STRUCTURE OF PLASMA-PROCESSED SILICON POWDERS

The defect structure of silicon particles (initial size of d similar o r equal to 35 mu m) exposed to a high-temperature nitrogen plasma is s tudied by EPR, IR spectroscopy, electron microscopy, and particle-size analysis. Fracturing of the primary particles and subsequent reaction with the plasma gas yield fine crystallites (d similar or equal to 0. 3 Irm) coated with the products of reaction between Si and gas molecul es (primarily N-2 and O-2). Fragmentation of the particles as a result of thermal collisions is followed by surface melting, which favors th e formation of reaction products in the surface layer. The nitriding b ehavior of the plasma-processed silicon powders depends on the surface defect structure thus formed.