Structural relaxation of Al-W amorphous thin films

The pronounced variation of the electrical resistivity of the amorphous Al-W thin films observed during initial heating above room temperature was examined. Both isochronal and isothermal treatments were performed in order to investigate the effects of the film composition, substrate material, and substrate temperature, on the magnitude of the relaxation phenomena. Regarding the isochronal heating, it was observed that the relaxation effects decreased with an increase of the heating rate, and decreased with the aluminum content in the film. The Al₇₈W₂₂ amorphous thin films were subjected to isothermal annealing for 6 h at a temperature of 515 °C. The effects of the substrate material (alumina ceramic, glass and sapphire), and the deposition temperature (LNT, RT, 200 and 400 °C) were examined. The relaxation decreased in a sequence of: alumina ceramic-glass-sapphire substrates, as well as with an increase of the substrate temperature. An assumed dominant role of the aluminum in the effects observed, was tested by the corresponding investigation of Al-Ti and Cu-Ti amorphous thin films.     

A comparison of the crystallization behavior of liquid-quenched and vapor-quenched amorphous Cu60Ti40

The crystallization behavior of two Cu₆₀Ti₄₀ amorphous alloys, one prepared by a vapor-quench (VQ) process and one by a liquid-quench (LQ) process, has been studied using differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. Microstructural studies show that the two alloys have the same transformation sequence under similar annealing conditions. However DSC measurements of the crystallization temperature during isochronal annealing and of the incubation time for crystallization during isothermal annealing show that the LQ alloy is more thermally stable and therefore more structurally relaxed. TEM analysis of the partially annealed microstructures gives some insight into the mode of crystal nucleation and growth as a function of temperature. During isothermal annealing significant differences are observed for the two alloys in the shape and orientation of the crystals and in the crystal structure formed. Whereas the VQ alloy transforms polymorphicaly into the intermetallic Cu₃Ti₂, the LQ alloy forms the Ti-rich phase, Cu₄Ti₃. The two phases are closely related in structure and composition. The differences observed for the two alloys are discussed in terms of greater structural relaxation and short range order in the LQ alloy resulting from the mode of synthesis.     

Nanocrystalline transparent SnO2‐ZnO films fabricated at lower substrate temperature using a low‐cost and simplified spray technique

Nanocrystalline and transparent conducting SnO₂‐ ZnO films were fabricated by employing an inexpensive, simplified spray technique using a perfume atomizer at relatively low substrate temperature (360±5 °C) compared with conventional spray method. The structural studies reveal that the SnO₂‐ZnO films are polycrystalline in nature with preferential orientation along the (101) plane. The dislocation density is very low (1.48×10¹⁵lines/m²), indicating the good crystallinity of the films. The crystallite size of the films was found to be in the range of 26–34 nm. The optical transmittance in the visible range and the optical band gap are 85% and 3.6 eV respectively. The sheet resistance increases from 8.74 kΩ/□ to 32.4 kΩ/□ as the zinc concentration increases from 0 to 40 at.%. The films were found to have desirable figure of merit (1.63×10^–2 (Ω/□)^–1), low temperature coefficient of resistance (–1.191/K) and good thermal stability. This simplified spray technique may be considered as a promising alternative to conventional spray for the massive production of economic SnO₂ ‐ ZnO films for solar cells, sensors and opto‐electronic applications. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

退火温度对CuNps@ZnO纳米复合薄膜结构与光学性能的影响

使用磁控溅射结合惰性气体冷凝的方法制备了Cu纳米粒子,通过将Cu纳米粒子沉积与ZnO离子束溅射原位复合的方法制得了CuNps@ZnO纳米复合薄膜,并研究了退火温度对CuNps@ZnO纳米粒子复合薄膜的结构和光学性能的影响.通过对样品的表征发现所得产物中存在着低温条件下难以形成的立方相、岩盐结构的ZnO.并且,样品的微观形貌、结晶性和光学性能随着退火温度的变化而发生显著地变化.     

