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.

Preparation and Properties of Zinc Oxide Films by Spin-Coating Water Solution Precursor

We successfully prepared ZnO thin films through spin-coating a mixture of zinc acetate dihydrate,poly (ethylene oxide) (PEO) and deionized H2O.Smooth and pure ZnO thin films were obtained by using PEO,because of its low thermal decomposition temperature.The morphology,crystallinity,band gap energy (Eg),and conductivity of the ZnO thin films annealed at different temperatures were determined.Atomic force microscopy (AFM) showed that the root mean square (rms) surface roughness of films annealed at 400,450,and 500℃ was 3.3,2.7,and 3.6 nm,respectively.TEM images showed that the ZnO films were composed of ZnO nanocrystals.The band gap energy (Eg) for the films was calculated as 3.3 eV from the absorption edge at 373 nm.From their current-voltage (I-V) curves the resistivities of ZnO thin films annealed at 400,450,and 500℃ were calculated as 3.3×109,2.7×109,and 6.6×109 Ω·cm,respectively.High annealing temperature is useful in improving purity and density of the film and increasing adsorbed oxygen on the film.The film with high purity and density will exhibit low resistivity.The film with more adsorbed oxygen will exhibit high resistivity,due to higher grain boundary barrier.Consequently,the ZnO thin film annealed at 450℃ exhibited the lowest resistivity,while the ZnO thin film annealed at 500℃ had the highest resistivity.