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1.
Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy 总被引:1,自引:0,他引:1
P. Bala Srinivasan J. Liang C. Blawert M. Störmer W. Dietzel 《Applied Surface Science》2009,255(7):4212-4218
Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15 mA cm−2, 75 mA cm−2, and 150 mA cm−2 and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15 min treated coatings produced at higher current density levels were thicker, they showed poor corrosion resistance when compared to that of the coatings obtained at 15 mA cm−2. Short-term treatments (2 min and 5 min) at 150 mA cm−2 yielded coatings of thickness and corrosion resistance comparable to that of the low current density coatings. The superior corrosion resistance of the low thickness coatings is attributed to the better pore morphology and compactness of the layer. 相似文献
2.
Deposition of sputtered iridium oxide—Influence of oxygen flow in the reactor on the film properties
Thin films of iridium oxide have been deposited by reactive magnetron sputtering. The influence of oxygen partial pressure in the sputtering plasma on the composition, surface structure and morphology of the films has been studied by XRD, SEM and AFM analysis. An optimal combination of sputtering parameters yields stable microporous amorphous films with highly extended fractal surface. The electrochemical properties of these films have been investigated in view of their application as catalysts for water splitting, using the electrochemical techniques of cyclovoltammetry, electrochemical impedance spectroscopy, and steady state polarization. The SIROFs have shown an excellent electrochemical reversibility and a high catalytic activity toward the oxygen evolution reaction in 0.5 M H2SO4. A current density of 150 mA cm−2 at potential of 1.7 V (versus Ag/AgCl) has been obtained at catalyst load of only 100 μg cm−2. These results combined with the established long-term mechanical stability of the sputtered iridium oxide films (SIROFs) proved the advantages of the reactive magnetron sputtering as simple and reliable method for preparation of catalysts with precisely controlled composition, loading, and surface characteristics. 相似文献
3.
ZnO films with different morphologies were deposited on the ITO-coated glass substrate from zinc nitrate aqueous solution at 65 °C by a seed-layer assisted electrochemical deposition route. The seed layers were pre-deposited galvanostatically at different current densities (isl) ranging from −1.30 to −3.0 mA/cm2, and the subsequent ZnO films had been done using the potentiostatic technique at the cathode potential of −1.0 V. Densities of nucleation centers in the seed layers varied with increasing the current density, and the ZnO films on them showed variable morphologies and optical properties. The uniform and compact nanocrystalline ZnO film with (0 0 2) preferential orientation was obtained on seed layer that was deposited under the current density (isl) of −1.68 mA/cm2, which exhibited good optical performances. 相似文献
4.
Physical and electrical properties of sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate are investigated. The as-deposited films and interfacial layer formation have been analyzed by using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). It is found that directly deposited Y2O3 on n-GaAs exhibits excellent electrical properties with low frequency dispersion (<5%), hysteresis voltage (0.24 V), and interface trap density (3 × 1012 eV−1 cm−2). The results show that the deposition of Y2O3 on n-GaAs can be an effective way to improve the interface quality by the suppression on native oxides formation, especially arsenic oxide which causes Fermi level pinning at high-k/GaAs interface. The Al/Y2O3/n-GaAs stack with an equivalent oxide thickness (EOT) of 2.1 nm shows a leakage current density of 3.6 × 10−6 A cm−2 at a VFB of 1 V. While the low-field leakage current conduction mechanism has been found to be dominated by the Schottky emission, Poole-Frenkel emission takes over at high electric fields. The energy band alignment of Y2O3 films on n-GaAs substrate is extracted from detailed XPS measurements. The valence and conduction band offsets at Y2O3/n-GaAs interfaces are found to be 2.14 and 2.21 eV, respectively. 相似文献
5.
ZnO films prepared from the ZnO target containing 2% AlN are transparent irrespective of radio frequency (RF) power. The obtained ZnO films have the carrier density of 3.8 × 1020 cm−3 or less and the low mobility of 5.3-7.8 cm2/(V s). In the case of 5% AlN target, ZnO films prepared at 40, 60 and 80 W are transparent, whereas ZnO films prepared at 100 and 120 W are colored. As RF power increases from 40 to 120 W, the carrier density increases straightforwardly up to 5.5 × 1020 cm−3 at 100 W and is oppositely reduced to 3.2 × 1020 cm−3 at 120 W. In the case of 10% AlN target, ZnO films prepared at 60 W or more are colored, and have the carrier density of 4 × 1020 cm−3 or less. The N-concentration in these colored films is estimated to be 1% or less. The Al-concentration in the ZnO films prepared from the 5 and 10% AlN targets is higher than 2%. The carrier density of the ZnO films containing Al and N atoms is nearly equal to that of ZnO films doped with Al atoms alone. There is no evidence in supporting the enhancement of the carrier density via the formation of N-AlxZn4−x clusters (4 ≥ x ≥ 2). 相似文献
6.
