主要研究了氢掺杂氧化锌(ZnO∶H)薄膜的性能,发现随着H2流量比的变化,其主要表现为浅施主掺杂、钝化空位缺陷以及刻蚀等作用。当H2流量比较小时(R≤0.02),样品沿(002)择优向生长,这时H原子主要作为浅施主掺杂,钝化氧空位和取代锌离子,使晶胞体积变小,提高ZnO薄膜的结晶性,同时使得ZnO带尾变窄,带隙变宽;SEM图观察到薄膜表面粗糙,晶粒变大、且分布均匀;薄膜电阻率下降,主要是薄膜结晶质量提高增加了电子迁移率及浅施主掺杂提高了电子浓度。当H2流量比较大时(R≥0.04),样品XRD(002)衍射峰淬灭,晶胞体积变大,薄膜结晶度降低。从红外吸收谱可以看出,在3400~3900cm-1范围,出现一个较宽的吸收带,这属于典型的O—H键区域振动模式(LVM)吸收带。由于极性分子团羟基造成电荷不平衡,产生氧空位,提高电子浓度,使薄膜电阻率降低。同时,由于刻蚀作用使得缺陷浓度增加,带尾变宽,使得薄膜带隙变窄。
This paper investigated the properties of ZnO : H thin films. We found that hydrogen played an important role on structural and properties of ZnO : H thin films. With the changing of H2 flow ratio, the effects of H doping manifested as passivating vacancy defects, shallow donor doping and etching action. When the H2 flow ratio (R-H2/ (H2 + Ar)40.09.) was low, samples grown along the (002) preferential orientation. In this condition, H+ did mainly play a role of shallow donor doping of passivating oxygen vacancies and substituting zinc ion, so the unit cell volumes became smaller and the crystallinity of ZnO : H thin films increased; in addition, H+ passivated oxygen vacancies, which made the band tails became narrower, so the optical band gap became wider; we could observe the grains size became bigger and homogeneous distribution on the rough films surface from the SEM figure; besides, the resistivity of thin film decreased, which was mainly attributed to the electron mobility increased from the erystallinity increasing and the electron concentration increased from the shallow donor doping. When the flow ratio was more than 0.04 (R〈0.04), the (002) peak of XRD quenched, the unit cell volumes became bigger and the quality of crystallization decreased. In the FT-IR spectra, which was observed an absorption band at 3400-3900 cm-1. It exhibited to the typical O--H bonding local vibrational modes (LVM) absorption band. Owing to the charges unbalance was caused by polar molecular clusters (hydroxy) in the high doping concentration, which produced a mass of oxygen vacancies and increased the electron concentration, so it led to the decreasing of the film resistivity. In this condition, the optical band gap Became narrower, which caused by the H+ etching action.