Phase transitions on clean and nickel containing vicinal Si(111) surfaces

Abstract

Structure and reversible structural phase transitions on clean vicinal Si surfaces inclined from the (111) plane towards [2 1 1 ] and [ 2 11] 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 [2 1 1 ] and [ 2 11] 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 d 111 (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 [2 1 1 ] contain steps with height 3 d 111, those inclined towards the [ 2 11] 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 2 d 111 on the surfaces inclined towards [2 1 1 1 ] and with height 2 d 111 or 1 d 111, depending on the nickel concentration, on the inclined towards [ 2 11]. On nickel-containing surfaces there also take place reversible structural transitions with varying temperature.