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Sample records for reactively sputtered zno

  1. Vertically aligned ZnO nanorods of high crystalline and optical quality grown by dc reactive sputtering

    NASA Astrophysics Data System (ADS)

    Nandi, R.; Appani, Shravan K.; Major, S. S.

    2016-09-01

    ZnO nanorods were grown on Si and quartz substrates by direct current reactive magnetron sputtering of metallic zinc target in argon–oxygen ambient, without the use of any seed layer or catalyst. A combination of top-down and cross-sectional scanning electron microscopy studies have shown that the substrate temperature critically controls the growth behavior and morphology of ZnO films, eventually resulting in the growth of well aligned and separated ZnO nanorods at substrate temperature of ∼750 °C. High resolution x-ray diffraction studies of ZnO nanorods grown at 750 °C have shown that the nanorods are highly c-axis oriented and vertically aligned perpendicular to both Si and quartz substrates, and display small values of tilt and micro-strain, particularly in the case of Si substrate (1.26° and 4 × 10‑4, respectively). Cross-sectional transmission electron microscopy of ZnO nanorods demonstrates their single-crystalline nature and growth along [0002] direction. Room temperature photoluminescence spectra of ZnO nanorods display extremely high near-band-edge emission and weak defect emission due to point defects, compared to that of the ZnO films grown at lower substrate temperatures. The drastic enhancement of near-band-edge emission of ZnO nanorods (over two orders of magnitude) and strong suppression of defect emission are attributed to their high crystalline quality and absence of interface defects due to lateral coalescence.

  2. Vertically aligned ZnO nanorods of high crystalline and optical quality grown by dc reactive sputtering

    NASA Astrophysics Data System (ADS)

    Nandi, R.; Appani, Shravan K.; Major, S. S.

    2016-09-01

    ZnO nanorods were grown on Si and quartz substrates by direct current reactive magnetron sputtering of metallic zinc target in argon-oxygen ambient, without the use of any seed layer or catalyst. A combination of top-down and cross-sectional scanning electron microscopy studies have shown that the substrate temperature critically controls the growth behavior and morphology of ZnO films, eventually resulting in the growth of well aligned and separated ZnO nanorods at substrate temperature of ˜750 °C. High resolution x-ray diffraction studies of ZnO nanorods grown at 750 °C have shown that the nanorods are highly c-axis oriented and vertically aligned perpendicular to both Si and quartz substrates, and display small values of tilt and micro-strain, particularly in the case of Si substrate (1.26° and 4 × 10-4, respectively). Cross-sectional transmission electron microscopy of ZnO nanorods demonstrates their single-crystalline nature and growth along [0002] direction. Room temperature photoluminescence spectra of ZnO nanorods display extremely high near-band-edge emission and weak defect emission due to point defects, compared to that of the ZnO films grown at lower substrate temperatures. The drastic enhancement of near-band-edge emission of ZnO nanorods (over two orders of magnitude) and strong suppression of defect emission are attributed to their high crystalline quality and absence of interface defects due to lateral coalescence.

  3. c-axis inclined ZnO films for shear-wave transducers deposited by reactive sputtering using an additional blind

    SciTech Connect

    Link, M.; Schreiter, M.; Weber, J.; Gabl, R.; Pitzer, D.; Primig, R.; Wersing, W.; Assouar, M.B.; Elmazria, O.

    2006-03-15

    This article reports on the growth and characterization of polycrystalline ZnO films having c axis inclined up to 16 deg. with respect to the substrate normal. These films allow the excitation of shear and longitudinal waves with comparable electromechanical coupling constants and are of significant interest for thin film bulk acoustic resonators (FBARs). The films are deposited on silicon substrates covered by Al{sub 2}O{sub 3} and SiO{sub 2} buffer layers under low pressure using a modified reactive dc-pulsed magnetron sputtering system. A blind has been positioned between target and substrate, allowing oblique particle incidence without tilting the wafer. The study of structural properties of the deposited ZnO films by x-ray diffraction and scanning electron microscopy has permitted to show the presence of the inclined structure. Electromechanical coupling constants K up to 13% have been extracted for shear-mode excitation using highly overmoded FBARs.

  4. Dielectric SiO2/ZrO2 distributed Bragg reflectors for ZnO microcavities prepared by the reactive helicon-wave-excited-plasma sputtering method

    NASA Astrophysics Data System (ADS)

    Chichibu, S. F.; Ohmori, T.; Shibata, N.; Koyama, T.

    2006-04-01

    Reactive helicon-wave-excited-plasma sputtering method is shown to be a suitable technique for the fabrication of high reflectivity (R) distributed Bragg reflectors (DBRs), in particular, operating at the resonance wavelength of B excitons in ZnO (366.5nm), utilizing quarter-wavelength multilayers of SiO2 and ZrO2 dielectric films. According to the surface-damage-free nature and proper stoichiometry controllability of the method, dense dielectric films exhibiting ideal refractive indices (1.46 for SiO2 and 2.10 for ZrO2 at 633nm) and small root-mean-square values for the surface roughness (0.20nm for SiO2 and 0.53nm for ZrO2) were deposited using Si and Zr targets and O2 gas at room temperature. Optical reflectance spectra of the SiO2/ZrO2 DBRs agreed with those calculated using the optical multilayer film theory, and eight-pair DBR exhibited R higher than 99.5% at 366.5nm and 82nm stop bandwidth (R ⩾95%). The results indicate that the DBR can be used for the realization of polariton lasers using ZnO microcavities.

  5. Thermoelectric properties optimization of Al-doped ZnO thin films prepared by reactive sputtering Zn-Al alloy target

    NASA Astrophysics Data System (ADS)

    Fan, Ping; Li, Ying-zhen; Zheng, Zhuang-hao; Lin, Qing-yun; Luo, Jing-ting; Liang, Guang-xing; Zhang, Miao-qin; Chen, Min-cong

    2013-11-01

    Al-doped ZnO (AZO) has practical applications in the industry for thermoelectric generation, owing to its nontoxicity, low-cost and stability at high temperatures. In this study, AZO thin films with high quality were deposited on BK7 glass substrates at room-temperature by direct current reactive magnetron sputtering using Zn-Al alloy target. The deposited thin films were annealed at various temperatures ranging from 623 K to 823 K with a space of 50 K. It is found that the absolute value of Seebeck coefficient of AZO thin film annealed at 723 K increases stably with increasing of measuring temperature and reaches a value of ∼60 μV/K at 575 K. After that, Al-doping content was varied to further optimize the thermoelectric properties of AZO thin films. The power factor of AZO thin films with Al content of 3 wt% increased with increase of measuring temperature and the maximum power factor of 1.54 × 10-4 W m-1K-2 was obtained at 550 K with the maximum absolute values of Seebeck coefficient of 99 μV/K, which is promising for high temperature thermoelectric application.

  6. Modeling target erosion during reactive sputtering

    NASA Astrophysics Data System (ADS)

    Strijckmans, K.; Depla, D.

    2015-03-01

    The influence of the reactive sputter conditions on the racetrack and the sputter profile for an Al/O2 DC reactive sputter system is studied by modeling. The role of redeposition, i.e. the deposition of sputtered material back on the target, is therefore taken into account. The used model RSD2013 is capable of simulating the effect of redeposition on the target condition in a spatial resolved way. Comparison between including and excluding redeposition in the RSD2013 model shows that the in-depth oxidation profile of the target differs. Modeling shows that it is important to distinguish between the formed racetrack, i.e. the erosion depth profile, and the sputter profile. The latter defines the distribution of the sputtered atoms in the vacuum chamber. As the target condition defines the sputter yield, it does determine the racetrack and the sputter profile of the planar circular target. Both the shape of the racetrack and the sputter profile change as function of the redeposition fraction as well as function of the oxygen flow change. Clear asymmetries and narrowing are observed for the racetrack shape. Similar effects are noticed for the sputter profile but to a different extent. Based on this study, the often heard misconception that the racetrack shape defines the distribution of the sputtered atoms during reactive sputtering is proven to be wrong.

  7. Conductive ZnO:Zn Composites for High-Rate Sputtering Deposition of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Zhou, Li Qin; Dubey, Mukul; Simões, Raul; Fan, Qi Hua; Neto, Victor

    2015-02-01

    We report an electrically conductive composite prepared by sintering ZnO and metallic Zn powders. Microstructure analysis combined with electrical conductivity studies indicated that when the proportion of metallic Zn reached a threshold (˜20 wt.%), a metal matrix was formed in accordance with percolation theory. This composite has potential as a sputtering target for deposition of high-quality ZnO. Use of the ZnO:Zn composite completely eliminates target poisoning effects in reactive sputtering of the metal, and enables deposition of thin ZnO films at rates much higher than those obtained by sputtering of pure ZnO ceramic targets. The optical transmittance of the ZnO films prepared by use of this composite is comparable with that of films produced by radio frequency sputtering of pure ZnO ceramic targets. The sputtering characteristics of the conductive ZnO:Zn composite target are reported, and possible mechanisms of the high rate of deposition are also discussed.

  8. On reactive high power impulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Gudmundsson, J. T.

    2016-01-01

    High power impulse magnetron sputtering (HiPIMS) is an ionized physical vapor deposition (IPVD) technique that is particularly promising for reactive sputtering applications. However, there are few issues that have to be resolved before the full potential of this technique can be realized. Here we give an overview of the key experimental findings for the reactive HiPIMS discharge. An increase in the discharge current is commonly observed with increased partial pressure of the reactive gas or decreased repetition pulse frequency. There are somewhat conflicting claims regarding the hysteresis effect in the reactive HiPIMS discharge as some report reduction or elimination of the hysteresis effect while others claim a feedback control is essential. The ion energy distribution of the metal ion and the atomic ion of the reactive gas are similar and extend to very high energies while the ion energy distribution of the working gas and the molecular ion of the reactive gas are similar and are much less energetic.

  9. Reactive sputter deposition of boron nitride

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; McKernan, M.A.; Makowiecki, D.M.

    1995-10-01

    The preparation of fully dense, boron targets for use in planar magnetron sources has lead to the synthesis of Boron Nitride (BN) films by reactive rf sputtering. The deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are characterized for composition using Auger electron spectroscopy, for chemical bonding using Raman spectroscopy and for crystalline structure using transmission electron microscopy. The deposition conditions are established which lead to the growth of crystalline BN phases. In particular, the growth of an adherent cubic BN coating requires 400--500 C substrate heating and an applied {minus}300 V dc bias.

  10. Structural transformations in reactively sputtered alumina films

    SciTech Connect

    Nayar, P. Khanna, A.

    2014-04-24

    Thin films of amorphous alumina of thickness ∼350 nm were prepared on silicon wafer by DC cathode reactive sputtering. The effects of thermal annealing on the structural properties were investigated at annealing temperatures of 600°C, 800°C, 1100°C and 1220°C. X-ray diffraction showed that crystallization starts at 800°C and produces δ and θ alumina phases, the latter phase grows with heat treatment and the film was predominantly δ-phase with small amount of a-phase after annealing at 1220°C. AFM studies found that the surface of thin films smoothened upon crystallization.

  11. Effect of Oxidation Condition on Growth of N: ZnO Prepared by Oxidizing Sputtering Zn-N Film

    NASA Astrophysics Data System (ADS)

    Qin, Xuesi; Li, Guojian; Xiao, Lin; Chen, Guozhen; Wang, Kai; Wang, Qiang

    2016-06-01

    Nitrogen-doped zinc oxide (N: ZnO) films have been prepared by oxidizing reactive RF magnetron-sputtering zinc nitride (Zn-N) films. The effect of oxidation temperature and oxidation time on the growth, transmittance, and electrical properties of the film has been explored. The results show that both long oxidation time and high oxidation temperature can obtain the film with a good transmittance (over 80 % for visible and infrared light) and a high carrier concentration. The N: ZnO film exhibits a special growth model with the oxidation time and is first to form a N: ZnO particle on the surface, then to become a N: ZnO layer, and followed by the inside Zn-N segregating to the surface to oxidize N: ZnO. The surface particle oxidized more adequately than the inside. However, the X-ray photoemission spectroscopy results show that the lower N concentration results in the lower N substitution in the O lattice (No). This leads to the formation of n-type N: ZnO and the decrease of carrier concentration. Thus, this method can be used to tune the microstructure, optical transmittance, and electrical properties of the N: ZnO film.

  12. Effect of Oxidation Condition on Growth of N: ZnO Prepared by Oxidizing Sputtering Zn-N Film.

    PubMed

    Qin, Xuesi; Li, Guojian; Xiao, Lin; Chen, Guozhen; Wang, Kai; Wang, Qiang

    2016-12-01

    Nitrogen-doped zinc oxide (N: ZnO) films have been prepared by oxidizing reactive RF magnetron-sputtering zinc nitride (Zn-N) films. The effect of oxidation temperature and oxidation time on the growth, transmittance, and electrical properties of the film has been explored. The results show that both long oxidation time and high oxidation temperature can obtain the film with a good transmittance (over 80 % for visible and infrared light) and a high carrier concentration. The N: ZnO film exhibits a special growth model with the oxidation time and is first to form a N: ZnO particle on the surface, then to become a N: ZnO layer, and followed by the inside Zn-N segregating to the surface to oxidize N: ZnO. The surface particle oxidized more adequately than the inside. However, the X-ray photoemission spectroscopy results show that the lower N concentration results in the lower N substitution in the O lattice (No). This leads to the formation of n-type N: ZnO and the decrease of carrier concentration. Thus, this method can be used to tune the microstructure, optical transmittance, and electrical properties of the N: ZnO film.

  13. AFM characterization of nonwoven material functionalized by ZnO sputter coating

    SciTech Connect

    Deng Bingyao; Yan Xiong; Wei Qufu Gao Weidong

    2007-10-15

    Sputter coatings provide new approaches to the surface functionalization of textile materials. In this study, polyethylene terephthalate (PET) nonwoven material was used as a substrate for creating functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit functional zinc oxide (ZnO) nanostructures onto the nonwoven substrate. The evolution of the surface morphology of the fibers in the nonwoven web was examined using atomic force microscopy (AFM). The AFM observations revealed a significant difference in the morphology of the fibers before and after the sputter coating. The AFM images also indicated the effect of the sputtering conditions on the surface morphology of the fibers. The increase in the sputtering time led to the growth of the ZnO grains on the fiber surfaces. The higher pressure in the sputtering chamber could cause the formation of larger grains on the fiber surfaces. The higher power used also generated larger grains on the fiber surfaces.

  14. 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.

  15. Formation of dielectric silicon compounds by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Veselov, D. S.; Voronov, Yu A.

    2016-09-01

    The paper is devoted to the study of reactive magnetron sputtering of the silicon target in the ambient of inert argon gas with reactive gas, nitrogen or oxygen. The magnetron was powered by two mid-frequency generators of a rectangular pulse of opposite polarity. The negative polarity pulse provides the sputtering of the target. The positive polarity pulse provides removal of accumulated charge from the surface of the target. This method does not require any special devices of resistances matching and provides continuous sputtering of the target.

  16. Synthesis, characterization, and hydrogen gas sensing properties of AuNs-catalyzed ZnO sputtered thin films

    NASA Astrophysics Data System (ADS)

    Drmosh, Q. A.; Yamani, Z. H.

    2016-07-01

    Hydrogen present in concentration up to 4 vol.% forms an explosive mixture with air. Its propensity to escape in the event of leak, could lead to quick build-up and formation of an explosive mixture with air in confined spaces, such as an automobile. This necessitates its detection at very low concentration. Zinc oxide (ZnO) is a well-known wide band gap (∼3.37 eV) semiconducting oxide that has been widely used for gas sensing applications. This work reports on the fabrication, characterization and gas sensing performance of nanogold decorated ZnO thin films made by DC reactive sputtering. The sensor films were fabricated by depositing a very thin layer of gold on the sputtered ZnO thin film. The as deposited Au@ZnO films were converted into highly crystalline ZnO film covered with gold nanostructures (AuNs@ZnO) by mild heat treatment. The structural and morphological as well as the compositional homogeneity of the as-deposited and heat-treated ZnO, Au@ZnO and AuNs@ZnO thin films were ascertained. The gas sensing behavior of the AuNs@ZnO thin films towards hydrogen as a function of temperature at different H2 concentrations was investigated and compared with that of pure and heat-treated ZnO films. The effect of the presence of gold nanoparticles on imparting improvement (in terms of higher response signal, high reproducibility and complete reversibility) was established; the optimal operating temperature was about 400 °C. A plausible mechanism for the observed enhancement in the sensing behavior of AuNs@ZnO films towards H2 is proposed.

  17. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  18. Comparison on electrically pumped random laser actions of hydrothermal and sputtered ZnO films

    SciTech Connect

    Wang, Canxing; Jiang, Haotian; Li, Yunpeng; Ma, Xiangyang; Yang, Deren

    2013-10-07

    Random lasing (RL) in polycrystalline ZnO films is an intriguing research subject. Here, we have comparatively investigated electrically pumped RL behaviors of two metal-insulator-semiconductor structured devices using the hydrothermal and sputtered ZnO films as the semiconductor components, i.e., the light-emitting layers, respectively. It is demonstrated that the device using the hydrothermal ZnO film exhibits smaller threshold current and larger output optical power of the electrically pumped RL. The morphological characterization shows that the hydrothermal ZnO film is somewhat porous and is much rougher than the sputtered one, suggesting that in the former stronger multiple light scattering can occur. Moreover, the photoluminescence characterization indicates that there are fewer defects in the hydrothermal ZnO film than in the sputtered one, which means that the photons can pick up larger optical gain through stimulated emission in the hydrothermal ZnO film. Therefore, it is believed that the stronger multiple light scattering and larger optical gain contribute to the improved performance of the electrically pumped RL from the device using the hydrothermal ZnO film.

  19. Synthesis and annealing study of RF sputtered ZnO thin film

    NASA Astrophysics Data System (ADS)

    Singh, Shushant Kumar; Sharma, Himanshu; Singhal, R.; Kumar, V. V. Siva; Avasthi, D. K.

    2016-05-01

    In this paper, we have investigated the annealing effect on optical and structural properties of ZnO thin films, synthesized by RF magnetron sputtering. ZnO thin films were deposited on glass and silicon substrates simultaneously at a substrate temperature of 300 °C using Argon gas in sputtering chamber. Thickness of as deposited ZnO thin film was found to be ~155 nm, calculated by Rutherford backscattering spectroscopy (RBS). These films were annealed at 400 °C and 500 °C temperature in the continuous flow of oxygen gas for 1 hour in tube furnace. X-ray diffraction analysis confirmed the formation of hexagonal wurtzite structure of ZnO thin film along the c-axis (002) orientation. Transmittance of thin films was increased with increasing the annealing temperature estimated by UV-visible transmission spectroscopy. Quality and texture of the thin films were improved with annealing temperature, estimated by Raman spectroscopy.

  20. Radio-frequency magnetron sputtering and wet thermal oxidation of ZnO thin film

    NASA Astrophysics Data System (ADS)

    Liu, H. F.; Chua, S. J.; Hu, G. X.; Gong, H.; Xiang, N.

    2007-08-01

    The authors studied the growth and wet thermal oxidation (WTO) of ZnO thin films using a radio-frequency magnetron sputtering technique. X-ray diffraction reveals a preferred orientation of [101¯0]ZnO(0002)//[112¯0]Al2O3(0002) coexisted with a small amount of ZnO (101¯1) and ZnO (101¯3) crystals on the Al2O3 (0001) substrate. The ZnO (101¯1) and ZnO (101¯3) crystals, as well as the in-plane preferred orientation, are absent from the growth of ZnO on the GaAs(001) substrate. WTO at 550 °C improves the crystalline and the photoluminescence more significantly than annealing in air, N2 and O2 ambient; it also tends to convert the crystal from ZnO (101¯1) and ZnO (101¯3) to ZnO (0002). The evolution of the photoluminescence upon WTO and annealing reveals that the green and orange emissions, centered at 520 and 650 nm, are likely originated from oxygen vacancies and oxygen interstitials, respectively; while the 420 nm emission, which is very sensitive to the postgrowth thermal processing regardless of the substrate and the ambient gas, is likely originated from the surface-state related defects.

  1. Deposition of reactively ion beam sputtered silicon nitride coatings

    NASA Technical Reports Server (NTRS)

    Grill, A.

    1982-01-01

    An ion beam source was used to deposit silicon nitride films by reactively sputtering a silicon target with beams of Ar + N2 mixtures. The nitrogen fraction in the sputtering gas was 0.05 to 0.80 at a total pressure of 6 to 2 millionth torr. The ion beam current was 50 mA at 500 V. The composition of the deposited films was investigated by auger electron spectroscopy and the rate of deposition was determined by interferometry. A relatively low rate of deposition of about 2 nm. one-tenth min. was found. AES spectra of films obtained with nitrogen fractions higher than 0.50 were consistent with a silicon to nitrogen ratio corresponding to Si3N4. However the AES spectra also indicated that the sputtered silicon nitride films were contaminated with oxygen and carbon and contained significant amounts of iron, nickel, and chromium, most probably sputtered from the holder of the substrate and target.

  2. Catalytic growth of ZnO nanostructures by r.f. magnetron sputtering.

    PubMed

    Arroyo-Hernández, María; Alvaro, Raquel; Serrano, Sheila; Costa-Krämer, José Luis

    2011-01-01

    The catalytic effect of gold seed particles deposited on a substrate prior to zinc oxide (ZnO) thin film growth by magnetron sputtering was investigated. For this purpose, selected ultra thin gold layers, with thicknesses close to the percolation threshold, are deposited by thermal evaporation in ultra high vacuum (UHV) conditions and subsequently annealed to form gold nanodroplets. The ZnO structures are subsequently deposited by r.f. magnetron sputtering in a UHV chamber, and possible morphological differences between the ZnO grown on top of the substrate and on the gold are investigated. The results indicate a moderate catalytic effect for a deposited gold underlayer of 4 nm, quite close to the gold thin film percolation thickness.

  3. Sputter deposition of Al-doped ZnO films with various incident angles

    SciTech Connect

    Sato, Yasushi; Yanagisawa, Kei; Oka, Nobuto; Nakamura, Shin-ichi; Shigesato, Yuzo

    2009-09-15

    Al-doped ZnO (AZO) films were sputter deposited on glass substrates heated at 200 degree sign C under incident angles of sputtered particles at 0 degree sign (incidence normal to substrate), 20 deg., 40 deg., 60 deg., and 80 deg. In the case of normal incidence, x-ray diffraction pole figures show a strong [001] preferred orientation normal to the film surface. In contrast, in the case wherein the incident angles were higher than 60 degree sign , the [001] orientation inclined by 25 deg. - 35 deg. toward the direction of sputtered particles. Transmission electron microscopy revealed that the tilt angle of the [001] orientation increased with increasing angle of the incident sputtered particles, whereas the columnar structure did not show any sign of inclination with respect to the substrate plane.

  4. Elementary surface processes during reactive magnetron sputtering of chromium

    SciTech Connect

    Monje, Sascha; Corbella, Carles Keudell, Achim von

    2015-10-07

    The elementary surface processes occurring on chromium targets exposed to reactive plasmas have been mimicked in beam experiments by using quantified fluxes of Ar ions (400–800 eV) and oxygen atoms and molecules. For this, quartz crystal microbalances were previously coated with Cr thin films by means of high-power pulsed magnetron sputtering. The measured growth and etching rates were fitted by flux balance equations, which provided sputter yields of around 0.05 for the compound phase and a sticking coefficient of O{sub 2} of 0.38 on the bare Cr surface. Further fitted parameters were the oxygen implantation efficiency and the density of oxidation sites at the surface. The increase in site density with a factor 4 at early phases of reactive sputtering is identified as a relevant mechanism of Cr oxidation. This ion-enhanced oxygen uptake can be attributed to Cr surface roughening and knock-on implantation of oxygen atoms deeper into the target. This work, besides providing fundamental data to control oxidation state of Cr targets, shows that the extended Berg's model constitutes a robust set of rate equations suitable to describe reactive magnetron sputtering of metals.

  5. Rotating cylindrical magnetron sputtering: Simulation of the reactive process

    SciTech Connect

    Depla, D.; Mahieu, S.; Van Aeken, K.; Leroy, W. P.; Haemers, J.; De Gryse, R.; Li, X. Y.; Bogaerts, A.

    2010-06-15

    A rotating cylindrical magnetron consists of a cylindrical tube, functioning as the cathode, which rotates around a stationary magnet assembly. In stationary mode, the cylindrical magnetron behaves similar to a planar magnetron with respect to the influence of reactive gas addition to the plasma. However, the transition from metallic mode to poisoned mode and vice versa depends on the rotation speed. An existing model has been modified to simulate the influence of target rotation on the well known hysteresis behavior during reactive magnetron sputtering. The model shows that the existing poisoning mechanisms, i.e., chemisorption, direct reactive ion implantation and knock on implantation, are insufficient to describe the poisoning behavior of the rotating target. A better description of the process is only possible by including the deposition of sputtered material on the target.

  6. Reactive sputtered copper indium diselenide films for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Thornton, J. A.; Cornog, D. G.; Hall, R. B.; Shea, S. P.; Meakin, J. D.

    1984-06-01

    Single phase chalcopyrite CuInSe2 coatings have been deposited by reactive cosputtering from Cu and In planar magnetron sources operated in an Ar + H2Se working gas. Effective sputtering yields from the conditioned Cu and In targets were approximately 0.7 and 0.5 atoms/unit charge, respectively. Sputtering rate, H2Se injection rate, and H2Se and H2 partial pressure measurements were consistent with the overall reaction Cu + In + 2H2SE yields CuInSe2 + 2H2. The formation of near-stoichiometric coatings appears to be aided at elevated temperatures by a reemission mechanism which removes excess In. Photovoltaic devices formed by evaporating CdS onto the sputtered CuInSe2 yielded short circuit currents of about 33 mA/sq cm and efficiencies of about 4 percent.

  7. Near band edge emission characteristics of sputtered nano-crystalline ZnO films

    NASA Astrophysics Data System (ADS)

    Kunj, Saurabh; Sreenivas, K.

    2016-05-01

    Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O2) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

  8. Highly textured and transparent RF sputtered Eu2O3 doped ZnO films.

    PubMed

    Sreedharan, Remadevi Sreeja; Ganesan, Vedachalaiyer; Sudarsanakumar, Chellappan Pillai; Bhavsar, Kaushalkumar; Prabhu, Radhakrishna; Mahadevan Pillai, Vellara Pappukutty Pillai

    2015-01-01

    Background : Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods : Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results : XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15-22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion : Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications. PMID:25765728

  9. Highly textured and transparent RF sputtered Eu2O3 doped ZnO films

    PubMed Central

    Sreedharan, Remadevi Sreeja; Ganesan, Vedachalaiyer; Sudarsanakumar, Chellappan Pillai; Bhavsar, Kaushalkumar; Prabhu, Radhakrishna; Mahadevan Pillai, Vellara Pappukutty Pillai

    2015-01-01

    Background Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15–22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications. PMID:25765728

  10. Ion-induced oxidation of aluminum during reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Kreiter, Oliver; Grosse-Kreul, Simon; Corbella, Carles; von Keudell, Achim

    2013-04-01

    Particle beam experiments were conducted in an ultra-high-vacuum vessel to mimic target poisoning during reactive magnetron sputtering of aluminum. Aluminum targets were exposed to quantified beams of argon ions, oxygen atoms and molecules, and aluminum vapour. The growth and etch rates were measured in situ by means of an Al-coated quartz crystal microbalance. The chemical state of the target surface was monitored in-situ by real-time Fourier transform infrared spectroscopy. The surface processes were modelled through a set of balance equations providing sputter yields and sticking coefficients. The results indicate that the oxygen uptake of the aluminum surface is enhanced by a factor 1 to 2 by knock-on implantation and that the deposition of aluminum is not affected by the oxidation state of the surface.

  11. Structural and optical properties of Cu doped ZnO thin films by co-sputtering.

    PubMed

    Chung, Sung Mook; Shin, Jae-Heon; Lee, Jeong-Min; Ryu, Min Ki; Cheong, Woo-Seok; Park, Sang Hee Ko; Hwang, Chi-Sun; Cho, Kyoung Ik

    2011-01-01

    This paper reports on the structural and optical properties of ZnCuO thin films that were prepared by co-sputtering for the application of p-type-channel transparent thin-film transistors (TFTs). Pure ceramic ZnO and metal Cu targets were prepared for the co-sputtering of the ZnCuO thin films. The effects of the Cu concentration on the structural, optical, and electrical properties of the ZnCuO films were investigated after their heat treatment. It was observed from the XRD measurements that the ZnCuO films with a Cu concentration of 7% had ZnO(002), Cu2O(111), and Cu2O(200) planes. The 7% Cu-doped ZnO films also showed a band-gap energy of approximately 2.05 eV, an average transmittance of approximately 62%, and a p-type carrier density of approximately 1.33 x 10(19) cm-3 at room temperature. The bottom-gated TFTs that were fabricated with the ZnCuO thin film as a p-type channel exhibited an on-off ratio of approximately 6. These results indicate the possibility of applying ZnCuO thin films with variable band-gap energies to ZnO-based optoelectronic devices.

  12. RF Reactive Magnetron Sputter Deposition of Silicon Sub-Oxides

    NASA Astrophysics Data System (ADS)

    van Hattum, E. D.

    2007-01-01

    RF reactive magnetron plasma sputter deposition of silicon sub oxide E.D. van Hattum Department of Physics and Astronomy, Faculty of Sciences, Utrecht University The work described in the thesis has been inspired and stimulated by the use of SiOx layers in the direct inductive printing technology, where the SiOx layer is used as the charge retention layer on the drums for copying and printing devices. The thesis describes investigations of the plasma and of processes taking place on the sputter target and on the SiOx growth surface in the room temperature, RF reactive magnetron plasma sputter deposition technology. The sputtering target consists of silicon and the reactive atmosphere consists of an Ar/O2 mixture. The composition of the grown SiOx layers has been varied between x=0 and x=2 by variation of the O2 partial pressure. The characteristics of the growth process have been related to the nanostructural properties of the grown films. The deposition system enables the characterisation of the plasma (Langmuir probe, energy resolved mass spectrometer) and of the growing film (Elastic Recoil Detection (ERD), Fourier transform infrared absorption spectroscopy) and is connected to a beamline of a 6MV tandem van de Graaff accelerator. Also Rutherford Backscattering Spectrometry and X-ray Photoelectron Spectroscopy have been applied. It is shown how ERD can be used as a real-time in-situ technique. The thesis presents spatially resolved values of the ion density, electron temperature and the quasi-electrostatic potential, determined using a Langmuir probe. The plasma potential has a maximum about 2 cm from the cathode erosion area, and decreases (more than 200 V typically) towards the floating sputter cathode. The potential decreases slightly in the direction towards the grounded growth surface and the positive, mainly Ar+, ions created in the large volume of the plasma closest to the substrate are accelerated towards the growth surface. These ions obtain a few eV of

  13. Role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films

    SciTech Connect

    Jie, Jin; Morita, Aya; Shirai, Hajime

    2010-08-15

    The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied by alternating the deposition of a several-nanometer-thick ZnO layer and the O{sub 2}/Ar mixture plasma exposure, i.e., layer-by-layer technique. The film crystallization promoted with suppressing the oxygen vacancy and interstitial defects by adjusting the exposure condition of O{sub 2}/Ar plasma. These findings suggest that the chemical potential of oxygen atom determine the film crystallization as well as the electronic state. The diffusion and effusion of oxygen atoms at the growing surface play a role of thermal annealing, promoted the film crystallization as well as the creation and the annihilation of oxygen and zinc related defects. The role of oxygen atoms reaching at the film-growing surface is discussed in term of chemical annealing. The possible oxygen diffusion mechanism is proposed.

  14. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    NASA Astrophysics Data System (ADS)

    Ahumada-Lazo, R.; Torres-Martínez, L. M.; Ruíz-Gómez, M. A.; Vega-Becerra, O. E.; Figueroa-Torres, M. Z.

    2014-12-01

    The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-visible spectroscopy (UV-Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

  15. Resistive switching behavior of RF magnetron sputtered ZnO thin films

    SciTech Connect

    Rajalakshmi, R.; Angappane, S.

    2015-06-24

    The resistive switching characteristics of RF magnetron sputtered zinc oxide thin films have been studied. The x-ray diffraction studies confirm the formation of crystalline ZnO on Pt/TiO{sub 2}/SiO{sub x}/Si substrate. We have fabricated Cu/ZnO/Pt device using a shadow masking technique for resistive switching study. Our Cu/ZnO/Pt device exhibits a unipolar resistive switching behaviour. The switching observed in our device could be related to oxygen vacancies or Cu ions that generate the conducting filaments responsible for resistive switching. We found HRS to LRS resistance ratio of as high as ∼200 for our Cu/ZnO/Pt device. The higher resistance ratio and stability of Cu/ZnO/Pt device would make our RF magnetron sputtered zinc oxide thin films suitable for non volatile memory applications.

  16. Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

    NASA Astrophysics Data System (ADS)

    Niang, K. M.; Cho, J.; Heffernan, S.; Milne, W. I.; Flewitt, A. J.

    2016-08-01

    The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ˜90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 108, a sub-threshold slope of 0.55 V dec-1, and a field effect mobility of 15 cm2 V-1 s-1, which is a sharp increase from 0.8 cm2 V-1 s-1 obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm2 V-1 s-1, but the sub-threshold slope is slightly deteriorated to 0.65 V dec-1. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn2SnO4 and ZnSnO3 phases.

  17. Progress in amorphous silicon solar cells produced by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Moustakas, T. D.

    The photovoltaic properties of reactively sputtered amorphous silicon are reviewed and it is shown that efficient PIN solar cells can be fabricated by the method of sputtering. The photovoltaic properties of the intrinsic films correlate with their structural and compositional inhomogeneities. Hydrogen incorporation and small levels of phosphorus and boron impurities also affect the photovoltaic properties through reduction of residual dangling bond related defects and modification of their occupation. The optical and transport properties of the doped P and N-films were found to depend sensitively on the amount of hydrogen and boron or phosphorus incorporation into the films as well as on their degree of crystallinity. Combination of the best intrinsic and doped films leads to PIN solar cell structures generating J(sc) of 13 mA/sq cm and V(oc) of between 0.85 to 0.95 volts. The efficiency of these devices, 5 to 6 percent, is limited by the low FF, typically about 50 percent. As a further test to the potential of this technology efficient tandem solar cell structures were fabricated, and device design concepts, such as the incorporation of optically reflective back contacts were tested.

  18. Fabrication and characterization of pristine and annealed Ga doped ZnO thin films using sputtering

    NASA Astrophysics Data System (ADS)

    Mishra, Abhisek; Mohapatra, Saswat; Gouda, Himanshu Sekhar; Singh, Udai P.

    2016-05-01

    ZnO is a wide-band gap, transparent, polar semiconductor with unparalleled optoelectronic, piezoelectric, thermal and transport properties, which make it the material of choice for a wide range of applications such as blue/UV optoelectronics, energy conversion, transparent electronics, spintronic, plasmonic and sensor devices. We report, three sets of Ga doped Zinc Oxide (GZO) were fabricated in different sputtering power (100 watt, 200 watt and 300 watt). Thereafter films were annealed in nitrogen ambient for 30 minutes at 400° C. From the optical absorption spectroscopy it was found that pristine films are showing a 75% transmittance in the visible region of light and it increases after the annealing. However, for 300 W grown sample opposite trend has been achieved for the post annealed sample. X-ray diffraction pattern of all the pristine and annealed films showed a preferable growth orientation at (002) phase. Some other weak peaks were also appeared in different angle which indicates that films are polycrystalline in nature. XRD data also reveals that crystallite size increases with sputtering power up to 200 W and thereafter it decreases with the deposition power. It also noted that the crystallite size of the annealed film increases with compare to the non annealed films. At room temperature an enhancement in electrical properties of Ga doped ZnO thin films was noted for the annealed ZnO films except for the film deposited at 300 watt. More significantly, it was found that annealed thin films showed the resistivity in the range of 10-3 ˜ 10-4 ohm-cm. Such a high optical transmittance and conducting zinc-oxide thin film can be used as a window layer in solar cell.

  19. Characteristics of Sputtered ZnO Thin Films for an Inverted Organic Solar Cell.

    PubMed

    Park, Yong Seob; Park, Chul Min; Lee, Jaehyeong

    2016-05-01

    Several research groups have claimed high energy conversion efficiency in organic solar cells. However, it still has low efficiency and is unstable, because organic materials are easily oxidized by atmospheric humidity and UV light. In this work, ZnO thin film as the blocking layer attributed to the interference of the injection of the hole from the P3HT and no charge carrier recombination. We obtained the maximum power conversion efficiency of 1.9% under AM 1.5 G spectral illumination of 100 MWcm(-2), when we used a ZnO film of 60 nm and the optimized P3HT:PCBM, and Au as the back electrode to solve the reaction problem of Al electrode and to control the work function between the HOMO level of P3HT and the energy level of the metal electrode. Power conversion efficiency of inverted organic solar cell (IOSC) is significantly dependent on the thickness of the ZnO thin film deposited by unbalanced magnetron sputtering method. Also, the stability of IOSC is measured under ambient conditions. PMID:27483875

  20. Sputtering temperature dependent growth kinetics and CO2 sensing properties of ZnO deposited over porous silicon

    NASA Astrophysics Data System (ADS)

    Martínez, L.; Holguín-Momaca, J. T.; Karthik, T. V. K.; Olive-Méndez, S. F.; Campos-Alvarez, J.; Agarwal, V.

    2016-10-01

    We report the growth kinetics and sensing properties of ZnO deposited over macro-porous silicon substrates at 400 and 600 °C using magnetron-sputtering technique. Scanning electron microscopy was employed to investigate the morphology and the particle size of the ZnO nanoparticles (NPs). The grain growth kinetics was analyzed with the help of the phenomenological equation rn =k0 texp(- Q / RT) finding an activation energy Q = 13.92 kJ/mol. The grain growth exponent (n = 2.85) for the growth at 400 °C corresponds to an Ostwald ripening process, while the growth at 600 °C is described by n = 1.66 implying a higher growth rate attributed to a high surface diffusion of add-atoms contributing to the formation of larger grains. The sensing response of the complete structure has been tested at different temperatures. The highest sensitivity, S ∼10, was obtained at a sensor temperature of 300 °C on the ZnO NPs sputtered on to the porous silicon substrate at 400 °C. The high response is attributed to the infiltration, uniform and homogenous distribution of the ZnO NPs into the pores. ZnO NPs sputtered at 400 °C are found to be smaller than those grown at 600 °C, exhibiting a larger surface-area/volume ratio and hence increasing the oxygen adsorption resulting in an enhanced CO2 sensitivity.

  1. Comparison of ZnO thin films grown on a polycrystalline 3C-SiC buffer layer by RF magnetron sputtering and a sol-gel method

    NASA Astrophysics Data System (ADS)

    Phan, Duy-Thach; Chung, Gwiy-Sang

    2011-02-01

    Zinc oxide (ZnO) thin films were deposited on a polycrystalline (poly) 3C-SiC buffer layer using RF magnetron sputtering and a sol-gel method. The post-deposition annealing was performed on ZnO thin films prepared using both methods. The formation of ZnO piezoelectric thin films with less residual stress was due to a close lattice mismatch of the ZnO and SiC layers as obtained by the sputtering method. Nanocrystalline, porous ZnO film prepared using the sol-gel method showed strong ultraviolet UV emission at a wavelength of 380 nm. The 3C-SiC buffer layer improved the optical and piezoelectric properties of the ZnO film produced by the two deposition methods. Moreover, the different structures of the ZnO films on the 3C-SiC intermediate layer caused by the different deposition techniques were also considered and discussed.

  2. Surface Texture and Structure of ZnO Films Synthesized by Off-Axis Sputtering Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, Sandor L.; George, M. A.; Lowndes, D. H.

    1999-01-01

    Morphology and structure of ZnO films deposited on (0001) sapphire and glass substrates by off-axis sputtering are investigated at various temperatures and pressures. All films show highly textured structures on glass substrates and epitaxial growth on sapphire substrates. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5 degrees. In textured films, it rises to several degrees. The trend of surface textures in films grown at low pressures is similar to those grown at high temperatures. A morphology transition from large well-defined hexagonal grains to flat surface was observed at a pressure of 50 mtorr and temperature of 550 C. The experiment results are explained by the transport behavior of depositing species.

  3. Strong free-carrier electro-optic response of sputtered ZnO films

    SciTech Connect

    Dominici, Lorenzo; Michelotti, Francesco; Auf der Maur, Matthias

    2012-09-01

    We report on the anisotropic electro-optic response of sputtered ZnO films and its dispersion towards both the frequency of the modulating voltage and the wavelength of the probing beam. The observed dispersion put in evidence two mechanisms. A fast and weak electrorefraction response, due to the nonlinear polarization of bound electrons, and a strong and slow carrier refraction term, ascribed to the modulation of free carriers. The former corresponds to an electro-optical coefficient of approximately -0.5 pm/V, while the latter may reach a magnitude up to 20 times stronger. This term relaxes at about 12 kHz and is largely wavelength dependent, due to a combination of effects. Also bias voltages lead to its quenching, likely extending the depletion regions at grain boundaries.

  4. Surface texture and structure of ZnO films synthesized by off-axis sputtering deposition

    SciTech Connect

    Zhu, Shen; Lowndes, D. H.

    2000-05-01

    Morphology and structure of ZnO films deposited on (0001) sapphire and glass substrates by off-axis sputtering were investigated at various temperatures and pressures. All films show highly textured structures on glass substrates and epitaxial growth on sapphire substrates. The full width at half-maximum of theta rocking curves for epitaxial films is less than 0.5 degree sign . In textured films, it rises to several degrees. The trend of surface textures in films grown at low pressures is similar to those grown at high temperatures. A morphology transition from large well-defined hexagonal grains to flat surface was observed at a pressure of 50 mtorr and temperature of 550 degree sign C. The experiment results are explained by the transport behavior of depositing species. (c) 2000 Materials Research Society.

  5. Electrical and optical properties of molybdenum doped zinc oxide films prepared by reactive RF magnetron sputtering

    SciTech Connect

    Reddy, R. Subba; Sreedhar, A.; Uthanna, S.

    2015-08-28

    Molybdenum doped zinc oxide (MZO) films were deposited on to glass substrates held at temperatures in the range from 303 to 673 K by reactive RF magnetron sputtering method. The chemical composition, crystallographic structure and surface morphology, electrical and optical properties of the films were determined. The films contained the molybdenum of 2.7 at. % in ZnO. The films deposited at 303 K were of X-ray amorphous. The films formed at 473 K were of nanocrystalline in nature with wurtzite structure. The crystallite size of the films was increased with the increase of substrate temperature. The optical transmittance of the films was in the visible range was 80–85%. The molybdenum (2.7 at %) doped zinc oxide films deposited at substrate temperature of 573 K were of nanocrystalline with electrical resistivity of 7.2×10{sup −3} Ωcm, optical transmittance of 85 %, optical band gap of 3.35 eV and figure of merit 30.6 Ω{sup −1}cm{sup −1}.

  6. Effects of annealing pressure and Ar+ sputtering cleaning on Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Wang, Jiwei; Mei, Yong; Lu, Xuemei; Fan, Xiaoxing; Kang, Dawei; Xu, Panfeng; Tan, Tianya

    2016-11-01

    Post-treatments of Al-doped ZnO films fabricated by sol-gel method were studied in condition of annealing in air, vacuum and protective ambient, as well as the follow-up Ar+ sputtering cleaning. The effect of annealing pressure on resistivity of AZO films was investigated from 105 to 10-4 Pa, where the resistivity decreased four orders of magnitude as the pressure decreased and approached to its minimum at 10 Pa. It was observed that the main decreasing of resistivity occurred in a very narrow range of middle vacuum (between 100 and 10 Pa) and high vacuum was dispensable. The XRD and XPS characterizations demonstrated that the radical increasing of oxygen vacancy, Zn interstitial and substitution of Al3+ for Zn2+ under middle vacuum were responsible for the significant enhancement of conductivity. The follow-up Ar+ sputtering cleaning can further decrease the resistivity through removing the chemisorbed oxygen on film surface and grain boundaries, meanwhile fulfil the surface texture process, and thus improve both electrical and optical performances for applications.

  7. High rate reactive sputtering of MoN(x) coatings

    NASA Technical Reports Server (NTRS)

    Rudnik, Paul J.; Graham, Michael E.; Sproul, William D.

    1991-01-01

    High rate reactive sputtering of MoN(x) films was performed using feedback control of the nitorgen partial pressure. Coatings were made at four different target powers: 2.5, 5.0, 7.5 and 10 kW. No hysteresis was observed in the nitrogen partial pressure vs. flow plot, as is typically seen for the Ti-N system. Four phases were determined by X-ray diffraction: molybdenum, Mo-N solid solution, Beta-Mo2N and gamma-Mo2N. The hardness of the coatings depended upon composition, substrate bias, and target power. The phases present in the hardest films differed depending upon deposition parameters. For example, the Beta-Mo2N phase was hardest (load 25 gf) at 5.0 kW with a value of 3200 kgf/sq mm, whereas the hardest coatings at 10 kW were the gamma-Mo2N phase (3000 kgf/sq mm). The deposition rate generally decreased with increasing nitrogen partial pressure, but there was a range of partial pressures where the rate was relatively constant. At a target power of 5.0 kW, for example, the deposition rates were 3300 A/min for a N2 partial pressure of 0.05 - 1.0 mTorr.

  8. Evidence of Negative Capacitance in Piezoelectric ZnO Thin Films Sputtered on Interdigital Electrodes.

    PubMed

    Laurenti, Marco; Verna, Alessio; Chiolerio, Alessandro

    2015-11-11

    The scaling paradigm known as Moore's Law, with the shrinking of transistors and their doubling on a chip every two years, is going to reach a painful end. Another less-known paradigm, the so-called Koomey's Law, stating that the computing efficiency doubles every 1.57 years, poses other important challenges, since the efficiency of rechargeable energy sources is substantially constant, and any other evolution is based on device architecture only. How can we still increase the computational power/reduce the power consumption of our electronic environments? A first answer to this question comes from the quest for new functionalities. Within this aim, negative capacitance (NC) is becoming one of the most intriguing and studied phenomena since it can be exploited for reducing the aforementioned limiting effects in the downscaling of electronic devices. Here we report the evidence of negative capacitance in 80 nm thick ZnO thin films sputtered on Au interdigital electrodes (IDEs). Highly (002)-oriented ZnO thin films, with a fine-grained surface nanostructure and the desired chemical composition, are deposited at room temperature on different IDEs structures. Direct-current electrical measurements highlighted the semiconducting nature of ZnO (current density in the order of 1 × 10(-3) A/cm(2)). When turned into the alternating current regime (from 20 Hz to 2 MHz) the presence of NC values is observed in the low-frequency range (20-120 Hz). The loss of metal/semiconductor interface charge states under forward bias conditions, together with the presence of oxygen vacancies and piezoelectric/electrostriction effects, is believed to be at the basis of the observed negative behavior, suggesting that ZnO thin-film-based field-effect transistors can be a powerful instrument to go beyond the Boltzmann limit and the downscaling of integrated circuit elements required for the fabrication of portable and miniaturized electronic devices, especially for electric household

  9. All-sputtered 14% CdS/CdTe thin-film solar cell with ZnO :Al transparent conducting oxide

    NASA Astrophysics Data System (ADS)

    Gupta, Akhlesh; Compaan, Alvin D.

    2004-07-01

    Radio-frequency (rf)-sputtered Al-doped ZnO was used as the transparent front contact in the fabrication of high efficiency superstrate configuration CdS /CdTe thin-film solar cells. These cells had CdS and CdTe layers also deposited by rf sputtering at 250°C with the highest processing temperature of 387°C reached during a post-deposition treatment. The devices were tested at National Renewable Energy Laboratory and yielded an efficiency of 14.0%, which is excellent for a CdTe cell using ZnO and also for any sputtered CdTe solar cell. The low-temperature deposition process using sputtering for all semiconductor layers facilitates the use of ZnO and conveys significant advantages for the fabrication of more complex multiple layers needed for the fabrication of tandem polycrystalline solar cells and for cells on polymer materials.

  10. Reactive sputtering of titanium in Ar/CH4 gas mixture: Target poisoning and film characteristics

    SciTech Connect

    Fouad, O.A.; Rumaiz, A.; Shah, S.

    2009-03-01

    Reactive sputtering of titanium target in the presence of Ar/CH{sub 4} gas mixture has been investigated. With the addition of methane gas to above 1.5% of the process gas a transition from the metallic sputtering mode to the poison mode was observed as indicated by the change in cathode current. As the methane gas flow concentration increased up to 10%, the target was gradually poisoned. The hysteresis in the cathode current could be plotted by first increasing and then subsequently decreasing the methane concentration. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of carbide phases and the transition of the process from the metallic to compound sputtering mode as the methane concentration in the sputtering gas is increased. The paper discusses a sputtering model that gives a rational explanation of the target poisoning phenomenon and shows an agreement between the experimental observations and calculated results.

  11. Mechanical and transparent conductive properties of ZnO and Ga-doped ZnO films sputtered using electron-cyclotron-resonance plasma on polyethylene naphtalate substrates

    SciTech Connect

    Akazawa, Housei

    2014-03-15

    Transparent conductive ZnO and Ga-doped ZnO (GZO) films were deposited on polyethylene naphtalate (PEN) sheet substrates using electron cyclotron resonance plasma sputtering. Both ZnO and GZO films were highly adhesive to the PEN substrates without inserting an intermediate layer in the interface. When compared at the same thickness, the transparent conductive properties of GZO films on PEN substrates were only slightly inferior to those on glass substrates. However, the carrier concentration of ZnO films on PEN substrates was 1.5 times that of those on glass substrates, whereas their Hall mobility was only 60% at a thickness of 300 nm. The depth profile of elements measured by secondary ion mass spectroscopy revealed the diffusion of hydrocarbons out of the PEN substrate into the ZnO film. Hence, doped carbons may act as donors to enhance carrier concentration, and the intermixing of elements at the interface may deteriorate the crystallinity, resulting in the lower Hall mobility. When the ZnO films were thicker than 400 nm, cracks became prevalent because of the lattice mismatch strain between the film and the substrate, whereas GZO films were free of cracks. The authors investigated how rolling the films around a cylindrical pipe surface affected their conductive properties. Degraded conductivity occurred at a threshold pipe radius of 10 mm when tensile stress was applied to the film, but it occurred at a pipe radius of 5 mm when compressive stress was applied. These values are guidelines for bending actual devices fabricated on PEN substrates.

  12. Properties of Cu-doped ZnO films by RF sputtering method: Thickness dependence

    SciTech Connect

    Sung, Nark-Eon; Lee, Ik-Jae; Thakur, Anup; Chae, Keun Hwa; Shin, Hyun-Joon; Lee, Han-Koo

    2012-10-15

    We present results concerning the thickness dependence of structural, morphological and optical properties of the Zn{sub 0.98}Cu{sub 0.02}O films deposited on glass substrates using radio frequency (RF) sputtering method. The microstructure and the chemical state of oxygen, copper and zinc in ZnO and Zn{sub 0.98}Cu{sub 0.02}O films were investigated by X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The results indicate that Zn{sub 0.98}Cu{sub 0.02}O films are the wurtzite structure with strong c-axis orientation. Crystallinity of the films is closely related to the film thickness. With increasing film thickness, there are more surface (mainly nanopores) defects existing in the Zn{sub 0.98}Cu{sub 0.02}O films and surface roughness increases. XRD and XPS data show that the valence state of copper in the Zn{sub 0.98}Cu{sub 0.02}O films is Cu{sup 2+}. The transparency of all films is more than 85% in the visible region.

  13. Spectral Behavior of Bias-Dependent Photocurrent and Photoluminescence in Sputtered ZnO Layers

    NASA Astrophysics Data System (ADS)

    Hong, K. J.; Jeong, T. S.; Kim, T. S.; Choi, C. J.; Youn, C. J.

    2016-08-01

    The bias-dependent behavior of the photocurrent (PC) and photoluminescence (PL) of sputtered ZnO layers has been investigated. Based on PC spectroscopy results, the PC intensity of the observed free exciton increased strongly up to electric field of 60 V/cm, after which its rate of increase slightly reduced due to disturbance of field-assisted dissociation of radical ion pairs, which leads to photocarrier generation. Thus, the energy of excitonic PC peaks showed a tendency to red-shift with increasing electric field, being attributed to the induced Stark effect. Therefore, it is concluded that the strong interaction between free excitons and photogenerated PC carriers leads to displacement or widening of the spectrum. In the PL measurements, near-band-edge (NBE) and violet emissions were observed. With increasing electric field, two PL emissions were progressively quenched. The combined PL/PC results reveal that the PL ions associated with the NBE and violet emissions readily interact with the PC carriers of photogenerated electrons and holes. This behavior reduces the recombination ratio and the lifetime of PL ions. So, the PL intensity quenching originates from a decrease in the number of carriers participating in recombination. Consequently, we find that the quenching mechanism of the NBE and violet emissions is strongly related to low external electric field.

  14. Using the Multipole Resonance Probe to Stabilize the Electron Density During a Reactive Sputter Process

    NASA Astrophysics Data System (ADS)

    Oberberg, Moritz; Styrnoll, Tim; Ries, Stefan; Bienholz, Stefan; Awakowicz, Peter

    2015-09-01

    Reactive sputter processes are used for the deposition of hard, wear-resistant and non-corrosive ceramic layers such as aluminum oxide (Al2O3) . A well known problem is target poisoning at high reactive gas flows, which results from the reaction of the reactive gas with the metal target. Consequently, the sputter rate decreases and secondary electron emission increases. Both parameters show a non-linear hysteresis behavior as a function of the reactive gas flow and this leads to process instabilities. This work presents a new control method of Al2O3 deposition in a multiple frequency CCP (MFCCP) based on plasma parameters. Until today, process controls use parameters such as spectral line intensities of sputtered metal as an indicator for the sputter rate. A coupling between plasma and substrate is not considered. The control system in this work uses a new plasma diagnostic method: The multipole resonance probe (MRP) measures plasma parameters such as electron density by analyzing a typical resonance frequency of the system response. This concept combines target processes and plasma effects and directly controls the sputter source instead of the resulting target parameters.

  15. Particle beam experiments for the analysis of reactive sputtering processes in metals and polymer surfaces

    SciTech Connect

    Corbella, Carles; Grosse-Kreul, Simon; Kreiter, Oliver; Arcos, Teresa de los; Benedikt, Jan; Keudell, Achim von

    2013-10-15

    A beam experiment is presented to study heterogeneous reactions relevant to plasma-surface interactions in reactive sputtering applications. Atom and ion sources are focused onto the sample to expose it to quantified beams of oxygen, nitrogen, hydrogen, noble gas ions, and metal vapor. The heterogeneous surface processes are monitored in situ by means of a quartz crystal microbalance and Fourier transform infrared spectroscopy. Two examples illustrate the capabilities of the particle beam setup: oxidation and nitriding of aluminum as a model of target poisoning during reactive magnetron sputtering, and plasma pre-treatment of polymers (PET, PP)

  16. Particle beam experiments for the analysis of reactive sputtering processes in metals and polymer surfaces

    NASA Astrophysics Data System (ADS)

    Corbella, Carles; Grosse-Kreul, Simon; Kreiter, Oliver; de los Arcos, Teresa; Benedikt, Jan; von Keudell, Achim

    2013-10-01

    A beam experiment is presented to study heterogeneous reactions relevant to plasma-surface interactions in reactive sputtering applications. Atom and ion sources are focused onto the sample to expose it to quantified beams of oxygen, nitrogen, hydrogen, noble gas ions, and metal vapor. The heterogeneous surface processes are monitored in situ by means of a quartz crystal microbalance and Fourier transform infrared spectroscopy. Two examples illustrate the capabilities of the particle beam setup: oxidation and nitriding of aluminum as a model of target poisoning during reactive magnetron sputtering, and plasma pre-treatment of polymers (PET, PP).

  17. Physical and Optical Properties of SnO2/ZnO Film Prepared by an RF Magnetron Sputtering Method.

    PubMed

    Park, Jooyoung; Lee, Ikjae; Kim, Jaeyong

    2016-03-01

    Al-, Ga-, and In-doped ZnO thin films are widely used in many technical applications, such as in solar cells and on transparent conducting oxides having high optical transmission and low resistivity values. We prepared SnO2-doped ZnO thin films on quartz substrates by using an RF magnetron sputtering method at a substrate temperature of 350 degrees C. The ratio of SnO2 to ZnO was varied from 0 to 5:5 to investigate the effects of Sn on structure and physical properties of ZnO film. The samples were synthesized at a base pressure of 1.3 x 10(-4) Pa with a working pressure of 1.3 Pa and an RF power of 40 W under Ar atmosphere. The results of X-ray diffraction data revealed that pure ZnO films exhibit a strong (002) orientation and a polycrystalline wurzite hexagonal structure. However, as increasing the SnO2 concentration, ZnO transforms to an amorphous phase. The results of the Hall-effect-measurement system revealed that the resistivity values of the films increased as increasing the doping level of SnO2. The AFM data of morphology and microstructure showed that the grain size decreased with increasing SnO2 contents while the total area of grain the boundary increased. The average value of the transmittance of the films in the visible light range was 80-95% and was shifted toward to the shorter wavelengths of the absorption edges with increasing SnO2 contents.

  18. Effects of substrate on the structure and orientation of ZnO thin film grown by rf-magnetron sputtering

    SciTech Connect

    Liu, H. F.; Chua, S. J.; Hu, G. X.; Gong, H.; Xiang, N.

    2007-10-15

    X-ray diffractions, Nomarski microscopy, scanning electron microscopy, and photoluminescence have been used to study the effects of substrate on the structure and orientation of ZnO thin films grown by rf-magnetron sputtering. GaAs(001), GaAs(111), Al{sub 2}O{sub 3}(0002) (c-plane), and Al{sub 2}O{sub 3}(1102) (r-plane) wafers have been selected as substrates in this study. X-ray diffractions reveal that the ZnO film grown on GaAs(001) substrate is purely textured with a high c-axis orientation while that grown on GaAs(111) substrate is a single ZnO(0002) crystal; a polycrystalline structure with a large-single-crystal area of ZnO(0002) is obtained on a c-plane Al{sub 2}O{sub 3} substrate while a ZnO(1120) single crystal is formed on an r-plane Al{sub 2}O{sub 3} substrate. There is absence of significant difference between the photoluminescence spectra collected from ZnO/GaAs(001), ZnO/GaAs(111), and ZnO/Al{sub 2}O{sub 3}(0002), while the photoluminescence from ZnO/Al{sub 2}O{sub 3}(1102) shows a reduced intensity together with an increased linewidth, which is, likely, due to the increased incorporation of native defects during the growth of ZnO(1120)

  19. Physical and Optical Properties of SnO2/ZnO Film Prepared by an RF Magnetron Sputtering Method.

    PubMed

    Park, Jooyoung; Lee, Ikjae; Kim, Jaeyong

    2016-03-01

    Al-, Ga-, and In-doped ZnO thin films are widely used in many technical applications, such as in solar cells and on transparent conducting oxides having high optical transmission and low resistivity values. We prepared SnO2-doped ZnO thin films on quartz substrates by using an RF magnetron sputtering method at a substrate temperature of 350 degrees C. The ratio of SnO2 to ZnO was varied from 0 to 5:5 to investigate the effects of Sn on structure and physical properties of ZnO film. The samples were synthesized at a base pressure of 1.3 x 10(-4) Pa with a working pressure of 1.3 Pa and an RF power of 40 W under Ar atmosphere. The results of X-ray diffraction data revealed that pure ZnO films exhibit a strong (002) orientation and a polycrystalline wurzite hexagonal structure. However, as increasing the SnO2 concentration, ZnO transforms to an amorphous phase. The results of the Hall-effect-measurement system revealed that the resistivity values of the films increased as increasing the doping level of SnO2. The AFM data of morphology and microstructure showed that the grain size decreased with increasing SnO2 contents while the total area of grain the boundary increased. The average value of the transmittance of the films in the visible light range was 80-95% and was shifted toward to the shorter wavelengths of the absorption edges with increasing SnO2 contents. PMID:27455746

  20. Oxygen vacancy mediated enhanced photo-absorption from ZnO(0001) nanostructures fabricated by atom beam sputtering

    NASA Astrophysics Data System (ADS)

    Solanki, Vanaraj; Joshi, Shalik R.; Mishra, Indrani; Kabiraj, D.; Mishra, N. C.; Avasthi, D. K.; Varma, Shikha

    2016-08-01

    The nanoscale patterns created on the ZnO(0001) surfaces during atom beam irradiation have been investigated here for their photo absorption response. Preferential sputtering, during irradiation, promotes Zn-rich zones that serve as the nucleation centers for the spontaneous creation of nanostructures. Nanostructured surfaces with bigger (78 nm) nanodots, displaying hexagonal ordering and long ranged periodic behavior, show higher photo absorption and a ˜0.09 eV reduced bandgap. These nanostructures also demonstrate higher concentration of oxygen vacancies which are crucial for these results. The enhanced photo-response, as observed here, has been achieved in the absence of any dopant elements.

  1. Effect of sputtering pressure on crystalline quality and residual stress of AlN films deposited at 823 K on nitrided sapphire substrates by pulsed DC reactive sputtering

    NASA Astrophysics Data System (ADS)

    Ohtsuka, Makoto; Takeuchi, Hiroto; Fukuyama, Hiroyuki

    2016-05-01

    Aluminum nitride (AlN) is a promising material for use in applications such as deep-ultraviolet light-emitting diodes (UV-LEDs) and surface acoustic wave (SAW) devices. In the present study, the effect of sputtering pressure on the surface morphology, crystalline quality, and residual stress of AlN films deposited at 823 K on nitrided a-plane sapphire substrates, which have high-crystalline-quality c-plane AlN thin layers, by pulsed DC reactive sputtering was investigated. The c-axis-oriented AlN films were homoepitaxially grown on nitrided sapphire substrates at sputtering pressures of 0.4–1.5 Pa. Surface damage of the AlN sputtered films increased with increasing sputtering pressure because of arcing (abnormal electrical discharge) during sputtering. The sputtering pressure affected the crystalline quality and residual stress of AlN sputtered films because of a change in the number and energy of Ar+ ions and Al sputtered atoms. The crystalline quality of AlN films was improved by deposition with lower sputtering pressure.

  2. Sorption Properties Of RF Reactive Sputtered TiOx Thin Films

    SciTech Connect

    Boiadjiev, S. I.; Rassovska, M. M.; Lazarova, V. B.

    2007-04-23

    The present research is focused on the sensing behavior of sputtered titanium oxide (TiOx) thin films. In order to deposit TiOx thin films the method of RF reactive sputtering of titanium target in the presence of oxygen as reactive gas is used. RF sputtering technology for thin film deposition has been elaborated on and the technological conditions during deposition have been optimized to obtain films with good quality. Films of various thicknesses have been deposited on quartz resonators in order to use the quartz crystal microbalance (QCM) method for studying their gas sensing properties. The films' microstructure and physical properties are identified by TEM, Raman and laser elipsometry analysis. The ultimate purpose of the research is to apply TiOx thin films in gas sensors. The sorption properties of various sub-stoichiometric and stoichiometric TiO2 thin films to ammonia and other gases are investigated.

  3. Modeling for calculation of vanadium oxide film composition in reactive-sputtering process

    SciTech Connect

    Yu He; Jiang Yadong; Wang Tao; Wu Zhiming; Yu Junsheng; Wei Xiongbang

    2010-05-15

    A modified model describing the changing ratio of vanadium to oxide on the target and substrate as a function of oxygen flow is described. Actually, this ratio is extremely sensitive to the deposition conditions during the vanadium oxide (VO{sub x}) reactive magnetron-sputtering process. The method in this article is an extension of a previously presented Berg's model, where only a single stoichiometry compound layer was taken into consideration. This work deals with reactive magnetron sputtering of vanadium oxide films with different oxygen contents from vanadium metal target. The presence of vanadium mixed oxides at both target and substrate surface produced during reactive-sputtering process are included. It shows that the model can be used for the optimization of film composition with respect to oxygen flow in a stable hysteresis-free reactive-sputtering process. A systematic experimental study of deposition rate of VO{sub x} with respect to target ion current was also made. Compared to experimental results, it was verified that the theoretical calculation from modeling is in good agreement with the experimental counterpart.

  4. Reactive sputter etching of magnetic materials in an HCl plasma

    SciTech Connect

    Heijman, M.G.J.

    1988-12-01

    In an rf low-pressure HCl plasma NiZn and MnZn ferrite etch up to five times as fast as in an otherwise comparable Ar sputter etch process. Selectivity towards Al/sub 2/O/sub 3/ as an etch mask is of order 10. No redeposited material and very little trenching are seen. The etched slopes have a steepness up to 70/sup 0/, resulting from redeposition and enhanced etching on the sidewalls. This is shown by experiments and by computer simulations.

  5. Formation of cubic boron-nitride by the reactive sputter deposition of boron

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Makowiecki, D.W.; McKeman, M.A.

    1997-03-01

    Boron-nitride films are synthesized by RF magnetron sputtering boron targets where the deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are analyzed using Auger electron spectroscopy, transmission electron microscopy, nanoindentation, Raman spectroscopy and x-ray absorption spectroscopy. These techniques provide characterization of film composition, crystalline structure, hardness and chemical bonding, respectively. Reactive, rf-sputtering process parameters are established which lead to the growth of crystalline BN phases. The deposition of stable and adherent boron nitride coatings consisting of the cubic phase requires 400 `C substrate heating and the application of a 300 V negative bias.

  6. Duty cycle control in reactive high-power impulse magnetron sputtering of hafnium and niobium

    NASA Astrophysics Data System (ADS)

    Ganesan, R.; Treverrow, B.; Murdoch, B.; Xie, D.; Ross, A. E.; Partridge, J. G.; Falconer, I. S.; McCulloch, D. G.; McKenzie, D. R.; Bilek, M. M. M.

    2016-06-01

    Instabilities in reactive sputtering have technological consequences and have been attributed to the formation of a compound layer on the target surface (‘poisoning’). Here we demonstrate how the duty cycle of high power impulse magnetron sputtering (HiPIMS) can be used to control the surface conditions of Hf and Nb targets. Variations in the time resolved target current characteristics as a function of duty cycle were attributed to gas rarefaction and to the degree of poisoning of the target surface. As the operation transitions from Ar driven sputtering to metal driven sputtering, the secondary electron emission changes and reduces the target current. The target surface transitions smoothly from a poisoned state at low duty cycles to a quasi-metallic state at high duty cycles. Appropriate selection of duty cycle increases the deposition rate, eliminates the need for active regulation of oxygen flow and enables stable reactive deposition of stoichiometric metal oxide films. A model is presented for the reactive HIPIMS process in which the target operates in a partially poisoned mode with different degrees of oxide layer distribution on its surface that depends on the duty cycle. Finally, we show that by tuning the pulse characteristics, the refractive indices of the metal oxides can be controlled without increasing the absorption coefficients, a result important for the fabrication of optical multilayer stacks.

