Interfacial roughness of Fe₃Si/GaAs(001) films studied by X-ray crystal truncation rods

Crystal truncation rods (CTRs) from thin Fe₃Si films grown on GaAs(001) by molecular beam epitaxy (MBE) are measured at different stages of deposition. The films do not develop their own surface roughness but are conformal to the substrate, so that the substrate roughness governs the whole system. A factor that describes the roughness of a zinc blende structure in the β model of terrace height probabilities is derived and applied to describe the experimental curves. We show that the β model adequately describes the CTRs while the model of continuous Gaussian fluctuations of the surface height notably underestimates the root-mean-squared (rms) roughness.