Buried H monolayer at hetero-interface between highly mismatched Sr films and Si substrates

Yamazaki, Tatsuya; Asaoka, Hidehito  ; Takeda, Masayasu  ; Yamazaki, Dai  ; Taguchi, Tomitsugu; Torikai, Naoya*; Toyoshima, Yasutake*; Shamoto, Shinichi  

Strontium and SrO are well-known templates on Si for SrTiO, highly-desirable transistor gate material. When stacked on Si, Srlayer becomes amorphous due to its large lattice mismatch of 12%. By introducing a monatomic hydrogen layer on Si, we succeeded in making the Sr (and subsequent SrO) layer(s) grow epitaxially with atomically abrupt interface. However, it is some what mysterious how the monatomic hydrogen layer behaves to manage this large mismatch. In order to identify its behavior, we have employed compound analysis by neutron reflectometer as well as multiple-internal-reflection fourier-transform infrared spectroscopy (MIR-FTIR) to investigate the buried heterointerface of Sr grown on Si(111)11: monohydride. We have found difference between the H- and D-terminated substrates in the reflectivity profiles, and changes in Si-H bonding features with the Sr growth (mainly at the initial monolayer stage) in the FTIR spectra. From these, existence of buried H layer at the heterointerfaceis confirmed with its bonding environment.