Fentosecond Time Resolved Surface Structural Dynamics of Optically Excited Silicon

Abstract

ABSTRACTLaser processing of materials has raised a number of interesting issues relating to phase transitions and the structure of optically excited semiconductors. In this paper we describe the dynamics of structural changes that take place on a silicon surface following excitation with an intense optical pulse. Second harmonic generation from the silicon surface is used as a tool to measure crystalline order with 90 femtosecond resolution. The three-fold rotational symmetry of the silicon <111> surface is observed to become rotationally isotropic within a picosecond after excitation consistent with a transition from the crystalline to the liquid molten state.