ZnO Films Synthesized by Solid-Source Chemical Vapor Deposition with c-Axis Parallel to Substrate

ZnO films with c -axis parallel to the substrate are reported.ZnO films are synthesized by solid-source chemical vapor deposition,a novel CVD technique,using zinc acetate dihydrate (solid) as the source material.The properties are characterized by X-ray diffraction,atomic force microscopy and transmission spectra.The parallel oriented ZnO films with mixed orientation for (100) and (110) planes are achieved on glass at the substrate temperature of 200℃ and the source temperature of 280℃,and a qualitative explanation is given for the forming of the mixed orientation.AFM images show that the surface is somewhat rough for the parallel oriented ZnO films.The transmission spectrum exhibits a high transmittance of about 85% in the visible region and shows an optical band gap about 3.25eV at room temperature.

Electrical and nonlinear optical properties of TGZO transparent conducting films deposited by magnetron sputtering

Thin transparent oxide conducting films(TCOFs)of titanium and gallium substituted zinc oxide(TGZO)were fabricated via radio frequency(RF)magnetron sputtering technique.The effects of RF power on electrical,linear and nonlinear optical characteristics were investigated by Hall tester,Ultraviolet(UV)-visible spectrophotometer and optical characterization method.The results indicate that RF power significantly influences the electrical and optical properties of the deposited films.As RF power raises,the resistivity and Urbach energy fall initially and then rise,while the figure of merit,mean visible transmittance and optical bandgap show the reverse variation trend.At RF power of 190 W,the TGZO sample exhibits the highest electro-optical properties,with the maximum figure of merit(1.14×10^(4)Ω^(-1)∙cm^(-1)),mean visible transmittance(86.9%)and optical bandgap(3.50 eV),the minimum resistivity(6.26×10^(-4)Ω∙cm)and Urbach energy(174.23 meV).In addition,the optical constants of the deposited films were determined by the optical spectrum fitting method,and the RF power dependence of nonlinear optical properties was studied.It is observed that all the thin films exhibit normal dispersion characteristics in the visible region,and the nonlinear optical parameters are greatly affected by the RF power in the ultraviolet region.

Low-Temperature Growth of ZnO Films on GaAs by Metal Organic Chemical Vapor Deposition

ZnO thin films were grown on GaAs （001） substrates by metal-organic chemical vapor deposition （MOCVD） at low temperatures ranging from 100 to 400℃. DEZn and 1-12 O were used as the zinc precursor and oxygen precursor, respectively. The effects of the growth temperatures on the growth characteristics and optical properties of ZnO films were investigated. The X-ray diffraction measurement （XRD） results indicated that all the thin films were grown with highly c- axis orientation. The surface morphologies and crystal properties of the films were critically dependent on the growth temperatures. Although there was no evidence of epitaxial growth, the scanning electron microscopy （SEM） image of ZnO film grown at 400℃ revealed the presence of ZnO microcrystallines with closed packed hexagon structure. The photoluminescence spectrum at room temperature showed only bright band-edge （3. 33eV） emissions with little or no deep-level e- mission related to defects.

Zn/O ratio and oxygen chemical state ofnanocrystalline ZnO films grown atdifferent temperatures

ZnO nanocrystalline films are prepared on Si substrates at different temperatures by using metal-organic chemical vapour deposition （MOCVD）. It is observed that when the growth temperature is low, the stoichiometric ratio between Zn and 0 atoms has a large deviation from the ideal ratio of 1：1. The ZnO grains in the film have small sizes and are not well crystallized, resulting in a poor photoluminescence （PL） property. When the temperature is increased to an appropriate value, the Zn/O ratio becomes optimized, and most of Zn and 0 atoms are combined into Zn-O bonds. Then the film has good crystal quality and good PL property. If the temperature is fairly high, the interracial mutual diffusion of atoms between the substrate and the epitaxial film appears, and the desorption process of the oxygen atoms is enhanced. However, it has no effect on the film property. The film still has the best crystal quality and PL property.