  7. Penetration, photo-reactivity and photoprotective properties of nanosized ZnO.

    PubMed

    Detoni, C B; Coradini, K; Back, P; Oliveira, C M; Andrade, D F; Beck, R C R; Pohlmann, A R; Guterres, S S

    2014-09-01

    The oxidizing capacity and skin penetration of a commercial nanosized ZnO, Nanosun™ (Micronisers-Australia), were evaluated in vitro using porcine skin. Nanosun™ was initially characterized regarding its photo-reactivity and size distribution. An assay using methylene blue was performed to confirm the Nanosun™ photo-reactivity by exposing the labile molecule to UVA irradiation in the presence and absence of the nanosized ZnO. The nanosized ZnO was photo-reactive, reducing the methylene blue concentration to 7% while its concentration remained constant in the control formulation (without ZnO). The product label states that the average particle size is 30 nm. X-ray diffraction, nitrogen sorption and UV-spectrophotometry confirmed the presence of nanometric particles of approximately 30 nm. On the other hand, laser diffractometry showed micrometric particles in the size distribution profile. These analyses indicated that the nanoparticles are arranged as agglomerates and aggregates of micrometric proportions ranging from 0.6 to 60 μm. The skin lipid peroxidation was determined by the formation of thiobarbituric acid reactive species (TBARS) and quantified by UV-spectrophotometry. When exposed to UVA radiation the nanosized ZnO applied porcine skin showed a lower production of TBARS (7.2 ± 1.5 nmol g(-1)) than the controls, the MCT applied porcine skin (18.4 ± 2.8 nmol g(-1)) and the blank porcine skin (14.0 ± 2.0 nmol g(-1)). The penetration of ZnO nanoparticles was studied by scanning electron microscopy and energy dispersive X-ray spectroscopy. The tested ZnO particles did not penetrate into viable layers of the intact porcine skin. The particles tend to accumulate on the skin folds and in these regions they may penetrate into the horny layer. PMID:24977261

  8. Formation of metal nanoparticles by short-distance sputter deposition in a reactive ion etching chamber

    SciTech Connect

    Nie Min; Meng, Dennis Desheng; Sun Kai

    2009-09-01

    A new method is reported to form metal nanoparticles by sputter deposition inside a reactive ion etching chamber with a very short target-substrate distance. The distribution and morphology of nanoparticles are found to be affected by the distance, the ion concentration, and the sputtering time. Densely distributed nanoparticles of various compositions were fabricated on the substrates that were kept at a distance of 130 mum or smaller from the target. When the distance was increased to 510 mum, island structures were formed, indicating the tendency to form continuous thin film with longer distance. The observed trend for nanoparticle formation is opposite to the previously reported mechanism for the formation of nanoparticles by sputtering. A new mechanism based on the seeding effect of the substrate is proposed to interpret the experimental results.

  9. An investigation of reactive sputtering for depositing copper indium diselenide films for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Thornton, J. A.; Cornog, D. G.; Hall, R. B.; Shea, S. P.; Meakin, J. D.

    Sputtering, particularly using magnetron methods, offers great potential for depositing films over large areas at the production volumes required for terrestrial photovoltaic applications. Single phase chalcopyrite CuInSe2 coatings have been successfully deposited by dc reactive cosputtering from Cu and In planar magnetron sources operated in an Ar+H2Se working gas. Studies of coatings deposited with various Cu and In sputtering rates and substrate temperatures indicate that the formation of near-stoichiometric coatings is aided at elevated temperatures by a re-emission mechanism which removes excess In. Photovoltaic test devices formed by evaporating CdS onto the sputtered CuInSe2 have yielded short circuit currents of about 33 mA/sq cm and efficiencies of about 4 percent.

  10. Deposition of ultrahard Ti-Si-N coatings by pulsed high-current reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Oskomov, K. V.; Zakharov, A. N.; Rabotkin, S. V.; Solov'ev, A. A.

    2016-02-01

    We report on the results of investigation of properties of ultrahard Ti-Si-N coatings deposited by pulsed high-current magnetron reactive sputtering (discharge pulse voltage is 300-900 V, discharge pulse current is up to 200 A, pulse duration is 10-100 μs, and pulse repetition rate is 20-2000 Hz). It is shown that for a short sputtering pulse (25 μs) and a high discharge current (160 A), the films exhibit high hardness (66 GPa), wear resistance, better adhesion, and a lower sliding friction coefficient. The reason is an enhancement of ion bombardment of the growing coating due to higher plasma density in the substrate region (1013 cm-3) and a manifold increase in the degree of ionization of the plasma with increasing peak discharge current (mainly due to the material being sputtered).

  11. Determination of reactive oxygen species from ZnO micro-nano structures with shape-dependent photocatalytic activity

    SciTech Connect

    He, Weiwei; Zhao, Hongxiao; Jia, Huimin; Yin, Jun-Jie; Zheng, Zhi

    2014-05-01

    Graphical abstract: ZnO micro/nano structures with shape dependent photocatalytic activity were prepared by hydrothermal reaction. The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were identified precisely by electron spin resonance spectroscopy. The type of reactive oxygen species was determined by band gap structure of ZnO. - Highlights: • ZnO micro/nano structures with different morphologies were prepared by solvothermal reaction. • Multi-pod like ZnO structures exhibited superior photocatalytic activity. • The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were characterized precisely by electron spin resonance spectroscopy. • The type of reactive oxygen species was determined by band gap structure of ZnO. - Abstract: ZnO micro/nano structures with different morphologies have been prepared by the changing solvents used during their synthesis by solvothermal reaction. Three typical shapes of ZnO structures including hexagonal, bell bottom like and multi-pod formed and were characterized by scanning electron microscopy and X-ray diffraction. Multi pod like ZnO structures exhibited the highest photocatalytic activity toward degradation of methyl orange. Using electron spin resonance spectroscopy coupled with spin trapping techniques, we demonstrate an effective way to identify precisely the generation of hydroxyl radicals, superoxide and singlet oxygen from the irradiated ZnO multi pod structures. The type of reactive oxygen species formed was predictable from the band gap structure of ZnO. These results indicate that the shape of micro-nano structures significantly affects the photocatalytic activity of ZnO, and demonstrate the value of electron spin resonance spectroscopy for characterizing the type of reactive oxygen species formed during photoexcitation of semiconductors.

  12. Reactive sputtering of δ-ZrH{sub 2} thin films by high power impulse magnetron sputtering and direct current magnetron sputtering

    SciTech Connect

    Högberg, Hans Tengdelius, Lina; Eriksson, Fredrik; Broitman, Esteban; Lu, Jun; Jensen, Jens; Hultman, Lars; Samuelsson, Mattias

    2014-07-01

    Reactive sputtering by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) of a Zr target in Ar/H{sub 2} plasmas was employed to deposit Zr-H films on Si(100) substrates, and with H content up to 61 at. % and O contents typically below 0.2 at. % as determined by elastic recoil detection analysis. X-ray photoelectron spectroscopy reveals a chemical shift of ∼0.7 eV to higher binding energies for the Zr-H films compared to pure Zr films, consistent with a charge transfer from Zr to H in a zirconium hydride. X-ray diffraction shows that the films are single-phase δ-ZrH{sub 2} (CaF{sub 2} type structure) at H content >∼55 at. % and pole figure measurements give a 111 preferred orientation for these films. Scanning electron microscopy cross-section images show a glasslike microstructure for the HiPIMS films, while the DCMS films are columnar. Nanoindentation yield hardness values of 5.5–7 GPa for the δ-ZrH{sub 2} films that is slightly harder than the ∼5 GPa determined for Zr films and with coefficients of friction in the range of 0.12–0.18 to compare with the range of 0.4–0.6 obtained for Zr films. Wear resistance testing show that phase-pure δ-ZrH{sub 2} films deposited by HiPIMS exhibit up to 50 times lower wear rate compared to those containing a secondary Zr phase. Four-point probe measurements give resistivity values in the range of ∼100–120 μΩ cm for the δ-ZrH{sub 2} films, which is slightly higher compared to Zr films with values in the range 70–80 μΩ cm.

  13. Properties of AlN films deposited by reactive ion-plasma sputtering

    SciTech Connect

    Bert, N. A.; Bondarev, A. D.; Zolotarev, V. V.; Kirilenko, D. A.; Lubyanskiy, Ya. V.; Lyutetskiy, A. V.; Slipchenko, S. O.; Petrunov, A. N.; Pikhtin, N. A. Ayusheva, K. R.; Arsentyev, I. N.; Tarasov, I. S.

    2015-10-15

    The properties of SiO{sub 2}, Al{sub 2}O{sub 3}, and AlN dielectric coatings deposited by reactive ion-plasma sputtering are studied. The refractive indices of the dielectric coatings are determined by optical ellipsometry. It is shown that aluminum nitride is the optimal material for achieving maximum illumination of the output mirror of a semiconductor laser. A crystalline phase with a hexagonal atomic lattice and oxygen content of up to 10 at % is found by transmission electron microscopy in the aluminum-nitride films. It is found that a decrease in the concentration of residual oxygen in the chamber of the reactive ion-plasma sputtering installation makes it possible to eliminate the appearance of vertical pores in the bulk of the aluminum-nitride film.

  14. Structure formation upon reactive direct current magnetron sputtering of transition metal oxide films

    SciTech Connect

    Ngaruiya, J.M.; Kappertz, O.; Mohamed, S.H.; Wuttig, M.

    2004-08-02

    A comparative study of reactive direct current magnetron sputtering for different transition metal oxides reveals crystalline films at room temperature for group 4 and amorphous films for groups 5 and 6. This observation cannot be explained by the known growth laws and is attributed to the impact of energetic particles, originating from the oxidized target, on the growing film. This scenario is supported by measured target characteristics, the evolution of deposition stress of the films, and the observed backsputtering.

  15. Transparent photostable ZnO nonvolatile memory transistor with ferroelectric polymer and sputter-deposited oxide gate

    SciTech Connect

    Park, C. H.; Im, Seongil; Yun, Jungheum; Lee, Gun Hwan; Lee, Byoung H.; Sung, Myung M.

    2009-11-30

    We report on the fabrication of transparent top-gate ZnO nonvolatile memory thin-film transistors (NVM-TFTs) with 200 nm thick poly(vinylidene fluoride/trifluoroethylene) ferroelectric layer; semitransparent 10 nm thin AgO{sub x} and transparent 130 nm thick indium-zinc oxide (IZO) were deposited on the ferroelectric polymer as gate electrode by rf sputtering. Our semitransparent NVM-TFT with AgO{sub x} gate operates under low voltage write-erase (WR-ER) pulse of {+-}20 V, but shows some degradation in retention property. In contrast, our transparent IZO-gated device displays very good retention properties but requires anomalously higher pulse of {+-}70 V for WR and ER states. Both devices stably operated under visible illuminations.

  16. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    SciTech Connect

    Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, D.; Haque, Sk Maidul; Shukla, Dinesh; Choudhary, Ram Janay

    2015-11-15

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L{sub 2,3} edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements.

  17. Investigation of the biaxial stress of Al-doped ZnO thin films on a flexible substrate with RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming

    2016-01-01

    Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.

  18. Temperature dependent electrical transport studies of self-aligned ZnO nanorods/Si heterostructures deposited by sputtering

    SciTech Connect

    Ranwa, Sapana; Dixit, Vivek; Kumar, Mahesh; Kumar Kulriya, Pawan

    2014-06-21

    Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along [0001] direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26 × 10{sup 10} cm{sup −2}, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120–300 K and it shows a rectifying behavior. Barrier height (ϕ{sub B}) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A{sup *}) was evaluated using Richardson plot of ln(I{sub o}/T{sup 2}) versus q/kT plot by linear fitting in two temperature range 120–180 K and 210–300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic equation gives mean barrier heights of 0.55 ± 0.01 eV and 0.86 ± 0.02 eV for two different temperature regions 120–180 K and 210–300 K, respectively. Modified Richardson plot provided two values of Richardson constant for two temperature regions. However, for higher temperature range (210–300 K), the calculated value of Richardson constant ∼123 A cm{sup −2} K{sup −2} was close to the ideal Richardson constant for n-Si.

  19. Parameter manipulation in the Synthesis of Ti-Cd-C Films via Reactive Sputtering in a Magnetized Sheet Plasma Facility

    NASA Astrophysics Data System (ADS)

    Villanueva, Matthew Bryan; Ramos, Henry

    2013-09-01

    Titanium-cadmium-carbon (Ti-Cd-C) deposits were achieved through reactive sputtering in a magnetized sheet plasma facility (MSPF). Titanium and cadmium metals (99.9% purity) were used as sputter targets, and high purity methane as the reactive gas. Parameters investigated were target bias, deposition duration, filling pressure, gas ratio, gas type such as acetylene, and magnetic configuration. Through X-ray diffractometry, peak signals at 2 θ = 23.3° for the treatment which implemented an independent sputtering step at -200 V target bias, and 2 θ = 12.34° for direct reactive sputtering only with -800 V target bias were recorded. Both XRD results are indicative of the formation of Ti2CdC, a theorized solid solution of Mn+1AXn phase variety. Department of Science and Technology for the project grant.

  20. Structure and mechanical properties of 3dTM ion doped RF sputtered ZnO thin films on Si (100)

    SciTech Connect

    Venkaiah, M. Singh, R.

    2014-04-24

    Mn, Fe and Mn-Fe doped ZnO thin films were deposited on Si (100) substrates by rf- magnetron sputtering using ceramic target in pure oxygen gas environment. The X-ray diffraction shows the polycrystalline wurtzite structure films. The average grain size varies from 32-50 nm, with lower grain size for Fe doped ZnO films. The room temperature loading and unloading curve are continuous without any pop-in. The Young's modulus and hardness are in the range 156-178 GPa and 14-15.5 GPa respectively.

  1. Hysteresis-free high rate reactive sputtering of niobium oxide, tantalum oxide, and aluminum oxide

    SciTech Connect

    Särhammar, Erik Berg, Sören; Nyberg, Tomas

    2014-07-01

    This work reports on experimental studies of reactive sputtering from targets consisting of a metal and its oxide. The composition of the targets varied from pure metal to pure oxide of Al, Ta, and Nb. This combines features from both the metal target and oxide target in reactive sputtering. If a certain relation between the metal and oxide parts is chosen, it may be possible to obtain a high deposition rate, due to the metal part, and a hysteresis-free process, due to the oxide part. The aim of this work is to quantify the achievable boost in oxide deposition rate from a hysteresis-free process by using a target consisting of segments of a metal and its oxide. Such an increase has been previously demonstrated for Ti using a homogeneous substoichiometric target. The achievable gain in deposition rate depends on transformation mechanisms from oxide to suboxides due to preferential sputtering of oxygen. Such mechanisms are different for different materials and the achievable gain is therefore material dependent. For the investigated materials, the authors have demonstrated oxide deposition rates that are 1.5–10 times higher than what is possible from metal targets in compound mode. However, although the principle is demonstrated for oxides of Al, Ta, and Nb, a similar behavior is expected for most oxides.

  2. Facing-target mid-frequency magnetron reactive sputtered hafnium oxide film: Morphology and electrical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Xu, Jun; Wang, You-Nian; Choi, Chi Kyu; Zhou, Da-Yu

    2016-03-01

    Amorphous hafnium dioxide (HfO2) film was prepared on Si (100) by facing-target mid-frequency reactive magnetron sputtering under different oxygen/argon gas ratio at room temperature with high purity Hf target. 3D surface profiler results showed that the deposition rates of HfO2 thin film under different O2/Ar gas ratio remain unchanged, indicating that the facing target midfrequency magnetron sputtering system provides effective approach to eliminate target poisoning phenomenon which is generally occurred in reactive sputtering procedure. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) demonstrated that the gradual reduction of oxygen vacancy concentration and the densification of deposited film structure with the increase of oxygen/argon (O2/Ar) gas flow ratio. Atomic force microscopy (AFM) analysis suggested that the surface of the as-deposited HfO2 thin film tends to be smoother, the root-meansquare roughness (RMS) reduced from 0.876 nm to 0.333 nm while O2/Ar gas flow ratio increased from 1/4 to 1/1. Current-Voltage measurements of MOS capacitor based on Au/HfO2/Si structure indicated that the leakage current density of HfO2 thin films decreased by increasing of oxygen partial pressure, which resulted in the variations of pore size and oxygen vacancy concentration in deposited thin films. Based on the above characterization results the leakage current mechanism for all samples was discussed systematically.

  3. Deposition of highly textured AlN thin films by reactive high power impulse magnetron sputtering

    SciTech Connect

    Moreira, Milena A.; Törndahl, Tobias; Katardjiev, Ilia; Kubart, Tomas

    2015-03-15

    Aluminum nitride thin films were deposited by reactive high power impulse magnetron sputtering (HiPIMS) and pulsed direct-current on Si (100) and textured Mo substrates, where the same deposition conditions were used for both techniques. The films were characterized by x-ray diffraction and atomic force microscopy. The results show a pronounced improvement in the AlN crystalline texture for all films deposited by HiPIMS on Si. Already at room temperature, the HiPIMS films exhibited a strong preferred (002) orientation and at 400 °C, no contributions from other orientations were detected. Despite the low film thickness of only 200 nm, an ω-scan full width at half maximum value of 5.1° was achieved on Si. The results are attributed to the high ionization of sputtered material achieved in HiPIMS. On textured Mo, there was no significant difference between the deposition techniques.

  4. Hall mobility of cuprous oxide thin films deposited by reactive direct-current magnetron sputtering

    SciTech Connect

    Lee, Yun Seog; Winkler, Mark T.; Siah, Sin Cheng; Brandt, Riley; Buonassisi, Tonio

    2011-05-09

    Cuprous oxide (Cu{sub 2}O) is a promising earth-abundant semiconductor for photovoltaic applications. We report Hall mobilities of polycrystalline Cu{sub 2}O thin films deposited by reactive dc magnetron sputtering. High substrate growth temperature enhances film grain structure and Hall mobility. Temperature-dependent Hall mobilities measured on these films are comparable to monocrystalline Cu{sub 2}O at temperatures above 250 K, reaching 62 cm{sup 2}/V s at room temperature. At lower temperatures, the Hall mobility appears limited by carrier scattering from ionized centers. These observations indicate that sputtered Cu{sub 2}O films at high substrate growth temperature may be suitable for thin-film photovoltaic applications.

  5. Intrinsic anomalous surface roughening of TiN films deposited by reactive sputtering

    SciTech Connect

    Auger, M. A.; Vazquez, L.; Sanchez, O.; Cuerno, R.; Castro, M.; Jergel, M.

    2006-01-15

    We study surface kinetic roughening of TiN films grown on Si(100) substrates by dc reactive sputtering. The surface morphology of films deposited for different growth times under the same experimental conditions were analyzed by atomic force microscopy. The TiN films exhibit intrinsic anomalous scaling and multiscaling. The film kinetic roughening is characterized by a set of local exponent values {alpha}{sub loc}=1.0 and {beta}{sub loc}=0.39, and global exponent values {alpha}=1.7 and {beta}=0.67, with a coarsening exponent of 1/z=0.39. These properties are correlated to the local height-difference distribution function obeying power-law statistics. We associate this intrinsic anomalous scaling with the instability due to nonlocal shadowing effects that take place during thin-film growth by sputtering.

  6. Transparent Conducting ITO Films Reactively Sputtered on Polyethylene Terephtalate Substrates Without Heat Treatment

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Hoo; Lee, Moo Young; Kim, Kwang Tae; Yoon, Sahng Hyun

    Indium tin oxide (ITO) films have been deposited on PET and glass substrates by DC reactive magnetron sputtering without post-deposition thermal treatment. High quality films have been deposited by optimizing the sputtering parameters. The influence of the working gas pressure, DC power, and oxygen partial pressure has been investigated. The lowest resistivity of ITO films deposited on PET substrates was 6×10-4Ωcm. It has been obtained at a working pressure of 3 mTorr and DC power of 30 W. The sheet resistance and optical transmittance of these films were 22 Ω/square and 84%, respectively. The best values of figures of merit for the electrical and optical chardcteristics such as T/Rsh and T10/Rsh are approximately 38.1 and 7.95 (×10-3 Ω-1), respectively.

  7. Microwave surface resistance of reactively sputtered NbN thin films

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.; Strayer, D. M.

    1987-01-01

    The surface resistance of niobium nitride (NBN) thin films was measured at 7.78 and 10.14 GHz in the temperature range of 1.5 to 4.2 K. The films were reactively sputtered on sapphire substrates to a thickness of approximately 1 micron. The surface resistance was determined by measuring the quality factor (Q) of the TE sub 011 mode of a lead-plated copper cavity where the NbN served as one end-cap of the cavity.

  8. Study of Niobium Nitride Films Produced by DC Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Hotovy, I.; Buc, D.; Brcka, J.; Srnanek, R.

    1997-05-01

    Niobium nitride films were prepared onto unheated GaAs and SiO2 substrates by dc reactive magnetron sputtering from a niobium metal target in an Ar + N2 mixed atmosphere. During deposition, the nitrogen content in the gas mixture was varied from 0 to 20%. The effects of the different nitrogen content and high-temperature annealing (with annealing temperatures ranging from 850 to 950 °C) on the composition, structural and electrical properties of the films were studied using Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM) and resistivity measurement. The correlations between technological parameters and film properties, structure and composition were established.

  9. Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics

    SciTech Connect

    Vitelaru, Catalin; Lundin, Daniel; Brenning, Nils; Minea, Tiberiu

    2013-09-02

    The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O{sub 2} gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The μs temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.

  10. Huge increase in gas phase nanoparticle generation by pulsed direct current sputtering in a reactive gas admixture

    NASA Astrophysics Data System (ADS)

    Polonskyi, Oleksandr; Peter, Tilo; Mohammad Ahadi, Amir; Hinz, Alexander; Strunskus, Thomas; Zaporojtchenko, Vladimir; Biederman, Hynek; Faupel, Franz

    2013-07-01

    Using reactive DC sputtering in a gas aggregation cluster source, we show that pulsed discharge gives rise to a huge increase in deposition rate of nanoparticles by more than one order of magnitude compared to continuous operation. We suggest that this effect is caused by an equilibrium between slight target oxidation (during "time-off") and subsequent sputtering of Ti oxides (sub-oxides) at "time-on" with high power impulse.

  11. Decorative black TiCxOy film fabricated by DC magnetron sputtering without importing oxygen reactive gas

    NASA Astrophysics Data System (ADS)

    Ono, Katsushi; Wakabayashi, Masao; Tsukakoshi, Yukio; Abe, Yoshiyuki

    2016-02-01

    Decorative black TiCxOy films were fabricated by dc (direct current) magnetron sputtering without importing the oxygen reactive gas into the sputtering chamber. Using a ceramic target of titanium oxycarbide (TiC1.59O0.31), the oxygen content in the films could be easily controlled by adjustment of total sputtering gas pressure without remarkable change of the carbon content. The films deposited at 2.0 and 4.0 Pa, those are higher pressure when compared with that in conventional magnetron sputtering, showed an attractive black color. In particular, the film at 4.0 Pa had the composition of TiC1.03O1.10, exhibited the L* of 41.5, a* of 0.2 and b* of 0.6 in CIELAB color space. These values were smaller than those in the TiC0.29O1.38 films (L* of 45.8, a* of 1.2 and b* of 1.2) fabricated by conventional reactive sputtering method from the same target under the conditions of gas pressure of 0.3 Pa and optimized oxygen reactive gas concentration of 2.5 vol.% in sputtering gas. Analysis of XRD and XPS revealed that the black film deposited at 4.0 Pa was the amorphous film composed of TiC, TiO and C. The adhesion property and the heat resisting property were enough for decorative uses. This sputtering process has an industrial advantage that the decorative black coating with color uniformity in large area can be easily obtained by plain operation because of unnecessary of the oxygen reactive gas importing which is difficult to be controlled uniformly in the sputtering chamber.

  12. Optical properties and residual stress in aluminum nitride films prepared by alternating-current dual reactive magnetron sputtering.

    PubMed

    Tang, Chien-Jen; Jaing, Cheng-Chung; Lee, Kun-Hsien; Lee, Cheng-Chung

    2011-05-01

    Aluminum nitride films were deposited by alternating-current dual reactive magnetron sputtering. The influence of different nitrogen flow and working pressures at a sputtering power of 5 kW on the refractive index, extinction coefficient, crystalline structure, residual stress, and surface roughness of aluminum nitride films was discussed. The aluminum nitride film would have high refractive index, low extinction coefficient and small residual stress at suitable nitrogen flow rate and low working pressure.

  13. Determination of the number density of excited and ground Zn atoms during rf magnetron sputtering of ZnO target

    SciTech Connect

    Maaloul, L.; Gangwar, R. K.; Stafford, L.

    2015-07-15

    A combination of optical absorption spectroscopy (OAS) and optical emission spectroscopy measurements was used to monitor the number density of Zn atoms in excited 4s4p ({sup 3}P{sub 2} and {sup 3}P{sub 0}) metastable states as well as in ground 4s{sup 2} ({sup 1}S{sub 0}) state in a 5 mTorr Ar radio-frequency (RF) magnetron sputtering plasma used for the deposition of ZnO-based thin films. OAS measurements revealed an increase by about one order of magnitude of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms by varying the self-bias voltage on the ZnO target from −115 to −300 V. Over the whole range of experimental conditions investigated, the triplet-to-singlet metastable density ratio was 5 ± 1, which matches the statistical weight ratio of these states in Boltzmann equilibrium. Construction of a Boltzmann plot using all Zn I emission lines in the 200–500 nm revealed a constant excitation temperature of 0.33 ± 0.04 eV. In combination with measured populations of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms, this temperature was used to extrapolate the absolute number density of ground state Zn atoms. The results were found to be in excellent agreement with those obtained previously by actinometry on Zn atoms using Ar as the actinometer gas [L. Maaloul and L. Stafford, J. Vac. Sci. Technol., A 31, 061306 (2013)]. This set of data was then correlated to spectroscopic ellipsometry measurements of the deposition rate of Zn atoms on a Si substrate positioned at 12 cm away from the ZnO target. The deposition rate scaled linearly with the number density of Zn atoms. In sharp contrast with previous studies on RF magnetron sputtering of Cu targets, these findings indicate that metastable atoms play a negligible role on the plasma deposition dynamics of Zn-based coatings.

  14. Influence of oxygen partial pressure on optical and structural properties of RF sputtered ZnO thin films

    NASA Astrophysics Data System (ADS)

    Murkute, P.; Saha, S.; Pandey, S. K.; Chatterjee, A.; Datta, D.; Chakrabarti, S.

    2016-02-01

    In this paper we report a detailed investigation of ZnO thin film properties deposited on Si<100> substrate at 400°C using RF sputtering. To reduce oxygen induced vacancies and interstitial defects in samples, variable oxygen flow rate during deposition followed by post growth annealing in oxygen ambient were carried out. Four samples were deposited under constant temperature condition but with variable oxygen partial pressure of 0%, 20%, 50% and 80% in Argon and Oxygen mixture, namely sample S1, S2 , S3 and S4 respectively. Deposited films were further annealed at 700, 800, 900 and 1000°C in oxygen ambient for 10s. Photoluminescence (PL) measurements carried at low temperature (18K) demonstrated near band edge emission peak of ZnO at 3.37eV. Increment in PL intensity was observed with increasing annealing temperature and a particular sample S4 annealed at 900 measured narrowest full width half maxima (FWHM) of ~0.1272eV. Defects peaks observed at lower energies were suppressed with increasing oxygen flow and post growth annealing, indicating improvement in film quality. From HRXRD measurement it was observed S4 sample annealed at 900°C has the highest peak intensity and narrowest FWHM compared to other samples, demonstrating the best crystalline property of annealed film at 900°C. Highest XRD peak intensity measured at 34.53° corresponds to (002) crystal orientation reveals that the films were highly caxis oriented. AFM results show increase in grain size with increasing oxygen flow and annealing temperature which ensures improvement in morphological properties of the film.

  15. Controlling ion fluxes during reactive sputter-deposition of SnO{sub 2}:F

    SciTech Connect

    Jäger, Timo Romanyuk, Yaroslav E.; Tiwari, Ayodhya N.; Anders, André

    2014-07-21

    Magnetron sputtering of fluorine-doped tin oxide (FTO) is a scalable deposition method for large-area transparent conducting films used in fenestration, photovoltaics, and other applications. The electrical conductivity of sputtered FTO is, however, lower than that of spray-pyrolized FTO because of the ion damage induced by high energy ions leading to a reduction of the crystal quality in sputtered FTO films. In this study, various ion species present during the reactive sputtering of a metallic tin target in a mixed Ar/O{sub 2}/CF{sub 4} atmosphere are systematically characterized by energy and mass spectrometry, and possible ways of controlling the ion fluxes are explored. Ion energy distribution functions (IEDFs) of the negative ions F{sup −} and O{sup −} exhibit large peaks at an energy corresponding to the full target voltage. Although the applied partial pressure of CF{sub 4} is about 1/30 than that of O{sub 2}, the obtained IEDFs of F{sup −} and O{sup −} have comparable peak height, which can be attributed to a higher electronegativity of F. The IEDFs of positively charged O{sup +}, O{sub 2}{sup +}, Ar{sup +}, and Sn{sup +} species have their peaks around 2–8 eV. To control ion fluxes a solenoid or permanent magnets were placed between the target and the mass spectrometer. The flux of positive ions could be varied by several orders of magnitude as a function of the applied current through the solenoid, whereas the high-energy (>100 eV) negative F{sup −} and O{sup −} ions were not notably deflected. By using permanent magnets with the B-field orthogonal to the ion trajectory, the flux of O{sup −} ions could be decreased by two orders and the exposure to the high-energy F{sup −} ions was completely suppressed.

  16. Influence of process parameters on properties of reactively sputtered tungsten nitride thin films

    SciTech Connect

    Addonizio, Maria L.; Castaldo, Anna; Antonaia, Alessandro; Gambale, Emilia; Iemmo, Laura

    2012-05-15

    Tungsten nitride (WN{sub x}) thin films were produced by reactive dc magnetron sputtering of tungsten in an Ar-N{sub 2} gas mixture. The influence of the deposition power on the properties of tungsten nitride has been analyzed and compared with that induced by nitrogen content variation in the sputtering gas. A combined analysis of structural, electrical and optical properties on thin WN{sub x} films obtained at different deposition conditions has been performed. It was found that at an N{sub 2} content of 14% a single phase structure of W{sub 2}N films was formed with the highest crystalline content. This sputtering gas composition was subsequently used for fabricating films at different deposition powers. Optical analysis showed that increasing the deposition power created tungsten nitride films with a more metallic character, which is confirmed with resistivity measurements. At low sputtering powers the resulting films were crystalline whereas, with an increase of power, an amorphous phase was also present. The incorporation of an excess of nitrogen atoms resulted in an expansion of the W{sub 2}N lattice and this effect was more pronounced at low deposition powers. Infrared analysis revealed that in WN{sub x} films deposited at low power, chemisorbed N{sub 2} molecules did not behave as ligands whereas at high deposition power they clearly appeared as ligands around metallic tungsten. In this study, the influence of the most meaningful deposition parameters on the phase transformation reaction path was established and deposition conditions suitable for producing thermally stable and highly crystalline W{sub 2}N films were found.

  17. Sputter process with time-variant reactive gas mixture for the deposition of optical multilayer and gradient layer systems

    NASA Astrophysics Data System (ADS)

    Bartzsch, H.; Weber, J.; Lau, K.; Glöß, D.; Frach, P.

    2008-09-01

    Magnetron sputtering of a silicon target in a time-variant mixture of the reactive gases oxygen and nitrogen allows the deposition of optical multilayer and gradient layer systems of silicon oxinitride at one stationary sputtering station. In this paper the processes within the sputter discharge and the properties of the growing film during the change of the reactive gas composition are investigated using optical in-situ monitoring, optical plasma emission spectroscopy and plasma impedance monitoring. A time delay between the change to the reactive gas composition and the resulting change to the film composition was observed. The time delay is longer for the transition from oxide to nitride deposition then vice versa. This asymmetry is attributed to the different affinity of nitrogen and oxygen to the silicon target. Examples of deposited antireflective coatings as well as rugate filters based on silicon oxinitride multilayer and gradient layer designs are given.

  18. Process-structure-property correlations in pulsed dc reactive magnetron sputtered vanadium oxide thin films

    SciTech Connect

    Venkatasubramanian, Chandrasekaran; Cabarcos, Orlando M.; Drawl, William R.; Allara, David L.; Ashok, S.; Horn, Mark W.; Bharadwaja, S. S. N.

    2011-11-15

    Cathode hysteresis in the reactive pulsed dc sputtering of a vanadium metal target was investigated to correlate the structural and electrical properties of the resultant vanadium oxide thin films within the framework of Berg's model [Berg et al., J. Vac. Sci. Technol. A 5, 202 (1987)]. The process hysteresis during reactive pulsed dc sputtering of a vanadium metal target was monitored by measuring the cathode (target) current under different total gas flow rates and oxygen-to-argon ratios for a power density of {approx}6.6.W/cm{sup 2}. Approximately 20%-25% hysteretic change in the cathode current was noticed between the metallic and oxidized states of the V-metal target. The extent of the hysteresis varied with changes in the mass flow of oxygen as predicted by Berg's model. The corresponding microstructure of the films changed from columnar to equiaxed grain structure with increased oxygen flow rates. Micro-Raman spectroscopy indicates subtle changes in the film structure as a function of processing conditions. The resistivity, temperature coefficient of resistance, and charge transport mechanism, obeying the Meyer-Neldel relation [Meyer and Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)], were correlated with the cathode current hysteric behavior.

  19. A parametric model for reactive high-power impulse magnetron sputtering of films

    NASA Astrophysics Data System (ADS)

    Kozák, Tomáš; Vlček, Jaroslav

    2016-02-01

    We present a time-dependent parametric model for reactive HiPIMS deposition of films. Specific features of HiPIMS discharges and a possible increase in the density of the reactive gas in front of the reactive gas inlets placed between the target and the substrate are considered in the model. The model makes it possible to calculate the compound fractions in two target layers and in one substrate layer, and the deposition rate of films at fixed partial pressures of the reactive and inert gas. A simplified relation for the deposition rate of films prepared using a reactive HiPIMS is presented. We used the model to simulate controlled reactive HiPIMS depositions of stoichiometric \\text{Zr}{{\\text{O}}2} films, which were recently carried out in our laboratories with two different configurations of the {{\\text{O}}2} inlets in front of the sputtered target. The repetition frequency was 500 Hz at the deposition-averaged target power densities of 5 Wcm-2and 50 Wcm-2 with a pulse-averaged target power density up to 2 kWcm-2. The pulse durations were 50 μs and 200 μs. Our model calculations show that the to-substrate {{\\text{O}}2} inlet provides systematically lower compound fractions in the target surface layer and higher compound fractions in the substrate surface layer, compared with the to-target {{\\text{O}}2} inlet. The low compound fractions in the target surface layer (being approximately 10% at the deposition-averaged target power density of 50 Wcm-2 and the pulse duration of 200 μs) result in high deposition rates of the films produced, which are in agreement with experimental values.

  20. Influence of the magnetron on the growth of aluminum nitride thin films deposited by reactive sputtering

    SciTech Connect

    Iriarte, G. F.

    2010-03-15

    Aluminum nitride (AlN) thin films deposited on high-vacuum systems without substrate heating generally exhibit a poor degree of c-axis orientation. This is due to the nonequilibrium conditions existing between the energy of the sputtered particles and the energy at the substrate surface. The application of substrate bias or substrate temperature is known to improve the adatom mobility by delivering energy to the substrate; both are hence well-established crystal growth promoting factors. It is well known that low sputtering pressures can be used as a parameter improving the growth of highly c-axis oriented aluminum nitride films at room temperature even without applying bias voltage to the substrate. Generally, the use of high pressures implies thermalization of particles within the gas phase and is considered to increase the energy gap between these and the substrate surface. However, in later experiments we have learned that the use of high processing pressures does not necessarily implies a detriment of crystallographic orientation in the films. By measuring (for the first time to the author's knowledge) the full width at half maximum value of the rocking curve of the 0002-AlN peak at several positions along the 100 mm diameter (100)-silicon wafers on which aluminum nitride thin films were deposited by reactive sputtering, a new effect was observed. Under certain processing conditions, the growth of the AlN thin films is influenced by the target magnetron. More precisely, their degree of c-axis orientation varies at wafer areas locally coincident under the target magnetron. This effect should be considered, especially where large area substrates are employed such as in silicon wafer foundry manufacturing processes.

  1. Magnetic field strength influence on the reactive magnetron sputter deposition of Ta2O5

    NASA Astrophysics Data System (ADS)

    Hollerweger, R.; Holec, D.; Paulitsch, J.; Rachbauer, R.; Polcik, P.; Mayrhofer, P. H.

    2013-08-01

    Reactive magnetron sputtering enables the deposition of various thin films to be used for protective as well as optical and electronic applications. However, progressing target erosion during sputtering results in increased magnetic field strengths at the target surface. Consequently, the glow discharge, the target poisoning, and hence the morphology, crystal structure and stoichiometry of the prepared thin films are influenced. Therefore, these effects were investigated by varying the cathode current Im between 0.50 and 1.00 A, the magnetic field strength B between 45 and 90 mT, and the O2/(Ar + O2) flow rate ratio Γ between 0% and 100%. With increasing oxygen flow ratio a substoichiometric TaOx oxide forms at the metallic Ta target surface which further transfers to a non-conductive tantalum pentoxide Ta2O5, impeding a stable dc glow discharge. These two transition zones (from Ta to TaOx and from TaOx to Ta2O5) shift to higher oxygen flow rates for increasing target currents. In contrast, increasing the magnetic field strength (e.g., due to sputter erosion) mainly shifts the TaOx to Ta2O5 transition to lower oxygen flow rates while marginally influencing the Ta to TaOx transition. To allow for a stable dc glow discharge (and to suppress the formation of non-conductive Ta2O5 at the target) even at Γ = 100% either a high target current (Im ⩾ 1 A) or a low magnetic field strength (B ⩽ 60 mT) is necessary. These conditions are required to prepare stoichiometric and fully crystalline Ta2O5 films.

  2. Photocatalytic and photoelectrochemical performance of Ta3N5 microcolumn films fabricated using facile reactive sputtering

    NASA Astrophysics Data System (ADS)

    Lin, Der-Hwa; Chang, Kao-Shuo

    2016-08-01

    This paper presents the photocatalytic and photoelectrochemical (PEC) properties of Ta3N5 microcolumn films. The highlights include (1) overcoming the fundamental barrier of standard reactive sputtering for fabricating microcolumns; (2) preventing unnecessary complexity from complicating facile sputtering; (3) an alternative but effective approach for fabricating Ta3N5 without using caustic NH3 gases; (4) investigating morphology tuning for favorable photocatalysis and PEC reactions; and (5) elucidating the relationships of the structures, morphologies, and properties of Ta3N5 microcolumns. High-resolution transmission electron microscopy and selective-area electron diffraction verified the polycrystallinity of Ta3N5 microcolumns, of which the elemental compositions and stoichiometry were measured using electron-probe energy dispersive spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The corresponding band gap was determined to be approximately 2.1 eV. The sample exhibited a superior photodegradation capability; the photodegradation rate constant k was determined to be approximately 1.4 times higher than that of P25 under UV irradiation. A photocatalytic and PEC cycling test indicated the photodegradation reusability and photostability of the Ta3N5 microcolumns. The incident photon-to-current efficiency performance reached 6%, suggesting that these microcolumns hold potential for application in PEC devices.

  3. Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites.

    PubMed

    Ramadan, Khaled Sayed Elbadawi; Evoy, Stephane

    2015-01-01

    Piezoelectric aluminum nitride thin films were deposited on aluminum-molybdenum (AlMo) metallic nanocomposites using reactive DC sputtering at room temperature. The effect of sputtering parameters on film properties was assessed. A comparative study between AlN grown on AlMo and pure aluminum showed an equivalent (002) crystallographic texture. The piezoelectric coefficients were measured to be 0.5±0.1 C m(-2) and 0.9±0.1 C m(-2), for AlN deposited on Al/0.32Mo and pure Al, respectively. Films grown onto Al/0.32Mo however featured improved surface roughness. Roughness values were measured to be 1.3nm and 5.4 nm for AlN films grown on AlMo and on Al, respectively. In turn, the dielectric constant was measured to be 8.9±0.7 for AlN deposited on Al/0.32Mo seed layer, and 8.7±0.7 for AlN deposited on aluminum; thus, equivalent within experimental error. Compatibility of this room temperature process with the lift-off patterning of the deposited AlN is also reported.

  4. Optical and electron transport properties of reactively sputtered Cu/sub x/S

    SciTech Connect

    Leong, J.Y.C.

    1980-06-30

    Thin films of Cu/sub x/S were deposited on glass slides by sputtering Cu in a reactive H/sub 2/S/Ar environment. Optical transmittance and reflectance measurements were used to explore the infrared absorption spectra of the material. Analysis of the absorption edge characteristics resulted in the identification of an indirect bandgap at 1.15 (+-.05) eV, a direct bandgap at 1.30 (+-.05) eV, and an electron effective mass of 1.0 (+-0.2) m/sub 0/. Electrical data consisting of resistivity and Hall effect measurements from liquid nitrogen to room temperature were analyzed to determine the dominant scattering mechanisms limiting the hole mobility in the material. Ionized impurity scattering was the dominant mechanism at low temperatures (T < 100/sup 0/K) and polar optical phonon scattering was most effective at high temperatures (T > 150/sup 0/K). All films were p-type. Effects of sputtering gas pressure, heat treatments, and temperature on the properties were studied.

  5. Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites

    PubMed Central

    Ramadan, Khaled Sayed Elbadawi; Evoy, Stephane

    2015-01-01

    Piezoelectric aluminum nitride thin films were deposited on aluminum-molybdenum (AlMo) metallic nanocomposites using reactive DC sputtering at room temperature. The effect of sputtering parameters on film properties was assessed. A comparative study between AlN grown on AlMo and pure aluminum showed an equivalent (002) crystallographic texture. The piezoelectric coefficients were measured to be 0.5±0.1 C m-2 and 0.9±0.1 C m-2, for AlN deposited on Al/0.32Mo and pure Al, respectively. Films grown onto Al/0.32Mo however featured improved surface roughness. Roughness values were measured to be 1.3nm and 5.4 nm for AlN films grown on AlMo and on Al, respectively. In turn, the dielectric constant was measured to be 8.9±0.7 for AlN deposited on Al/0.32Mo seed layer, and 8.7±0.7 for AlN deposited on aluminum; thus, equivalent within experimental error. Compatibility of this room temperature process with the lift-off patterning of the deposited AlN is also reported. PMID:26193701

  6. Low Temperature Reactive Sputtering of Thin Aluminum Nitride Films on Metallic Nanocomposites.

    PubMed

    Ramadan, Khaled Sayed Elbadawi; Evoy, Stephane

    2015-01-01

    Piezoelectric aluminum nitride thin films were deposited on aluminum-molybdenum (AlMo) metallic nanocomposites using reactive DC sputtering at room temperature. The effect of sputtering parameters on film properties was assessed. A comparative study between AlN grown on AlMo and pure aluminum showed an equivalent (002) crystallographic texture. The piezoelectric coefficients were measured to be 0.5±0.1 C m(-2) and 0.9±0.1 C m(-2), for AlN deposited on Al/0.32Mo and pure Al, respectively. Films grown onto Al/0.32Mo however featured improved surface roughness. Roughness values were measured to be 1.3nm and 5.4 nm for AlN films grown on AlMo and on Al, respectively. In turn, the dielectric constant was measured to be 8.9±0.7 for AlN deposited on Al/0.32Mo seed layer, and 8.7±0.7 for AlN deposited on aluminum; thus, equivalent within experimental error. Compatibility of this room temperature process with the lift-off patterning of the deposited AlN is also reported. PMID:26193701

  7. Composition and resistivity changes of reactively sputtered W-Si-N thin films under vacuum annealing

    SciTech Connect

    Vomiero, A.; Boscolo Marchi, E.; Mariotto, G.; Quaranta, A.; Della Mea, G.; Ottaviani, G.; Tonini, R.; Butturi, M.; Martinelli, G.

    2006-01-16

    W-Si-N layers about 200 nm thick with different nitrogen content were reactively sputtered from a W{sub 5}Si{sub 3} target on oxidized silicon substrates. The thermal stability of the films' composition and resistivity was studied with ion beam analysis and four-point probe measurements. Upon vacuum annealing from 600 to 980 deg. C for 1.5 h, a sample with an initial 56 at. % of nitrogen gradually loses nitrogen down to 36%. This composition lies close to the W-Si{sub 3}N{sub 4} tie line. Concurrently, the room temperature resistivity decreases from 4.7 to about 2 m{omega} cm. The composition changes only a little for a sample whose initial composition is near the W-Si{sub 3}N{sub 4} tie line and the resistivity changes significantly less than for the nitrogen-rich film. Interpretations are discussed.

  8. Structural and thermal properties of nanocrystalline CuO synthesized by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Verma, M.; Gupta, V. K.; Gautam, Y. K.; Dave, V.; Chandra, R.

    2014-01-01

    Recent research has shown immense application of metal oxides like CuO, MgO, CaO, Al2O3, etc. in different areas which includes chemical warfare agents, medical drugs, magnetic storage media and solar energy transformation. Among the metal oxides, CuO nanoparticles are of special interest because of their excellent gas sensing and catalytic properties. In this paper we report structural and thermal properties of CuO synthesized by reactive magnetron DC sputtering. The synthesized nanoparticles were characterized by X-ray diffractometer. The XRD result reveals that as DC power increased from 30W to 80W, size of the CuO nanoparticles increased. The same results have been verified through TEM analysis. Thermal properties of these particles were studied using thermogravimetry.

  9. Reactive DC magnetron sputtered zirconium nitride (ZrN) thin film and its characterization

    NASA Astrophysics Data System (ADS)

    Subramanian, B.; Ashok, K.; Sanjeeviraja, C.; Kuppusami, P.; Jayachandran, M.

    2008-05-01

    Zirconium nitride (ZrN) thin films were prepared by using reactive direct current (DC) magnetron sputtering onto different substrates. A good polycrystalline nature with face centered cubic structure was observed from X-ray Diffraction for ZrN thin films. The observed 'd' values from the X-ray Diffraction pattern were found to be in good agreement with the standard 'd' values (JCPDS-89-5269). An emission peak is observed at 587nm from Photoluminescence studies for the excitation at 430nm. The resistivity value (ρ) of 2.1798 (μΩ cm) was observed. ZrN has high wear resistance and low coefficient of friction. A less negative value of Ecorr and lower value of Icorr observed for ZrN / Mild Steel (MS) clearly confirm the better corrosion resistance than the bare substrate. Also the higher Rct value and lower Cdl value was observed for ZrN / MS from Nyquist - plot.

  10. Characterization of RF reactively sputtered Cu-In-S thin films

    NASA Astrophysics Data System (ADS)

    He, Y. B.; Polity, A.; Gregor, R.; Pfisterer, D.; Österreicher, I.; Hasselkamp, D.; Meyer, B. K.

    2001-12-01

    The ternary compound semiconductor CuInS 2 has attracted much attention owing to its potential applications in photovoltaic devices. We deposit CuInS 2 films on float glass substrates by a reactive radio frequency sputter process using a Cu-In inlay target and H 2S gas in one step. The morphology of the films was studied by Atomic Force Microscopy, X-ray Diffraction was used to check the crystal structure of the films. The composition of the layers was determined by Rutherford Back-scattering Spectroscopy and Energy-Dispersive X-ray Analysis. The electrical properties of the layers, i.e. the carrier concentration, Hall mobility, and specific resistivity and their dependencies on temperature were investigated by Hall effect measurements.

  11. Electron transport and defect structure in highly conducting reactively sputtered ultrathin tin oxide films

    SciTech Connect

    Bansal, Shikha; Pandya, Dinesh K. Kashyap, Subhash C.

    2014-02-24

    Electrical conduction behavior of ultrathin (5–110 nm) SnO{sub 2} films reactively sputtered at 150–400 °C substrate temperatures is presented. The surface roughness studies revealed that the films with lower thickness were smoother (≤0.6 nm). Stoichiometry/defect structure of the films obtained from X-ray photoelectron spectroscopy data and electron mobility are found to be dependent on film thickness and substrate temperature. The observed increase in conductivity of semi-metallic films with decrease in film thickness is attributed to changes in defect structure and surface roughness. Highest value of conductivity of about 715 Ω{sup −1} cm{sup −1} is obtained for 5 nm thick films deposited at 300 °C.

  12. Perpendicular magnetic anisotropy of Mn4N films fabricated by reactive sputtering method

    NASA Astrophysics Data System (ADS)

    Kabara, Kazuki; Tsunoda, Masakiyo

    2015-05-01

    Manganese nitride films were fabricated on MgO substrates by changing N2 flow ratio into Ar gas ( P N2 ) during reactive sputtering deposition of the films, and their crystal structures and magnetic properties were investigated. Single phased ɛ-Mn4N films were obtained when P N2 was 5%-9%, and the tetragonal lattice distortion was identified in all the Mn4N films (the lattice constant ratio, c/a = 0.99). Perpendicular magnetic anisotropy was observed in all the specimens. The Mn4N film, fabricated with P N2 = 8%, has a low saturation magnetization (Ms = 110 emu/cc) and relatively high magnetic anisotropic energy (Ku = 8.8 × 105 erg/cc). Both Ms and Ku of the films drastically changed with mixing other phases (α-Mn, β-Mn, η-Mn3N2, and possibly γ-Mn) by varying P N2 .

  13. Deposition of vanadium oxide films by direct-current magnetron reactive sputtering

    NASA Technical Reports Server (NTRS)

    Kusano, E.; Theil, J. A.; Thornton, John A.

    1988-01-01

    It is demonstrated here that thin films of vanadium oxide can be deposited at modest substrate temperatures by dc reactive sputtering from a vanadium target in an O2-Ar working gas using a planar magnetron source. Resistivity ratios of about 5000 are found between a semiconductor phase with a resistivity of about 5 Ohm cm and a metallic phase with a resistivity of about 0.001 Ohm cm for films deposited onto borosilicate glass substrates at about 400 C. X-ray diffraction shows the films to be single-phase VO2 with a monoclinic structure. The VO2 films are obtained for a narrow range of O2 injection rates which correspond to conditions where cathode poisoning is just starting to occur.

  14. Structural and thermal properties of nanocrystalline CuO synthesized by reactive magnetron sputtering

    SciTech Connect

    Verma, M.; Gupta, V. K.; Gautam, Y. K.; Dave, V.; Chandra, R.

    2014-01-28

    Recent research has shown immense application of metal oxides like CuO, MgO, CaO, Al{sub 2}O{sub 3}, etc. in different areas which includes chemical warfare agents, medical drugs, magnetic storage media and solar energy transformation. Among the metal oxides, CuO nanoparticles are of special interest because of their excellent gas sensing and catalytic properties. In this paper we report structural and thermal properties of CuO synthesized by reactive magnetron DC sputtering. The synthesized nanoparticles were characterized by X-ray diffractometer. The XRD result reveals that as DC power increased from 30W to 80W, size of the CuO nanoparticles increased. The same results have been verified through TEM analysis. Thermal properties of these particles were studied using thermogravimetry.

  15. Research on titanium nitride thin films deposited by reactive magnetron sputtering for MEMS applications

    NASA Astrophysics Data System (ADS)

    Merie, Violeta; Pustan, Marius; Negrea, Gavril; Bîrleanu, Corina

    2015-12-01

    Titanium nitride can be used among other materials as diffusion barrier for MEMS (microelectromechanical systems) applications. The aim of this study is to elaborate and to characterize at nanoscale titanium nitride thin films. The thin films were deposited by reactive magnetron sputtering on silicon substrates using a 99.99% purity titanium target. Different deposition parameters were employed. The deposition temperature, deposition time, substrate bias voltage and the presence/absence of a titanium buffer layer are the parameters that were modified. The so-obtained films were then investigated by atomic force microscopy. A significant impact of the deposition parameters on the determined mechanical and tribological characteristics was highlighted. The results showed that the titanium nitride thin films deposited for 20 min at room temperature without the presence of a titanium buffer layer when a negative bias of -90 V was applied to the substrate is characterized by the best tribological and mechanical behavior.

  16. Studies on optoelectronic properties of DC reactive magnetron sputtered chromium doped CdO thin films

    SciTech Connect

    Hymavathi, B. Rao, T. Subba; Kumar, B. Rajesh

    2014-10-15

    Cr doped CdO thin films were deposited on glass substrates by DC reactive magnetron sputtering method and subsequently annealed from 200 °C to 500 °C. X-ray diffraction analysis showed that the films exhibit (1 1 1) preferred orientation. The optical transmittance of the films increases from 64% to 88% with increasing annealing temperature. The optical band gap values were found to be decreased from 2.77 to 2.65 eV with the increase of annealing temperature. The decrease in optical band gap energy with increasing annealing temperature can be attributed to improvement in the crystallinity of the films and may also be due to quantum confinement effect. A minimum resistivity of 2.23 × 10{sup −4} Ω.cm and sheet resistance of 6.3 Ω/sq is obtained for Cr doped CdO film annealed at 500 °C.

  17. Visible light-responsive titanium dioxide thin film prepared by reactive sputtering.

    PubMed

    Jeong, Woon-Jo; Moon, In-Seob; Cho, Soon-Kye; Yang, Hyeon-Hun; Park, Gye-Choon; Gu, Hal-Bon; Kim, Ki-Joong; Ahn, Ho-Geun

    2011-02-01

    TiO2 is a wide band-gap semiconductor (3.4 eV) and can only absorb about 5% of sun light in the ultraviolet light region, which largely limits its practical applications because of the lower utility of sun light and quantum yield. In order to move the absorption edge of TiO2 films to visible spectrum range, we have made the impurity level within a band-gap of TiO2 thin film by introduction of oxygen vacancy. Oxygen-defected TiO2 photo-catalyst have prepared by reactive sputtering with the partial pressure of Ar:O2 = 76.7:23.3 approximately 98.5:1.5 ratios. As a result, we could have the impurity level of about 2.75 eV on condition that oxygen partial pressure is 2.9%. And the photocatalytic activity was realized at 400 nm wavelength.

  18. Mo-doped BiVO4 photoanodes synthesized by reactive sputtering.

    PubMed

    Chen, Le; Toma, Francesca M; Cooper, Jason K; Lyon, Alan; Lin, Yongjing; Sharp, Ian D; Ager, Joel W

    2015-03-01

    We report a scalable and reproducible method for reactive co-sputtering of Mo-doped BiVO4 thin films with broad compositional control. Optimal photoanode performance is achieved at a Mo concentration of 3 at. %. Incorporation of Mo promotes growth of large grains and reduces majority carrier transport limitations, resulting in maximum AM1.5G photocurrent densities of 3.5 mA cm(-2) at 1.23 V vs. RHE in pH 6.8 buffer solution containing 0.1 M Na2 SO3 as a hole scavenger. Operation as a front-illuminated water oxidation photoanode is achieved by balancing the operational stability, catalytic activity, and parasitic optical absorption of a FeOOH oxygen evolution catalyst. FeOOH/Mo:BiVO4 thin film photoanodes enable water oxidation under the front-side illumination conditions used in integrated tandem water splitting devices. PMID:25705871

  19. 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.

  20. The impact of oxygen incorporation during intrinsic ZnO sputtering on the performance of Cu(In,Ga)Se{sub 2} thin film solar cells

    SciTech Connect

    Lee, Kkotnim; Ok, Eun-A; Park, Jong-Keuk; Kim, Won Mok; Baik, Young-Joon; Jeong, Jeung-hyun; Kim, Donghwan

    2014-08-25

    We investigated the impact of incorporating 2% oxygen during intrinsic ZnO sputtering on the efficiency of Cu(In,Ga)Se{sub 2} solar cells. The added oxygen not only reduced the optical absorption loss of the Al-doped ZnO overlaying layer but also improved the electronic properties of the underlying CdS/Cu(In,Ga)Se{sub 2} by increasing carrier density, lowering defect level, and increasing diffusion length, eventually enhancing J{sub SC}, V{sub OC}, and fill factor. It was found that the Na doping concentration was significantly increased around the CdS/Cu(In,Ga)Se{sub 2} junction due to the plasma-activated oxygen. The improved electronic properties are better explained by the increased Na concentration than simply the oxygen-related defect passivation.

  1. DC sputtering assisted nano-branched core-shell TiO2/ZnO electrodes for application in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Zengming; Hu, Yong; Qin, Fuyu; Ding, Yutian

    2016-07-01

    TiO2/ZnO core-shell photo-anodes with a large surface area were synthesised by a combination of chemical growth and direct current (DC) magnetron sputtering (MS). The use of these combined methods for the advancement of dye-sensitized solar cells (DSSCs) was discussed. An understanding of the morphology and structure of this core-shell material was obtained from the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the thickness of the ZnO nanoshells (as assessed by using TEM), prepared by MS, has a significant effect on improvements in the conversion efficiency. The conversion efficiency can be greatly improved from 0.06% to 0.72% by optimising different experimental conditions, such as ZnO nanoshell MS time and chemical bath deposition time. The enhanced efficiency may be attributed to the emergence of a ZnO energy barrier and the improvement of the photo-anode surface area.

  2. Defect analysis by transmission electron microscopy of epitaxial Al-doped ZnO films grown on (0001) ZnO and a-sapphire by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Rengachari, Mythili; Bikowski, André; Ellmer, Klaus

    2016-07-01

    Microstructural investigations by cross section Transmission Electron Microscopy have been carried out on Al-doped ZnO films epitaxially grown on (0001) ZnO and a-sapphire by RF magnetron sputtering, since it is known that crystallographic defects influence the physical properties of ZnO films. Threading dislocations and basal stacking faults were the predominant defects observed in these films, which were dependent on the type of the substrate and its orientation. The orientational relationship between the ZnO:Al film and the a-sapphire was determined to be ( 11 2 ¯ 0 )sapphire||(0001)ZnO:Al and [0001]sapphire||[ 11 2 ¯ 0 ]ZnO:Al. The density of dislocations in the heteroepitaxial film of ZnO:Al on a-sapphire was higher than that of the homoepitaxial film of ZnO:Al on undoped ZnO, due to the difference in the lattice mismatch, which also affected the crystallinity of the film.

  3. Reactive sputter deposition of pyrite structure transition metal disulfide thin films: Microstructure, transport, and magnetism

    SciTech Connect

    Baruth, A.; Manno, M.; Narasimhan, D.; Shankar, A.; Zhang, X.; Johnson, M.; Aydil, E. S.; Leighton, C.

    2012-09-01

    Transition metal disulfides crystallizing in the pyrite structure (e.g., TMS{sub 2}, with TM = Fe, Co, Ni, and Cu) are a class of materials that display a remarkably diverse array of functional properties. These properties include highly spin-polarized ferromagnetism (in Co{sub 1-x}Fe{sub x}S{sub 2}), superconductivity (in CuS{sub 2}), an antiferromagnetic Mott insulating ground state (in NiS{sub 2}), and semiconduction with close to optimal parameters for solar absorber applications (in FeS{sub 2}). Exploitation of these properties in heterostructured devices requires the development of reliable and reproducible methods for the deposition of high quality pyrite structure thin films. In this manuscript, we report on the suitability of reactive sputter deposition from metallic targets in an Ar/H{sub 2}S environment as a method to achieve exactly this. Optimization of deposition temperature, Ar/H{sub 2}S pressure ratio, and total working gas pressure, assisted by plasma optical emission spectroscopy, reveals significant windows over which deposition of single-phase, polycrystalline, low roughness pyrite films can be achieved. This is illustrated for the test cases of the ferromagnetic metal CoS{sub 2} and the diamagnetic semiconductor FeS{sub 2}, for which detailed magnetic and transport characterization are provided. The results indicate significant improvements over alternative deposition techniques such as ex situ sulfidation of metal films, opening up exciting possibilities for all-sulfide heterostructured devices. In particular, in the FeS{sub 2} case it is suggested that fine-tuning of the sputtering conditions provides a potential means to manipulate doping levels and conduction mechanisms, critical issues in solar cell applications. Parenthetically, we note that conditions for synthesis of phase-pure monosulfides and thiospinels are also identified.

  4. Synthesis and characterization of delafossite thin films by reactive RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Asmat Uceda, Martin Antonio

    This work presents a comparative study on optical and electrical properties of CuAlO2 thin films on sapphire (0001) substrates deposited with two different growth conditions using reactive RF-magnetron sputtering technique from metallic Cu and Al targets. CuAlO2 is a very promising material for transparent electronic applications, it is intended that comparison of results obtained from both approaches, could lead to optimization and control of the physical properties of this material, namely its electrical conductivity and optical transmittance. All samples were heat treated at 1100°C using rapid thermal annealing with varying time and rate of cooling. The effect of sputtering conditions and different annealing time on phase formation and evolution is studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that for most of the samples CuAlO2 phase is formed after 60 min of annealing time, but secondary phases were also present that depend on the deposition conditions. However, pure CuAlO2 phase was obtained for annealed CuO on sapphire films with annealing time of 60 min. The optical properties obtained from UV-Visible spectroscopic measurement reveals indirect and direct optical band gaps for CuAlO2 films and were found to be 2.58 and 3.72 eV respectively. The films show a transmittance of about 60% in the visible range. Hall effect measurements indicate p-type conductivity. Van der Pauw technique was used to measure resistivity of the samples. The highest electrical conductivity and charge carrier concentration obtained were of 1.01x10-1S.cm -1 and 3.63 x1018 cm-3 respectively.

  5. Effects of the high-temperature-annealed self-buffer layer on the improved properties of ZnO epilayers grown by helicon-wave-excited-plasma sputtering epitaxy on a-plane sapphire substrates

    NASA Astrophysics Data System (ADS)

    Koyama, T.; Fouda, A. N.; Shibata, N.; Chichibu, S. F.

    2007-10-01

    The use of the high-temperature-annealed self-buffer layer (HITAB) enabled to observe free A-and B-exciton emissions at 9K from ZnO heteroepitaxial films grown by the sputtering epitaxy method using a helicon-wave-excited plasma on uniaxially nearly lattice-matched (112¯0) Al2O3 substrates. The result was correlated with a twofold decrease in the densities of threading dislocations having both the screw and edge components, according to the dislocation concealing in ZnO HITAB due to lateral mass transport of low-temperature deposited ZnO nanocrystalline grains during high temperature annealing.

  6. 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.

  7. Deposition of LaMnO 3 buffer layer on IBAD-MgO template by reactive DC sputtering

    NASA Astrophysics Data System (ADS)

    Kim, H. S.; Oh, S. S.; Ha, H. S.; Ko, R. K.; Ha, D. W.; Kim, T. H.; Youm, D. J.; Lee, N. J.; Moon, S. H.; Yoo, S. I.; Park, C.

    2009-10-01

    The deposition conditions of LaMnO 3 (LMO) buffer layer on Ion Beam Assisted Deposition (IBAD)-MgO template by reactive DC sputtering were investigated. We developed a specially designed chamber for reactive DC magnetron sputtering. The deposition chamber was composed of two sputtering guns with the mixed metallic target of La (50 at%) + Mn (50 at%), halogen lamp heater, QCM (Quartz Crystal Microbalance), RGA (Residual Gas Analyzer) and reel to reel tape moving system. We investigated the effect of oxygen flow rate on the deposition rate of LMO layer. We found that there was an optimal range of oxygen flow rate to have the desired layer. Above the range, the deposition rate decreased sharply and plasma was unstable. Below the range, the deposited layer was partially metallic. We investigated the effect of substrate temperature on the texturing of LMO layer. The texturing of LMO layer was improved by increasing the substrate temperature. We investigated the effect of deposition rate on the texturing of LMO layer. The LMO layer has a good texture in the deposition rate range of 0.07-0.21 nm/s. We confirmed that deposition rate had little effect on the texturing of LMO layer in the deposition rate range. Sm 1Ba 2Cu 3O 7-d superconducting layer was deposited on the LMO(reactive)/IBAD-MgO template. I c and J c were 81.6 A and 1 MA/cm 2. This means that LMO layer deposited by reactive DC sputtering shows a good performance in superconductor coated conductor.

  8. 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.

  9. Structural, optical and electrical properties of WOxNy filmsdeposited by reactive dual magnetron sputtering

    SciTech Connect

    Mohamed, Sodky H.; Anders, Andre

    2006-06-05

    Thin films of tungsten oxynitride were prepared by dual magnetron sputtering of tungsten using argon/oxygen/nitrogen gas mixtures with various nitrogen/oxygen ratios. The presence of even small amounts of oxygen had a great effect not only on the composition but on the structure of WOxNy films, as shown by Rutherford backscattering and x-ray diffraction, respectively. Significant incorporation of nitrogen occurred only when the nitrogen partial pressure exceeded 89 percent of the total reactive gas pressure. Sharp changes in the stoichiometry, deposition rate, room temperature resistivity, electrical activation energy and optical band gap were observed when the nitrogen/oxygen ratio was high.The deposition rate increased from 0.31 to 0.89 nm/s, the room temperature resistivity decreased from 1.65 x 108 to 1.82 x 10-2 ?cm, the electrical activation energy decreased from 0.97 to 0.067 eV, and the optical band gap decreased from 3.19 to 2.94 eV upon nitrogen incorporation into the films. WOxNy films were highly transparent as long as the nitrogen incorporation was low, and were brownish (absorbing) and partially reflecting as nitrogen incorporation became significant.

  10. Structural and optical properties of DC reactive magnetron sputtered zinc aluminum oxide thin films

    SciTech Connect

    Kumar, B. Rajesh; Rao, T. Subba

    2014-10-15

    Highly transparent conductive Zinc Aluminum Oxide (ZAO) thin films have been deposited on glass substrates using DC reactive magnetron sputtering method. The thin films were deposited at 200 °C and post-deposition annealing from 15 to 90 min. XRD patterns of ZAO films exhibit only (0 0 2) diffraction peak, indicating that they have c-axis preferred orientation perpendicular to the substrate. Scanning electron microscopy (SEM) is used to study the surface morphology of the films. The grain size obtained from SEM images of ZAO thin films are found to be in the range of 20 - 26 nm. The minimum resistivity of 1.74 × 10{sup −4} Ω cm and an average transmittance of 92% are obtained for the thin film post annealed for 30 min. The optical band gap of ZAO thin films increased from 3.49 to 3.60 eV with the increase of annealing time due to Burstein-Moss effect. The optical constants refractive index (n) and extinction coefficient (k) were also determined from the optical transmission spectra.

  11. Reactively-sputtered zinc semiconductor films of high conductivity for heterojunction devices

    NASA Technical Reports Server (NTRS)

    Stirn, Richard J. (Inventor)

    1986-01-01

    A high conductivity, n-doped semiconductor film is produced from zinc, or Zn and Cd, and group VI elements selected from Se, S and Te in a reactive magnetron sputtering system having a chamber with one or two targets, a substrate holder, means for heating the substrate holder, and an electric field for ionizing gases in the chamber. Zinc or a compound of Zn and Cd is placed in the position of one of the two targets and doping material in the position of the other of the two targets. Zn and Cd may be placed in separate targets while a dopant is placed in the third target. Another possibility is to place an alloy of Zn and dopant, or Zn, Cd and dopant in one target, thus using only one target. A flow of the inert gas is ionized and directed toward said targets, while a flow of a reactant gas consisting of hydrides of the group VI elements is directed toward a substrate on the holder. The targets are biased to attract negatively ionized inert gas. The desired stochiometry for high conductivity is achieved by controlling the temperature of the substrate, and partial pressures of the gases, and the target power and total pressure of the gases in the chamber.

