B掺杂ZnO透明导电薄膜的实验及理论研究

采用脉冲直流磁控溅射技术与基于密度泛函理论的平面波赝势方法对B掺杂ZnO （BZO）薄膜进行了研究. 以B₂O₃：ZnO陶瓷靶为溅射靶材，制备了低电阻率、可见和近红外光区高透过率的BZO薄膜. 系统地研究了衬底温度对BZO薄膜的结构、光电特性的影响. 结果表明：适当的增加衬底温度可以促进BZO薄膜结晶质量改善，晶粒尺寸增加，迁移率增大，电阻率降低. 在200 ℃时制备了电阻率为7.03×10^-4 Ω·cm，400–1100 nm平均透过率为89%的BZO薄膜. 理论模拟结果表明：在BZO薄膜中，以替位方式掺入的B （B_Zn）的形成能最低，B主要以替位形式掺入ZnO，其次分别为八面体间隙（B_IO）和四面体间隙（B_IT）的掺杂方式. B 掺入后，费米能级穿过导带，材料表现出n型半导体特性，光学带隙展宽，导电电子主要来源于B 2p，O 2p及Zn 4s电子轨道. 关键词： BZO薄膜 第一性原理计算 磁控溅射 太阳电池

Experimental and theoretical investigation of transparent and conductive B doped ZnO film

The properties of boron doped ZnO (BZO) films are investigated by the pulsed DC magnetron sputtering technique and the plane wave pseudo-potential method based on the density-functional theory. Highly conductive and transparent BZO thin films are prepared using a B₂O₃:ZnO ceramic target. The effects of the substrate temperature on the structureand electrical and optical properties are systematically investigated. The results show that by increasing the substrate temperature appropriately, the crystallinity, grain size, and carrier mobility of BZO film are improved, and the resistivity is reduced. BZO films of low resistivity (7.03×10^-4 Ω·cm) and high transmittance (89%) from 400–1100 nm are achieved at an optimal substrate temperature of 200 ℃. The theoretical results show that B is doped in ZnO mainly in three forms, i.e., in the forms of substitutional B_Zn atoms, octahedral interstitial site (B_IO), and tetrahedral interstitial site (B_IT). Among them the formation energy of B_Zn defect is lowest, and its concentration may be the highest in all the sample concentrations. After incorporation of B, the Fermi level goes through the conduction band. The sample shows a typical n-type metallic characteristic and the optical band gap increases significantly. The carriers originate from the orbits of B 2p, O 2p and Zn 4s.
Keywords： BZO film first principles calculations magnetron sputtering solar cells