Real-time scanning tunneling microscopy of phase transition and faceting on a vicinal Si(111) surface

We have used scanning tunneling microscopy for real-time observation of the (7×7) reconstruction on a Si(111) vicinal surface misoriented by 10° toward [112̄]. The (1×1)–(7×7) reconstruction corresponds to the formation of the (7×7) stripes perpendicular to the misorientation direction, and the width of the stripe is quantized in half units of (7×7) mesh. Moreover the (1×1)–(7×7) transition on the vicinal surface takes place at a temperature about 80° lower than that for the flat surface. As the temperature is decreased, further phase separation takes place, changing the vicinal surface into a (111) facet and a slanting surface. On the (111) facet the (7×7) or (5×5) structure is formed, while the slanting surface becomes a (331) facet that shows (12×1) periodic structure.