  12. Nanocharacterization of titanium nitride thin films obtained by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Merie, V. V.; Pustan, M. S.; Bîrleanu, C.; Negrea, G.

    2014-08-01

    Titanium nitride thin films are used in applications such as tribological layers for cutting tools, coating of some medical devices (scalpel blades, prosthesis, implants etc.), sensors, electrodes for bioelectronics, microelectronics, diffusion barrier, bio-microelectromechanical systems (Bio-MEMS) and so on. This work is a comparative study concerning the influence of substrate temperature on some mechanical and tribological characteristics of titanium nitride thin films. The researched thin films were obtained by reactive magnetron sputtering method. The experiments employed two kinds of substrates: a steel substrate and a silicon one. The elaboration of titanium nitride thin films was done at two temperatures. First, the obtaining was realized when the substrates were at room temperature, and second, the obtaining was realized when the substrates were previously heated at 250 °C. The elaborated samples were then investigated by atomic force microscopy in order to establish their mechanical and tribological properties. The nanohardness, roughness, friction force are some of the determined characteristics. The results marked out that the substrate which was previously heated at 250 °C led to the obtaining of more adherent titanium nitride thin films than the substrate used at room temperature.

  13. Nanocharacterization of Titanium Nitride Thin Films Obtained by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Merie, Violeta Valentina; Pustan, Marius Sorin; Bîrleanu, Corina; Negrea, Gavril

    2015-05-01

    Titanium nitride thin films are used in applications such as tribological layers for cutting tools, coating of some medical devices (scalpel blades, prosthesis, implants, etc.), sensors, electrodes for bioelectronics, microelectronics, diffusion barrier, bio-micro-electromechanical systems, and so on. This work is a comparative study concerning the influence of substrate temperature on some mechanical and tribological characteristics of titanium nitride thin films. The researched thin films were obtained by the reactive magnetron sputtering method. The experiments employed two kinds of substrates: a steel substrate and a silicon one. The elaboration of titanium nitride thin films was done at two temperatures. First, when the substrates were at room temperature, and second, when the substrates were previously heated at 250°C. The temperature of 250°C was kept constant during the deposition of the films. The samples were then investigated by atomic force microscopy in order to establish their mechanical and tribological properties. The nanohardness, Young's modulus, roughness, and friction force were some of the determined characteristics. The results demonstrated that the substrate which was previously heated at 250°C led to the obtaining of more adherent titanium nitride thin films than the substrate used at room temperature. The preheating of both substrates determined the decrease of thin films roughness. The friction force, nanohardness and Young's modulus of the tested samples increased when the substrates were preheated at 250°C.

  14. Adhesion analysis for chromium nitride thin films deposited by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Rusu, F. M.; Merie, V. V.; Pintea, I. M.; Molea, A.

    2016-08-01

    The thin film industry is continuously growing due to the wide range of applications that require the fabrication of advanced components such as sensors, biological implants, micro-electromechanical devices, optical coatings and so on. The selection regarding the deposition materials, as well as the deposition technology influences the properties of the material and determines the suitability of devices for certain real-world applications. This paper is focused on the adhesion force for several chromium nitride thin films obtained by reactive magnetron sputtering. All chromium nitride thin films were deposited on a silicon substrate, the discharge current and the argon flow being kept constant. The main purpose of the paper is to determine the influence of deposition parameters on the adhesion force. Therefore some of the deposition parameters were varied in order to study their effect on the adhesion force. Experimentally, the values of the adhesion force were determined in multiple points for each sample using the spectroscopy in point mode of the atomic force microscope. The obtained values were used to estimate the surface energy of the CrN thin films based on two existing mathematical models for the adhesion force when considering the contact between two bodies.

  15. Innovative technique for tailoring intrinsic stress in reactively sputtered piezoelectric aluminum nitride films

    SciTech Connect

    Felmetsger, V. V.; Laptev, P. N.; Tanner, S. M.

    2009-05-15

    Novel technical and technological solutions enabling effective stress control in highly textured polycrystalline aluminum nitride (AlN) thin films deposited with ac (40 kHz) reactive sputtering processes are discussed. Residual stress in the AlN films deposited by a dual cathode S-Gun magnetron is well controlled by varying Ar gas pressure, however, since deposition rate and film thickness uniformity depend on gas pressure too, an independent stress control technique has been developed. The technique is based on regulation of the flux of the charged particles from ac plasma discharge to the substrate. In the ac powered S-Gun, a special stress adjustment unit (SAU) is employed for reducing compressive stress in the film by means of redistribution of discharge current between electrodes of the S-Gun leading to controllable suppression of bombardment of the growing film. This technique is complementary to AlN deposition with rf substrate bias which increases ion bombardment and shifts stress in the compressive direction, if required. Using SAU and rf bias functions ensures tailoring intrinsic stress in piezoelectric AlN films for a particular application from high compressive -700 MPa to high tensile +300 MPa and allows the gas pressure to be adjusted independently to fine control the film uniformity. The AlN films deposited on Si substrates and Mo electrodes have strong (002) texture with full width at half maximum ranging from 2 degree sign for 200 nm to 1 degree sign for 2000 nm thick films.

  16. Growth dynamics of reactive-sputtering-deposited AlN films

    SciTech Connect

    Auger, M.A.; Vazquez, L.; Sanchez, O.; Jergel, M.; Cuerno, R.; Castro, M.

    2005-06-15

    We have studied the surface kinetic roughening of AlN films grown on Si(100) substrates by dc reactive sputtering within the framework of the dynamic scaling theory. Films deposited under the same experimental conditions for different growth times were analyzed by atomic force microscopy and x-ray diffraction. The AlN films display a (002) preferred orientation. We have found two growth regimes with a crossover time of 36 min. In the first regime, the growth dynamics is unstable and the films present two types of textured domains, well textured and randomly oriented, respectively. In contrast, in the second regime the films are homogeneous and well textured, leading to a relative stabilization of the surface roughness characterized by a growth exponent {beta}=0.37{+-}0.03. In this regime a superrough scaling behavior is found with the following exponents: (i) Global exponents: roughness exponent {alpha}=1.2{+-}0.2 and {beta}=0.37{+-}0.03 and coarsening exponent 1/z=0.32{+-}0.05; (ii) local exponents: {alpha}{sub loc}=1, {beta}{sub loc}=0.32{+-}0.01. The differences between the growth modes are found to be related to the different main growth mechanisms dominating their growth dynamics: sticking anisotropy and shadowing, respectively.

  17. Structural defect control and photosensitivity in reactively sputtered germanosilicate glass films

    SciTech Connect

    Potter, B.G. Jr.; Simmons-Potter, K.; Warren, W.L.; Ruffner, J.A.

    1997-02-01

    The optical performance of refractive index structures induced in photosensitive (PS) glasses ultimately depends on the index modulation depth attainable. In germanosilicate materials, the photosensitive response is linked to the presence of oxygen-deficient germanium point defect centers. Prior efforts to increase PS in these materials, e.g., hydrogen loading, rely on a chemical reduction of the glass structure to enhance the population of oxygen deficient centers and thus increase the saturated refractive index change. We have previously reported the development of highly photosensitive, as-deposited germanosilicate glass films through reactive atmosphere (O{sub 2}/Ar) sputtering from a Ge/Si alloy target. The present work details our investigation of the effect of substrate temperature during deposition on the material structure and propensity for photosensitivity. Using optical absorption/bleaching, Raman, electron paramagnetic resonance (EPR) and selective charge injection techniques we show that the predominate defect states responsible for the PS response can be varied through substrate temperature control. We find that two regimes of photosensitive behavior can be accessed which exhibit dramatically different uv-bleaching characteristics. Thus, the corresponding dispersion of the refractive index change as well as its magnitude can be controlled using our synthesis technique. Tentative defect models for the photosensitive process in materials deposited at both ambient temperature and at elevated substrate temperatures will be presented.

  18. High-frequency behavior of FeN thin films fabricated by using reactive sputtering

    NASA Astrophysics Data System (ADS)

    Hwang, Tae-Jong; Lee, Joonsik; Kim, Ki Hyeon; Kim, Dong Ho

    2016-08-01

    We used ferromagnetic resonance (FMR) and its relationship with the static magnetic properties to investigate the high-frequency behavior of FeN thin films prepared by using reactive sputtering. The FMR was observed in the frequency range from 2 to 18 GHz in the FeN films fabricated at a proper nitrogen flow rate (NFR). In those FeN thin films, a decrease in the saturation magnetization and a corresponding decrease of the FMR frequency were observed as the NFR was increased during the deposition. The external field dependences of the FMR frequencies fit the Kittel formula well, and the Landé g-factors determined from the fit were found to be very close to the free electron value. The high-field damping parameters were almost insensitive to the NFR. However, the lowfield damping parameters exhibited a high sensitivity to the NFR very similar to the dependence of the hard-axis coercivity on the NFR, suggesting that extrinsic material properties, such as impurities and defect structures, could be important in deciding the low-field damping behavior.

  19. Synthesis and characterization of nanocrystalline Ti(1-x)Al(x)N by reactive magnetron sputtering.

    PubMed

    Jose, Feby; Ramaseshan, R; Dash, S; Dasgupta, Arup; Saroja, S; Tyagi, A K

    2009-09-01

    Ti(1-x)Al(x)N metastable films were synthesized by reactive magnetron co-sputtering with different Ti to Al ratios. XRD studies showed that as-deposited films were crystalline for concentrations of Al (35, 40, 55 and 64%) and become amorphous at 81% Al. These films were annealed at 1073 K to study the phase separation. Films up to 55% Al did not show any phase separation after annealing. But films with 64% Al splits into c-TiAIN and c-AIN, whereas films with 81% Al split into cubic-TiN and hex-AIN. Distribution of crystallites and their size were analyzed by TEM. High density of crystallites with dimensions between 3-11 nm was dispersed in amorphous matrix for 64% Al films. Nanoindentation technique was used to determine the mechanical properties of these films without substrate effect. Maximum hardness obtained for as deposited and annealed films (64% Al) were 35 GPa and 38 GPa, respectively.

  20. Synthesis and characterization of petal type CZTS by stacked layer reactive sputtering

    NASA Astrophysics Data System (ADS)

    Singh, Om Pal; Parmar, R.; Gour, K. S.; Dalai, M. K.; Tawale, Jai; Singh, S. P.; Singh, Vidya Nand

    2015-12-01

    Here we present a method to grow the petal type structure of CZTS thin film on soda lime glass substrate using the stacked layer reactive sputtering and post-depostion annealing in N2 atmosphere. Optical bandgap of the petal type structure of CZTS was determined using UV-VIS spectroscopy and the value was 1.5 eV. In XRD analysis, (112) plane having highest intensity and other supporting planes with low intensity peaks corresponding to (200), (220) and (312) revealed the presence of CZTS phase. It was further confirmed by the Raman analysis, where the Raman peaks at 288 cm-1, 335 cm-1 and 353 cm-1 revealed the presence of CZTS phase. Petal type growth was observed in the scanning electron microscopy analysis. Elemental analysis was done by the EDAX. In EDAX analysis, It is observed that sample was Sn rich which may be responsible for petal type growth. Petal type growth of CZTS may be helpful in increasing the performance of the CZTS based thin film solar cell by phenomena of light scattering and enhanced surface area.

  1. Synthesis of copper nitride films doped with Fe, Co, or Ni by reactive magnetron sputtering

    SciTech Connect

    Yang, Jianbo; Huang, Saijia; Wang, Zhijiao; Hou, Yuxuan; Shi, Yuyu; Zhang, Jian; Yang, Jianping Li, Xing'ao

    2014-09-01

    Copper nitride (Cu{sub 3}N) and Fe-, Co-, and Ni-doped Cu{sub 3}N films were prepared by reactive magnetron sputtering. The films were deposited on silicon substrates at room temperature using pure Cu target and metal chips. The molar ratio of Cu to N atoms in the as-prepared Cu{sub 3}N film was 2.7:1, which is comparable with the stoichiometry ratio 3:1. X-ray diffraction measurements showed that the films were composed of Cu{sub 3}N crystallites with anti-ReO{sub 3} structure and adopted different preferred orientations. The reflectance of the four samples decreased in the wavelength range of 400–830 nm, but increased rapidly within wavelength range of 830–1200 nm. Compared with the Cu{sub 3}N films, the resistivity of the doped Cu{sub 3}N films decreased by three orders of magnitude. These changes have great application potential in optical and electrical devices based on Cu{sub 3}N films.

  2. Time-resolved in situ investigations of reactive sputtering processes by grazing incidence X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lützenkirchen-Hecht, Dirk; Frahm, Ronald

    2006-09-01

    We have applied the time-resolved grazing incidence X-ray absorption fine structure technique to study in situ the atomic short range order and the electronic structure of reactively sputter deposited thin films. Results obtained during the reactive deposition of amorphous Ta-pentoxide thin films deposited in oxygen containing atmospheres will be presented. A new calculation scheme for a detailed reflection mode EXAFS data analysis giving bond distances, coordination numbers and Debye-Waller factors is presented. The atomic short range structure of the amorphous Ta 2O 5 thin films is compared to that of crystalline β-Ta 2O 5.

  3. Process stabilization by peak current regulation in reactive high-power impulse magnetron sputtering of hafnium nitride

    NASA Astrophysics Data System (ADS)

    Shimizu, T.; Villamayor, M.; Lundin, D.; Helmersson, U.

    2016-02-01

    A simple and cost effective approach to stabilize the sputtering process in the transition zone during reactive high-power impulse magnetron sputtering (HiPIMS) is proposed. The method is based on real-time monitoring and control of the discharge current waveforms. To stabilize the process conditions at a given set point, a feedback control system was implemented that automatically regulates the pulse frequency, and thereby the average sputtering power, to maintain a constant maximum discharge current. In the present study, the variation of the pulse current waveforms over a wide range of reactive gas flows and pulse frequencies during a reactive HiPIMS process of Hf-N in an Ar-N2 atmosphere illustrates that the discharge current waveform is a an excellent indicator of the process conditions. Activating the reactive HiPIMS peak current regulation, stable process conditions were maintained when varying the N2 flow from 2.1 to 3.5 sccm by an automatic adjustment of the pulse frequency from 600 Hz to 1150 Hz and consequently an increase of the average power from 110 to 270 W. Hf-N films deposited using peak current regulation exhibited a stable stoichiometry, a nearly constant power-normalized deposition rate, and a polycrystalline cubic phase Hf-N with (1 1 1)-preferred orientation over the entire reactive gas flow range investigated. The physical reasons for the change in the current pulse waveform for different process conditions are discussed in some detail.

  4. Low-temperature growth of gallium nitride films by inductively coupled-plasma-enhanced reactive magnetron sputtering

    SciTech Connect

    Ni, Chih-Jui; Chau-Nan Hong, Franklin

    2014-05-15

    Gallium nitride (GaN) films were grown on sapphire substrate by reactive magnetron sputtering. Inductively coupled-plasma (ICP) source was installed between the substrate holder and the sputtering target to increase the plasma density and the degree of ionization of nitrogen gas. Liquid Ga and Ar/N{sub 2} were used as the sputtering target and sputtering gases, respectively. X-ray diffraction measurements confirmed that the authors could grow high quality GaN crystallites at 500 °C. However, the crystalline GaN (0002) peak remained even by lowering the growth temperature down to 300 °C. The N:Ga ratio of the film grown at 500 °C was almost 1:1, and the nitrogen composition became higher toward the 1:1 N:Ga ratio with increasing the growth temperature. The high degree of ionization induced by ICP source was essential to the growth of high crystalline quality GaN films.

  5. Limits of carrier mobility in Sb-doped SnO{sub 2} conducting films deposited by reactive sputtering

    SciTech Connect

    Bissig, B. Jäger, T.; Tiwari, A. N.; Romanyuk, Y. E.; Ding, L.

    2015-06-01

    Electron transport in Sb-doped SnO{sub 2} (ATO) films is studied to unveil the limited carrier mobility observed in sputtered films as compared to other deposition methods. Transparent and conductive ATO layers are deposited from metallic tin targets alloyed with antimony in oxygen atmosphere optimized for reactive sputtering. The carrier mobility decreases from 24 cm{sup 2} V{sup −1} s{sup −1} to 6 cm{sup 2} V{sup −1} s{sup −1} when increasing the doping level from 0 to 7 at. %, and the lowest resistivity of 1.8 × 10{sup −3} Ω cm corresponding to the mobility of 12 cm{sup 2} V{sup −1} s{sup −1} which is obtained for the 3 at. % Sb-doped ATO. Temperature-dependent Hall effect measurements and near-infrared reflectance measurements reveal that the carrier mobility in sputtered ATO is limited by ingrain scattering. In contrast, the mobility of unintentionally doped SnO{sub 2} films is determined mostly by the grain boundary scattering. Both limitations should arise from the sputtering process itself, which suffers from the high-energy-ion bombardment and yields polycrystalline films with small grain size.

  6. Photocatalytic degradation of Reactive Black 5 and Malachite Green with ZnO and lanthanum doped nanoparticles

    NASA Astrophysics Data System (ADS)

    Kaneva, N.; Bojinova, A.; Papazova, K.

    2016-02-01

    Here we report the preparation of ZnO particles with different concentrations of La3+ doping (0, 0.5 and 1 wt%) via sol-gel method. The nanoparticles are synthesized directly from Zn(CH3COO)2.2H2O in the presence of 1-propanol and triethylamine at 80°C. The conditions are optimized to obtain particles of uniform size, easy to isolate and purify. The nanoparticles are characterized by SEM, XRD and UV-Vis analysis. The photocatalytic properties of pure and La-doped ZnO are studied in the photobleaching of Malachite Green (MG) and Reactive Black 5 (RB5) dyes in aqueous solutions upon UV illumination. It is observed that the rate constant increases with the La loading up to 1 wt%. The doping helps to achieve complete mineralization of MG within a short irradiation time. 1 wt% La-doped ZnO nanoparticles show highest photocatalytic activity. The La3+ doped ZnO particles degrade faster RB5 than MG. The reason is weaker N=N bond in comparison with the C-C bond between the central carbon atom and N,N-dimethylaminobenzyl in MG. The as-prepared ZnO particles can find practical application in photocatalytic purification of textile wastewaters.

  7. Bioactivity response of Ta1-xOx coatings deposited by reactive DC magnetron sputtering.

    PubMed

    Almeida Alves, C F; Cavaleiro, A; Carvalho, S

    2016-01-01

    The use of dental implants is sometimes accompanied by failure due to periimplantitis disease and subsequently poor esthetics when soft-hard tissue margin recedes. As a consequence, further research is needed for developing new bioactive surfaces able to enhance the osseous growth. Tantalum (Ta) is a promising material for dental implants since, comparing with titanium (Ti), it is bioactive and has an interesting chemistry which promotes the osseointegration. Another promising approach for implantology is the development of implants with oxidized surfaces since bone progenitor cells interact with the oxide layer forming a diffusion zone due to its ability to bind with calcium which promotes a stronger bond. In the present report Ta-based coatings were deposited by reactive DC magnetron sputtering onto Ti CP substrates in an Ar+O2 atmosphere. In order to assess the osteoconductive response of the studied materials, contact angle and in vitro tests of the samples immersed in Simulated Body Fluid (SBF) were performed. Structural results showed that oxide phases where achieved with larger amounts of oxygen (70 at.% O). More compact and smooth coatings were deposited by increasing the oxygen content. The as-deposited Ta coating presented the most hydrophobic character (100°); with increasing oxygen amount contact angles progressively diminished, down to the lowest measured value, 63°. The higher wettability is also accompanied by an increase on the surface energy. Bioactivity tests demonstrated that highest O-content coating, in good agreement with wettability and surface energy values, showed an increased affinity for apatite adhesion, with higher Ca/P ratio formation, when compared to the bare Ti substrates.

  8. Studies on optoelectronic properties of DC reactive magnetron sputtered CdTe thin films

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Hymavathi, B.; Rao, T. Subba

    2014-01-01

    Cadmium telluride continues to be a leading candidate for the development of cost effective photovoltaics for terrestrial applications. In the present work two individual metallic targets of Cd and Te were used for the deposition of CdTe thin films on mica substrates from room temperature to 300 °C by DC reactive magnetron sputtering method. XRD patterns of CdTe thin films deposited on mica substrates exhibit peaks at 2θ = 27.7°, 46.1° and 54.6°, which corresponds to reflection on (1 1 1), (2 2 0) and (3 1 1) planes of CdTe cubic structure. The intensities of XRD patterns increases with the increase of substrate temperature upto 150 °C and then it decreases at higher substrate temperatures. The conductivity of CdTe thin films measured from four probe method increases with the increase of substrate temperature. The activation energies (ΔE) are found to be decrease with the increase of substrate temperature. The optical transmittance spectra of CdTe thin films deposited on mica have a clear interference pattern in the longer wavelength region. The films have good transparency (T > 85 %) exhibiting interference pattern in the spectral region between 1200 - 2500 nm. The optical band gap of CdTe thin films are found to be in the range of 1.48 - 1.57. The refractive index, n decreases with the increase of wavelength, λ. The value of n and k increases with the increase of substrate temperature.

  9. Studies on optoelectronic properties of DC reactive magnetron sputtered CdTe thin films

    SciTech Connect

    Kumar, B. Rajesh; Hymavathi, B.; Rao, T. Subba

    2014-01-28

    Cadmium telluride continues to be a leading candidate for the development of cost effective photovoltaics for terrestrial applications. In the present work two individual metallic targets of Cd and Te were used for the deposition of CdTe thin films on mica substrates from room temperature to 300 °C by DC reactive magnetron sputtering method. XRD patterns of CdTe thin films deposited on mica substrates exhibit peaks at 2θ = 27.7°, 46.1° and 54.6°, which corresponds to reflection on (1 1 1), (2 2 0) and (3 1 1) planes of CdTe cubic structure. The intensities of XRD patterns increases with the increase of substrate temperature upto 150 °C and then it decreases at higher substrate temperatures. The conductivity of CdTe thin films measured from four probe method increases with the increase of substrate temperature. The activation energies (ΔE) are found to be decrease with the increase of substrate temperature. The optical transmittance spectra of CdTe thin films deposited on mica have a clear interference pattern in the longer wavelength region. The films have good transparency (T > 85 %) exhibiting interference pattern in the spectral region between 1200 – 2500 nm. The optical band gap of CdTe thin films are found to be in the range of 1.48 – 1.57. The refractive index, n decreases with the increase of wavelength, λ. The value of n and k increases with the increase of substrate temperature.

  10. Influence of the N2 gas flow on optical and structural properties of reactively sputtered ZrN films

    NASA Astrophysics Data System (ADS)

    Schleussner, S.; Törndahl, T.; Edoff, M.

    2008-03-01

    We present optical and structural properties of reactively sputtered zirconium nitride (ZrN) films for application as back reflectors in Cu(In,Ga)Se2 solar cells with sub-micrometer absorbers. In this study, ZrN films were deposited by reactive DC sputtering on blank, Mo-coated and Zr-coated soda-lime glass at two different process pressures and various ratios of nitrogen mixed in the argon working gas. When characterised by x-ray diffraction (XRD), the majority of the films were found to consist of single-phase cubic ZrN. All peaks corresponding to the ZrN phase were present in the diffractograms with intensities similar to those obtained from bulk ZrN, indicating that the films were randomly oriented. No significant differences were found between films grown on different substrate types. Films sputtered with lower nitrogen partial pressures displayed a spectral optical reflectance similar to metallic Zr, while films prepared with higher N2 flows showed the pronounced Drude-like reflectance characteristic of the nitride. The best ZrN films were achieved with a process pressure of 2.5 mTorr and a N2/(Ar+N2) flow ratio of 26.5%. At a wavelength of 800 nm the reflectance of these reached 85%, as compared to a typical value of 58% in the case of molybdenum.

  11. Preparation and Characterization of Ba(ZrxTi1-x)O3 Thin Films Using Reactive Sputtering Method

    NASA Astrophysics Data System (ADS)

    Kim, Jin Woong; Osumi, Tsuyoshi; Mastuoka, Masashi; Tai, Takeshi; Nishide, Masamichi; Funakubo, Hiroshi; Shima, Hiromi; Nishida, Ken; Yamamoto, Takashi

    2012-09-01

    Ba(ZrxTi1-x)O3 (BZT) thin films with different Zr contents were deposited on (100) MgO and (100) Pt/(100) MgO substrates by RF-magnetron reactive sputtering using metal targets. The BZT (0 < x < 0.89) thin films had a single perovskite phase with only (001)/(100) orientation. In all cases, the ratio of Ba/Ti was stoichiometric according to X-ray fluorescence spectrometry (WDX) measurement. Atomic force microscopy (AFM) study proved that BZT films possess a dense microstructure without cracks or voids. The grain size was found to decrease with increasing of Zr content. The effect of Zr content on the dielectric constant and leakage current was studied. BZT thin films showed ferroelectric-to-paraelectric properties with increasing Zr content and excellent leakage properties according to measurements of electrical properties. These results indicated that we succeeded in depositing high-quality and low-sputter-damage BZT thin films by reactive sputtering using metal targets.

  12. Measurements of sputtered neutrals and ions and investigation of their roles on the plasma properties during rf magnetron sputtering of Zn and ZnO targets

    SciTech Connect

    Maaloul, L.; Stafford, L.

    2013-11-15

    Langmuir probe and optical absorption spectroscopy measurements were used to determine the line-integrated electron density, electron temperature, and number density of Ar atoms in metastable {sup 3}P{sub 2} and {sup 3}P{sub 0} levels in a 5 mTorr, rf magnetron sputtering plasmas used for the deposition of ZnO-based thin films. While the average electron energy and density of Ar atoms in {sup 3}P{sub 2} and {sup 3}P{sub 0} excited states were fairly independent of self-bias voltage, the Ar {sup 3}P{sub 2}-to-electron number density ratio decreased by approximately a factor of 5 when going from −115 V to −300 V. This decrease was correlated to an increase by about one order of magnitude of the number density of sputtered Zn atoms determined by absolute actinometry measurements on Zn I using either Ar or Xe as the actinometer gas. These results were also found to be in excellent agreement with the predictions of a global model accounting for Penning ionization of sputtered Zn particles. The importance of the latter reactions was further confirmed by plasma sampling mass spectrometry showing a double peak structure for Zn ions: a low-energy component ascribed to thermalized ions created in the gas phase (by direct electron impact and by Penning ionization) and a high-energy tail due to ions ejected from the target and reaching quasi-collisionlessly the substrate surface.

  13. Influence of in-situ annealing ambient on p-type conduction in dual ion beam sputtered Sb-doped ZnO thin films

    SciTech Connect

    Pandey, Sushil Kumar; Kumar Pandey, Saurabh; Awasthi, Vishnu; Mukherjee, Shaibal; Gupta, M.; Deshpande, U. P.

    2013-08-12

    Sb-doped ZnO (SZO) films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system and subsequently annealed in-situ in vacuum and in various proportions of O{sub 2}/(O{sub 2} + N{sub 2})% from 0% (N{sub 2}) to 100% (O{sub 2}). Hall measurements established all SZO films were p-type, as was also confirmed by typical diode-like rectifying current-voltage characteristics from p-ZnO/n-ZnO homojunction. SZO films annealed in O{sub 2} ambient exhibited higher hole concentration as compared with films annealed in vacuum or N{sub 2} ambient. X-ray photoelectron spectroscopic analysis confirmed that Sb{sup 5+} states were more preferable in comparison to Sb{sup 3+} states for acceptor-like Sb{sub Zn}-2V{sub Zn} complex formation in SZO films.

  14. Enhanced electrical and noise properties of nanocomposite vanadium oxide thin films by reactive pulsed-dc magnetron sputtering

    SciTech Connect

    Basantani, H. A.; Kozlowski, S.; Lee, Myung-Yoon; Li, J.; Dickey, E. C.; Jackson, T. N.; Bharadwaja, S. S. N.; Horn, M.

    2012-06-25

    Thin films of VO{sub x} (1.3 {<=} x {<=} 2) were deposited by reactive pulsed-dc magnetron sputtering of a vanadium metal target while RF-biasing the substrate. Rutherford back scattering, glancing angle x-ray, and cross-sectional transmission electron microscopy measurements revealed the formation of nanocolumns with nanotwins within VO{sub x} samples. The resistivity of nanotwinned VO{sub x} films ranged from 4 m{Omega}{center_dot}cm to 0.6 {Omega}{center_dot}cm and corresponding temperature coefficient of resistance between -0.1% and -2.6% per K, respectively. The 1/f electrical noise was analyzed in these VO{sub x} samples using the Hooge-Vandamme relation. These VO{sub x} films are comparable or surpass commercial VO{sub x} films deposited by ion beam sputtering.

  15. Low-temperature-deposited insulating films of silicon nitride by reactive sputtering and plasma-enhanced CVD: Comparison of characteristics

    NASA Astrophysics Data System (ADS)

    Sato, Masaru; Takeyama, Mayumi B.; Nakata, Yoshihiro; Kobayashi, Yasushi; Nakamura, Tomoji; Noya, Atsushi

    2016-04-01

    The characteristics of SiN x films deposited by reactive sputtering and plasma-enhanced chemical vapor deposition (PECVD) are examined to obtain high-density films at low deposition temperatures. PECVD SiN x films deposited at 200 °C show low densities of 2.14-2.20 g/cm3 regardless of their composition, while their refractive index varies depending on their composition. PECVD requires the substrate temperature to obtain high-density films, because a possible cause of low-density films is the amount of Si-H bond, rather than that of N-H bond, in the films originating from hydrogen incorporated by the insufficient decomposition of SiH4 molecules at low temperatures. The sputtered SiN x films with high density are obtained at a temperature lower than 200 °C and considered a promising candidate for insulating films at low process temperatures.

  16. Silicon oxynitride films deposited by reactive high power impulse magnetron sputtering using nitrous oxide as a single-source precursor

    SciTech Connect

    Hänninen, Tuomas Schmidt, Susann; Jensen, Jens; Hultman, Lars; Högberg, Hans

    2015-09-15

    Silicon oxynitride thin films were synthesized by reactive high power impulse magnetron sputtering of silicon in argon/nitrous oxide plasmas. Nitrous oxide was employed as a single-source precursor supplying oxygen and nitrogen for the film growth. The films were characterized by elastic recoil detection analysis, x-ray photoelectron spectroscopy, x-ray diffraction, x-ray reflectivity, scanning electron microscopy, and spectroscopic ellipsometry. Results show that the films are silicon rich, amorphous, and exhibit a random chemical bonding structure. The optical properties with the refractive index and the extinction coefficient correlate with the film elemental composition, showing decreasing values with increasing film oxygen and nitrogen content. The total percentage of oxygen and nitrogen in the films is controlled by adjusting the gas flow ratio in the deposition processes. Furthermore, it is shown that the film oxygen-to-nitrogen ratio can be tailored by the high power impulse magnetron sputtering-specific parameters pulse frequency and energy per pulse.

  17. Vapor-liquid-solid growth of GaN nanowires by reactive sputtering of GaAs

    NASA Astrophysics Data System (ADS)

    Mohanta, P.; Chaturvedi, P.; Major, S. S.; Srinivasa, R. S.

    2013-02-01

    Uniformly distributed nanosized Au-Ga alloy particles were formed on ultrathin Au coated quartz substrate by sputtering of GaAs with argon at 700 °C. Subsequent deposition of GaN by reactive sputtering of GaAs in 100 % nitrogen results in the growth of GaN nanowires. X-ray diffraction analysis confirmed the formation of hexagonal GaN. Field emission gun scanning electron microscopy studies show that the nanowires are of average length 400±50 nm and average diameter 40±5 nm. The presence of spherical Au-Ga nanoparticles of diameter ˜ 50 nm at the top of the nanowires suggests that the growth takes place by vapor-liquid-solid mechanism.

  18. In situ plasma sputtering synthesis of ZnO nanorods-Ag nanoparticles hybrids and their application in non-enzymatic hydrogen peroxide sensing.

    PubMed

    Zhang, Dan; Zhang, Yuxia; Yang, Chi; Ge, Cunwang; Wang, Yuanhong; Wang, Hao; Liu, Hongying

    2015-08-21

    In this paper, ZnO nanorods-Ag nanoparticles hybrids were first synthesized via a facile, rapid, and in situ plasma sputtering method without using any silver precursor. The obtained materials were then characterized by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetry. Based on the electrochemical catalytic properties of the obtained nanohybrids, a non-enzymatic hydrogen peroxide biosensor was constructed by immobilizing the obtained ZnO nanorods-Ag nanoparticles hybrids on the surface of a glassy carbon electrode. Under optimal conditions, the resulting biosensor displayed a good response for H2O2 with a linear range of 0.2 to 12.8 mM, and a detection limit of 7.8 μM at a signal-to-noise ratio of 3. In addition, it exhibited excellent anti-interference ability and fast response. The current work provides a feasible platform to fabricate a variety of non-enzymatic biosensors.

  19. Effect of Sn Doping on the Properties of Nano-Structured ZnO Thin Films Deposited by Co-Sputtering Technique.

    PubMed

    Islam, M A; Rahman, K S; Haque, F; Khan, N A; Akhtaruzzaman, M; Alam, M M; Ruslan, H; Sopian, K; Amin, N

    2015-11-01

    In this study, tin doped zinc oxide (ZnO:Sn) nano-structured thin films were successfully deposited by co-sputtering of ZnO and Sn on top of glass substrate. The effect of Sn doping on the microstructure, phase, morphology, optical and electrical properties of the films were extensively investigated by means of XRD, EDX, SEM, AFM, Hall Effect measurement, and UV-Vis spectrometry. The results showed that the undoped ZnO film exhibited preferred orientation along the c-axis of the hexagonal wurtzite structure. With increase of Sn doping, the peak position of the (002) plane was shifted to the higher 20 values, and ultimately changed to amorphous structure. The absorption edge was shifted to blue region which confirmed the excitonic quantum confinement effect in the films. Consequently, improved surface morphology with optical bandgap, reduced average particle size, reduced resistivity, enhanced Hall mobility and carrier concentration were observed in the doped films after vacuum annealing. Among all of the as-deposited and annealed ZnO:Sn films investigated in this study, annealed film doped with 8 at.% of Sn concentration exhibited the best properties with a bandgap of 3.84 eV, RMS roughness of 2.51 nm, resistivity of 2.36 ohm-cm, and Hall mobility of 83 cm2 V(-1) s(-1).

  20. Effect of Sn Doping on the Properties of Nano-Structured ZnO Thin Films Deposited by Co-Sputtering Technique.

    PubMed

    Islam, M A; Rahman, K S; Haque, F; Khan, N A; Akhtaruzzaman, M; Alam, M M; Ruslan, H; Sopian, K; Amin, N

    2015-11-01

    In this study, tin doped zinc oxide (ZnO:Sn) nano-structured thin films were successfully deposited by co-sputtering of ZnO and Sn on top of glass substrate. The effect of Sn doping on the microstructure, phase, morphology, optical and electrical properties of the films were extensively investigated by means of XRD, EDX, SEM, AFM, Hall Effect measurement, and UV-Vis spectrometry. The results showed that the undoped ZnO film exhibited preferred orientation along the c-axis of the hexagonal wurtzite structure. With increase of Sn doping, the peak position of the (002) plane was shifted to the higher 20 values, and ultimately changed to amorphous structure. The absorption edge was shifted to blue region which confirmed the excitonic quantum confinement effect in the films. Consequently, improved surface morphology with optical bandgap, reduced average particle size, reduced resistivity, enhanced Hall mobility and carrier concentration were observed in the doped films after vacuum annealing. Among all of the as-deposited and annealed ZnO:Sn films investigated in this study, annealed film doped with 8 at.% of Sn concentration exhibited the best properties with a bandgap of 3.84 eV, RMS roughness of 2.51 nm, resistivity of 2.36 ohm-cm, and Hall mobility of 83 cm2 V(-1) s(-1). PMID:26726665

  1. Silver Nanowires Binding with Sputtered ZnO to Fabricate Highly Conductive and Thermally Stable Transparent Electrode for Solar Cell Applications.

    PubMed

    Singh, Manjeet; Rana, Tanka R; Kim, SeongYeon; Kim, Kihwan; Yun, Jae Ho; Kim, JunHo

    2016-05-25

    Silver nanowire (AgNW) film has been demonstrated as excellent and low cost transparent electrode in organic solar cells as an alternative to replace scarce and expensive indium tin oxide (ITO). However, the low contact area and weak adhesion with low-lying surface as well as junction resistance between nanowires have limited the applications of AgNW film to thin film solar cells. To resolve this problem, we fabricated AgNW film as transparent conductive electrode (TCE) by binding with a thin layer of sputtered ZnO (40 nm) which not only increased contact area with low-lying surface in thin film solar cell but also improved conductivity by connecting AgNWs at the junction. The TCE thus fabricated exhibited transparency and sheet resistance of 92% and 20Ω/□, respectively. Conductive atomic force microscopy (C-AFM) study revealed the enhancement of current collection vertically and laterally through AgNWs after coating with ZnO thin film. The CuInGaSe2 solar cell with TCE of our AgNW(ZnO) demonstrated the maximum power conversion efficiency of 13.5% with improved parameters in comparison to solar cell fabricated with conventional ITO as TCE. PMID:27149372

  2. In situ plasma sputtering synthesis of ZnO nanorods-Ag nanoparticles hybrids and their application in non-enzymatic hydrogen peroxide sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Zhang, Yuxia; Yang, Chi; Ge, Cunwang; Wang, Yuanhong; Wang, Hao; Liu, Hongying

    2015-08-01

    In this paper, ZnO nanorods-Ag nanoparticles hybrids were first synthesized via a facile, rapid, and in situ plasma sputtering method without using any silver precursor. The obtained materials were then characterized by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetry. Based on the electrochemical catalytic properties of the obtained nanohybrids, a non-enzymatic hydrogen peroxide biosensor was constructed by immobilizing the obtained ZnO nanorods-Ag nanoparticles hybrids on the surface of a glassy carbon electrode. Under optimal conditions, the resulting biosensor displayed a good response for H2O2 with a linear range of 0.2 to 12.8 mM, and a detection limit of 7.8 μM at a signal-to-noise ratio of 3. In addition, it exhibited excellent anti-interference ability and fast response. The current work provides a feasible platform to fabricate a variety of non-enzymatic biosensors.

  3. Silver Nanowires Binding with Sputtered ZnO to Fabricate Highly Conductive and Thermally Stable Transparent Electrode for Solar Cell Applications.

    PubMed

    Singh, Manjeet; Rana, Tanka R; Kim, SeongYeon; Kim, Kihwan; Yun, Jae Ho; Kim, JunHo

    2016-05-25

    Silver nanowire (AgNW) film has been demonstrated as excellent and low cost transparent electrode in organic solar cells as an alternative to replace scarce and expensive indium tin oxide (ITO). However, the low contact area and weak adhesion with low-lying surface as well as junction resistance between nanowires have limited the applications of AgNW film to thin film solar cells. To resolve this problem, we fabricated AgNW film as transparent conductive electrode (TCE) by binding with a thin layer of sputtered ZnO (40 nm) which not only increased contact area with low-lying surface in thin film solar cell but also improved conductivity by connecting AgNWs at the junction. The TCE thus fabricated exhibited transparency and sheet resistance of 92% and 20Ω/□, respectively. Conductive atomic force microscopy (C-AFM) study revealed the enhancement of current collection vertically and laterally through AgNWs after coating with ZnO thin film. The CuInGaSe2 solar cell with TCE of our AgNW(ZnO) demonstrated the maximum power conversion efficiency of 13.5% with improved parameters in comparison to solar cell fabricated with conventional ITO as TCE.

  4. Optimization of process parameters for the electrical properties in Ga-doped ZnO thin films prepared by r.f. magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zhu, D. L.; Wang, Q.; Han, S.; Cao, P. J.; Liu, W. J.; Jia, F.; Zeng, Y. X.; Ma, X. C.; Lu, Y. M.

    2014-04-01

    Ga-doped ZnO (GZO) transparent conductive thin films have been deposited on quartz substrates by r.f. magnetron sputtering. The optimization of four process parameters (i.e., vacuum annealing temperature, r.f. power, sputtering pressure, and Ar flow rate) based on Taguchi method has been systematically studied in order to obtain the minimum resistivity. Compared to the optimal parameter set selected from orthogonal array by Taguchi method, the optimal prediction design can receive an improvement of 22.3% in electrical resistivity, and the corresponding resistivity is 8.08 × 10-4 Ω cm. The analysis of variance shows that vacuum annealing temperature is the most significant influencing parameter on the electrical properties in GZO films. X-ray photoelectron spectroscopy and photoluminescence results exhibit that the enhancement in electrical conductivity after vacuum annealing is ascribed to the variation of the chemical states of oxygen in GZO films. With the increase in annealing temperature, the content of absorbed oxygen and interstitial oxygen as acceptors will decrease.

  5. Thermal conductivity of nitride films of Ti, Cr, and W deposited by reactive magnetron sputtering

    SciTech Connect

    Jagannadham, Kasichainula

    2015-05-15

    Nitride films of Ti, Cr, and W were deposited using reactive magnetron sputtering from metal targets in argon and nitrogen plasma. TiN films with (200) orientation were achieved on silicon (100) at the substrate temperature of 500 and 600 °C. The films were polycrystalline at lower temperature. An amorphous interface layer was observed between the TiN film and Si wafer deposited at 600 °C. TiN film deposited at 600 °C showed the nitrogen to Ti ratio to be near unity, but films deposited at lower temperature were nitrogen deficient. CrN film with (200) orientation and good stoichiometry was achieved at 600 °C on Si(111) wafer but the film deposited at 500 °C showed cubic CrN and hexagonal Cr{sub 2}N phases with smaller grain size and amorphous back ground in the x-ray diffraction pattern. An amorphous interface layer was not observed in the cubic CrN film on Si(111) deposited at 600 °C. Nitride film of tungsten deposited at 600 °C on Si(100) wafer was nitrogen deficient, contained both cubic W{sub 2}N and hexagonal WN phases with smaller grain size. Nitride films of tungsten deposited at 500 °C were nonstoichiometric and contained cubic W{sub 2}N and unreacted W phases. There was no amorphous phase formed along the interface for the tungsten nitride film deposited at 600 °C on the Si wafer. Thermal conductivity and interface thermal conductance of all the nitride films of Ti, Cr, and W were determined by transient thermoreflectance technique. The thermal conductivity of the films as function of deposition temperature, microstructure, nitrogen stoichiometry and amorphous interaction layer at the interface was determined. Tungsten nitride film containing both cubic and hexagonal phases was found to exhibit much higher thermal conductivity and interface thermal conductance. The amorphous interface layer was found to reduce effective thermal conductivity of TiN and CrN films.

  6. Electrical and optical properties of Ta-Si-N thin films deposited by reactive magnetron sputtering

    SciTech Connect

    Oezer, D.; Sanjines, R.; Ramirez, G.; Rodil, S. E.

    2012-12-01

    The electrical and optical properties of Ta{sub x}Si{sub y}N{sub z} thin films deposited by reactive magnetron sputtering from individual Ta and Si targets were studied in order to investigate the effects of nitrogen and silicon contents on both properties and their correlation to the film microstructure. Three sets of fcc-Ta{sub x}Si{sub y}N{sub z} thin films were prepared: sub-stoichiometric Ta{sub x}Si{sub y}N{sub 0.44}, nearly stoichiometric Ta{sub x}Si{sub y}N{sub 0.5}, and over-stoichiometric Ta{sub x}Si{sub y}N{sub 0.56}. The optical properties were investigated by near-normal-incidence reflectivity and ellipsometric measurements in the optical energy range from 0.375 eV to 6.8 eV, while the d.c. electrical resistivity was measured in the van der Pauw configuration from 20 K to 300 K. The optical and electrical measurements were interpreted using the standard Drude-Lorentz model and the so-called grain boundary scattering model, respectively. The electronic properties were closely correlated with the compositional and structural modifications of the Ta{sub x}Si{sub y}N{sub z} films due to variations in the stoichiometry of the fcc-TaN{sub z} system and the addition of Si atoms. According to the nitrogen and silicon contents, fcc-Ta{sub x}Si{sub y}N{sub z} films can exhibit room temperature resistivity values ranging from 10{sup 2} {mu}{Omega} cm to about 6 Multiplication-Sign 10{sup 4} {mu}{Omega} cm. The interpretation of the experimental temperature-dependent resistivity data within the Grain Boundary Scattering model, combined with the results from optical investigations, showed that the mean electron transmission probability G and the free carriers concentration, N, are the main parameters that control the transport properties of these films. The results indicated that the correlation between electrical and optical measurements with the chemical composition and the nanostructure of the Ta{sub x}Si{sub y}N{sub z} thin films provides a pertinent and

  7. Microstructure and tribological properties of NbN-Ag composite films by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Ju, Hongbo; Xu, Junhua

    2015-11-01

    Recently, the chameleon thin films were developed with the purpose of adjusting their chemistry at self-mating interfaces in response to environmental changes at a wide temperature range. However, very few studies have focused on what state the lubricious noble metal exists in the films and the tribological properties at room temperature (RT). Composite NbN-Ag films with various Ag content (Ag/(Nb + Ag)) were deposited using reactive magnetron sputtering to investigate the crystal structure, mechanical and tribological properties. A combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analyses showed that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc silver coexisted in NbN-Ag films. The incorporation of soft Ag into NbN matrix led to the hardness decrease from 29.6 GPa at 0 at.% Ag to 11.3 GPa at 19.9 at.% Ag. Tribological properties of NbN-Ag films performed using dry pin-on-disc wear tests against Al2O3 depended on Ag content to a large extent. The average friction coefficient and wear rate of NbN-Ag films decreased as Ag content increased from 4.0 to 9.2 at.%. With a further increase of Ag content, the average friction coefficient further decreased, while the wear rate increased gradually. The optimal Ag content was found to be 9.2-13.5 at.%, which showed low average friction coefficient values of 0.46-0.40 and wear rate values of 1.1 × 10-8 to 1.7 × 10-8 mm3/(mm N). 3D Profiler and Raman spectroscopy measurements revealed that the lubricant tribo-film AgNbO3 detected on the surface of the wear tracks could lead to the friction coefficient curve stay constant and decrease the average friction coefficients. The decrease of wear rate was mainly attributed to the lubricant tribo-film AgNbO3 as Ag content increased from 4.0 to 9.2 at.%; with a further increase in Ag content, the wear rate increased with increasing Ag content in NbN-Ag films because a

  8. Structural properties of reactively sputtered W-Si-N thin films

    SciTech Connect

    Vomiero, A.; Boscolo Marchi, E.; Quaranta, A.; Della Mea, G.; Brusa, R. S.; Mariotto, G.; Felisari, L.; Frabboni, S.; Tonini, R.; Ottaviani, G.; Mattei, G.; Scandurra, A.; Puglisi, O.

    2007-08-01

    Tungsten-silicon-nitrogen, W-Si-N, ternary thin films have been reactively sputter deposited from W{sub 5}Si{sub 3} and WSi{sub 2} targets using several nitrogen partial pressures. The films have been thermal annealed in the 600-1000 deg. C temperature range and a wide region of the W-Si-N ternary phase diagram has been explored by changing the N{sub 2}/Ar ratio during the deposition. Multitechnique approach was adopted for the analysis of the samples. Composition has been determined via ion beam analysis; chemical states were investigated using x-ray photoelectron spectroscopy (XPS); crystalline structure was studied using transmission electron microscopy (TEM) and x-ray diffraction (XRD) and surface morphology by scanning electron microscope. The films deposited in pure argon atmosphere are tungsten rich and approach the target contents as N{sub 2}/Ar ratio is varied during deposition. Tungsten enrichment in the films is caused by resputtering of silicon which can be inhibited by the formation of silicon nitride, allowing films with Si/W ratio closer to the target compositions. The higher capability to form nitrides with silicon than with tungsten favors enhancement of nitrogen content in samples deposited from the silicon rich target (WSi{sub 2}). The samples with excess nitrogen content have shown losses of this element after thermal treatment. XPS measurements show a break of W-N bonds caused by thermal instability of tungsten nitrides. TEM and XRD revealed the segregation of tungsten in form of metallic or silicide nanoclusters in samples with low nitrogen content (W{sub 58}Si{sub 21}N{sub 21} and W{sub 24}Si{sub 42}N{sub 34}). High amounts of nitrogen were revealed to be highly effective in inhibiting metallic cluster coalescence. Measurements of electrical resistivity of as deposited films were performed using four point probe technique. They were found to lie in the range between 0.4 and 79 m{omega} cm depending on sample composition.

  9. Pulsed DC reactively sputtered tantalum oxide thin films for embedded capacitors

    NASA Astrophysics Data System (ADS)

    Jain, Pushkar

    Embedded capacitor technology, where thin film capacitors are integrated at on-chip and/or off-chip levels, offers high packaging densities and improved electrical performance at potentially reduced costs of capacitor fabrication and integration. This research explores and establishes the leverages of using thin film embedded capacitors over currently used surface mount discrete capacitors. In particular, this thesis focuses on developing pulsed dc reactively sputtered tantalum oxide (Ta2O5) thin film capacitors to be integrated into established interconnect technologies of IC chips and packages. A correlation between electrical breakdown field and dielectric constant, EBR (MV/cm) = (20/ 3r ) is empirically determined and used to establish a design space for breakdown voltage and capacitance density of planar capacitors, with film thickness and material dielectric constant as parameters. This design space sets the limits for "best one can achieve" (BOCA) breakdown voltages and capacitance densities using a particular dielectric. The validity of the developed design space is experimentally verified with Ta2O 5 thin films over a wide range of film thickness (0.05 to 5.4 mum). High frequency test vehicles were designed and fabricated to evaluate the electrical performance of Ta2O5, SiO 2, and Si3N4 thin film capacitors over a wide range of frequencies (dc to 20 GHz). Ta2O5, SiO 2, and Si3N4 show no dispersion at least up to 20 GHz. The total inductance of power connect vias is determined to be less than 50 pH/mum of via, which is at least two orders of magnitude lower than most discrete capacitors along with connection leads (>4 nH). The extent of Cu diffusion/drift into Ta2O5 films is determined and compared with Al, Ta, and Ti at various biasing and temperature conditions using bias-temperature-stress (BTS) and triangular voltage sweep (TVS) techniques. No Cu diffusion was detected at 150°C at least till 0.75 MV/cm. (Abstract shortened by UMI.)

  10. Corrosion and wear behaviours of a reactive-sputter-deposited Ta2O5 nanoceramic coating

    NASA Astrophysics Data System (ADS)

    Hu, Wei; Xu, Jiang; Lu, Xiaolin; Hu, Dongsheng; Tao, Hongliang; Munroe, Paul; Xie, Zong-Han

    2016-04-01

    In order to improve the wear and corrosion resistance of Ti-6Al-4V, a novel β-Ta2O5 nanoceramic coating was synthesised using reactive sputter deposition enabled by double glow discharge plasma technique. The surface topography, chemical composition, and microstructure of the newly developed coating were characterised by a variety of surface analytical techniques. The coating microstructure was found to exhibit a compact striated pattern extending in a direction perpendicular to coating surface, which is composed of equiaxed β-Ta2O5 grains with an average grain size of ∼20 nm, well adhered to the Ti-6A1-4V substrate. The hardness and the Young's modulus of the as-deposited coating were obtained by nanoindentation, and the adhesion strength between the coating and substrate was determined by a scratch tester. The dry sliding wear behaviours of the coating were investigated at room temperature against Si3N4 ceramic balls at room temperature under applied loads ranging from 2.3 N to 5.3 N using a ball-on-disc tribometer. The specific wear rates of the coating exhibited only a slight increase with applied normal load, and were shown to be two orders of magnitude lower than that for Ti-6Al-4V under the same loading condition. Furthermore, the electrochemical behaviour of the coating immersed in 3.5 wt.% NaCl solution was systematically examined by using a range of complementary electrochemical techniques including potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis as well as potential of zero charge (PZC). The results showed that the corrosion resistance of the β-Ta2O5 nanoceramic coating was better than that of Ti-6Al-4V alloy in 3.5 wt.% NaCl solution. Hence, by possessing higher mechanical properties and good wear and corrosion resistance, the β-Ta2O5 nanoceramic coating is considered to be a promising candidate for protection of engineering components operating under harsh conditions.

  11. Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering

    PubMed Central

    2013-01-01

    The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications. PMID:23570658

  12. Ion-enhanced oxidation of aluminum as a fundamental surface process during target poisoning in reactive magnetron sputtering

    SciTech Connect

    Kuschel, Thomas; Keudell, Achim von

    2010-05-15

    Plasma deposition of aluminum oxide by reactive magnetron sputtering (RMS) using an aluminum target and argon and oxygen as working gases is an important technological process. The undesired oxidation of the target itself, however, causes the so-called target poisoning, which leads to strong hysteresis effects during RMS operation. The oxidation occurs by chemisorption of oxygen atoms and molecules with a simultaneous ion bombardment being present. This heterogenous surface reaction is studied in a quantified particle beam experiment employing beams of oxygen molecules and argon ions impinging onto an aluminum-coated quartz microbalance. The oxidation and/or sputtering rates are measured with this microbalance and the resulting oxide layers are analyzed by x-ray photoelectron spectroscopy. The sticking coefficient of oxygen molecules is determined to 0.015 in the zero coverage limit. The sputtering yields of pure aluminum by argon ions are determined to 0.4, 0.62, and 0.8 at 200, 300, and 400 eV. The variation in the effective sticking coefficient and sputtering yield during the combined impact of argon ions and oxygen molecules is modeled with a set of rate equations. A good agreement is achieved if one postulates an ion-induced surface activation process, which facilitates oxygen chemisorption. This process may be identified with knock-on implantation of surface-bonded oxygen, with an electric-field-driven in-diffusion of oxygen or with an ion-enhanced surface activation process. Based on these fundamental processes, a robust set of balance equations is proposed to describe target poisoning effects in RMS.

  13. Conversion efficiency improvement of inverted CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells with room temperature sputtered ZnO by adding the C{sub 60} interlayer

    SciTech Connect

    Lai, Wei-Chih Chen, Peter; Lin, Kun-Wei; Wang, Yuan-Ting; Guo, Tzung-Fang

    2015-12-21

    We have demonstrated the performance of inverted CH{sub 3}NH{sub 3}PbI{sub 3} perovskite-based solar cells (SCs) with a room temperature (RT) sputtered ZnO electron transport layer by adding fullerene (C{sub 60}) interlayer. ZnO exhibits a better matched conduction band level with perovskite and Al work function and around energy offset of 2.2 eV between highest occupied molecular orbital level of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite and valance band level of ZnO. However, the CH{sub 3}NH{sub 3}PbI{sub 3} perovskite layer will be damaged during direct RT sputtering deposition of ZnO. Therefore, the C{sub 60} interlayer having matched conduction band level with ZnO and CH{sub 3}NH{sub 3}PbI{sub 3} perovskite added between the CH{sub 3}NH{sub 3}PbI{sub 3} perovskite and RT sputtered ZnO layers for protection prevents sputtering damages on the CH{sub 3}NH{sub 3}PbI{sub 3} perovskite layer. The short-circuit current density (J{sub SC}, 19.41 mA/cm{sup 2}) and open circuit voltage (V{sub OC}, 0.91 V) of the SCs with glass/ITO/poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS)/perovskite/C{sub 60}/RT sputtered ZnO/Al structure is higher than the J{sub SC} (16.23 mA/cm{sup 2}) and V{sub OC} (0.90 V) of the reference SC with glass/ITO/PEDOT:PSS/perovskite/C{sub 60}/bathocuproine (BCP)/Al structure. Although the SCs with the former structure has a lower fill factor (FF%) than the SCs with the latter structure, its conversion efficiency η% (10.93%) is higher than that (10.6%) of the latter.

  14. Formation of ST12 phase Ge nanoparticles in ZnO thin films

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Gumrukcu, Emre; Ozcan, Sadan

    2015-03-01

    In this work, we investigate the effects of reactive and nonreactive growth of ZnO on the rapid thermal annealing (RTA) induced formation of Ge nanoparticles (Ge-np) in ZnO: Ge nanocomposite thin films. The samples were deposited by sequential sputtering of ZnO and Ge thin film layers with a total thickness of about 600 nm on Si substrates followed by an ex-situ (RTA) at 600°C for 30, 60, 90, 120, 150, 180, and 210 s under forming gas atmosphere. In order for the reactive sputtering of ZnO layer, 5 mTorr Oxygen was introduced to the growth chamber. XRD and Raman analyses were utilized to investigate the effect of RTA time on the structural evolution of the samples. It has been realized that crystal structure of Ge nanoparticles is significantly affected by the growth method of the embedding ZnO layer. While reactive deposition of ZnO layers results in a mixture of diamond cubic (DC) and simple tetragonal (ST12) Ge-np, nonreactive deposition of ZnO layers leads to the formation of pure DC Ge-np upon RTA process. Formation of these two phases has been discussed based on the existence of native point defects such as oxygen vacancies and Zn interstitials.

  15. Observation of a periodic runaway in the reactive Ar/O{sub 2} high power impulse magnetron sputtering discharge

    SciTech Connect

    Shayestehaminzadeh, Seyedmohammad E-mail: shayesteh@mch.rwth-aachen.de; Arnalds, Unnar B.; Magnusson, Rögnvaldur L.; Olafsson, Sveinn

    2015-11-15

    This paper reports the observation of a periodic runaway of plasma to a higher density for the reactive discharge of the target material (Ti) with moderate sputter yield. Variable emission of secondary electrons, for the alternating transition of the target from metal mode to oxide mode, is understood to be the main reason for the runaway occurring periodically. Increasing the pulsing frequency can bring the target back to a metal (or suboxide) mode, and eliminate the periodic transition of the target. Therefore, a pulsing frequency interval is defined for the reactive Ar/O{sub 2} discharge in order to sustain the plasma in a runaway-free mode without exceeding the maximum power that the magnetron can tolerate.

  16. Optimized structure stability and electrochemical performance of LiNi0.8Co0.15Al0.05O2 by sputtering nanoscale ZnO film

    NASA Astrophysics Data System (ADS)

    Lai, Yan-Qing; Xu, Ming; Zhang, Zhi-An; Gao, Chun-Hui; Wang, Peng; Yu, Zi-Yang

    2016-03-01

    LiNi0.8Co0.15Al0.05O2 (NCA) is one of the most promising cathode material for lithium-ion batteries (LIBs) in electric vehicles, which is successfully adopted in Tesla. However, the dissolution of the cation into the electrolyte is still a one of the major challenges (fading capacity and poor cyclability, etc.) presented in pristine NCA. Herein, a homogeneous nanoscale ZnO film is directly sputtered on the surface of NCA electrode via the magnetron sputtering (MS). This ZnO film is evidenced by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results clearly demonstrate that ZnO film is fully and uniformly covered on the NCA electrodes. After 90 cycles at 1.0C, the optimized MS-2min coated NCA electrode delivers much higher discharge capacity with 169 mAh g-1 than that of the pristine NCA electrode with 127 mAh g-1. In addition, the discharge capacity also reaches 166 mAh g-1 at 3.0C, as compared to that of 125 mAh g-1 for the pristine electrode. The improved electrochemical performance can be ascribed to the superiority of the MS ZnO film that reduce charge transfer resistance and protect the NCA electrode from cation dissolution.

  17. Effects of NIR annealing on the characteristics of al-doped ZnO thin films prepared by RF sputtering

    PubMed Central

    2012-01-01

    Aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by employing radio frequency (RF) sputtering method for transparent conducting oxide applications. For the RF sputtering process, a ZnO:Al2O3 (2 wt.%) target was employed. In this paper, the effects of near infrared ray (NIR) annealing technique on the structural, optical, and electrical properties of the AZO thin films have been researched. Experimental results showed that NIR annealing affected the microstructure, electrical resistance, and optical transmittance of the AZO thin films. X-ray diffraction analysis revealed that all films have a hexagonal wurtzite crystal structure with the preferentially c-axis oriented normal to the substrate surface. Optical transmittance spectra of the AZO thin films exhibited transmittance higher than about 80% within the visible wavelength region, and the optical direct bandgap (Eg) of the AZO films was increased with increasing the NIR energy efficiency. PMID:22673232

  18. p-type conduction from Sb-doped ZnO thin films grown by dual ion beam sputtering in the absence of oxygen ambient

    SciTech Connect

    Kumar Pandey, Sushil; Kumar Pandey, Saurabh; Awasthi, Vishnu; Kumar, Ashish; Mukherjee, Shaibal; Deshpande, Uday P.; Gupta, Mukul

    2013-10-28

    Sb-doped ZnO (SZO) thin films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system in the absence of oxygen ambient. The electrical, structural, morphological, and elemental properties of SZO thin films were studied for films grown at different substrate temperatures ranging from 200 °C to 600 °C and then annealed in situ at 800 °C under vacuum (pressure ∼5 × 10{sup −8} mbar). Films grown for temperature range of 200–500 °C showed p-type conduction with hole concentration of 1.374 × 10{sup 16} to 5.538 × 10{sup 16} cm{sup −3}, resistivity of 66.733–12.758 Ω cm, and carrier mobility of 4.964–8.846 cm{sup 2} V{sup −1} s{sup −1} at room temperature. However, the film grown at 600 °C showed n-type behavior. Additionally, current-voltage (I–V) characteristic of p-ZnO/n-Si heterojunction showed a diode-like behavior, and that further confirmed the p-type conduction in ZnO by Sb doping. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. X-ray photoelectron spectroscopy analysis confirmed the formation of Sb{sub Zn}–2V{sub Zn} complex caused acceptor-like behavior in SZO films.

  19. Effect of substrate temperature on transparent conducting Al and F co-doped ZnO thin films prepared by rf magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Fang-Hsing; Chang, Chiao-Lu

    2016-05-01

    ZnO is a wide bandgap semiconductor that has many potential applications such as solar cells, thin film transistors, light emitting diodes, and gas/biological sensors. In this study, a composite ceramic ZnO target containing 1 wt% Al2O3 and 1.5 wt% ZnF2 was prepared and used to deposit transparent conducting Al and F co-doped zinc oxide (AFZO) thin films on glass substrates by radio frequency magnetron sputtering. The effect of substrate temperatures ranging from room temperature (RT) to 200 °C on structural, morphological, electrical, chemical, and optical properties of the deposited thin films were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Hall effect measurement, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and UV-vis spectrophotometer. The XRD results showed that all the AFZO thin films had a (0 0 2) diffraction peak, indicating a typical wurtzite structure with a preferential orientation of the c-axis perpendicular to the substrate. The FE-SEM and AFM analyses indicated that the crystallinity and grain size of the films were enhanced while the surface roughness decreased as the substrate temperature increased. Results of Hall effect measurement showed that Al and F co-doping decreased the resistivity more effectively than single-doping (either Al or F doping) in ZnO thin films. The resistivity of the AFZO thin films decreased from 5.48 × 10-4 to 2.88 × 10-4 Ω-cm as the substrate temperature increased from RT to 200 °C due to the increased carrier concentration and Hall mobility. The optical transmittances of all the AFZO thin films were over 92% in the wavelength range of 400-800 nm regardless of substrate temperature. The blue-shift of absorption edge accompanied the rise of the optical band gap, which conformed to the Burstein-Moss effect. The developed AFZO thin films are suitable as transparent conducting electrodes for various optoelectronic

  20. Flow cytometric assessment of reactive oxygen species generations that are directly related to cellular ZnO nanoparticle uptake.

    PubMed

    Yoo, Hyun Ju; Yoon, Tae Hyun

    2014-07-01

    In this study, a simple flow cytometry protocol to evaluate nanoparticle associated biological response was proposed. Particularly, we have evaluated the effect of surface charge on the cellular nanoparticle associations and nanoparticle-induced apoptosis. Significant enhancement in side scattering intensity was observed for the HeLa cells treated with positively charged (PLL)ZnO nanoparticles, suggesting that the (PLL)ZnO nanoparticles may induce cell death via adsorption and endocytosis of the nanoparticles. On the other hand, the negatively charged (PAA)ZnO nanoparticle seems to cause cell death process indirectly via the released Zn ions, with less contribution from cellular association of nanoparticles. Time- and dose-dependent studies on cellular association of ZnO nanoparticles, and ZnO associated reactive oxygen species generation were also performed for the HeLa cells exposed to the (PLL)ZnO nanoparticle. For those cells associated with (PLL)ZnO nanoparticle, a significant enhancement in reactive oxygen species generation was observed even at a lower concentration (10 ppm), which was not observable for the results with the whole cell population. By using this approach, we are able to distinguish biological responses (e.g., reactive oxygen species (ROS) generation) directly related to the cellular associations of NPs from those indirectly related to the cellular associations of NPs, such as the cytotoxicity caused by the NP released metal ions.

  1. Nanostructured ZnO Films for Room Temperature Ammonia Sensing

    NASA Astrophysics Data System (ADS)

    Dhivya Ponnusamy; Sridharan Madanagurusamy

    2014-09-01

    Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV-Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH3) at room temperature (˜30°C). The fabricated ZnO film based sensor was capable of detecting NH3 at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.

  2. Growth Behavior of Ga-Doped ZnO Thin Films Deposited on Au/SiN/Si(001) Substrates by Radio Frequency Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Seo, Seon Hee; Kang, Hyon Chol

    2013-11-01

    This paper reports the growth behavior of Ga-doped ZnO (ZnO:Ga) thin films deposited on Au/SiN/Si(001) substrates by radio-frequency magnetron sputtering. The microstructures of the overgrown ZnO:Ga thin films were investigated by performing X-ray diffraction, scanning electron microcopy, and transmission electron microscopy analyses. It was confirmed that the growth process proceeds through three stages. In the first stage, nano-scale ZnO:Ga islands were grown on the SiN layer, while a fairly continuous flat structure was formed on the Au nanoparticles (NPs). In the second stage of the growth process, ZnO:Ga domains with different growth orientations, depending strongly on the crystalline planes of the host Au NPs, were nucleated. These domains then grew at different rates, resulting in a change in the morphology from the initial shape reflecting that of the Au NPs to a sunflower-type shape. In the final stage, columnar growth with a preferred (0002) orientation along the surface normal direction became dominant.

  3. Superior electrochemical performance of LiCoO2 electrodes enabled by conductive Al2O3-doped ZnO coating via magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Dai, Xinyi; Zhou, Aijun; Xu, Jin; Yang, Bin; Wang, Liping; Li, Jingze

    2015-12-01

    A conductive Al2O3-doped ZnO (AZO) layer is coated directly on the LiCoO2 (LCO) porous composite electrode by magnetron sputtering of an AZO target, offering more efficient electron transfer and a stabilized interface layer. Up to 90% of the initial capacity of the AZO-coated electrode can be retained (173 mAh g-1) after 150 cycles between 3.0 and 4.5 V vs. Li/Li+. Meanwhile, the rate performance is remarkably improved showing a reversible capacity of 112 mAh g-1 at 12 C. The formation of amorphous solid electrolyte interface (SEI) observed on the uncoated LCO electrode is effectively impeded on the AZO-coated one. Acting as an intermediate barrier, the AZO layer can prevent chemical dissolution of the active materials by forming a thin passivation layer on the electrode surface containing some metal fluorides which are chemically inactive and ionically conductive. The positive role of the AZO coating is still effective under a more severe condition tested with an upper cut-off potential of 4.7 V.

