LMBE法生长ZnO薄膜的结构和光学性能

Structure and optical properties of ZnO thin films grown by laser molecular beam epitaxy

利用激光分子束外延方法(LMBE)在单晶Si(100)和玻璃基片上生长了ZnO薄膜。通过XRD谱、拉曼光谱和光致发光(PL)谱研究了ZnO薄膜的结构和光学性能。结果表明,ZnO薄膜具有六方纤锌矿结构,(002)衍射峰较强,c轴择优取向良好。在可见光范围,ZnO薄膜的平均透射率>80%,而在紫外范围,平均透射率急剧降低。拟合得到ZnO薄膜的禁带宽度为3.31eV。随激发波长增加,PL谱峰位没有变化,但强度发生了变化。同时,随测量温度升高,紫外发光峰强度减弱,峰位红移,半高宽展宽。理论拟合得到ZnO薄膜的活化能为59meV,接近于ZnO体材料的激子束缚能(60meV),说明紫外发光是由自由激子辐射复合引起的。

The ZnO thin films were grown by laser molecular beam epitaxy （LMBE） on both Si（100） and glass substrate,and then the structure and optical properties of ZnO films were investigated by using X-ray diffraction spectra,Raman spectra and Photoluminescence （PL） spectra,respectively. The results show that ZnO thin films form a hexagonal wurtzite structure and display a preferential c-axis （002） orientation. The average transparency is larger than 80% with the scope of the visible light, while the average transparency drops quickly with the scope of the ultraviolet （UV） light. Through fitting,the band gap of ZnO films was obtained to about 3.31 eV, which is smaller than that of bulk ZnO. With the increment of excited wavelength, the peaks location has no change but the peaks＂ intensity changes in PL spectrum. In addition,as the measuring temperature increases the intensity of UV emission decreases and the location of UV peaks shifts to larger wavelength as well as the full width at half maximum （FWHM） enlarges. The activation energy was obtained to be about 59 meV through theoretical fitting,which is close to that of bulk ZnO,indicating that UV emission originates from the recombination of free exciton.