Preparation and characterization of nano and microcrystalline ZnO thin films by PLD

Nano and microcrystalline ZnO thin films were prepared on glass substrates using pulsed laser deposition technique under a vacuum of 3 × 10⁻⁷ Torr at different laser power density. Composition analyses show that the films deposited at low laser power density have more structural defects than the film deposited at high laser power density. It confirms that the content of Zn in free-state decreased greatly at high laser power density. Atomic force microscopy analysis shows that the surface roughness of the deposited films increases with an increase in laser power density. X-ray diffraction analyses show that all the films are oriented along (0 0 2) direction independently on the laser power density applied. The structural quality increases with an increase in laser power density. It is due to the fact that the increase of laser power density leads to the enhancement of peak intensity. The increase of laser power density reduces the film transmission in the visible range of the spectra. The optical band gap value is found to be in the range from 3.42 to 3.39 eV. It shows that the optical band gap value decreases with an increase in laser power density. FTIR analysis shows that the hydrated oxide content in the deposited films decreases with an increase in laser power density.     

不同衬底温度下PLD法制备的氧化锌薄膜的特性

利用GCR-170型脉冲激光器Nd:YAG的三次谐波(355nm),以蓝宝石Al2O3(0001)为衬底,在不同温度下采用脉冲激光沉积法制备了ZnO薄膜.通过原子力显微镜、Raman谱、光致发光谱、红外透射谱、霍尔效应和表面粗糙度分析仪对制备的ZnO薄膜进行了测试.分析了在不同衬底温度下薄膜的表面形貌、光学特性,同时进行了薄膜结构和厚度的测试.研究表明:衬底温度对ZnO薄膜的表面形貌、光学特性、结构特性都是重要的工艺参量,尤其在500℃时沉积的ZnO薄膜致密均匀,并表现出较强的紫外发射峰.     

Preparation and characterization of ZnTe thin films by SILAR method

Nanocrystalline zinc telluride (ZnTe) thin films were prepared by using successive ionic layer adsorption and reaction (SILAR) method from aqueous solutions of zinc sulfate and sodium telluride. The films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques. The synthesized ZnTe thin films were nanocrystalline with densely aggregated particles in nanometer scale and were free from the voids or cracks. The optical band gap energy of the film was found to be thickness dependent. The elemental chemical compositional stoichiometric analysis revealed good Zn:Te elemental ratio of 53:47.     

Synthesis, characterization and photoelectrochemical properties of n-CdS thin films

Cadmium sulfide thin films have been deposited on glass substrates by simple and cost effective chemical bath deposition technique. Triethanolamine was used as a complexing agent. The preparative parameters like ion concentration, temperature, pH, speed of substrate rotation and deposition time have been optimized for good quality thin films. The ‘as-grown’ films are characterized for structural, electrical, optical and photoelectrochemical (PEC) properties. The X-ray diffraction (XRD) studies reveal that the films are polycrystalline in nature. Energy-dispersive analysis by X-ray (EDAX) shows that films are cadmium rich. Uniform deposition of CdS thin films on glass substrate is observed from scanning electron microscopy (SEM) and atomic force microscopy (AFM) micrographs. Optical studies reveal a high absorption coefficient (10⁴ cm⁻¹) with a direct type of transition. The band gap is estimated to be 2.47 eV. The film shows n-type conduction mechanism. The photoelectrochemical (PEC) cell with CdS thin film as a photoanode and sulfide/polysulfide (1 M) solution as an electrolyte have been constructed and investigated for various cell parameters. The solar to electrical conversion efficiency (η) and fill factor (ff) are found to be 0.049% and 0.36, respectively.     

