Growth of thin films of refractory silicides on Si(100) in ultrahigh vacuum

Abstract

Thin films (30–150 nm thick) of tungsten and molybdenum silicide were grown by evaporation under ultrahigh vacuum conditions on Si(100) substrates cleaned according to the classical procedures used in silicon molecular beam epitaxy. Two methods for silicide formation were studied: (1) metal deposition onto substrates at room temperature followed by in situ annealing; (2) metal deposition onto heated substrates at temperatures ranging between 600 and 800°C, i.e. higher than the threshold temperature for silicide formation (in this case the silicide grows during the evaporation of the metal). Excellent values of the resistivity were obtained in both cases despite the low annealing temperature and the thickness of the silicide layers. These results are discussed in terms of the crystal structure of the silicides observed using transmission electron microscopy. It was found that silicides produced by the second process grew epitaxially on Si(100).