) and O3 oxidation (OZO) prior to HfO2 film deposition. X-ray photoelectron spectroscopy result revealed that Si diffusion from the substrate into the film was suppressed for the film with NAO compared to that with OZO, which was attributed to the higher physical density of IL. The electrical measurement using metal-insulator-semiconductor devices showed that the film with NAO exhibited higher effective permittivity and lower densities of fixed charge and slow state at the interface. Furthermore, the leakage current density at an equivalent electrical thickness was lower for the film with NAO than OZO.

  1. Synthesis of nanocrystalline Cu{sub 2}ZnSnS{sub 4} thin films grown by the spray-pyrolysis technique

    SciTech Connect

    Chandel, Tarun Singh, Joginder; Rajaram, P.

    2015-08-28

    Spray pyrolysis was used to deposit Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films on soda lime glass substrates at 300 °C. Aqueous solutions of copper chloride, zinc chloride, stannous chloride and thiourea were mixed together to form the spray liquid. The sprayed films were annealed under vacuum at 350 °C, 400 °C and 450 °C. Structural and optical characterization was performed on the CZTS films using X-ray diffraction (XRD) and UV-VIS spectrophotometry. XRD results indicate that the films are single phase nanocrystalline CZTS. Optical studies show that the optical gap values are 1.44 eV for the as-grown film and 1.46 eV, 1.48 eV and 1.49 eV for the films annealed at 350 °C, 400 °C and 450 °C, respectively.

  2. Realization of compressively strained GaN films grown on Si(110) substrates by inserting a thin AlN/GaN superlattice interlayer

    SciTech Connect

    Shen, X. Q.; Takahashi, T.; Kawashima, H.; Ide, T.; Shimizu, M.

    2012-07-16

    We investigate the strain properties of GaN films grown by plasma-assisted molecular beam epitaxy on Si(110) substrates. It is found that the strain of the GaN film can be converted from a tensile to a compressive state simply by inserting a thin AlN/GaN superlattice structure (SLs) within the GaN film. The GaN layers seperated by the SLs can have different strain states, which indicates that the SLs plays a key role in the strain modulation during the growth and the cooling down processes. Using this simple technique, we grow a crack-free GaN film exceeding 2-{mu}m-thick. The realization of the compressively strained GaN film makes it possible to grow thick GaN films without crack generation on Si substrates for optic and electronic device applications.

  3. Surface plasmon resonances of Ag-Au alloy nanoparticle films grown by sequential pulsed laser deposition at different compositions and temperatures

    SciTech Connect

    Verma, Shweta Rao, B. T.; Detty, A. P.; Kukreja, L. M.; Ganesan, V.; Phase, D. M.; Rai, S. K.; Bose, A.; Joshi, S. C.

    2015-04-07

    We studied localized surface plasmon resonances (LSPR) at different compositions, substrate temperatures, and mass thicknesses of Ag-Au alloy nanoparticle films grown by sequential pulsed laser deposition. The LSPRs were pronounced at all compositions of the films grown at high substrate temperature of about 300 °C as compared to those grown at room temperature. The alloy formation and composition of the films were determined using X-ray photoelectron and energy dispersive spectroscopy. Films' mass thickness and compositional uniformity along the thickness were determined using X-ray reflectometry and secondary ion mass spectroscopy. Atomic force microscopic analysis revealed the formation of densely packed nanoparticles of increasing size with the number of laser ablation pulses. The LSPR wavelength red shifted with increasing either Au percentage or film mass thickness and corresponding LSPR tuning was obtained in the range of 450 to 690 nm. The alloy dielectric functions obtained from three different models were compared and the optical responses of the nanoparticle films were calculated from modified Yamaguchi effective medium theory. The tuning of LSPR was found to be due to combined effect of change in intrinsic and extrinsic parameters mainly the composition, morphology, particle-particle, and particle-substrate interactions.

  4. Correlation of growth temperature with stress, defect states and electronic structure in an epitaxial GaN film grown on c-sapphire via plasma MBE.

    PubMed

    Krishna, Shibin; Aggarwal, Neha; Mishra, Monu; Maurya, K K; Singh, Sandeep; Dilawar, Nita; Nagarajan, Subramaniyam; Gupta, Govind

    2016-03-21

    The relationship of the growth temperature with stress, defect states, and electronic structure of molecular beam epitaxy grown GaN films on c-plane (0001) sapphire substrates is demonstrated. A minimum compressively stressed GaN film is grown by tuning the growth temperature. The correlation of dislocations/defects with the stress relaxation is scrutinized by high-resolution X-ray diffraction and photoluminescence measurements which show a high crystalline quality with significant reduction in the threading dislocation density and defect related bands. A substantial reduction in yellow band related defect states is correlated with the stress relaxation in the grown film. Temperature dependent Raman analysis shows the thermal stability of the stress relaxed GaN film which further reveals a downshift in the E2 (high) phonon frequency owing to the thermal expansion of the lattice at elevated temperatures. Electronic structure analysis reveals that the Fermi level of the films is pinned at the respective defect states; however, for the stress relaxed film it is located at the charge neutrality level possessing the lowest electron affinity. The analysis demonstrates that the generated stress not only affects the defect states, but also the crystal quality, surface morphology and electronic structure/properties. PMID:26916430

  5. The magnetic properties of strained and relaxed Fe{sub 3-x}Mg{sub x}O{sub 4} ferrite films on MgO(001) and SrTiO{sub 3}(001) by molecular beam epitaxy

    SciTech Connect

    Lee, D. S.; Wang, J. S.; Modak, Dilip K.; Liu, Y. S.; Chang, C. L.; Chern, G.