Effect of annealing on the structural,electrical and optical properties of nanostructured TiO2 thin films

Nanostructured titanium dioxide thin films were prepared using reactive pulsed laser ablation technique. Effects of annealing on the structural, morphological, electrical and optical properties are discussed. The structural, electrical and optical properties of TiO₂ films are found to be sensitive to annealing temperature and are described with GIXRD, SEM, AFM, UV‐Visible spectroscopy and electrical studies. X‐ray diffraction studies showed that the as‐deposited films were amorphous and at first changed to anatase and then to rutile phase with increase of annealing temperature. Optical constants of these films were derived from the transmission spectra and the refractive index dispersion of the films, subjected to annealing at different temperatures, is discussed in terms of the single oscillator‐Wemple and Didomenico model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and optical properties of AgGaS2 nanofilms

In this paper, AgGaS₂ nanofilms have been prepared by a two‐step process involving the successive ionic layer absorption and reaction (SILAR) and annealing method. Using AgNO₃, GaCl₃ and Na₂S₂O₃ as reaction sources, the mixture films were firstly deposited on quartz glass substrates at room temperature, and then annealed in Ar environment at 200–500 °C for 4 h, respectively. The effects of annealing temperature on structural and optical properties were investigated by XRD, UV‐Vis, EDS and photoluminescence (PL) spectra. It was revealed in XRD results that α‐Ag₉GaS₆ was contained in the samples annealed at 200 °C, and this phase was decreased with increase of the annealing temperatures. When the sample was annealed at above 400 °C, the chalcopyrite AgGaS₂ nanofilm was obtained. The preferred orientation was exhibited along the (112) plane. It was shown in atomic force microscopy (AFM) results that the grain sizes in AgGaS₂ nanofilms were 18‐24 nm and the thin films were smooth and strongly adherent to the substrates. When the annealing temperature was higher than 400 °C, it is an optimum condition to improve the structural and optical properties of the AgGaS₂ thin films. The room temperature PL spectra of AgGaS₂ nanofilms showed prominent band edge emission at 2.72 eV. Based on all results mentioned above, it can be concluded that the SILAR‐annealing method is preferable to preparing high‐quality AgGaS₂ nanofilms. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of ZnO-TiO2 films obtained by sol-gel method

The sol-gel route has been applied to obtain ZnO-TiO₂ thin films. For comparison, pure TiO₂ and ZnO films are also prepared from the corresponding solutions. The films are deposited by a spin-coated method on silicon and glass substrates. Their structural and vibrational properties have been studied as a function of the annealing temperatures (400-750 °C). Pure ZnO films crystallize in a wurtzite modification at a relatively low temperature of 400 °C, whereas the mixed oxide films show predominantly amorphous structure at this temperature. XRD analysis shows that by increasing the annealing temperatures, the sol-gel Zn/Ti oxide films reveal a certain degree of crystallization and their structures are found to be mixtures of wurtzite ZnO, Zn₂TiO₄, anatase TiO₂ and amorphous fraction. The XRD analysis presumes that Zn₂TiO₄ becomes a favored phase at the highest annealing temperature of 750 °C. The obtained thin films are uniform with no visual defects. The optical properties of ZnO-TiO₂ films have been compared with those of single component films (ZnO and TiO₂). The mixed oxide films present a high transparency with a slight decrease by increasing the annealing temperature.     

价态和结构对VO2薄膜热致相变光电性能的影响

本文通过合理控制真空还原时间和真空还原温度,利用真空还原V2O5的方法制备出具有优良热致相变性能的VO2薄膜;通过研究不同真空还原时间及真空退火温度对VO2薄膜结构和热致相变过程中光电性能的影响,得到最佳真空还原参数;制备的薄膜高／低温电阻变化最大达3个数量级;900nm波长光透过率在相变前后改变了40％左右,光学特性相变响应参数较大,热致相变性能优良,利用XPS,XRD对不同条件制备薄膜的化学状态和结晶状态进行了研究,结果表明较低温度退火有利于V^5 离子的还原,而升高退火温度可改善结晶状态,退火时间对VO2中结晶状况和V离子价态有显著影响,讨论了离子价态和样品结晶状态对VO2薄膜热相变过程中热滞回线的宽度,相变温度点的影响。     

