异质外延MgO/SrTiO_3薄膜中界面应力研究

Interfacial Strain in Heteroepitaxial Growth of MgO/STO Thin Film

本文利用激光分子束外延 (LMBE)技术在SrTiO3 (10 0 )单晶基片上外延生长MgO薄膜 ,同时又在MgO(10 0 )单晶基片上外延生长SiTiO3 (STO)薄膜。通过反射高能电子衍射 (RHEED)仪原位实时监测薄膜生长 ,研究薄膜的生长过程。并结合X射线衍射 (XRD)仪来分析在不同的生长条件下 ,不同应力对薄膜外延生长的影响。在压应力情况下 ,MgO薄膜在STO基片上以单个晶胞叠层的方式生长 ,即以“CubiconCubic”方式进行外延 ;在张应力情况下 ,由于膜内位错较多 ,STO薄膜在MgO基片上以晶胞镶嵌的方式进行生长 ,即以“Mosaic”结构进行外延 ;提高生长温度 ,可以减少膜内位错 ,提高外延质量 ,使STO薄膜在MgO基片上以较好的层状方式外延生长。

Epitaxial thin films of MgO have been grown on SrTiO3(100) single-crystal substrate and SrTiO3 (STO) thin film has been grown on MgO(100) single-crystal substrate by laser molecular beam epitaxy (LMBE), respectively. The growth process of the films was in situ monitored by reflective high energy electron diffraction (RHEED). X-ray diffraction (XRD) 2θ-ω scan and φ scan were used to analyse the orientation and epitaxial relation of the films. Under stress, MgO grows in a cubic-on-cubic way on the STO substrate in the mode of MgO//STO. In contrast, with the tensile stress, STO grows with special mosaic structure on MgO substrate, while its epitaxial quality improves at a higher temperature, say 800°C.