Preparation and Some Properties of Metal Organic Chemical Vapour Deposited Al-Doped ZnO Thin Films Using Single Solid Precursors

Zinc Oxide (ZnO) and Aluminium doped ZnO (AZO) thin films were deposited on soda lime glass by Metal Organic Chemical Vapour deposition technique (MOCVD), using prepared compound mixtures of Zinc Acetate di-hydrate (Zn(CH3COO)2⋅2H2O;ZAD) and Aluminium Acetyl-Acetonate (Al(C5H702)3;AAA) precursors at a temperature of 420°C. Effects of the varying mole percent concentrations of AAA precursor additives on the Al dopant concentrations in ZnO were systematically studied. The observations were made via investigations carried out on the morphological, optical, electrical and compositional properties of the deposited thin films. The thin films morphology was found to be strongly dependent on the varying concentration of AAA in the precursor mixtures. The average optical transmittance of the thin films in the uv-visible region was over 85% except 5 mol.% Al. While the energy band gaps were found to be in range of 3.27 - 3.36 eV. There is a blue-shift of the energy band edge observed between 0 and 5 mol.% AAA, which may be due to Burstein-Moss’ band gap widening effect and an opposing band gap renormalization effect at 10 mol.% AAA along with an extra band gap stabilization effect (Roth’s effect) at 15 mol.% AAA in rather quasi-sinusoidal or anomalous behaviour. The optical transmittance and electrical conductivity of ZnO were enhanced with addition of Al dopants. The RBS confirm the presence of Al, Zn and O, and evidence that Al dopants were successfully incorporated into the ZnO.

A Novel Approach to Synthesizing Porous ZnO Films: Inorganic Chelating Sol-Gel Method

Porous ZnO films are synthesized by inorganic chelating sol-gel method,which is a novel sol-gel technique using zinc nitrate as starting materials and citric acid as the chelating reagent.The crystal structure,surface morphology,porous and optical properties of the deposited films are investigated.X-ray diffraction pattern analysis shows that crystal structure of the ZnO films is hexagonal wurtzite.Scanning electron microscopy (SEM) shows that the ZnO film is porous.The curve of pore size distribution has two peak values at about 2.02nm and 4.97nm and BET surface area of the ZnO film is 27.57m2/g.In addition,the transmittance spectrum gives a high transmittance of 85% in the visible region and optical bandgap of the ZnO film (fired at 500℃) is 3.25eV.

基于共溅射ZnO/SnO_(2)异质结薄膜的气体传感器研究

采用射频磁控共溅射法在叉指电极上制备了ZnO/SnO_(2)n-n异质结复合薄膜,系统测试了其气敏特性,并分析了其气敏机理。结果表明,与ZnO薄膜和SnO_(2)薄膜气体传感器相比,ZnO/SnO_(2)异质结薄膜气体传感器具有更低的工作温度、更高的灵敏度以及更快的响应和恢复速度。ZnO/SnO_(2)异质结薄膜气体传感器对乙醇具有较好的选择性,最低检测体积分数为1×10^(-6),最佳工作温度为250℃;对1×10^(-4)乙醇气体的灵敏度可达18.4,响应时间和恢复时间分别为10 s和19 s。

Growth and Optical Properties of ZnO Films and Quantum Wells

The growth characteristics during metalorganic chemical vapor deposition and optical properties of ZnO films on sapphire （Al2O3） （0001） and （1120） substrates are studied. For the former,the effects of two important growth parameters,i, e. temperature and pressure, are investigated in detail. Due to the large lattice mismatch between the film and the substrate, ZnO nanocrystals are usually obtained. The growth behavior at the film-substrate interface is found to be strongly dependent on the growth temperature,while the growth pressure determines the shape of the nanostructures as they grow. It is difficult to obtain ZnO films that have good quality and a smooth surface simultaneously. Due to the smaller lattice mismatch,the critical thickness of ZnO on the Al2O3 （1120） surface is found to be much larger than that on the Al2O3 （0001） surface. ZnO/MgZnO quantum wells with graded well thicknesses are grown on the Al2O3 （1120） surfaces,and their optical properties are studied. The built-in electric field in the well layer, generated by the piezoelectric effect, is estimated to be 3 × 10^5 V/cm. It is found that growth at low temperatures and low pressures may facilitate the incorporation of acceptor impurities in ZnO.

