Measuring crystal orientation from etched surfaces via directional reflectance microscopy

Mapping crystal orientation has always been the domain of diffraction-based techniques. However, these measurements have limited throughput and require specialized equipment. In this work, we demonstrate crystal orientation mapping on chemically etched aluminum samples using a simple and inexpensive optical technique called directional reflectance microscopy (DRM). DRM quantifies surface reflectance as a function of illumination angle. We identify directional reflectance characteristics of grains with (111) out-of-plane orientation and infer their surface topography to calculate their underlying crystal orientation. We confirm the surface topography using atomic force microscopy and validate DRM orientation measurements with electron backscatter diffraction.