Fluoride accelerated nitridation of silicon

Fully characterized silicon powder has been nitrided alone, and in the presence of small amounts of aluminum, calcium and sodium fluorides. Comparisons of the overall extents of reaction, and individual alpha- and beta-silicon nitride phase yields, have been made. It is concluded that the principal action of these fluorides is the disruption of the native silica film on the silicon surfaces, thereby increasing the active site density at which nitridation can occur. The nitridation kinetics are shown to be consistent with a 'mutually blocking pore' model.