Effect of sputtering conditions on growth and properties of ZnO :Al films

Al-doped zinc oxide（AZO） films were deposited on glass substrates by mid-frequency magnetron sputtering. The effects of substrate rotation speed and target-substrate distance on the electrical, optical properties and microstructure and crystal structures of the resulting films were investigated by scanning electron microscopy（SEM）, atomic force microscopy（AFM）, X-ray diffraction（XRD）, spectrophotometer and Hall-effect measurement system, respectively. XRD results show that all AZO films exhibit a strong preferred c-axis orientation. However, the crystallinity of films decreases with the increase of substrate rotation speed, accompanying with the unbalanced grains grows. For the films prepared at different target-substrate distances, the uniform microstructure and morphology are observed. The highest carrier concentration of 5.9×1020 cm-3 and Hall mobility of 13.1 cm^2/（V·s） are obtained at substrate rotation speed of 0 and target-substrate distance of 7 cm. The results indicate that the structure and performances of the AZO films are strongly affected by substrate rotation speed.

双层结构对ZnO TFT稳定性的影响

室温下采用射频磁控溅射方法在SiO_(2)/Si衬底上沉积了单层ZnO薄膜和高氧/低氧双层ZnO薄膜,采用电子束蒸发设备蒸镀Al电极,制备单沟道ZnO TFTs和双层沟道ZnO TFTs。比较两种结构ZnO TFTs的各种性能参数,分析双层结构对TFTs产生的影响。实验结果表明,底部高含氧量ZnO层和顶部低含氧量ZnO层构成了DAL同质结且高氧/低氧薄膜存在载流子浓度产差,利用载流子从高浓度向低浓度扩散的性质,可以填补栅介电层和沟道层之间的界面态缺陷,使器件界面类受主陷阱减少,有效降低TFTs的滞回现象。与单有源层TFTs相比,双沟道层TFTs还具有电学调制作用,其电学性能和稳定性均有明显的提高,得到最佳TFTs的开/关电流比达到3.44×10^(9),亚阈值摆幅为0.68 V/dec,阈值电压偏移为1.2 V。

First-principles study and electronic structures of Mn-doped ultrathin ZnO nanofilms

The first-principles density functional calculation is used to investigate the electronic structures and magnetic properties of Mn-doped and N-co-doped ZnO nanofilms.The band structure calculation shows that the band gaps of ZnO films with 2,4,and 6 layers are larger than the band gap of the bulk with wurtzite structure and decrease with the increase of film thickness.However,the four-layer ZnO nanofilms exhibit ferromagnetic phases for Mn concentrations less than 24% and 12% for Mn-doping performed in the whole layers and two layers of the film respectively,while they exhibit spin glass phases for higher Mn concentrations.It is also found,on the one hand,that the spin glass phase turns into the ferromagnetic one,with the substitution of nitrogen atoms for oxygen atoms,for nitrogen concentrations higher than 16% and 5% for Mn-doping performed in the whole layers and two layers of the film respectively.On the other hand,the spin-glass state is more stable for ZnO bulk containing 5% of Mn impurities,while the ferromagnetic phase is stable by introducing the p-type carriers into the bulk system.Moreover,it is shown that using the effective field theory for ferromagnetic system,the Curie temperature is close to the room temperature for the undamped Ruderman-Kittel-Kasuya-Yoshida（RKKY） interaction.

