Low-threshold defect formation and modification of Ge surface layer under elastic and elastoplastic pulsed laser effects

Abstract

Changes in the spectra of fluorescence of dye (rhodamine B) molecules adsorbed on a Ge surface and modification of the parameters of Raman and diffuse scattering of light by a semiconductor surface subjected to elastic and elastoplastic effects of pulsed laser radiation are studied. Using contactless photoacoustic measurements based on the laser beam deflection technique, the amplitude of the threshold surface strain is estimated at ∼5×10−5. An appreciable quenching of the fluorescence of the adsorbed probe molecules, an abrupt broadening of the molecular spectra, and an above-threshold increase in the intensity of the diffusively scattered light are observed upon the transition to the range of energy densities corresponding to the inelastic strain formation. The larger the laser-induced strain, the smaller the frequency and the width of the Raman lines, and the higher their intensities. The physical nature of these effects is discussed.