Abstract

Si(001) interfaces are among the most technologically important for nonlinear optical analysis, yet their exceptionally weak interfacial second harmonic susceptibility χ⁽²⁾_s has strongly inhibited quantitative interface-specific second harmonic (SH) spectroscopy and related nonlinear optical process control applications. The advent of widely tunable, unamplified femtosecond (fs) solid-state lasers has overcome this barrier by enabling unprecedented SH generation efficiency (~ 10⁶ photons/s) with minimal interface heating (<20 K).¹ We have exploited these capabilities to characterize technologically important characteristics of buried SiO₂/Si(001) interfaces, including microroughness,² band-bending,³ strain,⁴ and interface oxidation stoichiometry⁵ by SH spectroscopy with a single unamplified Ti: sapphire fs laser beam. Here, as an example, we highlight an interface-specific SH electro-modulation spectroscopy³ study of a Cr/SiO₂/Si(001) MOS structure, and its extension to a fs-time-resolved SH pump-probe study of carrier dynamics in the space-charge region (SCR). In addition we illustrate real-time (< 0.1 s kinetic resolution) SH monitoring of hydrogen (H) coverage of Si_1-xGe_x(001) epitaxial growth surfaces during UHV chemical vapor deposition.

© 1996 Optical Society of America