溅射参数对ZnO薄膜物性的影响

采用磁控溅射方法分别在ITO玻璃和硅片上成功制备了具有良好C轴取向的ZnO薄膜.并研究了溅射气压,基底温度,以及氧偏压对ZnO薄膜物性的影响,从而确定了制备ZnO薄膜的最佳溅射条件.     

旋涂水溶液前驱体制备氧化锌薄膜及其性质

通过旋涂法, 采用Zn(OAc)2·2H2O和聚环氧乙烷(PEO)的水溶液为前驱体在不同的热处理温度下制备了ZnO薄膜. PEO的加入增加了溶液的成膜性, 其较低的热分解温度有利于制得纯净的ZnO薄膜. 文中考察了在不同热处理温度下制备的ZnO薄膜的形貌、结晶性、带隙(Eg)以及电导性. 原子力显微镜(AFM)测试表明在热处理温度为400、450和500 ℃制备的ZnO薄膜的粗糙度均方根值分别为3.3、2.7和3.6 nm. 采用透射电子显微镜(TEM)测试发现ZnO薄膜中含有大量纳晶粒子. 通过测试ZnO薄膜的UV-Vis吸收光谱, 根据薄膜位于373 nm处的吸收带边计算得到ZnO的带隙为3.3 eV. 通过对薄膜的电流-电压(I-V)曲线的测试计算得到在热处理温度为400、450和500 ℃制备的ZnO薄膜的电阻率分别为3.3×109、2.7×109和6.6×109 Ω·cm. 450 ℃时制备的ZnO薄膜的电阻率最小, 主要是由于较高的热处理温度有利于提高薄膜的纯度、密度和吸附氧. 而纯度较高、密度较大的薄膜电阻率比较小; 吸附氧含量增加, 晶界势垒增大, 电阻率增大. 因此在纯度和吸附氧的双重作用下450 ℃时制备的ZnO薄膜的电阻率最小, 而500 ℃时制备的ZnO薄膜的电阻率最大.     

Ag改性纳米ZnO薄膜及光催化活性

采用溶胶-凝胶法和光还原沉积贵金属法结合制备出Ag改性的纳米ZnO薄膜。利用FESEM、XPS、ESR、UV-Vis分析了纳米Ag-ZnO薄膜的表面形貌、表面组成和光谱特征。FESEM分析表明银在纳米ZnO薄膜表面形成原子簇而没有形成均匀覆盖层。XPS分析表明负载在纳米ZnO薄膜表面的银以Ag⁰形式存在; 相对于纳米ZnO薄膜, 纳米Ag-ZnO薄膜中晶格氧的含量有所下降,而表面羟基氧和吸附氧的含量显著增加。纳米Ag-ZnO薄膜的ESR峰强比纳米ZnO薄膜大,表明纳米Ag-ZnO薄膜中束缚单电子的氧空位的浓度高于纳米ZnO薄膜。UV-Vis分析纳米Ag-ZnO薄膜的紫外可见吸收光谱可能是纳米银粒子与纳米ZnO薄膜共同作用的结果。以甲基橙为模拟污染物,考察了纳米Ag-ZnO薄膜的光催化活性以及银沉积量对催化剂活性的影响。光催化降解结果表明,银的沉积量为0.018 2 mg·cm^-2的纳米Ag-ZnO薄膜的光催化活性最高,在紫外光照射3 h后甲基橙降解率约为78%,而纳米ZnO薄膜约为62%。     

结晶性和粒子尺寸对C60薄膜晶体管迁移率的影响

采用真空沉积方法在不同基片温度(30~190℃)和沉积压力(1×10~(-4)和1×10~(-1) Pa)下制得了C_(60)薄膜。研究了薄膜的结晶性和晶粒尺寸对迁移率的影响。采用X射线衍射和原子力显微镜表征了薄膜的结构和形貌,发现提高基片温度,薄膜的结晶性和晶粒尺寸均提高;提高沉积压力,薄膜的晶粒尺寸增大而结晶性不变。场效应测试结果表明,C_(60)薄膜的迁移率与其结晶性密切相关,高的结晶性有利于获得高迁移率;不同于平面有机半导体材料,对于球状C_(60)半导体材料,大的晶粒尺寸可能导致低迁移率。     