Preparation and characterization of nanocrystalline ITO thin films on glass and clay substrates by ion-beam sputter deposition method

Nanocrystalline indium tin oxide (ITO) thin films were prepared on clay-1 (Clay-TPP-LP-SA), clay-2 (Clay-TPP-SA) and glass substrates using ion-beam sputter deposition method. X-ray diffraction (XRD) patterns showed that the as-deposited ITO films on both clay-1 and clay-2 substrates were a mixture of amorphous and polycrystalline. But the as-deposited ITO films on glass substrates were polycrystalline. The surface morphologies of as-deposited ITO/glass has smooth surface; in contrast, ITO/clay-1 has rough surface. The surface roughnesses of ITO thin films on glass and clay-1 substrate were calculated as 4.3 and 83 nm, respectively. From the AFM and SEM analyses, the particle sizes of nanocrystalline ITO for a film thickness of 712 nm were calculated as 19.5 and 20 nm, respectively. Optical study showed that the optical transmittance of ITO/clay-2 was higher than that of ITO/clay-1. The sheet resistances of as-deposited ITO/clay-1 and ITO/clay-2 were calculated as 76.0 and 63.0 Ω/□, respectively. The figure of merit value for as-deposited ITO/clay-2 (12.70 × 10⁻³/Ω) was also higher than that of ITO/clay-1 (9.6 × 10⁻³/Ω), respectively. The flexibilities of ITO/clay-1 and ITO/clay-2 were evaluated as 13 and 12 mm, respectively. However, the ITO-coated clay-2 substrate showed much better optical and electrical properties as well as flexibility as compared to clay-1.     

高脉冲功率能量PLD法制备MgZnO薄膜中的沉积机理

用PLD法成功制备了一系列高质量的MgZnO薄膜。实验中发现高脉冲能量沉积薄膜的结构和发光特性随基片温度的变化规律与低脉冲能量下的结果不一样:基片在室温时高脉冲能量制备薄膜的XRD峰的半峰全宽比高基片温度时的结果相对更小;AFM显示其颗粒变大,柱状生长突出;PL谱紫峰与绿峰强度比最大,结晶质量反而提高。另一方面,与低脉冲能量时相反,增大氧气压强后高脉冲能量沉积的薄膜XRD半峰全宽变窄。结合实验现象和表征,合理解释了高脉冲能量沉积的机理。室温制备高质量MgZnO薄膜的PLD沉积机理对于以后在柔性衬底上沉积薄膜的研究有重要的参考价值。     

Preparation and characterization of Mg-doped ZnO thin films by sol-gel method

Undoped and Mg-doped ZnO thin films were deposited on Si(1 0 0) and quartz substrates by the sol-gel method. The thin films were annealed at 873 K for 60 min. Microstructure, surface topography and optical properties of the thin films have been measured by X-ray diffraction (XRD), atomic force microscope (AFM), UV-vis spectrophotometer, and fluorophotometer (FL), respectively. The XRD results show that the polycrystalline with hexagonal wurtzite structure are observed for the ZnO thin film with Mg:Zn = 0.0, 0.02, and 0.04, while a secondary phase of MgO is evolved for the thin film with Mg:Zn = 0.08. The ZnO:Mg-2% thin film exhibits high c-axis preferred orientation. AFM studies reveal that rms roughness of the thin films changes from 7.89 nm to 16.9 nm with increasing Mg concentrations. PL spectra show that the UV-violet emission band around 386-402 nm and the blue emission peak about 460 nm are observed. The optical band gap calculated from absorption spectra and the resistivity of the ZnO thin films increase with increasing Mg concentration. In addition, the effects of Mg concentrations on microstructure, surface topography, PL spectra and electrical properties are discussed.     

