The electrochemical dissolution of silicon in fluoride media under very high potentials (5-100 V) was investigated. The interface was characterized by voltammetry and in situ infrared spectroscopy. The infrared results indicate that the interfacial oxide becomes porous above a critical potential of similar to20 V. Light emission from the interface was observed for potentials above similar to10 V. The electroluminescence signal was found to be composed of a red component and a blue component. Both components exhibit an increase in intensity as a function of applied potential, but their distinct dependence suggests that they arise from two distinct types of oxide defects and excitation mechanisms.