Epitaxial growth of LaAlO_3 on Si(001) using interface engineering

摘要

In this work, the potentiality of molecular beam epitaxy techniques to prepare epitaxial lanthanum aluminate (LaAlO_3) films on Si(001) is explored. We first demonstrate that the direct growth of LaAlO_3 on Si(001) is impossible : amorphous layers are obtained at temperatures below 600℃ whereas crystalline layers can be grown at higher temperatures but interfacial reactions leading to silicate formation occur. An interface engineering strategy is then developed to avoid these reactions. SrO and SrTiO_3 have been studied as buffer for the subsequent growth of LaAlO_3. Only partial LaAlO_3 epitaxy is obtained on SrO whereas high quality layers are achieved on SrTiO_3. However both SrO and SrTiO_3 appear to be unstable with respect of Si at the growth temperature of LaAlO_3 (700℃). This leads to the formation of relatively thick amorphous interfacial layers. Despite their instability at high temperature, these processes could be used for the fabrication of twins-free LaAlO_3 templates on Si, and for the fabrication of complex oxide/Si heterostructures for various applications.