Growth of CdF2CaF2Si(111) heterostructure with abrupt interfaces by using thin CaF2 buffer layer

The minimum thickness of CaF2 buffer layer in CdF2/CaF2/Si(111) heterostructure to grow CdF2 epitaxialy on Si(111) under less stringent vacuum conditions (∼ 10−8 Torr) was found to be 0.9 nm. Chemical reaction and growth mode at the initial stage of growth of CdF2 layer on Si(111) and on CaF2Si(111) were studied with the in-situ X-ray photoelectron spectroscopy method. It was found that oxygen-related, chemical reaction of the CdF2 occurred on the Si(111) surface, but not on the CaF2(111) surface. Two-dimensional growth of CdF2 layer from the initial stage was observed on the CaF2 buffer layer. These results indicate that the CaF2 buffer layer plays a role as a barrier layer to chemical reaction between the CdF2 and the Si substrates. A short-period CdF2CaF2 superlattice was grown on CaF2Si(111) and the XRD showed satellite peaks which is consistent with the growth rate. This result shows that the structure has abrupt interfaces with less than a few monolayers.