  4. Visible light-induced photocatalytic properties of WO{sub 3} films deposited by dc reactive magnetron sputtering

    SciTech Connect

    Imai, Masahiro; Kikuchi, Maiko; Oka, Nobuto; Shigesato, Yuzo

    2012-05-15

    The authors examined the photocatalytic activity of WO{sub 3} films (thickness 500-600 nm) deposited on a fused quartz substrate heated at 350-800 deg. C by dc reactive magnetron sputtering using a W metal target under the O{sub 2} gas pressure from 1.0 to 5.0 Pa. Films deposited at 800 deg. C under 5.0 Pa have excellent crystallinity of triclinic, P1(1) structure and a large surface area, as confirmed by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Exposure of acetaldehyde (CH{sub 3}CHO) adsorbed onto the film surface to ultraviolet, visible, or standard fluorescence light induces oxidative photocatalytic decomposition indicated by a decrease in CH{sub 3}CHO concentration and generation of CO{sub 2} gas. For all three types of irradiation, concentration ratio of decreased CH{sub 3}CHO to increased CO{sub 2} is about 1:1, suggesting the possible presence of intermediates. The sputter-deposited WO{sub 3} film can be a good candidate as a visible light-responsive photocatalyst.

  5. Effect of duty cycle on the electrical and optical properties of VOx film deposited by pulsed reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Dong, Xiang; Wu, Zhiming; Xu, Xiangdong; Wei, Xiongbang; Jiang, Yadong

    2013-12-01

    Vanadium oxide (VOx) films were deposited onto well cleaned glass substrates by bipolar pulsed reactive magnetron sputtering at room temperature. Dependence of the structure, composition, optical and electrical properties of the films on the pulsed power's duty cycle has been investigated. The results from the X-ray diffraction (XRD) analysis show that there was no remarkable change in the amorphous structure in the films with duty cycle can be observed. But chemical analysis of the surface evaluated with x-ray photoelectron spectroscopy (XPS) indicates that decrease the duty cycle favors to enhance the oxidation of the vanadium. The optical and electrical properties of the films were characterized by spectroscopic ellipsometry and temperature dependent resistivity measurements, respectively. The evolution of the transmittance, optical band gap, optical constants, resistivity and temperature coefficient of resistance (TCR) of the deposited films with duty cycle was analyzed and discussed. In comparison with conventional DC sputtering, under the same discharge atmosphere and power level, these parameters of the VOx films can be modified over a broad range by duty cycle. Therefore adjusting the duty cycle during deposition, which is an effective way to control and optimize the performances of the VOx film for various optoelectronic devices applications.

  6. Reactive pulsed-DC sputtered Nb-doped VO2 coatings for smart thermochromic windows with active solar control.

    PubMed

    Batista, C; Carneiro, J; Ribeiro, R M; Teixeira, V

    2011-10-01

    Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive pulsed-DC magnetron sputtering. Different Nb doping amounts were introduced in the VO2 solid solution during the film growing which resulted in films with distinct semiconducting-metal phase transition temperatures. Pure VO2 showed improved thermochromic behavior as compared with VO2 films prepared by conventional DC sputtering. The transition temperatures were linearly decreased from 59 down to 34 degrees C with the increase in Nb content. However, the luminous transmittance and the infrared modulation efficiency were markedly affected. The surface morphology of the films was examined by scanning electron microscopy (SEM) and showed a tendency for grain sized reduction due to Nb addition. Moreover, the films were found to be very dense with no columnar microstructure. Structural analyses carried out by X-ray diffractometry (XRD) revealed that Nb introduces significant amount of defects in the crystal lattice which clearly degrade the optical properties.

  7. Substrate biasing effect on the physical properties of reactive RF-magnetron-sputtered aluminum oxide dielectric films on ITO glasses.

    PubMed

    Liang, Ling Yan; Cao, Hong Tao; Liu, Quan; Jiang, Ke Min; Liu, Zhi Min; Zhuge, Fei; Deng, Fu Ling

    2014-02-26

    High dielectric constant (high-k) Al2O3 thin films were prepared on ITO glasses by reactive RF-magnetron sputtering at room temperature. The effect of substrate bias on the subband structural, morphological, electrode/Al2O3 interfacial and electrical properties of the Al2O3 films is systematically investigated. An optical method based on spectroscopic ellipsometry measurement and modeling is adopted to probe the subband electronic structure, which facilitates us to vividly understand the band-tail and deep-level (4.8-5.0 eV above the valence band maximum) trap states. Well-selected substrate biases can suppress both the trap states due to promoted migration of sputtered particles, which optimizes the leakage current density, breakdown strength, and quadratic voltage coefficient of capacitance. Moreover, high porosity in the unbiased Al2O3 film is considered to induce the absorption of atmospheric moisture and the consequent occurrence of electrolysis reactions at electrode/Al2O3 interface, as a result ruining the electrical properties. PMID:24490685

  8. BiVO4 photoanodes for water splitting with high injection efficiency, deposited by reactive magnetron co-sputtering

    NASA Astrophysics Data System (ADS)

    Gong, Haibo; Freudenberg, Norman; Nie, Man; van de Krol, Roel; Ellmer, Klaus

    2016-04-01

    Photoactive bismuth vanadate (BiVO4) thin films were deposited by reactive co-magnetron sputtering from metallic Bi and V targets. The effects of the V-to-Bi ratio, molybdenum doping and post-annealing on the crystallographic and photoelectrochemical (PEC) properties of the BiVO4 films were investigated. Phase-pure monoclinic BiVO4 films, which are more photoactive than the tetragonal BiVO4 phase, were obtained under slightly vanadium-rich conditions. After annealing of the Mo-doped BiVO4 films, the photocurrent increased 2.6 times compared to undoped films. After optimization of the BiVO4 film thickness, the photocurrent densities (without a catalyst or a blocking layer or a hole scavenger) exceeded 1.2 mA/cm2 at a potential of 1.23 VRHE under solar AM1.5 irradiation. The surprisingly high injection efficiency of holes into the electrolyte is attributed to the highly porous film morphology. This co-magnetron sputtering preparation route for photoactive BiVO4 films opens new possibilities for the fabrication of large-scale devices for water splitting.

  9. Effects of Ti addiction in WO 3 thin film ammonia gas sensor prepared by dc reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hu, Ming; Yong, Cholyun; Feng, Youcai; Lv, Yuqiang; Han, Lei; Liang, Jiran; Wang, Haopeng

    2006-11-01

    WO 3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness (100-500 Å) onto WO 3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition on sensitive properties of WO 3 thin film to the NH 3 gas was then discussed. WO 3 thin films added Ti revealed excellent sensitivity and response characteristics in the presence of low concentration of NH 3 (5-400 ppm) gas in air at 200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO 3 thin films have a promotional effect on the response speed to NH 3 and selectivity enhanced with respect to other gases (CO, C IIH 5OH, CH 4). The influence of different substrates, including alumina, silicon and glass, on sensitivity to NH 3 gas has also been investigated.

  10. Reactively Sputtered Nanocrystalline ZrN Film as Extremely Thin Diffusion Barrier between Cu and SiO2

    NASA Astrophysics Data System (ADS)

    Mayumi B. Takeyama,; Masaru Sato,; Eiji Aoyagi,; Atsushi Noya,

    2010-05-01

    The results of analyses by X-ray diffraction, transmission electron microscopy, and grazing incidence X-ray reflectivity measurement indicate that a 5-nm-thick ZrN film interposed between Cu and SiO2 shows excellent barrier properties, tolerating annealing up to at least 500 °C for 30 min. The X-ray diffraction pattern reveals a decrease in the intensity of the Cu(111) reflection upon annealing at 800 °C, suggesting a failure of the thin barrier due to Cu diffusion through the barrier. We are confident that the formation of a continuous nanocrystalline ZrN film in a uniform fashion in a stable phase with a slightly nitrogen-rich composition is a cause of the excellent features obtained. The formation process of the ZrN film is discussed in terms of the nucleation process of reactive sputtering at a low deposition temperature.

  11. Bimodal substrate biasing to control γ-Al{sub 2}O{sub 3} deposition during reactive magnetron sputtering

    SciTech Connect

    Prenzel, Marina; Kortmann, Annika; Stein, Adrian; Keudell, Achim von; Nahif, Farwah; Schneider, Jochen M.

    2013-09-21

    Al{sub 2}O{sub 3} thin films have been deposited at substrate temperatures between 500 °C and 600 °C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.8 dpa for a substrate temperature of 500 °C. This threshold shifts to 0.6 dpa for films grown at 550 °C.

  12. Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with indium tin oxide

    NASA Astrophysics Data System (ADS)

    Deuermeier, Jonas; Gassmann, Jürgen; Brötz, Joachim; Klein, Andreas

    2011-06-01

    Thin films of copper oxides were prepared by reactive magnetron sputtering and structural, morphological, chemical, and electronic properties were analyzed using x-ray diffraction, atomic force microscopy, in situ photoelectron spectroscopy, and electrical resistance measurements. The deposition conditions for preparation of Cu(I)-oxide (Cu2O) are identified. In addition, the interface formation between Cu2O and Sn-doped In2O3 (ITO) was studied by stepwise deposition of Cu2O onto ITO and vice versa. A type II (staggered) band alignment with a valence band offset ΔEVB = 2.1-2.6 eV depending on interface preparation is observed. The band alignment explains the nonrectifying behavior of p-Cu2O/n-ITO junctions, which have been investigated for thin film solar cells.

  13. Investigation of antiperovskite Mn{sub 3}CuN{sub x} film prepared by DC reactive magnetron sputtering

    SciTech Connect

    Sun, Ying; Wang, Cong; Na, Yuanyuan; Chu, Lihua; Wen, Yongchun; Nie, Man

    2010-09-15

    Antiperovskite Mn{sub 3}CuN{sub x} film was prepared by dc reactive magnetron sputtering. It is the first time to report an antiperovskite ternary nitride film. The composition and crystal structure were characterized by energy dispersive spectroscope (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). From the XRD pattern, it displays a (1 0 0) preferential orientation. A comparative study on the properties of Mn{sub 3}CuN{sub x} film and the bulk sample was presented. The film exhibits an antiferromagnetic to paramagnetic transition around 135 K, similar with the bulk sample. With temperature, the resistivity of the film shows semiconductor-like behavior throughout the measured temperature region, whereas there is an abrupt drop around the magnetic transition for the bulk. The variable temperature XRD results indicate that the film did not display any structure transition and shows a normal linear thermal expansion property around the magnetic transition.

  14. Origin of the butterfly-shaped magnetoresistance in reactive sputtered epitaxial Fe{sub 3}O{sub 4} films

    SciTech Connect

    Li, P.; Zhang, L. T.; Mi, W. B.; Jiang, E. Y.; Bai, H. L.

    2009-08-01

    Epitaxial Fe{sub 3}O{sub 4} thin films were synthesized by facing-target reactive sputtering Fe targets. The epitaxy of the Fe{sub 3}O{sub 4} film on MgO (100) was examined macroscopically using x-ray diffraction, including conventional theta-2theta scan, tilting 2theta scan, phi scan, and pole figure. The observed low-field butterfly-shaped magnetoresistance (MR) are explained by the primary fast rotation of the spins far away from antiphase boundaries and the high-field MR changing linearly with magnetic field can be understood by the gradual rotation of the spins near the antiphase boundaries. It is magnetocrystalline anisotropy that causes an increase in MR below Verwey transition temperature.

  15. Effect of oxygen flow rate on the properties of SiOx films deposited by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lai, Fachun; Li, Ming; Wang, Haiqian; Jiang, Yousong; Song, Yizhou

    2005-08-01

    SiOx (x=0--2) films were deposited on BK-7 substrates by a low frequency reactive magnetron sputtering system with the oxygen flow rate (OFR) changing from 0 to 30 sccm. The samples were characterized by atomic force microscopy, spectrophotometer, and X-ray photoelectron spectroscopy. The extinction coefficient and refractive index decrease, while the optical transmittance increases with the increase of OFR from 0 to 17 sccm. The root mean square surface roughness has a maximum at 10 sccm OFR. The highest deposition rate is at 15 sccm OFR. Our results show that the films deposited at 20 sccm OFR are stoichiometric silica with relatively high deposition rate, low extinction coefficient, and low surface roughness. Therefore, a precise control of OFR is very important to obtain high quality films for optical applications.

  16. Potential for reactive pulsed-dc magnetron sputtering of nanocomposite VO{sub x} microbolometer thin films

    SciTech Connect

    Jin, Yao O. Ozcelik, Adem; Horn, Mark W.; Jackson, Thomas N.

    2014-11-01

    Vanadium oxide (VO{sub x}) thin films were deposited by reactive pulsed-dc sputtering a metallic vanadium target in argon/oxygen mixtures with substrate bias. Hysteretic oxidation of the vanadium target surface was assessed by measuring the average cathode current during deposition. Nonuniform oxidization of the target surface was analyzed by Raman spectroscopy. The VO{sub x} film deposition rate, resistivity, and temperature coefficient of resistance were correlated to oxygen to argon ratio, processing pressure, target-to-substrate distance, and oxygen inlet positions. To deposit VO{sub x} in the resistivity range of 0.1–10 Ω-cm with good uniformity and process control, lower processing pressure, larger target-to-substrate distance, and oxygen inlet near the substrate are useful.

  17. Reactive Sputter Deposition of WO3/Ag/WO3 Film for Indium Tin Oxide (ITO)-Free Electrochromic Devices.

    PubMed

    Yin, Yi; Lan, Changyong; Guo, Huayang; Li, Chun

    2016-02-17

    Functioning both as electrochromic (EC) and transparent-conductive (TC) coatings, WO3/Ag/WO3 (WAW) trilayer film shows promising potential application for ITO-free electrochromic devices. Reports on thermal-evaporated WAW films revealed that these bifunctional WAW films have distinct EC characteristics; however, their poor adhesive property leads to rapid degradation of coloring-bleaching cycling. Here, we show that WAW film with improved EC durability can be prepared by reactive sputtering using metal targets. We find that, by introducing an ultrathin tungsten (W) sacrificial layer before the deposition of external WO3, the oxidation of silver, which leads to film insulation and apparent optical haze, can be effectively avoided. We also find that the luminous transmittance and sheet resistance were sensitive to the thicknesses of tungsten and silver layers. The optimized structure for TC coating was obtained to be WO3 (45 nm)/Ag (10 nm)/W (2 nm)/WO3 (45 nm) with a sheet resistance of 16.3 Ω/□ and a luminous transmittance of 73.7%. Such film exhibits compelling EC performance with decent luminous transmittance modulation ΔTlum of 29.5%, fast switching time (6.6 s for coloring and 15.9 s for bleaching time), and long-term cycling stability (2000 cycles) with an applied potential of ±1.2 V. Thicker external WO3 layer (45/10/2/100 nm) leads to larger modulation with maximum ΔTlum of 46.4%, but at the cost of significantly increasing the sheet resistance. The strategy of introducing ultrathin metal sacrificial layer to avoid silver oxidation could be extended to fabricating other oxide-Ag-oxide transparent electrodes via low-cost reactive sputtering. PMID:26726834

  18. Highly oriented {delta}-Bi{sub 2}O{sub 3} thin films stable at room temperature synthesized by reactive magnetron sputtering

    SciTech Connect

    Lunca Popa, P.; Kerdsongpanya, S.; Lu, J.; Eklund, P.; Sonderby, S.; Bonanos, N.

    2013-01-28

    We report the synthesis by reactive magnetron sputtering and structural characterization of highly (111)-oriented thin films of {delta}-Bi{sub 2}O{sub 3}. This phase is obtained at a substrate temperature of 150-200 Degree-Sign C in a narrow window of O{sub 2}/Ar ratio in the sputtering gas (18%-20%). Transmission electron microscopy and x-ray diffraction reveal a polycrystalline columnar structure with (111) texture. The films are stable from room temperature up to 250 Degree-Sign C in vacuum and 350 Degree-Sign C in ambient air.

  19. Structure and Properties of Ti-O-N Coatings Produced by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Konischev, M. E.; Kuzmin, O. S.; Pustovalova, A. A.; Morozova, N. S.; Evdokimov, K. E.; Surmenev, R. A.; Pichugin, V. F.; Epple, M.

    2014-02-01

    Results of an experimental study of the optical characteristics of gas discharges are presented. The study was aimed at optimizing the operating modes of a mid-frequency magnetron sputtering system to efficiently deposit Ti-O-N coatings. The conditions for maintaining the intensity of the chosen spectroscopic lines that ensure synthesis of titanium oxide and titanium oxynitride coatings have been revealed. The morphology, structure, contact angle, and free surface energy of titanium oxide and titanium oxynitride coatings on type 12Kh18N10T stainless steel substrates were examined by using scanning and transmission electron microscopy and infrared spectroscopy, and by measuring the wetting angle. The results of examination of the structure and properties of the synthesized films and their physicomechanical and optical characteristics are given.

  20. Effects of Processing Variables on Tantalum Nitride by Reactive-Ion-Assisted Magnetron Sputtering Deposition

    NASA Astrophysics Data System (ADS)

    Wei, Chao‑Tsang; Shieh, Han‑Ping D.

    2006-08-01

    The binary compound tantalum nitride (TaN) and ternary compounds tantalum tungsten nitrides (Ta1-xWxNy) exhibit interesting properties such as high melting point, high hardness, and chemical inertness. Such nitrides were deposited on a tungsten carbide (WC) die and silicon wafers by ion-beam-sputter evaporation of the respective metal under nitrogen ion-assisted deposition (IAD). The effects of N2/Ar flux ratio, post annealing, ion-assisted deposition, deposition rate, and W doping in coating processing variables on hardness, load critical scratching, oxidation resistance, stress and surface roughness were investigated. The optimum N2/Ar flux ratios in view of the hardness and critical load of TaN and Ta1-xWxNy films were ranged from 0.9 to 1.0. Doping W into TaN to form Ta1-xWxNy films led significant increases in hardness, critical load, oxidation resistance, and reduced surface roughness. The optimum doping ratio was [W/(W+Ta)]=0.85. From the deposition rate and IAD experiments, the stress in the films is mainly contributed by sputtering atoms. The lower deposition rate at a high N2/Ar flux ratio resulted in a higher compressive stress. A high compressive residual stress accounts for a high hardness. The relatively high compressive stress was attributed primarily to peening by atoms, ions and electrons during film growth, the Ta1-xWxNy films showed excellent hardness and strength against a high temperature, and sticking phenomena can essentially be avoided through their use. Ta1-xWxNy films showed better performance than the TaN film in terms of mechanical properties and oxidation resistance.

  1. Hydrogen release kinetics during reactive magnetron sputter depostion of a-Si:H: An isotope labeling study

    NASA Astrophysics Data System (ADS)

    Abelson, J. R.; Mandrell, L.; Doyle, J. R.

    1994-08-01

    The release of moleculear hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an isotope labeling technique. The results demonstrate that surface-bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon-hydrogen atmosphere. To achieve isotope labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurments of film growth and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H-surface kinetics. Under conditions which produce electronically useful films, (1) 0.5-1.0 hydrogen atoms react with the growing surface per incorporated silicon atom, (2) the near surface of the growing film contains 1-3 x 10(exp 15)/sq cm pf excess hydrogen, the dominant hydrogen release mechanism is by direct abstraction to form H2 molecules, and the kinetics of H release and incorportation can be described by constant rate coefficients. These data are supported by studies of H interactions with single-crystal silicon and amorphous carbon surfaces.

  2. Preparation and study of Titanium Nitride films by reactive sputtering and an investigation of target poisoning during the process

    NASA Astrophysics Data System (ADS)

    Aziz, Tareque; Rumaiz, Abdul

    Titanium Nitride (TiNx) thin films were prepared by reactive dc sputtering in presence of Ar-N2 plasma. The thin films were grown on Quartz and pure Si surfaces. The Ar-N2 content ratio was gradually varied while the substrate and the Titanium target were kept at room temperature. Structural properties, optical and electrical properties of the thin films were studied by using X-ray Photoelectron Spectroscopy (XPS) and XRD and 4 probe resistivity measurement. Target poisoning of the Ti target was also studied by varying reactive gas concentration and measuring the target current. A study of target current vs growth rate of the films was performed to investigate the onset of ``poison'' mode.Although there was an insignificant drop in plasma current, we noticed a drop in the deposition rate. This result was tested against Monte Carlo simulations using SRIM simulations. Effects of annealing on the crystallinity and the sheet resistance will also be discussed. The work has been supported by BSA,DOE.

  3. Stoichiometric silicon oxynitride thin films reactively sputtered in Ar/N2O plasmas by HiPIMS

    NASA Astrophysics Data System (ADS)

    Hänninen, Tuomas; Schmidt, Susann; Wissting, Jonas; Jensen, Jens; Hultman, Lars; Högberg, Hans

    2016-04-01

    Silicon oxynitride (SiO x N y , x=0.2-1.3, y=0.2 -0.7) thin films were synthesized by reactive high power impulse magnetron sputtering from a pure silicon target in Ar/N2O atmospheres. It was found that the composition of the material can be controlled by the reactive gas flow and the average target power. X-ray photoelectron spectroscopy (XPS) shows that high average powers result in more silicon-rich films, while lower target powers yield silicon-oxide-like material due to more pronounced target poisoning. The amount of nitrogen in the films can be controlled by the percentage of nitrous oxide in the working gas. The nitrogen content remains at a constant level while the target is operated in the transition region between metallic and poisoned target surface conditions. The extent of target poisoning is gauged by the changes in peak target current under the different deposition conditions. XPS also shows that varying concentrations and ratios of oxygen and nitrogen in the films result in film chemical bonding structures ranging from silicon-rich to stoichiometric silicon oxynitrides having no observable Si-Si bond contributions. Spectroscopic ellipsometry shows that the film optical properties depend on the amount and ratio of oxygen and nitrogen in the compound, with film refractive indices measured at 633 nm ranging between those of SiO2 and Si3N4.

  4. Thermoelectric and Magneto-Thermoelectric Properties of Ga-DOPED ZnO Thin Films by RF Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Liu, H.; Fang, L.; Wu, F.; Tian, D. X.; Li, W. J.; Lu, Y.; Kong, C. Y.; Zhang, S. F.

    2014-04-01

    Zn(1-x)GaxO thin films (x = 0.01, 0.03, 0.05, 0.07 named as GZO1, GZO2, GZO3, GZO4, respectively) were deposited on glass substrates by RF magnetron sputtering. The crystal structure, electrical, thermoelectric and magneto-thermoelectric properties of GZO films were investigated. It is found that all the GZO films are polycrystalline and preferentially oriented in the c-axis. The electrical resistivity of GZO films decreased first with increasing Ga doping content before it reached a minimum at x = 0.05, and then increased with further increasing Ga doping content. The magnetic fields (B) ranging from 0 to 1.5 T are perpendicularly applied to the films to study the magneto-thermoelectric properties. It is observed that the absolute values of Seebeck coefficients (|S|) of GZO1, GZO2, GZO3 show marked variation with magnetic field and obtain the maximum value at B = 0.5 T. Whereas the |S| value of GZO4 fluctuates slightly with magnetic field and reaches its peak at B = 1.0 T. The magneto-thermoelectric properties are analyzed and we propose that this behavior is mainly attributed to the effect of magnetic field on the electron transport.

  5. Optical, electrical and mechanical properties of Ga-doped ZnO thin films under different sputtering powers

    NASA Astrophysics Data System (ADS)

    Chang, Sheng Hsiung; Cheng, Hsin-Ming; Tien, Chuen-Lin; Lin, Shih-Chin; Chuang, Kie-Pin

    2014-12-01

    We present the optical, electrical and mechanical properties of Ga-doped zinc oxide (GZO) thin films prepared by radio-frequency (RF) magnetron sputtering at room temperature under different RF powers (80-180 W). The thickness, electron concentration, and electron mobility of the GZO thin film were determined by fitting the visible-to-near-infrared transmittance spectrum of GZO film/glass using the transfer matrix method. The bending force per unit width was measured by a home-made Twyman-Green interferometer with the fast Fourier transform method. The obtained results show that the optical, electrical and mechanical properties of GZO thin film are subject to the RF power. At an RF power of 140 W, the local minimum of bending force per unit width corresponds to the highest electron mobility in GZO thin film. This study demonstrates that the optical, electrical and mechanical properties of GZO thin film can be fully resolved by non-contact optical methods.

  6. Comparative study of RF reactive magnetron sputtering and sol-gel deposition of UV induced superhydrophilic TiOx thin films

    NASA Astrophysics Data System (ADS)

    Vrakatseli, V. E.; Amanatides, E.; Mataras, D.

    2016-03-01

    TiOx and TiOx-like thin films were deposited on PEEK (Polyether ether ketone) substrates by low-temperature RF reactive magnetron sputtering and the sol-gel method. The resulting films were compared in terms of their properties and photoinduced hydrophilicity. Both techniques resulted in uniform films with good adhesion that can be switched to superhydrophilic after exposure to UVA radiation for similar time periods. In addition, the sputtered films can also be activated and switched to superhydrophilic by natural sunlight due to the higher absorption in the visible spectrum compared to the sol-gel films. On the other hand, the as deposited sol-films remain relatively hydrophilic for a longer time in dark compared to the sputtered film due to the differences in the morphology and the porosity of the two materials. Thus, depending on the application, either method can be used in order to achieve the desirable TiOx properties.

  7. Structural and gasochromic properties of WO3 films prepared by reactive sputtering deposition

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.; Hakoda, T.; Miyashita, A.; Yoshikawa, M.

    2015-02-01

    The effects of deposition temperature and film thickness on the structural and gasochromic properties of tungsten trioxide (WO3) films used for the optical detection of diluted cyclohexane gas have been investigated. The WO3 films were prepared on SiO2 substrates by magnetron sputtering, with the deposition temperature ranging from 300 to 550 °C in an Ar and O2 gas mixture. The films were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and Rutherford backscattering spectroscopy (RBS). The gasochromic properties of the WO3 films, coated with a catalytic Pt layer, were examined by exposing them to up to 5% cyclohexane in N2 gas. It was found that (001)-oriented monoclinic WO3 films, with a columnar structure, grew at deposition temperatures between 400 and 450 °C. Furthermore, (010)-oriented WO3 films were preferably formed at deposition temperatures higher than 500 °C. The gasochromic characterization of the Pt/WO3 films revealed that (001)-oriented WO3 films, with cauliflower-like surface morphology, were appropriate for the optical detection of cyclohexane gas.

  8. Low temperature deposition of transparent conducting ITO/Au/ITO films by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Kim, Daeil

    2010-01-01

    Transparent conducting indium tin oxide/Au/indium tin oxide (ITO) multilayered films were deposited on unheated polycarbonate substrates by magnetron sputtering. The thickness of the Au intermediated film varied from 5 to 20 nm. Changes in the microstructure, surface roughness and optoelectrical properties of the ITO/Au/ITO films were investigated with respect to the thickness of the Au intermediated layer. X-ray diffraction measurements of ITO single layer films did not show characteristic diffraction peaks, while ITO/Au/ITO films showed an In 2O 3 (2 2 2) characteristic diffraction peak. The optoelectrical properties of the films were also dependent on the presence and thickness of the Au thin film. The ITO 50 nm/Au 10 nm/ITO 40 nm films had a sheet resistance of 5.6 Ω/□ and an average optical transmittance of 72% in the visible wavelength range of 400-700 nm. Consequently, the crystallinity, which affects the optoelectrical properties of ITO films, can be enhanced with Au intermediated films.

  9. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Harris, M. T.; George, Michael A.; McCarty, P.

    1999-01-01

    As a high temperature semiconductor, ZnO has been used for many applications such as wave-guide, solar cells, and surface acoustic wave devices. Since the ZnO material has an energy gap of 3.3 eV at room temperature and an excitonic binding energy (60 meV) that is possible to make excitonic lasering at room temperature a recent surge of interest is to synthesize ZnO films for electro-optical devices. These applications require films with a smooth surface, good crystal quality, and low defect density. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystals are grown by the hydrothermal method. Substrates are mechanically polished and annealed in air for four hours before deposited films. The annealing temperature-dependence of ZnO substrates is studied. Films are synthesized by the off-axis reactive sputtering deposition. The films have very smooth surface with a roughness ZnO films grown of (0001) ZnO and (0001) sapphire substrates will be also compared and discussed in the presentation.

  10. Optimizing TaOx memristor performance and consistency within the reactive sputtering "forbidden region"

    NASA Astrophysics Data System (ADS)

    Lohn, Andrew J.; Stevens, James E.; Mickel, Patrick R.; Marinella, Matthew J.

    2013-08-01

    Standard deposition processes for depositing ReRAM oxides utilize mass flow of reactive gas to control stoichiometry and have difficulty depositing a precisely defined sub-stoichiometry within a "forbidden region" where film properties are discontinuous with mass flow. We show that by maintaining partial pressure within this discontinuous "forbidden region," instead of by maintaining mass flow, we can optimize tantalum oxide device properties and reduce or eliminate the electroforming step. We also show that defining the partial pressure set point as a fraction of the "forbidden region" instead of as an absolute value can be used to improve wafer-to-wafer consistency with minimal recalibration efforts.

  11. Atomistic growth phenomena of reactively sputtered RuO{sub 2} and MnO{sub 2} thin films

    SciTech Connect

    Music, Denis Bliem, Pascal; Geyer, Richard W.; Schneider, Jochen M.

    2015-07-07

    We have synthesized RuO{sub 2} and MnO{sub 2} thin films under identical growth conditions using reactive DC sputtering. Strikingly different morphologies, namely, the formation of RuO{sub 2} nanorods and faceted, nanocrystalline MnO{sub 2}, are observed. To identify the underlying mechanisms, we have carried out density functional theory based molecular dynamics simulations of the growth of one monolayer. Ru and O{sub 2} molecules are preferentially adsorbed at their respective RuO{sub 2} ideal surface sites. This is consistent with the close to defect free growth observed experimentally. In contrast, Mn penetrates the MnO{sub 2} surface reaching the third subsurface layer and remains at this deep interstitial site 3.10 Å below the pristine surface, resulting in atomic scale decomposition of MnO{sub 2}. Due to this atomic scale decomposition, MnO{sub 2} may have to be renucleated during growth, which is consistent with experiments.

  12. Giant planar Hall effect in reactive sputtered epitaxial CrxFe3-xO4 films

    NASA Astrophysics Data System (ADS)

    Li, P.; Cui, W. Y.; Jin, C.; Bai, H. L.

    2014-09-01

    The epitaxial CrxFe3-xO4 films were fabricated by dc reactive sputtering on MgO (001) substrates. The longitudinal resistivity ρxx was enhanced 3 orders of magnitude with the increase of Cr content x from 0 to 0.87. The tunneling magnetoresistance like planar Hall effect in the CrxFe3-xO4 films was observed while the angle between ⟨100⟩ in (001) oriented films and the direction of magnetic field is 45° and 135°, respectively. Both the phase relation of angular dependent planar Hall resistivity ρxy and the numeral relation of ρxy with longitudinal resistivity difference ρ//-ρ⊥ cannot be understood by the planar Hall effect expression in isotropic magnetic medium. The largest planar Hall resistivity was ˜105 μΩ cm for x = 0.71, which is one, two, and six orders of magnitude larger than that in Fe3O4, GaMnAs, and ferromagnetic metals, respectively. The giant planar Hall resistivity ρxy is weak saturated at high fields and increases with the magnetic field. This giant planar Hall effect in the highly resistive CrxFe3-xO4 films is closely correlated to the longitudinal resistivity and antiphase boundaries.

  13. Proton conductive tantalum oxide thin film deposited by reactive DC magnetron sputtering for all-solid-state switchable mirror

    NASA Astrophysics Data System (ADS)

    Tajima, K.; Yamada, Y.; Bao, S.; Okada, M.; Yoshimura, K.

    2008-03-01

    Our developed all-solid-state switchable mirror as a smart window is consisted in multi-layer of Mg4Ni/Pd/Ta2O5/WO3/ITO/glass and can switch reversibly from the reflective state to the transparent one. The development of high performance solid electrolyte thin film of Ta2O5 is important for fast speed switching and high durability of the device. In this work, we have investigated the electrochemical property of Ta2O5 thin film deposited by reactive DC magnetron sputtering. The effect of thickness on electrochemical and proton conductivities of Ta2O5 thin film was investigated. The Ta2O5 thin film with a thickness of 400 nm had better proton conductivity of 1.5×10-9 S/cm measured by AC impedance method. The transmittance at wavelength of 670 nm of the device with 400 nm thick Ta2O5 thin film was changed from 0.1% (reflective state) to 51% (transparent state) within 10 s by applying voltage of 5 V. The device showed high durability up to two-thousand switching cycles.

  14. Reactive dc magnetron sputtering of (GeO{sub x}-SiO{sub 2}) superlattices for Ge nanocrystal formation

    SciTech Connect

    Zschintzsch, M.; Jeutter, N. M.; Borany, J. von; Krause, M.; Muecklich, A.

    2010-02-15

    The motivation of this work is the tailored growth of Ge nanocrystals for photovoltaic applications. The use of superlattices provides a reliable method to control the Ge nanocrystal size after phase separation. In this paper, we report on the deposition of (GeO{sub x}-SiO{sub 2}) superlattices via reactive dc magnetron sputtering and the self-ordered Ge nanocrystal formation during subsequent annealing. Attention is directed mainly to define proper deposition conditions for tuning the GeO{sub x} composition between elemental Ge (x=0) and GeO{sub 2} (x=2) by the variation in the deposition temperature and the oxygen partial pressure. A convenient process window has been found which allows sequential GeO{sub x}-SiO{sub 2} deposition without changing the oxygen partial pressure during deposition. The phase separation and Ge nanocrystal formation after subsequent annealing were investigated with in situ x-ray scattering, Raman spectroscopy, and electron microscopy. By these methods the existence of 2-5 nm Ge nanocrystals at annealing temperatures of 600-750 deg. C has been confirmed which is within the superlattice stability range. The technique used allows the fabrication of superlattice stacks with very smooth interfaces (roughness<1 nm); thus the Ge nanocrystal layers could be separated by very thin SiO{sub 2} films (d<3 nm) which offers interesting possibilities for charge transport via direct tunneling.

  15. Correlation of photothermal conversion on the photo-induced deformation of amorphous carbon nitride films prepared by reactive sputtering

    SciTech Connect

    Harata, T.; Aono, M. Kitazawa, N.; Watanabe, Y.

    2014-08-04

    The photo-induced deformation of hydrogen-free amorphous carbon nitride (a-CN{sub x}) films was investigated under visible-light illumination. The films gave rise to photothermal conversion by irradiation. In this study, we investigated the effects of thermal energy generated by irradiation on the deformation of a-CN{sub x}/ultrathin substrate bimorph specimens. The films were prepared on both ultrathin Si and SiO{sub 2} substrates by reactive radio-frequency magnetron sputtering from a graphite target in the presence of pure nitrogen gas. The temperature of the film on the SiO{sub 2} substrate increased as the optical band-gap of the a-CN{sub x} was decreased. For the film on Si, the temperature remained constant. The deformation degree of the films on Si and SiO{sub 2} substrates were approximately the same. Thus, the deformation of a-CN{sub x} films primarily induced by photon energy directly.

  16. SEMICONDUCTOR DEVICES: An MWCNT-doped SNO2 thin film NO2 gas sensor by RF reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wei, Lin; Shizhen, Huang; Wenzhe, Chen

    2010-02-01

    An MWCNT-doped (multi-walled carbon nanotube) SnO2 thin film NO2 gas sensor, prepared by radio frequency reactive magnetron sputtering, showed a high sensitivity to ultra-low concentrations of NO2 in the parts per billion range. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM) characterizations indicated that the MWCNTs were affected by the morphology of the SnO2 thin film and the particle size. The properties of the MWCNT-doped SnO2 sensor, such as sensitivity, selectivity, and response-recovery time, were investigated. Experimental results revealed that the MWCNT-doped SnO2 thin film sensor response to NO2 gas depended on the operating temperature, NO2 gas concentration, thermal treatment conditions, film thickness, and so on. The mechanism of the gas-sensing property of the MWCNT-doped Sn22 thin film sensor was investigated and showed that the improved gas-sensing performance should be attributed to the effects between MWCNTs (p-type) and SnO2 (n-type) semiconductors.

  17. Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films

    NASA Astrophysics Data System (ADS)

    Hu, C. Q.; Zhu, J. Q.; Zheng, W. T.; Han, J. C.

    2009-01-01

    The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge 1- xC x) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH 4/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures ( Ta) above 300 °C decreases, whereas that of C-H bonds show a decrease only when Ta exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at Ta above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge 1- xC x films are almost constant against Ta, which can be ascribed to the unchanged ratios of Ge/C and sp 2-C/sp 3-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge 1- xC x double-layer film on ZnS substrate is still maintained after annealing at 700 °C.

  18. Study of Fluorine Addition Influence in the Dielectric Constant of Diamond-Like Carbon Thin Film Deposited by Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Trippe, S. C.; Mansano, R. D.

    The hydrogenated amorphous carbon films (a-C:H) or DLC (Diamond-Like Carbon) films are well known for exhibiting high electrical resistivity, low dielectric constant, high mechanical hardness, low friction coefficient, low superficial roughness and also for being inert. In this paper, we produced fluorinated DLC films (a-C:F), and studied the effect of adding CF4 on the above-mentioned properties of DLC films. These films were produced by a reactive RF magnetron sputtering system using a target of pure carbon in stable graphite allotrope. We performed measurements of electrical characteristic curves of capacitance as a function of applied tension (C-V) and current as a function of the applied tension (I-V). We showed the dielectric constant (k) and the resistivity (ρ) as functions of the CF4 concentration. On films with 65% CF4, we found that k = 2.7, and on films with 70% CF4, ρ = 12.3 × 1011 Ω cm. The value of the electrical breakdown field to films with 70% CF4 is 5.3 × 106 V/cm.

  19. The effect of alumina and aluminium nitride coating by reactive magnetron sputtering on the resin bond strength to zirconia core

    PubMed Central

    Külünk, Şafak; Baba, Seniha; Öztürk, Özgür; Danişman, Şengül; Savaş, Soner

    2013-01-01

    PURPOSE Although several surface treatments have been recently investigated both under in vitro and in vivo conditions, controversy still exists regarding the selection of the most appropriate zirconia surface pre-treatment. The purpose of this study was to evaluate the effect of alumina (Al) and aluminium nitride (AlN) coating on the shear bond strength of adhesive resin cement to zirconia core. MATERIALS AND METHODS Fifty zirconia core discs were divided into 5 groups; air particle abrasion with 50 µm aluminum oxide particles (Al2O3), polishing + Al coating, polishing + AlN coating, air particle abrasion with 50 µm Al2O3 + Al coating and air particle abrasion with 50 µm Al2O3 + AlN coating. Composite resin discs were cemented to each of specimens. Shear bond strength (MPa) was measured using a universal testing machine. The effects of the surface preparations on each specimen were examined with scanning electron microscope (SEM). Data were statistically analyzed by one-way ANOVA (α=.05). RESULTS The highest bond strengths were obtained by air abrasion with 50 µm Al2O3, the lowest bond strengths were obtained in polishing + Al coating group (P<.05). CONCLUSION Al and AlN coatings using the reactive magnetron sputtering technique were found to be ineffective to increase the bond strength of adhesive resin cement to zirconia core. PMID:24353874

  20. Reactively sputtered nickel nitride as electrocatalytic counter electrode for dye- and quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Soo Kang, Jin; Park, Min-Ah; Kim, Jae-Yup; Ha Park, Sun; Young Chung, Dong; Yu, Seung-Ho; Kim, Jin; Park, Jongwoo; Choi, Jung-Woo; Jae Lee, Kyung; Jeong, Juwon; Jae Ko, Min; Ahn, Kwang-Soon; Sung, Yung-Eun

    2015-05-01

    Nickel nitride electrodes were prepared by reactive sputtering of nickel under a N2 atmosphere at room temperature for application in mesoscopic dye- or quantum dot- sensitized solar cells. This facile and reliable method led to the formation of a Ni2N film with a cauliflower-like nanostructure and tetrahedral crystal lattice. The prepared nickel nitride electrodes exhibited an excellent chemical stability toward both iodide and polysulfide redox electrolytes. Compared to conventional Pt electrodes, the nickel nitride electrodes showed an inferior electrocatalytic activity for the iodide redox electrolyte; however, it displayed a considerably superior electrocatalytic activity for the polysulfide redox electrolyte. As a result, compared to dye-sensitized solar cells (DSCs), with a conversion efficiency (η) = 7.62%, and CdSe-based quantum dot-sensitized solar cells (QDSCs, η = 2.01%) employing Pt counter electrodes (CEs), the nickel nitride CEs exhibited a lower conversion efficiency (η = 3.75%) when applied to DSCs, but an enhanced conversion efficiency (η = 2.80%) when applied to CdSe-based QDSCs.

  1. In situ deposition of PbTiO3 thin films by direct current reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Iljinas, Aleksandras; Marcinauskas, Liutauras; Stankus, Vytautas

    2016-09-01

    The lead titanate thin films were deposited using in situ layer-by-layer reactive magnetron sputtering. The synthesis of films was performed on platinized silicon (Pt/Ti/SiO2/Si) substrates at 450-600 °C temperatures using Ti2O seed layer. The influence of the substrate temperature on the surface morphology, phase composition, and electrical properties of PbTiO3 films were investigated. Experimental results demonstrated that the deposition at higher substrate temperatures resulted in the formation of films with the lower surface roughness values. The increase of the substrate temperature has no effect on the tetragonality value of the films. The preferential orientation in the films was changed and the crystallites size slightly increased with the increased substrate temperature from 450 °C to 550 °C. Hysteresis measurements show that the films exhibit ferroelectric properties with a maximum coercive field of Ec = 150 kV/cm and of Pr = 60 μC/cm2. Coercive field dependence on the frequency measurements indicated that the creep regime of domain wall motions dominated till 1 kHz of frequency.

  2. Optical and chemical properties of mixed-valent rhenium oxide films synthesized by reactive DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Murphy, Neil R.; Gallagher, Regina C.; Sun, Lirong; Jones, John G.; Grant, John T.

    2015-07-01

    Mixed-valent rhenium oxide thin films were deposited using reactive magnetron sputtering employing a metallic rhenium target within an oxygen-argon environment. The oxygen and argon flow rates were systematically varied, while the extinction coefficient, k, of the deposited layers was monitored using in situ spectroscopic ellipsometry. In situ monitoring was used to identify absorption features specific to ReO3, namely, the minimization of k brought on by the gap between interband absorption features in the UV at 310 nm and the onset of free electron absorption at wavelengths above 540 nm. Based on these results, oxygen flow ratios of 50% and 60% were shown to produce films having optical properties characteristic of ReO3, and thus, were selected for detailed ex situ characterization. Chemical analysis via X-ray photoelectron spectroscopy confirmed that all films consisted largely of ReO3, but had some contributions from Re2O3, ReO2 and Re2O7. Additional monitoring of the chemistry, as a function of environmental exposure time, indicated a correlation between structural instability and the presence of Re2O3 and Re2O7 in the films.

  3. Properties of p-type N-doped Cu2O thin films prepared by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Jung, Yu Sup; Choi, Hyung Wook; Kim, Kyung Hwan

    2014-11-01

    We have investigated the electrical, optical, and structural properties of p-type nitrogen (N)-doped Cu2O thin films prepared at various nitrogen gas flow rates for application in heterojunction solar cells. The N-doped Cu2O thin films were fabricated by facing-target reactive sputtering. The hole concentration of the N-doped Cu2O thin films was affected by N2 gas flow rate. With increasing N2 gas flow rate from 0 to 0.5 sccm, the hole concentration and mobility of N-doped Cu2O films increased sharply. The resistivity, hole concentration, and mobility of the N-doped Cu2O films prepared at a N2 gas flow rate of 4 sccm were 1.9 Ω·cm, 2.0 × 1018 cm-3, and 3.4 cm2·V-1·s-1, respectively. The N-doped Cu2O films showed Cu2O(111) and Cu2O(200) diffraction peaks. Cu2O(200) diffraction peak intensity increased slightly with N2 gas flow rate. The Cu2O(200) peaks were stronger at a N2 gas flow rate of 4 sccm than at other gas flow rates.

  4. Effect of thermal annealing on structural, optical and electrical properties of RF reactive magnetron sputtered CdO thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Gadipelly Anil; Ramana Reddy, Musugu; Narasimha Reddy, Katta

    2014-10-01

    Recently, there has been a lot of interest on transparent conducting oxide (TCO) materials which have common application in solar cells and some optoelectronic devices. In this work, cadmium oxide (CdO) thin films have been deposited on glass substrates by RF reactive magnetron sputtering technique and subsequently annealed in air from 200 °C to 500 °C. The effect of annealing temperature on the structural, morphological, optical and electrical properties of CdO films is systematically investigated by X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, UV-visible spectrophotometer and Hall effect measurements. X-ray diffraction (XRD) studies showed that the films are polycrystalline in nature with a preferential orientation along (2 0 0) plane. Atomic force microscopy studies showed that these films are very smooth with maximum root mean square roughness of 3.13 nm. The CdO films formed at annealing temperature of 400 °C exhibited optical transmittance of 84%, electrical resistivity of 1.9 × 10-3 Ω cm and figure of merit of 1.8 × 10-3 Ω-1.

  5. Study on MoO{sub 3-x} films deposited by reactive sputtering for organic light-emitting diodes

    SciTech Connect

    Oka, Nobuto; Watanabe, Hiroki; Sato, Yasushi; Yamaguchi, Hiroshi; Ito, Norihiro; Tsuji, Hiroya; Shigesato, Yuzo

    2010-07-15

    The authors investigate the role of reduced molybdenum trioxide [MoO{sub 3-x} (x{<=}1)] films in organic light-emitting diodes, particularly from the viewpoint of the oxidation state of Mo. MoO{sub 3-x} films were deposited by reactive sputtering under a mixture of argon (Ar) and oxygen (O{sub 2}). The O{sub 2} gas-flow ratio (GFR) [O{sub 2}/(Ar+O{sub 2})] was adjusted between 10% and 100%. Mo with six, five, and four valence electrons was detected in MoO{sub 3-x} film deposited with an O{sub 2} GFR of 10% and 12.5%, whereas, under higher O{sub 2} GFRs, only six valence electrons for Mo in the MoO{sub 3-x} film were detected. N,N{sup '}-di(1-naphthyl)-N,N{sup '}-diphenylbenzidine ({alpha}-NPD) layer, hole-transport material, were deposited over the MoO{sub 3-x} layer by subsequent vacuum evaporation. At the {alpha}-NPD/MoO{sub 3-x} interface, it was found that {alpha}-NPD cations were generated and that MoO{sub 3-x} was reduced, which provided evidence of charge transfer across the interface by Raman spectroscopy and x-ray photoelectron spectroscopy.

  6. SiNx Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering: Process Parameters Influencing the Nitrogen Content.

    PubMed

    Schmidt, Susann; Hänninen, Tuomas; Goyenola, Cecilia; Wissting, Jonas; Jensen, Jens; Hultman, Lars; Goebbels, Nico; Tobler, Markus; Högberg, Hans

    2016-08-10

    Reactive high power impulse magnetron sputtering (rHiPIMS) was used to deposit silicon nitride (SiNx) coatings for biomedical applications. The SiNx growth and plasma characterization were conducted in an industrial coater, using Si targets and N2 as reactive gas. The effects of different N2-to-Ar flow ratios between 0 and 0.3, pulse frequencies, target power settings, and substrate temperatures on the discharge and the N content of SiNx coatings were investigated. Plasma ion mass spectrometry shows high amounts of ionized isotopes during the initial part of the pulse for discharges with low N2-to-Ar flow ratios of <0.16, while signals from ionized molecules rise with the N2-to-Ar flow ratio at the pulse end and during pulse-off times. Langmuir probe measurements show electron temperatures of 2-3 eV for nonreactive discharges and 5.0-6.6 eV for discharges in transition mode. The SiNx coatings were characterized with respect to their composition, chemical bond structure, density, and mechanical properties by X-ray photoelectron spectroscopy, X-ray reflectivity, X-ray diffraction, and nanoindentation, respectively. The SiNx deposition processes and coating properties are mainly influenced by the N2-to-Ar flow ratio and thus by the N content in the SiNx films and to a lower extent by the HiPIMS frequencies and power settings as well as substrate temperatures. Increasing N2-to-Ar flow ratios lead to decreasing growth rates, while the N content, coating densities, residual stresses, and the hardness increase. These experimental findings were corroborated by density functional theory calculations of precursor species present during rHiPIMS.

  7. SiNx Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering: Process Parameters Influencing the Nitrogen Content.

    PubMed

    Schmidt, Susann; Hänninen, Tuomas; Goyenola, Cecilia; Wissting, Jonas; Jensen, Jens; Hultman, Lars; Goebbels, Nico; Tobler, Markus; Högberg, Hans

    2016-08-10

    Reactive high power impulse magnetron sputtering (rHiPIMS) was used to deposit silicon nitride (SiNx) coatings for biomedical applications. The SiNx growth and plasma characterization were conducted in an industrial coater, using Si targets and N2 as reactive gas. The effects of different N2-to-Ar flow ratios between 0 and 0.3, pulse frequencies, target power settings, and substrate temperatures on the discharge and the N content of SiNx coatings were investigated. Plasma ion mass spectrometry shows high amounts of ionized isotopes during the initial part of the pulse for discharges with low N2-to-Ar flow ratios of <0.16, while signals from ionized molecules rise with the N2-to-Ar flow ratio at the pulse end and during pulse-off times. Langmuir probe measurements show electron temperatures of 2-3 eV for nonreactive discharges and 5.0-6.6 eV for discharges in transition mode. The SiNx coatings were characterized with respect to their composition, chemical bond structure, density, and mechanical properties by X-ray photoelectron spectroscopy, X-ray reflectivity, X-ray diffraction, and nanoindentation, respectively. The SiNx deposition processes and coating properties are mainly influenced by the N2-to-Ar flow ratio and thus by the N content in the SiNx films and to a lower extent by the HiPIMS frequencies and power settings as well as substrate temperatures. Increasing N2-to-Ar flow ratios lead to decreasing growth rates, while the N content, coating densities, residual stresses, and the hardness increase. These experimental findings were corroborated by density functional theory calculations of precursor species present during rHiPIMS. PMID:27414283

  8. Characterization of reactively sputtered molybdenum oxide films for solar cell application

    SciTech Connect

    Simchi, H.; Boyle, J. H.; Shafarman, W. N.; McCandless, B. E.; Meng, T.

    2013-07-07

    Molybdenum oxide (MoO{sub 3}) thin films were prepared via Radio Frequency (RF) sputtering at different ambient composition and post-deposition annealing. The effects on the structural, optical, and surface properties of the deposited films were investigated. The ambient oxygen concentration O{sub 2}/(O{sub 2} + Ar) was varied from 10% to 100% at 10 mTorr. Post deposition anneals were performed in Ar at 300-500 Degree-Sign C. The films were analyzed using glancing incidence x-ray diffraction (GIXRD), UV/Vis/NIR spectrophotometry, and x-ray photoelectron spectroscopy (XPS). As-deposited films have amorphous structures, independent of the oxygen partial pressure. Annealing at 300 Degree-Sign C in air resulted in crystallization of the molybdenum oxide films to the monoclinic {beta}-MoO{sub 3} phase. Samples annealed at 400 and 500 Degree-Sign C were identified as pure orthorhombic {alpha}-MoO{sub 3} phase with (020) preferred orientation. High resolution XPS studies showed the presence of Mo{sup 6+} (MoO{sub 3}) and Mo{sup 5+} (Mo{sub 4}O{sub 11}) oxidation states at the surface of as deposited and low temperature (300 Degree-Sign C) annealed films, and the Mo{sup 6+} to Mo{sup 5+} did not change much with deposition oxygen partial pressure. Annealing at 400-500 Degree-Sign C suppressed the oxygen deficiency at the surface, resulting in films with composition close to stoichiometric phases. UV/Vis/NIR spectrophotometry revealed that all films have a high optical transmittance (>80%) in the visible range, followed by a steep drop at {lambda} Almost-Equal-To 400 nm indicating a strong absorption due to band-to-band transition. Increasing the oxygen partial pressure had no significant effect on optical transmittance of the films, and the bandgaps in the range of 2.6 eV to 2.9 eV were obtained. Annealing at 300 Degree-Sign C had a negligible effect on the optical properties of the MoO{sub 3} films, but samples annealed at 400 Degree-Sign C and 500 Degree-Sign C exhibited

  9. Process monitoring during AlN{sub x}O{sub y} deposition by reactive magnetron sputtering and correlation with the film's properties

    SciTech Connect

    Borges, Joel Vaz, Filipe; Marques, Luis; Martin, Nicolas

    2014-03-15

    In this work, AlN{sub x}O{sub y} thin films were deposited by reactive magnetron sputtering, using an aluminum target and an Ar/(N{sub 2}+O{sub 2}) atmosphere. The direct current magnetron discharge parameters during the deposition process were investigated by optical emission spectroscopy and a plasma floating probe was used. The discharge voltage, the electron temperature, the ion flux, and the optical emission lines were recorded for different reactive gas flows, near the target and close to the substrate. This information was correlated with the structural features of the deposits as a first step in the development of a system to control the structure and properties of the films during reactive magnetron sputtering. As the target becomes poisoned, the discharge voltage suffers an important variation, due to the modification of the secondary electron emission coefficient of the target, which is also supported by the evolution of the electron temperature and ion flux to the target. The sputtering yield of the target was also affected, leading to a reduction of the amount of Al atoms arriving to the substrate, according to optical emission spectroscopy results for Al emission line intensity. This behavior, together with the increase of nonmetallic elements in the films, allowed obtaining different microstructures, over a wide range of compositions, which induced different electrical and optical responses of films.

  10. Investigation of the annealing effects on the structural and optoelectronic properties of RF-sputtered ZnO films studied by the Drude-Lorentz model

    NASA Astrophysics Data System (ADS)

    García-Méndez, Manuel; Bedoya-Calle, Álvaro; Segura, Ricardo Rangel; Coello, Víctor

    2015-09-01

    Zinc oxide films were deposited on glass substrates by RF reactive magnetron sputtering and post-annealed in vacuum at 100, 200, and 300 ºC. Structural and optical properties of films were obtained using X-ray diffraction and UV-visible spectroscopy. Optical parameters were extracted from transmittance curves using the single-oscillator Drude-Lorentz model. The evolution of the optical and structural properties of films with the annealing process was investigated. The films crystallized into the hexagonal würzite lattice structure, with preferential growth along the c-axis [0002]. The results indicate that the crystalline quality of films improved with annealing, whereas transparency was reduced from 90 to 80 % at 300 ºC. With post-annealing, the absorption edge shifted to the red, while the optical band gap decreased from to eV because of the Burstein-Moss effect. Calculated values of plasma frequency, fall within the IR range and decrease with temperature, from rad/s () to rad/s ().

  11. Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    NASA Astrophysics Data System (ADS)

    Oka, Nobuto; Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Iwabuchi, Yoshinori; Kotsubo, Hidefumi; Shigesato, Yuzo

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO3 films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO3 films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH3CHO under visible light irradiation. The decomposition time for 60 ppm of CH3CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO3 films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH3CHO.

  12. Visible-light active thin-film WO{sub 3} photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

    SciTech Connect

    Oka, Nobuto Murata, Akiyo; Nakamura, Shin-ichi; Jia, Junjun; Shigesato, Yuzo; Iwabuchi, Yoshinori; Kotsubo, Hidefumi

    2015-10-01

    A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO{sub 3} films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO{sub 3} films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH{sub 3}CHO under visible light irradiation. The decomposition time for 60 ppm of CH{sub 3}CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO{sub 3} films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH{sub 3}CHO.

  13. Self-assembled 3D ZnO porous structures with exposed reactive {0001} facets and their enhanced gas sensitivity.

    PubMed

    Chang, Jin; Ahmad, Muhammad Z; Wlodarski, Wojtek; Waclawik, Eric R

    2013-07-02

    Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2∙g-1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance.

  14. Phase map, composition and resistivity of reactively magnetron sputtered and annealed Ta–N films

    NASA Astrophysics Data System (ADS)

    Salamon, K.; Radić, N.; Bogdanović Radović, I.; Očko, M.

    2016-05-01

    Thin films of tantalum nitride (Ta–N) have been prepared by reactive magnetron deposition under various nitrogen partial pressures p{{\\text{N}}2} (0-1) and subsequently annealed (T a   =  450–950 °C). The structure, density, composition and electrical resistivity of the prepared films were systematically investigated. A p{{\\text{N}}2}-{{T}a} phase map was constructed from the results of structural analysis. With increasing of p{{\\text{N}}2} from 0 to 0.2, a single-phase or two-phase mixture films of tetragonal Ta, Ta2N ({{T}a}≥slant 450 °C), ɛ-TaN ({{T}a}≥slant 850 °C), θ-TaN ({{T}a}≥slant 850 °C) and fcc δ-TaN are sequentially observed. For p{{\\text{N}}2}=0.25 –0.45, the as grown and annealed films exhibit δ-TaN structure. Amorphous films grown in the p{{\\text{N}}2}=0.45 –0.75 range crystallize as cubic Ta2N3 upon annealing at {{T}a}≥slant 650 °C or as δ-TaN at {{T}a}≥slant 850 °C. A cubic Ta2N3 is grown at highest p{{\\text{N}}2} (≥slant 0.85), which decomposes to δ-TaN at {{T}a}≥slant 850 °C. The N     / Ta atomic ratio in the film linearly increases for p{{\\text{N}}2}=0 –0.5, ranging from 0 to 2.1, while the mass density monotonically decreases with p{{\\text{N}}2} . Upon annealing, a part of N atoms out-diffuses from the films deposited at p{{\\text{N}}2}≥slant 0.3 . The electrical resistivity strongly depends on both p{{\\text{N}}2} and T a . However, in the as grown and annealed δ-TaN films the resistivity was of the order of 100–1000 μ Ω cm. In these films, a correlation between the resistivity and the average number of defects (Ta vacancies and N atom excess) is observed. Finally, the influence of thermally introduced oxygen on the films resistivity has been revealed.

  15. Thermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates

    SciTech Connect

    Burmistrova, Polina V.; Rui Koh, Yee; Lundstrom, Mark S.; Maassen, Jesse; Salamat, Shuaib; Favaloro, Tela; Saha, Bivas; Shakouri, Ali; Sands, Timothy D.

    2013-04-21

    Epitaxial ScN(001) thin films were grown on MgO(001) substrates by dc reactive magnetron sputtering. The deposition was performed in an Ar/N{sub 2} atmosphere at 2 Multiplication-Sign 10{sup -3} Torr at a substrate temperature of 850 Degree-Sign C in a high vacuum chamber with a base pressure of 10{sup -8} Torr. In spite of oxygen contamination of 1.6 {+-} 1 at. %, the electrical resistivity, electron mobility, and carrier concentration obtained from a typical film grown under these conditions by room temperature Hall measurements are 0.22 m{Omega} cm, 106 cm{sup 2} V{sup -1} s{sup -1}, and 2.5 Multiplication-Sign 10{sup 20} cm{sup -3}, respectively. These films exhibit remarkable thermoelectric power factors of 3.3-3.5 Multiplication-Sign 10{sup -3} W/mK{sup 2} in the temperature range of 600 K to 840 K. The cross-plane thermal conductivity is 8.3 W/mK at 800 K yielding an estimated ZT of 0.3. Theoretical modeling of the thermoelectric properties of ScN calculated using a mean-free-path of 23 nm at 300 K is in very good agreement with the experiment. These results also demonstrate that further optimization of the power factor of ScN is possible. First-principles density functional theory combined with the site occupancy disorder technique was used to investigate the effect of oxygen contamination on the electronic structure and thermoelectric properties of ScN. The computational results suggest that oxygen atoms in ScN mix uniformly on the N site forming a homogeneous solid solution alloy. Behaving as an n-type donor, oxygen causes a shift of the Fermi level in ScN into the conduction band without altering the band structure and the density of states.

  16. Process controllability of inductively coupled plasma-enhanced reactive sputter deposition for the fabrication of amorphous InGaZnOx channel thin-film transistors

    NASA Astrophysics Data System (ADS)

    Takenaka, Kosuke; Nakata, Keitaro; Otani, Hirofumi; Osaki, Soichiro; Uchida, Giichiro; Setsuhara, Yuichi

    2016-01-01

    The process controllability of inductively coupled plasma-enhanced reactive sputter deposition for the fabrication of amorphous InGaZnOx (a-IGZO) channel thin-film transistors (TFTs) was investigated. a-IGZO film deposition with the addition of H2 gas was performed using a plasma-assisted reactive sputtering system to control the oxidation process during a-IGZO film formation by balancing the oxidation and reduction reactions. Optical emission spectroscopy measurements indicate the possibility for the oxidation reaction to be inhibited by a decrease in the density of oxygen atoms and the reduction effect of hydrogen during a-IGZO film deposition due to the addition of H2 gas. The characteristics of TFTs fabricated using a-IGZO films deposited with a plasma-enhanced magnetron sputtering deposition system were investigated. The results indicate the possibility of expanding the process window by controlling the balance between oxidation and reduction with the addition of H2 gas. TFTs with a-IGZO films that were deposited with the addition of H2 gas exhibited good performance with a field-effect mobility (μFE) of 15.3 cm2 V-1 s-1 and a subthreshold gate voltage swing (S) of 0.48 V decade-1.

  17. ZrO2-ZnO composite thin films for humidity sensing

    NASA Astrophysics Data System (ADS)

    Velumani, M.; Meher, S. R.; Balakrishnan, L.; Sivacoumar, R.; Alex, Z. C.

    2016-05-01

    ZrO2-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO2 phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

  18. Polarity Effects of Substrate Surface in Epitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.; McCarty, P.

    1999-01-01

    Epitaxial ZnO films were grown on the two polar surfaces (0-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films are also deposited on the (000 I) Al203 substrates. It is found that the two polar surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which are strongly inference the epitaxial film growth. The morphology and structure of epitaxial films on the ZnO substrates are different from the film on the Al203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite Surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth using reactive sputtering deposition.

  19. Enhanced quality of epitaxial AlN thin films on 6H-SiC by ultra-high-vacuum ion-assisted reactive dc magnetron sputter deposition

    NASA Astrophysics Data System (ADS)

    Tungasmita, S.; Birch, J.; Persson, P. O. A.˚.; Järrendahl, K.; Hultman, L.

    2000-01-01

    Epitaxial AlN thin films have been grown on 6H-SiC substrates by ultra-high-vacuum (UHV) ion-assisted reactive dc magnetron sputtering. The low-energy ion-assisted growth (Ei=17-27 eV) results in an increasing surface mobility, promoting domain-boundary annihilation and epitaxial growth. Domain widths increased from 42 to 135 nm and strained-layer epitaxy was observed in this energy range. For Ei>52 eV, an amorphous interfacial layer of AlN was formed on the SiC, which inhibited epitaxial growth. Using UHV condition and very pure nitrogen sputtering gas yielded reduced impurity levels in the films (O: 3.5×1018cm-3). Analysis techniques used in this study are in situ reflection high-energy electron diffraction, secondary-ion-mass spectroscopy, atomic-force microscopy, x-ray diffraction, and cross-section high-resolution electron microscopy.

  20. Deposition and characterization of zirconium nitride (ZrN) thin films by reactive magnetron sputtering with linear gas ion source and bias voltage

    NASA Astrophysics Data System (ADS)

    Kavitha, A.; Subramanian, N. Sankara; Loganathan, S.; Kannan, R.

    2014-04-01

    Zirconium nitride thin films have been prepared on stainless steel substrate (304L grade) by reactive cylindrical magnetron sputtering method with Gas Ion Source (GIS) and bias voltage using optimized coating parameters. The structure and surface morphologies of the ZrN films were characterized using X-ray diffraction, atomic microscopy and scanning electron microscopy. The adhesion property of ZrN thin film has been increased due to the GIS. The coating exhibits better adhesion strength up to 10 N whereas the ZrN thin film with bias voltage exhibits adhesion up to 500 mN.

  1. Laser damage resistance of hafnia thin films deposited by electron beam deposition, reactive low voltage ion plating, and dual ion beam sputtering

    SciTech Connect

    Gallais, Laurent; Capoulade, Jeremie; Natoli, Jean-Yves; Commandre, Mireille; Cathelinaud, Michel; Koc, Cian; Lequime, Michel

    2008-05-01

    A comparative study is made of the laser damage resistance of hafnia coatings deposited on fused silica substrates with different technologies: electron beam deposition (from Hf or HfO2 starting material), reactive low voltage ion plating, and dual ion beam sputtering.The laser damage thresholds of these coatings are determined at 1064 and 355 nm using a nanosecond pulsed YAG laser and a one-on-one test procedure. The results are associated with a complete characterization of the samples: refractive index n measured by spectrophotometry, extinction coefficient k measured by photothermal deflection, and roughness measured by atomic force microscopy.

  2. Deposition and characterization of zirconium nitride (ZrN) thin films by reactive magnetron sputtering with linear gas ion source and bias voltage

    SciTech Connect

    Kavitha, A.; Kannan, R.; Subramanian, N. Sankara; Loganathan, S.

    2014-04-24

    Zirconium nitride thin films have been prepared on stainless steel substrate (304L grade) by reactive cylindrical magnetron sputtering method with Gas Ion Source (GIS) and bias voltage using optimized coating parameters. The structure and surface morphologies of the ZrN films were characterized using X-ray diffraction, atomic microscopy and scanning electron microscopy. The adhesion property of ZrN thin film has been increased due to the GIS. The coating exhibits better adhesion strength up to 10 N whereas the ZrN thin film with bias voltage exhibits adhesion up to 500 mN.

  3. Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Pereira, André L. J.; Lisboa Filho, Paulo N.; Acuña, Javier; Brandt, Iuri S.; Pasa, André A.; Zanatta, Antonio R.; Vilcarromero, Johnny; Beltrán, Armando; Dias da Silva, José H.

    2012-06-01

    Oxygen-deficient TiO2 films with enhanced visible and near-infrared optical absorption have been deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is observed that the increase in the absorption coefficient is more effective when the O2 gas supply is periodically interrupted rather than by a decrease of the partial O2 gas pressure in the deposition plasma. The optical absorption coefficient at 1.5 eV increases from about 1 × 102 cm-1 to more than 4 × 103 cm-1 as a result of the gas flow discontinuity. A red-shift of ˜0.24 eV in the optical absorption edge is also observed. High resolution transmission electron microscopy with composition analysis shows that the films present a dense columnar morphology, with estimated mean column width of 40 nm. Moreover, the interruptions of the O2 gas flow do not produce detectable variations in the film composition along its growing direction. X-ray diffraction and micro-Raman experiments indicate the presence of the TiO2 anatase, rutile, and brookite phases. The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films deposited under discontinued O2 gas flow. The increase of optical absorption in the visible and near-infrared regions has been attributed to a high density of defects in the TiO2 films, which is consistent with density functional theory calculations that place oxygen-related vacancy states in the upper third of the optical bandgap. The electronic structure calculation results, along with the adopted deposition method and experimental data, have been used to propose a mechanism to explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic structure are potentially useful concerning the optimization of efficiency of the photocatalytic activity and the magnetic doping of TiO2 films.