Crystallization Behavior and Properties of B-Doped ZnO Thin Films Prepared by Sol-Gel Method with Different Pyrolysis Temperatures

Boron-doped zinc oxide transparent （BZO） films were prepared by sol-gel method. The effect of pyrolysis temperature on the crystallization behavior and properties was systematically investigated. XRD patterns revealed that the BZO films had wurtzite structure with a preferential growth orientation along the c-axis. With the increase of pyrolysis temperature, the particle size and surface roughness of the BZO films increased, suggesting that pyrolysis temperature is the critical factor for determining the crystallization behavior of the BZO films. Moreover, the carrier concentration and the carrier mobility increased with increasing the pyrolysis temperature, and the mean transmittance for every film is over 90% in the visible range.

Effects of high-dose Ge ion implantation and post-implantation annealing on ZnO thin films

This paper reports that ion implantation to a dose of 1 ×10^17 ions/cm^2 was performed on c-axis-orientated ZnO thin films deposited on （0001） sapphire substrates by the sol-gel technique. After ion implantation, the as-implanted ZnO films were annealed in argon ambient at different temperatures from 600 - 900 ℃. The effects of ion implantation and post-implantation annealing on the structural and optical properties of the ZnO films were investigated by x-ray diffraction （XRD）, photoluminescence （PL）. It was found that the intensities of （002） peak and near band edge （NBE） exitonic ultraviolet emission increased with increasing annealing temperature from 600- 900 ℃. The defect related deep level emission （DLE） firstly increased with increasing annealing temperature from 600 - 750 ℃, and then decreased quickly with increasing annealing temperature. The recovery of the intensities of NBE and DLE occurs at ～850℃ and ～750℃ respectively. The relative PL intensity ratio of NBE to DLE showed that the quality of ZnO films increased continuously with increasing annealing temperature from 600 - 900 ℃.

耐高温柔性Mica/ZnO薄膜的制备与表征

以氟晶云母片为衬底,进行柔性ZnO透明导电薄膜(Mica/ZnO)的制备与表征。利用XRD和SEM表征可知,晶种水热法比直接水热法更有利于制备Mica/ZnO薄膜。研究发现,晶种水热法制备Mica/ZnO薄膜分为颗粒状ZnO晶体生长阶段、颗粒状ZnO晶体成长为棒状ZnO晶体阶段和棒状ZnO晶体成长三个阶段。采用晶种水热法制备Mica/ZnO薄膜适宜的晶化时间为26h,制备的致密棒状ZnO晶体长度约500nm左右。制备的Mica/ZnO薄膜可耐500℃以上的高温,为研究耐高温柔性ZnO透明导电薄膜提供更为丰富的柔性衬底材料和制备方法。

Fabrication of ZnO films by radio frequency magnetron sputtering and annealing

ZnO thin films were deposited on Si（111） substrates through a radio frequency （rf） magnetron sputtering system. Then the samples were annealed at different temperatures in air ambience and ammonia ambience respectively. The structure and composition of the ZnO films were studied by X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The morphology of the samples was studied by scanning electron microscopy （SEM）. Measured results show that ZnO films with hexagonal wurtzite structure were grown on Si（111） substrates when annealed in the two ambiences. The volatilization process of ZnO in the ammonia ambience at high temperature was discussed and the mechanism of the reaction was analyzed.

Properties of doped ZnO transparent conductive thin films deposited by RF magnetron sputtering using a series of high quality ceramic targets

To obtain high transmittance and low resistivity ZnO transparent conductive thin films,a series of ZnO ceramic targets（ZnO：Al,ZnO：（Al,Dy）,ZnO：（Al,Gd）,ZnO：（Al,Zr）,ZnO：（Al,Nb）,and ZnO：（Al,W）） were fabricated and used to deposit thin films onto glass substrates by radio frequency（RF） magnetron sputtering.X-ray diffraction（XRD） analysis shows that the films are polycrystalline fitting well with hexagonal wurtzite structure and have a preferred orientation of the（002） plane.The transmittance of above 86% as well as the lowest resistivity of 8.43 × 10^-3 Ω·cm was obtained.

