Probing the surface of silicon and the silicon-silica interface using nonperturbative third and fifth harmonic generation

TL;DR

This study investigates third and fifth harmonic generation on silicon and silicon-silica interfaces, revealing polarization-dependent signals and introducing a tensor formalism to understand surface and interface structures.

Contribution

It presents a nonperturbative analysis of harmonic generation at silicon surfaces and interfaces, with a new tensor formalism for polarization dependence.

Findings

Strong polarization dependence of harmonic signals observed

Differences between silicon surface and silicon-silica interface explained qualitatively

Tensor formalism accurately describes polarization dependence

Abstract

We examined, in backward (reflection) geometry, the generation of the 3rd and 5th harmonics, located in the deep and vacuum ultraviolet, on the surface of silicon and on the interface between silicon and silica when a thin silica film was grown on a silicon substrate. In both cases, a strong dependence of the harmonic signal on the polarization direction of the driving laser beam was found. The differences observed for both samples, are qualitatively explained. Furthermore, a simplified tensor formalism for the polarization dependence is introduced, which reveals the structural symmetry of the surface and the interface and describes the polarization dependence with high accuracy. The study is an essential step to further understand nonlinear interaction and nonperturbative harmonic generation on the boundaries of materials.