  4. Combined optical emission and resonant absorption diagnostics of an Ar-O2-Ce-reactive magnetron sputtering discharge

    NASA Astrophysics Data System (ADS)

    El Mel, A. A.; Ershov, S.; Britun, N.; Ricard, A.; Konstantinidis, S.; Snyders, R.

    2015-01-01

    We report the results on combined optical characterization of Ar-O2-Ce magnetron sputtering discharges by optical emission and resonant absorption spectroscopy. In this study, a DC magnetron sputtering system equipped with a movable planar magnetron source with a Ce target is used. The intensities of Ar, O, and Ce emission lines, as well as the absolute densities of Ar metastable and Ce ground state atoms are analyzed as a function of the distance from the magnetron target, applied DC power, O2 content, etc. The absolute number density of the Arm is found to decrease exponentially as a function of the target-to-substrate distance. The rate of this decrease is dependent on the sputtering regime, which should be due to the different collisional quenching rates of Arm by O2 molecules at different oxygen contents. Quantitatively, the absolute number density of Arm is found to be equal to ≈ 3 × 108 cm- 3 in the metallic, and ≈ 5 × 107 cm- 3 in the oxidized regime of sputtering, whereas Ce ground state densities at the similar conditions are found to be few times lower. The absolute densities of species are consistent with the corresponding deposition rates, which decrease sharply during the transition from metallic to poisoned sputtering regime.

  5. Properties of reactively sputtered oxygenated cadmium sulfide (CdS:O) and their impact on CdTe solar cell performance

    SciTech Connect

    Meysing, Daniel M. Wolden, Colin A.; Griffith, Michelle M.; Mahabaduge, Hasitha; Pankow, Joel; Reese, Matthew O.; Burst, James M.; Rance, William L.; Barnes, Teresa M.

    2015-03-15

    Oxygenated cadmium sulfide (CdS:O) is commonly used as the n-type window layer in high-performance CdTe heterojunction solar cells. This layer is deposited by reactive sputtering, but the optimal amount of oxygen in the sputtering ambient is highly dependent on the specific system and process employed. In this work, the intrinsic properties of CdS:O were measured as a function of the oxygen content (0%–10%) in the sputtering ambient and correlated to device performance with the goal of better defining optimal CdS:O properties for CdTe solar cells. Optimal performance was found using CdS:O films that contained ∼40 at. % oxygen as measured by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy confirmed these results and showed that oxygen is incorporated primarily as oxygenated sulfur compounds (SO{sub x}). Device efficiency improved from 10.5% using CdS to >14% with CdS:O due largely to increases in short-circuit current density as well as a modest improvement in open-circuit voltage. The transparency of the CdS:O films was well correlated with observed improvements in blue quantum efficiency with increasing oxygen content. The optical bandgap of as-deposited CdS:O was identified as a simple metric for process optimization and transfer, with 2.8 eV being ideal for the device architecture employed.

  6. Compositional, morphological and mechanical investigations of monolayer type coatings obtained by standard and reactive magnetron sputtering from Ti, TiB2 and WC

    NASA Astrophysics Data System (ADS)

    Jinga, V.; Mateescu, A. O.; Cristea, D.; Mateescu, G.; Burducea, I.; Ionescu, C.; Crăciun, L. S.; Ghiuţă, I.; Samoilă, C.; Ursuţiu, D.; Munteanu, D.

    2015-12-01

    The purpose of this work was to study new composite coatings that would have wear resistant properties. The coatings were obtained by standard and reactive simultaneous magnetron sputtering from three targets (Ti, TiB2, WC) with or without N2 as reactive gas. The chemical composition of the coatings was investigated by Rutherford backscattering spectrometry, while the morphological features were evaluated by atomic force microscopy. Some of the mechanical properties of the coatings, such as hardness and Young's modulus, were investigated by nanoindentation, while the adherence to the substrate was investigated by scratch tests. The wear resistance and friction coefficients were evaluated using a pin-on-disk tribometer. The films are hard (Hit between 20 and 22 GPa) and show promising results concerning their wear resistance, especially if the films would be paired with an appropriate substrate material.

  7. Co and Cu co-doped ZnO epitaxial films—A magnetically soft nano-composite

    NASA Astrophysics Data System (ADS)

    Ney, V.; Venkataraman, V.; Henne, B.; Ollefs, K.; Wilhelm, F.; Rogalev, A.; Ney, A.

    2016-04-01

    A series of Co/Cu co-doped ZnO epitaxial films has been grown on sapphire substrates to investigate the possibilities of tailoring the magnetic properties in functional ZnO-Co/Cu nano-composites. The growth was performed using reactive magnetron sputtering varying the oxygen partial pressure to tune the incorporation of the dopants and the resulting valence state. At high oxygen pressures, Co2+ is formed and the resulting magnetic properties are very similar to phase pure paramagnetic Co-doped ZnO samples. However, the formation of a secondary CuO phase reduces the overall structural quality of the layers and virtually no substitutional incorporation of Cu2+ in ZnO could be evidenced. At low oxygen pressures, a significant fraction of metallic Co and Cu forming nanometer-sized superparamagnetic precipitates of a Co/Cu alloy can be evidenced which are embedded in a ZnO host matrix.

  8. Growth of residual stress-free ZnO films on SiO{sub 2}/Si substrate at room temperature for MEMS devices

    SciTech Connect

    Singh, Jitendra; Akhtar, Jamil; Ranwa, Sapana; Kumar, Mahesh

    2015-06-15

    ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2”-wafer of SiO{sub 2}/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 10{sup 9} to 11.28 x 10{sup 9} dyne/cm{sup 2} with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ∼3.275 eV to ∼3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications.

  9. Emission intensity of the λ = 1.54 μm line in ZnO films grown by magnetron sputtering, diffusion doped with Ce, Yb, Er

    SciTech Connect

    Mezdrogina, M. M. Eremenko, M. V.; Smirnov, A. N.; Petrov, V. N.; Terukov, E. I.

    2015-08-15

    The effect of the Er{sup 3+}-ion excitation type on the photoluminescence spectra of crystalline ZnO(ZnO〈Ce, Yb, Er〉) films is determined in the cases of resonant (λ = 532 nm, Er{sup 3+}-ion transition from {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} levels to {sup 4}I{sub 15/2}) and non-resonant (λ = 325 nm, in the region near the ZnO band-edge emission) excitation. It is shown that resonant excitation gives rise to lines with various emission intensities, characteristic of the Er{sup 3+}-ion intracenter 4f transition with λ = 1535 nm when doping crystalline ZnO films with three rare-earth ions (REIs, Ce, Yb, Er) or with two impurities (Ce, Er) or (Er, Yb), independently of the measurement temperature (T = 83 and 300 K). The doping of crystalline ZnO films with rare-earth impurities (Ce, Yb, Er) leads to the efficient transfer of energy to REIs, a consequence of which is the intense emission of an Er{sup 3+} ion in the IR spectral region at λ{sub max} = 1535 nm. The kick-out diffusion mechanism is used upon the sequential introduction of impurities into semiconductor matrices and during the postgrowth annealing of the ZnO films under study. The crystalline ZnO films doped with Ce, Yb, Er also exhibit intense emission in the visible spectral region at room temperature, which makes them promising materials for optoelectronics.

  10. A cost-effective growth of SiO(x) thin films by reactive sputtering: photoluminescence tuning.

    PubMed

    Pappas, S D; Grammatikopoulos, S; Poulopoulos, P; Kapaklis, V; Delimitis, A; Trachylis, D; Politis, C

    2011-04-01

    We present a new cost-effective method to produce substoichiometric SiO2 thin films by means of a simple sputter-coater operated at a base pressure of 1 x 10(-3) mbar. During sputtering air is introduced through a fine valve so that the sputtering gas is a mixture of air/Ar. High-resolution electron microscopy shows the formation of amorphous SiO(x) thin films for the as-deposited samples. The index x approaches 1 when the ratio of the partial pressure of air/Ar tends to 0.1. On the other hand, pure silica is formed when the ratio of the partial pressure of air/Ar approaches 0.5. The films in the as-deposited state show intense green-yellow photoluminescence. This fades away with short annealing under air at 950 degrees C. If on the other hand, prolonged annealing is performed under Argon atmosphere at 1000 degrees C, red-infrared photoluminescence is recorded due to the formation of Si nanocrystals embedded in SiO2. This simple method could be suitable for the production of thin SiO(x) films with embedded nanocrystals for optoelectronic or photovoltaic applications. PMID:21776754

  11. Growth of Homoepitaxial ZnO Semiconducting Films

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; George, M. A.; McCarty, P.

    1999-01-01

    As a high temperature wide-band-gap (3.3 eV at room temperature) semiconductor, ZnO has been used for many applications such as wave-guides, solar cells, and surface acoustic wave devices, Since ZnO has a 60 meV excitonic binding energy that makes it possible to produce excitonic lasing at room temperature, a recent surge of interest is to synthesize ZnO films for UV/blue/green laser diodes. These applications require films with a smooth surface, good crystal quality, and low defect density. Thus, homoepitaxial film growth is the best choice. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystal substrates grown by the hydrothermal method are mechanically polished and annealed in air for four hours before the films are deposited. The annealing temperature-dependence on ZnO substrate morphology and electrical properties is investigated. Films are synthesized by off-axis reactive sputtering deposition. This produces films that have very smooth surfaces with roughness less than or equal to 5 nm on a 5 microns x 5 microns area. The full width at half maximum of film theta rocking curves measured by the x-ray diffraction is slightly larger than that of the crystal substrate. Films are also characterized by measuring resistivity, optical transmittance, and photoluminescence. The properties of ZnO films grown on (0001) ZnO and (0001) sapphire substrates will also be compared and discussed.

  12. Effect of W-Ti target composition on the surface chemistry and electronic structure of WO3-TiO2 films made by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Vargas, M.; Lopez, D. M.; Murphy, N. R.; Grant, J. T.; Ramana, C. V.

    2015-10-01

    Tungsten-titanium (W-Ti) mixed oxide thin films were fabricated using reactive sputtering of W-Ti alloy targets with Ti content ranging from 0 to 30 wt%. The effect of target composition on film structure, surface/interface chemistry and chemical valence state of the W and Ti cations was investigated in detail. All films were amorphous in nature as confirmed by X-ray diffraction analyses. For growth times of 1 h, the thicknesses of the W-Ti-O films decreased significantly from 150 to 35 nm with increasing Ti content in the target, confirming that the oxide film growth behavior is dependent on the sputter-target composition. The chemistry and composition of the films probed using X-ray photoelectron spectroscopy (XPS) confirms the existence of W and Ti in their highest oxidation states of 6+ and 4+, respectively. Quantification of binding energy shifts for W and Ti core-level transitions confirms the formation of WO3-TiO2 composite oxide films. Depth profiles confirm and validate film uniformity, as well as film thickness differences and variable oxidation behavior of W and Ti in the films.

  13. Results on the electrochromic and photocatalytic properties of vanadium doped tungsten oxide thin films prepared by reactive dc magnetron sputtering technique

    NASA Astrophysics Data System (ADS)

    Muthu Karuppasamy, K.; Subrahmanyam, A.

    2008-02-01

    In this investigation, vanadium doped tungsten oxide (V : WO3) thin films are prepared at room temperature by reactive dc magnetron sputtering employing a tungsten-vanadium 'inlay' target. In comparison with pure sputtered tungsten oxide thin films, 11% vanadium doping is observed to decrease the optical band gap, enhance the colour neutral property, decrease the coloration efficiency (from 121 to 13 cm2 C-1), increase the surface work function (4.68-4.83 eV) and significantly enhance the photocatalytic efficiency in WO3 thin films. These observations suggest that (i) vanadium creates defect levels that are responsible for optical band gap reduction, (ii) multivalent vanadium bonding with terminal oxygen in the WO3 lattice gives rise to localized covalent bonds and thus results in an increase in the work function, and (iii) a suitable work function of V : WO3 with ITO results in an enhancement of the photocatalytic activity. These results on electrochromic and photocatalytic properties of V : WO3 thin films show good promise in the low maintenance window application.

  14. Effect of O{sub 2} flow ratio on the microstructure and stress of room temperature reactively sputtered RuO{sub x} thin films

    SciTech Connect

    Shi Junxia; Huang Feng; Weaver, Mark L.; Klein, Tonya M.

    2005-05-01

    RuO{sub x} thin films were deposited at room temperature by reactive radio frequency magnetron-sputtering using Ar/O{sub 2} discharges of varying O{sub 2} flow ratio (f{sub O{sub 2}}) over the range 10%-50% and were characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, resistivity, and stress-temperature measurements. With the increase of f{sub O{sub 2}}, the film texture changed from (110) to (101). Films deposited with f{sub O{sub 2}}>25% were determined stoichiometric. The residual stresses in as-deposited films were all compressive and increased with addition of O{sub 2}, except for the film sputtered at f{sub O{sub 2}}=20% which was in biaxial tension. The film deposited at f{sub O{sub 2}}=30% had a low resistivity value of 68 {mu}{omega} cm and near zero stress (<50 MPa tensile) after a thermal cycle in air up to 500 deg. C which is promising for use in microdevices.

  15. Effect of Substrate Bias Voltage on the Physical Properties of Zirconium Nitride (ZrN) Films Deposited by Mid Frequency Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Kavitha, A.; Kannan, R.; Loganathan, S.

    2014-05-01

    Present work involves the preparation of Zirconium Nitride thin films on stainless steel (SS) (304L grade) substrate by reactive cylindrical magnetron sputtering method. The X-ray diffraction (XRD) profile of the ZrN thin films prepared with different bias voltage conforms face centered cubic structure with preferred orientation along the (111) plane at lower bias voltage (100 V) and at higher bias voltage (300 V) the preferred orientation shifted to (220) plane. The influences of bias voltage on the thickness and microhardness ZrN thin films have been studied. ZrN thin film sputtered with 300 V bias voltage shows the maximum reflectance of 90% at a wavelength of 1000 nm. The coated substrates have been found to exhibit improved corrosion resistance compared to the SS plate. The root mean square surface roughness and surface morphology were investigated from 3D atomic force microscope (AFM) images and scanning electron microscope (SEM), which indicate smooth and uniform surface pattern without any pin holes.

  16. Growth of (Sr,La)-(Ta,Ti)-O-N perovskite oxide and oxynitride films by radio frequency magnetron sputtering: Influence of the reactive atmosphere on the film structure

    NASA Astrophysics Data System (ADS)

    Le Paven, C.; Le Gendre, L.; Benzerga, R.; Cheviré, F.; Tessier, F.; Jacq, S.; Traoré-Mantion, S.; Sharaiha, A.

    2015-03-01

    In the search for new dielectric and ferroelectric compounds, we were interested in the perovskite (Sr1-xLax)2(Ta1-xTix)2O7 solid solution with ferroelectric end members Sr2Ta2O7 (TCurie=-107 °C) and La2Ti2O7 (TCurie=1461 °C). In order to achieve a Curie temperature close to room temperature, the formulation with x=0.01 was chosen and synthetized as thin films by reactive radio-frequency magnetron sputtering. In oxygen rich plasma, a (Sr0.99La0.01)2(Ta0.99Ti0.01)2O7 film is deposited, characterized by a band-gap Eg=4.75 eV and an (1 1 0) epitaxial growth on (0 0 1)MgO substrate. The use of nitrogen rich plasma allows to synthesize (Sr0.99La0.01)(Ta0.99Ti0.01)O2N oxynitride films, with band gap Eg~2.10 eV and a polycrystalline, textured or epitaxial growth on (0 0 1)MgO substrate. Nitrogen-substoichiometric oxynitride films with larger lattice cells are produced for low dinitrogen percentages in the sputtering plasma.

  17. Research Update: Reactively sputtered nanometer-thin ZrN film as a diffusion barrier between Al and boron layers for radiation detector applications

    NASA Astrophysics Data System (ADS)

    Golshani, Negin; Mohammadi, V.; Schellevis, H.; Beenakker, C. I. M.; Ishihara, R.

    2014-10-01

    In this paper, optimization of the process flow for PureB detectors is investigated. Diffusion barrier layers between a boron layer and the aluminum interconnect can be used to enhance the performance and visual appearance of radiation detectors. Few nanometers-thin Zirconium Nitride (ZrN) layer deposited by reactive sputtering in a mixture of Ar/N2, is identified as a reliable diffusion barrier with better fabrication process compatibility than others. The barrier properties of this layer have been tested for different boron layers deposited at low and high temperatures with extensive optical microscopy analyses, electron beam induced current, SEM, and electrical measurements. This study demonstrated that spiking behavior of pure Al on Si can be prevented by the thin ZrN layer thus improving the performance of the radiation detectors fabricated using boron layer.

  18. Semiconducting ZnSn{sub x}Ge{sub 1−x}N{sub 2} alloys prepared by reactive radio-frequency sputtering

    SciTech Connect

    Shing, Amanda M.; Coronel, Naomi C.; Lewis, Nathan S.; Atwater, Harry A.

    2015-07-01

    We report on the fabrication and structural and optoelectronic characterization of II-IV-nitride ZnSn{sub x}Ge{sub 1−x}N{sub 2} thin-films. Three-target reactive radio-frequency sputtering was used to synthesize non-degenerately doped semiconducting alloys having <10% atomic composition (x = 0.025) of tin. These low-Sn alloys followed the structural and optoelectronic trends of the alloy series. Samples exhibited semiconducting properties, including optical band gaps and increasing in resistivities with temperature. Resistivity vs. temperature measurements indicated that low-Sn alloys were non-degenerately doped, whereas alloys with higher Sn content were degenerately doped. These films show potential for ZnSn{sub x}Ge{sub 1−x}N{sub 2} as tunable semiconductor absorbers for possible use in photovoltaics, light-emitting diodes, or optical sensors.

  19. Stress-induced VO{sub 2} films with M2 monoclinic phase stable at room temperature grown by inductively coupled plasma-assisted reactive sputtering

    SciTech Connect

    Okimura, Kunio; Watanabe, Tomo; Sakai, Joe

    2012-04-01

    We report on growth of VO{sub 2} films with M2 monoclinic phase stable at room temperature under atmospheric pressure. The films were grown on quartz glass and Si substrates by using an inductively coupled plasma-assisted reactive sputtering method. XRD-sin{sup 2}{Psi} measurements revealed that the films with M2 phase are under compressive stress in contrast to tensile stress of films with M1 phase. Scanning electron microscopy observations revealed characteristic crystal grain aspects with formation of periodical twin structure of M2 phase. Structural phase transition from M2 to tetragonal phases, accompanied by a resistance change, was confirmed to occur as the temperature rises. Growth of VO{sub 2} films composed of M2 phase crystalline is of strong interest for clarifying nature of Mott transition of strongly correlated materials.

  20. Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering

    NASA Astrophysics Data System (ADS)

    Klewe, C.; Meinert, M.; Boehnke, A.; Kuepper, K.; Arenholz, E.; Gupta, A.; Schmalhorst, J.-M.; Kuschel, T.; Reiss, G.

    2014-03-01

    We fabricated NiFe2O4 thin films on MgAl2O4 (001) substrates by reactive dc magnetron co-sputtering in a pure oxygen atmosphere at different substrate temperatures. The film properties were investigated by various techniques with a focus on their structure, surface topography, magnetic characteristics, and transport properties. Structural analysis revealed a good crystallization with epitaxial growth and low roughness and a similar quality as in films grown by pulsed laser deposition. Electrical conductivity measurements showed high room temperature resistivity (12 Ω m), but low activation energy, indicating an extrinsic transport mechanism. A band gap of about 1.55 eV was found by optical spectroscopy. Detailed x-ray spectroscopy studies confirmed the samples to be ferrimagnetic with fully compensated Fe moments. By comparison with multiplet calculations of the spectra, we found that the cation valencies are to a large extent Ni2+ and Fe3+.

  1. Effect of nitrogen flow ratios on the structure and mechanical properties of (TiVCrZrY)N coatings prepared by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Tsai, Du-Cheng; Huang, Yen-Lin; Lin, Sheng-Ru; Liang, Shih-Chang; Shieu, Fuh-Sheng

    2010-12-01

    This study reports the influence of growth conditions on the characteristics of (TiVCrZrY)N coatings prepared by reactive magnetron sputtering at various N 2-to-total (N 2 + Ar) flow ratio, which is R N. The crystal structures, microstructure, and mechanical properties for different R N were characterized by electron spectroscopy for chemical analysis, X-ray diffraction, atomic force microscopy, field-emission-scanning electron microscopy, transmission electron microscopy, and nanoindentation. The results indicate that the TiVCrZrY alloy and nitride coatings have hexagonal close-packed (hcp)-type and sodium chloride (NaCl)-type solid-solution structures, respectively. The voids in the coatings are eliminated and the growth of the columnar crystal structures is inhibited along with an increasing R N. As a consequence, highly packed equiaxed amorphous structures with smooth surfaces are formed. The coatings accordingly achieved a pronounce hardness of 17.5 GPa when R N = 100%.

  2. Research Update: Reactively sputtered nanometer-thin ZrN film as a diffusion barrier between Al and boron layers for radiation detector applications

    SciTech Connect

    Golshani, Negin Mohammadi, V.; Schellevis, H.; Beenakker, C. I. M.; Ishihara, R.

    2014-10-01

    In this paper, optimization of the process flow for PureB detectors is investigated. Diffusion barrier layers between a boron layer and the aluminum interconnect can be used to enhance the performance and visual appearance of radiation detectors. Few nanometers-thin Zirconium Nitride (ZrN) layer deposited by reactive sputtering in a mixture of Ar/N{sub 2}, is identified as a reliable diffusion barrier with better fabrication process compatibility than others. The barrier properties of this layer have been tested for different boron layers deposited at low and high temperatures with extensive optical microscopy analyses, electron beam induced current, SEM, and electrical measurements. This study demonstrated that spiking behavior of pure Al on Si can be prevented by the thin ZrN layer thus improving the performance of the radiation detectors fabricated using boron layer.

  3. Photocatalytic activities of wet oxidation synthesized ZnO and ZnO-TiO2 thick porous films

    NASA Astrophysics Data System (ADS)

    Chen, Ruiqun; Han, Jie; Yan, Xiaodong; Zou, Chongwen; Bian, Jiming; Alyamani, Ahmed; Gao, Wei

    2011-05-01

    Highly porous zinc oxide (ZnO) film was produced by using reactive magnetron sputtering zinc target followed by wet oxidation. Titanium dioxide (TiO2) was mixed to the porous films by using either TiO2 target magnetron sputter deposition or sol-spin method. The film thickness could reach 50 μm with uniform porosity. On the sputtering prepared ZnO-TiO2 film surface, fine nanorods with small anatase TiO2 nano-clusters on the tips were observed by SEM and TEM, and the titanium (Ti) composition was determined by XPS as 0.37%. The sol-spin treatment could increase the Ti composition to 4.9%, with reduced pore size compared to the untreated ZnO porous film. Photoluminescence measurements showed that the Ti containing porous film has strong ultraviolet-visible light emission. In the photo-catalysis testing, ZnO and ZnO-TiO2 have similar photo-catalysis activity under 365 nm UV irradiation, but under visible light, the photocatalysis activities of ZnO-TiO2 films were twice higher than that of ZnO porous film, implying promising applications of this porous oxide composite for industrial and dairy farm wastewater treatment.

  4. Reactive magnetron sputter deposition of (Ti,Cu)N nano-crystalline thin films: modeling of particle and energy flux toward the substrate

    NASA Astrophysics Data System (ADS)

    Rahmati, A.

    2012-08-01

    Ternary (Ti,Cu)N thin films were deposited by reactive dc magnetron sputtering on Si (111), glass slide, quartz and potassium bromide (KBr) substrates in molecular nitrogen ambient. This work has provided insight into the effects of substrate temperature, nitrogen content and particle and energy flux toward the substrate on the characteristics of (Ti,Cu)N films. Structural analysis of the films was identified by the x-ray diffraction (XRD) technique. Crystalline quality and phase stability are strongly dependent on substrate temperature. Ti-accommodated Cu3N structure results in lattice constant expansion and (100) preferential orientation. The bonding environment in these films was obtained by Fourier transform infrared (FTIR) spectroscopy. The surface morphology and chemical composition of the films were studied by using a scanning electron microscope (SEM)/energy dispersive x-ray spectroscopy (EDX). The films were aggregated as spherical grains. The atomic titanium to copper (Ti : Cu) ratio of (Ti,Cu)N films was less than that of the original target. An optical study was performed by vis-near-IR transmittance spectroscopy. The film thickness, refractive index and extinction coefficient were extracted from the measured transmittance. The as-deposited (Ti,Cu)N films are direct semiconductors with bandgap energy in the range of 2.57-3.23 eV. Nitrogen richness acts as an acceptor center and injects holes into the valence band (excited semiconductor). The amount of N attracted by the films was calculated using a model based on chemical bonding and the solubility process. Energy and angular contributions of sputtering yield were extracted from the existing literature to obtain a prediction about the atomic Ti : Cu ratio. By means of transport and range of ions in matter (TRIM.SP) Monte-Carlo simulation, the particle reflection coefficient of reflected N-neutrals was calculated. The initial energy of reflected N-neutrals and the sputtered particle at the

  5. Photoelectron spectroscopic and electronic structure studies of CH(2)O bonding and reactivity on ZnO surfaces: steps in the methanol synthesis reaction.

    PubMed

    Jones, P M; May, J A; Reitz, J B; Solomon, Edward I

    2004-05-31

    Adsorption of CH(2)O on ZnO(0001) has been investigated using XPS, NEXAFS, variable-energy photoelectron spectroscopy (PES), and density functional theory (DFT) calculations. CH(2)O is chemisorbed on the (0001) surface at 130 K. Its C1s XPS peak position at 292.7 eV and NEXAFS sigma shape resonance at 302.6 eV are consistent with an eta(1) bound surface geometry. Geometry optimized DFT calculations also indicate that CH(2)O is bound to the Zn(II) site in an eta(1) configuration through its oxygen atom. The variable-energy PES of the eta(1) bound CH(2)O/ZnO(0001) complex exhibits four valence band features at 21.2, 16.4, 13.8, and 10.7 eV below the vacuum level providing an experimental and theoretical description of this surface interaction. Annealing the ZnO(0001)/CH(2)O surface complex to 220 K decomposes the chemisorbed CH(2)O, producing formyl (291.5 eV), methoxide (290.2 eV), and formate (293.6 eV) intermediates. Thus this reaction coordinate involves the conversion of an oxygen bound formaldehyde to a carbon bound formyl species on ZnO(0001). Only formate is formed on the ZnO(100) surface. DFT is used to explore surface intermediates and the transition state in the methanol synthesis reaction (MSR). The bonding interactions of H(2), CO, CH(3)O(-), HCO(-), and trans-HCOH to the ZnO(0001) surface are elucidated using geometry optimization. H(2) was found to be heterolytically cleaved on the ZnO(0001) surface, and carbon monoxide, formyl, and methoxide are calculated to be eta(1) bound. These results are consistent with observed metal oxide surface reactivity where heterolytic bond cleavage is dominant. The oxygen atom in the bound formyl was found to be activated for attack by a proton. This results in the planar eta(1) bound trans-HCOH surface species. The transition state in the gas phase rearrangement of trans-HCOH to formaldehyde was calculated to have a barrier of 31 kcal/mol. The correlation diagram for this rearrangement in the gas phase indicates that

  6. Influence of substrate bias voltage on structural and optical properties of RF reactive magnetron sputtered WO3 thin films

    NASA Astrophysics Data System (ADS)

    Madhavi, V.; Kondaiah, P.; Uthanna, S.

    2012-11-01

    In this investigation, tungsten oxide (WO3) thin films have been deposited on unheated glass substrates by RF magnetron sputtering of tungsten target at constant oxygen partial pressure of 6×10-2 Pa, sputtering power of 150 W and at different substrate bias voltages in the range from 0 to -150 V. The structural and optical properties of the films were investigated by using X-ray diffraction, Fourier transform infrared spectroscopy and UV-Vis-NIR spectrophotometers. The films formed up to substrate bias voltage of -50 V were found to be amorphous in nature, while those films formed at -100 V showed a weak (200) reflection indicates the presence of monoclinic phase of WO3 in amorphous matrix. The optical transmittance of the films was in the range 78 - 95 % in the wavelength range of 500 - 1200 nm. The absorption band edge was shifted towards higher wavelength side with increasing substrate bias voltage. The optical band gap of the films decrease from 2.81 to 2.69 eV with increase of substrate bias voltage from 0 to -150 V respectively. The refractive index of the films increased from 2.19 to 2.27 with increase of substrate bias voltage from 0 to -150 V respectively.

  7. Influence of surface defects in ZnO thin films on its biosensing response characteristic

    SciTech Connect

    Saha, Shibu; Gupta, Vinay

    2011-09-15

    Highly c-axis oriented zinc oxide (ZnO) thin films deposited by rf magnetron sputtering under varying processing pressure (20-50 mT) in a reactive gas mixture of argon and oxygen were studied for biosensing application. The as-deposited ZnO thin films were in a state of compressive stress having defects related to interstitial Zn and antisite oxygen. Glucose oxidase has been chosen as the model enzyme in the present study and was immobilized on the surface of ZnO thin films deposited on indium tin oxide coated Corning Glass substrate. The studies reveal a correlation between the biosensing characteristic and the presence of defects in the ZnO films. The ZnO films deposited under high pressure (50 mT) are found to be more sensitive for biosensing application due to availability of more surface area for effective immobilization of biomolecules and exhibits a suitable microenvironment with good electron transfer characteristic. The obtained results highlight the importance of desired microstate besides availability of suitable native defects in the ZnO thin film for exhibiting enhanced biosensing response.

  8. Effect of RF power on the optical, electrical, mechanical and structural properties of sputtering Ga-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Tien, Chuen-Lin; Yu, Kuo-Chang; Tsai, Tsung-Yo; Liu, Ming-Chung

    2015-11-01

    We present the influences of radio-frequency (RF) power on the optical, electrical, mechanical, and structural properties of Ga-doped zinc oxide (GZO) thin films by RF magnetron sputtering at room temperature. GZO thin films were grown on unheated glass and silicon substrates using radio-frequency (RF) magnetron sputtering method with different RF powers (from 60 W to 160 W). The optical properties of the GZO thin film were determined by a UV-vis spectrophotometer. The residual stress in GZO films were measured by a home-made Twyman-Green interferometer with the fast Fourier transform (FFT) method. The surface roughness of GZO films were measured by a microscopic interferometry. The microstructure, composition and crystal orientation of the GZO films were determined by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). This paper revealed that the optical, electrical, mechanical, and structural properties of GZO thin film are subject to the RF power. For the optical spectrum measurement, an average optical transmittance in the visible region of the spectra of 85% was obtained. For the characteristic measurements, all the GZO thin films deposited by RF magnetron sputtering have compressive stress at different RF powers. A minimum residual stress of 0.24 GPa is found at the RF power of 140 W. A four-point probe method was used to measure the resistivity of the GZO thin films with different powers, the results indicate that the resistivity increases with increasing of RF power. In addition, the root-mean-square (RMS) surface roughness of GZO thin films slightly increases as the RF power is increasing. We have also compared the results with the relevant literatures.

  9. Study on the electrical properties of ZnO thin film transistors using pyrochlore Bi1.5Zn(1+y)Nb1.5O(7+y) gate insulators fabricated by RF sputtering

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Ren, Wei; Shi, Peng; Jiang, Zhuangde

    2016-06-01

    A series of ZnO thin film transistors (TFTs) using pyrochlore Bi1.5ZnNb1.5O (BZN) thin films as gate insulators by RF sputtering has been fabricated. The relations between the zinc content and performance of BZN thin films and ZnO-TFTs are studied. The electrical properties of the ZnO-TFTs with BZN gate insulators as a function of Zn content are discussed. The research results showed that excess Zn (5 mol.%) can significantly enhance the performance of BZN thin films and ZnO-TFTs, which is mainly attributed to the compensation of Zn volatility during fabrication of BZN thin films. At an applied electric field of 250 kV/cm, the leakage current density of BZN thin films with 5 mol.% excess Zn is approximately four order of magnitude lower than that of BZN thin films without excess Zn. The subthreshold and surface state density of ZnO-TFTs were decreased from 684 and 350 mV/dec to 4.5×1012 and 2×1012 cm-2, respectively, as Zn content was increased.

  10. Amorphous indium-tin-zinc oxide films deposited by magnetron sputtering with various reactive gases: Spatial distribution of thin film transistor performance

    SciTech Connect

    Jia, Junjun; Torigoshi, Yoshifumi; Shigesato, Yuzo; Kawashima, Emi; Utsuno, Futoshi; Yano, Koki

    2015-01-12

    This work presents the spatial distribution of electrical characteristics of amorphous indium-tin-zinc oxide film (a-ITZO), and how they depend on the magnetron sputtering conditions using O{sub 2}, H{sub 2}O, and N{sub 2}O as the reactive gases. Experimental results show that the electrical properties of the N{sub 2}O incorporated a-ITZO film has a weak dependence on the deposition location, which cannot be explained by the bombardment effect of high energy particles, and may be attributed to the difference in the spatial distribution of both the amount and the activity of the reactive gas reaching the substrate surface. The measurement for the performance of a-ITZO thin film transistor (TFT) also suggests that the electrical performance and device uniformity of a-ITZO TFTs can be improved significantly by the N{sub 2}O introduction into the deposition process, where the field mobility reach to 30.8 cm{sup 2} V{sup –1} s{sup –1}, which is approximately two times higher than that of the amorphous indium-gallium-zinc oxide TFT.

  11. Effects of Substrate Bias on the Hardness and Resistivity of Reactively Sputtered TaN and TiN Thin Films

    NASA Astrophysics Data System (ADS)

    Lu, Junqing; Arshi, Nishat

    2016-06-01

    TaN and TiN films are being widely used as conductive layers in electronic devices or protective coatings on metal surfaces. Among various deposition methods, reactive magnetron sputtering is preferred partly due to its ability to control the energy of the depositing ions by applying different substrate bias voltages. In this study, TaN and TiN films were deposited on Si/SiO2 substrates by using direct current magnetron sputtering technique with 370 W target power at 1.9 mTorr and under different substrate biases. The effects of the substrate bias on both the resistivity and the hardness of the deposited TaN and TiN films were investigated. The phase and composition of the deposited films were investigated by x-ray diffraction, the resistivity was measured by a four-point probe, and the hardness was obtained by nano-indentation. For TaN films, the use of substrate bias not only increased the hardness but also increased the resistivity. Moreover, the formation of the Ta3N5 phase at the -300 V substrate bias significantly increased the TaN film resistivity. For TiN films, the optimum resistivity (minimum) of 19.5 µΩ-cm and the hardness (maximum) of 31.5 GPa were achieved at the -100 V substrate bias. Since the phase changes occurred in both the TaN and the TiN films at higher substrate biases and these phase changes negatively affected the resistivity or hardness property of the films, the substrate bias should not significantly exceed -100 V.

  12. Morphology and structure evolution of Cu(In,Ga)S{sub 2} films deposited by reactive magnetron co-sputtering with electron cyclotron resonance plasma assistance

    SciTech Connect

    Nie, Man Ellmer, Klaus

    2014-02-28

    Cu(In,Ga)S{sub 2} (CIGS) films were deposited on Mo coated soda lime glass substrates using an electron cyclotron resonance plasma enhanced one-step reactive magnetron co-sputtering process (ECR-RMS). The crystalline quality and the morphology of the Cu(In,Ga)S{sub 2} films were investigated by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and X-ray fluorescence. We also compared these CIGS films with films previously prepared without ECR assistance and find that the crystallinity of the CIGS films is correlated with the roughness evolution during deposition. Atomic force microscopy was used to measure the surface topography and to derive one-dimensional power spectral densities (1DPSD). All 1DPSD spectra of CIGS films exhibit no characteristic peak which is typical for the scaling of a self-affine surface. The growth exponent β, characterizing the roughness R{sub q} evolution during the film growth as R{sub q} ∼ d{sup β}, changes with film thickness. The root-mean-square roughness at low temperatures increases only slightly with a growth exponent β = 0.013 in the initial growth stage, while R{sub q} increases with a much higher exponent β = 0.584 when the film thickness is larger than about 270 nm. Additionally, we found that the H{sub 2}S content of the sputtering atmosphere and the Cu- to-(In + Ga) ratio has a strong influence of the morphology of the CIGS films in this one-step ECR-RMS process.

  13. Combinatorial Reactive Sputtering of In2S3 as an Alternative Contact Layer for Thin Film Solar Cells.

    PubMed

    Siol, Sebastian; Dhakal, Tara P; Gudavalli, Ganesh S; Rajbhandari, Pravakar P; DeHart, Clay; Baranowski, Lauryn L; Zakutayev, Andriy

    2016-06-01

    High-throughput computational and experimental techniques have been used in the past to accelerate the discovery of new promising solar cell materials. An important part of the development of novel thin film solar cell technologies, that is still considered a bottleneck for both theory and experiment, is the search for alternative interfacial contact (buffer) layers. The research and development of contact materials is difficult due to the inherent complexity that arises from its interactions at the interface with the absorber. A promising alternative to the commonly used CdS buffer layer in thin film solar cells that contain absorbers with lower electron affinity can be found in β-In2S3. However, the synthesis conditions for the sputter deposition of this material are not well-established. Here, In2S3 is investigated as a solar cell contact material utilizing a high-throughput combinatorial screening of the temperature-flux parameter space, followed by a number of spatially resolved characterization techniques. It is demonstrated that, by tuning the sulfur partial pressure, phase pure β-In2S3 could be deposited using a broad range of substrate temperatures between 500 °C and ambient temperature. Combinatorial photovoltaic device libraries with Al/ZnO/In2S3/Cu2ZnSnS4/Mo/SiO2 structure were built at optimal processing conditions to investigate the feasibility of the sputtered In2S3 buffer layers and of an accelerated optimization of the device structure. The performance of the resulting In2S3/Cu2ZnSnS4 photovoltaic devices is on par with CdS/Cu2ZnSnS4 reference solar cells with similar values for short circuit currents and open circuit voltages, despite the overall quite low efficiency of the devices (∼2%). Overall, these results demonstrate how a high-throughput experimental approach can be used to accelerate the development of contact materials and facilitate the optimization of thin film solar cell devices.

  14. Combinatorial Reactive Sputtering of In2S3 as an Alternative Contact Layer for Thin Film Solar Cells.

    PubMed

    Siol, Sebastian; Dhakal, Tara P; Gudavalli, Ganesh S; Rajbhandari, Pravakar P; DeHart, Clay; Baranowski, Lauryn L; Zakutayev, Andriy

    2016-06-01

    High-throughput computational and experimental techniques have been used in the past to accelerate the discovery of new promising solar cell materials. An important part of the development of novel thin film solar cell technologies, that is still considered a bottleneck for both theory and experiment, is the search for alternative interfacial contact (buffer) layers. The research and development of contact materials is difficult due to the inherent complexity that arises from its interactions at the interface with the absorber. A promising alternative to the commonly used CdS buffer layer in thin film solar cells that contain absorbers with lower electron affinity can be found in β-In2S3. However, the synthesis conditions for the sputter deposition of this material are not well-established. Here, In2S3 is investigated as a solar cell contact material utilizing a high-throughput combinatorial screening of the temperature-flux parameter space, followed by a number of spatially resolved characterization techniques. It is demonstrated that, by tuning the sulfur partial pressure, phase pure β-In2S3 could be deposited using a broad range of substrate temperatures between 500 °C and ambient temperature. Combinatorial photovoltaic device libraries with Al/ZnO/In2S3/Cu2ZnSnS4/Mo/SiO2 structure were built at optimal processing conditions to investigate the feasibility of the sputtered In2S3 buffer layers and of an accelerated optimization of the device structure. The performance of the resulting In2S3/Cu2ZnSnS4 photovoltaic devices is on par with CdS/Cu2ZnSnS4 reference solar cells with similar values for short circuit currents and open circuit voltages, despite the overall quite low efficiency of the devices (∼2%). Overall, these results demonstrate how a high-throughput experimental approach can be used to accelerate the development of contact materials and facilitate the optimization of thin film solar cell devices. PMID:27173477

  15. [Effects of Temperature on the Preparation of Al/Zn3N2 Thin Films Using Magnetron Reactive Sputtering].

    PubMed

    Feng, Jun-qin; Chen, Jun-fang

    2015-08-01

    The effects of substrate temperature on the plasma active species were investigated by plasma optical emission spectroscopy. With increasing substrate temperature, the characteristic spectroscopy intensity of the first positive series of N2* (B(3)Πg-->A(3)Σu(+)), the second positive N2* (C(3)Πu-->B(3)Πg), the first negative series N2(+)* (B(2)Σu(+)-->X(2)Σg(+)) and Zn* are increased. Due to the substrate temperature, each ion kinetic energy is increased and the collision ionization intensified in the chamber. That leading to plasma ion density increase. These phenomenons's show that the substrate temperature raises in a certain range was conducive to zinc nitride thin films growth. Zn3N2 thin films were prepared on Al films using ion sources-assisted magnetron sputtering deposition method. The degree of crystalline of the films was examined with X-ray diffraction (XRD). The results show that has a dominant peak located at 34.359° in room temperature, which was corresponding to the (321) plane of cubic anti-bixbyite zinc nitride structure (JCPDS Card No35-0762). When the substrate temperature was 100 °C, in addition to the (321) reflection, more diffraction peaks appeared corresponding to the (222), (400) and (600) planes, which were located at 31.756°, 36.620° and 56.612° respectively. When the substrate temperature was 200 °C, in addition to the (321), (222), (400) and (600) reflection, more new diffraction peaks also appeared corresponding to the (411), (332), (431) and (622) planes, which were located at 39.070, 43.179°, 47.004° and 62.561° respectively. These results show the film crystalline increased gradually with raise the substrate temperature. XP-1 profilometer were used to analyze the thickness of the Zn3N2 films. The Zn3N2 films deposited on Al films in mixture gas plasma had a deposition rate of 2.0, 2.2, and 2.7 nm · min(-1). These results indicate that the deposition rate was gradually enhanced as substrate temperature increased

  16. [Effects of Temperature on the Preparation of Al/Zn3N2 Thin Films Using Magnetron Reactive Sputtering].

    PubMed

    Feng, Jun-qin; Chen, Jun-fang

    2015-08-01

    The effects of substrate temperature on the plasma active species were investigated by plasma optical emission spectroscopy. With increasing substrate temperature, the characteristic spectroscopy intensity of the first positive series of N2* (B(3)Πg-->A(3)Σu(+)), the second positive N2* (C(3)Πu-->B(3)Πg), the first negative series N2(+)* (B(2)Σu(+)-->X(2)Σg(+)) and Zn* are increased. Due to the substrate temperature, each ion kinetic energy is increased and the collision ionization intensified in the chamber. That leading to plasma ion density increase. These phenomenons's show that the substrate temperature raises in a certain range was conducive to zinc nitride thin films growth. Zn3N2 thin films were prepared on Al films using ion sources-assisted magnetron sputtering deposition method. The degree of crystalline of the films was examined with X-ray diffraction (XRD). The results show that has a dominant peak located at 34.359° in room temperature, which was corresponding to the (321) plane of cubic anti-bixbyite zinc nitride structure (JCPDS Card No35-0762). When the substrate temperature was 100 °C, in addition to the (321) reflection, more diffraction peaks appeared corresponding to the (222), (400) and (600) planes, which were located at 31.756°, 36.620° and 56.612° respectively. When the substrate temperature was 200 °C, in addition to the (321), (222), (400) and (600) reflection, more new diffraction peaks also appeared corresponding to the (411), (332), (431) and (622) planes, which were located at 39.070, 43.179°, 47.004° and 62.561° respectively. These results show the film crystalline increased gradually with raise the substrate temperature. XP-1 profilometer were used to analyze the thickness of the Zn3N2 films. The Zn3N2 films deposited on Al films in mixture gas plasma had a deposition rate of 2.0, 2.2, and 2.7 nm · min(-1). These results indicate that the deposition rate was gradually enhanced as substrate temperature increased

  17. Influence of working gas pressure on structure and properties of WO3 films reactively deposited by rf magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Tanabe, J.; Yamada, N.; Nakabayashi, H.

    2003-07-01

    Tungsten trioxide (WO3) films with thickness of 0.9-6.7 μm have been deposited on glass-slide substrates, using rf magnetron sputtering in an atmosphere of mixture 80% Ar and 20% O2. The as-deposited films had a dark metallic color, like the W target, at a working gas pressure PW of 1 mTorr. Yellow films resulted at a PW of 3 mTorr. With a further increase of PW, the film color changed to pale yellow. From the x-ray diffraction patterns, the as-deposited films were polycrystalline crystallizing in the monoclinic crystal structure with high c-axis orientation perpendicular to the film plane. The optical transmittance of the films deposited at a PW of 1 mTorr is nearly zero. However, the transmittance of the films deposited at other PW are larger than 70% in the wavelength, λ, ranging from 500 to 900 nm. With decreasing λ to 400 nm, the transmittance decreases steeply to zero. The λ at this absorption edge is longer than that in TiO2 and comes in the visible region. The surface morphology of the films depends on PW. This different morphology may be attributed to the effect of the substrate heating by plasma emission because of the high plasma density at higher PW. The morphology of the films may also depend on the crystallinity of the WO3 films. As PW increased, the surfaces of the films became rougher but the grain sizes of the films did not always become larger. The WO3 films deposited in this study may be used for the underlayer of TiO2 photocatalyst.

  18. Indium doped ZnO films prepared by RF magnetron sputtering: effect of substrate temperature on the strain-induced band gap.

    PubMed

    Daniel, Georgi P; Kumar, David Devraj; Justinvictor, V B; Nair, Prabitha B; Joy, K; Koshy, Peter; Thomas, P V

    2012-03-01

    Indium doped zinc oxide (InZnO) thin films were deposited onto corning glass substrates by RF magnetron sputtering. The dependence of crystal structure, surface morphology, optical properties and electrical conductivity on substrate temperature was investigated using XRD, AFM, UV-vis Spectrophotometer, Fluorescence Spectrophotometer and four-point probe. The films were prepared at different substrate temperatures viz, room temperature (RT), 473 K and 673 K at RF power 200 W. All the films showed preferred orientation along (002) direction. Crystallite size increased from 14 to 19 nm as the substrate temperature was increased to 473 K. With increase in substrate temperature the crystallites did not show any further growth. AFM analysis showed that the rms roughness value decreased from 60 nm to 23 nm when the substrate temperature was increased to 673 K. Optical measurements revealed maximum band gap and minimum refractive index for the film prepared at 473 K. A strong correlation between the band gap variation and the strain developed at different substrate temperatures is established. PMID:22755081

  19. Multi-functional reactively-sputtered copper oxide electrodes for supercapacitor and electro-catalyst in direct methanol fuel cell applications

    PubMed Central

    Pawar, Sambhaji M.; Kim, Jongmin; Inamdar, Akbar I.; Woo, Hyeonseok; Jo, Yongcheol; Pawar, Bharati S.; Cho, Sangeun; Kim, Hyungsang; Im, Hyunsik

    2016-01-01

    This work reports on the concurrent electrochemical energy storage and conversion characteristics of granular copper oxide electrode films prepared using reactive radio-frequency magnetron sputtering at room temperature under different oxygen environments. The obtained films are characterized in terms of their structural, morphological, and compositional properties. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscope studies reveal that granular, single-phase Cu2O and CuO can be obtained by controlling the oxygen flow rate. The electrochemical energy storage properties of the films are investigated by carrying out cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. The electrochemical analysis reveals that the Cu2O and CuO electrodes have high specific capacitances of 215 and 272 F/g in 6 M KOH solution with a capacity retention of about 80% and 85% after 3000 cycles, respectively. Cyclic voltammetry and chronoamperometry are used to study the electrochemical energy conversion properties of the films via methanol electro-oxidation. The results show that the Cu2O and CuO electrodes are electro-catalytically active and highly stable. PMID:26888077

  20. Surface fluorination of rutile-TiO2 thin films deposited by reactive sputtering for accelerating response of optically driven capillary effect

    NASA Astrophysics Data System (ADS)

    Kobayashi, Taizo; Maeda, Hironobu; Konishi, Satoshi

    2016-06-01

    We report the acceleration of photoresponsive wettability switching by applying surface fluorination to rutile-TiO2 thin films deposited by reactive sputtering. Photoresponsive wettability switchable surfaces can be applied to optically driven liquid manipulation to enable the elimination of the electrical wiring and pneumatic tubing from fluidic systems. In this work, surface fluorination using CF4 plasma treatment is applied to rutile-TiO2 thin films, which exhibit a wider switching range of wettability than that of anatase-TiO2 thin films. Fluorine termination of TiO2 thin films increases the surface acidity and enhances its photocatalytic performance. TiO2 thin films with and without surface fluorination respectively exhibited the transition of contact angles ranging from 73.7 to 12.3°, and from 70.2 to 32° under UV irradiation for 15 min. Liquid introduction into a microchannel is also demonstrated, utilizing the developed TiO2 surface, which can generate a negative capillary pressure difference under ultraviolet light irradiation.

  1. Transmission photocathodes based on stainless steel mesh and quartz glass coated with N-doped DLC thin films prepared by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Arbet, J.

    2016-03-01

    The influence was investigated of N-doped diamond-like carbon (DLC) films properties on the quantum efficiency of a prepared transmission photocathode. N-doped DLC thin films were deposited on a silicon substrate, a stainless steel mesh and quartz glass (coated with 5 nm thick Cr adhesion film) by reactive magnetron sputtering using a carbon target and gas mixture Ar, 90%N2+10%H2. The elements' concentration in the films was determined by RBS and ERD. The quantum efficiency was calculated from the measured laser energy and the measured cathode charge. For the study of the vectorial photoelectric effect, the quartz type photocathode was irradiated by intensive laser pulses to form pin-holes in the DLC film. The quantum efficiency (QE), calculated at a laser energy of 0.4 mJ, rose as the nitrogen concentration in the DLC films was increased and rose dramatically after the micron-size perforation in the quartz type photocathodes.

  2. Effect of Aluminum concentration on structural and optical properties of DC reactive magnetron sputtered Zinc Aluminum Oxide thin films for transparent electrode applications

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Subba Rao, T.

    2012-11-01

    Zinc Aluminum Oxide(ZAO) thin films were deposited on glass substrates by DC reactive magnetron sputtering in an Ar+O2 gas mixture using commercial available Zn metal (99.99% purity) and Al (99.99% purity) targets of 2 inch diameter and 4 mm thickness. The films were characterized and the effect of aluminum (Al) concentration (2 at %-6 at %) on the structural and optical properties was studied. The average crystallite size obtained from Scherer formula is in the range of 32-44nm. Microstructural analysis using Scanning Electron Microscope (SEM) supplemented with EDS is carried out to find the grain size as well as to find the composition elemental data of prepared thin films. Optical study is performed to calculate the extinction coefficient (k), absorption coefficient (a), optical band gap (Eg) using transmission spectra obtained using UV-VIS-NIR spectrophotometer. There was widening of optical band gap with increasing aluminum concentration. ZAO film with low resistivity 3.2 × 10-4 cm and high transmittance of 80% is obtained for 3at% doped Al which is crucial for optoelectronic applications.

  3. Surface morphology and electrical properties of BiSrCaCuO thin films deposited by reactive sputtering from multiple targets

    NASA Astrophysics Data System (ADS)

    Rubin, L. M.; Orlando, T. P.; Vander Sande, J. B.

    1994-02-01

    Smooth, superconducting films of Bi 2Sr 2CaCu 2O 8+° have been prepared by reactive sputtering from elemental targets in the presence of ozone. The influence of substrate temperature, deposition rate, and ozone pressure on the resulting films are discussed. Films deposited on SrTiO 3 substrates are c-axis oriented and featureless for substrate temperatures below 710°C. Above this temperature, small inclusions of CuO appear. Films on MgO exhibit mixed a-axis and c-axis orientation below about 710°C, and inclusions of CuO above this temperature. The temperature at which this transition occurs increases with increasing deposition rate. Tc increases and then decreases sharply with decreasing oxygen content. The oxygen partial pressure corresponding to the maximum Tc of 77 K is well above the thermodynamic stability limit for Bi 2Sr 2CaCu 2O 8+°, suggesting that an optimum carrier concentration has been achieved for these films.

  4. Preparation of diamond-like carbon films using reactive Ar/CH4 high power impulse magnetron sputtering system with negative pulse voltage source for substrate

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Kamata, Hikaru

    2016-04-01

    Diamond-like carbon films were prepared using a reactive Ar/CH4 high-power impulse magnetron sputtering system with a negative pulse voltage source for the substrate, changing the CH4 fraction up to 15% in the total pressure range from 0.3 to 2 Pa. The magnitude of the negative pulse voltage for the substrate was also varied up to about 500 V. The hardness of films monotonically increased with increasing magnitude of the negative pulse voltage. The films with hardnesses between 16.5 and 23 GPa were prepared at total pressures less than 0.5 Pa and CH4 fractions less than 10% by applying an appropriate negative pulse voltage of 300-400 V. In X-ray photoelectron spectroscopy, the area ratio C-C sp3/(C-C sp2 + C-C sp3) in the C 1s core level was higher than 30% at pressures less than 0.5 Pa and CH4 fractions less than 15%. On the other hand, the films with hardnesses between 5 and 10 GPa were prepared with a relatively high growth rate at the partial pressures of CH4 higher than 0.1 Pa. However, the observation of the photoluminescence background in Raman spectroscopy indicated a relatively high hydrogen content.

  5. Structure Evolution and Electric Properties of TaN Films Deposited on Al2O3-BASED Ceramic and Glass Substrates by Magnetron Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Zhou, Yan Ming; Ma, Yang Zhao; Xie, Zhong; He, Ming Zhi

    2014-03-01

    Structure evolution and electric properties of tantalum nitride (TaN) films deposited on Al2O3-based ceramic and glass substrates by magnetron reactive sputtering were carried out as a function of the N2-to-Ar flow ratio. The TaN thin films on Al2O3-based ceramic substrates grow with micronclusters composed of numerous nanocrystallites, contains from single-phase of Ta2N grains to TaN, and exhibits high defect density, sheet resistance and negative TCR as the N2-to-Ar flow ratio continuously increases. However, the films on the glass substrates grow in the way of sandwich close-stack, contains from single-phase of Ta2N grains to TaN and Ta3N5 phases with the increase of N2-to-Ar flow ratio. These results indicate that the N2-to-Ar flow ratio and surface characteristic difference of substrates play a dominant effect on the structure and composition of the TaN films, resulting in different electrical properties for the films on Al2O3-based ceramic and the samples on glass substrates.

  6. Optimizing TaO{sub x} memristor performance and consistency within the reactive sputtering “forbidden region”

    SciTech Connect

    Lohn, Andrew J.; Stevens, James E.; Mickel, Patrick R.; Marinella, Matthew J.

    2013-08-05

    Standard deposition processes for depositing ReRAM oxides utilize mass flow of reactive gas to control stoichiometry and have difficulty depositing a precisely defined sub-stoichiometry within a “forbidden region” where film properties are discontinuous with mass flow. We show that by maintaining partial pressure within this discontinuous “forbidden region,” instead of by maintaining mass flow, we can optimize tantalum oxide device properties and reduce or eliminate the electroforming step. We also show that defining the partial pressure set point as a fraction of the “forbidden region” instead of as an absolute value can be used to improve wafer-to-wafer consistency with minimal recalibration efforts.

  7. CMOS Alcohol Sensor Employing ZnO Nanowire Sensing Films

    NASA Astrophysics Data System (ADS)

    Santra, S.; Ali, S. Z.; Guha, P. K.; Hiralal, P.; Unalan, H. E.; Dalal, S. H.; Covington, J. A.; Milne, W. I.; Gardner, J. W.; Udrea, F.

    2009-05-01

    This paper reports on the utilization of zinc oxide nanowires (ZnO NWs) on a silicon on insulator (SOI) CMOS micro-hotplate for use as an alcohol sensor. The device was designed in Cadence and fabricated in a 1.0 μm SOI CMOS process at XFAB (Germany). The basic resistive gas sensor comprises of a metal micro-heater (made of aluminum) embedded in an ultra-thin membrane. Gold plated aluminum electrodes, formed of the top metal, are used for contacting with the sensing material. This design allows high operating temperatures with low power consumption. The membrane was formed by using deep reactive ion etching. ZnO NWs were grown on SOI CMOS substrates by a simple and low-cost hydrothermal method. A few nanometer of ZnO seed layer was first sputtered on the chips, using a metal mask, and then the chips were dipped in a zinc nitrate hexahydrate and hexamethylenetramine solution at 90° C to grow ZnO NWs. The chemical sensitivity of the on-chip NWs were studied in the presence of ethanol (C2H5OH) vapour (with 10% relative humidity) at two different temperatures: 200 and 250° C (the corresponding power consumptions are only 18 and 22 mW). The concentrations of ethanol vapour were varied from 175-1484 ppm (pers per million) and the maximum response was observed 40% (change in resistance in %) at 786 ppm at 250° C. These preliminary measurements showed that the on-chip deposited ZnO NWs could be a promising material for a CMOS based ethanol sensor.

  8. Thin film growth of boron nitride on {alpha}-Al{sub 2}O{sub 3} (0 0 1) substrates by reactive sputtering

    SciTech Connect

    Anzai, Atsushi; Nishiyama, Fumitaka; Yamanaka, Shoji; Inumaru, Kei

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer A BN film grown on {alpha}-Al{sub 2}O{sub 3} (0 0 1) had a structure in which h-BN sheet stacking continued through almost the whole film thickness. Black-Right-Pointing-Pointer The structure was characterized by X-ray diffraction, ATR-IR, and XPS. Black-Right-Pointing-Pointer Tauc plots suggested the film had direct band gap and the optical band gap was close to that of bulk h-BN. -- Abstract: Boron nitride thin films were grown on {alpha}-Al{sub 2}O{sub 3} (0 0 1) substrates by reactive magnetron sputtering. Infrared attenuated total reflection (ATR) spectra of the films gave an intense signal associated with in-plane B-N stretching TO mode of short range ordered structure of BN hexagonal sheets. X-ray diffraction for the film prepared at a low working pressure (ca. 1 Multiplication-Sign 10{sup -3} Torr) gave a diffraction peak at slightly lower angle than that corresponding to crystal plane h-BN (0 0 2). It is notable that crystal thickness calculated from X-ray peak linewidth (45 nm) was close to film thickness (53 nm), revealing well developed sheet stacking along the direction perpendicular to the substrate surface. When the substrates of MgO (0 0 1) and Si (0 0 1) were used, the short-range ordered structure of h-BN sheet was formed but the films gave no X-ray diffraction. The film showed optical band gap of 5.9 eV, being close to that for bulk crystalline h-BN.

  9. CdTeOx to CdTeO3 structural phase transition in as-grown polycrystalline films by reactive sputtering

    NASA Astrophysics Data System (ADS)

    Carmona-Rodríguez, J.; Lozada-Morales, R.; Jiménez-Sandoval, O.; Rodríguez-Melgarejo, F.; Meléndez-Lira, M.; Jiménez-Sandoval, S. J.

    2008-06-01

    Polycrystalline thin films of CdTeOx (x <3) and CdTeO3 were grown at 400 °C by rf-reactive sputtering. The CdTe oxide films were elaborated in an Ar-O2 atmosphere using different oxygen flow rates in the 5-11 SCCM (SCCM denotes cubic centimeter per minute at STP) range. The structural properties of the samples were studied by x-ray diffraction and micro-Raman spectroscopy. The diffraction patterns show that the films grown with oxygen flows between 5 and 10.5 SCCM present a crystalline structure similar to that of pure CdTe films, that is, a mixture of cubic zinc-blende-type and hexagonal wurtzite-type structures. However, the diffraction patterns of samples grown under an oxygen flow rate of 11 SCCM are strikingly different and in agreement with that of cubic CdTeO3, indicating that a structural phase transition was achieved. These results are in accordance with those obtained by micro-Raman spectroscopy, where the spectra of the CdTeOx samples grown with oxygen flows below 11 SCCM show an intense LO CdTe-like peak at 166 cm-1, which is no longer observable for the CdTeO3 sample. Instead, the Raman spectrum in this case is dominated by two broad bands in the 550-800 cm-1 range, which have been ascribed to the vibrational modes of TeO3 structural subunits. The optical properties, as determined by optical absorption and photoreflectance spectroscopies, are in correspondence with the structural and chemical changes induced by the incorporation of oxygen. The band gap varied between 1.55 and 3.3 eV, the last value corresponding to CdTeO3 films.

  10. Microstructural evolution and Poisson ratio of epitaxial ScN grown on TiN(001)/MgO(001) by ultrahigh vacuum reactive magnetron sputter deposition

    SciTech Connect

    Gall, D.; Petrov, I.; Desjardins, P.; Greene, J.E.

    1999-11-01

    ScN layers, 60{endash}80 nm thick, were grown at 800&hthinsp;{degree}C on 220-nm-thick epitaxial TiN(001) buffer layers on MgO(001) by ultrahigh vacuum reactive magnetron sputter deposition in pure N{sub 2} discharges. The films are stoichiometric with N/Sc ratios, determined by Rutherford backscattering spectroscopy and x-ray photoelectron spectroscopy, of 1.00{plus_minus}0.02. Plan-view and cross-sectional transmission electron microscopy analyses showed that the films are single crystals which appear defect free up to a critical thickness of {approx_equal}15 nm, above which an array of nanopipes form with their tubular axis along the film growth direction and extending to the free surface. The nanopipes are rectangular in cross section with areas of {approx_equal}1.5{times}5&hthinsp;nm{sup 2} and are self-organized along {l_angle}100{r_angle}, directions with an average separation of {approx_equal}40 nm. Their formation is the result of periodic kinetic surface roughening which leads to atomic self-shadowing and, under limited adatom mobility conditions, to deep cusps which are the origin of the nanopipes. The ScN layers are nearly relaxed, as determined from x-ray diffraction {theta}-2{theta} scans in both reflection and transmission, with only a small residual compressive strain due to differential thermal contraction. The Poisson ratio of ScN was found to be 0.20{plus_minus}0.04, in good agreement with {ital ab initio} calculations. {copyright} {ital 1999 American Institute of Physics.}

  11. The effect of increasing V content on the structure, mechanical properties and oxidation resistance of Ti-Si-V-N films deposited by DC reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Fernandes, F.; Loureiro, A.; Polcar, T.; Cavaleiro, A.

    2014-01-01

    In the last years, vanadium rich films have been introduced as possible candidates for self-lubrication at high temperatures, based on the formation of V2O5 oxide. The aim of this investigation was to study the effect of V additions on the structure, mechanical properties and oxidation resistance of Ti-Si-V-N coatings deposited by DC reactive magnetron sputtering. The results achieved for TiSiVN films were compared and discussed in relation to TiN and TiSiN films prepared as reference. All coatings presented a fcc NaCl-type structure. A shift of the diffraction peaks to higher angles with increasing Si and V contents suggested the formation of a substitutional solid solution in TiN phase. Hardness and Young's modulus of the coatings were similar regardless on V content. The onset of oxidation of the films decreased significantly to 500 °C when V was added into the films; this behaviour was independent of the Si and V contents. The thermogravimetric isothermal curves of TiSiVN coatings oxidized at temperatures below the melting point of α-V2O5 (∼685 °C) showed two stages: at an early stage, the weight increase over time is linear, whilst, in the second stage, a parabolic evolution can be fitted to the experimental data. At higher temperatures only a parabolic evolution was fitted. α-V2O5 was the main phase detected at the oxidized surface of the coatings. Reduction of α-V2O5 to β-V2O5 phase occurred for temperatures above its melting point.

  12. Mechanical, tribological, and electrochemical behavior of Cr 1- xAl xN coatings deposited by r.f. reactive magnetron co-sputtering method

    NASA Astrophysics Data System (ADS)

    Sanchéz, J. E.; Sanchéz, O. M.; Ipaz, L.; Aperador, W.; Caicedo, J. C.; Amaya, C.; Landaverde, M. A. Hernández; Beltran, F. Espinoza; Muñoz-Saldaña, J.; Zambrano, G.

    2010-02-01

    Chromium aluminum nitride (Cr 1- xAl xN) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N 2) gas mixture from chromium and aluminum targets. Properties of deposited Cr 1- xAl xN coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr 1- xAl xN coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr 1- xAl xN cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr 1- xAl xN varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr 1- xAl xN coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere.

  13. Large modification in insulator-metal transition of VO2 films grown on Al2O3 (001) by high energy ion irradiation in biased reactive sputtering

    NASA Astrophysics Data System (ADS)

    Azhan, Nurul Hanis; Okimura, Kunio; Ohtsubo, Yoshiyuki; Kimura, Shin-ichi; Zaghrioui, Mustapha; Sakai, Joe

    2016-02-01

    High energy ion irradiation in biased reactive sputtering enabled significant modification of insulator-metal transition (IMT) properties of VO2 films grown on Al2O3 (001). Even at a high biasing voltage with mean ion energy of around 325 eV induced by the rf substrate biasing power of 40 W, VO2 film revealed low IMT temperature (TIMT) at 309 K (36 °C) together with nearly two orders magnitude of resistance change. Raman measurements from -193 °C evidenced that the monoclinic VO2 lattice begins to transform to rutile-tetragonal lattice near room temperature. Raman spectra showed the in-plane compressive stress in biased VO2 films, which results in shortening of V-V distance along a-axis of monoclinic structure, aM-axis (cR-axis) and thus lowering the TIMT. In respect to that matter, significant effects in shortening the in-plane axis were observed through transmission electron microscopy observations. V2p3/2 spectra from XPS measurements suggested that high energy ion irradiation also induced oxygen vacancies and resulted for an early transition onset and rather broader transition properties. Earlier band gap closing against the temperature in VO2 film with higher biasing power was also probed by ultraviolet photoelectron spectroscopy. Present results with significant modification of IMT behavior of films deposited at high-energy ion irradiation with TIMT near the room temperature could be a newly and effective approach to both exploring mechanisms of IMT and further applications of this material, due to the fixed deposition conditions and rather thicker VO2 films.

  14. A comparative study of the electrical properties of TiO2 films grown by high-pressure reactive sputtering and atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Dueñas, S.; Castán, H.; García, H.; San Andrés, E.; Toledano-Luque, M.; Mártil, I.; González-Díaz, G.; Kukli, K.; Uustare, T.; Aarik, J.

    2005-10-01

    Oxide-semiconductor interface quality of high-pressure reactive sputtered (HPRS) TiO2 films annealed in O2 at temperatures ranging from 600 to 900 °C, and atomic layer deposited (ALD) TiO2 films grown at 225 or 275 °C from TiCl4 or Ti(OC2H5)4, and annealed at 750 °C in O2, has been studied on silicon substrates. Our attention has been focused on the interfacial state and disordered-induced gap state densities. From our results, HPRS films annealed at 900 °C in oxygen atmosphere exhibit the best characteristics, with Dit density being the lowest value measured in this work (5-6 × 1011 cm-2 eV-1), and undetectable conductance transients within our experimental limits. This result can be due to two contributions: the increase of the SiO2 film thickness and the crystallinity, since in the films annealed at 900 °C rutile is the dominant crystalline phase, as revealed by transmission electron microscopy and infrared spectroscopy. In the case of annealing in the range of 600-800 °C, anatase and rutile phases coexist. Disorder-induced gap state (DIGS) density is greater for 700 °C annealed HPRS films than for 750 °C annealed ALD TiO2 films, whereas 800 °C annealing offers DIGS density values similar to ALD cases. For ALD films, the studies clearly reveal the dependence of trap densities on the chemical route used.

