Local-field enhancement on rough surfaces of metals, semimetals, and semiconductors with the use of optical second-harmonic generation

Optical second-harmonic generation was used to study the local-field enhancement due to surface roughness on various materials ranging from the alkalis to a semiconductor. The roughness morphology was standardized by evaporating each material onto the same chemically etched glass slide, having microstructures hundreds to thousands of angstroms in size. With the laser excitation at 1.06 μm, the observed second-harmonic enhancements for different materials varied from 27 to 1 × ${10}^{-3\mathrm{}}$ times that of silver. They were in fair agreement with a simple model calculation assuming that the rough surface is composed of a distribution of noninteracting hemispheroids on a plane. The results are used to predict some rather substantial enhancements for surface Raman scattering for a number of substrate materials.