Homogeneous and heterogeneous nucleations in the surface phase transition: Si(111)4 × 1-In

Abstract

Homogeneous and heterogeneous nucleations in a reduced-dimensional system undergoing a firstorder structural phase transition were examined by using low electron energy diffraction and scanning tunneling microscopy. The high-temperature 4 × 1 phase of a Si(111)-In surface was supercooled at temperatures below the transition temperature (Tc) and evolved slowly into a low-temperature 8 × 2 phase with time. The transition rate decreased significantly as the temperature approached Tc. The kinetics of the observed homogeneous nucleation was analyzed by classical nucleation theory. The introduction of oxygen atoms reduced the hysteresis and accelerated nucleation significantly, showing that the Tc-raising oxygen impurity plays the role of a nucleation seed for heterogeneous nucleation.