Mechanism of nitridation of silicon powder in a fluidized-bed reactor

Direct nitridation of 400 mu m average-sized silicon granules, composed of 2 mu m average-sized particles, was carried out in a fluidized-bed reactor, Nitridation progress was studied by transmission electron microscopy (TEM). TEM photomicrographs suggested that the formation of surface nitride layers on individual silicon particles and the subsequent spallation of these layers were the dominant process of the direct nitridation of silicon, The spallation was modeled based on a simple crack theory, and the critical thickness of nitride layers leading to spallation was estimated to be 57 nm, This agreed reasonably well with the experimentally observed values of 20-100 nm.