Competing desorption pathways during epitaxial growth: LEEM investigation of Cu/W(110) heteroepitaxy.

Abstract

Competing desorption during the initial stages of epitaxial growth of Cu on the W(110) surface has been studied with low-energy electron microscopy (LEEM). LEEM observations of a strain-induced (1\ifmmode\times\else\texttimes\fi{}1)--(15\ifmmode\times\else\texttimes\fi{}1) transformation of the Cu overlayer which occurs at a critical coverage of ${\mathrm{\ensuremath{\theta}}}_{\mathit{c}}$=2.13 ML have been used as a very accurate, local probe of coverage during deposition. It is found that the growth rate vanishes at high temperature, Tg950 K, due to competing desorption. A mean-field growth model which includes desorption and parametrization of interlayer diffusion flux quantitatively accounts for the experimentally measured dependence of the growth rate upon temperature and incident flux. Our results indicate that there is little or no Cu interlayer diffusion during growth. The desorption energy E=3.67 eV and attempt frequency \ensuremath{\nu}=2.4\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ are determined by examining the balance of incident and desorption fluxes. A step-flow-like growth morphology of the (15\ifmmode\times\else\texttimes\fi{}1) phase occurs when the supersaturation is significantly reduced by competing desorption at high temperature. Island nucleation and coalescence is prominent in the absence of competing desorption at low temperature. \textcopyright{} 1996 The American Physical Society.