Optical second harmonic spectroscopy of semiconductor surfaces: advances in microscopic understanding

Even‐order non‐linear optical spectroscopy has emerged as an unusually sensitive technique for non‐invasive analysis of surfaces and buried interfaces of centrosymmetric materials. The forefront challenges are: to develop reliable microscopic computational methods for calculating and interpreting measured surface non‐linear spectra; to relate non‐linear surface spectra quantitatively to linear optical surface probes such as reflectance‐difference spectroscopy (RDS); and to develop convenient methods for acquiring non‐linear optical spectra over bandwidths (several electron‐volts) that encompass multiple electronic surface resonances. We review recent advances in both calculation and measurement of non‐linear spectra, with emphasis on reconstructed and adsorbate‐covered silicon surfaces in epitaxial growth environments.