The role of rough surfaces in quantitative ADF imaging of gallium nitride-based materials

Abstract

We have studied the surface of GaN after preparations commonly used to thin cross sectional samples to electron transparency with atomic force microscopy (AFM) and scanning transmission electron microscopy annular dark-field (STEM-ADF) imaging. Tripod polishing and ion milling leave the GaN surface in varying degrees of roughness and strain. By comparing the roughness seen in the AFM with the 'roughness' observed in STEM-ADF imaging, we show most nano-scale variations in ADF can be attributed to surface roughness alone. However, some systematic differences are seen for very thin specimens. © 2010 IOP Publishing Ltd.