Preparation and characterization of electrodeposited SnS thin films

Tin sulfide (SnS) thin films have been deposited by electrodeposition using potentiostaic method on indium doped tin oxide (ITO) coated glass substrates from aqueous solution containing SnCl₂·2H₂O and Na₂S₂O₃ at various potentials. Good quality thin films were obtained at a cathodic potential −1000 mV versus saturated calomel electrode (SCE). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). X-ray diffraction analysis shows that the crystal structure of SnS thin films is orthorhombic with preferential orientation along 〈0 2 1〉 plane. Microstructural parameters such as crystallite size, micro strain, and dislocation density are calculated and found to depend upon cathodic potentials. SEM studies reveal that the SnS films exhibited uniformly distributed grains over the entire surface of the substrate. The optical transmittance studies showed that the direct band gap of SnS is 1.1 eV. FTIR was used to further characterize the SnS films obtained at various potentials.     

Effects of post-annealing on the structural and nanomechanical properties of Ga-doped ZnO thin films deposited on glass substrate by rf-magnetron sputtering

In this study, the effects of post-annealing on the structure, surface morphology and nanomechanical properties of ZnO thin films doped with a nominal concentration of 3 at.% Ga (ZnO:Ga) are investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and nanoindentation techniques. The ZnO:Ga thin films were deposited on the glass substrates at room temperature by radio frequency magnetron sputtering. Results revealed that the as-deposited ZnO:Ga thin films were polycrystalline albeit the low deposition temperature. Post-annealing carried out at 300, 400 and 500 °C, respectively, has resulted in progressive increase in both the average grain size and the surface roughness of the ZnO:Ga thin film, in addition to the improved thin films crystallinity. Moreover, the hardness and Young's modulus of ZnO:Ga thin films are measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. The hardness and Young's modulus of ZnO:Ga thin films increased as the annealing temperature increased from 300 to 500 °C, with the best results being obtained at 500 °C.     

Pulsed laser deposition of doped skutterudite thin films

Ca_xCo₄Sb₁₂ skutterudite thin films have been prepared by pulsed laser deposition using a Nd:YAG laser working at 532 or 266 nm of wavelength. Characterization has been carried out by X-ray diffraction, atomic force microscopy and scanning electron microscopy. Emphasis has been put on the difficulty to obtain the skutterudite phase. Influence of the deposition temperature, the way of sticking the substrate, the laser fluence, the base pressure prior to deposition and the laser wavelength has been studied. All parameters revealed to have a drastic effect, and the skutterudite could only be achieved in a very narrow range of temperature and laser fluence, for a given wavelength, showing the importance on how these parameters are measured to ensure reproducible results.     

Magnetoelectrical properties of W doped ZnO thin films

ZnO thin films were deposited on the Si(100) substrate by rf sputtering using a 99.999% pure commercially bought and a home made target under 100 W power. The home made ZnO target, including 1–2% tungsten, was synthesized via solid state reaction. Thin films were deposited under a flow of 70% argon and 30% O₂ gas mixture followed by post-deposition annealing under 1 Torr oxygen atmosphere. Both deposition and post-deposition annealing were done at 420±1 °C. The structural analyses show that the films were in the [0002] preferred direction and that W atoms are bound to the oxygen atoms by replacing the Zn host atoms. Although no specific change was observed in the magnetic properties as a result of W doping, significant changes in the electrical properties were observed, as determined by the longitudinal and transversal magneto-electrical measurements. It was found that the W impurities induce better insulating properties due to lower carrier concentration and higher resistivity values. On the other hand, the enhanced positive magnetoresistivity and the existence of polarized spin currents, which were not specific for pure ZnO thin films, were observed in W doped ZnO films below 10 K.     

Al掺杂ZnO薄膜的厚度对其结构及磁学性能的影响

采用直流磁控共溅的方法在玻璃基底上制备了不同厚度的Al掺杂ZnO薄膜,并在真空和空气中分别退火.利用X射线衍射仪(XRD)和物理性能测量仪(PPMS)对系列薄膜的结构和磁性进行了表征.XRD结果显示:随着膜厚的增加,晶粒尺寸逐渐增大,薄膜的内应力逐渐减小.在空气退火的薄膜样品中观察到了室温的铁磁性,薄膜的饱和磁化强度M_s 随着膜厚的增加而增大,而矫顽力H_c却随着膜厚的增加而减小. 关键词： Al掺杂ZnO薄膜 薄膜厚度 应力 铁磁性     

Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films

ZnO thin films grown on Si(1 1 1) substrates by using atomic layer deposition (ALD) were annealed at the temperatures ranging from 300 to 500 °C. The X-ray diffraction (XRD) results show that the annealed ZnO thin films are highly (0 0 2)-oriented, indicating a well ordered microstructure. The film surface examined by the atomic force microscopy (AFM), however, indicated that the roughness increases with increasing annealing temperature. The photoluminescence (PL) spectrum showed that the intensity of UV emission was strongest for films annealed at 500 °C. The mechanical properties of the resultant ZnO thin films investigated by nanoindentation reveal that the hardness decreases from 9.2 GPa to 7.2 GPa for films annealed at 300 °C and 500 °C, respectively. On the other hand, the Young's modulus for the former is 168.6 GPa as compared to a value of 139.5 GPa for the latter. Moreover, the relationship between the hardness and film grain size appear to follow closely with the Hall-Petch equation.     

Mn掺杂ZnO薄膜的结构及光学性能研究

通过脉冲激光沉积(PLD)法在SiO₂基片上制备了不同含量的Mn掺杂ZnO薄膜.X射线衍射、X射线能谱、原子力显微镜与紫外-可见分光光度计测试结果表明：少量的Mn离子的掺杂并没有改变薄膜的结构，薄膜具有(103)面的择优取向；PLD法制备的ZnO薄膜的成分与靶材基本一致，实现了薄膜的同组分沉积；薄膜表面比较平坦，起伏度小于80nm，颗粒尺寸主要集中在25nm附近；但是Mn离子的掺杂改变了ZnO薄膜的禁带宽度，随Mn掺杂含量的增加，ZnO薄膜的禁带宽度增加；当薄膜中Mn含量从6%增加到 关键词： PLD ZnO薄膜 Mn掺杂 吸收谱     

Physical properties of Pb doped ZnS thin films prepared by ultrasonic spray technique

In the present work, high quality Pb doped ZnS thin films were deposited on glass substrates at 450°C using spray ultrasonic technique. The dependence of the structural, morphological and optical properties of the films on the lead (Pb) doping amount was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis–NIR spectrophotometry, and four-point method. The improvement of the obtained Pb:ZnS thin films properties were discussed as a function of Pb concentration (0.5 to 2 at.%). The average crystallite size of Pb:ZnS was found in the range of 25–37 nm. The scanning electron microscopy (SEM) reveals that the films are continuous, homogeneous and dense. The UV–vis–NIR spectroscopy characterizations demonstrated that all the films exhibit good transmittance (60–70%) in the visible region and their optical band gap energy ($E_{\mathrm{g}}$) changes from 3.92 to 3.6 eV. The films electrical resistivity showed an apparent dependence on Pb content.     

Preparation of ZnO-doped Al films by spray pyrolysis technique

Al-doped zinc oxide (AZO) thin films have been prepared by spray pyrolysis (SP) technique of zinc acetate and aluminium nitrate, and the effect of thickness on structural and optical properties has been investigated. The structural and optical characteristics of the AZO films were examined by X-ray diffraction (XRD) and double-beam spectrophotometry. These films, deposited on glass substrates at an optimal substrate temperature (T_S = 450 °C), have a polycrystalline texture with a hexagonal structure. Transmission measurements showed that for visible wavelengths, the AZO films have an average transmission of over 90%. The optical parameters have been calculated. The dependence of the refractive index, n, and extinction coefficient, k, on the wavelength for the sprayed films is also reported. Optical band gap of AZO is 3.30 and 3.55 eV, respectively, depending on the film thicknesses.     

