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1.
The structural, electrical and optical properties of Na-doped CuInS 2 thin films grown by spray pyrolysis were studied. These films crystallized in the sphalerite structure of CuInS 2, and showed to contain traces of indium sulfide and CuIn 5S 8 as impurity phases. All films were In-rich and showed p-type conductivity. The film conductivity was strongly affected by Na-doping, which decreased from 10 −2 to 10 −5 S/cm by increasing the [Na]/[Cu] ratio from 0.005 to 0.03 in the spray solution. The band gap energy was observed to increase, from 1.4 to 1.45 eV, with increasing the [Na]/[Cu] ratio. Our results suggested that Na could be an effective acceptor impurity in sprayed CuInS 2. 相似文献
2.
We have investigated the stress behaviors and a mechanism of void formation in TiSi x films during annealing. TiSi x thin films were prepared by DC magnetron sputtering using a TiSi 2.1 target in the substrate temperature range of 200–500 °C. The as-deposited TiSi x films at low substrate temperature (<300 °C) have an amorphous structure with low stress of 1×10 8 dynes/cm 2. When the substrate temperature increases to 500 °C, the as-deposited TiSi x film has a mixture of C49 and C54 TiSi 2 phase with stress of 8×10 9 dynes/cm 2. No void was observed in the as-deposited TiSi x film. Amorphous TiSi x film transforms to C54 TiSi 2 phase with a random orientation of (311) and (040) after annealing at 750 °C. The C49 and C54 TiSi 2 mixture phase transforms to (040) preferred C54 TiSi 2 phase after annealing over 650 °C. By increasing substrate temperature, the transformation temperature for C54 TiSi 2 can be reduced, resulting in relieved stress of TiSi 2 film. The easy nucleation of the C54 phase was attributed to an avoidance of amorphous TiSi x phase. We found that amorphous TiSi x→C54 TiSi 2 transformation caused higher tensile stress of 2×10 10 dynes/cm 2, resulting in more voids in the films, than C49→C54 transformation. It was observed that void formation was increased with thermal treatment. The high tensile stress caused by volume decreases in the silicide must be relieved to retard voids and cracks during C54 TiSi 2 formation. 相似文献
3.
We report on the properties of (1− x)SrBi 2Ta 2O 9– xBi 3TaTiO 9 solid solution thin films for ferroelectric non-volatile memory applications. The solid solution thin films fabricated by modified metalorganic solution deposition technique showed much improved properties compared to SrBi 2Ta 2O 9. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 600°C and grain size was found to be considerably increased for the solid solution compositions. The film properties were found to be strongly dependent on the composition and annealing temperatures. The measured dielectric constant of the solid solution thin films was in the range 180–225 for films with 10–50% of Bi 3TaTiO 9 content in the solid solution. Ferroelectric properties of (1− x)SrBi 2Ta 2O 9– xBi 3TaTiO 9 thin films were significantly improved compared to SrBi 2Ta 2O 9. For example, the observed remanent polarization (2 Pr) and coercive field ( Ec) values for films with 0.7SrBi 2Ta 2O 9–0.3Bi 3TaTiO 9 composition, annealed at 650°C, were 12.4 μC/cm 2 and 80 kV/cm, respectively. The solid solution thin films showed less than 5% decay of the polarization charge after 10 10 switching cycles and good memory retention characteristics after about 10 6 s of memory retention. The improved microstructural and ferroelectric properties of (1− x)SrBi 2Ta 2O 9– xBi 3TaTiO 9 thin films compared to SrBi 2Ta 2O 9, especially at lower annealing temperatures, suggest their suitability for high density FRAM applications. 相似文献
4.
This paper embodies the first report on the electrochemical deposition of RuS 2 thin films. The as-deposited and heat-treated films (in argon atmosphere) were characterized by XRD, SEM and UV-VIS-NIR spectrophotometry. The polycrystalline deposits of RuS 2 obtained indicated a cubic structure with a lattice constant of 5.685 Å, an average grain size around 3 μm, and an absorption co-efficient of 5 × 10 4 cm −1. The optical band gap was found to be 1.48 eV. 相似文献
5.