Effect of annealing temperature on the microstructure and optoelectrical properties of ZnO thin films and their application in self-powered accelerometers

This paper reports a piezoelectric nanogenerator(NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide(ZnO) thin film, a magnetron sputtering machine was used. Polymethyl methacrylate(PMMA) and aluminum-doped zinc oxide(AZO) were used as the insulating layer and the top electrode of the NG, respectively. The experimental results show that the ZnO thin films annealed at 150℃ exhibited the highest crystallinity among the prepared films and an optical band gap of 3.24 eV. The NG fabricated with an AZO/PMMA/ZnO/stainless steel configuration exhibited a higher output voltage than the device with an AZO/ZnO/PMMA/stainless steel configuration. In addition, the annealing temperature affected the open-circuit voltage of the NGs;the output voltage reached 3.81 V when the annealing temperature was 150℃. The open-circuit voltage of the prepared self-powered accelerometer increased linearly with acceleration. In addition, the small NG-based accelerometer, which exhibited excellent fatigue resistance, can be used for acceleration measurements of small and lightweight devices.

Propagations of Rayleigh and Love waves in ZnO films/glass substrates analyzed by three-dimensional finite element method

Propagation characteristics of surface acoustic waves（SAWs） in ZnO films/glass substrates are theoretically investigated by the three-dimensional（3D） finite element method. At first, for（11ˉ20） ZnO films/glass substrates, the simulation results confirm that the Rayleigh waves along the [0001] direction and Love waves along the [1ˉ100] direction are successfully excited in the multilayered structures. Next, the crystal orientations of the ZnO films are rotated, and the influences of ZnO films with different crystal orientations on SAW characterizations, including the phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency, are investigated. The results show that at appropriate h/λ, Rayleigh wave has a maximum k^2 of 2.4% in（90°, 56.5°, 0°） ZnO film/glass substrate structure; Love wave has a maximum k^2 of 3.81% in（56°, 90°, 0°） ZnO film/glass substrate structure. Meantime, for Rayleigh wave and Love wave devices, zero temperature coefficient of frequency（TCF） can be achieved at appropriate ratio of film thickness to SAW wavelength. These results show that SAW devices with higher k^2 or lower TCF can be fabricated by flexibly selecting the crystal orientations of ZnO films on glass substrates.

Induced growth of high quality ZnO thin films by crystallized amorphous ZnO

This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds （buffer layer）, ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80 ℃. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

ZnO纳米颗粒掺杂对镍钛合金表面微弧氧化膜层形貌及性能的影响

针对镍钛合金在体内复杂生理环境的作用下受到腐蚀而释放大量镍离子的问题,向以NaAlO_(2)、C_(10)H_(14)N_(2)Na_(2)O_(8)、Na_(2)HPO_(4)·12H_(2)O为主要成分的电解液中添加ZnO纳米颗粒,通过微弧氧化技术在镍钛合金表面制备耐腐蚀陶瓷氧化膜层。采用帕累托法则和正态分布曲线分析ZnO纳米颗粒对氧化膜层孔隙率和孔隙尺寸的作用,通过SEM、EDS、电化学工作站以及水滴接触角来研究颗粒掺杂对氧化膜层微观形貌、化学组分、耐腐蚀性及润湿性能的影响。结果表明:颗粒掺杂后的氧化膜层更加平整致密,孔隙率下降65.3%,孔径平均值从0.518μm降至0.321μm;随着ZnO纳米颗粒的加入,复合膜层的O、Al、Zn含量增加,Ni含量下降,阻抗模值上升,动电位极化曲线明显地向右上方偏移,自腐蚀电位上升32.4%,而电流密度下降一个数量级。