    2007-05-01

    The present study grows a series of Fe{sub 3-x}Mg{sub x}O{sub 4} (0IExIE1.5) films and systematically measure both structure and magnetization of these films. These films are grown on MgO and SrTiO{sub 3} (STO), which have small ({approx}-0.3%) and large ({approx}7.5%) lattice mismatch in order to have either strained or relaxed films, by plasma-oxygen-assisted molecular beam epitaxy, respectively. X-ray diffraction (XRD) is carried out to analyze the crystalline structure. Saturation magnetization (M{sub s}) of pure Fe{sub 3}O{sub 4} (x=0) on both substrates is {approx}500 emu/cm{sup 3}, which is consistent with the bulk value. However, M{sub s} has a fast decrease with increasing x for the films grown on MgO(001), from 340 to {approx}100 emu/cm{sup 3} in the region of 0.31.35. On the other hand, M{sub s} remains unchanged with x increasing from 0.3 to 1 for the film grown on STO. With x>1, M{sub s} drops abruptly to {approx}100 emu/cm{sup 3}, which is comparable to M{sub s} of the film grown on MgO. The discrepancy in M{sub s} of Fe{sub 3-x}Mg{sub x}O{sub 4} film grown on MgO and STO may imply that the cation distribution of these films may be fundamentally different. Possible cation distribution and the substrate strain effect will be discussed.

  6. Analysis of scattering mechanisms in zinc oxide films grown by the atomic layer deposition technique

    SciTech Connect

    Krajewski, Tomasz A. Dybko, Krzysztof; Luka, Grzegorz; Wachnicki, Lukasz; Kopalko, Krzysztof; Paszkowicz, Wojciech; Guziewicz, Elzbieta

    2015-07-21

    In this work, the analysis of the temperature-dependent electrical conductivity of highly crystalline zinc oxide (ZnO) thin films obtained by the Atomic Layer Deposition (ALD) method is performed. It is deduced that the most important scattering mechanisms are: scattering by ionized defects (at low temperatures) as well as by phonons (mainly optical ones) at higher temperatures. Nevertheless, the role of grain boundaries in the carrier mobility limitation ought to be included as well. These conclusions are based on theoretical analysis and temperature-dependent Hall mobility measurements. The presented results prove that existing models can explain the mobility behavior in the ALD-ZnO films, being helpful for understanding their transport properties, which are strongly related both to the crystalline quality of deposited ZnO material and defects in its lattice.

  7. Absorption enhancement of ZnPc thin films grown on nano-patterned polymer underlayer

    NASA Astrophysics Data System (ADS)

    Han, Jiyeong; Lee, Jinho; Yim, Sanggyu

    2013-11-01

    We developed a simple and efficient nanoimprinting technique based on the capillary force lithography to fabricate two-dimensional arrays of nanoholes on the surface of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layers. A replicated polymer mold was used as the imprinting stamp, and the surface nanopatterns were formed by capillary rise of the moist PEDOT:PSS solution. The nanopatterned PEDOT:PSS layer could refract the incident light, thereby increasing the path lengths of the light passing through the zinc phthalocyanine (ZnPc) films deposited on the PEDOT:PSS layer. As a result, the absorbance of the ZnPc films was enhanced by up to ∼14% in parts of the absorbance range of ZnPc.

  8. Noble gas incorporation in sputtered and ion beam assisted grown silicon films

    SciTech Connect

    van Veen, A. . Inter-Faculty Reactor Inst.); Greuter, M.J.W.; Niesen, L. . Dept. of Physics); Nielsen, B.; Lynn, K.G. )

    1991-01-01

    Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

  9. Noble gas incorporation in sputtered and ion beam assisted grown silicon films

    SciTech Connect

    van Veen, A.; Greuter, M.J.W.; Niesen, L.; Nielsen, B.; Lynn, K.G.

    1991-12-31

    Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

  10. Manganese phosphide thin films and nanorods grown on gallium phosphide and on glass substrates

    NASA Astrophysics Data System (ADS)

    Nateghi, N.; Lambert-Milot, S.; Ménard, D.; Masut, R. A.

    2016-05-01

    We report a simple and fast route to grow ferromagnetic manganese phosphide polycrystalline films and nanorods on GaP and on glass substrates using metalorganic vapor phase deposition. Increasing the growth temperature (≥600 °C) and growth time (≥30 min) results in nucleation of secondary MnP crystals on the primary grains. The secondary crystals grow faster along a specific direction of orthorhombic MnP (c-axis) and form long rods (up to ~10 μm) whose diameters are in the nanoscale (20-100 nm). The nanorods can be easily detached from the glass substrate. The films exhibit ferromagnetic behavior with a range of transition temperatures, depending on the growth conditions.

  11. Persistence of superconductivity in niobium ultrathin films grown on R-plane sapphire

    NASA Astrophysics Data System (ADS)

    Delacour, Cécile; Ortega, Luc; Faucher, Marc; Crozes, Thierry; Fournier, Thierry; Pannetier, Bernard; Bouchiat, Vincent

    2011-04-01

    We report on a combined structural and electronic analysis of niobium ultrathin films (from 2 to 10 nm) deposited in ultrahigh vacuum on atomically flat R-plane sapphire wafers. A textured polycrystalline morphology is observed for the thinnest films, showing that heteroepitaxy is not achieved under a thickness of 3.3 nm, which almost coincides with the first measurement of a superconducting state. The superconducting critical temperature rise takes place on a very narrow thickness range, of the order of a single monolayer (ML). The thinnest superconducting sample (3 nm/9 ML) has an offset critical temperature above 4.2 K and can be processed by standard nanofabrication techniques to generate air- and time-stable superconducting nanostructures, useful for quantum devices.