We have made a study of the chemical composition, the electrical, the optical and the structural properties of polycrystalline CuInS 2 thin films prepared by spray pyrolysis to be used for thin film solar cells. These films were deposited starting from aqueous solutions with different chemical compositions ([Cu]/[In] and [S]/[Cu] ratios) and at different substrate temperatures. In all cases, the material is p-type with grains preferentially oriented in the (112) direction of the sphalerite structure. The electro-optical properties show a very strong dependence on the [Cu]/[In] ratio in the solution. Films with copper excess have smaller resistivity and better crystallinity than those which are stoichiometric or have indium excess. The results obtained in this work show the possibility of having CuInS 2 thin films with a wide range of resistivity, a fact that could be important for making solar cells based on this material. 相似文献
6.
Polycrystalline BaTiO 3 thin films having the perovskite structure were successfully produced on platinum coated silicon, bare silicon, and fused quartz substrate by the combination of the metallo-organic solution deposition technique and post-deposition rapid thermal annealing treatment. The films exhibited good structural, electrical, and optical properties. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) and metal-ferroelectric-semiconductor (MFS) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 255 and 0.025, respectively, and the remanent polarization and coercive field were 2.2 μC cm −2 and 25 kV cm −1, respectively. The resistivity was found to be in the range 10 10–10 12 Ω·cm, up to an applied electric field of 100 kV cm −1, for films annealed in the temperature range 550–700 °C. The films deposited on bare silicon substrates exhibited good film/substrate interface characteristics. The films deposited on fused quartz were highly transparent. An optical band gap of 3.5 eV and a refractive index of 2.05 (measured at 550 nm) was obtained for polycrystalline BaTiO 3 thin film on fused quartz substrate. The optical dispersion behavior of BaTiO 3 thin films was found to fit the Sellmeir dispersion formula well. 相似文献
7.
This work reports on the effect of post-deposition rapid thermal annealing on the structural and electrical properties of deposited TiB 2 thin films. The TiB 2 thin films, thicknesses from 9 to 450 nm, were deposited by e-beam evaporation on high resistivity and thermally oxidized silicon wafers. The resistivity of as-deposited films varied from 1820 μΩ cm for the thinnest film to 267 μΩ cm for thicknesses greater than 100 nm. In the thickness range from 100 to 450 nm, the resistivity of TiB 2 films has a constant value of 267 μΩ cm. A rapid thermal annealing (RTA) technique has been used to reduce the resistivity of deposited films. During vacuum annealing at 7 × 10−3 Pa, the film resistivity decreases from 267 μΩ cm at 200 °C to 16 μΩ cm at 1200 °C. Heating cycles during RTA were a sequence of 10 s. According to scanning tunneling microscopy analysis, the decrease in resistivity may be attributed to a grain growth through polycrystalline recrystallization, as well as to an increase in film density. The grain size and mean surface roughness of annealed films increase with annealing temperature. At the same time, the conductivity of the annealed samples increases linearly with grain size. The obtained results show that RTA technique has a great potential for low resistivity TiB2 formation. 相似文献
8.
AgInSn xS 2−x ( x = 0–0.2) polycrystalline thin films were prepared by the spray pyrolysis technique. The samples were deposited on glass substrates at temperatures of 375 and 400 °C from alcoholic solutions comprising silver acetate, indium chloride, thiourea and tin chloride. All deposited films crystallized in the chalcopyrite structure of AgInS 2. A p-type conductivity was detected in the Sn-doped samples deposited at 375 °C, otherwise they are n-type. The optical properties of AgInSn xS 2−x ( x < 0.2) resemble those of chalcopyrite AgInS 2. Low-temperature PL measurements revealed that Sn occupying an S-site could be the responsible defect for the p-type conductivity observed in AgInSn xS 2−x ( x < 2) thin films. 相似文献
9.
