REFLECTION ELECTRON MICROSCOPY METHODOLOGY FOR QUANTIFICATION OF CLUSTER GROWTH: INDIUM CLUSTERS ON THE InP(110) SURFACE

Abstract

Dynamical reflection electron microscopy (REM) can provide a wealth of time-resolved data pertinent to the initial and intermediate stages of cluster growth. REM allows one to follow and quantify the size and shape evolution of individual clusters. Average cluster size and cluster density data can be obtained as a function of time due to the large field of view produced by REM image foreshortening. We describe here a methodology for extracting these data from dynamical REM experiments, based on a geometrical model for the interpretation of REM images from two- and three-dimensional clusters. This methodology has been applied to studies of In cluster growth on InP (110) surfaces at 650°C. The average In cluster height and length initially increased as a fourth root of time, with a constant contact angle with the surface, consistent with surface-diffusion-limited growth of 3D clusters. The same behavior was found in the later stage of cluster growth, but the intermediate stage showed anomalous power laws for the cluster height and base length, accompanied by a decrease in the contact angle between the In clusters and the InP (110) surface. This anomalous regime can be explained by growth of In clusters into the InP substrate, when the true contact angle is no longer defined with respect to the InP(110) surface.