Conversion of CuS thin films to structured nanosheet CuyS (1 < y ≦ 2) by vacuum annealing

In this study, large‐area and uniform thickness novel nano‐sheet structured CuS thin films on ITO glass have been prepared by the one‐step electrodeposition method from a dimethyl sulfoxide solution. Thin films of completely preserved nano‐sheet like morphology of Cu_yS (y = 1.75, 1.8, 1.95, and 2.0) are grown by vacuum annealing CuS thin films at 500 °C for different lengths of time. The 500 °C sample heated for 10 hours was nearly converted to single phase of Cu₂S with y ∼ 2. The optical direct band gaps of nano‐sheet Cu_yS thin films annealed at 500 °C of 2, 6, and 10 hours in vacuum were found to be 1.94, 1.68, and 1.44 eV, respectively.     

Crystallization kinetics in Cu46Zr45Al7Y2 bulk metallic glass by differential scanning calorimetry (DSC)

Crystallization transformation kinetics in isothermal and non-isothermal (continuous heating) modes were investigated in Cu₄₆Zr₄₅Al₇Y₂ bulk metallic glass by differential scanning calorimetry (DSC). In isochronal heating process, activation energy for crystallization at different crystallized volume fraction is analyzed by Kissinger method. Average value for crystallization in Cu₄₆Zr₄₅Al₇Y₂ bulk metallic glass is 361 kJ/mol in isochronal process. Isothermal transformation kinetics was described by the Johnson-Mehl-Avrami (JMA) model. Avrami exponent n ranges from 2.4 to 2.8. The average value, around 2.5, indicates that crystallization mechanism is mainly three-dimensional diffusion-controlled. Activation energy is 484 kJ/mol in isothermal transformation for Cu₄₆Zr₄₅Al₇Y₂ bulk metallic glass. These different results were discussed using kinetic models. In addition, average activation energy of Cu₄₆Zr₄₅Al₇Y₂ bulk metallic glass calculated using Arrhenius equation is larger than the value calculated by the Kissinger method in non-isothermal conditions. The reason lies in the nucleation determinant in the non-isothermal mode, since crystallization begins at low temperature. Moreover, both nucleation and growth are involved with the same significance during isothermal crystallization. Therefore, the energy barrier in isothermal annealing mode is higher than that of isochronal conditions.     

Studies on optical properties of polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor

Optical properties of spray deposited antimony (Sb) doped tin oxide (SnO₂) thin films, prepared from SnCl₂ precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0‐4 wt.% of Sb. All the films were deposited on microscope glass slides at the optimized substrate temperature of 400 °C. The films are polycrystalline in nature with tetragonal crystal structure. The doped films are degenerate and n‐type conducting. The sheet resistance of tin oxide films was found to decrease from 38.22 Ω/□ for undoped films to 2.17 Ω/□ for antimony doped films. The lowest sheet resistance was achieved for 2 wt.% of Sb doping. To the best of our knowledge, this sheet resistance value is the lowest reported so far, for Sb doped films prepared from SnCl₂ precursor. The transmittance and reflectance spectra for the as‐deposited films were recorded in the wavelength range of 300 to 2500 nm. The transmittance of the films was observed to increase from 42 % to 55 % (at 800 nm) on initial addition of Sb and then it is decreased for higher level of antimony doping. This paper investigates the variation of optical and electrical properties of the as‐deposited films with Sb doping. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructural,optical and electrical properties of GeO2 thin films prepared by sol‐gel method

GeO₂ thin films were prepared by sol‐gel method on ITO/Glass substrate. The electrical and optical properties and the microstructures of these films were investigated with special emphasis on the effects of an annealing treatment in ambient air. The films were annealed at various temperatures from 500 °C to 700 °C. Structural analysis through X‐ray diffraction (XRD) and atomic force microscope (AFM) showed that surface structure and morphological characteristics were sensitive to the treatment conditions. The optical transmittance spectra of the GeO₂/ITO/Glass were measured using a UV‐visible spectrophotometer. All films exhibited GeO₂ (101) orientation perpendicular to the substrate surface where the grain size increased with increasing annealing temperature. The optical transmittance spectroscopy further revealed high transparency (over 70 %) in the wave range 400 – 800 nm of the visible region. At an annealing temperature level of 700 °C, the GeO₂ films were found to possess a leakage current density of 1.31×10^‐6A/cm² at an electrical field of 20 kV/cm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of annealing on the properties of chemical bath deposited nanorods of CdSe thin films

