阳极氧化法制备多孔硅中的正电子湮没及扫描电子显微镜研究

摘要

用正电子湮没技术和扫描电子显微镜研究了阳极氧化法制备的多孔硅材料。正电子湮没实验表明，随着阳极氧化时间的延长，平均寿命值增大，空位缺陷增多。长寿命(正电子素)成分较少。扫描电子显微镜显示，在阳极氧化过程中有尺寸为几μm的单晶球形成。并观察到部分单晶球脱离后形成的微米坑。空位缺陷增多的原因可能是随着阳极氧化时间的延长，多孔硅结构向内层延伸增加了空位缺陷。但扫描电子显微镜的观察结果并不排除另一种可能部分表面结构的变化增大了表面层的空位缺陷浓度。%In this report, the porous silicon formed by anodization of crystal silicon was studied by positron annihilation technique (PAT) and scanning electron microscopy (SEM). The PAT experiments showed that the mean life and vacancy defects increased with the increasing anodization time. While the intensities of the longest lifetime, several ns~tens ns (orth-positronium) droped down. Small single-crystal Si spheres with mean radius of a few μm were observed by SEM after anodization. Pits with mean radius of a few μm from the divorcement of single-crystal spheres were also observed after further anodization. The increases of vacancy defects might be that the extension of structures of porous silicon towards inner layer with anodization time and caused more vacancy defects in inner layer. Our SEM observation presented another possibility of the increase of density of vacancy defects in surface layer induced by the change of structures.