Structural and phase transformations during initial stages of copper condensation on Si(001)

Abstract

Auger-electron spectroscopy, electron-energy loss spectroscopy, low-energy electron diffraction, and atomic-force microscopy are employed to investigate the growth mechanism, composition, structural and phase states, and morphology of Cu films (0.1–1 nm thick) deposited on a Si(001)-2 × 1 surface at a lower temperature of Cu evaporation (900°C) and room temperature of a substrate. The Cu film phase is shown to start growing on the Si(001)−2 × 1 surface after three Cu monolayers (MLs) are condensed. It has been revealed that atoms of Cu and Si(001) are mixed, a Cu2Si film phase is formed, and, thereafter, Cu3Si islands arise at a larger coating thickness. Annealing of the first Cu ML leads to reconstruction of the Si(001)-1 × 1-Cu surface layer, thereby modifying the film growth mechanism. As a consequence, the Cu2Si film phase arises when the thickness reaches two to four MLs, and bulk Cu3Si silicide islands begin growing at five to ten MLs. When islands continue to grow, their height and density reach, respectively, 1.5 nm and 2 × 1011 cm−2 and the island area is 70% of the substrate surface at a thickness of ten MLs.