Mg_xZn_(1-x)O单晶薄膜的分子束外延生长及结构表征

Growth and characterization of MgxZn1-xO single -crystal thin films by plasma assisted molecular beam epitaxy

用等离子辅助分子束外延(P-MBE)的方法,在蓝宝石c-平面上外延生长了Mg_xZn_(1-x)O合金薄膜。在0≤x≤0.2范围内Mg_xZn_(1-x)O薄膜保持着六角纤锌矿结构不变。原位反射式高能电子衍射图样和X射线双晶衍射谱的结果表明生长的样品是单晶薄膜。随着x值逐渐增大,Mg^(2+)离子逐渐进入ZnO的晶格,X射线双晶衍射测得样品的(002)取向的半高宽度从0.249°增加到0.708°,表明结晶质量逐渐下降,(002)方向的X射线衍射峰向大角度方向移动,晶格常数c由5.205减小到5.185。透射光谱的结果表明,合金薄膜的吸收边随着Mg离子的掺入逐渐向高能侧移动,室温光致发光谱出现很强的紫外发光(NBE)峰,没有观察到深能级(DL)发射,且随着Mg掺入量的增加,紫外发光峰有明显的蓝移,这与透射光谱的结果是相吻合的。

MgxZn1 - xO alloy thin films were fabricated on c -plane sapphire (Al2O3) substrates by plasma assisted molecular beam epitaxy (P - MBE). The films with different composition x, which is changed from 0 to 0. 20, keep wurtzite crystal structure measured by X - ray diffraction (XRD). Reflection high -energy electron diffraction (RHEED) and X -ray double crystal diffraction spectra show that the samples are single - crystal films. As x value is increased from 0 to 0. 20, the full width at half maximum (FWHM) of (002) - oriented ZnO X - ray rocking curve is broadened from 0. 249° to 0. 708° and the lattice constant of c - axis is decreases from 5. 205A to 5. 185A. The absorption edges of alloy thin films show the blue shifts with increasing x value in the transmission spectra at room temperature (RT). Photoluminescence (PL) spectra at RT exhibit an intense ultraviolet emission, which shifts to high - energy side with increasing x values, and the deep level emission are not observed. The above results indicate that high quality single - crystal MgZnO thin films are fabricated by P - MBE.