  15. Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques

    NASA Astrophysics Data System (ADS)

    Adachi, N.; Denysenkov, V. P.; Khartsev, S. I.; Grishin, A. M.; Okuda, T.

    2000-09-01

    We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd3(ScGa)5O12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ion beam sputtering (RIBS) techniques. A very high deposition rate of about 0.8 μm/h has been achieved in the PLD process. Comprehensive x-ray diffraction analyses reveal epitaxial quality both of the films: they are single phase, exclusively (001) oriented, the full width at half maximum of the rocking curve of (004) Bragg reflection is 0.06 deg for PLD and 0.05 deg for RIBS film, strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. Saturation magnetization 4πMs and Faraday rotation at 635 nm were found to be 1400 Gs and -7.8 deg/μm in PLD-BIG, and 1200 Gs and -6.9 deg/μm in RIBS-BIG. Ferromagnetic resonance (FMR) measurements performed at 9.25 GHz yielded the gyromagnetic ratio γ=1.797×107l/s Oe, 1.826×107 l/s Oe; the constants of uniaxial magnetic anisotropy were Ku*=-8.66×104erg/cm3, -8.60×104 erg/cm3; the cubic magnetic anisotropy K1=-2.7×103 erg/cm3,-3.8×103 erg/cm3; and the FMR linewidth ΔH=25 and 34 Oe for PLD and RIBS films correspondingly. High Faraday rotation, low microwave loss, and low coercive field ⩽40 Oe of BIG/GSGG(001) films promise their use in integrated magneto-optic applications.

  16. Homoepitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C-H; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; McCarty, P.; George, M. A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    ZnO films have high potential for many applications, such as surface acoustic wave filters, UV detectors, and light emitting devices due to its structural, electrical, and optical properties. High quality epitaxial films are required for these applications. The Al2O3 substrate is commonly used for ZnO heteroepitaxial growth. Recently, high quality ZnO single crystals are available for grow homoepitaxial films. Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films were also deposited on (0001) Al2O3 substrates. It was found that the two polar ZnO surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which strongly influence the epitaxial film growth. The morphology and structure of homoepitaxial films grown on the ZnO substrates were different from heteroepitaxial films grown on the Al2O3. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

  17. Sputter target

    DOEpatents

    Gates, Willard G.; Hale, Gerald J.

    1980-01-01

    The disclosure relates to an improved sputter target for use in the deposition of hard coatings. An exemplary target is given wherein titanium diboride is brazed to a tantalum backing plate using a gold-palladium-nickel braze alloy.

  18. Fabrication of ZnO photonic crystals by nanosphere lithography using inductively coupled-plasma reactive ion etching with CH{sub 4}/H{sub 2}/Ar plasma on the ZnO/GaN heterojunction light emitting diodes

    SciTech Connect

    Chen, Shr-Jia; Chang, Chun-Ming; Kao, Jiann-Shiun; Chen, Fu-Rong; Tsai, Chuen-Horng

    2010-07-15

    This article reports fabrication of n-ZnO photonic crystal/p-GaN light emitting diode (LED) by nanosphere lithography to further booster the light efficiency. In this article, the fabrication of ZnO photonic crystals is carried out by nanosphere lithography using inductively coupled plasma reactive ion etching with CH{sub 4}/H{sub 2}/Ar plasma on the n-ZnO/p-GaN heterojunction LEDs. The CH{sub 4}/H{sub 2}/Ar mixed gas gives high etching rate of n-ZnO film, which yields a better surface morphology and results less plasma-induced damages of the n-ZnO film. Optimal ZnO lattice parameters of 200 nm and air fill factor from 0.35 to 0.65 were obtained from fitting the spectrum of n-ZnO/p-GaN LED using a MATLAB code. In this article, we will show our recent result that a ZnO photonic crystal cylinder has been fabricated using polystyrene nanosphere mask with lattice parameter of 200 nm and radius of hole around 70 nm. Surface morphology of ZnO photonic crystal was examined by scanning electron microscope.

  19. Evaluation of transverse piezoelectric coefficient of ZnO thin films deposited on different flexible substrates: a comparative study on the vibration sensing performance.

    PubMed

    Joshi, Sudeep; Nayak, Manjunatha M; Rajanna, K

    2014-05-28

    We report on the systematic comparative study of highly c-axis oriented and crystalline piezoelectric ZnO thin films deposited on four different flexible substrates for vibration sensing application. The flexible substrates employed for present experimental study were namely a metal alloy (Phynox), metal (aluminum), polyimide (Kapton), and polyester (Mylar). ZnO thin films were deposited by an RF reactive magnetron sputtering technique. ZnO thin films of similar thicknesses of 700 ± 30 nm were deposited on four different flexible substrates to have proper comparative studies. The crystallinity, surface morphology, chemical composition, and roughness of ZnO thin films were evaluated by respective material characterization techniques. The transverse piezoelectric coefficient (d31) value for assessing the piezoelectric property of ZnO thin films on different flexible substrates was measured by a four-point bending method. ZnO thin films deposited on Phynox alloy substrate showed relatively better material characterization results and a higher piezoelectric d31 coefficient value as compared to ZnO films on metal and polymer substrates. In order to experimentally verify the above observations, vibration sensing studies were performed. As expected, the ZnO thin film deposited on Phynox alloy substrate showed better vibration sensing performance. It has generated the highest peak to peak output voltage amplitude of 256 mV as compared to that of aluminum (224 mV), Kapton (144 mV), and Mylar (46 mV). Therefore, metal alloy flexible substrate proves to be a more suitable, advantageous, and versatile choice for integrating ZnO thin films as compared to metal and polymer flexible substrates for vibration sensing applications. The present experimental study is extremely important and helpful for the selection of a suitable flexible substrate for various applications in the field of sensor and actuator technology.

  20. Impact of solar UV radiation on toxicity of ZnO nanoparticles through photocatalytic reactive oxygen species (ROS) generation and photo-induced dissolution

    EPA Science Inventory

    The present study investigated the impact of solar UV radiation on ZnO nanoparticle toxicity through photocatalytic ROS generation and photo-induced dissolution. Toxicity of ZnO nanoparticles to Daphnia magna was examined under laboratory light versus simulated solar UV radiatio...

  1. A reactive magnetron sputtering route for attaining a controlled core-rim phase partitioning in Cu2O/CuO thin films with resistive switching potential

    NASA Astrophysics Data System (ADS)

    Ogwu, A. A.; Darma, T. H.

    2013-05-01

    The achievement of a reproducible and controlled deposition of partitioned Cu2O/CuO thin films by techniques compatible with ULSI processing like reactive magnetron sputtering has been reported as an outstanding challenge in the literature. This phase partitioning underlies their performance as reversible resistive memory switching devices in advanced microelectronic applications of the future. They are currently fabricated by thermal oxidation and chemical methods. We have used a combination of an understanding from plasma chemistry, thermo-kinetics of ions, and rf power variation during deposition to successfully identify a processing window for preparing partitioned Cu2O/CuO films. The production of a core rich Cu2O and surface rich Cu2O/CuO mixture necessary for oxygen migration during resistive switching is confirmed by XRD peaks, Fourier transform infra red Cu (I)-O vibrational modes, XPS Cu 2P3/2 and O 1S peak fitting, and a comparison of satellite peak ratio's in Cu 2P3/2 fitted peaks. We are proposing based on the findings reported in this paper that an XPS satellite peak intensity(Is) to main peak intensity ratio (Im) ≤ 0.45 as an indicator of a core rich Cu2O and surface rich Cu2O/CuO formation in our prepared films. CuO is solely responsible for the satellite peaks. This is explained on the basis that plasma dissociation of oxygen will be limited to the predominant formation of Cu2O under certain plasma deposition conditions we have identified in this paper, which also results in a core-rim phase partitioning. The deposited films also followed a Volmer-Weber columnar growth mode, which could facilitate oxygen vacancy migration and conductive filaments at the columnar interfaces. This is further confirmed by optical transmittance and band-gap measurements using spectrophotometry. This development is expected to impact on the early adoption of copper oxide based resistive memory electronic switching devices in advanced electronic devices of the future

  2. Growth of fullerene-like carbon nitride thin solid films by reactive magnetron sputtering; role of low-energy ion irradiation in determining microstructure and mechanical properties

    NASA Astrophysics Data System (ADS)

    Neidhardt, J.; Czigány, Zs.; Brunell, I. F.; Hultman, L.

    2003-03-01

    Fullerene-like (FL) carbon nitride (CNx) films were deposited on Si (100) substrates by dc reactive, unbalanced, magnetron sputtering in a N2/Ar mixture from a high-purity pyrolythic graphite cathode in a dual-magnetron system with coupled magnetic fields. The N2 fraction in the discharge gas (0%-100%) and substrate bias (-25 V; -40 V) was varied, while the total pressure (0.4 Pa) and substrate temperature (450 °C) was kept constant. The coupled configuration of the magnetrons resulted in a reduced ion flux density, leading to a much lower average energy per incorporated particle, due to a less focused plasma as compared to a single magnetron. This enabled the evolution of a pronounced FL microstructure. The nitrogen concentration in the films saturated rapidly at 14-18 at. %, as determined by elastic recoil analysis, with a minor dependence on the discharge conditions. No correlations were detected between the photoelectron N1s core level spectra and the different microstructures, as observed by high-resolution electron microscopy. A variety of distinct FL structures were obtained, ranging from structures with elongated and aligned nitrogen-containing graphitic sheets to disordered structures, however, not exclusively linked to the total N concentration in the films. The microstructure evolution has rather to be seen as in equilibrium between the two competing processes of adsorption and desorption of nitrogen-containing species at the substrate. This balance is shifted by the energy and number of arriving species as well as by the substrate temperature. The most exceptional structure, for lower N2 fractions, consists of well-aligned, multi-layered circular features (nano-onions) with an inner diameter of approximately 0.7 nm and successive shells at a distance of ˜0.35 nm up to a diameter of 5 nm. It is shown that the intrinsic stress formation is closely linked with the evolution and accommodation of the heavily bent fullerene-like sheets. The FL CNx

  3. Influence of vanadium incorporation on the microstructure, mechanical and tribological properties of Nb–V–Si–N films deposited by reactive magnetron sputtering

    SciTech Connect

    Ju, Hongbo; Xu, Junhua

    2015-09-15

    Composite Nb–V–Si–N films with various V contents (3.7–13.2 at.%) were deposited by reactive magnetron sputtering and the effects of V content on the microstructure, mechanical and tribological properties of Nb–V–Si–N films were investigated. The results revealed that a three-phase structure, consisting of face-centered cubic (fcc) Nb–V–Si–N, hexagonal close-packed (hcp) Nb–V–Si–N and amorphous Si{sub 3}N{sub 4}, co-exists in the Nb–V–Si–N films and the cubic phase is dominant. The hardness and critical load (L{sub c}) of Nb–V–Si–N films initially increased gradually and reached a summit, then decreased with the increasing V content in the films and the maximum values were 35 GPa and 9.8 N, respectively, at 6.4 at.% V. The combination of V into Nb–Si–N film led to the fracture toughness linearly increasing from 1.11 MPa·m{sup 1/2} at 3.7 at.% V to 1.67 MPa·m{sup 1/2} at 13.2 at.% V. At room temperature (RT), the average friction coefficient decreased from 0.80 at 3.7 at.% V to 0.55 at 13.2 at.% V for the Nb–V–Si–N films. The wear rate of Nb–V–Si–N films initially decreased and then increased after reaching a minimum value of about 6.35 × 10{sup −} {sup 7} mm{sup 3}/N·mm at 6.4 at.% V. As the rise of testing temperature from 200 °C to 600 °C, the average friction coefficient of Nb–V–Si–N films decreased with the increase of the testing temperature regardless of V content. However, the wear rate gradually increased for all films. The average friction coefficient and wear rate at RT and elevated temperatures were mainly influenced by the vanadium oxides with weakly bonded lattice planes. - Highlight: • Fcc-Nb–V–Si–N, hcp-Nb–V–Si–N and amorphous Si{sub 3}N{sub 4} co-existed in the films. • The amount of Si{sub 3}N{sub 4} decreased with increasing V content in the films. • Hardness of Nb–V–Si–N film (6.4 at.%) reached a maximum value of 35 GPa. • Addition of V led to the

  4. Effect of SiN x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol-gel dip coating and reactive magnetron sputtering.

    PubMed

    Ghazzal, Mohamed Nawfal; Aubry, Eric; Chaoui, Nouari; Robert, Didier

    2015-01-01

    We investigate the effect of the thickness of the silicon nitride (SiN x ) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol-gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN x diffusion barrier. Increasing the thickness of the SiN x diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol-gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiN x barrier diffusion. The SiN x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed.

  5. Effect of SiNx diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol–gel dip coating and reactive magnetron sputtering

    PubMed Central

    Aubry, Eric; Chaoui, Nouari; Robert, Didier

    2015-01-01

    Summary We investigate the effect of the thickness of the silicon nitride (SiNx) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol–gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiNx diffusion barrier. Increasing the thickness of the SiNx diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol–gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiNx barrier diffusion. The SiNx barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed. PMID:26665074

  6. The influence of Atomic Oxygen on the Figure of Merit of Indium Tin Oxide thin Films grown by reactive Dual Ion Beam Sputtering

    NASA Astrophysics Data System (ADS)

    Geerts, Wilhelmus; Simpson, Nelson; Woodall, Allen; Compton, Maclyn

    2014-03-01

    Indium Tin Oxide (ITO) is a transparent conducting oxide that is used in flat panel displays and optoelectronics. Highly conductive and transparent ITO films are normally produced by heating the substrate to 300 Celsius during deposition excluding plastics to be used as a substrate material. We investigated whether high quality ITO films can be sputtered at room temperature using atomic instead of molecular oxygen. The films were deposited by dual ion beam sputtering (DIBS). During deposition the substrate was exposed to a molecular or an atomic oxygen flux. Microscope glass slides and silicon wafers were used as substrates. A 29 nm thick SIO2 buffer layer was used. Optical properties were measured with a M2000 Woollam variable angle spectroscopic ellipsometer. Electrical properties were measured by linear four point probe using a Jandel 4pp setup employing silicon carbide electrodes, high input resistance, and Keithley low bias current buffer amplifiers. The figure of merit (FOM), i.e. the ratio of the conductivity and the average optical absorption coefficient (400-800 nm), was calculated from the optical and electric properties and appeared to be 1.2 to 5 times higher for the samples sputtered with atomic oxygen. The largest value obtained for the FOM was 0.08 reciprocal Ohms. The authors would like to thank the Research Corporation for Financial Support.

  7. Inverse I-V Injection Characteristics of ZnO Nanoparticle-Based Diodes.

    PubMed

    Mundt, Paul; Vogel, Stefan; Bonrad, Klaus; von Seggern, Heinz

    2016-08-10

    Simple Al/ZnO(NP)/Au diodes produced by spin coating of ZnO nanoparticle dispersions (ZnO(NP)) on Al/Al2O3 and Au substrates and subsequent Au deposition have been investigated to understand electron injection properties of more complex devices, incorporating ZnO(NP) as injection layer. Inverse I-V characteristics have been observed compared to conventional Al/ZnO(SP)/Au diodes produced by reactive ion sputtering of ZnO. SEM micrographs reveal that the void-containing contact of ZnO(NP) with the bottom Al electrode and the rough morphology of the top Au electrode are likely to be responsible for the observed injection and ejection probabilities of electrons. A simple tunneling model, incorporating the voids, explains the strongly reduced injection currents from Al whereas the top electrode fabricated by vapor deposition of Au onto the nanoparticle topology adopts the inverse ZnO(NP) morphology leading to enlarged injection areas combined with Au-tip landscapes. These tips in contrast to the smooth sputtered ZnO(SP) lead to electric field enhancement and strongly increased injection of electrons in reverse direction. The injected charge piles up at the barrier generated by voids between ZnO(NP) and the bottom electrode forcing a change in the barrier shape and therefore allowing for higher ejection rates. Both effects in combination explain the inverse I-V characteristic of nanoparticle based diodes.

  8. A MEMS based acetone sensor incorporating ZnO nanowires synthesized by wet oxidation of Zn film

    NASA Astrophysics Data System (ADS)

    Behera, Bhagaban; Chandra, Sudhir

    2015-01-01

    In this work, we report a simple and efficient method for synthesis of ZnO nanowires by thermal oxidation of Zn film and their integration with MEMS technologies to fabricate a sensor for acetone vapour detection. ZnO nanowires were prepared by thermal oxidation of sputter deposited Zn film. The nanostructured ZnO was characterized by x-ray diffraction, a scanning electron microscope and room temperature photoluminescence measurements. The ZnO nanowires synthesis process was integrated with MEMS technologies to obtain a sensor for volatile organic compounds, incorporating an on-chip Ni microheater and an interdigited electrode structure. To reduce the heat loss from the on-chip microheater, the sensor was made on a thin silicon diaphragm obtained via a modified reactive ion etching process. This resulted in considerable power saving during sensor operation. For this, a three-mask process was used. The performance of the microheater was simulated on COMSOL and validated experimentally. The sensor has been tested for acetone vapour sensing and the operating parameters were optimized. The sensor has the ability to detect acetone vapour at 5 parts per million (ppm) concentrations when operated at 100 °C. The sensor consumed only 36 mW power and showed a high-sensitivity value of 26.3% for 100 ppm of acetone vapour.

  9. Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

    NASA Astrophysics Data System (ADS)

    Ceylan, Abdullah; Ozcan, Yusuf; Orujalipoor, Ilghar; Huang, Yen-Chih; Jeng, U.-Ser; Ide, Semra

    2016-06-01

    In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactive growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.

  10. Physical deoxygenation of graphene oxide paper surface and facile in situ synthesis of graphene based ZnO films

    SciTech Connect

    Ding, Jijun; Wang, Minqiang Zhang, Xiangyu; Ran, Chenxin; Shao, Jinyou; Ding, Yucheng

    2014-12-08

    In-situ sputtering ZnO films on graphene oxide (GO) paper are used to fabricate graphene based ZnO films. Crystal structure and surface chemical states are investigated. Results indicated that GO paper can be effectively deoxygenated by in-situ sputtering ZnO on them without adding any reducing agent. Based on the principle of radio frequency magnetron sputtering, we propose that during magnetron sputtering process, plasma streams contain large numbers of electrons. These electrons not only collide with argon atoms to produce secondary electrons but also they are accelerated to bombard the substrates (GO paper) resulting in effective deoxygenation of oxygen-containing functional groups. In-situ sputtering ZnO films on GO paper provide an approach to design graphene-semiconductor nanocomposites.

  11. Role of ZnO thin film in the vertically aligned growth of ZnO nanorods by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Son, Nguyen Thanh; Noh, Jin-Seo; Park, Sungho

    2016-08-01

    The effect of ZnO thin film on the growth of ZnO nanorods was investigated. ZnO thin films were sputter-deposited on Si substrate with varying the thickness. ZnO nanorods were grown on the thin film using a chemical bath deposition (CBD) method at 90 °C. The ZnO thin films showed granular structure and vertical roughness on the surface, which facilitated the vertical growth of ZnO nanorods. The average grain size and the surface roughness of ZnO film increased with an increase in film thickness, and this led to the increase in both the average diameter and the average length of vertically grown ZnO nanorods. In particular, it was found that the average diameter of ZnO nanorods was very close to the average grain size of ZnO thin film, confirming the role of ZnO film as a seed layer for the vertical growth of ZnO nanorods. The CBD growth on ZnO seed layers may provide a facile route to engineering vertically aligned ZnO nanorod arrays.

  12. Effect of buffer layer growth temperature on epitaxial GaN films deposited by magnetron sputtering

    SciTech Connect

    Mohanta, P.; Singh, D.; Kumar, R.; Ganguli, T.; Srinivasa, R. S.; Major, S. S.

    2012-06-05

    Epitaxial GaN films were deposited by reactive sputtering of a GaAs target in 100 % nitrogen at 700 deg. C on ZnO buffer layers grown at different substrate temperatures over sapphire substrates. High resolution X-ray diffraction measurements and the corresponding analysis show that the growth temperature of buffer layers significantly affects the micro-structural parameters of GaN epilayer, such as lateral coherence length, tilt and twist, while the vertical coherence length remains unaffected. The optimum substrate temperature for buffer layer growth has been found to be 300 deg. C. High epitaxial quality GaN film grown on such a buffer layer exhibited micro strain of 1.8x10{sup -4} along with screw and edge type dislocation densities of 7.87x10{sup 9} and 1.16x10{sup 11}, respectively.

  13. Structural, chemical and nanomechanical investigations of SiC/polymeric a-C:H films deposited by reactive RF unbalanced magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Tomastik, C.; Lackner, J. M.; Pauschitz, A.; Roy, M.

    2016-03-01

    Amorphous carbon (or diamond-like carbon, DLC) films have shown a number of important properties usable for a wide range of applications for very thin coatings with low friction and good wear resistance. DLC films alloyed with (semi-)metals show some improved properties and can be deposited by various methods. Among those, the widely used magnetron sputtering of carbon targets is known to increase the number of defects in the films. Therefore, in this paper an alternative approach of depositing silicon-carbide-containing polymeric hydrogenated DLC films using unbalanced magnetron sputtering was investigated. The influence of the C2H2 precursor concentration in the deposition chamber on the chemical and structural properties of the deposited films was investigated by Raman spectroscopy, X-ray photoelectron spectroscopy and elastic recoil detection analysis. Roughness, mechanical properties and scratch response of the films were evaluated with the help of atomic force microscopy and nanoindentation. The Raman spectra revealed a strong correlation of the film structure with the C2H2 concentration during deposition. A higher C2H2 flow rate results in an increase in SiC content and decrease in hydrogen content in the film. This in turn increases hardness and elastic modulus and decreases the ratio H/E and H3/E2. The highest scratch resistance is exhibited by the film with the highest hardness, and the film having the highest overall sp3 bond content shows the highest elastic recovery during scratching.

  14. Sputter process diagnostics by negative ions

    NASA Astrophysics Data System (ADS)

    Zeuner, Michael; Neumann, Horst; Zalman, Jan; Biederman, Hynek

    1998-05-01

    We measured the energy distributions of negative ions during reactive sputtering of silicon in oxygen. Various oxygen containing negative ions are formed in the cathode sheath or directly at the sputter target, respectively. These negative ions are accelerated away from the cathode by the electrical field, and can be detected using a mass spectrometer facing the sputter magnetron. The origin of each ion can be determined from peak structures in the energy distribution. Additionally the flux of different negative ions provides information on poisoning of the target by oxide films.

  15. Sputtering and ion plating

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The proceedings of a conference on sputtering and ion plating are presented. Subjects discussed are: (1) concepts and applications of ion plating, (2) sputtering for deposition of solid film lubricants, (3) commercial ion plating equipment, (4) industrial potential for ion plating and sputtering, and (5) fundamentals of RF and DC sputtering.

  16. Electrochromic properties and performance of NiOx films and their corresponding all-thin-film flexible devices preparedby reactive DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Dong, Dongmei; Wang, Wenwen; Dong, Guobo; Zhang, Fan; He, Yingchun; Yu, Hang; Liu, Famin; Wang, Mei; Diao, Xungang

    2016-10-01

    Nickel oxide (NiOx) thin films were deposited by direct current magnetron sputtering technique onto flexible substrates with various oxygen (O2) partial pressures. The influence of O2 contents during deposition process on film structure, morphology, composition, optical and electrochromic (EC) characteristics of the films were investigated. The EC response for nonstoichiometric NiOx films shows a strong dependence on grain size variations and surface morphology. Finally, the multiple-layer stacks ITO/NiOx/Ta2O5:H/WO3/ITO were sequentially vacuum deposited over flexible polyethylene terephthalate plates based on the optimization of NiOx single layers. A large optical contrast up to 60% and a good durability are obtained for full device. To perform preliminary research on the mechanical properties within flexible devices, we introduced nontrivial changes to the interfacial properties by replacing the glass with flexible polymers. The effects were studied through static bending and the nano-scratch test.

  17. Magnetron sputtering source

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.; Grabner, R.F.; Ramsey, P.B.

    1994-08-02

    A magnetron sputtering source for sputtering coating substrates includes a high thermal conductivity electrically insulating ceramic and magnetically attached sputter target which can eliminate vacuum sealing and direct fluid cooling of the cathode assembly. The magnetron sputtering source design results in greater compactness, improved operating characteristics, greater versatility, and low fabrication cost. The design easily retrofits most sputtering apparatuses and provides for safe, easy, and cost effective target replacement, installation, and removal. 12 figs.

  18. Magnetron sputtering source

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.; Grabner, R. Fred; Ramsey, Philip B.

    1994-01-01

    A magnetron sputtering source for sputtering coating substrates includes a high thermal conductivity electrically insulating ceramic and magnetically attached sputter target which can eliminate vacuum sealing and direct fluid cooling of the cathode assembly. The magnetron sputtering source design results in greater compactness, improved operating characteristics, greater versatility, and low fabrication cost. The design easily retrofits most sputtering apparatuses and provides for safe, easy, and cost effective target replacement, installation, and removal.

  19. Ambient-Temperature Sputtering Of Composite Oxide Films

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1992-01-01

    Technique for deposition of homogeneous films of multicomponent oxides on substrates at ambient temperature based on sequential sputter deposition of individual metal components, as alternating ultra-thin layers, from multiple targets. Substrates rotated over sputtering targets of lead, zirconium, and titanium. Dc-magnetron sputtering of constituent metals in reactive ambient of argon and oxygen leads to formation of the respective metal oxides intermixed on extremely fine scale in desired composition. Compatible with low-temperature microelectronic processing.

  20. Electrochromic behavior of W(x)Si(y)O(z) thin films prepared by reactive magnetron sputtering at normal and glancing angles.

    PubMed

    Gil-Rostra, Jorge; Cano, Manuel; Pedrosa, José M; Ferrer, Francisco Javier; García-García, Francisco; Yubero, Francisco; González-Elipe, Agustín R

    2012-02-01

    This work reports the synthesis at room temperature of transparent and colored W(x)Si(y)O(z) thin films by magnetron sputtering (MS) from a single cathode. The films were characterized by a large set of techniques including X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), Fourier transform infrared (FT-IR), and Raman spectroscopies. Their optical properties were determined by the analysis of the transmission and reflection spectra. It was found that both the relative amount of tungsten in the W-Si MS target and the ratio O(2)/Ar in the plasma gas were critical parameters to control the blue coloration of the films. The long-term stability of the color, attributed to the formation of a high concentration of W(5+) and W(4+) species, has been related with the formation of W-O-Si bond linkages in an amorphous network. At normal geometry (i.e., substrate surface parallel to the target) the films were rather compact, whereas they were very porous and had less tungsten content when deposited in a glancing angle configuration. In this case, they presented outstanding electrochromic properties characterized by a fast response, a high coloration, a complete reversibility after more than one thousand cycles and a relatively very low refractive index in the bleached state. PMID:22208156

  1. Surface treatment of diamond-like carbon films by reactive Ar/CF4 high-power pulsed magnetron sputtering plasmas

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Nishimura, Ryotaro; Azuma, Kingo; Nakao, Setsuo; Sonoda, Tsutomu; Kusumori, Takeshi; Ozaki, Kimihiro

    2015-12-01

    Surface modification of diamond-like carbon films deposited by a high-power pulsed magnetron sputtering (HPPMS) of Ar was carried out by a HPPMS of Ar/CF4 mixture, changing a CF4 fraction from 2.5% to 20%. The hardness of the modified films markedly decreased from about 13 to about 3.5 GPa with increasing CF4 fraction, whereas the water contact angle of the modified films increased from 68° to 109° owing to the increase in the CFx content on the film surface. C 1s spectra in X-ray photoelectron spectroscopy indicated that a graphitic structure of modified films was formed at CF4 fractions less than 5%, above which the modified films possessed a polymer-like structure. Influence of treatment time on the properties of the modified films was also investigated in the range of treatment time from 5 to 30 min. The properties of the modified films did not depend on the treatment time in the range of treatment time longer than 10 min, whereas the water contact angle was not sensitive to the treatment time at any treatment time.

  2. Effects of substrate bias and nitrogen flow ratio on the surface morphology and binding state of reactively sputtered ZrN x films before and after annealing

    NASA Astrophysics Data System (ADS)

    Jeng, J. S.; Chen, J. S.

    2009-07-01

    ZrN x films were sputtered in an Ar + N 2 atmosphere, with different substrate biases (0 to -200 V) at various nitrogen flow ratios (%N 2 = 0.5-24%). The surface morphology, resistivity, crystllinity, and bonding configuration of ZrN x films, before and after vacuum annealing, were investigated. As compared with ZrN x films grown without substrate bias, before and after annealing, the resistivity of 1% and 2% N 2 films decreases with increasing substrate biases. Simultaneously, if the applied bias is too high, the crystallinity of ZrN x film will decrease. The surfaces of 1% and 2% N 2 flow films deposited without bias have small nodules, whereas the surface morphology of films deposited at -100 V of substrate bias exhibits large nodules and rugged surface. Once a -200 V of substrate bias is applied to the substrate, the surface morphology of ZrN x films, grown at 1% and 2% nitrogen flow ratios, is smooth. Furthermore, there are two deconvoluted peaks in XPS spectra (i.e., Zr-O and Zr-N) of ZrN x films deposited at -200 V of substrate bias before and after annealing. On the other hand, the surface morphology changes dramatically from rugged surfaces for film deposited at lower nitrogen flow ratio (%N 2 < 1%) to smoother and denser surfaces for film grown at higher nitrogen flow ratio (%N 2 ≥ 1%). The Zr-N bonding in 2% N 2 films still exist after annealing at 700 °C, while the Zr-N bonding in 0.5% and 16% N 2 flow film vanish at the same temperature. The connection between the resistivity, crystallinity, surface morphology, and bonding configuration of ZrN x films and how they are influenced by the substrate bias and nitrogen flow ratio are discussed in this paper.

  3. Development of Anti-Reflection Coating Layer for Efficiency Enhancement of ZnO Dye-Sensitized Solar Cells.

    PubMed

    Chanta, E; Bhoomanee, C; Gardchareon, A; Wongratanaphisan, D; Phadungdhitidhada, S; Choopun, S

    2015-09-01

    In this research, we investigated the effects of ZnO anti-reflection coating layers on power conversion efficiency enhancement of ZnO dye-sensitized solar cells. ZnO thin films were prepared by rf-magnetron sputtering by varying sputtering time of 10, 30, 60, 80, 100 min. Surface morphology, thickness and optical reflective index were investigated by field emission scanning electron microscopy and ellipsometry. Then, transmittance and reflectance were investigated by UV-vis spectroscopy. Furthermore, we found that ZnO anti-reflection coating layers with sputtering time of 30 and 60 min showed lower reflection and higher transmission than that of reference film. In addition, ZnO anti-reflection coating layers have rough surface with sputtering rate has 2.14 nm/min. Thus, the ZnO anti-reflection coating layers with sputtering time in the range of 10-60 min have a potential as anti-reflection coating applications. The ZnO anti-reflection coating layers were used in ZnO dye-sensitized solar cells and exhibited a short circuit current density of 5.16 mA/cm2 and the maximum power conversion efficiency of 1.54% from a sample with sputtering time at 60 min while the reference cell exhibited 3.88 mA/cm2 and 1.19%, respectively. Thus, we suggested an alternative improvement of ZnO DSSCs by adding the ZnO anti-reflection coating layers.

  4. Epitaxial growth of Ce 2Y 2O 7 buffer layers for YBa 2Cu 3O 7-δ coated conductors using reel-to-reel DC reactive sputtering

    NASA Astrophysics Data System (ADS)

    Fan, F.; Lu, Y. M.; Ying, L. L.; Liu, Z. Y.; Cai, C. B.; Hühne, R.; Holzapfel, B.

    2011-08-01

    Biaxially textured Ce 2Y 2O 7 (CYO) films were deposited on Ni-5at.%W (Ni-5W) tapes by a DC reactive sputtering technique in a reel-to-reel system. Subsequent YBa 2Cu 3O 7-δ (YBCO) films were prepared using pulsed laser deposition leading to a simplified coated conductor architecture of YBCO/CYO/Ni-5W. X-ray diffraction measurements revealed an epitaxial growth of the CYO buffer layer with a texture spread down to 2.2° and 4.7° for the out-of-plane and in-plane alignment, respectively. Microstructural investigations showed a dense, smooth and crack-free surface morphology for CYO film up to a thickness of 350 nm, implying an effective suppression of cracks due to the incorporation of Y in CeO 2. The superconducting transition temperature T c of about 90 K with a narrow transition of 0.8 K and the inductively measured critical current density J c of about 0.7 MA/cm 2 indicate the potential of the single CYO buffer layer.

  5. Synthesis of low resistive p type Cu4O3 thin films by DC reactive magnetron sputtering and conversion of Cu4O3 into CuO by laser irradiation

    NASA Astrophysics Data System (ADS)

    Murali, Dhanya S.; Subrahmanyam, A.

    2016-09-01

    Copper oxide thin films are a topic of intense investigation by several researchers. Copper reacting with oxygen, depending upon the available energy, forms CuO, Cu2O and Cu4O3 phases. Among these, Cu4O3 is a difficult phase to prepare. In the present communication, we report the preparation and properties of the stable phase of Cu4O3. These Cu4O3 thin films have been prepared at room temperature (300 K) on borosilicate glass by reactive DC magnetron sputtering. Cu4O3 thin films (of thickness 265  ±  5 nm) are p-type semiconductors (hole density 2.4  ×  1018 cc‑1 and Hall mobility 0.04 cm2 V‑1 s‑1) and show a low resistivity (55 Ω cm). They have a direct band gap of 2.34 eV and an indirect band gap of 1.50 eV. The surface work function of Cu4O3 (measured by Kelvin Probe technique) is 5.35  ±  0.01 eV. Cu4O3 films are irradiated with laser radiation of 532 nm wavelength and 10 MW cm‑2 (120 s) power density. It shows a phase transformation to CuO which is confirmed by the Raman Spectroscopy measurements.

  6. Epitaxial growth of In{sub x}Ga{sub 1-x}N alloy films on sapphire and silicon by reactive co-sputtering of GaAs and indium

    SciTech Connect

    Mohan, Shyam Major, S. S.; Srinivasa, R. S.

    2015-06-24

    In{sub x}Ga{sub 1-x}N alloy films (0.2reactive co-sputtering of GaAs and indium with 100% nitrogen at a substrate temperature of 600 °C. X-ray diffraction studies show the formation of completely c-axis oriented, single phase alloy films over the studied range of composition. The crystallite size along the growth direction and surface morphology of alloy films, particularly those with higher indium fraction exhibit substantial improvement on Si (100) substrate, compared to the c-cut sapphire substrate. The electrical resistivity decreases monotonously with increase in indium fraction and the alloy films on Si (100) show substantially higher mobility, compared to those on sapphire. These features are attributed to superior crystallinity of alloy films on Si (100), which possibly arise from the formation of interfacial hexagonal α-Si{sub 3}N{sub 4}, owing to the interaction of nitrogen plasma with Si surface.

  7. Synthesis of low resistive p type Cu4O3 thin films by DC reactive magnetron sputtering and conversion of Cu4O3 into CuO by laser irradiation

    NASA Astrophysics Data System (ADS)

    Murali, Dhanya S.; Subrahmanyam, A.

    2016-09-01

    Copper oxide thin films are a topic of intense investigation by several researchers. Copper reacting with oxygen, depending upon the available energy, forms CuO, Cu2O and Cu4O3 phases. Among these, Cu4O3 is a difficult phase to prepare. In the present communication, we report the preparation and properties of the stable phase of Cu4O3. These Cu4O3 thin films have been prepared at room temperature (300 K) on borosilicate glass by reactive DC magnetron sputtering. Cu4O3 thin films (of thickness 265  ±  5 nm) are p-type semiconductors (hole density 2.4  ×  1018 cc-1 and Hall mobility 0.04 cm2 V-1 s-1) and show a low resistivity (55 Ω cm). They have a direct band gap of 2.34 eV and an indirect band gap of 1.50 eV. The surface work function of Cu4O3 (measured by Kelvin Probe technique) is 5.35  ±  0.01 eV. Cu4O3 films are irradiated with laser radiation of 532 nm wavelength and 10 MW cm-2 (120 s) power density. It shows a phase transformation to CuO which is confirmed by the Raman Spectroscopy measurements.

  8. Epitaxial growth of γ-Al{sub 2}O{sub 3} on Ti{sub 2}AlC(0001) by reactive high-power impulse magnetron sputtering

    SciTech Connect

    Eklund, Per Frodelius, Jenny; Hultman, Lars; Lu, Jun; Magnfält, Daniel

    2014-01-15

    Al{sub 2}O{sub 3} was deposited by reactive high-power impulse magnetron sputtering at 600 °C onto pre-deposited Ti{sub 2}AlC(0001) thin films on α-Al{sub 2}O{sub 3}(0001) substrates. The Al{sub 2}O{sub 3} was deposited to a thickness of 65 nm and formed an adherent layer of epitaxial γ-Al{sub 2}O{sub 3}(111) as shown by transmission electron microscopy. The demonstration of epitaxial growth of γ-Al{sub 2}O{sub 3} on Ti{sub 2}AlC(0001) open prospects for growth of crystalline alumina as protective coatings on Ti{sub 2}AlC and related nanolaminated materials. The crystallographic orientation relationships are γ-Al{sub 2}O{sub 3}(111)//Ti{sub 2}AlC(0001) (out-of-plane) and γ- Al {sub 2}O{sub 3}(22{sup ¯}0)// Ti {sub 2} AlC (112{sup ¯}0) (in-plane) as determined by electron diffraction. Annealing in vacuum at 900 °C resulted in partial decomposition of the Ti{sub 2}AlC by depletion of Al and diffusion into and through the γ-Al{sub 2}O{sub 3} layer.

  9. Structural and electrical properties of reactively sputtered InN thin films on AlN-buffered (00.1) sapphire substrates: Dependence on buffer and film growth temperatures and thicknesses

    NASA Astrophysics Data System (ADS)

    Kistenmacher, T. J.; Ecelberger, S. A.; Bryden, W. A.

    1993-08-01

    An extensive investigation of InN overlayers on AlN-buffered (00.1) sapphire by reactive magnetron sputtering has been undertaken and the dependencies of several basic materials properties (film thickness, development and quality of heteroepitaxy, film morphology, and electrical transport) on such key deposition parameters such as the growth temperatures of the insulating AlN buffer layer and the InN overlayer and their thicknesses have been determined. Three prominent effects of the AlN buffer layer are (1) the stabilization of heteroepitaxial growth over a broad range of film and buffer layer growth temperatures; (2) the attainment of a higher Hall mobility (up to 60 cm2/V s) over much of the same range; and, (3) the retention of heteroepitaxial growth, higher Hall mobility, and pseudo-two-dimensional growth even in the limit of an InN layer of ˜40 Å. In the context of a structure-zone model, the AlN buffer layer is projected to effectively raise the growth temperature of the InN thin film. The increase in effective growth temperature is, however, insufficient to overcome low atomic and cluster mobility and to achieve single-crystal InN thin film growth.

  10. Growth, structural and optoelectronic properties tuning of nitrogen-doped ZnO thin films synthesized by means of reactive pulsed laser deposition

    SciTech Connect

    Naouar, M.; Ka, I.; Gaidi, M.; Alawadhi, H.; Bessais, B.; Khakani, M.A.El

    2014-09-15

    Highlights: • PLD technique has been used to elaborate N doped ZnO. • A maximum incorporation of 0.7 at.% has been achieved at a pressure of 25 mTorr. • Increasing the N{sub 2} pressure decreases the nitrogen content with the creation of more defects. • Optical transmission and PL spectra have confirmed the band gap narrowing. - Abstract: Pulsed laser deposition has been successfully used to achieve in-situ nitrogen doping of zinc oxide thin films at a temperature as low as 300 °C. Nitrogen-doped zinc oxide (ZnO:N) thin films with a maximum nitrogen content of 0.7 at.% were obtained by varying the nitrogen background pressure in the range of 0–150 mTorr. The ZnO:N thin films were found to present hexagonal crystalline structure with dense and smooth surface. X-ray photoelectron spectroscopy analysis confirms the effective incorporation of nitrogen into ZnO thin films. Optical transmission together with room temperature photoluminescence measurements show that the band gap of the ZnO:N films shifts from 3.3 eV to 3.1 eV as nitrogen concentration varies in the range of 0.2–0.7 at.%. The narrower band gap is obtained at an optimal nitrogen concentration of 0.22 at.%. This band gap narrowing is found to be caused by both nitrogen incorporation and nitrogen-induced defects in the ZnO:N films.

  11. Transport Phenomena of Off-Axis Sputtering Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, S.; Su, C. H.; Lehoczky, S. L.; Zhang, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Various high quality epitaxial films, especially oxides, have been synthesized using off-axis sputtering deposition. In this presentation, we report the experiment results of ZnO films grown by the off-axis sputtering deposition. Films were synthesized in temperatures ranged from room temperature to 600 C, and pressures from 5 mTorr to 150 mTorr. Film growth rate was measured by surface profilometer, ellipsometer, and wavelength dispersive spectrometry. Due to the collisions between the sputtered species and the residue gases, the kinetic energy of species was reduced and the transport of depositing species changed from a ballistic movement for low pressure to a diffuse drift for high pressure in which the transport species were almost thermalized. The measurements show an increase of growth rates along the gravity vector when the Knodson (Knudsen??) number of transport species is less than 0.05, which suggests that gravity affected the transport characterization in off-axis sputtering deposition. Because the product of pressure (p) and travel distance (d) of sputtered species, p exceeds several mTorr-cm during film deposition, the classical simulations for sputtering process in high vacuum system may not be applied. Based on these experimental measurements, a transport process of the off-axis sputtering deposition is proposed. Several methods including the Monte Carlo method and gravity-driven flow dynamics simulation will be discussed.

  12. Preparation of ZnO Thin Films on Free-Standing Diamond Substrates

    NASA Astrophysics Data System (ADS)

    Tang, Ke; Wang, Linjun; Huang, Jian; Xu, Run; Lai, Jianming; Wang, Jun; Min, Jiahua; Shi, Weimin; Xia, Yiben

    2009-10-01

    Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction (XRD) measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to-O2 composition of 1:1, a higher intensity of the (002) diffraction peak and a narrower full width at half maximum (FWHM) were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film.

  13. Comparison of the Sputter Rates of Oxide Films Relative to the Sputter Rate of SiO2

    SciTech Connect

    Baer, Donald R.; Engelhard, Mark H.; Lea, Alan S.; Nachimuthu, Ponnusamy; Droubay, Timothy C.; Kim, J.; Lee, B.; Mathews, C.; Opila, R. L.; Saraf, Laxmikant V.; Stickle, William F.; Wallace, Robert; Wright, B. S.

    2010-09-02

    Because of the increasing technological importance of oxide films for a variety of applications, there is a growing interest in knowing the sputter rates for a wide variety of oxides. To support needs of users of the Environmental Molecular Sciences Laboratory (EMSL) User facility as well as our research programs, we have made a series of measurements of the sputter rates for oxide films that have been grown by oxygen plasma assisted molecular beam epitaxy (OPA-MBE), pulsed laser deposition (PLD), Atomic Layer Deposition (ALD), electrochemical oxidation, or sputter deposition. The sputter rates for these oxide films were determined in comparison to the sputter rates for thermally grown SiO2, a common sputter rate reference material. The film thicknesses and densities of these films were usually measured using x-ray reflectivity (XRR). These samples were mounted in an x-ray photoelectron spectroscopy (XPS) system or an Auger electron spectrometer for sputtering measurements using argon ion sputtering. Although the primary objective was to determine relative sputter rates at a fixed angle, the measurements were also used to determine: i) the angle dependence of the relative sputter rates; ii) the energy dependence of the relative sputter rates; and iii) the extent of ion beam reduction for the various oxides. Materials examined include: SiO2 (reference films), Al2O3, CeO2, Cr2O3, Fe2O3, HfO2, ITO (In-Sn-oxide) Ta2O5, TiO2 (anatase and rutile) and ZnO. We find that the sputter rates for the oxides can vary up to a factor of two (usually slower) from that observed for SiO2. The ratios of sputter rates to SiO2 appear to be relatively independent of ion beam energy for the range of 1kV to 4 kV and for incident angles of less than 50º. As expected, the ion beam reduction of the oxides varies with the sputter angle. These studies demonstrate that we can usually obtain sputter rate reproducibility better than 5% for similar oxide films.

  14. Effect of a ga-doped ZnO thin film with a ZTO buffer layer fabricated by using pulsed DC magnetron sputter for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Song, Sang-Woo; Lee, Kyung-Ju; Roh, Ji-Hyung; Park, On-Jeon; Kim, Hwan-Sun; Moon, Byung-Moo; Ji, Min-Woo

    2014-08-01

    The electrical property of a Ga-doped ZnO(GZO) thin film is well known to be similar that of commercialized fluorine-doped tin oxide(FTO). However GZO is limited for use at high process temperatures for solar cells because of its unstable resistivity at temperatures above 300 °C. A GZO thin film compared to zinc tin oxide(ZTO)-GZO multilayer can be used at high process temperatures. A GZO thin film was deposited on glass by using pulsed DC magnetron sputter. Then, a ZTO buffer layer was deposited on the GZO surface. During the deposition, the working pressure was 5 mTorr (Z-1 glass) and 1 mTorr (Z-2 glass). Dye-sensitized solar cells (DSSCs) were fabricated using Z-1, Z-2 and commercialized FTO glasses. Z-2 showed a conversion efficiency of 4.265%, which was enhanced by 0.399% compared to that of the DSSCs using FTO(3.784%). The conversion efficiency for Z-1 (3.889%) was a little higher than that of FTO. Thus, the ZTO-GZO electrode showed better characteristics than those obtained using the FTO electrode, which can be attributed to the reduced charge recombination and series resistance.

  15. Merits and Demerits of Transparent Conducting Magnetron Sputtered ZnO:Al, ITO and SnO2:F Thin Films for Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Das, Rajesh; Das, Himadri Sekhar

    2016-06-01

    Transparent conducting ZnO:Al and indium tin oxide (ITO) thin films were deposited by magnetron sputtering under reactive environment. Both the transparent conducting oxide (TCO) films were exposed intentionally in hydrogen environment at 350 °C calcinations temperature to study the post treated TCO film's opto-electronic, structural as well as surface morphological properties. Electrical resistivity of both ZnO:Al, ITO and SnO2:F films are comparable (order of 10-4 Ω-cm), lowest sheet resistance are 8.5, 3.7 and 4.6 Ω/sq respectively and slightly improved after hydrogen exposure at 350 °C. Optical transmittance and internal texture of hydrogen environment exposed ZnO films remains invariant, but in case of ITO, SnO2:F films optical transmittance deteriorated drastically. Hexagonal wurtzite structure with (002) c-axis orientation is observed for pre- and post-hydrogen exposed ZnO films whereas internal texture as well as crystallographic orientation of ITO and SnO2:F films have significantly changed. Surface grains of ITO films have been significantly enhanced, but no such variations are observed in ZnO surface morphology. ZnO:Al and ITO films show unique plasmonic properties in near infrared transmittance due to free carrier generation in conduction band. Based on surface features/morphology, haze factor and internal texture light scattering mechanism is modeled.

  16. Microstructural and optical properties of nanocrystalline ZnO deposited onto vertically aligned carbon nanotubes by physical vapor deposition

    SciTech Connect

    Borkar, Tushar; Chang, Won Seok; Hwang, Jun Yeon; Shepherd, Nigel D.; Banerjee, Rajarshi

    2012-10-15

    Nanocrystalline ZnO films with thicknesses of 5 nm, 10 nm, 20 nm, and 50 nm were deposited via magnetron sputtering onto the surface of vertically aligned multi-walled carbon nanotubes (MWCNTs). The ZnO/CNTs heterostructures were characterized by scanning electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction studies. No structural degradation of the CNTs was observed and photoluminescence (PL) measurements of the nanostructured ZnO layers show that the optical properties of these films are typical of ZnO deposited at low temperatures. The results indicate that magnetron sputtering is a viable technique for growing heterostructures and depositing functional layers onto CNTs.

  17. A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques

    SciTech Connect

    Yadav, Harish Kumar; Gupta, Vinay

    2012-05-15

    Photoresponse characteristics of ZnO thin films deposited by three different techniques namely rf diode sputtering, rf magnetron sputtering, and electrophoretic deposition has been investigated in the metal-semiconductor-metal (MSM) configuration. A significant variation in the crystallinity, surface morphology, and photoresponse characteristics of ZnO thin film with change in growth kinetics suggest that the presence of defect centers and their density govern the photodetector relaxation properties. A relatively low density of traps compared to the true quantum yield is found very crucial for the realization of practical ZnO thin film based ultraviolet (UV) photodetector.

  18. Fabrication and characterization of ZnO nanowire structure on flexible substrate with different solution molarities

    NASA Astrophysics Data System (ADS)

    Lee, Kyu-Hang; Hur, Shin; Kim, Wan-Doo; Choi, Hongsoo

    2010-08-01

    Zinc Oxide nanostructures are capable of applying numerous applications such as optoelectronics, sensors, varistors, and electronic devices. There are several techniques to gorw ZnO nanostructures, including vapor-liquid-solid method, chemical vapor deposition, physical vapor deposition, metal organic chemical vapor deposition and solution process. Recently reported solution method is a simple way to grow ZnO nanowires at a low temperature. One distinctive advantage with the solution method is low processing temperature so that flexible polymer materials can be used as a substrate to grow ZnO nanowires. In this study, ZnO nanowires have been fabricated on PET film by solution method with various molarities to see the effect of different molarities on ZnO nanowire growth. The solution temperature was 80°C and ZnO nanowires were grown for 6 hours for each case. The ZnO seed layer was sputtered at room temperature for 33 min. prior to ZnO nanowire growth. These ZnO nanowires were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) measurements at room temperature using a He-Cd 325-nm laser as the excitation source. We also measured the current using current Atomic Force Microscopy (I-AFM) and presented the possibility to use ZnO nanowires as a power source for micro/nano scale devices. As a result, we found that the characterization of ZnO nanowires changes according to the solution molarity.

  19. Self-focused ZnO transducers for ultrasonic biomicroscopy

    SciTech Connect

    Cannata, J. M.; Williams, J. A.; Zhou, Q. F.; Sun, L.; Shung, K. K.; Yu, H.; Kim, E. S.

    2008-04-15

    A simple fabrication technique was developed to produce high frequency (100 MHz) self-focused single element transducers with sputtered zinc oxide (ZnO) crystal films. This technique requires the sputtering of a ZnO film directly onto a curved backing substrate. Transducers were fabricated by sputtering an 18 {mu}m thick ZnO layer on 2 mm diameter aluminum rods with ends shaped and polished to produce a 2 mm focus or f-number equal to one. The aluminum rod served a dual purpose as the backing layer and positive electrode for the resultant transducers. A 4 {mu}m Parylene matching layer was deposited on the transducers after housing and interconnect. This matching layer was used to protect the substrate and condition the transfer of acoustic energy between the ZnO film and the load medium. The pulse-echo response for a representative transducer was centered at 101 MHz with a -6 dB bandwidth of 49%. The measured two way insertion loss was 44 dB. A tungsten wire phantom and an adult zebrafish eye were imaged to show the capability of these transducers.

  20. Annihilation of Leishmania by daylight responsive ZnO nanoparticles: a temporal relationship of reactive oxygen species-induced lipid and protein oxidation

    PubMed Central

    Nadhman, Akhtar; Khan, Malik Ihsanullah; Nazir, Samina; Khan, Momin; Shahnaz, Gul; Raza, Abida; Shams, Dilawar Farhan; Yasinzai, Masoom

    2016-01-01

    Lipid and protein oxidation are well-known manifestations of free radical activity and oxidative stress. The current study investigated extermination of Leishmania tropica promastigotes induced by lipid and protein oxidation with reactive oxygen species produced by PEGylated metal-based nanoparticles. The synthesized photodynamic therapy-based doped and nondoped zinc oxide nanoparticles were activated in daylight that produced reactive oxygen species in the immediate environment. Lipid and protein oxidation did not occur in dark. The major lipid peroxidation derivatives comprised of conjugated dienes, lipid hydroperoxides, and malondialdehyde whereas water, ethane, methanol, and ethanol were found as the end products. Proteins were oxidized to carbonyls, hydroperoxides, and thiol degrading products. Interestingly, lipid hydroperoxides were produced by more than twofold of the protein hydroperoxides, indicating higher degradation of lipids compared to proteins. The in vitro evidence represented a significant contribution of the involvement of both lipid and protein oxidation in the annihilated antipromastigote effect of nanoparticles. PMID:27330288

  1. Ion beam sputter etching

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.

    1986-01-01

    An ion beam etching process which forms extremely high aspect ratio surface microstructures using thin sputter masks is utilized in the fabrication of integrated circuits. A carbon rich sputter mask together with unmasked portions of a substrate is bombarded with inert gas ions while simultaneous carbon deposition occurs. The arrival of the carbon deposit is adjusted to enable the sputter mask to have a near zero or even slightly positive increase in thickness with time while the unmasked portions have a high net sputter etch rate.

  2. Structural and optical properties of zinc oxide film using RF-sputtering technique

    SciTech Connect

    Hashim, A. J.; Jaafar, M. S.; Ghazai, Alaa J.

    2012-11-27

    This paper reports the fabrication of zinc oxide (ZnO) film using RF-sputtering technique. Determination of the structural properties using High Resolution X-ray Diffraction (HRXRD) confirmed that ZnO film deposited on silicon (Si) substrate has a high quality. This result is in line with the Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) which were used to image the morphology of the film, in which a rough surface was demonstrated. Photoluminescence (PL) emission is included to study the optical properties of ZnO film that shows two PL peak in the UV region at 371 nm and in visible region at 530 nm respectively.

  3. Room Temperature Ferromagnetism in Cu Doped ZnO Thin Films

    SciTech Connect

    Khan, Zaheer Ahmed; Ghosh, Subhasis

    2011-07-15

    We report on the growth of Cu doped ZnO thin films for different Cu concentration from 0.1%, to10% by RF magnetron sputtering. The X-ray diffraction study has shown single phase wurtzite type ZnO thin films with no evidence of copper/copper oxide or any other secondary phases. Room temperature ferromagnetism was observed in RF sputtered Cu doped ZnO films with magnetic moment per Cu atom first increasing and then decreasing with an increasing Cu content. Decrease of band gap with Cu doping, indicating strong p-d mixing of O and Cu is clear by the absorption spectroscopy study. The surface morphology by AFM of pure and Cu doped ZnO thin films show average grain size of 110nm and RMS surface roughness of 2.15 nm.

  4. Comparison of the sputter rates of oxide films relative to the sputter rate of SiO{sub 2}

    SciTech Connect

    Baer, D. R.; Engelhard, M. H.; Lea, A. S.; Nachimuthu, P.; Droubay, T. C.; Kim, J.; Lee, B.; Mathews, C.; Opila, R. L.; Saraf, L. V.; Stickle, W. F.; Wallace, R. M.; Wright, B. S.

    2010-09-15

    There is a growing interest in knowing the sputter rates for a wide variety of oxides because of their increasing technological importance in many different applications. To support the needs of users of the Environmental Molecular Sciences Laboratory, a national scientific user facility, as well as our research programs, the authors made a series of measurements of the sputter rates from oxide films that have been grown by oxygen plasma-assisted molecular beam epitaxy, pulsed laser deposition, atomic layer deposition, electrochemical oxidation, or sputter deposition. The sputter rates for these oxide films were determined in comparison with those from thermally grown SiO{sub 2}, a common reference material for sputter rate determination. The film thicknesses and densities for most of these oxide films were measured using x-ray reflectivity. These oxide films were mounted in an x-ray photoelectron or Auger electron spectrometer for sputter rate measurements using argon ion sputtering. Although the primary objective of this work was to determine relative sputter rates at a fixed angle, the measurements also examined (i) the angle dependence of the relative sputter rates, (ii) the energy dependence of the relative sputter rates, and (iii) the extent of ion beam induced reduction for some oxides. Oxide films examined include SiO{sub 2}, Al{sub 2}O{sub 3}, CeO{sub 2}, Cr{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}, HfO{sub 2}, In-Sn oxide, Ta{sub 2}O{sub 5}, TiO{sub 2} (anatase, rutile, and amorphous), and ZnO. The authors found that the sputter rates for the oxides can vary up to a factor of 2 (usually lower) from that observed for SiO{sub 2}. The ratios of sputter rates relative to those of SiO{sub 2} appear to be relatively independent of ion beam energy in the range of 1-4 kV and for incident angles <50 deg. As expected, the extent of ion beam induced reduction of the oxides varies with the sputter angle.

  5. Characterization of ZnO Thin Films Prepared by Thermal Oxidation of Zn

    NASA Astrophysics Data System (ADS)

    Bouanane, I.; Kabir, A.; Boulainine, D.; Zerkout, S.; Schmerber, G.; Boudjema, B.

    2016-07-01

    Zinc oxide thin films were prepared by thermal oxidation of zinc films at a temperature of 500°C for 2 h. The Zn films were deposited onto glass substrates by magnetron RF sputtering. The sputtering time varied from 2.5 min to 15 min. The physico-chemical characterization of the ZnO films was carried out depending on the Zn sputtering time. According to x-ray diffraction, ZnO films were polycrystalline and the Zn-ZnO phase transformation was direct. The mean transmittance of the ZnO films was around 80% and the band gap increased from 3.15 eV to 3.35 eV. Photoluminescence spectra show ultraviolet, visible, and infrared emission bands. The increase of the UV emission band was correlated with the improvement of the crystalline quality of the ZnO films. The concentration of native defects was found to decrease with increasing Zn sputtering time. The decrease of the electrical resistivity as a function of Zn sputtering time was linked to extrinsic hydrogen-related defects.

  6. Characterization of Flexible CIGS Thin Film Solar Cells or Stainless Steel with Intrinsic ZnO Diffusion Barriers.

    PubMed

    Kim, Chae-Woong; Kim, Hye Jin; Kim, Jin Hyeok; Jeong, Chaehwan

    2016-05-01

    ZnO diffusion barrier layer was deposited by RF magnetron sputtering by using the same method as intrinsic ZnO layer. The CIGS solar cells were fabricated on stainless steel substrate. The 50-200 nm thin ZnO diffusion barriers effectively reduced the diffusion of Fe and Cr, from stainless steel substrates into the CIGS absorbers. The CIGS solar cells with ZnO diffusion barriers increased the J(sc) and FF, which resulted in an increase of cell efficiency from 5.9% up to 9.06%. PMID:27483885

  7. A reactive magnetron sputtering route for attaining a controlled core-rim phase partitioning in Cu{sub 2}O/CuO thin films with resistive switching potential

    SciTech Connect

    Ogwu, A. A.; Darma, T. H.

    2013-05-14

    The achievement of a reproducible and controlled deposition of partitioned Cu{sub 2}O/CuO thin films by techniques compatible with ULSI processing like reactive magnetron sputtering has been reported as an outstanding challenge in the literature. This phase partitioning underlies their performance as reversible resistive memory switching devices in advanced microelectronic applications of the future. They are currently fabricated by thermal oxidation and chemical methods. We have used a combination of an understanding from plasma chemistry, thermo-kinetics of ions, and rf power variation during deposition to successfully identify a processing window for preparing partitioned Cu{sub 2}O/CuO films. The production of a core rich Cu{sub 2}O and surface rich Cu{sub 2}O/CuO mixture necessary for oxygen migration during resistive switching is confirmed by XRD peaks, Fourier transform infra red Cu (I)-O vibrational modes, XPS Cu 2P{sub 3/2} and O 1S peak fitting, and a comparison of satellite peak ratio's in Cu 2P{sub 3/2} fitted peaks. We are proposing based on the findings reported in this paper that an XPS satellite peak intensity(I{sub s}) to main peak intensity ratio (I{sub m}) {<=} 0.45 as an indicator of a core rich Cu{sub 2}O and surface rich Cu{sub 2}O/CuO formation in our prepared films. CuO is solely responsible for the satellite peaks. This is explained on the basis that plasma dissociation of oxygen will be limited to the predominant formation of Cu{sub 2}O under certain plasma deposition conditions we have identified in this paper, which also results in a core-rim phase partitioning. The deposited films also followed a Volmer-Weber columnar growth mode, which could facilitate oxygen vacancy migration and conductive filaments at the columnar interfaces. This is further confirmed by optical transmittance and band-gap measurements using spectrophotometry. This development is expected to impact on the early adoption of copper oxide based resistive memory

  8. REACTIVE SPUTTERING OF NANOSTRUCTURED WCX. (R829624)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. Influence of homo buffer layer thickness on the quality of ZnO epilayers.

    PubMed

    Eid, E A; Fouda, A N

    2015-10-01

    ZnO buffer layers with different thicknesses were deposited on a-plane sapphire substrates at 300 °C. ZnO epilayers were grown on ZnO buffers at 600 °C by radio-frequency magnetron sputtering and vacuum annealed at 900 °C for an hour. Influence of nucleation layer thickness on the structural and quality of ZnO thin films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and Raman spectroscopy. The best ZnO film quality was obtained with the ZnO buffer layer of 45 nm thick which provided the smoothest surface with RMS value of 0.3 nm. X-ray diffraction measurements reveal that the films have a single phase wurtzite structure with (0001) preferred crystal orientation. As evident from narrow FWHM of ZnO (0002) rocking curve, ZnO buffer can serve as a good template for the growth of high-quality ZnO films with little tilt. In addition, the micro-Raman scattering measurements at room temperature revealed the existence of Raman active phonon modes of ZnO; A1(TO), A1(LO) and E2(high). The latter two modes were not observed in thin buffer layer beside the dis-appearance of E2(low) mode in all films. PMID:25950638

  10. All-sputtered 14% CdS/CdTe thin-film solar cell with ZnO:Al transparent conducting oxide

    SciTech Connect

    Gupta, Akhlesh; Compaan, Alvin D.

    2004-07-26

    Radio-frequency (rf)-sputtered Al-doped ZnO was used as the transparent front contact in the fabrication of high efficiency superstrate configuration CdS/CdTe thin-film solar cells. These cells had CdS and CdTe layers also deposited by rf sputtering at 250 deg. C with the highest processing temperature of 387 deg. C reached during a post-deposition treatment. The devices were tested at National Renewable Energy Laboratory and yielded an efficiency of 14.0%, which is excellent for a CdTe cell using ZnO and also for any sputtered CdTe solar cell. The low-temperature deposition process using sputtering for all semiconductor layers facilitates the use of ZnO and conveys significant advantages for the fabrication of more complex multiple layers needed for the fabrication of tandem polycrystalline solar cells and for cells on polymer materials.

  11. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells

    PubMed Central

    Tseng, Zong-Liang; Chiang, Chien-Hung; Wu, Chun-Guey

    2015-01-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. PMID:26411577

  12. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells.

    PubMed

    Tseng, Zong-Liang; Chiang, Chien-Hung; Wu, Chun-Guey

    2015-01-01

    Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. PMID:26411577

  13. Sputtering of uranium

    NASA Technical Reports Server (NTRS)

    Gregg, R.; Tombrello, T. A.

    1978-01-01

    Results are presented for an experimental study of the sputtering of U-235 atoms from foil targets by hydrogen, helium, and argon ions, which was performed by observing tracks produced in mica by fission fragments following thermal-neutron-induced fission. The technique used allowed measurements of uranium sputtering yields of less than 0.0001 atom/ion as well as yields involving the removal of less than 0.01 monolayer of the uranium target surface. The results reported include measurements of the sputtering yields for 40-120-keV protons, 40-120-keV He-4(+) ions, and 40- and 80-keV Ar-40(+) ions, the mass distribution of chunks emitted during sputtering by the protons and 80-keV Ar-40(+) ions, the total chunk yield during He-4(+) sputtering, and some limited data on molecular sputtering by H2(+) and H3(+). The angular distribution of the sputtered uranium is discussed, and the yields obtained are compared with the predictions of collision cascade theory.

  14. Synthesis, characterization and photocatalytic activity of PVP stabilized ZnO and modified ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Bandekar, Gauri; Rajurkar, N. S.; Mulla, I. S.; Mulik, U. P.; Amalnerkar, D. P.; Adhyapak, P. V.

    2013-01-01

    In the present study, ZnO nanostructures have been successfully synthesized by hydrothermal, sonochemical and precipitation methods using polyvinyl pyrrolidone (PVP) as the capping agent. The ZnO nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Visible spectroscopy and photoluminescence (PL) techniques. The XRD results revealed the hexagonal wurtzite structure of the ZnO nanostructures for all the samples. Furthermore, the morphology of the ZnO particles was obtained from FESEM micrographs. Particles prepared by hydrothermal method were found to be rice grain shaped and that prepared by precipitation and sonochemical methods were spherical shaped. Sunlight driven photocatalytic degradation of methylene blue (MB) was studied for ZnO nanostructures synthesized by various methods. The ZnO nanostructures were further decorated with Ag nanoparticles to enhance its dye degradation efficiency. The Ag decorated ZnO nanoparticles exhibited a higher degradation rate as compared to pure ZnO nanoparticles which was independent of pH. Since this process of dye degradation relies on the degradation of dye due to oxidation by highly reactive hydroxyl radicals, there are many factors which affect the efficiency of this process. Hence a study was conducted on the effect of various parameters on ZnO viz amount of catalyst, reaction pH and concentration of MB dye.

  15. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1994-02-15

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material is described. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly. 11 figures.

  16. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1994-01-01

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly.

  17. Defects in room-temperature ferromagnetic Cu-doped ZnO films probed by x-ray absorption spectroscopy.

    PubMed

    Ma, Q; Prater, J T; Sudakar, C; Rosenberg, R A; Narayan, J

    2012-08-01

    We report a comprehensive study of the defects in room-temperature ferromagnetic (RTFM) Cu-doped ZnO thin films using x-ray absorption spectroscopy. The films are doped with 2 at.% Cu, and are prepared by reactive magnetron sputtering (RMS) and pulsed laser deposition (PLD), respectively. The results reveal unambiguously that atomic point defects exist in these RTFM thin films. The valence states of the Cu ions in both films are 2(+). In the film prepared by PLD, the oxygen vacancies (V(O)) form around both Zn ions and Cu ions in the hexagonal wurtzite structure. Upon annealing of the film in O(2), the V(O) population reduces and so does the RTFM. In the film prepared by RMS, the V(O)s around Cu ions are not detected, and the V(O) population around Zn ions is also smaller than in the PLD-prepared film. However, zinc vacancies (V(Zn)) are evidenced. Given the low doping level of spin-carrying Cu ions, these results provide strong support for defect-mediated ferromagnetism in Cu-doped ZnO thin films.

  18. Investigation of thin ZnO layers in view of laser desorption-ionization

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Georgieva, V. B.; Alimpiev, S. S.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Dimova-Malinovska, D.; Angelov, O. I.