  12. Structural Properties and Resistance-Switching Behavior of Thermally Grown NiO Thin Films

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Wook; Jung, Ranju; Park, Bae Ho; Li, Xiang-Shu; Park, Chanwoo; Shin, Seongmo; Kim, Dong-Chirl; Lee, Chang Won; Seo, Sunae

    2008-03-01

    We investigated the structural and electrical properties of polycrystalline NiO thin films on Pt electrodes formed by thermal oxidation. A Ni-Pt alloy phase was found at the interface, which could be explained by the oxidation kinetics and reactions of Ni, NiO, and Pt. An increase in the oxidation temperature decreased the volume of the alloy layer and improved the crystalline quality of the NiO thin films. Pt/NiO/Pt structures were fabricated, and they showed reversible resistance switching from a high-resistance state (HRS) to a low-resistance state (LRS) and vice versa during unipolar current-voltage measurements. The oxidation temperature affected (did not affect) the HRS (LRS) resistance of the Pt/NiO/Pt structures. This indicated that the transport characteristics of HRS and LRS should be different.

  13. Intrinsically tunable bulk acoustic wave resonators based on sol-gel grown PMN-PT films

    NASA Astrophysics Data System (ADS)

    Vorobiev, A.; Spreitzer, M.; Veber, A.; Suvorov, D.; Gevorgian, S.

    2014-08-01

    Intrinsically tunable bulk acoustic wave resonators, based on sol-gel 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) thin films, with high effective electromechanical coupling coefficient of 13% and tunability of the series resonance frequency up to 4.0% are fabricated and characterized. The enhanced electroacoustic properties of the PMN-PT resonators are attributed to the mechanism of polarization rotation occurring in the region of the morphotropic phase boundary. Electroacoustic performance of the PMN-PT resonators is analyzed using the theory of dc field-induced piezoelectric effect in ferroelectrics. Extrinsic acoustic loss in the PMN-PT resonators is analyzed using the model of the wave scattering at reflections from rough interfaces. Mechanical Q-factor of the resonators is up to 70 at 4.1 GHz and limited mainly by losses in the PMN-PT film.

  14. Efficient photovoltaic conversion of graphene-carbon nanotube hybrid films grown from solid precursors

    NASA Astrophysics Data System (ADS)

    Gan, Xin; Lv, Ruitao; Bai, Junfei; Zhang, Zexia; Wei, Jinquan; Huang, Zheng-Hong; Zhu, Hongwei; Kang, Feiyu; Terrones, Mauricio

    2015-09-01

    Large-area (e.g. centimeter size) graphene sheets are usually synthesized via pyrolysis of gaseous carbon precursors (e.g. methane) on metal substrates like Cu using chemical vapor deposition (CVD), but the presence of grain boundaries and the residual polymers during transfer deteriorates significantly the properties of the CVD graphene. If carbon nanotubes (CNTs) can be covalently bonded to graphene, the hybrid system could possess excellent electrical conductivity, transparency and mechanical strength. In this work, conducting and transparent CNT-graphene hybrid films were synthesized by a facile solid precursor pyrolysis method. Furthermore, the synthesized CNT-graphene hybrid films display enhanced photovoltaic conversion efficiency when compared to devices based on CNT membranes or graphene sheets. Upon chemical doping, the graphene-CNT/Si solar cells reveal power conversion efficiencies up to 8.50%.

  15. Effect of Ni content on the structural, morphological and magnetic properties of spray deposited Ni–Zn ferrite thin films

    SciTech Connect

    Kumbhar, S.S.; Mahadik, M.A.; Mohite, V.S.; Hunge, Y.M.; Rajpure, K.Y.; Bhosale, C.H.

    2015-07-15

    Graphical abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) thin films were prepared by spray pyrolysis technique onto the quartz substrates. The composition x = 0.4 shows the formation of the compact grain structure and highest saturation magnetization of 143 emu/cm{sup 3}. - Highlights: • Synthesis of nanocrystalline Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films. • Influence of Ni substitution on physicochemical properties. • Electrical conductivity arises mainly from the grain boundary. • The highest saturation magnetization is 143 emu/cm{sup 3} for x = 0.4. - Abstract: The Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} thin films have been prepared using a simple spray pyrolysis technique. The X-ray diffraction studies reveal that, the films are polycrystalline with spinel structure. The lattice parameters vary in the range of 8.35–8.48 Å with composition (x) obeying Vegard’s rule. SEM and AFM studies show that the surface of the films exhibit a smooth, compact and a pin hole free morphology. Raman spectra indicate first order Raman active modes; A{sub 1g} (λ = 334 cm{sup −1}); E{sub g} (λ = 148 cm{sup −1}) and T{sub 2g} (λ = 699) of the Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4}. The investigation on dielectric constant, dielectric loss tangent and ac conductivity was carried out in the frequency range 20 Hz–1 MHz at room temperature. The linear nature of the AC conductivity shows small polaron type of hopping mechanism. The saturation magnetization increases up to x = 0.4 (143 emu/cm{sup 3}), which decreases for higher x.

