Heteroepitaxy of SrTiO3 thin films on Si (001) using different growth strategies: Toward substratelike quality

Different molecular beam epitaxy (MBE) strategies for fabricating SrTiO3(STO) thin films on Si (001) substrates are described and compared. The resulting STO structural quality (crystallinity, surface roughness, and interface sharpness) is systematically analyzed depending on growth conditions. In particular, the authors show that sharp STO/Si interface and good STO structural quality can be obtained up to the plastic relaxation critical thickness by using direct STO epitaxy in a narrow (low temperature and low oxygen partial pressure) growth window. For thicker films, two-step strategies (STO buffer grown under moderately oxidizing conditions and further STO growth carried out at higher temperature and oxygen partial pressure) must be preferred: they allow for obtaining fully relaxed STO layers having optimal structural qualities, at the expense of the formation of a thin amorphous interface layer. The impact of the STO buffer growth conditions on the overall quality of the layer is described and it is shown that excellent STO structural quality can be achieved by using convenient growth conditions. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3609813]