    2010-04-01

    Thin zinc oxide films (ZnO) were developed as a matrix-free platform for surface assisted laser desorption-ionization (SALDI) time-of-flight mass spectrometry. The ZnO films were deposited by RF magnetron sputtering of ZnO ceramic targets in Ar atmospheres on monocrystalline silicon. The generation under UV (355 nm) laser irradiation of positive ions of atenolol, reserpine and gramicidin S from the ZnO layers deposited was studied. All analytes tested were detected as protonated molecules with no or very structure-specific fragmentation. The mass spectra obtained showed low levels of chemical background noise. All ZnO films studied exhibited high stability and good reproducibility. The detection limits for test analytes are in the 10 femtomol range.

  19. Effect of ZnO buffer layer on the cathodoluminescence of ZnGa 2O 4/ZnO phosphor screen for FED

    NASA Astrophysics Data System (ADS)

    Yang, Su-Hua; Hsueh, Ting-Jen; Chang, Shoou-Jinn

    2006-01-01

    A ZnGa 2O 4/ZnO phosphor screen for FED was prepared by RF magnetron sputtering. The ZnO buffer layer has a reasonable resistivity of about 5.2×10 3 Ω cm and a high transparency larger than 85%. The ZnGa 2O 4 phosphor was polycrystalline on ITO, yet it was amorphous on ZnO. If the ZnGa 2O 4/ZnO phosphor screen was annealed at temperatures above 300 °C, then ZnGa 2O 4 was crystallized. Owing to the lattice mismatch between ZnGa 2O 4 and ZnO, the grain size of ZnGa 2O 4 on ZnO was small. As a result, the effective emission area and luminescence of the ZnGa 2O 4/ZnO phosphor screen were enhanced. Auger electron spectroscopy (AES) examination showed that atoms in ZnO did not diffuse into ZnGa 2O 4 film, and the ZnGa 2O 4 was Zn-deficient. For charge balance, oxygen vacancy defects in the phosphor film were formed to compensate Zn deficiencies; consequently, the probability for electrons transfer from 2E B to 4A 2 of Ga energy levels was improved and the luminescence of the phosphor was increased.

  20. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciTech Connect

    Nandi, R. Mohan, S. Major, S. S.; Srinivasa, R. S.

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology and vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.

  1. Room temperature ferromagnetism in ZnO using non-magnetic dopants

    NASA Astrophysics Data System (ADS)

    Ali, Nasir; Atri, Asha; Singh, Budhi; Ghosh, Subhasis

    2016-05-01

    We studied the magnetic properties of Ag and Cu doped ZnO thin films deposited by magnetron sputtering. Robust room temperature ferromagnetism is observed in the films. Comparative to Cu doped films Ag doped films shows significant increase in ferromagnetism. Spectroscopic ellipsometry studies are also done to see the change in band structure with different metal doping content.

  2. The c-axis orientation ZnO by ICP enhanced HiPIMS at ambient temperature

    NASA Astrophysics Data System (ADS)

    Zhang, Haitao; chen, Jianyuan; Cherng, Jyhshiarn; Wang, Zhengduo; Liu, Zhongwei; Chen, Qiang

    2016-11-01

    In this paper, a facile method to prepare a high c-axis orientation ZnO film is reported. We combine a high power impulse magnetron sputtering (HiPIMS) with an inductively coupled plasma (ICP) in purpose of improving the reaction activity of Zn species sputtered from HiPIMS with dissociated oxygen, and gaining a high quality ZnO. The diagnostic of optical emission spectroscope (OES), which reveals the Zn+ and atomic oxygen concentrations in plasma, is evident the increasing ionization of Zn and the dissociation of O2 by ICP. After characterizing films grown with and without ICP, likely crystal through x-ray diffraction (XRD), component by energy dispersive spectroscopy (EDS), and morphology by atomic force microscope (AFM), we conclude that ICP assistance is crucial for the ZnO preferentially growth in (002) facet. With ICP assistance ZnO is grown in a big crystal size with a good quality.

  3. Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

    NASA Astrophysics Data System (ADS)

    Giri, Pushpa; Chakrabarti, P.

    2016-05-01

    Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

  4. RF Sputtering for preparing substantially pure amorphous silicon monohydride

    DOEpatents

    Jeffrey, Frank R.; Shanks, Howard R.

    1982-10-12

    A process for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicon produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous silicon hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  5. I-V Characteristic for ZnO MSM Photodetector with Pd Contact Electrodes on PPC Plastic

    SciTech Connect

    Jandow, N. N.; Ibrahim, K.; Hassan, H. Abu

    2010-07-07

    ZnO thin film was deposited on polypropylene carbonate (PPC) plastic substrate by direct current (DC) sputtering. The measurements of the absorption spectrum and the photoluminescence of the film were carried out. ZnO Metal-Semiconductor-Metal (MSM) photodetector with palladium (Pd) contact electrodes was then fabricated. The structural and electrical properties of the detector were investigated using the current-voltage (I-V) measurements.

  6. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1998-01-01

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence.

  7. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1998-06-16

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence. 8 figs.

  8. Physics of arcing, and implications to sputter deposition

    SciTech Connect

    Anders, Andre

    2005-03-15

    Arc and glow discharges are defined based on their cathode processes. Arcs are characterized by collective electron emission, which can be stationary with hot cathodes (thermionic arcs), or non-stationary with cold cathodes (cathodic arcs). A brief review on cathodic arc properties serves as the starting point to better understand arcing phenomena in sputtering. Although arcing occurs in both metal and reactive sputtering, it is more of an issue in the reactive case. Arcing occurs if sufficiently high field strength leads to thermal runaway of an electron emission site. The role of insulating layers and surface potential adjustment through current leakage is highlighted. In the situation of magnetron sputtering with ''racetrack'', the need for a model with two spatial dimensions is shown. In many cases, arcing is initiated by breakdown of dielectric layers and inclusions. It is most efficiently prevented if formation and excessive charge-up of dielectric layers and inclusions can be avoided.

  9. Contamination removal by ion sputtering

    NASA Astrophysics Data System (ADS)

    Shaw, Christopher G.

    1990-11-01

    Experimental investigations are described for ion-beam sputtering and RF-plasma sputtering to determine the effectiveness of the methods for removing contaminants from an optical surface. The effects of ion-beam sputtering are tested with an ion gun and measured by mounting a 5-MHz quartz-crystal microbalance on a sample holder and simulating spacecraft contamination. RF-plasma sputtering involves the application of an alternating electric field to opposing electrodes immersed in a low density gas, and is tested with the same setup. The energy dependence of the sputtering yields is measured to determine whether the different contaminants are removed and whether the mirror surface is affected. Ion-beam sputtering removes all contaminants tested, but also affects the mirror surface at high energies. When the correct DC bias is applied, RF sputtering can remove the contaminants without removing the metal-mirror surface.

  10. Defect-free ZnO nanorods for low temperature hydrogen sensor applications

    SciTech Connect

    Ranwa, Sapana; Kumar, Mahesh; Kulriya, Pawan K.; Sahu, Vikas Kumar; Kukreja, L. M.

    2014-11-24

    Uniformly distributed and defect-free vertically aligned ZnO nanorods (NRs) with high aspect ratio are deposited on Si by sputtering technique. X-ray diffraction along with transmission electron microscopy studies confirmed the single crystalline wurtzite structure of ZnO. Absence of wide band emission in photoluminescence spectra showed defect-free growth of ZnO NRs which was further conformed by diamagnetic behavior of the NRs. H{sub 2} sensing mechanism based on the change in physical dimension of channel is proposed to explain the fast response (∼21.6 s) and recovery times (∼27 s) of ZnO NRs/Si/ZnO NRs sensors. Proposed H{sub 2} sensor operates at low temperature (∼70 °C) unlike the existing high temperature (>150 °C) sensors.

  11. Performance analysis of RF-sputtered ZnO/Si heterojunction UV photodetectors with high photo-responsivity

    NASA Astrophysics Data System (ADS)

    Singh, Satyendra Kumar; Hazra, Purnima; Tripathi, Shweta; Chakrabarti, P.

    2016-03-01

    In this paper, structural, electrical and ultraviolet photodetection parameters of RF sputtered-ZnO/Si heterojunction diodes are analyzed. In this work, ZnO thin film was deposited on bare Si substrate as well as Si substrate coated with ultrathin ZnO seed layer to exhibit the effect of seed layer on device performance. AFM image of as-grown ZnO films have exhibited the uniform growth ZnO film over the whole Si substrate with average roughness of 3.2 nm and 2.83 nm for ZnO with and without seed layer respectively. Stronger peak intensity along (002) direction, as shown in XRD spectra confirm that ZnO film grown on ZnO seed layer is having more stable wurtzite structure. Ti/Al point contacts were deposited on top of the ZnO film and a layer of Al was deposited on bottom of Si substrate for using as ohmic contacts for further device characterization at dark and under UV light of 365 nm wavelength. This process is repeated for both the films sequentially. The photo-responsivity of our proposed devices is calculated as 0.34 A/W for seed layer-mediated devices and 0.26 A/W for devices without seed layer. These values are very high as compare to the reported value of photo-responsivity for same kind of ZnO/Si heterojunction device prototypes prepared by other techniques.

  12. Enhanced the photocatalytic activity of Ni-doped ZnO thin films: Morphological, optical and XPS analysis

    NASA Astrophysics Data System (ADS)

    Abdel-wahab, M. Sh.; Jilani, Asim; Yahia, I. S.; Al-Ghamdi, Attieh A.

    2016-06-01

    Pure and Ni-doped ZnO thin films with different concentration of Ni (3.5 wt%, 5 wt%, 7 wt%) were prepared by DC/RF magnetron sputtering technique. The X-rays diffraction pattern showed the polycrystalline nature of pure and Ni-doped ZnO thin films. The surface morphology of pure and Ni doped ZnO thin films were investigated through atomic force microscope, which indicated the increase in the grain dimension and surface roughness with increasing the Ni doping. The UV-Visible transmission spectra showed the decrease in the transmittance of doped ZnO thin films with the incorporation of Ni dopants. The surface and chemical state analysis of pure and Ni doped ZnO thin films were investigated by X-rays photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by an aqueous solution of methyl green dye. The tungsten lamp of 500 W was used as a source of visible light for photocatalytic study. The degradation results showed that the Ni-doped ZnO thin films exhibit highly enhanced photocatalytic activity as compared to the pure ZnO thin films. The enhanced photocatalytic activities of Ni-doped ZnO thin films were attributed to the enhanced surface area (surface defects), surface roughness and decreasing the band gap of Ni-doped ZnO thin films. Our work supports the applications of thin film metal oxides in waste water treatment.

  13. Influence of Mg doping on the morphology and optical properties of ZnO films for enhanced H₂ sensing.

    PubMed

    Vijayalakshmi, K; Karthick, K

    2013-11-01

    Highly oriented ZnO and Mg doped ZnO thin films were fabricated on Al2 O3 substrate by sputtering at room temperature. The effect of Mg doping on the structural, optical, and morphological properties of ZnO film was investigated. The intensity of (002) peak in X-ray diffraction measurements revealed the influence of Mg doping on the crystallinity and orientation of ZnO film. Photoluminescence (PL) results show that the Ultraviolet (UV) emission peak was shifted to lower wavelength side for Mg:ZnO film indicating the possibility for quantum confinement. UV-vis-NIR optical absorption revealed an improvement in optical transmittance from 70 to 85%, and corresponding optical band gap from 3.25 to 3.54 eV. Atomic force microscope (AFM) images revealed the nano-size particulate microstructure of the films. The surface topography of Mg doped ZnO film confirmed decreased grain size with large surface roughness and increased surface area, favorable for sensing. Pure ZnO and Mg doped ZnO film were used as active layer and tested for its sensing performance to hydrogen. Compared to undoped ZnO, 22 at.% Mg doped ZnO film showed much higher sensor response to H2 at a concentration as low as 200 ppm and at a lower operating temperature of 180°C. A linear sensor response was observed for H2 concentration in the range of 100-500 ppm.

  14. Photoconductivity of sputtered Cu/sub x/S films

    SciTech Connect

    McLeod, P.S.; Partain, L.D.; Sawyer, D.E.; Peterson, T.M.

    1984-08-15

    The optical band edge of reactively sputtered Cu/sub x/S films has been determined to be 1.18 +- 0.03 eV using a technique in which the conductance of the films with respect to the wavelength of the incident light was measured. These results were found to confirm optical absorption data on Cu/sub x/S films. Also, the efficiency of a 6.0% solar cell which was made using this sputtering technique is reported.

  15. Deposition rates of high power impulse magnetron sputtering: Physics and economics

    SciTech Connect

    Anders, Andre

    2010-07-15

    Deposition by high power impulse magnetron sputtering (HIPIMS) is considered by some as the new paradigm of advanced sputtering technology, yet this is met with skepticism by others for the reported lower deposition rates, if compared to rates of more conventional sputtering of equal average power. In this contribution, the underlying physical reasons for the rate changes are discussed, including (i) ion return to the target and self-sputtering, (ii) the less-than-linear increase in the sputtering yield with increasing ion energy, (iii) yield changes due to the shift of species responsible for sputtering, (iv) changes due to greater film density, limited sticking, and self-sputtering on the substrate, (v) noticeable power losses in the switch module, (vi) changes in the magnetic balance and particle confinement of the magnetron due to self-fields at high current, and (vii) superposition of sputtering and sublimation/evaporation for selected materials. The situation is even more complicated for reactive systems where the target surface chemistry is a function of the reactive gas partial pressure and discharge conditions. While most of these factors imply a reduction in the normalized deposition rate, increased rates have been reported for certain conditions using hot targets and less poisoned targets. Finally, some points of economics and HIPIMS benefits are considered.

  16. Enhanced ultraviolet photoresponse based on ZnO nanocrystals/Pt bilayer nanostructure

    NASA Astrophysics Data System (ADS)

    Tong, Xiao-Lin; Xia, Xiao-Zhi; Li, Qing-Xia

    2015-06-01

    The development of solution strategies for Zinc oxide (ZnO) quantum dots provides a pathway to utilizing ZnO nanocrystal thin films in optoelectronic devices. In this work, quasi-spherical ZnO quantum dots with a diameter of 5 nm are synthesized by using ethanol as a solvent. ZnO nanocrystal thin film is obtained by spin-coating ZnO quantum dots on a Au interdigital electrode (IDE)/Al2O3 substrate and annealing at different temperatures in order to yield the optimal photosensitive on/off ratio of ZnO. For further enhancing the responsivity, ion sputtering is utilized to deposit Pt nanoparticles on the surface of ZnO nanocrystal thin film, the responsivity of the ZnO/Pt bilayer nanostructure increases from 0.07 A/W to 54 A/W, showing that the metal/inorganic nanocrystal bilayer nanostructure can be used to improve the performance of optoelectronic devices. The excellent properties of ZnO/Pt bilayer nanostructure have important applications in future electronic and optoelectronic devices. Project supported by the National Natural Science Foundation of China (Grant No. 41176156).

  17. Electrical and Optical Properties of ZnO Films Grown on GaAs Substrates

    NASA Astrophysics Data System (ADS)

    Yuldashev, Shavkat U.; Panin, Gennady N.; Choi, Sung Woo; Yalishev, Vadim Sh.; Nosova, Ludmila A.; Ryu, Min Ki; Lee, Sanghern; Jang, Min Su; Chung, Kwan Soo; Kang, Tae Won

    2003-06-01

    Undoped ZnO films were deposited on GaAs substrates by conventional rf magnetron sputtering technique. After thermal annealing at temperatures of 500°C and higher for 20 min, the Hall coefficient of ZnO films on GaAs substrate becomes positive. The long-time annealing of 550 min at a temperature of 400°C also converts the sign of the Hall coefficient to positive. X-ray microanalysis shows that the diffusion of Zn atoms into the GaAs substrate and Ga atoms from the GaAs substrate into the ZnO film during thermal annealing occurs. The results of Hall measurements were analyzed by using the two-layer model of conductivity. It was shown that the positive sign of the Hall coefficient for the annealed ZnO film on the GaAs substrate is due to p-type conductivity of the GaAs substrate as a result of the diffusion of the Zn atoms from ZnO film into the GaAs substrate. With increasing annealing temperature or annealing time the ZnO films become more n-type due to the diffusion of Ga atoms from the GaAs substrate into the ZnO film.

  18. Enhanced band-edge photoluminescence from ZnO-passivated ZnO nanoflowers by atomic layer deposition

    PubMed Central

    2013-01-01

    The ZnO nanoflowers were synthesized by reactive vapor deposition. A secondary nucleation in the stalk/leaves interface was suggested. The photoluminescence revealed that there were many oxygen vacancies in the nanoflowers. To tune the optical properties of ZnO nanoflowers, ZnO thin films with varying thicknesses were coated on the nanoflowers by atomic layer deposition, which can distinctly improve the band-edge photoluminescence properties. PMID:23442577

  19. ZnO transparent conductive electrodes embedded with Pt nanoclusters for high-efficiency GaN-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Kyurin; Gil, Youngun; Jeong, Seonghoon; Oh, Munsik; Kim, Hyunsoo; Lee, Sung-Nam; Ahn, Kwang-Soon

    2016-01-01

    ZnO transparent conductive electrodes (TCEs) embedded with Pt nanoclusters were developed for the fabrication of reliable and efficient GaN-based light-emitting diodes (LEDs). The 200-nmthick ZnO films sputtered on Pt nanoclusters showed good TCE performance, i.e., a specific contact resistance of ˜10-5 Ωcm2, a sheet resistance of 50 Ω/sq, and an optical transmittance of 81.5% at 450 nm. LEDs fabricated with the ZnO TCEs embedded with Pt nanoclusters showed lower forward voltages and improved device reliability as compared to the reference LEDs fabricated with pure ZnO TCEs. This is attributed to the role of the interfacial Pt nanoclusters, suppressing the generation of sputtering surface damage on p-GaN and hence enhancing the carrier transport via Ohmic formation.

  20. Ion Beam Sputtered Coatings of Bioglass

    NASA Technical Reports Server (NTRS)

    Hench, Larry L.; Wilson, J.; Ruzakowski, Patricia Henrietta Anne

    1982-01-01

    The ion beam sputtering technique available at the NASA-Lewis was used to apply coatings of bioglass to ceramic, metallic, and polymeric substrates. Experiments in vivo and in vitro described investigate these coatings. Some degree of substrate masking was obtained in all samples although stability and reactivity equivalent to bulk bioglass was not observed in all coated samples. Some degree of stability was seen in all coated samples that were reacted in vitro. Both metallic and ceramic substrates coated in this manner failed to show significantly improved coatings over those obtained with existing techniques. Implantation of the coated ceramic substrate samples in bone gave no definite bonding as seen with bulk glass; however, partial and patchy bonding was seen. Polymeric substrates in these studies showed promise of success. The coatings applied were sufficient to mask the underlying reactive test surface and tissue adhesion of collagen to bioglass was seen. Hydrophilic, hydrophobic, charged, and uncharged polymeric surfaces were successfully coated.

  1. Cholesterol biosensor based on rf sputtered zinc oxide nanoporous thin film

    SciTech Connect

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

    2007-08-06

    Cholesterol oxidase (ChOx) has been immobilized onto zinc oxide (ZnO) nanoporous thin films grown on gold surface. A preferred c-axis oriented ZnO thin film with porous surface morphology has been fabricated by rf sputtering under high pressure. Optical studies and cyclic voltammetric measurements show that the ChOx/ZnO/Au bioelectrode is sensitive to the detection of cholesterol in 25-400 mg/dl range. A relatively low value of enzyme's kinetic parameter (Michaelis-Menten constant) {approx}2.1 mM indicates enhanced enzyme affinity of ChOx to cholesterol. The observed results show promising application of nanoporous ZnO thin film for biosensing application without any functionalization.

  2. Synthesis of nano-dimensional ZnO and Ga doped ZnO thin films by vapor phase transport and study as transparent conducting oxide.

    PubMed

    Ghosh, S; Saurav, M; Pandey, B; Srivastava, P

    2008-05-01

    We report synthesis of polycrystalline ZnO and Ga doped ZnO (ZnO:Ga) thin films (approximately 80 nm) on Si and quartz substrates in a non-vacuum muffle furnace, a simple and cost-effective route, without any catalyst/reactive carrier gases, at relatively low processing temperature of 550 degrees C. The crystalline phases of the films are identified by grazing angle X-ray diffraction (GAXRD). The growth of ZnO films is examined with scanning electron microscope (SEM) as a function of deposition time. An optical transmission of approximately 90% is observed for pure ZnO film having a resistivity of approximately 2.1 Omega-cm as measured by van der Pauw technique. Doping with Ga results in single phase ZnO:Ga films, retaining an optical transmission of about 80% and three orders of magnitude decrease in resistivity as compared to pure ZnO film. PMID:18572702

  3. Characterization of Gold-Sputtered Zinc Oxide Nanorods—a Potential Hybrid Material

    NASA Astrophysics Data System (ADS)

    Perumal, Veeradasan; Hashim, Uda; Gopinath, Subash C. B.; Rajintra Prasad, Haarindraprasad; Wei-Wen, Liu; Balakrishnan, S. R.; Vijayakumar, Thivina; Rahim, Ruslinda Abdul

    2016-01-01

    Generation of hybrid nanostructures has been attested as a promising approach to develop high-performance sensing substrates. Herein, hybrid zinc oxide (ZnO) nanorod dopants with different gold (Au) thicknesses were grown on silicon wafer and studied for their impact on physical, optical and electrical characteristics. Structural patterns displayed that ZnO crystal lattice is in preferred c-axis orientation and proved the higher purities. Observations under field emission scanning electron microscopy revealed the coverage of ZnO nanorods by Au-spots having diameters in the average ranges of 5-10 nm, as determined under transmission electron microscopy. Impedance spectroscopic analysis of Au-sputtered ZnO nanorods was carried out in the frequency range of 1 to 100 MHz with applied AC amplitude of 1 V RMS. The obtained results showed significant changes in the electrical properties (conductance and dielectric constant) with nanostructures. A clear demonstration with 30-nm thickness of Au-sputtering was apparent to be ideal for downstream applications, due to the lowest variation in resistance value of grain boundary, which has dynamic and superior characteristics.

  4. Influence of oxygen on characteristics of Zn(O,S) thin films deposited by RF magnetron sputtering

    SciTech Connect

    Choi, Ji Hyun; Garay, Adrian Adalberto; Hwang, Su Min; Chung, Chee Won

    2015-07-15

    Zn(O,S) thin films were successfully deposited by reactive sputtering using Ar and O{sub 2} gas mixtures at 473 K. X-ray diffraction patterns revealed that the well crystallized Zn(O,S) films were deposited with increasing oxygen concentration in O{sub 2}/Ar, resulting in a shift of the Zn peak of 28.5° to a higher angle, closer to the ZnO peak of 34.4°. Zn(O,S) films were composed of grains agglomerated from small particles, which grew gradually with increasing oxygen concentration. The depth profiles and energy dispersive spectroscopy results of the films indicated that the O/(O+S) ratio increased from 0.04 to 0.81, and all Zn(O,S) films were Zn rich with uniform concentrations of each component. X-ray photoelectron spectroscopy revealed that, as the oxygen concentration increased to 2%, the ZnS films were transformed to Zn(O,S) films via substitution of oxygen for sulfur.

  5. Ferromagnetism in Tb doped ZnO nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Zou, W. Q.; Ge, C. N.; Venkataiah, G.; Su, H. L.; Hsu, H. S.; Huang, J. C. A.; Liu, X. C.; Zhang, F. M.; Du, Y. W.

    2012-06-01

    Nanocrystalline Tb-doped ZnO films have been prepared by ion-beam sputtering technique. Magnetic characterization showed that the films are ferromagnetic with Curie temperature (TC) higher than room temperature. By further treated with a rapid thermal annealing process, both the grain size and the carrier concentration of the films increase, while the saturation magnetization of the films decreases. This magnetic behavior can be hardly explained by either bound magnetic polaron model or free carrier mediation model, thus suggests that the grain boundaries play a key role for the origin of ferromagnetism in these films.

  6. Synthesis of nanocrystalline material by sputtering and laser ablation at low temperatures

    NASA Astrophysics Data System (ADS)

    Ayyub, P.; Chandra, R.; Taneja, P.; Sharma, A. K.; Pinto, R.

    Physical vapor deposition techniques such as sputtering and laser ablation - which are very commonly used in thin film technology - appear to hold much promise for the synthesis of nanocrystalline thin films as well as loosely aggregated nanoparticles. We present a systematic study of the process parameters that facilitate the growth of nanocrystalline metals and oxides. The systems studied include TiO2, ZnO, γ-Al2O3, Cu2O, Ag and Cu. The mean particle size and crystallographic orientation are influenced mainly by the sputtering power, the substrate temperature and the nature, pressure and flow rate of the sputtering gas. In general, nanocrystalline thin films were formed at or close to 300 K, while loosely adhering nanoparticles were deposited at lower temperatures.

  7. A transmission electron microscopy and X-ray photoelectron spectroscopy study of annealing induced γ-phase nucleation, clustering, and interfacial dynamics in reactively sputtered amorphous alumina thin films

    NASA Astrophysics Data System (ADS)

    Kumar, A. K. Nanda; Prasanna, S.; Subramanian, B.; Jayakumar, S.; Rao, G. Mohan

    2015-03-01

    Pure α-Al2O3 exhibits a very high degree of thermodynamical stability among all metal oxides and forms an inert oxide scale in a range of structural alloys at high temperatures. We report that amorphous Al2O3 thin films sputter deposited over crystalline Si instead show a surprisingly active interface. On annealing, crystallization begins with nuclei of a phase closely resembling γ-Alumina forming almost randomly in an amorphous matrix, and with increasing frequency near the substrate/film interface. This nucleation is marked by the signature appearance of sharp (400) and (440) reflections and the formation of a diffuse diffraction halo with an outer maximal radius of ≈0.23 nm enveloping the direct beam. The microstructure then evolves by a cluster-coalescence growth mechanism suggestive of swift nucleation and sluggish diffusional kinetics, while locally the Al ions redistribute slowly from chemisorbed and tetrahedral sites to higher anion coordinated sites. Chemical state plots constructed from XPS data and simple calculations of the diffraction patterns from hypothetically distorted lattices suggest that the true origins of the diffuse diffraction halo are probably related to a complex change in the electronic structure spurred by the a-γ transformation rather than pure structural disorder. Concurrent to crystallization within the film, a substantially thick interfacial reaction zone also builds up at the film/substrate interface with the excess Al acting as a cationic source.

  8. Wurtzite structure Sc{sub 1-x}Al{sub x}N solid solution films grown by reactive magnetron sputter epitaxy: Structural characterization and first-principles calculations

    SciTech Connect

    Hoeglund, Carina; Birch, Jens; Bareno, Javier; Persson, Per O. A.; Wingqvist, Gunilla; Zukauskaite, Agne; Hultman, Lars; Alling, Bjoern; Czigany, Zsolt

    2010-06-15

    AlN(0001) was alloyed with ScN with molar fractions up to {approx}22%, while retaining a single-crystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al{sub 2}O{sub 3}(0001) and MgO(111) substrates. Films with ScN contents between 23% and {approx}50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt structure Sc{sub 1-x}Al{sub x}N(111) films. The experimental results are analyzed with ion beam analysis, x-ray diffraction, and transmission electron microscopy, together with ab initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.

  9. A transmission electron microscopy and X-ray photoelectron spectroscopy study of annealing induced γ-phase nucleation, clustering, and interfacial dynamics in reactively sputtered amorphous alumina thin films

    SciTech Connect

    Kumar, A. K. Nanda Subramanian, B.; Prasanna, S.; Jayakumar, S.; Rao, G. Mohan

    2015-03-28

    Pure α-Al{sub 2}O{sub 3} exhibits a very high degree of thermodynamical stability among all metal oxides and forms an inert oxide scale in a range of structural alloys at high temperatures. We report that amorphous Al{sub 2}O{sub 3} thin films sputter deposited over crystalline Si instead show a surprisingly active interface. On annealing, crystallization begins with nuclei of a phase closely resembling γ-Alumina forming almost randomly in an amorphous matrix, and with increasing frequency near the substrate/film interface. This nucleation is marked by the signature appearance of sharp (400) and (440) reflections and the formation of a diffuse diffraction halo with an outer maximal radius of ≈0.23 nm enveloping the direct beam. The microstructure then evolves by a cluster-coalescence growth mechanism suggestive of swift nucleation and sluggish diffusional kinetics, while locally the Al ions redistribute slowly from chemisorbed and tetrahedral sites to higher anion coordinated sites. Chemical state plots constructed from XPS data and simple calculations of the diffraction patterns from hypothetically distorted lattices suggest that the true origins of the diffuse diffraction halo are probably related to a complex change in the electronic structure spurred by the a-γ transformation rather than pure structural disorder. Concurrent to crystallization within the film, a substantially thick interfacial reaction zone also builds up at the film/substrate interface with the excess Al acting as a cationic source.

  10. Growth of Single- and Bilayer ZnO on Au(111) and Interaction with Copper

    SciTech Connect

    Deng, Xingyi; Yao, Kun; Sun, Keju; Li, Wei-Xue; Lee, Junseok; Matranga, Christopher

    2013-05-02

    The stoichiometric single- and bi-layer ZnO(0001) have been prepared by reactive deposition of Zn on Au(111) and studied in detail with X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Both single- and bi-layer ZnO(0001) adopt a planar, graphite-like structure similar to freestanding ZnO(0001) due to the weak van der Waals interactions dominating their adhesion with the Au(111) substrate. At higher temperature, the single-layer ZnO(0001) converts gradually to bi-layer ZnO(0001) due to the twice stronger interaction between two ZnO layers than the interfacial adhesion of ZnO with Au substrate. It is found that Cu atoms on the surface of bi-layer ZnO(0001) are mobile with a diffusion barrier of 0.31 eV, and likely to agglomerate and form nanosized particles at low coverages; while Cu atoms tend to penetrate a single layer of ZnO(0001) with a barrier of 0.10 eV, resulting in a Cu free surface.

  11. Effects of Au on the Growth of ZnO Nanostructures on Si by MOCVD

    NASA Astrophysics Data System (ADS)

    Cong, Chen; Fan, Lu Yang; Ping, He Hai; Wei, Wu Ke; Zhen, Ye Zhi

    2013-08-01

    The effects of Au on the growth of ZnO nanostructures on Si by metal organic chemical vapor deposition (MOCVD) at a relatively low temperature (450°C) were investigated. The experimental results showed that Au nanoparticles played a critical role during the growth of the ZnO nanostructures and affected their morphology and optical properties. It was found that Au nanoparticles particularly affected the nucleation of ZnO nanostructures during the growth process and the Au-assisted growth mechanism of ZnO nanostructures should be ascribed to the vapor-solid (VS) mechanism. The formation of a nanoneedle may be attributed to a more reactive interface between Au and ZnO, which leads to more zinc gaseous species absorbed near the interface. Different nucleation sites on ZnO nuclei resulted in the disorder of ZnO nanoneedles. Moreover, the crystalline quality of nano-ZnO was improved due to the presence of Au, according to the smaller full width at half maximum (FWHM) of the low-temperature exciton emission. We confirmed that ZnO nanoneedles showed better crystalline quality than ZnO nanorods through the HRTEM images and the SAED patterns. The reason for the improvement of the crystalline quality of nano-ZnO may be due to the less lattice mismatch.

  12. Mimicry of sputtered i-ZnO thin films using chemical bath deposition for solution-processed solar cells.

    PubMed

    Della Gaspera, Enrico; van Embden, Joel; Chesman, Anthony S R; Duffy, Noel W; Jasieniak, Jacek J

    2014-12-24

    Solution processing provides a versatile and inexpensive means to prepare functional materials with specifically designed properties. The current challenge is to mimic the structural, optical, and/or chemical properties of thin films fabricated by vacuum-based techniques using solution-based approaches. In this work we focus on ZnO to show that thin films grown using a simple, aqueous-based, chemical bath deposition (CBD) method can mimic the properties of sputtered coatings, provided that the kinetic and thermodynamic reaction parameters are carefully tuned. The role of these parameters toward growing highly oriented and dense ZnO thin films is fully elucidated through detailed microscopic and spectroscopic investigations. The prepared samples exhibit bulk-like optical properties, are intrinsic in their electronic characteristics, and possess negligible organic contaminants, especially when compared to ZnO layers deposited by sol-gel or from nanocrystal inks. The efficacy of our CBD-grown ZnO thin films is demonstrated through the effective replacement of sputtered ZnO buffer layers within high efficiency solution processed Cu2ZnSnS4xSe4(1-x) solar cells. PMID:25506738

  13. Comparative research on the optical properties of three surface patterning ZnO ordered arrays

    NASA Astrophysics Data System (ADS)

    Hou, Kai; Zhu, Ya-Bin; Qiao, Lu

    2015-12-01

    We fabricate three surface patterning zinc oxide (ZnO) ordered arrays on glass substrates by using nanosphere lithography technique and dc magnetron sputtering technique. The crescent, tube and honeycomb surface morphologies of the samples are observed by scanning electron microscopy. The transmittance, fluorescence and confocal Raman spectra of the sample are measured. Obviously, when the angle between the plume and the substrate is 90°, the honeycomb arrays have a better transmission. Additionally, the PL intensity of honeycomb arrays is superior. With the increasing of the angle between the substrate and the sputtering plume, the fluorescence peak shows blue shift. The Raman peak located at 438 cm- 1 belongs to ZnO E2 (high) mode, which corresponds to the characteristic band of the hexagonal wurtzite phase. The tube arrays have the best Raman spectrum intensity.

  14. ZnO thin film piezoelectric MEMS vibration energy harvesters with two piezoelectric elements for higher output performance.

    PubMed

    Wang, Peihong; Du, Hejun

    2015-07-01

    Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s(2). By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration.

  15. ZnO thin film piezoelectric MEMS vibration energy harvesters with two piezoelectric elements for higher output performance.

    PubMed

    Wang, Peihong; Du, Hejun

    2015-07-01

    Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s(2). By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration. PMID:26233403

  16. Closed field magnetron sputtering: new generation sputtering process for optical coatings

    NASA Astrophysics Data System (ADS)

    Gibson, D. R.; Brinkley, I.; Waddell, E. M.; Walls, J. M.

    2008-09-01

    "Closed field" magnetron (CFM) sputtering offers a flexible and high throughput deposition process for optical coatings and thin films. CFM sputtering uses two or more different metal targets to deposit multilayers comprising a wide range of dielectrics, metals and conductive oxides. Moreover, CFM provides a room temperature deposition process with high ion current density, low bias voltage and reactive oxidation in the entire volume around the rotating substrate drum carrier, thereby producing films over a large surface area at high deposition rate with excellent and reproducible optical properties. Machines based on the Closed Field are scaleable to meet a range of batch and in-line size requirements. Typically, thin film thickness control to <+/-1% is accomplished simply using time, although optical monitoring can be used for more demanding applications. Fine layer thickness control and deposition of graded index layers is also assisted with a specially designed rotating shutter mechanism. This paper presents data on optical properties for CFM deposited optical coatings, including anti-reflection, thermal control filters, graded coatings, narrowband filters as well as conductive transparent oxides such as indium tin oxide and carbide films. Benefits of the CFM sputter process are described.

  17. Growth of crystalline ZnO films on the nitridated (0001) sapphire surface

    SciTech Connect

    Butashin, A. V.; Kanevsky, V. M.; Muslimov, A. E. Prosekov, P. A.; Kondratev, O. A.; Blagov, A. E.; Vasil’ev, A. L.; Rakova, E. V.; Babaev, V. A.; Ismailov, A. M.; Vovk, E. A.; Nizhankovsky, S. V.

    2015-07-15

    The surface morphology and structure of (0001) sapphire substrates subjected to thermochemical nitridation in a mixture of N{sub 2}, CO, and H{sub 2} gases are investigated by electron and probe microscopy and X-ray and electron diffraction. It is shown that an aluminum nitride layer is formed on the substrate surface and heteroepitaxial ZnO films deposited onto such substrates by magnetron sputtering have a higher quality when compared with films grown on sapphire.

  18. Low-Energy Sputtering Research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1999-01-01

    An experimental study is described to measure low-energy (less than 600 eV) sputtering yields of molybdenum with xenon ions using Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectroscopy (SNMS). An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 (micro)A/sq cm. For RBS measurements, the sputtered material was collected on a thin aluminum strip which was mounted on a semi-circular collector plate. The target was bombarded with 200 and 500 eV xenon ions at normal incidence. The differential sputtering yields were measured using the RBS method with 1 MeV helium ions. The differential yields were fitted with a cosine fitting function and integrated with respect to the solid angle to provide the total sputtering yields. The sputtering yields obtained using the RBS method are in reasonable agreement with those measured by other researchers using different techniques. For the SNMS measurements, 150 to 600 eV xenon ions were used at 50deg angle of incidence. The SNMS spectra were converted to sputtering yields for perpendicular incidence by normalizing SNMS spectral data at 500 eV with the yield measured by Rutherford backscattering spectrometry. Sputtering yields as well as the shape of the yield-energy curve obtained in this manner are in reasonable agreement with those measured by other researchers using different techniques. Sputtering yields calculated by using two semi-spherical formulations agree reasonably well with measured data. The isotopic composition of secondary ions were measured by bombarding copper with xenon ions at energies ranging from 100 eV to 1.5 keV. The secondary ion flux was found to be enriched in heavy isotopes at low incident ion energies. The heavy isotope enrichment was observed to decrease with increasing impact energy. Beyond 700 eV, light isotopes were sputtered preferentially with the enrichment remaining nearly constant.

  19. Effect of annealing in hydrogen atmosphere on ZnO films for field emission display

    NASA Astrophysics Data System (ADS)

    Zulkifli, Zurita; Sharma, Subash; Shinde, Sachin; Kalita, Golap; Tanemura, M.

    2015-11-01

    Surface morphology, crystallinity, conductivity and optical transmittance of ZnO films can be modified by annealing process. Hydrogen is one of the popular annealing gases as well as nitrogen, argon, oxygen and air which are commonly used for thin film cleaning or the removal of native oxide. In general, annealing is done at high temperatures (> 600degC) to improve the film properties. From a view point of environment, however, lower annealing temperature is preferable. In this work, low annealing process was challenged to understand the effect of annealing temperature on properties of ZnO thin films and nanostructured film grown on glass substrates for transparent field emission device applications. The annealing temperature employed was 100, 200 and 450°C at 100 sccm hydrogen flow rate. ZnO thin films were deposited by RF magnetron sputtering. The ZnO thin films were characterized by X-ray diffraction analysis (XRD), Atomic Force Microscopy (AFM), UV-VIS and Raman spectroscopy. The sheet resistances reduced about 15 kohm/sq at low annealing temperature. By contrast, the optical transmittance did not show any significant changes after annealing. The FE current density increased after the ZnO nanostructures film was annealed in 100°C. The results obtained could motivate a surface treatment for flexible ZnO thin film since the substrate is always suffered by heat.

  20. Achieving highly-enhanced UV photoluminescence and its origin in ZnO nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Thapa, Dinesh; Huso, Jesse; Morrison, John L.; Corolewski, Caleb D.; McCluskey, Matthew D.; Bergman, Leah

    2016-08-01

    ZnO is an efficient luminescent material in the UV-range ∼3.4 eV with a wide range of applications in optical technologies. Sputtering is a cost-effective and relatively straightforward growth technique for ZnO films; however, most as-grown films are observed to contain intrinsic defects which can significantly diminish the desirable UV-emission. In this research the defect dynamics and optical properties of ZnO sputtered films were studied via post-growth annealing in Ar or O2 ambient, with X-ray diffraction (XRD), imaging, transmission and Urbach analysis, Raman scattering, and photoluminescence (PL). The imaging, XRD, Raman and Urbach analyses indicate significant improvement in crystal morphology and band-edge characteristics upon annealing, which is nearly independent of the annealing environment. The native defects specific to the as-grown films, which were analyzed via PL, are assigned to Zni related centers that luminesce at 2.8 eV. Their presence is attributed to the nature of the sputtering growth technique, which supports Zn-rich growth conditions. After annealing, in either environment the 2.8 eV center diminished accompanied by morphology improvement, and the desirable UV-PL significantly increased. The O2 ambient was found to introduce nominal Oi centers while the Ar ambient was found to be the ideal environment for the enhancement of the UV-light emission: an enhancement of ∼40 times was achieved. The increase in the UV-PL is attributed to the reduction of Zni-related defects, the presence of which in ZnO provides a competing route to the UV emission. Also, the effect of the annealing was to decrease the compressive stress in the films. Finally, the dominant UV-PL at the cold temperature regime is attributed to luminescent centers not associated with the usual excitons of ZnO, but rather to structural defects.

  1. Sputtering. [as deposition technique in mechanical engineering

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1976-01-01

    This paper primarily reviews the potential of using the sputtering process as a deposition technique; however, the manufacturing and sputter etching aspects are also discussed. Since sputtering is not regulated by classical thermodynamics, new multicomponent materials can be developed in any possible chemical composition. The basic mechanism for dc and rf sputtering is described. Sputter-deposition is described in terms of the unique advantageous features it offers such as versatility, momentum transfer, stoichiometry, sputter-etching, target geometry (coating complex surfaces), precise controls, flexibility, ecology, and sputtering rates. Sputtered film characteristics, such as strong adherence and coherence and film morphology, are briefly evaluated in terms of varying the sputtering parameters. Also described are some of the specific industrial areas which are turning to sputter-deposition techniques.

  2. Self-organized ZnO nanodot arrays: Effective control using SiNx interlayers and low-temperature plasmas

    NASA Astrophysics Data System (ADS)

    Huang, S. Y.; Cheng, Q. J.; Xu, S.; Wei, D. Y.; Zhou, H. P.; Long, J. D.; Levchenko, I.; Ostrikov, K.

    2012-02-01

    An advanced inductively coupled plasma (ICP)-assisted rf magnetron sputtering deposition method is developed to synthesize regular arrays of pear-shaped ZnO nanodots on a thin SiNx buffer layer pre-deposited onto a silicon substrate. It is shown that the growth of ZnO nanodots obey the cubic root-law behavior. It is also shown that the synthesized ZnO nanodots are highly-uniform, controllable by the experimental parameters, and also feature good structural and photoluminescent properties. These results suggest that this custom-designed ICP-based technique is very effective and highly-promising for the synthesis of property- and size-controllable highly-uniform ZnO nanodots suitable for next-generation light emitting diodes, energy storage, UV nanolasers, and other applications.

  3. Simultaneous ion sputter polishing and deposition

    NASA Technical Reports Server (NTRS)

    Rutledge, S.; Banks, B.; Brdar, M.

    1981-01-01

    Results of experiments to study ion beam sputter polishing in conjunction with simultaneous deposition as a mean of polishing copper surfaces are presented. Two types of simultaneous ion sputter polishing and deposition were used in these experiments. The first type utilized sputter polishing simultaneous with vapor deposition, and the second type utilized sputter polishing simultaneous with sputter deposition. The etch and deposition rates of both techniques were studied, as well as the surface morphology and surface roughness.

  4. Effect of indium low doping in ZnO based TFTs on electrical parameters and bias stress stability

    SciTech Connect

    Cheremisin, Alexander B. Kuznetsov, Sergey N.; Stefanovich, Genrikh B.

    2015-11-15

    Some applications of thin film transistors (TFTs) need the bottom-gate architecture and unpassivated channel backside. We propose a simple routine to fabricate indium doped ZnO-based TFT with satisfactory characteristics and acceptable stability against a bias stress in ambient room air. To this end, a channel layer of 15 nm in thickness was deposited on cold substrate by DC reactive magnetron co-sputtering of metal Zn-In target. It is demonstrated that the increase of In concentration in ZnO matrix up to 5% leads to negative threshold voltage (V{sub T}) shift and an increase of field effect mobility (μ) and a decrease of subthreshold swing (SS). When dopant concentration reaches the upper level of 5% the best TFT parameters are achieved such as V{sub T} = 3.6 V, μ = 15.2 cm{sup 2}/V s, SS = 0.5 V/dec. The TFTs operate in enhancement mode exhibiting high turn on/turn off current ratio more than 10{sup 6}. It is shown that the oxidative post-fabrication annealing at 250{sup o}C in pure oxygen and next ageing in dry air for several hours provide highly stable operational characteristics under negative and positive bias stresses despite open channel backside. A possible cause of this effect is discussed.

  5. Third generation biosensing matrix based on Fe-implanted ZnO thin film

    SciTech Connect

    Saha, Shibu; Gupta, Vinay; Sreenivas, K.; Tan, H. H.; Jagadish, C.

    2010-09-27

    Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 {mu}A mM{sup -1} cm{sup -2} and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.

  6. Third generation biosensing matrix based on Fe-implanted ZnO thin film

    NASA Astrophysics Data System (ADS)

    Saha, Shibu; Gupta, Vinay; Sreenivas, K.; Tan, H. H.; Jagadish, C.

    2010-09-01

    Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 μA mM-1 cm-2 and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.

  7. Epitaxial chemical deposition of ZnO nanocolumns from NaOH solutions.

    PubMed

    Peterson, Renee B; Fields, Clark L; Gregg, Brian A

    2004-06-01

    A new method of depositing expitaxial ZnO nanocolumns on sputter-coated ZnO substrates is described that utilizes supersaturated zincate species in sodium hydroxide solutions and requires no complexing agents. Uniform arrays of columns are grown reproducibly over entire substrates in 10-50 min. Columns are 50-2000 nm long and 50-100 nm wide. Strict substrate cleaning and/or preparation was not necessary with this method, in contrast to many other techniques, probably because the high pH generates a reproducible surface. The interfacial properties of the substrate are critical to lowering the activation energy for columnar growth; therefore films grow only on substrates precoated with ZnO, not on bare glass or ITO- or SnO2-coated glass. Factors affecting the column growth are elucidated, and experimental observations are correlated with crystal growth theory.

  8. Polarity enhancement in high oriented ZnO films on Si (100) substrate

    NASA Astrophysics Data System (ADS)

    Kurniawan, Robi; Nurfani, Eka; Muhammady, Shibghatullah; Sutjahja, Inge M.; Winata, Toto; Rusydi, Andrivo; Darma, Yudi

    2016-04-01

    Zinc oxide films with hexagonal crystal structures have been grown on Si substrate (100) using the DC-unbalanced magnetron sputtering at temperature of 300°C with growth time variation. The films have been characterized using X-Ray Diffraction and Fourier Transform Infrared measurement to show the crystal parameter and atomic bonding. The results show that the films have a dominant orientation in the hkl plane (002), while peak positions are shift to lower diffraction angle with addition of growth time. In addition, the bonding between Zn and O atoms (Zn-O) tend to be weaker as indicated by transmittance peak shifting to lower energy. The weakening of Zn-O bonding is due to the contribution of addition of bond length. These conditions make the films tend to have a high polarity. Further analysis of these studies will bring us to have a good undestanding to explain the ferroelectric properties of the ZnO films.

  9. Linear and nonlinear optical investigations of nano-scale Si-doped ZnO thin films: spectroscopic approach

    NASA Astrophysics Data System (ADS)

    Jilani, Asim; Abdel-wahab, M. Sh.; Zahran, H. Y.; Yahia, I. S.; Al-Ghamdi, Attieh A.

    2016-09-01

    Pure and Si-doped ZnO (SZO) thin films at different concentration of Si (1.9 and 2.4 wt%) were deposited on highly cleaned glass substrate by radio frequency (DC/RF) magnetron sputtering. The morphological and structural investigations have been performed by atomic force electron microscope (AFM) and X-ray diffraction (XRD). The X-ray photoelectron spectroscopy was employed to study the composition and the change in the chemical state of Si-doped ZnO thin films. The optical observations like transmittance, energy band gap, extinction coefficient, refractive index, dielectric loss of pure and Si-doped ZnO thin films have been calculated. The linear optical susceptibility, nonlinear refractive index, and nonlinear optical susceptibility were also studied by the spectroscopic approach rather than conventional Z-scan method. The energy gap of Si-doped ZnO thin films was found to increase as compared to pure ZnO thin films. The crystallinity of the ZnO thin films was effected by the Si doping. The O1s spectra in pure and Si-doped ZnO revealed the bound between O-2 and Zn+2 ions and reduction in the surface oxygen with the Si doping. The chemical state analysis of Si 2p showed the conversation of Si to SiOx and SiO2. The increase in the first-order linear optical susceptibility χ (1) and third-order nonlinear optical susceptibility χ (3) was observed with the Si doping. The nonlinear studies gave some details about the applications of metal oxides in nonlinear optical devices. In short, this study showed that Si doping through sputtering has effected on the structural, surface and optical properties of ZnO thin films which could be quite useful for advanced applications such as metal-oxide-based optical devices.

  10. Photoluminescence characterization of ZnO nanowires functionalization

    NASA Astrophysics Data System (ADS)

    Politi, Jane; Gioffrè, Mariano; Rea, Ilaria; De Stefano, Luca; Rendina, Ivo

    2015-05-01

    Nanostructured photoluminescent materials are optimal transducers for optical biosensors due to their capacity to convert molecular interactions in light signals without contamination or deterioration of the samples. In recent years, nanostructured biosensors with low cost and readily available properties have been developed for such applications as therapeutics, diagnostic and environmental. Zinc oxide nanowires (ZnO NWs) is material with unique properties and due to these they were widely studied in many fields as electronics, optics, and photonics. ZnO NWs can be either grown independently or deposited on solid support, such as glass, gold substrates and crystalline silicon. Vertical aligned ZnO forest on a substrate shows specific advantages in photonic device fabrication. ZnO NWs are typically synthesized by such techniques classified as vapour phase and solution phase synthesis. In particular, hydrothermal methods have received a lot of attention and have been widely used for synthesis of ZnO NWs. This technique shows more crystalline defects than others due to oxygen vacancies, so as the material shows intense photoluminescence emission under laser irradiation. ZnO NWs surface is highly hydrolysed, so it is covered by OH reactive groups, and standard biomodification chemistry can be used in order to bind bioprobes on the surface. In this work, we present our newest results on synthetic nanostructured materials characterization for optical biosensors applications. In particular, we characterize the ZnO NWs structure grown on crystalline silicon by SEM images and the biomodification by photoluminesce technique, fluorescence microscopy, water contact angle and FT-IR measurements.

  11. Antifungal activity of ZnO nanoparticles—the role of ROS mediated cell injury

    NASA Astrophysics Data System (ADS)

    Lipovsky, Anat; Nitzan, Yeshayahu; Gedanken, Aharon; Lubart, Rachel

    2011-03-01

    Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml - 1 ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.

  12. Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury.

    PubMed

    Lipovsky, Anat; Nitzan, Yeshayahu; Gedanken, Aharon; Lubart, Rachel

    2011-03-11

    Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds. PMID:21289395

  13. Assessment of phytotoxicity of ZnO NPs on a medicinal plant, Fagopyrum esculentum.

    PubMed

    Lee, Sooyeon; Kim, Sunghyun; Kim, Saeyeon; Lee, Insook

    2013-02-01

    Fagopyrum esculentum commonly named as buckwheat plant is pseudocereal food crops and healthy herbs but is not known as a bioindicator of environmental condition. In the present study, the effects of ZnO nanoparticles (NPs) and microparticles (MPs) on plant growth, bioaccumulation, and antioxidative enzyme activity in buckwheat were estimated under hydroponic culture. The significant biomass reduction at concentrations of 10-2,000 mg/L was 7.7-26.4 % for the ZnO NP and 11.4-23.5 % for the ZnO MP treatment, (p < 0.05). ZnO NPs were observed in root cells and root cell surface by scanning electron microscopy and transmission electron microscopy analysis. Zn bioaccumulation in plant increased with increasing treatment concentrations. The upward translocation (translocation factor <0.2) of Zn in plant was higher with the ZnO NP treatment than that with the ZnO MP treatment. Additionally, reactive oxygen species generation by ZnO NPs was estimated as the reduced glutathione level and catalase activity, which would be a predictive biomarker of nanotoxicity. The results are the first study to evaluate the phytotoxicity of ZnO NPs to medicinal plant. F. esculentum can be as a good indicator of plant species in NP-polluted environment.

  14. Impact of preparation condition of ZnO electron transport layer on performance of hybrid organic-inorganic light-emitting diodes

    SciTech Connect

    Huang, Chun-Yuan; Yang, Chih-Chiang; Yu, Hsin-Chieh; Chen, Ying-Chih

    2014-02-28

    In this article, we have demonstrated the hybrid polymer light-emitting diodes (PLEDs) with a sol-gel derived or rf-sputtered ZnO electron transport layer (ETL). For the ZnO films prepared under different conditions, low annealing temperature (300 °C) leads to the film amorphous while the polycrystalline films is readily achieved by sputtering. Though the surface roughness can be improved by thermal annealing at 400 °C for sputtered films, the release of compressive stress after treatment has shrunk the optical band gap from 3.282 to 3.268 eV. As the ETL in PLEDs, the reduced band gap could increase potential barrier for electron injection and decrease the hole blocking capability. In our cases, luminance larger than 7000 cd/m{sup 2} can be obtained in device with pristine sputtered ZnO ETL. It is concluded that crystalline structure of ZnO films is important to facilitate the balance of carrier mobility to obtain high luminance and high efficiency devices.

  15. Fabrication and characterization of ZnO nanowires by wet oxidation of Zn thin film deposited on Teflon substrate

    NASA Astrophysics Data System (ADS)

    Farhat, O. F.; Halim, M. M.; Abdullah, M. J.; Ali, M. K. M.; Ahmed, Naser M.; Bououdina, M.

    2015-10-01

    In this study, ZnO nanowires (NWs) were successfully grown for the first time on to Teflon substrate by a wet oxidation of a Zn thin film coated by RF sputtering technique. The sputtered Zn thin film was oxidized at 100 °C for 5 h under water-vapour using a horizontal furnace. This oxidation process transformed Zn thin film into ZnO with wire-like nanostructure. XRD analysis confirms the formation of single nanocrystalline ZnO phase having a low compressive strain. FESEM observations reveal high density of ZnO NWs with diameter ranging from 34 to 52 nm and length about 2.231 μm, which are well distributed in different direction. A flexible ZnO NWs-based metal-semiconductor-metal UV photodetector was fabricated. Photo-response and sensitivity measurements under low power illumination (375 nm, 1.5 mW/cm2) showed a high sensitivity of 2050%, which can be considered a relatively fast response and baseline recovery for UV detection.

  16. Effect of self-organization, defects, impurities, and autocatalytic processes on the parameters of ZnO films and nanorods

    SciTech Connect

    Mezdrogina, M. M. Eremenko, M. V.; Levitskii, V. S.; Petrov, V. N.; Terukov, E. I.; Kaidashev, E. M.; Langusov, N. V.

    2015-11-15

    The effects of the parameters of ZnO-film deposition onto different substrates using the method of ac magnetron sputtering in a gas mixture of argon and oxygen hare studied. The phenomenon of self-organization is observed, which leads to invariability of the surface morphology of the ZnO films upon a variation in the substrate materials and deposition parameters. The parameters of the macro- and micro-photoluminescence spectra of the films differ insignificantly from the parameters of the photoluminescence spectra of bulk ZnO crystals obtained by the method of hydrothermal growth. The presence of intense emission with a narrow full-width at half-maximum (FWHM) in different regions of the spectrum allows ZnO films obtained by magnetron sputtering doped with rare-earth metal impurities (REIs) to be considered as a promising material for the creation of optoelectronic devices working in a broad spectral range. The possibility of the implementation of magnetic ordering upon legierung with REIs significantly broadens the functional possibilities of ZnO films. The parameters of the photoluminescence spectra of ZnO nanorods are determined by their geometrical parameters and by the concentration and type of the impurities introduced.

  17. Effect of post-annealing temperature on structure and optical properties of Zn1- x Cd x O thin films synthesized by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sui, Yingrui; Song, Yanping; Yue, Yonggao; Xiao, Li; Wu, Yanjie; Lv, Shiquan; Liu, Xiaoyan; Yao, Bin; Yang, Jinghai

    2016-08-01

    The Zn1- x Cd x O ( x = 0.5) thin film was grown on quartz by the direct current reactive magnetron sputtering and post-annealing techniques. The influence of annealing temperature ( T a) on the structure and optical properties of Zn1- x Cd x O thin film was investigated by using X-ray diffraction (XRD), photoluminescence and optical absorbance measurements. The XRD results indicate that the as-grown Zn1- x Cd x O thin film is of highly (002)-preferred orientation and possessing the hexagonal wurtzite structure of pure ZnO, as the T a increases up from 300 to 600 °C, the phase segregation as cubic CdO was observed. The detailed microstructures of the Zn1- x Cd x O thin film were investigated by transmission electron microscopy. Moreover, with the increase of T a, the optical band gap of the Zn1- x Cd x O thin films increased from 2.08 to 3.14 eV. Correspondingly, the near-band-edge photoluminescence was tuned in a wide visible region from ~588 to 403 nm.

  18. In situ analyses on negative ions in the indium-gallium-zinc oxide sputtering process

    SciTech Connect

    Jia, Junjun; Torigoshi, Yoshifumi; Shigesato, Yuzo

    2013-07-01

    The origin of negative ions in the dc magnetron sputtering process using a ceramic indium-gallium-zinc oxide target has been investigated by in situ analyses. The observed negative ions are mainly O{sup -} with energies corresponding to the target voltage, which originates from the target and barely from the reactive gas (O{sub 2}). Dissociation of ZnO{sup -}, GaO{sup -}, ZnO{sub 2}{sup -}, and GaO{sub 2}{sup -} radicals also contributes to the total negative ion flux. Furthermore, we find that some sputtering parameters, such as the type of sputtering gas (Ar or Kr), sputtering power, total gas pressure, and magnetic field strength at the target surface, can be used to control the energy distribution of the O{sup -} ion flux.

  19. RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

    DOEpatents

    Jeffery, F.R.; Shanks, H.R.

    1980-08-26

    A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  20. Facility for combined in situ magnetron sputtering and soft x-ray magnetic circular dichroism

    SciTech Connect

    Telling, N. D.; Laan, G. van der; Georgieva, M. T.; Farley, N. R. S.

    2006-07-15

    An ultrahigh vacuum chamber that enables the in situ growth of thin films and multilayers by magnetron sputtering techniques is described. Following film preparation, x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements are performed by utilizing an in vacuum electromagnet. XMCD measurements on sputtered thin films of Fe and Co yield spin and orbital moments that are consistent with those obtained previously on films measured in transmission geometry and grown in situ by evaporation methods. Thin films of FeN prepared by reactive sputtering are also examined and reveal an apparent enhancement in the orbital moment for low N content samples. The advantages of producing samples for in situ XAS and XMCD studies by magnetron sputtering are discussed.

  1. Optical, Electrical, and Adhesive Properties of ZnO Thin Films.

    PubMed

    Chen, Yuan-Tsung

    2016-01-01

    ZnO films were sputtered onto glass substrates to thicknesses from 100 A to 500 A under the following conditions; (a) as-deposited films were maintained at room temperature (RT); (b) films were post-annealed at 150 °C for 1 h, and (c) films were post-annealed at 250 °C for 1 h. X-ray diffraction (XRD) result thus obtained demonstrate that ZnO has a wurtzite structure with a (002) texture diffraction peak with a 2θ of 34° range. The intensity of the ZnO (002) peak increased with film thickness and upon post-annealing. As the ZnO thin film thickness increased and post-annealing was carried out, the grains became larger. A spectral analyzer was utilized to measure transmittance for various thicknesses. Post-annealing treatment promoted the growth of grains, yielding a large mean grain size and, therefore, low transmittance. The as-deposited ZnO thin film with a thickness of 100 Å had a transmittance maximum of approximately 88% and a reflectance minimum of around 12%. Additionally, the four-point probe measurements revealed that p decreased as the ZnO thickness increased and with post-annealing treatment because grain boundaries and the surface of thin films scatter electrons, so thinner films have a greater resistance. ZnO with a thickness of 500 Å that underwent post-annealing treatment at 250 °C had a minimum resistivity of 7.6 x 10⁻³ Ω · cm. Adhesion critically influences the surface energy of films. The surface energy of as-deposited ZnO films was higher than that following post-annealing treatments, revealing that the adhesion of the as-deposited ZnO films was stronger than that following post-annealing treatment because the degree of crystallinity was lower. Accordingly, the thickness and crystallinity of ZnO importantly affects its optical, electrical, and adhesive characteristics. Finally, thinner as-deposited ZnO films exhibited better optical and adhesive properties. PMID:27398504

  2. Fabrication and characterization of lithium manganese nickel oxide sputtered thin film cathodes for lithium-ion batteries

    SciTech Connect

    Baggetto, Loic; Unocic, Raymond R; Dudney, Nancy J; Veith, Gabriel M

    2012-01-01

    Li-rich and stoichiometric Li1Mn1.5Ni0.5O4 (LMNO) cathode films have been prepared by magnetron sputtering. Sputtering from a Li stoichiometric target yields Li-rich films composed of spinel, layered and monoclinic phases. Films obtained from a Li deficient target are mostly made of a spinel phase and little layered material. The resulting cathode thin films have good capacity retention and very high rate capability. The reaction mechanism has been investigated by XRD and HRTEM and evidences the reversible formation of a spinel phase, as is also found for the powder samples. The film geometry enables to understand the effect of coatings (ZnO or LiPON). Coating high voltage cathodes reduces the coulombic losses but at the price of rate performance. Nonetheless, these coated sputtered electrode thin films offer a higher rate capability than other LMNO thin films obtained by other physical vapor deposition techniques.

  3. Sputtered silicon nitride coatings for wear protection

    NASA Technical Reports Server (NTRS)

    Grill, A.; Aron, P. R.

    1982-01-01

    Silicon nitride films were deposited by RF sputtering on 304 stainless steel substrates in a planar RF sputtering apparatus. The sputtering was performed from a Si3N4 target in a sputtering atmosphere of argon and nitrogen. The rate of deposition, the composition of the coatings, the surface microhardness and the adhesion of the coatings to the substrates were investigated as a function of the process parameters, such as: substrate target distance, fraction nitrogen in the sputtering atmosphere and sputtering pressure. Silicon rich coating was obtained for fraction nitrogen below 0.2. The rate of deposition decreases continuously with increasing fraction nitrogen and decreasing sputtering pressure. It was found that the adherence of the coatings improves with decreasing sputtering pressure, almost independently of their composition.

  4. Ion beam sputtering of fluoropolymers

    NASA Technical Reports Server (NTRS)

    Sovey, J. S.

    1978-01-01

    Etching and deposition of fluoropolymers are of considerable industrial interest for applications dealing with adhesion, chemical inertness, hydrophobicity, and dielectric properties. This paper describes ion beam sputter processing rates as well as pertinent characteristics of etched targets and films. An argon ion beam source was used to sputter etch and deposit the fluoropolymers PTFE, FEP, and CTFE. Ion beam energy, current density, and target temperature were varied to examine effects on etch and deposition rates. The ion etched fluoropolymers yield cone or spire-like surface structures which vary depending upon the type of polymer, ion beam power density, etch time, and target temperature. Also presented are sputter target and film characteristics which were documented by spectral transmittance measurements, X-ray diffraction, ESCA, and SEM photomicrographs.

  5. Some properties of RF sputtered hafnium nitride coatings

    NASA Technical Reports Server (NTRS)

    Aron, P. R.; Grill, A.

    1982-01-01

    Hafnium nitride coatings were deposited by reactive RF sputtering from a hafnium target in nitrogen and argon gas mixtures. The rate of deposition, composition, electrical resistivity and complex index of refraction were investigated as a function of target substrate distance and the fraction nitrogen, (fN2) in the sputtering atmosphere. The relative composition of the coatings is independent on fN2 for values above 0.1. The electric resistivity of the hafnium nitride films changes over 8 orders of magnitude when fN2 changes from 0.10 to 0.85. The index of refraction is almost constant at 2.8(1-0.3i) up to fN2 = 0.40 then decreases to 2.1(1 - 0.01i) for higher values of fN2.

  6. Fabrication of thick structures by sputtering

    NASA Technical Reports Server (NTRS)

    Kazaroff, J. M.; Mcclanahan, E. D.; Busch, R.; Moss, R. W.

    1974-01-01

    Deposit, 5500-gram of Cu-0.15 wt % Zr alloy, sputtered onto copper cylinder to average thickness of 12.29 mm. Structure was achieved with high-rate sputter deposition for about 100 hours total sputtering time. Material had twice the strength of unsputtered material at temperatures to 723 K and equivalent strength at nearly 873 K.

  7. Enhanced the photocatalytic activity of Ni-doped ZnO thin films: Morphological, optical and XPS analysis

    NASA Astrophysics Data System (ADS)

    Abdel-wahab, M. Sh.; Jilani, Asim; Yahia, I. S.; Al-Ghamdi, Attieh A.

    2016-06-01

    Pure and Ni-doped ZnO thin films with different concentration of Ni (3.5 wt%, 5 wt%, 7 wt%) were prepared by DC/RF magnetron sputtering technique. The X-rays diffraction pattern showed the polycrystalline nature of pure and Ni-doped ZnO thin films. The surface morphology of pure and Ni doped ZnO thin films were investigated through atomic force microscope, which indicated the increase in the grain dimension and surface roughness with increasing the Ni doping. The UV-Visible transmission spectra showed the decrease in the transmittance of doped ZnO thin films with the incorporation of Ni dopants. The surface and chemical state analysis of pure and Ni doped ZnO thin films were investigated by X-rays photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by an aqueous solution of methyl green dye. The tungsten lamp of 500 W was used as a source of visible light for photocatalytic study. The degradation results showed that the Ni-doped ZnO thin films exhibit highly enhanced photocatalytic activity as compared to the pure ZnO thin films. The enhanced photocatalytic activities of Ni-doped ZnO thin films were attributed to the enhanced surface area (surface defects), surface roughness and decreasing the band gap of Ni-doped ZnO thin films. Our work supports the applications of thin film metal oxides in waste water treatment.

  8. ZnO nanoparticle tracking from uptake to genotoxic damage in human colon carcinoma cells.

    PubMed

    Condello, Maria; De Berardis, Barbara; Ammendolia, Maria Grazia; Barone, Flavia; Condello, Giancarlo; Degan, Paolo; Meschini, Stefania

    2016-09-01

    Zinc Oxide (ZnO) nanoparticles are widely used both in the industry and in biomedical applications for their chemical and physical nanomaterial properties. It is therefore essential to go in depth into the cytotoxicity mechanisms and interactions between nanomaterials and cells. The aim of this work was to evaluate the dissolution of ZnO nanoparticles and their uptake, from a few minutes after treatments up to 24h. ZnO nanoparticles routes of entry into the human colon carcinoma cells (LoVo) were followed at different times by a thorough ultrastructural investigation and semiquantitative analysis. The intracellular release of Zn(2+) ions by Zinquin fluorescent dye, and phosphorylated histone H2AX (γ-H2AX) expression were evaluated. The genotoxic potential of ZnO nanoparticles was also investigated by determining the levels of 8-hydroxyl-2'-deoxyguanosine (8-oxodG). The experimental data show that ZnO nanoparticles entered LoVo cells by either passive diffusion or endocytosis or both, depending on the agglomeration state of the nanomaterial. ZnO nanoparticles coming into contact with acid pH of lysosomes altered organelles structure, resulting in the release of Zn(2+) ions. The simultaneous presence of ZnO nanoparticles and Zn(2+) ions in the LoVo cells determined the formation of reactive oxygen species at the mitochondrial and nuclear level, inducing severe DNA damage. PMID:27317967

  9. Different properties of aluminum doped zinc oxide nanostructured thin films prepared by radio frequency magnetron sputtering

    SciTech Connect

    Bidmeshkipour, Samina Shahtahmasebi, Nasser

    2013-06-15

    Aluminium doped zinc oxide (AZO) nanostructured thin films are prepared by radio frequency magnetron sputtering on glass substrate using specifically designed ZnO target containing different amount of Al{sub 2}O{sub 3} powder as the Al doping source. The optical properties of the aluminium doped zinc oxide films are investigated. The topography of the deposited films were investigated by Atomic Force Microscopy. Variation of the refractive index by annealing temperature are considered and it is seen that the refractive index increases by increasing the annealing temperature.