Bi 2Ti 2O 7 thin films have been grown directly on n-type GaAs (1 0 0) by the chemical solution decomposition technique. X-ray diffraction analysis shows that the Bi 2Ti 2O 7 thin films are polycrystalline. The optical properties of the thin films are investigated using infrared spectroscopic ellipsometry (3.0–12.5 μm). By fitting the measured ellipsometric parameter (Ψ and Δ) data with a three-phase model (air/Bi 2Ti 2O 7/GaAs), and Lorentz–Drude dispersion relation, the optical constants and thickness of the thin films have been obtained simultaneously. The refractive index and extinction coefficient increase with increasing wavelength. The fitted plasma frequency ω p is 1.64×10 14 Hz, and the electron collision frequency γ is 1.05×10 14 Hz, and it states that the electron average scattering time is 0.95×10 −14 s. The absorption coefficient variation with respect to increasing wavelength has been obtained. 相似文献
10.
A XeCl excimer laser ( λ=308 nm) has been used to anneal Indium Tin Oxide (ITO) films deposited at 25 °C using DC magnetron sputtering. With increasing laser fluence, the film crystallinity was improved while retaining the as-deposited 111 texture. As a result of laser irradiation, the sheet resistance of 100 nm ITO films decreased from 191 Ω/□ (1.91×10 −3 Ω cm) to 25 Ω/□ (2.5×10 −4 Ω cm), while the optical transmittance in the visible range increased from 70% to more than 85%. Surface roughness and etching properties were also significantly improved following laser annealing. 相似文献
11.
High-quality and well-reproducible PbSnS 3 thin films have been prepared by a simple and inexpensive chemical-bath deposition method from an aqueous medium, using thioacetamide as a sulphide ion source. X-ray diffraction analysis of the deposited films revealed that the as-deposited films were amorphous, however, an amorphous-to-crystalline phase transition was observed as the result of thermal annealing at 425 K for 1 h. The X-ray structure analysis of the collected powder from the bath annealed at 425 K for 1.5 h revealed an orthorhombic phase. Analysis of the optical absorption data of crystalline PbSnS3 films revealed that both direct and indirect optical transitions exist in the photon energy range 1.24–2.48 eV with optical band gaps of 1.68 and 1.42 eV, respectively. However, a forbidden direct optical transition with a band gap value of 1.038 eV dominates at low energy (<1.24 eV). The refractive index changes from 3.38 to 2.16 in the range 500–1300 nm. The high frequency dielectric constant and the carrier concentration to the effective mass ratio calculated from the refractive index analysis were found to be 4.79 and 2.3×1020 cm−3, respectively. The temperature dependence of the electrical resistivity of the deposited films follows the semiconductor behaviour with extrinsic and intrinsic conduction. The determined activation energies range are 0.35–0.42 and 0.76–85 eV, respectively. 相似文献
12.
Semiconducting polycrystalline CdSe thin films were prepared on glass substrates by chemical bath at 65 °C. As-deposited films grew in the metastable cubic sphalerite (S) crystalline structure with good stoichiometry. Upon thermal annealing (TA) in Ar+Se 2 atmosphere at different temperatures in the range 200–500 °C, the gradual phase transformation from cubic modification to hexagonal wurtzite (W) stable phase could be observed. From optical absorption measurements the fundamental energy band gap ( Eg) and the second electronic transition ( Eg+Δ Eg) were calculated for as-deposited and thermal annealed films. For TA350 °C, S-phase dominates the crystalline structure and only the spin orbit (Δ Eso) contribution to Δ Eg is present. Above 350 °C, the W-phase dominates and the energy splitting (Δ Ecf), owed to crystal field contribution and originated by the loss of lattice symmetry, should be added to Δ Eso in order to complete Δ Eg in the W-phase. The values Δ Eso=0.389±0.011 eV and Δ Ecf=0.048±0.018 eV were found from our analysis, and Tc=350 °C was here defined as the critical point of the phase transformation. 相似文献
13.
