Why monatomic steps on Si(001) are always rough

Abstract

High temperature scanning tunneling microscopy (STM) measurments are performed to study the behavior of monatomic step edges on Si(001) at elevated temperatures. The freeze out temperature ${\mathit{T}}_{\mathit{f}}$, at which the roughness of these step edges is frozen out, is estimated to be well above the intrinsic roughening temperature ${\mathit{T}}_{\mathit{r}}$ of the edges. This means that these step edges are always rough at room temperature. The 1D random walk behavior of the step edges, as determined from room temperature STM images, suggests that the step-step interaction is very weak compared to the kink formation energies.