  10. ZnO nanowire lasers.

    PubMed

    Vanmaekelbergh, Daniël; van Vugt, Lambert K

    2011-07-01

    The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review. PMID:21552596

  11. Investigation of photocalalytic activity of ZnO prepared by spray pyrolis with various precursors

    NASA Astrophysics Data System (ADS)

    Bourfaa, F.; Lamri Zeggar, M.; A, A.; Aida, M. S.; Attaf, N.

    2016-03-01

    Semiconductor photocatalysts such as ZnO has attracted much attention in recent years due to their various applications for the degradation of organic pollutants in water, air and in dye sensitized photovoltaic solar cell. In the present work, ZnO thin films were prepared by ultrasonic spray pyrolysis by using different precursors namely: acetate, chloride and zinc nitrate in order to investigate their influence on ZnO photocatalytic activity. The films crystalline structure was studied by mean of X- ray diffraction measurements (XRD) and the films surface morphology by Scanning Electron Microscopy (SEM). The films optical properties were studied by mean of UV-visible spectroscopy. The prepared films were tested for the degradation of the red reactive dye largely used in textile industry. As a result, we found that the zinc nitrate is the best precursor to prepare ZnO thin films suitable for a good photocatalytic activity.

  12. Molecular dynamics simulation study on substrate temperature dependence of sputtering yields for an organic polymer under ion bombardment

    SciTech Connect

    Yamashiro, Masashi; Yamada, Hideaki; Hamaguchi, Satoshi

    2007-02-15

    Substrate temperature dependence of sputtering yields in organic polymer etching processes has been examined with the use of molecular dynamics (MD) simulations. The simulation results indicate that structural weakness arising from high substrate temperatures alone is not sufficient to account for the experimentally observed strong dependence of sputtering yields on substrate temperatures. In other words, thermal desorption is likely to increase significantly at high substrate temperatures in reactive ion etching processes of organic polymers.

  13. Sputtering technology in solid film lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1978-01-01

    Current and potential sputtering technology is reviewed as it applies primarily to the deposition of MoS2, though such lubricants as WS2 and PTFE are also considered. It is shown by electron microscopy and surface sensitive analytical techniques that the lubricating properties of sputtered MoS2 films are directly influenced by the sputtering parameters selected (i.e., power density, pressure, sputter etching, dc-biasing, etc.), substrate temperature, chemistry, topography, and environmental conditions during the friction test. Electron micrographs and diffractograms of sputtered MoS2 films clearly show the resultant changes in film morphology which affect film adherence and frictional properties.

  14. Chemical stability enhancement of lithium conducting solid electrolyte plates using sputtered LiPON thin film

    NASA Technical Reports Server (NTRS)

    West, W. C.; Whitacre, J. F.; Lim, J. R.

    2004-01-01

    Sputter deposition of LiPON films directly onto high Li+ conductivity solid electrolyte plates has been investigated as a means to minimize the reactivity of the plates to metallic Li. The LiPON films were shown to effectively passivate the plates in contact with metallic Li, in contrast to unpassivated plates that reacted immediately in contact with Li metal.

  15. Features of AlN film grown by ion-plasma sputtering

    NASA Astrophysics Data System (ADS)

    Lubyanskiy, Ya V.; Bondarev, A. D.; Soshnikov, I. P.; Kotlyar, K. P.; Kirilenko, D. A.; Bert, N. A.; Ayusheva, K. R.; Tarasov, I. S.

    2016-08-01

    The work under consideration presents research of structure, composition and optical properties of aluminium nitride thin films grown by reactive ion plasma sputtering. Aluminium nitride films are shown to contain amorphous and polycrystalline phases. Amorphous phase presence influences on refraction and absorption indexes. Conditions of polycrystalline films with primary (dedicated) orientation synthesis are revealed.

  16. Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor

    NASA Astrophysics Data System (ADS)

    Ranwa, Sapana; Singh Barala, Surendra; Fanetti, Mattia; Kumar, Mahesh

    2016-08-01

    We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor’s performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.

  17. Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor.

    PubMed

    Ranwa, Sapana; Barala, Surendra Singh; Fanetti, Mattia; Kumar, Mahesh

    2016-08-26

    We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor's performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment. PMID:27418478

  18. Catalyst-Free Synthesis of ZnO Nanowires on Oxidized Silicon Substrate for Gas Sensing Applications.

    PubMed

    Behera, B; Chandra, S

    2015-06-01

    In the present work, we report the synthesis of nanostructured ZnO by oxidation of zinc film without using a seed or catalyst layer. The zinc films were deposited on oxidized Si substrates by RF magnetron sputtering process. These were oxidized in dry and wet air/oxygen ambient. The optimized process yielded long nanowires of ZnO having diameter of around 60-70 nm and spread uniformly over the surface. The effect of oxidation temperature, time, Zn film thickness and the ambient has strong influence on the morphology of resulting nanostruxctured ZnO film. The films were characterized by scanning electron microscopy for morphological studies and X-ray diffraction (XRD) analysis to study the phase of the nanostructured ZnO. Room temperature photoluminescence (PL) measurements of the nanowires show UV and green emission. A sensor was designed and fabricated using nanostructured ZnO film, incorporating inter-digital-electrode (IDE) for the measurement of resistance of the sensing layer. The gas sensing properties were investigated from the measurement of change in resistance when exposed to vapours of different volatile organic compound (VOC) such as acetone, ethanol, methanol and 2-propanol. The results suggest that ZnO nanowires fabricated by this method have potential application in gas sensors.

  19. Influence of Gas Flow Rate for Formation of Aligned Nanorods in ZnO Thin Films for Solar-Driven Hydrogen Production

    SciTech Connect

    Shet, S.; Chen, L.; Tang, H.; Nuggehalli, R.; Wang, H.; Yan, Y.; Turner, J.; Al-Jassim, M.

    2012-04-01

    ZnO thin films have been deposited in mixed Ar/N{sub 2} gas ambient at substrate temperature of 500 C by radiofrequency sputtering of ZnO targets. We find that an optimum N{sub 2}-to-Ar ratio in the deposition ambient promotes the formation of well-aligned nanorods. ZnO thin films grown in ambient with 25% N{sub 2} gas flow rate promoted nanorods aligned along c-axis and exhibit significantly enhanced photoelectrochemical (PEC) response, compared with ZnO thin films grown in an ambient with different N{sub 2}-to-Ar gas flow ratios. Our results suggest that chamber ambient is critical for the formation of aligned nanostructures, which offer potential advantages for improving the efficiency of PEC water splitting for H{sub 2} production.

  20. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    SciTech Connect

    Belmoubarik, M.; Nozaki, T.; Sahashi, M.; Endo, H.

    2013-05-07

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co{sub 3}Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 Degree-Sign C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 {Omega} cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co{sub 3}Pt surface oxidation was discussed.

  1. Photovoltaic Conversion Enhancement of a Carbon Quantum Dots/p-Type CuAlO2/n-Type ZnO Photoelectric Device.

    PubMed

    Pan, Jiaqi; Sheng, Yingzhuo; Zhang, Jingxiang; Huang, Peng; Zhang, Xin; Feng, Boxue

    2015-04-22

    Carbon quantum dots (C QDs)/p-type CuAlO2/n-type ZnO photoelectric bilayer film composites were prepared by a simple route, through which ZnO films were sputtered on crystal quartz substrates and CuAlO2 films were prepared by sol-gel on ZnO films and then these bilayer films were composited with C QDs on their surface. The characterization results indicated that C QDs were well combined with the surface of the CuAlO2 films. The photovoltage and photocurrent of these bilayer film composites were investigated under illumination and darkness switching, which demonstrated to be significantly enhanced compared with those of the CuAlO2/ZnO bilayer films. Through analysis, this enhancement of the photoconductivity was mainly attributed to C QDs with unique up-converted photoluminescence behavior. PMID:25822085

  2. Sputtering technology in solid film lubrication

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1978-01-01

    Potential and present sputtering technology is discussed as it applies to the deposition of solid film lubricants particularly MoS2, WS2, and PTFE. Since the sputtered films are very thin, the selection of the sputtering parameters and substrate condition is very critical as reflected by the lubricating properties. It was shown with sputtered MoS2 films that the lubricating characteristics are directly affected by the selected sputtering parameters (power density, pressure, sputter etching, dc-biasing, etc.) and the substrate temperature, chemistry, topography and the environmental conditions during the friction tests. Electron microscopy and other surface sensitive analytical techniques illustrate the resulting changes in sputtered MoS2 film morphology and chemistry which directly influence the film adherence and frictional properties.

  3. Redeposition of the sputtered surface in limiters

    SciTech Connect

    Brooks, J.N.; McGrath, R.T.

    1981-01-01

    Erosion of the surface coating of a pumped limiter by sputtering may be a critical life-limiting issue for future tokamak reactors. Redeposition of the sputtered material, however, may extend the coating life significantly. This subject has now been studied through the use of a code which models the redeposition of sputtered material which gets ionized in the scrape-off layer. The code also treats the transfer of wall-sputtered material to the limiter. The code uses models of the plasma density and temperature in the scrape-off zone, sheath potential, sputtering coefficients, spatial distribution of the sputtered atoms, and electron impact ionization coefficient for the sputtered atoms. The studies were made for high flux and low flux edge conditions corresponding to FED and STARFIRE limiters and assumed plasma-edge parameters. The results indicate that substantial redeposition from the scrape-off layer ionized neutrals occurs in the cases considered.

  4. Transparent Conducting ZnO Thin Films Doped with Al and Mo

    SciTech Connect

    Duenow, J.; Gessert, T.; Wood, D.; Young, D.; Coutts, T.

    2007-01-01

    Transparent conducting oxide (TCO) thin films are a vital part of photovoltaic cells, flat-panel displays, and electrochromic windows. ZnO-based TCOs, due to the relative abundance of Zn, may reduce production costs compared to those of the prevalent TCO In2O3:Sn (ITO). Undoped ZnO, ZnO:Al (0.5, 1, and 2 wt.% Al2O3), and ZnO:Mo (2 wt.%) films were deposited by RF magnetron sputtering. Controlled incorporation of H2 in the Ar sputtering ambient increased mobility of undoped ZnO by a factor of ~20 to 48 cm2V-1s-1. H2 also appears to catalyze ionization of dopants. This enabled lightly doped ZnO:Al to provide comparable conductivity to the standard 2 wt.%-doped ZnO:Al while demonstrating reduced infrared absorption. Mo was found to be an n-type dopant of ZnO, though material properties did not match those of ZnO:Al. Scattering mechanisms were investigated using temperature-dependent Hall measurements and the method of four coefficients. This abstract is subject to government rights.

  5. Growth of Cu{sub 2}O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    SciTech Connect

    Wong, L. M.; Chiam, S. Y.; Wang, S. J.; Pan, J. S.; Huang, J. Q.; Chim, W. K.

    2010-08-15

    Cu{sub 2}O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu{sub 2}O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu{sub 2}O. Based on this finding, we fabricate heterojunctions of p-type Cu{sub 2}O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu{sub 2}O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu{sub 2}O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu{sub 2}O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  6. Growth of Cu2O on Ga-doped ZnO and their interface energy alignment for thin film solar cells

    NASA Astrophysics Data System (ADS)

    Wong, L. M.; Chiam, S. Y.; Huang, J. Q.; Wang, S. J.; Pan, J. S.; Chim, W. K.

    2010-08-01

    Cu2O thin films are deposited by direct current reactive magnetron sputtering on borofloat glass and indium tin oxide (ITO) coated glass at room temperature. The effect of oxygen partial pressure on the structures and properties of Cu2O thin films are investigated. We show that oxygen partial pressure is a crucial parameter in achieving pure phases of CuO and Cu2O. Based on this finding, we fabricate heterojunctions of p-type Cu2O with n-type gallium doped ZnO (GZO) on ITO coated glass substrates by pulsed laser deposition for GZO thin films. The energy band alignment for thin films of Cu2O/GZO on ITO glass is characterized using high-resolution x-ray photoelectron spectroscopy. The energy band alignment for the Cu2O/GZO heterojunctions is determined to be type II with a valence band offset of 2.82 eV and shows negligible effects of variation with gallium doping. The higher conduction band of the Cu2O relative to that of GZO in the obtained band alignment shows that the heterojunctions are suitable for solar cell application based on energy levels consideration.

  7. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature.

    PubMed

    Stan, G E; Pasuk, I; Husanu, M A; Enculescu, I; Pina, S; Lemos, A F; Tulyaganov, D U; El Mabrouk, K; Ferreira, J M F

    2011-12-01

    Thin (380-510 nm) films of a low silica content bioglass with MgO, B(2)O(3), and CaF(2) as additives were deposited at low-temperature (150°C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (~73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (~46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (~50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO(3)) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

  8. ZnO nanoparticle-induced oxidative stress triggers apoptosis by activating JNK signaling pathway in cultured primary astrocytes

    NASA Astrophysics Data System (ADS)

    Wang, Jieting; Deng, Xiaobei; Zhang, Fang; Chen, Deliang; Ding, Wenjun

    2014-03-01

    It has been documented in in vitro studies that zinc oxide nanoparticles (ZnO NPs) are capable of inducing oxidative stress, which plays a crucial role in ZnO NP-mediated apoptosis. However, the underlying molecular mechanism of apoptosis in neurocytes induced by ZnO NP exposure was not fully elucidated. In this study, we investigated the potential mechanisms of apoptosis provoked by ZnO NPs in cultured primary astrocytes by exploring the molecular signaling pathways triggered after ZnO NP exposure. ZnO NP exposure was found to reduce cell viability in MTT assays, increase lactate dehydrogenase (LDH) release, stimulate intracellular reactive oxygen species (ROS) generation, and elicit caspase-3 activation in a dose- and time-dependent manner. Apoptosis occurred after ZnO NP exposure as evidenced by nuclear condensation and poly(ADP-ribose) polymerase-1 (PARP) cleavage. A decrease in mitochondrial membrane potential (MMP) with a concomitant increase in the expression of Bax/Bcl-2 ratio suggested that the mitochondria also mediated the pathway involved in ZnO NP-induced apoptosis. In addition, exposure of the cultured cells to ZnO NPs led to phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK). Moreover, JNK inhibitor (SP600125) significantly reduced ZnO NP-induced cleaved PARP and cleaved caspase-3 expression, but not ERK inhibitor (U0126) or p38 MAPK inhibitor (SB203580), indicating that JNK signaling pathway is involved in ZnO NP-induced apoptosis in primary astrocytes.

  9. Ultrasonic-assisted degradation of phenazopyridine with a combination of Sm-doped ZnO nanoparticles and inorganic oxidants.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Ziarani, Ghodsi Mohammadi

    2016-01-01

    Pure and samarium doped ZnO nanoparticles were synthesized by a sonochemical method and characterized by TEM, SEM, EDX, XRD, Pl, and DRS techniques. The average crystallite size of pure and Sm-doped ZnO nanoparticles was about 20 nm. The sonocatalytic activity of pure and Sm-doped ZnO nanoparticles was considered toward degradation of phenazopyridine as a model organic contaminant. The Sm-doped ZnO nanoparticles with Sm concentration of 0.4 mol% indicated a higher sonocatalytic activity (59%) than the pure ZnO (51%) and other Sm-doped ZnO nanoparticles. It was believed that Sm(3+) ion with optimal concentration (0.4 mol%) can act as superficial trapping for electrons in the conduction band of ZnO and delayed the recombination of charge carriers. The influence of the nature and concentration of various oxidants, including periodate, hydrogen peroxide, peroxymonosulfate, and peroxydisulfate on the sonocatalytic activity of Sm-doped ZnO nanoparticles was studied. The influence of the oxidants concentration (0.2-1.4 g L(-1)) on the degradation rate was established by the 3D response surface and the 2D contour plots. The results demonstrated that the utilizing of oxidants in combination with Sm-doped ZnO resulting in rapid removal of contaminant, which can be referable to a dual role of oxidants; (i) scavenging the generated electrons in the conduction band of ZnO and (ii) creating highly reactive radical species under ultrasonic irradiation. It was found that the Sm-doped ZnO and periodate combination is the most efficient catalytic system under ultrasonic irradiation.

  10. Sputtered silver oxide layers for surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Büchel, D.; Mihalcea, C.; Fukaya, T.; Atoda, N.; Tominaga, J.; Kikukawa, T.; Fuji, H.

    2001-07-01

    We present results of reactively sputtered silver oxide thin films as a substrate material for surface-enhanced Raman spectroscopy (SERS). Herein, we show that deposited layers develop an increasingly strong SERS activity upon photoactivation at 488 nm. A benzoic acid/2-propanol solution was used to demonstrate that the bonding of molecules to SERS active sites at the surface can be followed by investigating temporal changes of the corresponding Raman intensities. Furthermore, the laser-induced structural changes in the silver oxide layers lead to a fluctuating SERS activity at high laser intensities which also affects the spectral features of amorphous carbon impurities.

  11. Transport of sputtered particles in capacitive sputter sources

    NASA Astrophysics Data System (ADS)

    Trieschmann, Jan; Mussenbrock, Thomas

    2015-07-01

    The transport of sputtered aluminum inside a multi frequency capacitively coupled plasma chamber is simulated by means of a kinetic test multi-particle approach. A novel consistent set of scattering parameters obtained for a modified variable hard sphere collision model is presented for both argon and aluminum. An angular dependent Thompson energy distribution is fitted to results from Monte Carlo simulations and used for the kinetic simulation of the transport of sputtered aluminum. For the proposed configuration, the transport of sputtered particles is characterized under typical process conditions at a gas pressure of p = 0.5 Pa. It is found that—due to the peculiar geometric conditions—the transport can be understood in a one dimensional picture, governed by the interaction of the imposed and backscattered particle fluxes. It is shown that the precise geometric features play an important role only in proximity to the electrode edges, where the effect of backscattering from the outside chamber volume becomes the governing mechanism.

  12. Role of physical and chemical interactions in the antibacterial behavior of ZnO nanoparticles against E. coli.

    PubMed

    Jiang, Yunhong; Zhang, Lingling; Wen, Dongsheng; Ding, Yulong

    2016-12-01

    Zinc oxide (ZnO) nanoparticles (NPs) exhibit antibacterial activity against both Gram-positive and Gram-negative bacteria. However, the antimicrobial mechanism of ZnO NPs remains unclear. In this study, we investigated the interactions among ZnO NPs, released chemicals (Zn(2+) and Reactive Oxygen Species, ROS) and Escherichia coli (E. coli) cells. ZnO NPs without contacting with bacterial cells showed strong antibacterial effect. The results of the leakage of intracellular K(+) and integrity of carboxyfluoresce in-filled liposomes showed that ZnO NPs have antimicrobial activity against E. coli by non-specifically disrupting E. coli membranes. Traces of zinc ions (1.25mg/L) and hydrogen peroxide (from 1.25 to 4.5μM/L) were detected in ZnO NPs suspensions, but was insufficient to cause the antibacterial effect. However, the addition of radical scavengers suppressed the bactericidal effect of ZnO coated films against E. coli, potentially implicating ROS generation, especially hydroxyl radicals, in the antibacterial ability of ZnO NPs.

  13. Role of physical and chemical interactions in the antibacterial behavior of ZnO nanoparticles against E. coli.

    PubMed

    Jiang, Yunhong; Zhang, Lingling; Wen, Dongsheng; Ding, Yulong

    2016-12-01

    Zinc oxide (ZnO) nanoparticles (NPs) exhibit antibacterial activity against both Gram-positive and Gram-negative bacteria. However, the antimicrobial mechanism of ZnO NPs remains unclear. In this study, we investigated the interactions among ZnO NPs, released chemicals (Zn(2+) and Reactive Oxygen Species, ROS) and Escherichia coli (E. coli) cells. ZnO NPs without contacting with bacterial cells showed strong antibacterial effect. The results of the leakage of intracellular K(+) and integrity of carboxyfluoresce in-filled liposomes showed that ZnO NPs have antimicrobial activity against E. coli by non-specifically disrupting E. coli membranes. Traces of zinc ions (1.25mg/L) and hydrogen peroxide (from 1.25 to 4.5μM/L) were detected in ZnO NPs suspensions, but was insufficient to cause the antibacterial effect. However, the addition of radical scavengers suppressed the bactericidal effect of ZnO coated films against E. coli, potentially implicating ROS generation, especially hydroxyl radicals, in the antibacterial ability of ZnO NPs. PMID:27612837

  14. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1995-01-01

    A process for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B.sub.4 C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil.

  15. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1995-02-28

    A process is disclosed for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B{sub 4}C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil. 7 figs.

  16. Energy spectrum of sputtered uranium

    NASA Technical Reports Server (NTRS)

    Weller, R. A.; Tombrello, T. A.

    1977-01-01

    The fission track technique for detecting uranium 235 was used in conjunction with a mechanical time-of-flight spectrometer to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched U-235 foil by 80 keV Ar-40(+) ions. The spectrum was found to exhibit a peak in the region 2-4 eV and to decrease approximately as E to the -1.77 power for E is approximately greater than 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the ramdom collision cascade model of sputtering.

  17. In-situ sputtering apparatus

    SciTech Connect

    Erickson, Mark R.; Poole, Henry J.; Custer, III, Arthur W.; Hershcovitch, Ady

    2015-06-09

    A sputtering apparatus that includes at least a target presented as an inner surface of a confinement structure, the inner surface of the confinement structure is preferably an internal wall of a circular tube. A cathode is disposed adjacent the internal wall of the circular tube. The cathode preferably provides a hollow core, within which a magnetron is disposed. Preferably, an actuator is attached to the magnetron, wherein a position of the magnetron within the hollow core is altered upon activation of the actuator. Additionally, a carriage supporting the cathode and communicating with the target is preferably provided, and a cable bundle interacting with the cathode and linked to a cable bundle take up mechanism provided power and coolant to the cathode, magnetron, actuator and an anode of the sputtering apparatus.

  18. Sputtering Holes with Ion Beamlets

    NASA Technical Reports Server (NTRS)

    Byers, D. C.; Banks, B. A.

    1974-01-01

    Ion beamlets of predetermined configurations are formed by shaped apertures in the screen grid of an ion thruster having a double grid accelerator system. A plate is placed downstream from the screen grid holes and attached to the accelerator grid. When the ion thruster is operated holes having the configuration of the beamlets formed by the screen grid are sputtered through the plate at the accelerator grid.

  19. Microfluidic pumps employing surface acoustic waves generated in ZnO thin films

    SciTech Connect

    Du, X. Y.; Flewitt, A. J.; Milne, W. I.; Fu, Y. Q.; Luo, J. K.

    2009-01-15

    ZnO thin film based surface acoustic wave (SAW) devices have been utilized to fabricate microfluidic pumps. The SAW devices were fabricated on nanocrystalline ZnO piezoelectric thin films deposited on Si substrates using rf magnetron sputtering and use a Sezawa wave mode for effective droplet motion. The as-deposited ZnO surface is hydrophilic, with a water contact angle of {approx}75 deg., which prevents droplet pumping. Therefore, the ZnO surface was coated using a self-assembled monolayer of octadecyltrichlorosilane which forms a hydrophobic surface with a water contact angle of {approx}110 deg. Liquid droplets between 0.5 and 1 {mu}l in volume were successfully pumped on the hydrophobic ZnO surface at velocities up to 1 cm s{sup -1}. Under acoustic pressure, the water droplet on an hydrophilic surface becomes deformed, and the asymmetry in the contact angle at the trailing and leading edges allow the force acting upon the droplet to be calculated. These forces, which increase with input voltage above a threshold level, are found to be in the range of {approx}100 {mu}N. A pulsed rf signal has also been used to demonstrate precision manipulation of the liquid droplets. Furthermore, a SAW device structure is demonstrated in which the ZnO piezoelectric only exists under the input and output transducers. This structure still permits pumping, while avoiding direct contact between the piezoelectric material and the fluid. This is of particular importance for biological laboratory-on-a-chip applications.

  20. In situ stress evolution during magnetron sputtering of transition metal nitride thin films

    SciTech Connect

    Abadias, G.; Guerin, Ph.

    2008-09-15

    Stress evolution during reactive magnetron sputtering of TiN, ZrN, and TiZrN layers was studied using real-time wafer curvature measurements. The presence of stress gradients is revealed, as the result of two kinetically competing stress generation mechanisms: atomic peening effect, inducing compressive stress, and void formation, leading to a tensile stress regime predominant at higher film thickness. No stress relaxation is detected during growth interrupt in both regimes. A change from compressive to tensile stress is evidenced with increasing film thickness, Ti content, sputtering pressure, and decreasing bias voltage.

  1. Radio-Frequency Superimposed Direct Current Magnetron Sputtered Ga:ZnO Transparent Conducting Thin Films

    SciTech Connect

    Sigdel, A. K.; Ndione, P. F.; Perkins, J. D.; Gennett, T.; van Hest, M. F. A. M.; Shaheen, S. E.; Ginley, D. S.; Berry, J. J.

    2012-05-01

    The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

  2. Radio-frequency superimposed direct current magnetron sputtered Ga:ZnO transparent conducting thin films

    SciTech Connect

    Sigdel, Ajaya K.; Shaheen, Sean E.; Ndione, Paul F.; Perkins, John D.; Gennett, Thomas; Hest, Maikel F. A. M. van; Ginley, David S.; Berry, Joseph J.

    2012-05-01

    The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

  3. Collision-spike sputtering of Au nanoparticles

    SciTech Connect

    Sandoval, Luis; Urbassek, Herbert M.

    2015-08-06

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For this specific case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31% of the impact energy remains in the nanoparticles after impact; the remainder is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80% of that of free nanoparticles due to the suppression of forward sputtering.

  4. Collision-spike sputtering of Au nanoparticles

    DOE PAGES

    Sandoval, Luis; Urbassek, Herbert M.

    2015-08-06

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For this specific case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31% of the impact energy remains in the nanoparticles after impact; the remaindermore » is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80% of that of free nanoparticles due to the suppression of forward sputtering.« less

  5. Collision-spike Sputtering of Au Nanoparticles.

    PubMed

    Sandoval, Luis; Urbassek, Herbert M

    2015-12-01

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For the particular case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31 % of the impact energy remains in the nanoparticles after impact; the remainder is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80 % of that of free nanoparticles due to the suppression of forward sputtering.

  6. Sputtering and ion plating for aerospace applications

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1981-01-01

    Sputtering and ion plating technologies are reviewed in terms of their potential and present uses in the aerospace industry. Sputtering offers great universality and flexibility in depositing any material or in the synthesis of new ones. The sputter deposition process has two areas of interest: thin film and fabrication technology. Thin film sputtering technology is primarily used for aerospace mechanical components to reduce friction, wear, erosion, corrosion, high temperature oxidation, diffusion and fatigue, and also to sputter-construct temperature and strain sensors for aircraft engines. Sputter fabrication is used in intricate aircraft component manufacturing. Ion plating applications are discussed in terms of the high energy evaporant flux and the high throwing power. Excellent adherence and 3 dimensional coverage are the primary attributes of this technology.

  7. Heavily-doped ZnO:Al thin films prepared by using magnetron Co-sputtering: Optical and electrical properties

    NASA Astrophysics Data System (ADS)

    Moon, Eun-A.; Jun, Young-Kil; Kim, Nam-Hoon; Lee, Woo-Sun

    2016-07-01

    Photovoltaic applications require transparent conducting-oxide (TCO) thin films with high optical transmittance in the visible spectral region (380 - 780 nm), low resistivity, and high thermal/chemical stability. The ZnO thin film is one of the most common alternatives to the conventional indium-tin-oxide (ITO) thin film TCO. Highly transparent and conductive ZnO thin films can be prepared by doping with group III elements. Heavily-doped ZnO:Al (AZO) thin films were prepared by using the RF magnetron co-sputtering method with ZnO and Al targets to obtain better characteristics at a low cost. The RF sputtering power to each target was varied to control the doping concentration in fixed-thickness AZO thin films. The crystal structures of the AZO thin films were analyzed by using X-ray diffraction. The morphological microstructure was observed by using scanning electron microscopy. The optical transmittance and the band gap energy of the AZO thin films were examined with an UV-visible spectrophotometer in the range of 300 - 1800 nm. The resistivity and the carrier concentration were examined by using a Hall-effect measurement system. An excellent optical transmittance > 80% with an appropriate band gap energy (3.26 - 3.27 eV) and an improved resistivity (~10 -1 Ω·cm) with high carrier concentration (1017 - 1019 cm -3) were demonstrated in 350-nm-thick AZO thin films for thin-film photovoltaic applications.

  8. Comparison of SiOx structure in RF sputtered samples

    NASA Astrophysics Data System (ADS)

    Swart, H. C.; van Hattum, E. D.; Arnoldbik, W. M.; Habraken, F. H. P. M.

    2004-08-01

    The nano-structure of rf magnetron sputtered SiOx films is addressed. More specifically, it was examined whether boundary effects created by the confinement of the material into a thin film induces the formation of a layered structure parallel to the surface during annealing. Different films of SiOx (0 < x < 2) were deposited by an RF magnetron reactive sputtering technique by controlling the relative O2/Ar gas flow during sputter deposition. The graded samples used in this study were 10 nm (x = 2 at the interface to 0 at the surface) and 20 nm (x = 1 to 0), respectively. Samples were annealed in situ from room temperature to 570 °C. Infrared analysis (IR) and X-ray Photoelectron Spectroscopy (XPS) were used to analyze and compare the samples. IR spectra before and after annealing were compared with each other. XPS spectra were drawn during annealing to monitor the changes in the SiOx structure. The sputtered SiOx showed a tendency to decompose into Si and SiO2 during the annealing process. The reaction is characterized by an initial increase in the reaction rate when the temperature was raised, followed by a decrease in the reaction rate toward equilibrium. Two possible models can describe the process. The layer consists of a mixture of all possible sub-oxides with different activation energies for each sub-oxide or the O can segregate from the Si rich region toward an oxygen rich region, where the accumulation of the oxygen forms a diffusion barrier against further diffusion of the oxygen atoms at that specific temperature.

  9. Charge Compensated (Al, N) Co-Doped Zinc Oxide (ZnO) Films for Photlelectrochemical Application

    SciTech Connect

    Shet, S.

    2012-01-01

    ZnO thin films with significantly reduced bandgaps were synthesized by doping N and co-doping Al and N at 100oC. All the films were synthesized by radio-frequency magnetron sputtering on F-doped tin-oxide-coated glass. We found that co-doped ZnO:(Al,N) thin films exhibited significantly enhanced crystallinity as compared to ZnO doped solely with N, ZnO:N, at the same growth conditions. Furthermore, annealed ZnO:(Al,N) thin films exhibited enhanced N incorporation over ZnO:N films. As a result, ZnO:(Al,N) films exhibited improved photocurrents than ZnO:N films grown with pure N doping, suggesting that charge-compensated donor-acceptor co-doping could be a potential method for bandgap reduction of wide-bandgap oxide materials to improve their photoelectrochemical performance.

  10. Decrease in work function of transparent conducting ZnO tin films by phosphorus ion implantation.

    PubMed

    Heo, Gi-Seok; Hong, Sang-Jin; Park, Jong-Woon; Choi, Bum-Ho; Lee, Jong-Ho; Shin, Dong-Chan

    2008-09-01

    To confirm the possibility of engineering the work function of ZnO thin films, we have implanted phosphorus ions into ZnO thin films deposited by radio-frequency magnetron sputtering. The fabricated films show n-type characteristics. It is shown that the electrical and optical properties of those thin films vary depending sensitively on the ion dose and rapid thermal annealing time. Compared to as-deposited ZnO films, the work-function of phosphorus ion-implanted ZnO thin films is observed to be lower and decreases with increasing ion doses. It is likely that the zinc or oxygen vacancies are firstly filled with the implanted phosphorus ions. With further increased ions, free electrons are generated as Zn2+ sites are replaced by those ions or interstitial phosphorus ions increase at the lattice sites, the fermi level by which approaches the conduction band and thus the work function decreases. Those films exhibit the optical transmittance higher than 85% within the visible wavelength range (up to 800 nm).

  11. ZnO micro-nano composite hydrophobic film prepared by the three-step method

    NASA Astrophysics Data System (ADS)

    Ma, Kai; Li, Hua; Zhang, Han; Xu, Xiao-Liang; Gong, Mao-Gang; Yang, Zhou

    2009-05-01

    The hydrophobicity of the lotus leaf is mainly due to its surface micro-nano composite structure. In order to mimic the lotus structure, ZnO micro-nano composite hydrophobic films were prepared via the three-step method. On thin buffer films of SiO2, which were first fabricated on glass substrates by the sol-gel dip-coating method, a ZnO seed layer was deposited via RF magnetron sputtering. Then two different ZnO films, micro-nano and micro-only flower-like structures, were grown by the hydrothermal method. The prepared films have different hydrophobic properties after surface modification. The structures of the obtained ZnO films were characterized using x-ray diffraction and field-emission scanning electron microscopy. A conclusion that a micro-nano composite structure is more beneficial to hydrophobicity than a micro-only structure was obtained through research into the effect of structure on hydrophobic properties.

  12. Schottky-contacted vertically self-aligned ZnO nanorods for hydrogen gas nanosensor applications

    SciTech Connect

    Ranwa, Sapana; Kumar, Mohit; Kumar, Mahesh; Singh, Jitendra; Fanetti, Mattia

    2015-07-21

    Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ∼75 nm, ∼850 nm, and ∼1.5 × 10{sup 10} cm{sup −2}, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9–16 s) and moderate recovery time (100–200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs.

  13. Schottky-contacted vertically self-aligned ZnO nanorods for hydrogen gas nanosensor applications

    NASA Astrophysics Data System (ADS)

    Ranwa, Sapana; Kumar, Mohit; Singh, Jitendra; Fanetti, Mattia; Kumar, Mahesh

    2015-07-01

    Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ˜75 nm, ˜850 nm, and ˜1.5 × 1010 cm-2, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9-16 s) and moderate recovery time (100-200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs.

  14. Cytotoxic effects of ZnO hierarchical architectures on RSC96 Schwann cells

    NASA Astrophysics Data System (ADS)

    Yin, Yixia; Lin, Qiang; Sun, Haiming; Chen, Dan; Wu, Qingzhi; Chen, Xiaohui; Li, Shipu

    2012-08-01

    The alteration in intracellular Zn2+ homeostasis is attributed to the generation of intracellular reactive oxygen species, which subsequently results in oxidative damage of organelles and cell apoptosis. In this work, the neurotoxic effects of ZnO hierarchical architectures (nanoparticles and microspheres, the prism-like and flower-like structures) were evaluated through the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay using RSC96 Schwann cells as the model. Cell apoptosis and cell cycle were detected using flow cytometry. The concentration of Zn2+ in the culture media was monitored using atomic absorption spectrometry. The results show that ZnO nanoparticles and microspheres displayed significant cytotoxic effects on RSC96 Schwann cells in dose- and time-dependent manners, whereas no or low cytotoxic effect was observed when the cells were treated with the prism-like and flower-like ZnO. A remarkable cell apoptosis and G2/M cell cycle arrest were observed when RSC96 Schwann cells were exposed to ZnO nanoparticles and microspheres at a dose of 80 μg/mL for 12 h. The time-dependent increase of Zn2+ concentration in the culture media suggests that the cytotoxic effects were associated with the decomposition of ZnO hierarchical architecture and the subsequent release of Zn2+. These results provide new insights into the cytotoxic effects of complex ZnO architectures, which could be prominently dominated by nanoscale building blocks.

  15. Cytotoxic effects of ZnO hierarchical architectures on RSC96 Schwann cells

    PubMed Central

    2012-01-01

    The alteration in intracellular Zn2+ homeostasis is attributed to the generation of intracellular reactive oxygen species, which subsequently results in oxidative damage of organelles and cell apoptosis. In this work, the neurotoxic effects of ZnO hierarchical architectures (nanoparticles and microspheres, the prism-like and flower-like structures) were evaluated through the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay using RSC96 Schwann cells as the model. Cell apoptosis and cell cycle were detected using flow cytometry. The concentration of Zn2+ in the culture media was monitored using atomic absorption spectrometry. The results show that ZnO nanoparticles and microspheres displayed significant cytotoxic effects on RSC96 Schwann cells in dose- and time-dependent manners, whereas no or low cytotoxic effect was observed when the cells were treated with the prism-like and flower-like ZnO. A remarkable cell apoptosis and G2/M cell cycle arrest were observed when RSC96 Schwann cells were exposed to ZnO nanoparticles and microspheres at a dose of 80 μg/mL for 12 h. The time-dependent increase of Zn2+ concentration in the culture media suggests that the cytotoxic effects were associated with the decomposition of ZnO hierarchical architecture and the subsequent release of Zn2+. These results provide new insights into the cytotoxic effects of complex ZnO architectures, which could be prominently dominated by nanoscale building blocks. PMID:22873432

  16. Rapid large-scale preparation of ZnO nanowires for photocatalytic application

    PubMed Central

    2011-01-01

    ZnO nanowires are a promising nanomaterial for applications in the fields of photocatalysis, nano-optoelectronics, and reinforced composite materials. However, the challenge of producing large-scale ZnO nanowires has stunted the development and practical utilization of ZnO nanowires. In this study, a modified carbothermal reduction method for preparing large-scale ZnO nanowires in less than 5 min is reported. The preparation was performed in a quartz tube furnace at atmospheric pressure without using any catalysts. A mixed gas of air and N2 with a volume ratio of 45:1 was used as the reactive and carrier gas. About 0.8 g ZnO nanowires was obtained using 1 g ZnO and 1 g graphite powder as source materials. The obtained nanowires exhibited a hexagonal wurtzite crystal structure with an average diameter of about 33 nm. Good photocatalytic activity of the nanowires toward the photodegradation of methylene blue dye under UV irradiation was also demonstrated. PMID:21968032

  17. Sputtering Threshold Energies of Heavy Ions

    NASA Technical Reports Server (NTRS)

    Mantenieks, Maris A.

    1999-01-01

    Sputter erosion in ion thrusters has been measured in lifetests at discharge voltages as low as 25 V. Thruster operation at this discharge voltage results in component erosion rates sufficiently low to satisfy most mission requirements. It has been recognized that most of the internal sputtering in ion thrusters is done by doubly charged ions. Knowledge of the sputtering threshold voltage of a xenon molybdenum system would be beneficial in understanding the sputtering process as well as making more accurate calculations of the sputtering rates of ion thruster components. Sputtering threshold energies calculated from various formulations found in the literature results in values ranging from 28 to 200 eV. It is evident that some of these formulations cannot be relied upon to provide sputtering thresholds with any degree of accuracy. This paper re-examines the threshold energies measurements made in the early sixties by Askerov and Sena, and Stuart and Wehner. The threshold voltages as derived by Askerov and au have been reevaluated by using a different extrapolation method of sputter yields at low ion energies. The resulting threshold energies are in general similar to those measured by Stuart and Wehner. An empirical relationship is derived,for mercury and xenon ions for the ratio of the sputtering threshold energy to the sublimation energy as a function of the ratio of target to ion atomic mass.

  18. Modified Sigmund sputtering theory: isotopic puzzle

    NASA Astrophysics Data System (ADS)

    Zhang, Z. L.; Zhang, L.

    2005-05-01

    The theory of anisotropic sputtering proposed by Zhang [Z.L. Zhang, Phys. Rev. B 71 026101 (2005).] and [Z.L. Zhang and L. Zhang, Radiat. Eff. Defects Solids 159(5) 301 (2004).] has been generalized to sputtering of isotopic mixtures. The present theory (modified Sigmund theory) has been shown to fit numerous simulations and experimental measurements, including energy and angular distribution of sputtered atoms. In particular, the theory has successfully solved the isotope puzzle of sputtering induced by low energy and heavy ion bombardment.

  19. Cytotoxic effects of ZnO nanoparticles on mouse testicular cells

    PubMed Central

    Han, Zhe; Yan, Qi; Ge, Wei; Liu, Zhi-Guo; Gurunathan, Sangiliyandi; De Felici, Massimo; Shen, Wei; Zhang, Xi-Feng

    2016-01-01

    Background Nanoscience and nanotechnology are developing rapidly, and the applications of nanoparticles (NPs) have been found in several fields. At present, NPs are widely used in traditional consumer and industrial products, however, the properties and safety of NPs are still unclear and there are concerns about their potential environmental and health effects. The aim of the present study was to investigate the potential toxicity of ZnO NPs on testicular cells using both in vitro and in vivo systems in a mouse experimental model. Methods ZnO NPs with a crystalline size of 70 nm were characterized with various analytical techniques, including ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and atomic force microscopy. The cytotoxicity of the ZnO NPs was examined in vitro on Leydig cell and Sertoli cell lines, and in vivo on the testes of CD1 mice injected with single doses of ZnO NPs. Results ZnO NPs were internalized by Leydig cells and Sertoli cells, and this resulted in cytotoxicity in a time- and dose-dependent manner through the induction of apoptosis. Apoptosis likely occurred as a consequence of DNA damage (detected as γ-H2AX and RAD51 foci) caused by increase in reactive oxygen species associated with loss of mitochondrial membrane potential. In addition, injection of ZnO NPs in male mice caused structural alterations in the seminiferous epithelium and sperm abnormalities. Conclusion These results demonstrate that ZnO NPs have the potential to induce apoptosis in testicular cells likely through DNA damage caused by reactive oxygen species, with possible adverse consequences for spermatogenesis and therefore, male fertility. This suggests that evaluating the potential impacts of engineered NPs is essential prior to their mass production, to address both the environmental and human health concerns and also to develop sustainable and safer nanomaterials. PMID:27785022

  20. Defects in ZnO

    NASA Astrophysics Data System (ADS)

    McCluskey, M. D.; Jokela, S. J.

    2009-10-01

    Zinc oxide (ZnO) is a wide band gap semiconductor with potential applications in optoelectronics, transparent electronics, and spintronics. The high efficiency of UV emission in this material could be harnessed in solid-state white lighting devices. The problem of defects, in particular, acceptor dopants, remains a key challenge. In this review, defects in ZnO are discussed, with an emphasis on the physical properties of point defects in bulk crystals. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. However, experiments and theory have shown that O vacancies are deep donors, while Zn interstitials are too mobile to be stable at room temperature. Group-III (B, Al, Ga, and In) and H impurities account for most of the n-type conductivity in ZnO samples. Interstitial H donors have been observed with IR spectroscopy, while substitutional H donors have been predicted from first-principles calculations but not observed directly. Despite numerous reports, reliable p-type conductivity has not been achieved. Ferromagnetism is complicated by the presence of secondary phases, grain boundaries, and native defects. The famous green luminescence has several possible origins, including Cu impurities and Zn vacancies. The properties of group-I (Cu, Li, and Na) and group-V (N, P, As, and Sb) acceptors, and their complexes with H, are discussed. In the future, doping of ZnO nanocrystals will rely on an understanding of these fundamental properties.

  1. Study of Doped ZnO Films Synthesized by Combining Vapor Gases and Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, Sandor L.; George, M. A.

    2000-01-01

    The properties and structure of the ZnO material are similar to those of the GaN. Since an excitonic binding energy of ZnO is about 60 meV, it has strong potential for excitonic lasing at the room temperature. This makes synthesizing ZnO films for applications attractive. However, there are several hurdles in fabricating electro-optical devices from ZnO. One of those is in growing doped p-type ZnO films. Although techniques have been developed for the doping of both p-type and n-type ZnO, this remains an area that can be improved. In this presentation, we will report the experimental results of using both thermal vapor and pulsed laser deposition to grow doped ZnO films. The films are deposited on (0001) sapphire, (001) Si and quartz substrates by ablating a ZnO target. The group III and V elements are introduced into the growth chamber using inner gases. Films are characterized by x-ray diffraction, scanning probe microscopy, energy dispersive spectroscopy, Auger electron spectroscopy, and electrical measurements. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5 deg. In textured films, it rises to several degrees. Film surface morphology reveals an island growth pattern, but the size and density of these islands vary with the composition of the reactive gases. The electrical resistivity also changes with the doped elements. The relationship between the doping elements, gas composition, and film properties will be discussed.

  2. Chemical and physical sputtering effects on the surface morphology of carbon films grown by plasma chemical vapor deposition

    SciTech Connect

    Vazquez, Luis

    2009-08-01

    We have studied the influence of chemical and physical sputtering on the surface morphology of hydrogenated carbon films deposited on silicon substrates by bias-enhanced electron cyclotron resonance chemical vapor deposition. Atomic force microscopy based power spectrum density (PSD) and roughness analysis have been used to investigate the film morphology. This study has been possible due to the appropriate choice of the experimental variables, in particular, gas mixture, resulting in either nitrogen-free (a-C:H) or nitrogenated carbon (a-CN:H) films, and substrate bias (V{sub b}). Under these conditions, chemical sputtering is present for a-CN:H deposition but it is negligible for a-C:H film growth, while physical sputtering processes appear for both systems for V{sub b}<=-85 V. When physical sputtering does not operate, the film growth with simultaneous chemical sputtering leads to a characteristic a-CN:H granular surface morphology. Furthermore, PSD analysis reveals that a spatial correlation of the a-CN:H film surface roughness, up to distances approx300 nm, becomes a fingerprint of the coexistence of growth and chemical erosion processes on the film morphology. However, once physical sputtering takes place, the influence of chemical sputtering by reactive nitrogen species on the final surface morphology becomes negligible and both a-CN:H and a-C:H film morphologies are ultrasmooth.

  3. Sn doping induced enhancement in the activity of ZnO nanostructures against antibiotic resistant S. aureus bacteria.

    PubMed

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Zakaullah, M; Naqvi, Sajjad Haider; Badshah, Noor

    2013-01-01

    Highly ionic metal oxide nanostructures are attractive, not only for their physiochemical properties but also for antibacterial activity. Zinc oxide (ZnO) nanostructures are known to have inhibitory activity against many pathogens but very little is known about doping effects on it. The antibacterial activity of undoped ZnO and tin (Sn) doped ZnO nanostructures synthesized by a simple, versatile, and wet chemical technique have been investigated against Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa bacterial strains. It has been interestingly observed that Sn doping enhanced the inhibitory activity of ZnO against S. aureus more efficiently than the other two bacterial strains. From cytotoxicity and reactive oxygen species (ROS) production studies it is found that Sn doping concentration in ZnO does not alter the cytotoxicity and ROS production very much. It has also been observed that undoped and Sn doped ZnO nanostructures are biosafe and biocompatible materials towards SH-SY5Y Cells. The observed behavior of ZnO nanostructures with Sn doping is a new way to prevent bacterial infections of S. aureus, especially on skin, when using these nanostructures in creams or lotions in addition to their sunscreen property as an ultraviolet filter. Structural investigations have confirmed the formation of a single phase wurtzite structure of ZnO. The morphology of ZnO nanostructures is found to vary from spherical to rod shaped as a function of Sn doping. The excitation absorption peak of ZnO is observed to have a blue shift, with Sn doping leading toward a significant tuning in band gap.

  4. Physico-chemical characteristics of ZnO nanoparticles-based discs and toxic effect on human cervical cancer HeLa cells

    NASA Astrophysics Data System (ADS)

    Sirelkhatim, Amna; Mahmud, Shahrom; Seeni, Azman; Kaus, Noor Haida Mohd.; Sendi, Rabab

    2014-10-01

    In this study, we investigated physico-chemical properties of zinc oxide nanoparticles (ZnO NPs)-based discs and their toxicity on human cervical cancer HeLa cell lines. ZnO NPs (80 nm) were produced by the conventional ceramic processing method. FESEM analysis indicated dominant structure of nanorods with dimensions 100-500 nm in length, and 20-100 nm in diameter. The high content of ZnO nanorods in the discs probably played significant role in toxicity towards HeLa cells. Structural defects (oxygen vacancies and zinc/oxygen interstitials) were revealed by PL spectra peaks at 370-376 nm and 519-533 nm for the ZnO discs. The structural, optical and electrical properties of prepared sample have influenced the toxicological effects of ZnO discs towards HeLa cell lines via the generation of reactive oxygen species (ROS), internalization, membrane damage, and eventually cell death. The larger surface to volume area of the ZnO nanorods, combined with defects, stimulated enhanced toxicity via ROS generation hydrogen peroxide, hydroxyl radicals, and superoxide anion. The preliminary results confirmed the ZnO-disc toxicity on HeLa cells was significantly associated with the unique physicochemical properties of ZnO NPs and to our knowledge, this is the first cellular study for treatment of HeLa cells with ZnO discs made from 80 nm ZnO particles.

  5. Synthesis of ZnO:As Films Using Off-Axis Sputtering Deposition

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    As a novel oxide semiconductor material, ZnO is interesting for use in many applications. For fabricating electronic devices, it is important to have n- and p- type ZnO materials. Arsenic has been proven to be one of the p-type dopants for ZnO materials. However, information in studying the ZnAsO ternary compound films has been scarce. In order to investigate the morphology, structure and electrical properties of ZnAsO ternary compounds, ZnO:As films have been synthesized using off-axis sputtering deposition on various substrates including (100) Si and (0001) sapphire crystals. Films are grown under various growth conditions. ZnO:As targets with the atomic weight ratios of arsenic to zinc from 0.01 to 0.10 are used for film synthesis. The growth temperatures and pressures range from 350 to 550C and 5 to 150 mTorr, respectively. Argon to oxygen gas ratio for film growth is varied to examine the film quality as well. Film surface morphology, crystal structure, and compositions, are characterized using atomic force microscopy, x-ray diffraction, and energy dispersive spectroscopy, respectively. The compositions of target material and ZnO:As films grown under various conditions are then assessed. The electrical properties were also measured. The detail of these measurements will be discussed in the presentation.

  6. Development of sputtered techniques for thrust chambers. [coolant passage closing by triode sputtering

    NASA Technical Reports Server (NTRS)

    Mullaly, J. R.; Hecht, R. J.; Broch, J. W.; Allard, P. A.

    1976-01-01

    Procedures for closing out coolant passages in regeneratively cooled thrust chambers by triode sputtering, using post and hollow Cu-0.15 percent Zr cathodes are described. The effects of aluminum composite filler materials, substrate preparation, sputter cleaning, substrate bias current density and system geometry on closeout layer bond strength and structure are evaluated. High strength closeout layers were sputtered over aluminum fillers. The tensile strength and microstructure of continuously sputtered Cu-0.15 percent Zr deposits were determined. These continuous sputtered deposits were as thick as 0.75 cm. Tensile strengths were consistently twice as great as the strength of the material in wrought form.

  7. Dust Growth by RF Sputtering

    SciTech Connect

    Churton, B.; Samarian, A. A.; Coueedel, L.

    2008-09-07

    The effect of the dust particle growth by RF sputtering on glow discharge has been investigated. It has been found that the growth of dust particles modifies the electrical characteristics of the discharge. In particularly, the absolute value of the self-bias voltage decreases during the particle growth due to the electron losses on the dust particles. To find the correlation between the dust growth and the self bias evolution, dust particles have been collected at different times. The dust particle growth rate is found to be linear.

  8. Sputter metalization of Wolter type optical elements

    NASA Technical Reports Server (NTRS)

    Ledger, A. M.

    1977-01-01

    An analytical task showed that the coating thickness distribution for both internal and external optical elements coated using either electron beam or sputter sources can be made uniform and will not affect the surface figure of coated elements. Also, sputtered samples of nickel, molybdenum, iridium and ruthenium deposited onto both hot and cold substrates showed excellent adhesion.

  9. Deposition and characterization of magnetron sputtered bcc tantalum

    NASA Astrophysics Data System (ADS)

    Patel, Anamika

    The goal of this thesis was to provide scientific and technical research results for developing and characterizing tantalum (Ta) coatings on steel substrates deposited by DC magnetron sputtering. Deposition of tantalum on steel is of special interest for the protection it offers to surfaces, e.g. the surfaces of gun barrels against the erosive wear of hot propellant gases and the mechanical damage caused by the motion of launching projectiles. Electro-plated chromium is presently most commonly used for this purpose; however, it is considered to be carcinogenic in its hexavalent form. Tantalum is being investigated as non-toxic alternative to chromium and also because of its superior protective properties in these extreme environments. DC magnetron sputtering was chosen for this investigation of tantalum coatings on steel substrates because it is a versatile industrial proven process for deposition of metals. Sputter deposited Ta films can have two crystallographic structures: (1) body center cubic (bcc) phase, characterized by high toughness and high ductility and (2) a tetragonal beta phase characterized by brittleness and a tendency to fail under stress. It was found in this work that the bcc Ta coatings on steel can be obtained reliably by either of two methods: (1) depositing Ta on a submicron, stoichiometric TaN seed layer reactively sputtered on unheated steel and (2) depositing Ta directly on steel heated above a critical temperature. For argon sputtering gas this critical temperature was found to be 400°C at a pressure of 5 mtorr. With the heavier krypton gas, this critical temperature is reduced to 350°C. X-ray diffraction (XRD) was used to investigate the structure of tantalum and nitride films, and the composition of the nitride films was measured by nuclear reaction analyses (NRA), which were used to study in detail the enhancement of the bcc phase of Ta on steel. The scratch adhesion tests performed with a diamond hemispherical tip of radius 200 mum

  10. Characterization of high power impulse magnetron sputtering discharges

    NASA Astrophysics Data System (ADS)

    Hala, Matej

    Paper I: In the first paper, we present a new approach in the characterization of the high power pulsed magnetron sputtering (HiPIMS) discharge evolution—time- and species-resolved plasma imaging—employing a set of band-pass optical interference filters suitable for the isolation of the emission originating from different species populating the plasma. We demonstrate that the introduction of such filters can be used to distinguish different phases of the discharge, and to visualize numerous plasma effects including background gas excitations during the discharge ignition, gas shock waves, and expansion of metal-rich plasmas. In particular, the application of this technique is shown on the diagnostics of the 200 µs long non-reactive HiPIMS discharges using a Cr target. Paper II: In order to gain further information about the dynamics of reactive HiPIMS discharges, both fast plasma imaging and time- and space-resolved optical emission spectroscopy (OES) are used for a systematic investigation of the 200 µs long HiPIMS pulses operated in Ar, N2 and N 2/Ar mixtures and at various pressures. It is observed that the dense metal plasma created next to the target propagates in the reactor at a speed ranging from 0.7 to 3.5 km s-1, depending on the working gas composition and the pressure. In fact, it increases with higher N 2 concentration and with lower pressure. The visible form of the propagating plasma wave changes from a hemispherical shape in Ar to a drop-like shape extending far from the target with increasing N2 concentration, owing to the significant emission from molecular N2. Interestingly, the evidence of the target self-sputtering is found for all investigated conditions, including pure N2 atmosphere. Paper III: Here, we report on the time- and species-resolved plasma imaging analysis of the dynamics of the 200 µs long HiPIMS discharges above a Cr target ignited in pure O2. It is shown that the discharge emission is dominated solely by neutral and

  11. Ion beam sputter deposited diamond like films

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Rutledge, S. K.

    1982-01-01

    A single argon ion beam source was used to sputter deposit carbon films on fused silica, copper, and tantalum substrates under conditions of sputter deposition alone and sputter deposition combined with simultaneous argon ion bombardment. Simultaneously deposited and ion bombarded carbon films were prepared under conditions of carbon atom removal to arrival ratios of 0, 0.036, and 0.71. Deposition and etch rates were measured for films on fused silica substrates. Resulting characteristics of the deposited films are: electrical resistivity of densities of 2.1 gm/cu cm for sputter deposited films and 2.2 gm/cu cm for simultaneously sputter deposited and Ar ion bombarded films. For films approximately 1700 A thick deposited by either process and at 5550 A wavelength light the reflectance was 0.2, the absorptance was 0.7, the absorption coefficient was 67,000 cm to the -1 and the transmittance was 0.1.

  12. Confined ion beam sputtering device and method

    DOEpatents

    Sharp, Donald J.

    1988-01-01

    A hollow cylindrical target, lined internally with a sputter deposit material and open at both ends, surrounds a substrate on which sputtered deposition is to be obtained. An ion beam received through either one or both ends of the open cylindrical target is forced by a negative bias applied to the target to diverge so that ions impinge at acute angles at different points of the cylindrical target surface. The ion impingement results in a radially inward and downstream directed flux of sputter deposit particles that are received by the substrate. A positive bias applied to the substrate enhances divergence of the approaching ion beams to generate a higher sputtered deposition flux rate. Alternatively, a negative bias applied to the substrate induces the core portion of the ion beams to reach the substrate and provide ion polishing of the sputtered deposit thereon.

  13. Confined ion beam sputtering device and method

    DOEpatents

    Sharp, D.J.

    1986-03-25

    A hollow cylindrical target, lined internally with a sputter deposit material and open at both ends, surrounds a substrate on which sputtered deposition is to be obtained. An ion beam received through either one or both ends of the open cylindrical target is forced by a negative bias applied to the target to diverge so that ions impinge at acute angles at different points of the cylindrical target surface. The ion impingement results in a radially inward and downstream directed flux of sputter deposit particles that are received by the substrate. A positive bias applied to the substrate enhances divergence of the approaching ion beams to generate a higher sputtered deposition flux rate. Alternatively, a negative bias applied to the substrate induces the core portion of the ion beams to reach the substrate and provide ion polishing of the sputtered deposit thereon.

  14. Graphene: the ultimately thin sputtering shield

    NASA Astrophysics Data System (ADS)

    Herbig, Charlotte; Michely, Thomas

    2016-06-01

    Scanning tunneling microscopy methods are applied to investigate the potential of monolayer graphene as a sputtering shield for the underlying metal substrate. To visualize the effect, a bare and a graphene protected Ir(111) surface are irradiated with 500 eV Xe+, as well as 200 eV Xe+ and Ar+ ions, all at 1000 K. By quantitatively evaluating the sputtered material from the surface vacancy island area, we find a drastic decrease in metal sputtering for the graphene protected surface. It is demonstrated that efficient sputter protection relies on self-repair of the ion damage in graphene, which takes place efficiently in the temperature range of chemical vapor deposition growth. Based on the generality of the underlying principles of ion damage, graphene self-repair, and graphene growth, we speculate that efficient sputter protection is possible for a broad range of metals and alloys.

  15. ZnO Nanoparticles Treatment Induces Apoptosis by Increasing Intracellular ROS Levels in LTEP-a-2 Cells

    PubMed Central

    Wang, Caixia; Hu, Xiaoke; Gao, Yan; Ji, Yinglu

    2015-01-01

    Owing to the wide use of novel nanoparticles (NPs) such as zinc oxide (ZnO) in all aspects of life, toxicological research on ZnO NPs is receiving increasing attention in these days. In this study, the toxicity of ZnO NPs in a human pulmonary adenocarcinoma cell line LTEP-a-2 was tested in vitro. Log-phase cells were exposed to different levels of ZnO NPs for hours, followed by colorimetric cell viability assay using tetrazolium salt and cell survival rate assay using trypan blue dye. Cell morphological changes were observed by Giemsa staining and light microscopy. Apoptosis was detected by using fluorescence microscopy and caspase-3 activity assay. Both intracellular reactive oxygen species (ROS) and reduced glutathione (GSH) were examined by a microplate-reader method. Results showed that ZnO NPs (≥0.01 μg/mL) significantly inhibited proliferation (P < 0.05) and induced substantial apoptosis in LTEP-a-2 cells after 4 h of exposure. The intracellular ROS level rose up to 30–40% corresponding to significant depletion (approximately 70–80%) in GSH content in LTEP-a-2 cells (P < 0.05), suggesting that ZnO NPs induced apoptosis mainly through increased ROS production. This study elucidates the toxicological mechanism of ZnO NPs in human pulmonary adenocarcinoma cells and provides reference data for application of nanomaterials in the environment. PMID:26339612

  16. ZnO Nanoparticles Treatment Induces Apoptosis by Increasing Intracellular ROS Levels in LTEP-a-2 Cells.

    PubMed

    Wang, Caixia; Hu, Xiaoke; Gao, Yan; Ji, Yinglu

    2015-01-01

    Owing to the wide use of novel nanoparticles (NPs) such as zinc oxide (ZnO) in all aspects of life, toxicological research on ZnO NPs is receiving increasing attention in these days. In this study, the toxicity of ZnO NPs in a human pulmonary adenocarcinoma cell line LTEP-a-2 was tested in vitro. Log-phase cells were exposed to different levels of ZnO NPs for hours, followed by colorimetric cell viability assay using tetrazolium salt and cell survival rate assay using trypan blue dye. Cell morphological changes were observed by Giemsa staining and light microscopy. Apoptosis was detected by using fluorescence microscopy and caspase-3 activity assay. Both intracellular reactive oxygen species (ROS) and reduced glutathione (GSH) were examined by a microplate-reader method. Results showed that ZnO NPs (≥ 0.01 μg/mL) significantly inhibited proliferation (P < 0.05) and induced substantial apoptosis in LTEP-a-2 cells after 4 h of exposure. The intracellular ROS level rose up to 30-40% corresponding to significant depletion (approximately 70-80%) in GSH content in LTEP-a-2 cells (P < 0.05), suggesting that ZnO NPs induced apoptosis mainly through increased ROS production. This study elucidates the toxicological mechanism of ZnO NPs in human pulmonary adenocarcinoma cells and provides reference data for application of nanomaterials in the environment. PMID:26339612

  17. Eradication of Multi-drug Resistant Bacteria by Ni Doped ZnO Nanorods: Structural, Raman and optical characteristics

    NASA Astrophysics Data System (ADS)

    Jan, Tariq; Iqbal, Javed; Ismail, Muhammad; Mansoor, Qaisar; Mahmood, Arshad; Ahmad, Amaar

    2014-07-01

    In this paper, ZnO nanorods doped with varying amounts of Ni have been prepared by chemical co-precipitation technique. Structural investigations provide the evidence that Ni is successfully doped into ZnO host matrix without having any secondary phases. Scanning electron microscopy (SEM) images reveal the formation of rodlike structure of undoped ZnO with average length and diameter of 1 μm and 80 nm, respectively. Raman spectroscopy results show that the E1LO phonons mode band shifts to the higher values with Ni doping, which is attributed to large amount of crystal defects. Ni doping is also found to greatly influence the optical properties of ZnO nanorods. The influence of Ni doping on antibacterial characteristics of ZnO nanorods have been studied by measuring the growth curves of Escherichia coli (E. coli), Methicillin-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria in the presence of prepared nanorods. ZnO nanorods antibacterial potency is found to increase remarkably with Ni doping against S. aureus and P. aeruginosa microbials, which might possibly be due to the increase in reactive oxygen species (ROS) generation. Interestingly, it is observed that Ni doped ZnO nanorods completely eradicates these multi-drug resistant bacteria.

  18. A Comparison of ZnO and ZnO(-)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    1998-01-01

    Ab initio electronic structure calculations are performed to support and to help interpret the experimental work reported in the proceeding manuscript. The CCSD(T) approach, in conjunction with a large basis set, is used to compute spectroscopic constants for the X(exp 1)Epsilon(+) and (3)II states of ZnO and the X(exp 2)Epsilon(+) state of ZnO(-). The spectroscopic constants, including the electron affinity, are in good agreement with experiment. The ZnO EA is significantly larger than that of O, thus relative to the atomic ground state asymptotes, ZnO(-) has a larger D(sub o) than the (1)Epsilon(+) state, despite the fact that the extra electron goes into an antibonding orbital. The changes in spectroscopic constants can be understood in terms of the X(exp 1)Epsilon(+) formally dissociating to Zn (1)S + O (1)D while the (3)II and (2)Epsilon(+) states dissociate to Zn (1)S + O (3)P and Zn (1) and O(-) (2)P, respectively.

  19. Interfacial and structural properties of sputtered HfO{sub 2} layers

    SciTech Connect

    Aygun, G.; Yildiz, I.

    2009-07-01

    Magnetron sputtered HfO{sub 2} layers formed on a heated Si substrate were studied by spectroscopic ellipsometer (SE), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO{sub x} suboxide layer at the HfO{sub 2}/Si interface is unavoidable. The HfO{sub 2} thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O{sub 2}/Ar gas ratio during sputtering, sputtering time, and substrate temperature. XRD spectra show that the deposited film has (111) monoclinic phase of HfO{sub 2}, which is also supported by FTIR spectra. The atomic concentration and chemical environment of Si, Hf, and O have been measured as a function of depth starting from the surface of the sample by XPS technique. It shows that HfO{sub 2} layers of a few nanometers are formed at the top surface. Below this thin layer, Si-Si bonds are detected just before the Si suboxide layer, and then the Si substrate is reached during the depth profiling by XPS. It is clearly understood that the highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO{sub 2} to form HfO{sub 2}, leaving Si-Si bonds behind.

  20. Effect of depth of traps in ZnO polycrystalline thin films on ZnO-TFTs performance

    NASA Astrophysics Data System (ADS)

    Medina-Montes, Maria I.; Baldenegro-Perez, Leonardo A.; Sanchez-Zeferino, Raul; Rojas-Blanco, Lizeth; Becerril-Silva, Marcelino; Quevedo-Lopez, Manuel A.; Ramirez-Bon, Rafael

    2016-09-01

    ZnO thin films were processed by radio frequency magnetron sputtering at room temperature on p-Si/SiO2 substrates under pure argon (Ar:O2 = 100:0 vol.%) and argon-oxygen mixture (Ar:O2 = 99:1 vol.%) gas environment. Morphological, optical and electrical characteristics of the ZnO films are reported, and they show a clear relationship with the gas mixture employed for the sputtering process. Scanning Electron Microscopy revealed the formation of grains of 15.3 and 19.9 nm average sizes and thicknesses of 59 nm and 82 nm for films growth in pure argon and argon-oxygen, respectively. Photoluminescence measurements at room temperature showed the violet emission band (centered at 3 eV) which was only detected in the ZnO film grown under pure argon. From thermally stimulated conductivity measurements two traps with 0.27 and 0.14 eV activation energies were identified for films grown in pure argon and argon-oxygen mixture, respectively. The trap at 0.27 eV is associated with a level located below the conduction band edge and it is supported by the PL band centered at 3 eV. Both types of ZnO films were used as the active channel layer in thin film transistors with thermal SiO2 as gate dielectric. Field effect mobility, threshold voltage and current ratio were improved in the devices with ZnO channel deposited with the argon-oxygen mixture (99% Ar/1% O2 vol.). Threshold voltage decreased from 25 V to 15 V, field effect mobility and current ratio increased from 0.8 to 2.4 cm2/Vs and from 102 to 106, in that order.