Silicon oxynitride thin films were deposited by reactive r.f. sputtering from a silicon target. Different Ar:O2:N2 gas atmospheres were used at fixed power density (3.18 W cm−2) and pressure (0.4 Pa) to obtain various film composition. Pt-SiOxNy-Pt sandwich type structure was realised for electrical property investigations. The C-V measurements showed the absence of a Schottky barrier and thus confirmed that Pt electrode provides an ohmic contact. The evolution of the current density showed a decrease of the film conductivity when the oxygen concentration in the films increases. The various layer composition leads to two different conduction mechanisms which were identified as space charge limited current (SCLC) and Poole-Frenkel effect. Finally, the structural defects of the films were studied by EPR analysis and the spin densities were correlated to both the composition and the electrical behaviour of the films. 相似文献
7.
Porous Ni-YSZ (YSZ—yttria-stabilized zirconia) films were fabricated by reactive co-sputtering of a Ni and a Zr-Y target, followed by sequentially annealing in air at 900 °C and in vacuum at 800 °C. The Ni-YSZ films comprised small grains and pores that were tens of nanometers in size. The porous Ni-YSZ films were used as an anode on one side of a YSZ electrolyte disc and a La0.7Sr0.3MnO3 thick film was used as a cathode on the other side of the disc to form solid oxide fuel cells (SOFCs). The voltage-current curves of the SOFCs with single- and a triple-layered porous anodes were measured in a single-chamber configuration, in a mixture of CH4 and air (CH4:O2 volume ratio=2:1). The maximum power density of the SOFC using the single-layered porous Ni-YSZ thin films as the anode was 0.38 mW cm−2, which was lower than that of 0.76 mW cm−2, obtained using a screen-printed Ni-YSZ thick anode. The maximum power density of the SOFC with a thin anode was increased, but varied between 0.6 and 1.14 mW cm−2 when a triple-layered porous Ni-YSZ anode was used. 相似文献
8.
S. Hussain 《Applied Surface Science》2007,253(7):3649-3657
Diamond-like carbon films containing Ag and Cu in nanocrystalline form were deposited onto SnO2-coated glass substrates by electrochemical technique. Relative amount of silver and copper to be incorporated in the DLC matrix was tailored by varying the amount of silver and copper containing salts in the electrolyte. Current density was adjusted to obtain films with different crystallite size while the volume fraction of the metal nanocrystallites was altered by varying the dilution of the solution containing the salts. Raman studies indicated the presence of two peaks located at ∼1350 cm−1 (D-line) and 1566 cm−1 (G-line) for all the films and the relative intensities of these peaks changed with the amount of metal incorporation in it. The FTIR spectra were seen to be dominated by a peak at 975 cm−1 for C-H out of plane deformation modes along with peaks for C-H bending, C-H stretching and C-C stretching modes at 858, 1113 and 1189 cm−1, respectively. The optical absorption spectra showed a single plasmon band instead of two characteristic bands for Ag and Cu. We ascribe this to nanophase limited interfacial alloying at the Ag-Cu interface. The experimental observation was analyzed in the light of Mie theory. 相似文献
9.
Hirokazu KitauraAkitoshi Hayashi Kiyoharu TadanagaMasahiro Tatsumisago 《Solid State Ionics》2011,192(1):304-307
To improve the electrochemical performance of an all-solid-state In/80Li2S⋅20P2S5 (electrolyte)/LiMn2O4 cell, a lithium-titanate thin film was used to coat LiMn2O4. The interfacial resistance between LiMn2O4 and the electrolyte (measured after initial charging) decreased when the LiMn2O4 particles were coated with lithium-titanate. A cell with lithium-titanate-coated LiMn2O4 had a higher capacity than a cell with noncoated LiMn2O4 for current densities in the range 0.064 to 2.6 mA cm− 2. Additionally, a cell with coated LiMn2O4 retained 96% of the 10th-cycle reversible capacity at a current density of 0.064 mA cm− 2 after 50 cycles. 相似文献
10.
This paper attempts to realize unpinned high-k insulator-semiconductor interfaces on air-exposed GaAs and In0.53Ga0.47As by using the Si interface control layer (Si ICL). Al2O3 was deposited by ex situ atomic layer deposition (ALD) as the high-k insulator. By applying an optimal chemical treatment using HF acid combined with subsequent thermal cleaning below 500 °C in UHV, interface bonding configurations similar to those by in situ UHV process were achieved both for GaAs and InGaAs after MBE growth of the Si ICL with no trace of residual native oxide components. As compared with the MIS structures without Si ICL, insertion of Si ICL improved the electrical interface quality, a great deal both for GaAs and InGaAs, reducing frequency dispersion of capacitance, hysteresis effects and interface state density (Dit). A minimum value of Dit of 2 × 1011 eV−1 cm−2 was achieved both for GaAs and InGaAs. However, the range of bias-induced surface potential excursion within the band gap was different, making formation of electron layer by surface inversion possible in InGaAs, but not possible in GaAs. The difference was explained by the disorder induced gap state (DIGS) model. 相似文献
11.
