Amorphization of silicon during mechanical treatment of its powders: 3. Sorption of gases

Abstract

Several series of adsorption measurements were made for a more detailed analysis of the processes resulted in the amorphization of silicon during the mechanical treatment of its powder. Among these measurements are the determination of the specific surface area by the BET method and the registration of “instantaneous” sorption of hydrogen and oxygen directly during the mechanical treatment of powders in the atmosphere of these gases. The sorption of hydrogen is low corresponding approximately to the monomolecular coverage of a freshly formed silicon surface. The sorption of oxygen (P> 100 Torr) is significantly higher than that of hydrogen and its yield is close to that of amorphous phase in the inert environment. The presence of oxygen slows down the formation of amorphous phase. To explain this result, it was suggested that, in the regions of the concentration of mechanical stresses, silicon is active, disordered, and possesses a high sorption capacity. In the oxygen atmosphere, the sorbed molecules tend to oxidize the active silicon, whereas, in an inert atmosphere, the amorphous phase that is stable up to 800°C is formed from active silicon.