TiO2薄膜光电极能带结构和催化活性的初探

以阳极氧化法制得的TiO₂薄膜光电极为工作电极,铂环为对电极,饱和甘汞电极为参比电极,组成光电催化降解苯酚体系.运用电化学阻抗图谱(EIS),测得光电催化过程中TiO₂薄膜光电极的空间电荷层电容,计算出半导体能带结构参数——空间电荷层宽度W.结果证明:当空间电荷层宽度W随阳极偏压增加而增大时,TiO₂薄膜电极光催化活性提高;当其等于薄膜厚度时,光催化活性最好,此时出现最佳偏压值;继续增加偏压,活性反而有所下降.     

结晶性和粒子尺寸对C60薄膜晶体管迁移率的影响

采用真空沉积方法在不同基片温度（30~190℃）和沉积压力（1×10^-4和1×10^-1 Pa）下制得了C₆₀薄膜。研究了薄膜的结晶性和晶粒尺寸对迁移率的影响。采用X射线衍射和原子力显微镜表征了薄膜的结构和形貌,发现提高基片温度,薄膜的结晶性和粒子尺寸均提高;提高沉积压力,薄膜的晶粒尺寸增大而结晶性不变。场效应测试结果表明,C₆₀薄膜的迁移率与其结晶性密切相关,高的结晶性有利于获得高迁移率;不同于平面有机半导体材料,对于球状C₆₀半导体材料,大的晶粒尺寸可能导致低迁移率。     

Pt／Ti／Si3N4／SiO2／Si基底的多层薄膜制备及拉曼研究

选用三水醋酸铅、乙酰基丙酮酸锆、四异丙氧基钛、乙酰丙酮作初始材料,用同样的方法分别制备了锆钛酸铅（PZT）和钛酸铅（PT）两种固体前驱物．采用改良型的溶胶-凝胶工艺技术,分别在不同的Pt-Ti-Si3N4-SiO2-Si基底上,按照不同的组合方式,制备了三种多层薄膜：PZT、PT／PZT—PZT／PT、PT／PZT／-／PZT／PT．较详细地讨论了薄膜制备的工艺技术,发现当凝胶通过烧结和干燥后变成固态物质时,薄膜内部存在着较大的残余应力,当薄膜在600℃下退火时其内部残余应力可以被减小．通过拉曼衍射和XRD分析,发现PT／PZT—PZT／PT结构的薄膜具有较好的结晶性和较小的残余应力．XRD分析表明,多层混合薄膜的衍射峰是PZT和PT两种薄膜衍射峰的叠加．     

等离子体增强MOCVD法生长ZnO薄膜

利用等离子体增强MOCVD法生长出 ZnO薄膜，用X射线衍射谱观察到位于 2θ34．56°处（0002）的衍射峰，表明ZnO沿c方向呈柱状生长．通过荧光光谱，观察到来自于激子的高强度的近带边紫外光发射（375um）．紫外发射光强度与深能级复合发射光强度比高达 193，显示出材料的高质量，并通过原子力显微镜加以验证．为了实现高阻ZnO薄膜，利用高温富氧分段退火和用N2 气进行掺氮两种方法生长高阻ZnO薄膜．结果表明，电阻率由0．65 Ω·cm分别升高到1100 Ω·cm（分段退火）和5×104Ω·cm（掺氮）．进一步比较发现，掺氮的样品不仅电阻率高，而且光荧光特性好，显示出更高的薄膜质量．     

直流负偏压对类金刚石薄膜结构的影响

在不同的直流负偏压下利用直流射频等离子体辅助化学气相沉积技术在单晶硅表面沉积得到了类金刚石薄膜,用拉曼光谱、红外光谱和原子力显微镜对薄膜的结构和形貌进行了表征.结果表明:无偏压时,沉积得到的薄膜呈现类聚合物结构且表面比较粗糙,而叠加了偏压后,薄膜表现出类金刚石薄膜的结构特征,随着偏压的增大,膜中的氢含量和sp3碳含量均逐渐减小,且薄膜的表面粗糙度逐渐减小.     

