Epitaxial growth of CaF2 films on Si(111) studied by STM

K. Kametani, K. Sudoh and H. Iwasaki

The Institute of Scientific and Industrial Research, Osaka University
8-1 Mihogaoka, Ibaraki, 567-0047, Japan

Growth of CaF2 on Si(111) has been extensively studied to realize an epitaxial insulator film with atomically abrupt interface. In this study, we have investigated the CaF2 growth on Si(111) using scanning tunneling microscopy. Samples were prepared at 630 oC by evaporation of CaF2 at the rather low growth rate of 0.2 monolayer/min. After the completion of CaF layer [1], we observe assemblies of one-dimensional CaF2 islands along one of the <10> directions of the substrate with monolayer height and with three different widths where 1, 2, and 3 CaF2 molecules align. With increasing CaF2 coverage, the density of the one-dimensional islands becomes high, and then a smooth CaF2 layer is eventually completed.

[1] M.A. Olmstead, in Thin Films: Heteroepitaxial Systems, edited by W.K. Liu and M.B. Santos (World Scientific, Singapore, 1999).