Studies on Structure and Growth of Ce Thin Films on a Mo(110) Surface.

Abstract

The surface structures and growth mode of Ce thin films on Mo (110) surface were investigated by reflection high-energy electron diffraction. Five kinds of two-dimensional superstructures of ( ), ( ), ( ), ( ) and ( ) and one kind of one-dimensional structure were found with Ce submonolayers. All of these structures show a common periodicity of √2 a0Mo along Mo [110] direction. This periodicity is considered to be very stable and dominant in case of the submonolayer coverage of Ce thin films on the Mo (110) surface. Cerium grows in accordance with the Stranski-Krastanov growth mode in which two Ce monolayers grow initially in the substrate temperature range from 500 to 800°C. The Ce two-dimensional layers are composed of a distorted fcc γ-Ce (111) layer and a fcc γ-Ce (111) layer for the 1st and the 2nd layers, respectively. The first Ce mono-layer is expanded by 7.8% in [110] direction and 5.6% in [112] direction compared with the fcc γ-Ce (111) layer.