Breakdown of step flow growth in unstable homoepitaxy

¹ Laboratory of Physics, Helsinki University of Technology P.O. Box 1100, FIN-02015 HUT, Espoo, Finland
² Fachbereich Physik, Universität Duisburg-Essen - D-45117 Essen, Germany
³ Institut für Theoretische Physik, Universität zu Köln Zülpicher Strasse 77, D-50937 Köln, Germany (Present and permanent address.)

Received: 13 January 2004
Accepted: 2 April 2004

Abstract

Two mechanisms for the breakdown of step flow growth, in the sense of the appearance of steps of opposite sign to the original vicinality, are studied by kinetic Monte Carlo simulations and scaling arguments. The first mechanism is the nucleation of islands on the terraces, which leads to mound formation if interlayer transport is sufficiently inhibited. The second mechanism involves the formation of vacancy islands due to the self-crossing of strongly meandering steps. The second mechanism is observed in the simulations even when the nucleation of islands is entirely negligible, and eventually leads to a mounded morphology due to the formation of deep craters. We show that the growth of the meander amplitude and the synchronization of the meander phase play competing roles in the formation of vacancies, and find numerically that the areal concentration of vacancy islands is inversely proportional to the square of the meander wavelength.