In situ studies of epitaxial growth in the low energy electron microscope

Abstract

The epitaxial growth of Cu on Mo{110}, Au on Mo{110}, Cu on Si{111} and Au on Si{111} is studied in situ in the ultra high vacuum low energy electron microscope. Nucleation at atomic steps and defects is seen, and submonolayer growth is followed. Domains and domain boundaries within single terraces are resolved. The monolayer of Cu is pseudomorphic with the Mo{110} substrate, whereas the double layer is in the Nishiyama-Wassermann orientation with the Cu(111)∥Mo(110) and Cu[1 1 0]∥Mo[001]. At 700 K the Cu double layer is coherent along Mo[001] and grows with a needle-like habit in this direction. The Au monolayer grows in the Kurdjumov-Sachs orientation with Au(111)∥Mo(110) and Au[1 1 0]∥Mo[1 1 1]. At low temperatures Au forms rows along Mo〈111〉 and grows with a needle-like habit in these directions. Cu grows on Si{111}(7×7) as a silicide monolayer followed by three-dimensional islands with sides aligned along Si〈110〉. Atomic steps often bunch together into groups of three and facet along Si〈110〉. In the growth of Au on Si{111} at elevated temperature the (5×1) structure forms elongated islands oriented along Si〈110〉, which is accompanied by two-dimensional faceting of atomic steps along Si〈110〉. Step bunching, which causes three-dimensional microfaceting, leads to a loss of smoothness of the Si substrate.