Cadmium selenide (CdSe) thin films have been deposited by chemical bath deposition (CBD) on a glass substrate and they are annealed at 450 °C for 1 h. Scanning electron microscopic (SEM) image of as‐deposited CdSe shows the spherical shaped grains distributed over entire glass substrate. When it is annealed at 450 °C, clusters of nano‐rods with star shaped grains are formed. The X‐ray diffraction (XRD) study of the as‐deposited films exhibits a polycrystalline nature and it undergoes a structural phase transition from the metastable cubic to the stable hexagonal phase when annealed at 450 °C. Optical band gap of as‐deposited films (2.0 eV) has a blue shift with respect to the bulk value (1.7 eV) due to quantum confinement. The band gap energies of the films are decreased from 2.0 eV to 1.9 eV due to annealing at the temperature of 450 °C. The electrical resistivity, Hall mobility and carrier concentration of as‐deposited and annealed films are determined.     

热处理工艺对室温制备ZnO:Al薄膜结构与光电性能的影响

采用室温溅射加后续退火工艺制备了ZnO∶ Al透明导电薄膜.研究了热处理工艺对薄膜微观结构和光电性能的影响.研究表明:退火有助于减小Al~(3+)对Zn~(2+)的取代造成的晶格畸变,消除应力,促进晶粒长大,有效提高电子浓度和迁移率,降低电阻率;当溅射功率为80 W、退火温度为320 ℃时,薄膜的电阻率可低至8.6×10~(-4) Ω·cm;退火气氛对薄膜的导电性能有较大影响,真空退火可使吸附氧脱附,大大降低薄膜的方块电阻.而退火温度和退火气氛均对ZnO∶ Al薄膜的透光率没有明显影响,薄膜的透光率在86;以上.     

Optical properties and synthesis of CuInSe2 thin films by selenization of Cu/In layers

In this paper, we report the effect of annealing temperature on the properties of copper indium diselenide (CuInSe₂) thin films. The CuInSe₂ thin films were fabricated at 500 °C for 2 h by annealing Cu‐In layers (as precursors) selenized in a glass tube with pure selenium powder. The structural and morphological properties of the CuInSe₂ thin films were characterized respectively by means of x‐ray diffraction (XRD) and field‐emission scanning electron microscope (FE‐SEM). The type of CuInSe₂ thin film has been identified as direct allowed and the band gap value was determined. The study of UV/Visible/NIR absorption shows that the band gap value of CuInSe₂ thin film is about 1.07 eV, which is within an optimal range for harvesting solar radiation energy. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

电化学共沉积法制备GaAs纳米结构薄膜及表征

以含一定比例Ga与As2O3的酸性溶液(pH=2.5)作为前驱溶液,以Pt片为对电极,饱和甘汞电极(SCE)为参比电极,室温下利用三电极电化学站在Ti衬底上恒压沉积GaAs薄膜.然后对GaAs薄膜进行退火处理.利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM),以及荧光光度计(PL)分别对不同沉积电压下所制备的薄膜的晶体结构,薄膜形貌以及光学性能进行分析表征.结果表明:沉积电压以及退火过程对GaAs薄膜的形貌、晶体结构、薄膜质量有很大影响,所制备的GaAs薄膜退火前晶化程度较低,部分粒子表现出不均匀团聚.光致发光峰为红光发射,且单色性好.退火后的GaAs薄膜为面心立方晶型,呈纳米颗粒状,薄膜的光电性能明显提高.     

