Interface characterization of SrTiO3/Sr/Si heterostructure through X-ray reflectivity

Abstract

The growth of hetero-epitaxial strontium titanate (SrTiO3) on single-crystal silicon (Si) substrate is of considerable scientific interest because of its wide range application. Unlike other hetero-epitaxial systems, there exists a fairly large lattice mismatch between SrTiO3 and Si. This leads to the possibility of strain in SrTiO3 thin film. In order to prevent the formation of amorphous SiO2 phase and interdiffusion of component atoms at the interface, an ultrathin strontium (Sr) layer is deposited on the underlying Si-substrate. The X-ray diffraction (XRD) is used for characterization of hetero-structures. In this paper, we report the characterization of SrTiO3 thin film on Si (100) substrate with Sr interlayer by a variety of X-ray measurements. Based on the data obtained from SrTiO3 thin film, the growth characteristics of the sample is objectively appreciated. The sample is prepared by laser molecular beam epitaxy (L-MBE) under optimized conditions of substrate temperature and oxygen pressure. 2θ/ω scan indicates a high crystallization quality and epitaxial grown of SrTiO3 thin film in the nanometre scale. Θ-scans have further revealed the in-plane orientation relationship between SrTiO3 and Si. The α- and c- lattice parameters of the SrTiO3 thin film are found to be 0.3898, and 0.3901 nm, respectively, which suggests a slight elastic distortion. More detailed investigations by X-ray reflectivity have therefore been carried out, in order to get better understanding to the effect of the buried heterointerface.