  16. Preparation and characterization of lithium thio-germanate thin film electrolytes grown by RF sputtering for solid state lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Seo, Inseok

    In this study, lithium thio-germanate thin amorphous films were prepared as electrolytes for lithium rechargeable batteries by RF sputtering deposition in Ar atmosphere. The targets for RF sputtering were prepared by milling the appropriate amounts of the starting materials in the nLi2S+GeS 2(n = 1, 2, and 3), Li2GeS3, Li4GeS 4 and Li6GeS5, binary system. The ~1 mum thin film electrolytes were grown onto a variety of substrates using 50 W power and 25 mtorr gas pressure. Films were sputtered in inactive Ar atmospheres. IR, Raman spectroscopy and XRD were used to characterize the chemical bonding and the local structures in the films. XPS spectroscopy was used to further characterize the composition and electronic structures of the films. Ionic conductivity measurements of the electrolyte film using impedance spectroscopy were used to examine the Li2S dependence of the conductivity. The conductivities of the thin films at 25 °C is 1.7 x 10-3 (S/cm). This ionic conductivities of the thin films are two order magnitude higher than oxide thin films (LiPON) which are commercial thin film electrolytes. Therefore, lithium thio-germanate thin film electrolytes are very promising materials for use Li-ion batteries.

  17. Characterization of nitrogen-rich silicon nitride films grown by the electron cyclotron resonance plasma technique

    NASA Astrophysics Data System (ADS)

    Wang, L.; Reehal, H. S.; Martínez, F. L.; San Andrés, E.; del Prado, A.

    2003-07-01

    Amorphous hydrogenated silicon nitride films have been deposited by the electron cyclotron resonance plasma technique, using N2 and SiH4 as precursor gases. The gas flow ratio, deposition temperature and microwave power have been varied in order to study their effect on the properties of the films, which were characterized by Rutherford back-scattering spectrometry, elastic recoil detection analysis (ERDA), Fourier transform infrared spectroscopy and ellipsometry. All samples show N/Si ratios near or above the stoichiometric value (N/Si = 1.33). The hydrogen content determined from ERDA measurements is significantly higher than the amount detected by infrared spectroscopy, evidencing the presence of non-bonded H. As the N2/SiH4 gas flow ratio is increased (by decreasing the SiH4 partial pressure), the Si content decreases and the N-H concentration increases, while the N content remains constant, resulting in an increase of the N/Si ratio. The decrease of the Si content causes a decrease of the refractive index and the density of the film, while the growth ratio also decreases due to the limiting factor of the SiH4 partial pressure. The infrared Si-N stretching band shifts to higher wavenumbers as the N-H concentration increases. The increase of deposition temperature promotes the release of H, resulting in a higher incorporation of N and Si into the film and a decrease of the N/Si ratio. The effect of increasing the microwave power is analogous to increasing the N2/SiH4 ratio, due to the increase in the proportion of nitrogen activated species.

  18. Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

    SciTech Connect

    Lo, Fang-Yuh Ting, Yi-Chieh; Chou, Kai-Chieh; Hsieh, Tsung-Chun; Ye, Cin-Wei; Hsu, Yung-Yuan; Liu, Hsiang-Lin; Chern, Ming-Yau

    2015-06-07

    Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescence spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.

  19. Characterisation of nano-crystalline titanium dioxide films grown by atmospheric pressure plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Paulmier, Thierry; Bell, John M.; Fredericks, Peter M.

    2006-01-01

    A new atmospheric pressure plasma electrolytic process has been developed for the deposition of TiO II crystalline thin films on metal substrate. Contrary to the other deposition techniques, the process occurs in a liquid precursor, composed of titanium tetraisopropoxide and absolute ethanol. A plasma discharge is created and confined around the cathode in a superheated vapour sheath surrounded by the liquid phase, inducing the production of a thin TiO II coating at the surface of the cathode. Because of the flexibility of the operating parameters, this technology allows the rapid deposition of thin films with a wide range of structural and physical properties. This process enables therefore the production of nanocrystalline titania films with adjustable morphology and structure (anatase, rutile) by adjusting the operating voltage, current intensity, the treatment time and calcination temperature. The analysis of the structure and composition of these TiO II coatings have been carried out by Scanning Electron Microscopy, Transmission Electron Microscopy, Raman spectroscopy, X-ray Photoelectron Spectroscopy and X-Ray Diffraction. A thorough study has been performed to understand the influence of the operating parameters on the properties and structure of the coatings.

  20. Multiferroic fluoride BaCoF4 Thin Films Grown Via Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Borisov, Pavel; Johnson, Trent; García-Castro, Camilo; Kc, Amit; Schrecongost, Dustin; Cen, Cheng; Romero, Aldo; Lederman, David

    Multiferroic materials exhibit exciting physics related to the simultaneous presence of multiple long-range orders, in many cases consisting of antiferromagnetic (AF) and ferroelectric (FE) orderings. In order to provide a new, promising route for fluoride-based multiferroic material engineering, we grew multiferroic fluoride BaCoF4 in thin film form on Al2O3 (0001) substrates by molecular beam epitaxy. The films grow with the orthorhombic b-axis out-of-plane and with three in-plane structural twin domains along the polar c-axis directions. The FE ordering in thin films was verified by FE remanent hysteresis loops measurements at T = 14 K and by room temperature piezoresponse force microscopy (PFM). An AF behavior was found below Neel temperature TN ~ 80 K, which is in agreement with the bulk properties. At lower temperatures two additional magnetic phase transitions at 19 K and 41 K were found. First-principles calculations demonstrated that the growth strain applied to the bulk BaCoF4 indeed favors two canted spin orders, along the b- and a-axes, respectively, in addition to the main AF spin order along the c-axis. Supported by FAME (Contract 2013-MA-2382), WV Research Challenge Grant (HEPC.dsr.12.29), and DMREF-NSF 1434897.

