The morphology of monatomic step edges on vicinal Si (001) surfaces is briefly reviewed. With increasing miscut angle, the Si (001) surface exhibits an interesting sequence of phase transitions. For a miscut angle smaller than about 0.03°, a hilly structure with step loops is found, whereas a phase of wavy steps coexisting with a phase of straight steps is observed in the range of 0.03°–0.1°. If the miscut angle lies in the range of 0.1° up to about 3°, two types, one much straighter than the other, of monatomic step edges develop. For even larger miscut angles, a phase of straight biatomic step edges is found. The fundamental energetic parameters, like kink formation energies, step edge energies and step-step interactions, which govern the thermodynamic behavior are determined using Scanning Tunneling Microscopy (STM) images of 0.5° misoriented Si (001). Despite the weak strength of energetic and entropic step-step interactions as compared to the interactions along the step edge, i.e. the kink formation and step edge energies, they have a profound effect on the meandering of the step edges. Both entropic and energetic step-step interactions are proportional to L−2 (where L is the average terrace length). The behavior of the step edges at temperatures above room temperature will be addressed with the aid of a high-temperature STM. The freeze-out temperature, T f , of the monatomic step edges is estimated to be higher than 600–700 K. The temperature T f is significantly above the roughening temperature, Tr, of the step edges. This means that at room temperature, the monatomic step edges on vicinal Si (001) are always rough.
Profile of a Faceted Macrostep Caused by Anomalous Surface Tension