Electrical conduction mechanism and gas sensing properties of Pd-doped TiO2 films

Undoped and Pd-doped titanium oxide thin films (0.5 wt.%) were prepared by the sol-gel technique (dip-coating) on glass and silicon substrates. The as-deposited thin films were compacted by subjecting them to different annealing temperatures (300 °C, 500 °C). The dependences of the electrical conductivity vs. inverse temperature were investigated in air and in vacuum. A study of the effects of Pd-doping, annealing temperature and ambient conditions on their electrical properties was performed. The sensing behavior of titanium oxide thin films exposed to some reducing gases (methane, acetone, ethanol, formaldehyde and liquefied petroleum gas) was carried out, by means of electrical conductivity measurements. All the studied films are most sensitive to formaldehyde, with a special remark for the Pd-doped ones deposited on silicon substrates.     

Structural and optical properties of 6CaO·6SrO·7Al2O3 thin films derived by sol-gel dip coating process

The nanostructured 6CaO·6SrO·7Al₂O₃ (C6S6A7) thin films with cubic structure using calcium, strontium metals, aluminium isopropoxide and ethylene glycol monomethyl ether as stating materials has been fabricated via sol-gel route. Based on hydrolysis of Ca²⁺, Sr²⁺ and Al³⁺ in the sol-gel processing using ethylene glycol monomethyl ether as solvent have been employed as the precursor material. The films were coated on soda lime float glass by the dip coating technique and annealed at 450 °C in air atmosphere. The structure, morphology and composition of the films were investigated by Fourier transformed infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy indicating that the films were composed of C6S6A7 nanoparticles with cubic structure. The spectral transmittance of the films was measured in the wavelength range of 200-1100 nm using an UV-visible spectrometer. It has been found that the optical properties of the films significantly affected by precursor chemistry and annealing temperature due to the improvement of the crystallinity of the films with increasing annealing temperature and became stable when the annealing temperature is higher than 450 °C. The C6S6A7 films annealed at 450 °C had high transparency about 80% in wide visible range.     

Optical properties of thermally evaporated CdS thin films

CdS thin films of varying thicknesses were deposited on cleaned glass substrates at room temperature by thermal evaporation technique in a vacuum of about 2 x 10^‐5 torr. UV‐VIS spectra of the films were studied using the optical transmittance measurements which were taken in the spectral region from 300 nm to 1100 nm. The absorbance and reflectance spectra of the films in the UV‐VIS region were also studied. Optical constants such as optical band gap, extinction coefficient, refractive index, optical conductivity and complex dielectric constant were evaluated from these spectra. All the films were found to exhibit high transmittance (∼ 60 ‐ 93 %), low absorbance and low reflectance in the visible/near infrared region from ∼ 500 nm to 1100 nm. The optical band gap energy was found to be in the range 2.28 – 2.53 eV. All the films annealed at 300°C for 4 hours in vacuum (∼ 10^‐2 torr) showed a decrease in the optical transmittance with its absorption edge shifted towards the longer wavelength, leading to the result that the optical band gap decreases on annealing the films. Also, on annealing crystallinity of the films improves, resulting in decrease in the optical transmittance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

氩气退火时间对Fe(Se,Te)薄膜的性能影响研究

作为一种铁基超导薄膜,Fe(Se,Te)薄膜具有晶体结构简单、所包含的元素较少、易于合成的特点,不仅有利于超导机理研究而且有着潜在的技术应用价值。本文通过磁控溅射在温度为320 ℃的CaF₂单晶衬底上制备了Fe(Se,Te)薄膜,并在氩气氛围下进行了退火处理。研究了退火时间对Fe(Se,Te)薄膜的晶体结构、微观形貌、成分组成以及电输运特性的影响。结果表明:Fe(Se,Te)薄膜的结晶性较好,退火有助于消除薄膜样品中的FeSe相,薄膜的晶格常数c对退火不敏感,退火后薄膜晶粒尺寸变大;Fe(Se,Te)薄膜成分与靶材的名义组分存在一定的偏差,退火时间越长,Fe(Se,Te)薄膜表面的颗粒越密集;Fe(Se,Te)薄膜的电阻随温度升高而减小,呈现出半导体特性,退火3 h后电阻明显增大。