  1. Quantum dot FRET-based probes in thin films grown in microfluidic channels.

    PubMed

    Crivat, Georgeta; Da Silva, Sandra Maria; Reyes, Darwin R; Locascio, Laurie E; Gaitan, Michael; Rosenzweig, Nitsa; Rosenzweig, Zeev

    2010-02-10

    This paper describes the development of new fluorescence resonance energy transfer (FRET)-based quantum dot probes for proteolytic activity. The CdSe/ZnS quantum dots are incorporated into a thin polymeric film, which is prepared by layer-by-layer deposition of alternately charged polyelectrolytes. The quantum dots, which serve as fluorescent donors, are separated from rhodamine acceptor molecules, which are covalently attached to the film surface by a varying number of polyelectrolyte layers. When excited with visible light, the emission color of the polyelectrolyte multilayer film appears orange due to FRET between the quantum dots and molecular acceptors. The emission color changes to green when the rhodamine molecules are removed from the surface by enzymatic cleavage. The new probe design enables the use of quantum dots in bioassays, in this study for real-time monitoring of trypsin activity, while alleviating concerns about their potential toxicity. Application of these quantum dot FRET-based probes in microfluidic channels enables bioanalysis of volume-limited samples and single-cell studies in an in vivo-like environment. PMID:20073459

  2. Grain size dependent mechanical properties of nanocrystalline diamond films grown by hot-filament CVD

    SciTech Connect

    Wiora, M; Bruehne, K; Floeter, A; Gluche, P; Willey, T M; Kucheyev, S O; Van Buuren, A W; Hamza, A V; Biener, J; Fecht, H

    2008-08-01

    Nanocrystalline diamond (NCD) films with a thickness of {approx}6 {micro}m and with average grain sizes ranging from 60 to 9 nm were deposited on silicon wafers using a hot-filament chemical vapor deposition (HFCVD) process. These samples were then characterized with the goal to identify correlations between grain size, chemical composition and mechanical properties. The characterization reveals that our films are phase pure and exhibit a relatively smooth surface morphology. The levels of sp{sup 2}-bonded carbon and hydrogen impurities are low, and showed a systematic variation with the grain size. The hydrogen content increases with decreasing grain size, whereas the sp{sup 2} carbon content decreases with decreasing grain size. The material is weaker than single crystalline diamond, and both stiffness and hardness decrease with decreasing grain size. These trends suggest gradual changes of the nature of the grain boundaries, from graphitic in the case of the 60 nm grain size material to hydrogen terminated sp{sup 3} carbon for the 9 nm grain size material. The films exhibit low levels of internal stress and freestanding structures with a length of several centimeters could be fabricated without noticeable bending.

  3. Photovoltaic properties of Bi2FeCrO6 films epitaxially grown on (100)-oriented silicon substrates.

    PubMed

    Nechache, R; Huang, W; Li, S; Rosei, F

    2016-02-14

    We demonstrate the promising potential of using perovskite Bi2FeCrO6 (BFCO) for niche applications in photovoltaics (PV) (e.g. self-powered sensors that simultaneously exploit PV conversion and multiferroic properties) or as a complement to mature PV technologies like silicon. BFCO thin films were epitaxially grown on silicon substrates using an MgO buffer layer. Piezoresponse force microscopy measurements revealed that the tensile strained BFCO phase exhibits a polarization predominantly oriented through the in-plane direction. The semiconducting bandgap of the ordered BFCO phase combined with ferroelectric properties, opens the possibility of a ferroelectric PV efficiency above 2% in a thin film device and the use of ferroelectric materials simultaneously as solar absorber layers and carrier separators in PV devices. A large short circuit photocurrent density of 13.8 mA cm(-2) and a photovoltage output of 0.5 V are typically obtained at FF of 38% for BFCO devices fabricated on silicon. We believe that the reduced photovoltage is due to the low diffusion length of photogenerated charge carriers in the BFCO material where the ferroelectric domains are predominately oriented in-plane and thus do not contribute efficiently to the photocharge separation process. PMID:26797567

  4. Thickness-dependent transport channels in topological insulator Bi2Se3 thin films grown by magnetron sputtering

    PubMed Central

    Wang, Wen Jie; Gao, Kuang Hong; Li, Zhi Qing

    2016-01-01

    We study the low-temperature transport properties of Bi2Se3 thin films grown by magnetron sputtering. A positive magnetoresistance resulting from the weak antilocalization (WAL) effect is observed at low temperatures. The observed WAL effect is two dimensional in nature. Applying the Hikami-Larkin-Nagaoka theory, we have obtained the dephasing length. It is found that the temperature dependence of the dephasing length cannot be described only by the Nyquist electron-electron dephasing, in conflict with prevailing experimental results. From the WAL effect, we extract the number of the transport channels, which is found to increase with increasing the thickness of the films, reflecting the thickness-dependent coupling between the top and bottom surface states in topological insulator. On the other hand, the electron-electron interaction (EEI) effect is observed in temperature-dependent conductivity. From the EEI effect, we also extract the number of the transport channel, which shows similar thickness dependence with that obtained from the analysis of the WAL effect. The EEI effect, therefore, can be used to analyze the coupling effect between the top and bottom surface states in topological insulator like the WAL effect. PMID:27142578

  5. Thickness-dependent transport channels in topological insulator Bi2Se3 thin films grown by magnetron sputtering.

    PubMed

    Wang, Wen Jie; Gao, Kuang Hong; Li, Zhi Qing

    2016-01-01

    We study the low-temperature transport properties of Bi2Se3 thin films grown by magnetron sputtering. A positive magnetoresistance resulting from the weak antilocalization (WAL) effect is observed at low temperatures. The observed WAL effect is two dimensional in nature. Applying the Hikami-Larkin-Nagaoka theory, we have obtained the dephasing length. It is found that the temperature dependence of the dephasing length cannot be described only by the Nyquist electron-electron dephasing, in conflict with prevailing experimental results. From the WAL effect, we extract the number of the transport channels, which is found to increase with increasing the thickness of the films, reflecting the thickness-dependent coupling between the top and bottom surface states in topological insulator. On the other hand, the electron-electron interaction (EEI) effect is observed in temperature-dependent conductivity. From the EEI effect, we also extract the number of the transport channel, which shows similar thickness dependence with that obtained from the analysis of the WAL effect. The EEI effect, therefore, can be used to analyze the coupling effect between the top and bottom surface states in topological insulator like the WAL effect. PMID:27142578