Structural and optical properties of La-doped BaSnO3 thin films grown by PLD

In this study the structural and optical properties of lanthanum-doped BaSnO₃ powder samples and thin films deposited on fused silica were investigaed using laser ablation. Under an oxygen pressure of 5×10⁻⁴ mbar, phase pure BaSnO₃ films with a lattice constant of 0.417 nm and grain size of 21 nm were prepared at 630 °C. The band gap of BaSnO3 powder sample and thin films was calculated to be 3.36 eV and 3.67 eV, respectively. There was a progressive increase in conductivity for thin films of BaSnO₃ doped with 0~7 at% of La. The highest conductivity, 9 Scm⁻¹, was obtained for 7 at% La-doped BaSnO₃. Carrier concentration, obtained from Burstein-Moss (B-M) shift, nearly matches the measured values except for 3 at% and 10 at% La-doped BaSnO₃ thin films.     

Structural characterization of supported nanocrystalline ZnO thin films prepared by dip-coating

Nanocrystalline ZnO thin films prepared by the sol-gel dip-coating technique were characterized by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS). The structures of several thin films subjected to (i) isochronous annealing at 350, 450 and 550 °C, and (ii) isothermal annealing at 450 °C during different time periods, were characterized. The studied thin films are composed of ZnO nanocrystals as revealed by analysing several GIXD patterns, from which their average sizes were determined. Thin film thickness and roughness were determined from quantitative analyses of AFM images and XR patterns. The analysis of XR patterns also yielded the average density of the studied films. Our GISAXS study indicates that the studied ZnO thin films contain nanopores with an ellipsoidal shape, and flattened along the direction normal to the substrate surface. The thin film annealed at the highest temperature, T = 550 °C, exhibits higher density and lower thickness and nanoporosity volume fraction, than those annealed at 350 and 450 °C. These results indicate that thermal annealing at the highest temperature (550 °C) induces a noticeable compaction effect on the structure of the studied thin films.     

Growth of n-type ZnO thin films by using mixture gas of hydrogen and argon

High-quality oxide semiconductor ZnO thin films were prepared on single-crystal sapphire and LaAlOZnO薄膜 氩氢混合气体 薄膜生长 异质结构 薄膜物理学ZnO, PLD, heterostructureProject supported by the National Natural Science Foundation of China (Grant No 19974001) and the National Key Basic Research Special Foundation of China (Grant No NKBRSF G1999064604 and G2000036505).2005-05-309/3/2005 12:00:00 AMHigh-quality oxide semiconductor ZnO thin films were prepared on single-crystal sapphire and baAlO3 substrates by pulsed laser deposition （PLD） in the mixture gas of hydrogen and argon. Low resistivity n-type ZnO thin films with smoother surface were achieved by deposition at 600℃ in 1Pa of the mixture gas. in addition, ferromagnetism was observed in Co-doped ZnO thin films and rectification Ⅰ - Ⅴ curves were found in p-GaN/n-ZnO and p-CdTe/n-ZnO heterostructure junctions. The results indicated that using mixture gas of hydrogen and argon in PLD technique was a flexible method for depositing high-quality n-type oxide semiconductor films, especially for the multilayer thin film devices.     

Al/ZnO/Al薄膜的结构与磁性分析

采用直流磁控溅射的方法制备了Al/ZnO/Al纳米薄膜,并对薄膜分别在真空及空气中进行退火处理.利用X射线衍射仪(XRD)和物理性能测量仪(PPMS)分别对薄膜样品的结构和磁性进行了表征.XRD分析表明,不同的退火氛围对薄膜的微结构有着很大的影响.采用了一种新的修正方法对磁测量结果进行修正,计算了基底拟合误差的最大值,并对修正后样品的磁性进行了分析.结果显示,室温铁磁性可能与Al和ZnO基体之间发生的电荷转移以及在不同退火氛围下Al在ZnO晶格中的地位变化有关. 关键词： Al/ZnO/Al薄膜 铁磁性 磁性表征