HfO 2 thin films with columnar microstructure were deposited directly on ZnS substrates by electron beam evaporation process. SiO 2 thin films, deposited by reactive magnetron sputtering, were used as buffer layers, HfO 2 thin films of granular microstructure were obtained on SiO 2 interlayer by this process. X-ray diffraction patterns demonstrate that the as-deposited HfO 2 films are in an amorphous-like state with small amount of crystalline phase while the HfO 2 films annealed at 450 °C in O 2 for 30 min and in Ar for 150 min underwent a phase transformation from amorphous-like to monoclinic phase. Antireflection effect in certain infrared wave band, such as 3–6 μm, 4–12 μm, 4–8 μm and 3–10 μm, can be observed, which was dependent on the thickness of thin films. The cross-sectional images of HfO 2 films, obtained by field emission scanning electron microscopy, revealed that there was no distinct morphological change upon annealing. 相似文献
14.
Vanadium oxides condensed films are prepared on glass substrates, using spray pyrolysis (SP) technique.The effects of substrate temperature, vanadium concentration in initial solution and the solution spray rate on the nano-structural, electrical, and optical properties of deposited films were investigated. Characterizations of the samples were performed using X-ray diffraction (XRD),scanning electron microscopy (SEM), and UV-Vis spectroscopy methods. The type and concentration of the charge carriers were determined and measured by Hall effect experiment. XRD patterns showed that the prepared films had polycrystalline structure, mostly tetragonal β-V 2O 5 and V 4O 9 phases with the preferred orientation along (200) direction. The Hall effect experiment revealed that all samples were n-type, except the ones deposited at substrate temperatures Tsub = 300 ℃ and Tsub = 450 ℃, vanadium concentration 0.1 mol/L and solution spray rate 10 mL/min.The charge carrier concentrations obtained were in the range 10 16–10 18 cm -3. The lowest sheet resistance ( Rs) was obtained for the samples prepared at T sub = 450 ℃, vanadium concentration 0.05 mol/L and solution spray rate 10 mL/min. It was also found that the optical transparency of the samples changed from 20% to 75% and the optical band gap of the samples was from 2.22 eV to 2.58 eV, depending on the deposition conditions. 相似文献
15.
采用脉冲激光沉积法制备了斜方相Sc 2W 3O 12薄膜。利用X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对Sc 2W 3O 12靶材和Sc 2W 3O 12薄膜组分、表面形貌和靶材断面形貌进行表征, 研究衬底温度与氧分压对薄膜制备的影响。采用变温XRD和热机械分析仪(TMA)分析了Sc 2W 3O 12陶瓷靶材和薄膜的负热膨胀特性。实验结果表明: 经1000℃烧结6 h得到结构致密的斜方相Sc 2W 3O 12陶瓷靶材, 其在室温到600℃的温度范围内平均热膨胀系数为-5.28×10 -6 K -1。在室温到500℃衬底温度范围内脉冲激光沉积制备的Sc 2W 3O 12薄膜均为非晶态, 随着衬底温度的升高, 薄膜表面光滑程度提高; 随着沉积氧压强增大, 表面平整性变差。非晶膜经1000℃退火处理7 min后得到斜方相Sc 2W 3O 12多晶薄膜, 在室温到600℃温度区间内, Sc 2W 3O 12薄膜的平均热膨胀系数为-7.17×10 -6 K -1。 相似文献
16.
Thin films of CuGaTe 2 with thicknesses in the range, 0.1–1.0 μm were deposited on Corning 7059 glass substrates by flash evaporation. The substrate temperatures, Ts, were maintained in the range 373–623 K. The transmittance of the films was recorded in the wavelength range 900–2500 nm. The dependence of the optical band gap, Eg, on substrate temperature showed that the value of Eg varied from 1.21 eV to 1.24 eV. The variation of refractive index and extinction coefficient with photon energy was studied from which the material properties such as the limiting value of dielectric constant, ε ∞, plasma frequency, ω p, and hole effective mass, mh*, were evaluated as ε ∞ = 7.59, ω p = 1.47 × 10 14 and mh* = 1.25 m0. 相似文献
17.
