Interfacial roughness scaling and strain in lattice mismatched Si _0.4Ge_0.6 thin films on Si <AUTHGRP>

Interfacial roughness parameters and lattice strain of Si _0.4Ge_0.6 films with varying thickness epitaxially grown on Si(100) were determined using the techniques of grazing-incidence x-ray scattering and diffraction. The roughness of both the buried interface and sample surface follows a similar power-law scaling behavior with an exponent β around 0.71 for films below the critical thickness, and it undergoes a large change above the critical thickness. Observation of such a scaling law thus establishes a quantitative correlation between the interfacial roughness and lattice strain, and also allows the prediction of interfacial roughness as a function of film thickness of this compound.