CURRENT EFFECTS ON SI(111) SURFACES AT THE PHASE-TRANSITION BETWEEN THE 7X7 AND THE 1X1 STRUCTURES .2.

In our previous paper [Surf. Sci. 287/288 (1993) 820] it was reported that a DC current effect on step structures of Si(111) surfaces, forming either a regular array of steps (R surface) or step bunching (B surface), reverses three times across the phase transition between the 1 x 1 and the 7 x 7 structures. The current effects were similar for the [112BAR], [112BAR] and [110] steps except for some details. In the present paper, detailed studies show that the reversals depend on terrace width and step character. A video tape recording showed that the difference is closely related to the magnitude of the thermally induced fluctuation of the step shapes at the phase transition temperature. Along with such studies, it was found that the phase transition to the 7 x 7 structure depends on the terrace width.