Scanning tunneling microscopy of SiGe alloy surfaces grown on Si(1 0 0) by molecular beam epitaxy

An investigation into the surface structure and morphology that results from the growth of SiGe alloys with 0%, 5%, 10%, and 20% Ge bulk concentration at 500 and 800 °C on Si(1 0 0) is presented. Stages of alloy growth are reported from the initial Si–Ge intermixing to the segregation of Ge from the alloy to the final 2D island surface morphology. Surface Ge produces a “2×n” surface reconstruction, which is shown to result from a mixture of local atomic orderings of c(4×2) and p(2×2) that varies with alloy concentration. The alloy surfaces are characterized by 2D island growth, where the surface roughness is observed to increase with increasing Ge concentration and with increasing growth temperature. A discussion of the effects of adatom mobility, compressive strain, step-edge attachment, and surface reconstruction involved in 2D island growth are presented.