溶胶-凝胶法制备的MgxZnl—xO纳米薄膜结构和光学性质

用溶胶-凝胶法制备了不同组分的MgxZn1-xO薄膜．X射线衍射结果表明，薄膜为具有六角纤锌矿结构的纳米薄膜，晶粒尺寸3～5nm，随着Mg进入ZnO晶格，其晶格常数变小．紫外-可见吸收光谱表明，随着Mg含量的增加带隙变宽，自由激子吸收峰明显蓝移．室温光致发光光谱由很强的且与氧空位相关的深能级缺陷发光和较弱的紫外激子发光组成，激子发光强度和缺陷发光强度比随x的增大而减小，表明Mg原子进入ZnO晶格会引起深能级缺陷的增加．Mg0.03Zn0.97O薄膜经700℃热氧化后，紫外与可见发光强度比达到30．     

Structural and Optical Properties of ZnO Films with Different Thicknesses Grown on Sapphire by MOCVD

IntroductionZnOis one of the most promising materials for pro-ducing ultraviolet laser at room temperature because ofits wide direct band gap(Eg=3.37eV)and large ex-citonic binding energy of60meV.Recently,much at-tention has been paid to short-wavelength …     

Preparation of nitrogen doped zinc oxide nanoparticles and thin films by colloidal route and low temperature nitridation process

Nitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO₂ substrate from a ZnO colloidal solution. Zinc peroxide (ZnO₂) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H₂O₂ solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250 °C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV–Visible transmittance spectroscopy.     

Interfacial interaction between ZnO thin film and polyimide substrate investigated by XPS and DFT calculation

The interfacial interaction between the ZnO film and the polyimide substrate was investigated by XPS and density functional theory (DFT) calculation, for the ZnO thin films deposited on polyimide (PI) substrates using cathodic vacuum arc deposition technique. The XPS results showed that a shoulder peak was present for the ZnO film with the thickness of about 15 nm, used for depth profiling, at the binding energy 1 eV higher than that of the Zn2p3 core level for bulk ZnO. Such a shoulder peak is attributed to the interaction between the ZnO and the polyimide. This agrees with the results of DFT calculation. Furthermore, the difference in adsorption energy between the polyimide monomer and the ZnO molecule at different adsorption sites showed that the carbonyl (C?O) plays an important role in the interfacial strength. Copyright © 2011 John Wiley & Sons, Ltd.     

Inverted polymer solar cells with a solution-processed zinc oxide thin film as an electron collection layer

A solution-processed zinc oxide (ZnO) thin film as an electron collection layer for polymer solar cells (PSCs) with an inverted device structure was investigated. Power conversion efficiencies (PCEs) of PSCs made with a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) are 3.50% and 1.21% for PSCs with and without the ZnO thin film, respectively. Light intensity dependence of the photocurrent and the capacitance-voltage measurement demonstrate that the increased PCEs are due to the restriction of the strong bimolecular recombination in the interface when a thin ZnO layer is inserted between the polymer active layer and the ITO electrode. These results demonstrate that the ZnO thin film plays an important role in the performance of PSCs with an inverted device structure.     

Photoinduced charge transfer in ZnO/Cu(2)O heterostructure films studied by surface photovoltage technique

ZnO/Cu(2)O heterostructure films were prepared by a two-step electrodeposition method in aqueous solution on fluorine-doped tin oxide (FTO) substrates. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and UV-vis transmission measurements were utilized to characterize the films. Surface photovoltage (SPV) technique was used to investigate the process of photoinduced charge transfer. The results show that there is an electric field located at the interface between ZnO and Cu(2)O film and the photoinduced electrons in Cu(2)O film inject into ZnO under the effect of interfacial electric field with visible light irradiation. While under ultraviolet light illumination, the photoinduced electrons in Cu(2)O film accumulate at the surface of Cu(2)O film instead of injecting into ZnO under the action of surface built-in electric field of Cu(2)O film. The work function measurements confirm that the direction of interfacial electric field is from ZnO to Cu(2)O. These results are help to future design of high performance heterostructure photovoltaic devices.     

Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to S_n ^2? reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO₂) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO₂ thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO₂ thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.     

温度对α-Al2O3(0001)表面吸附生长ZnO影响的DFT研究

The adsorption and the growth of ZnO on α-Al2O3(0001) surface at various temperatures were theoretically calculated by using a plane wave pseudopotentials (USP) method based on density functional theory.The average adsorption energy of ZnO at 400, 600 and 800 ℃ is 4.16±0.08, 4.25±0.11 and 4.05±0.23 eV respectively. Temperature has a remarkable effect on the structure of the surface and the interface of ZnO/α-Al2O3(0001). It is found that the Zn-hexagonal symmetry deflexion does not appear during the adsorption growth of ZnO at 400 ℃, and that the ZnO10-10 is parallel with the 10-10 of the α-Al2O3(0001), which is favorable for forming ZnO film with the Zn-terminated surface. It is observed from simulation that there are two kinds of surface structures in the adsorption of ZnO at 600 ℃: one is the ZnO surface that has the Zn-terminated structure, and whose 10-10 parallels the 10-10 of the substrate surface, and the other is the ZnO10-10 //sapphire 11-10 with the O-terminated surface. The energy barrier of the phase transition between these two different surface structures is about 1.6 eV, and the latter is more stable. Therefore,the suitable temperature for the thin film growth of ZnO on sapphire is about 600 ℃, and it facilitates the formation of wurtzite structure containing Zn-O-Zn-O-Zn-O double-layers as a growth unit-cell. At 600 ℃, the average bond length of Zn-O is 0.190±0.01 nm, and the ELF value indicates that the bond of (substrate)-O-Zn-O has a distinct covalent character, whereas the (Zn)O-Al (substrate) shows a clear character of ionic bond. However, at a temperature of 800 ℃, the dissociation of Al and O atoms on the surface of the α-Al2O3(0001) leads to a disordered surface and interface structure. Thus, the Zn-hexagonal symmetry structure of the ZnO film is not observed under this condition     

The effects of oxygen concentration on ultraviolet luminescence of ZnO films by sol–gel technology and annealing

ZnO thin films were successfully deposited on SiO₂/Si substrate using the sol–gel technique and annealed in various annealing atmospheres at 900 °C by rapid thermal annealing (RTA). X-ray diffraction revealed the (002) texture of ZnO thin films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the grains of the ZnO thin film were enlarged and its surface was smoothed upon annealing in oxygen. PL measurement revealed two ultraviolet (UV) luminescence bands at 375 and 380 nm. The intensity of the emission peak at 380 nm became stronger as the concentration of oxygen in the annealing atmosphere increased. The X-ray photoelectron spectrum (XPS) demonstrated that a more stoichiometric ZnO thin film was obtained upon annealing in oxygen and more excitons were generated from the radiative recombination carriers consistently. Additionally, the UV intensity increased with the thickness of ZnO thin film.     

Forming extremely smooth ZnO thin film on silicon substrates for growth of large and well-aligned ZnO rods with the hydrothermal method

Sol–gel zinc oxide (ZnO) thin films generally have non-uniform stripes. After annealing at high temperatures, these thin films are rough and granular. When ZnO rods are grown on such rough and non-uniform surface with the hydrothermal method, collimation, crystalline structure, and defect density are very poor. Here we explore a method to solve this problem. The ZnO thin film is first coated with an Au layer to prohibit the vertical extension of crystallization during the annealing period. As a result, the surface morphology of ZnO thin film is very flat and uniform after annealing. Afterwards, the ZnO rods are grown on the flat and uniform thin film, which gives rise to ZnO rods with very good collimation and crystalline structure. The extremely flat ZnO thin film even enables the fabrication of patterned ZnO rod arrays with regular shapes through lithography.