利用脉冲激光沉积法制备高Mg掺杂的六方相MgZnO薄膜

Heavily Mg-doped Hexagonal Phase Thin ZnO Films Prepared by Pulsed Laser Deposition

选用Mg0.2Zn0.8O陶瓷靶,利用脉冲激光沉积(PLD)法,在单晶Si(100)和石英衬底上生长了一系列MgZnO薄膜(MZO)。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(EDS)和紫外可见光透射光谱(UV-Vis)等实验手段,研究了在不同工作压强下生长的薄膜样品的晶体结构、微观形貌和光学性能的变化。结果表明:所有的薄膜样品都是单一的ZnO六方相,禁带宽度随生长压强的升高而增加,变化范围在3.83～4.05eV之间,最短吸收边接近300nm。

As an important candidate material for photoelectric devices such as ultraviolet detector,thin MgxZn1-xO films （MZO） have been recently given extensive attention.Most studies have been focused on changing target compositions to prepare MZO with absorption edge in the solar-blind region （220～280 nm）.However,the mix phases of hexagonal ZnO and cubic MgO appear when the Mg concentration increases to certain percentage.For different growing technologies and parameters,different limits of Mg concentration have been reported to keep MZO single hexagonal phase.Besides,the Mg content in the prepared thin films often deviates from the targets according to most studies.In this paper,a series of thin MZO films were prepared with different growing pressure on the Si（111） and quartz substrates by using Mg0.2Zn0.8O target and pulsed laser deposition （PLD） method in order to adjust the Mg content in the prepared MZO samples.The crystal structures,micro-morphologies and optical properties were characterized by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,X-ray energy dispersion spectra （EDS） and ultraviolet-visible absorption spectra.The EDS results showed that the Mg concentrations in the prepared samples change from 44.5% to 48.5% with the growing pressure from 5.2×10^-4 Pa to 0.3 Pa,much higher than that in the target.But all the thin films still show single hexagonal phase according to the XRD results.We suggested that the increase of Mg content in the thin films is due to the stronger binding force of Mg-O compared to Zn-O in the oxygen-deficient growing environment.The band-gap of the thin films increases from 3.83 eV to 4.05 eV with the increasing Mg content,which can be estimated from the transmittance spectra.Among all the MZO samples,the 48.5% Mg sample has the shortest absorption edge which is close to 300 nm,quite near the solar-blind region.This work would be helpful for the preparation of solar-bind thin MZO films with single phase.