  6. Efficient etching-free transfer of high quality, large-area CVD grown graphene onto polyvinyl alcohol films

    NASA Astrophysics Data System (ADS)

    Marta, Bogdan; Leordean, Cosmin; Istvan, Todor; Botiz, Ioan; Astilean, Simion

    2016-02-01

    Graphene transfer is a procedure of paramount importance for the production of graphene-based electronic devices. The transfer procedure can affect the electronic properties of the transferred graphene and can be detrimental for possible applications both due to procedure induced defects which can appear and due to scalability of the method. Hence, it is important to investigate new transfer methods for graphene that are less time consuming and show great promise. In the present study we propose an efficient, etching-free transfer method that consists in applying a thin polyvinyl alcohol layer on top of the CVD grown graphene on Cu and then peeling-off the graphene onto the polyvinyl alcohol film. We investigate the quality of the transferred graphene before and after the transfer, using Raman spectroscopy and imaging as well as optical and atomic force microscopy techniques. This simple transfer method is scalable and can lead to complete transfer of graphene onto flexible and transparent polymer support films without affecting the quality of the graphene during the transfer procedure.

  7. Thickness-dependent transport channels in topological insulator Bi2Se3 thin films grown by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Wen Jie; Gao, Kuang Hong; Li, Zhi Qing

    2016-05-01

    We study the low-temperature transport properties of Bi2Se3 thin films grown by magnetron sputtering. A positive magnetoresistance resulting from the weak antilocalization (WAL) effect is observed at low temperatures. The observed WAL effect is two dimensional in nature. Applying the Hikami-Larkin-Nagaoka theory, we have obtained the dephasing length. It is found that the temperature dependence of the dephasing length cannot be described only by the Nyquist electron-electron dephasing, in conflict with prevailing experimental results. From the WAL effect, we extract the number of the transport channels, which is found to increase with increasing the thickness of the films, reflecting the thickness-dependent coupling between the top and bottom surface states in topological insulator. On the other hand, the electron-electron interaction (EEI) effect is observed in temperature-dependent conductivity. From the EEI effect, we also extract the number of the transport channel, which shows similar thickness dependence with that obtained from the analysis of the WAL effect. The EEI effect, therefore, can be used to analyze the coupling effect between the top and bottom surface states in topological insulator like the WAL effect.

  8. Effect of oxygen surfactant on the magnetic and structural properties of Co films grown on Cu(110)

    SciTech Connect

    Ling, W. L.; Qiu, Z. Q.; Takeuchi, O.; Ogletree, D. F.; Salmeron, M.

    2001-01-01

    It was found that atomically flat Co(110) films could be grown on Cu(110) using O as a surfactant. To obtain detailed knowledge on the effect of O on the growth, as well as on the magnetic properties of Co overlayer, we carried out an investigation on this system using Auger electron spectroscopy, low-energy electron diffraction, surface magneto-optic Kerr effect (SMOKE), and scanning tunneling microscopy. With O as a surfactant, the initial growth of Co (<1 ML) results in a flat monolayer structure. When the Co is thicker than 1 ML, three-dimensional clusters begin to form. These clusters become ordered islands at 3 ML Co and coalesce at {approx}5 ML Co. Above 5 ML Co, layer-by-layer growth resumes. No significant Cu segregation is observed. SMOKE studies at room temperature show that the Co film is magnetic above {approx}5 ML Co, with the magnetization easy axis along the [001] direction. On the other hand, without using oxygen as a surfactant, Co grows three-dimensionally on Cu(110). The Co overlayer has its easy magnetization axis along the [001] direction, but the onset of the magnetization was observed at 11 ML Co at room temperature.

  9. Transparent conducting ITAZO anode films grown by a composite target RF magnetron sputtering at room temperature for organic solar cells

    NASA Astrophysics Data System (ADS)

    Sun, Nanhai; Fang, Guojia; Zheng, Qiao; Wang, Mingjun; Liu, Nishuang; Liu, Wei; Zhao, Xingzhong

    2009-08-01

    The preparation and characteristics of AZO co-sputtered ITO (ITAZO) electrodes grown on glass and flexible substrates using a specially designed composite target in organic solar cells are described. It was found that both the electrical and optical properties of the ITAZO films were critically dependent on the Ar/O2 flow ratio and sputtering power. In addition, all ITAZO electrodes show the amorphous structure due to the low substrate temperature. Even though the ITAZO electrode was prepared at room temperature, we can obtain the ITAZO electrode with the sheet resistance of 23 Ω/square (on a glass substrate) and 26 Ω/square (on a flexible substrate) and the average optical transmittance of 87.5% (on a glass substrate) and 86.3% (on a flexible substrate) in the region between 450 and 800 nm wavelength. In addition, the Ar ion treatment of the polyethylene terephthalate (PET) substrate could remove surface contamination and increase the adherence of the ITAZO film with the PET substrate. Furthermore, organic solar cells prepared on the ITAZO electrode under optimized conditions show the typical current density-voltage characteristics with the conversion power efficiency of 3.2%. This indicates that the composite target sputtering technique is a promising sputtering process for transparent conducting electrodes for low-cost solar cell applications.

