Nanometer scale surface clustering on ZnSe epilayers

We have used atomic force microscopy to investigate the surface morphology of ZnSe films grown on GaAs(001) by molecular beam epitaxy. We report the observation of nanometer scale surface clusters 400–1200 Å in diameter and 60–200 Å in height. The clusters form ex situ as the result of the initial exposure of the ZnSe to atmosphere, and undergo Ostwald ripening at room temperature. Our observations, combined with the relevant literature, suggest that the cluster composition is SeO2. We propose that the oxidation of the ZnSe epilayers produces a thin layer of SeO2 which migrates to form surface clusters on a stable, zinc-related oxide surface. These findings should facilitate greater control of surface morphologies during ZnSe based device fabrication processes.