Combining surface X-ray scattering and ellipsometry for non-destructive characterization of ion beam-induced GaSb surface nanostructures

Producing surfaces textured with a homogeneous pattern of nanoscale structures is increasingly important for fabrication of semiconductor devices. Although techniques exist for imaging surface nanostructures on a local scale, these techniques are often impractical for use over large areas for finding average structural information. The nanostructured surface in this study consists of densely packed cones produced by sputtering a mono-crystalline GaSb substrate with a low-energy unfocused ion beam, yielding self-organized cones that are slightly tilted away from the sample normal. Here, we devise an all-optical non-destructive characterization scheme using Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) and Spectroscopic Mueller Matrix Ellipsometry (MME) for obtaining all main dimensions including average height, lateral spacing and packing motifs, and the cone top and bottom diameters. It is further shown that both MME and GISAXS are sensitive to small tilts of the nanocone axis from the surface normal.