  10. Effects of substrate conductivity on cell morphogenesis and proliferation using tailored, atomic layer deposition-grown ZnO thin films

    PubMed Central

    Choi, Won Jin; Jung, Jongjin; Lee, Sujin; Chung, Yoon Jang; Yang, Cheol-Soo; Lee, Young Kuk; Lee, You-Seop; Park, Joung Kyu; Ko, Hyuk Wan; Lee, Jeong-O

    2015-01-01

    We demonstrate that ZnO films grown by atomic layer deposition (ALD) can be employed as a substrate to explore the effects of electrical conductivity on cell adhesion, proliferation, and morphogenesis. ZnO substrates with precisely tunable electrical conductivity were fabricated on glass substrates using ALD deposition. The electrical conductivity of the film increased linearly with increasing duration of the ZnO deposition cycle (thickness), whereas other physical characteristics, such as surface energy and roughness, tended to saturate at a certain value. Differences in conductivity dramatically affected the behavior of SF295 glioblastoma cells grown on ZnO films, with high conductivity (thick) ZnO films causing growth arrest and producing SF295 cell morphologies distinct from those cultured on insulating substrates. Based on simple electrostatic calculations, we propose that cells grown on highly conductive substrates may strongly adhere to the substrate without focal-adhesion complex formation, owing to the enhanced electrostatic interaction between cells and the substrate. Thus, the inactivation of focal adhesions leads to cell proliferation arrest. Taken together, the work presented here confirms that substrates with high conductivity disturb the cell-substrate interaction, producing cascading effects on cellular morphogenesis and disrupting proliferation, and suggests that ALD-grown ZnO offers a single-variable method for uniquely tailoring conductivity. PMID:25897486

  11. Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH{sub 4}/Ar plasma

    SciTech Connect

    Sankaran, K. J.; Tai, N. H. E-mail: nhtai@mse.nthu.edu.tw; Huang, B. R.; Saravanan, A.; Lin, I. N. E-mail: nhtai@mse.nthu.edu.tw

    2014-10-28

    Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH{sub 4} and Ar under different negative bias voltages ranging from −50 to −200 V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under −200 V, the electron field emission (EFE) process can be turned on at a field as small as 4.08 V/μm, attaining a EFE current density as large as 3.19 mA/cm{sup 2} at an applied field of 8.64 V/μm. But the films grown without bias (0 V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH{sub 4}/Ar plasma due to large applied bias voltage of −200 V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

  12. Effect of growth stoichiometry on the electrical activity of screw dislocations in GaN films grown by molecular-beam epitaxy

    SciTech Connect

    Hsu, J. W. P.; Manfra, M. J.; Chu, S. N. G.; Chen, C. H.; Pfeiffer, L. N.; Molnar, R. J.

    2001-06-18

    The impact of the Ga/N ratio on the structure and electrical activity of threading dislocations in GaN films grown by molecular-beam epitaxy is reported. Electrical measurements performed on samples grown under Ga-rich conditions show three orders of magnitude higher reverse bias leakage compared with those grown under Ga-lean conditions. Transmission electron microscopy (TEM) studies reveal excess Ga at the surface termination of pure screw dislocations accompanied by a change in the screw dislocation core structure in Ga-rich films. The correlation of transport and TEM results indicates that dislocation electrical activity depends sensitively on dislocation type and growth stoichiometry. {copyright} 2001 American Institute of Physics.

  13. Photoluminescence of GaAs films grown by vacuum chemical epitaxy

    SciTech Connect

    Bernussi, A.A.; Barreto, C.L.; Carvalho, M.M.G.; Motisuke, P.

    1988-08-01

    GaAs layers grown by vacuum chemical epitaxy (VCE) are investigated by low-temperature photoluminescence. A qualitative relation between the growth parameters and the shallow-impurity-incorporation mechanism is established. It was observed that the predominant shallow acceptor is carbon, and its incorporation during the growth process decreases with the As:Ga ratio, increases with growth temperature until 750 /sup 0/C, and then it diminishes. In this work we compare the characteristics observed in the VCE system with those in conventional molecular-beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Our results show that this system contains some advantages from both the MBE and MOCVD systems. The photoluminescence spectra also show that at low As:Ga ratios the generation of As vacancies or its complexes is strongly enhanced.

  14. Real-time monitoring of structure and stress evolution of boron films grown on Si(100) by ultrahigh vacuum chemical vapor deposition

    SciTech Connect

    Nesting, D.C.; Kouvetakis, J.; Hearne, S.; Chason, E.; Tsong, I.S.

    1999-05-01

    The morphology and biaxial stress of amorphous boron films grown on silicon at 630 {degree}C have been determined {ital in situ} and in real time using energy dispersive x-ray reflectivity and multiple-beam optical stress sensor techniques. The capability to determine the morphology and stress of light-element thin films {ital in situ} and in real time provides a unique opportunity to optimize the parameters of thin film deposition under chemical vapor deposition conditions. {copyright} {ital 1999 American Vacuum Society.}

  15. Suppression of Precipitates in the La2-xSrxCuO4 Films Grown on LaSrAlO4 Substrates by Introducing Homoepitaxial Layer

    NASA Astrophysics Data System (ADS)

    Li, Bing-Sheng; Sawa, Akihito; Okamoto, Hiroshi

    2011-09-01

    We have investigated impacts of a LaSrAlO4 (LSAO) homoepitaxial layer (HL) on the quality of La2-xSrxCuO4 (LSCO) films grown on single crystal LSAO (001) substrates by pulsed laser deposition. Introduction of the LSAO HL significantly suppressed the segregation of impurity phases in the LSCO films especially in a higher Sr-doping range (x > 0.20), leading to the improvement of the surface morphology. The suppression of impurity phases also enables us to obtain the desired stoichiometry of the LSCO films, which show the superconducting dome in the x-temperature phase diagram very similar to that of bulk samples.