Diamond-like carbon films (DLC) were deposited on titanium substrates in acetonitrile and N,N-dimethyl formamide (DMF) liquids by the liquid-phase electrodeposition technique at ambient pressure and temperature. The applied voltage between the electrodes was high (1200 V) due to the use of resistive organic liquids. The surface morphology was examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Corrosion performance of the coatings was investigated by potentiodynamic polararization tests in phosphate buffer saline solution. Raman spectroscopy analysis of the films revealed two broad bands at approximately 1360 cm−1 and 1580 cm−1, related to D and G-band of DLC, respectively. The coated Ti was tested in a ball-on-plate type wear test machine with Al2O3 balls. The films presented a low friction coefficient (about 0.1), and the films deposited from DMF presented the best wear resistance. 相似文献
12.
Magnetotransport properties of magnetite thin films deposited on gallium arsenide and sapphire substrates at growth temperatures between 473 and 673 K are presented. The films were grown by UV pulsed laser ablation in reactive atmospheres of O2 and Ar, at working pressure of 8 × 10−2 Pa. Film stoichiometry was determined in the range from Fe2.95O4 to Fe2.97O4. Randomly oriented polycrystalline thin films were grown on GaAs(1 0 0) while for the Al2O3(0 0 0 1) substrates the films developed a (1 1 1) preferred orientation. Interfacial Fe3+ diffusion was found for both substrates affecting the magnetic behaviour. The temperature dependence of the resistance and magnetoresistance of the films were measured for fields up to 6 T. Negative magnetoresistance values of ∼5% at room temperature and ∼10% at 90 K were obtained for the as-deposited magnetite films either on GaAs(1 0 0) or Al2O3(0 0 0 1). 相似文献
13.
Yousuke Fukaya Takashi Yanase Yasushi Kubota Shigeki Imai Taketoshi Matsumoto Hikaru Kobayashi 《Applied Surface Science》2010,256(18):5610-5613
We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5-10 nm) SiO2/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 °C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO2 layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 × 1022 atoms/cm2, and it increases by POA at 400 °C in wet-oxygen (2.32 × 1022 atoms/cm2) or dry-oxygen (2.30 × 1022 atoms/cm2). The leakage current density is considerably low (e.g., 10−5 A/cm2 at 8 MV/cm) and it is greatly decreased (10−8 A/cm2 at 8 MV/cm) by POA at 400 °C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO2 layer, and decreases the density of oxide fixed positive charges. 相似文献
14.
Mehmet Ali Ebeo?lu 《Physica B: Condensed Matter》2008,403(1):61-66
Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density Nss with and without taking into account the series resistance Rs. While the interface state density calculated without taking into account Rs has increased exponentially with bias from 2.2×1012 cm−2 eV−1 in (Ec−0.48) eV to 3.85×1012 cm−2 eV−1 in (Ec−0.32) eV of n-GaAs, the Nss obtained taking into account the series resistance has remained constant with a value of 2.2×1012 cm−2 eV−1 in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer. 相似文献
15.
M.E. Sánchez Vergara A. Ortiz Rebollo M. Rivera 《Journal of Physics and Chemistry of Solids》2008,69(1):1-7
Semiconductor-like thin films were grown using metallic phthalocyanines (MPc) (M=Fe, Pb, Co) and 1,8 dihydroxiantraquinone as initial compounds. The morphology of the deposited films was studied by using scanning electron microscopy and atomic force microscopy. The powder and thin-film samples of the synthesized materials, deposited by vacuum thermal evaporation, showed the same intra-molecular bonds as in IR spectroscopy studies, which suggests that the evaporation process does not alter these bonds. The optical band gap values of C60H28N8O8Fe, C60H28N8O8Pb and C60H28N8O8Co calculated from the absorption coefficient were found to be 1.60, 1.89 and 1.75 eV, respectively, arising from non-direct transitions. The effect of temperature on conductivity was also measured in these samples. It was found that the temperature-dependent electric current in all cases showed a semiconductor behavior with conductivities in the order of 10−6 Ω−1 cm−1 where the highest value corresponded to the cobalt material. The linear dependence observed in the films implies only one type of conduction mechanism in all cases, with mean activation energies of the order of 1.55, 1.77 and 1.50 eV for iron, lead and cobalt-based thin films, respectively. 相似文献
16.
