PHASE-TRANSITIONS ON CLEAN AND NICKEL CONTAINING VICINAL SI(111) SURFACES

Structure and reversible structural phase transitions on clean vicinal Si surfaces inclined from the (111) plane towards [211] and [211] poles and the effect of nickel on the structure and the structural transitions on these surfaces have been studied by LEED. The structures of clean surfaces inclined towards [211] and [211] are different. Phase transitions take place at about 870°C and 800° C, respectively. Above the transition temperatures these two surfaces consist of regular steps with heights equal to one interplanar distance d111 (3.135 Å). The terrace width between steps is determined by the angle of inclination to the (111) plane. Below the transition temperatures the surfaces inclined to [211] contain steps with height 3d111, those inclined towards the [211] pole consist of combinations of (111) facets and some other, apparently (133). The effect of nickel leads to the formation of regular steps with height 2d111 on the surfaces inclined towards [2111] and with height 2d111 or 1d111, depending on the nickel concentration, on the inclined towards [211]. On nickel-containing surfaces there also take place reversible structural transitions with varying temperature. © 1990.