Surface Diffusion and Phase Transitions in Ultrathin Films with Quasi-One-Dimensional Long-Period Structures

Abstract

The kinetics of surface diffusion in a submonolayer film with the structure p(1 × 4) on the (112) bcc crystal surface in the region of a second order phase transition is investigated by molecular dynamics method. It is shown that collective effects play an important role in the surface diffusion within films where long-period chain structures are present. This is due to the strong anisotropy of the surface atomic structure and lateral interaction of adatoms. Adatom chains which form a superstructure p(1 × N) block the path of easy diffusion of individual atoms along the substrate grooves. With increasing temperature, the diffusion coefficients increase rapidly because of the emergence of new vacancies in the chains. Domains of a chain-like structure incommensurate with the substrate are formed in the adsorbed film when passing through the critical temperature. The activation energy for diffusion decreases sharply at temperatures above the critical one. The commensurate islands gradually disappear in the presence of the incommensurate structure as the temperature increases. This increases the number of defects in the incommensurate chain structure. Collective effects in the adsorbed film play an important role even at high enough temperatures owing to fluctuations and destruction of interacting segments of the adatom chains. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35015