  16. Optical properties of hydrogenated amorphous carbon films grown from methane plasma

    NASA Technical Reports Server (NTRS)

    Pouch, J. J.; Alterovitz, S. A.; Warner, J. D.; Liu, D. C.; Lanford, W. A.

    1985-01-01

    A 30 kHz ac glow discharge formed from methane gas was used to grow carbon films on InP substrates. Both the growth rate, and the realitive Ar ion sputtering rate at 3 keV varied monotonically with deposition power. Results from the N-15 nuclear reaction profile experiments indicated a slight drop in the hydrogen concentration as more energy was dissipated in the ac discharge. Values for the index of refraction and extinction coefficient ranged from 1.721 to 1.910 and 0 to -0.188, respectively. Optical bandgaps as high as 2.34 eV were determined.

  17. Reactor design for uniform chemical vapor deposition-grown films without substrate rotation

    DOEpatents

    Wanlass, M.

    1985-02-19

    A quartz reactor vessel for growth of uniform semiconductor films includes a vertical, cylindrical reaction chamber in which a substrate-supporting pedestal provides a horizontal substrate-supporting surface spaced on its perimeter from the chamber wall. A cylindrical confinement chamber of smaller diameter is disposed coaxially above the reaction chamber and receives reaction gas injected at a tangent to the inside chamber wall, forming a helical gas stream that descends into the reaction chamber. In the reaction chamber, the edge of the substrate-supporting pedestal is a separation point for the helical flow, diverting part of the flow over the horizontal surface of the substrate in an inwardly spiraling vortex.

  18. Reactor design for uniform chemical vapor deposition-grown films without substrate rotation

    DOEpatents

    Wanlass, Mark

    1987-01-01

    A quartz reactor vessel for growth of uniform semiconductor films includes a vertical, cylindrical reaction chamber in which a substrate-supporting pedestal provides a horizontal substrate-supporting surface spaced on its perimeter from the chamber wall. A cylindrical confinement chamber of smaller diameter is disposed coaxially above the reaction chamber and receives reaction gas injected at a tangent to the inside chamber wall, forming a helical gas stream that descends into the reaction chamber. In the reaction chamber, the edge of the substrate-supporting pedestal is a separation point for the helical flow, diverting part of the flow over the horizontal surface of the substrate in an inwardly spiraling vortex.

  19. Influence of growth temperature on electrical, optical, and plasmonic properties of aluminum:zinc oxide films grown by radio frequency magnetron sputtering

    SciTech Connect

    Dondapati, Hareesh; Santiago, Kevin; Pradhan, A. K.

    2013-10-14

    We have investigated the responsible mechanism for the observation of metallic conductivity at room temperature and metal-semiconductor transition (MST) at lower temperatures for aluminum-doped zinc oxide (AZO) films. AZO films were grown on glass substrates by radio-frequency magnetron sputtering with varying substrate temperatures (T{sub s}). The films were found to be crystalline with the electrical resistivity close to 1.1 × 10{sup −3} Ω cm and transmittance more than 85% in the visible region. The saturated optical band gap of 3.76 eV was observed for the sample grown at T{sub s} of 400 °C, however, a slight decrease in the bandgap was noticed above 400 °C, which can be explained by Burstein–Moss effect. Temperature dependent resistivity measurements of these highly conducting and transparent films showed a MST at ∼110 K. The observed metal-like and metal-semiconductor transitions are explained by taking into account the Mott phase transition and localization effects due to defects. All AZO films demonstrate crossover in permittivity from positive to negative and low loss in the near-infrared region, illustrating its applications for plasmonic metamaterials, including waveguides for near infrared telecommunication region. Based on the results presented in this study, the low electrical resistivity and high optical transmittance of AZO films suggested a possibility for the application in the flexible electronic devices, such as transparent conducting oxide film on LEDs, solar cells, and touch panels.

  20. Influence of growth temperature on electrical, optical, and plasmonic properties of aluminum:zinc oxide films grown by radio frequency magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Dondapati, Hareesh; Santiago, Kevin; Pradhan, A. K.

    2013-10-01

    We have investigated the responsible mechanism for the observation of metallic conductivity at room temperature and metal-semiconductor transition (MST) at lower temperatures for aluminum-doped zinc oxide (AZO) films. AZO films were grown on glass substrates by radio-frequency magnetron sputtering with varying substrate temperatures (Ts). The films were found to be crystalline with the electrical resistivity close to 1.1 × 10-3 Ω cm and transmittance more than 85% in the visible region. The saturated optical band gap of 3.76 eV was observed for the sample grown at Ts of 400 °C, however, a slight decrease in the bandgap was noticed above 400 °C, which can be explained by Burstein-Moss effect. Temperature dependent resistivity measurements of these highly conducting and transparent films showed a MST at ˜110 K. The observed metal-like and metal-semiconductor transitions are explained by taking into account the Mott phase transition and localization effects due to defects. All AZO films demonstrate crossover in permittivity from positive to negative and low loss in the near-infrared region, illustrating its applications for plasmonic metamaterials, including waveguides for near infrared telecommunication region. Based on the results presented in this study, the low electrical resistivity and high optical transmittance of AZO films suggested a possibility for the application in the flexible electronic devices, such as transparent conducting oxide film on LEDs, solar cells, and touch panels.