Reversal of Step Roughness on Ge-Covered Vicinal Si(001)

The influence of Ge on the equilibrium step morphologies of vicinal Si(001) has been investigated quantitatively using scanning tunneling microscopy. As the Ge coverage ${\theta }_{\mathrm{Ge}}$ increases, the relative roughness of the two types of steps on the surface reverses. Physically, the accompanying evolving ($2\times n$) reconstruction modifies the kink energetics by introducing a new type of kink, and confines step meandering. The energies associated with these new kinks and the dependence of the step energies on ${\theta }_{\mathrm{Ge}}$ are extracted.