Epitaxy of Binary Compounds and Alloys

Abstract

The present work aims at constructing a theoretical framework within which to address the issues of morphological instabilities (one-dimensional step bunching and two-dimensional step meandering), alloying, and phase segregation in binary systems in the context of (physical or chemical) vapor deposition. The length scale of interest, although nanoscopic, is sufficiently large that the steps on a vicinal surface can be viewed as smooth curves and, correspondingly, the theory is a continuum one. In a departure from theories inaugurated by Burton, Cabrera, and Frank [The growth of crystals and the equilibrium structure of their surfaces. Phil. Trans. Roy. Soc. A 243 (1951) 299-358] the steps are endowed with a thermodynamic structure whose main ingredients are a step free-energy density and edge species chemical potentials. Moreover, crystal anisotropy, with its altering of the dynamics of steps and the associated morphological instabilities, is accounted for -in a manner consistent with the second law -both in the thermodynamic and kinetic properties of terraces and, more importantly, of steps. Additionally, in contrast with most of

Stability of Vicinal Surfaces: Beyond the Quasistatic Approximation

“…To understand it, recall that (thermal, mechanical or chemical) equilibrium between two phases involves two conditions at their interface: continuity of heat flux and the Gibbs-Thomson relation in thermal equilibrium; continuity of traction and the Maxwell condition in mechanical equilibrium; continuity of both chemical and grand canonical potentials in chemical equilibrium. Since step motion results from the nonequilibrium chemical process of adatom incorporation, it is natural that the jump in the grand canonical potential, which reduces to Θ⟦ρ⟧ when adatoms behave like an ideal lattice gas, should appear in the driving force at the steps [25][26][27].…”