Periodic faceting of a Si(113) surface miscut towards [110]

The equilibrium morphology of a Si(113) surface miscut by a polar angle of 1.8° away from the (113) orientation along an azimuth within 3.5° of the [11̄0] direction has been characterized by X-ray scattering, for temperatures between 900 and 1450 K. Above 1215 K, a uniformly stepped surface is found. Between 1075 and 1215 K, the surface phase-separates into two coexisting phases of different polar and azimuthal orientations. With decreasing temperature, the phase with the smaller polar angle approaches the (113) orientation, while the other phase exhibits an increasingly large polar angle (up to 9°). The two coexisting phases form a periodic groove structure with periodicity ranging from 740 to 940 Å, depending on the temperature. Below 1075 K, the phase with the larger polar angle further phase-separates into two phases of different azimuth (±17°), resulting in coexistence among three distinct phases. The three coexisting phases form a quasi-periodic array of pyramids.