High-quality LB multilayers have been prepared from the Lu(III) sandwich complex of 2,3,9,10,16,17,23,24-octa ( n-butoxy)phthalocyanine (LuPc 2(OBu) 16). Surface pressure-area isotherms were characterized and indicate that a stable monolayer is formed corresponding to an area per molecule of 2.4 nm 2 at 30 mN m −1. The LB films were highly birefringent, and polarized spectra gave dichroic ratios of 3.3 for the 670 nm absorption band and between 0.5 and 2.8 for infrared absorptions. The results indicate that the phthalocyanine rings were highly oriented perpendicular to the dipping direction but somewhat tilted from the substrate normal. The order was shown to be absent when (i) unsubstituted LuPc 2 was used for LB films, or (ii) the horizontal lifting method of film deposition was used, or (iii) the surface pressure was increased to 50 mN m −1, causing a molecular rearrangement. The ordering was improved at 100 °C and finally lost at 280 °C by annealing on a hot stage. The d.c. electrical conductivity of LB films of LuPc 2(OBu) 16 was low (σ ≈ 2 × 10 −7 Ω −1 m −1), in contrast with unsubstituted LuPc 2 (σ ≈ 10 −1 Ω −1 m −1) and showed no evidence for anisotropy. The findings are in broad agreement with related studies and illustrate some of the many factors involved in improving the structure of phthalocyanine LB films for possible applications. 相似文献
18.
As the first stage for thin film preparation of copper indium disulfide (CuInS 2), an electrodeposition technique of thin films in the Cu---S system was investigated from a new viewpoint. Deposition was carried out potentiostatically on a Ti substrate from acidic aqueous solution containing CuSO 4 and Na 2S 2O 3. Tartaric acid was found to be effective as a buffer for stabilizing the hydrogen ion concentration. Thin films of Cu 2S were obtained at −0.7 V vs. Ag/AgCl with good reproducibility from a solution containing 10 mM CuSO 4, 400 mM Na 2S 2O 3 and 100 mM tartaric acid. Scanning electron microscopy and energy dispersive X-ray analyses revealed that the film deposited had a crack-free surface and uniform stoichiometry of Cu 2S. Film thickness was estimated to be 0.6−0.8×10 −6m after 3600 s deposition. The mechanism of Cu 2S formation was supposed to be that S 2O 32− ion reduces Cu(II) ion to make complex with Cu(I) ion. Probably it is this complex that contributes to the Cu 2S formation. 相似文献
19.
(Ti 1−xAl x)N films were prepared on a Si wafer at 700°C from toluene solution of alkoxides (titanium tetraetoxide and aluminum tri-butoxide) in an Ar/N 2/H 2 plasma by the thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrical resistivity, and Vickers micro-hardness. Single phase TiN formed at an Al atomic fraction of 0–0.2, with a mixed TiN and AlN phase occurring up to 0.6 and single phase AlN forming above 0.8. The films had relatively sooth surfaces, 0.4 μm thick at an Al atomic fraction of 0.2, and thickened with increasing Al fraction. The atomic concentration of Ti, Al, N, O, and C determined from their respective XPS areas showed that the Ti and Al contents of the films changes with the solution composition in a complementary way. The impurities were about 10 at.% oxygen and carbon. The electrical resistivity was almost unchanged from the value of 10 3 μΩ cm at 0–0.6 Al but then suddenly increased to 10 4 μΩ cm at higher Al contents. The hardness showed a synergic maximum of about 20 GPa at an Al fraction of 0.6–0.8. 相似文献
20.
Physical and electrical properties of hafnium silicon oxynitride (HfSi xO yN z) dielectric films prepared by UV ozone oxidation of hafnium silicon nitride (HfSiN) followed by annealing to 450 °C are reported. Interfacial layer growth was minimized through room temperature deposition and subsequent ultraviolet/ozone oxidation. The capacitance–voltage ( C– V) and current–voltage ( I– V) characteristics of the as-deposited and annealed HfSi xO yN z are presented. These 4 nm thick films have a dielectric constant of 8–9 with 12 at.% Hf composition, with a leakage current density of 3×10 −5 A/cm 2 at Vfb+1 V. The films have a breakdown field strength >10 MV/cm. 相似文献
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