Localized epitaxial growth of ReSi₂ on (111) and (001) silicon

Abstract

Epitaxial ReSi2 has been grown locally on (111) and (001)Si. The best epitaxy was obtained in samples after two-step annealing at 500-1100 °C. In (111) samples, the orientation relationships were analyzed to be [110]ReSi2//[111]Si and (002)ReSi2//(2̄02)Si. About 70% in areal fraction of the epitaxial regions were found to be pseudomorphic. In (001) samples, two different modes of epitaxial silicides were observed: [110]ReSi2//[001]Si and (1̄10)ReSi2//(22̄0)Si (mode A') and [110]ReSi2//[001]Si and (1̄12̄)ReSi 2//(220)Si (mode B'). About 40% and 60% in areal fractions of the mode A' and mode B' epitaxial ReSi2 regions, respectively, were found to be pseudormorphic. The apparent insensitivity of the quality of the ReSi2 epitaxy to the lattice matches at silicide/silicon interfaces at room temperature may be explained in part by the considerable changes in lattice mismatches at the growth temperature arising from the substantial difference in thermal expansion coefficients between the ReSi2 overlayer and the substrate silicon. The results are in agreement with a theory which predicts that orientations with negative mismatches are favored for epitaxial growth over orientations with positive mismatches.