Chemical composition of Cu/Ge layers deposited on a 1 μm thick n-type GaAs epitaxial layer (doped with Te to a concentration of 5 × 1018 cm−3) and its interface were examined ex situ by XPS combined with Ar+ sputtering. These measurements indicate a diffusion of Cu and Ge from the Cu/Ge layer towards GaAs and, also, an out-diffusion of Ga and As from the GaAs layer to the metallic films. The Auger parameter corrected Auger spectra and XPS spectra show only Cu and Ge metals in the in the Cu/Ge layer and in the interface. 相似文献
17.
Surface textured ZnO:Al thin films by pulsed DC magnetron sputtering for thin film solar cells applications 总被引:1,自引:0,他引:1
Transparent conducting thin films of ZnO:Al (Al-doped ZnO, AZO) were prepared via pulsed DC magnetron sputtering with good transparency and relatively lower resistivity. The AZO films with 800 nm in thickness were deposited on soda-lime glass substrates keeping at 473 K under 0.4 Pa working pressure, 150 W power, 100 μs duty time, 5 μs pulse reverse time, 10 kHz pulse frequency and 95% duty cycle. The as-deposited AZO thin films has resistivity of 6.39 × 10−4 Ω cm measured at room temperature with average visible optical transmittance, Ttotal of 81.9% under which the carrier concentration and mobility were 1.95 × 1021 cm−3 and 5.02 cm2 V−1 s−1, respectively. The films were further etched in different aqueous solutions, 0.5% HCl, 5% oxalic acid, 33% KOH, to conform light scattering properties. The resultant films etched in 0.5% HCl solution for 30 s exhibited high Ttotal = 78.4% with haze value, HT = 0.1 and good electrical properties, ρ = 8.5 × 10−4 Ω cm while those etched in 5% oxalic acid for 150 s had desirable HT = 0.2 and relatively low electrical resistivity, ρ = 7.9 × 10−4 Ω cm. However, the visible transmittance, Ttotal was declined to 72.1%. 相似文献
18.
Jaskiran Kaur Surinder SinghRajesh Kumar Dinakar KanjilalShiv Kumar Chakarvarti 《Superlattices and Microstructures》2011,50(6):713-721
In this paper electrical and field emission properties of the randomly distributed copper, iron and nickel nanowires on GaAs substrate are presented. Semiconducting (GaAs) wafers, spin coated with thin polymeric films were irradiated with 50 MeV Li (+3) ions at a fluence of 8 × 107 ions/cm2, followed by UV irradiation and chemically etching in aqueous NaOH (6N, at room temperature). The wires have been deposited potentiostatically into the pores of the track-etch polycarbonate membrane spin coated onto the GaAs substrate. The size, shape and morphology of the deposits are strongly dependent of the preparation conditions such as deposition potential, current density, electrolyte and etching conditions. Later, morphological, electrical and field emission properties of the so deposited nano-/micro-structures were studied. 相似文献
19.
Metallo-organic decomposition derived dielectric thin films of calcium zirconate doped with various concentrations of strontium ((Ca, Sr)ZrO3) were prepared on Pt coated silicon substrate. Mainly in this paper, we present the investigations of their structural developments and present their electric and dielectric properties as well. The structural developments show that the CaZrO3 film has amorphous structure with carbonate existing when annealed at 600 °C, while annealed at 650 °C and above, the carbonate is decomposed and those films crystallize into perovskite phase without preferred orientation. In addition, the prepared (Ca, Sr)ZrO3 films with their Zr-O bonds affected by strontium doping are homogenous and stable as solid solutions in any concentration of strontium and all Bragg diffraction characteristics for the films shift downward with the increase in the concentration of strontium. Moreover, the electric properties show that the (Ca, Sr)ZrO3 films have very low leakage current density and high breakdown strength; typically, the CaZrO3 film annealed at 650 °C has the leakage current density approximately 9.5 × 10−8 A cm−2 in the field strength of 2.6 MV cm−1. Furthermore, the dielectric properties show that their dielectric constants are higher than 12.8 with very little dispersion in the frequency range from 100 Hz to 1 MHz and are independent of applied dc bias as well. The dielectric properties, in combination with the electric properties, make the materials promising candidates for high-voltage and high-reliability capacitor applications. 相似文献
20.
Pulsed laser deposited ZnS bare and SnO2 coated ultra thin films were subjected to prolonged electron beam bombardment with 2 keV energy and a steady 44 mA/cm2 current density, in 1 × 10−6 Torr O2 pressure backfilled from a base pressure of 3 × 10−9 Torr at room temperature. Auger electron spectroscopy (AES) was used to monitor changes of the surface chemical composition of both the bare and coated phosphor films during electron bombardment. Degradation was manifested by the decrease of sulphur and accumulation of oxygen on the surface of the bare phosphor. However, with the SnO2 coating this phenomenon was delayed until the protective SnO2 was depleted on the surface through dissociation and reduction. 相似文献