THE ROLE OF HYDROGEN AND IRON IN SILICON NITRIDATION BY BALL-MILLING

We have studied in detail the alpha Si3N4 formation during ball millin g of Si in NH3 and N-2 environments and subsequent annealing, alpha-Si 3N4 can be formed upon annealing after Si is milled in NH3, but no suc h phase is found for milling in N-2. This difference is attributed to the role of H in embrittlement of the powder particles and to the subs equent introduction of Fe contamination into the Si powder. Our studie s also show that the presence of Fe greatly enhances the nitridation r eaction of as-milled Si powder. Fe silicide phases can be found after milling in NH3 and annealing, and the extent of silicide depends on th e N content in the powder. In favorable cases, Fe can be removed from the alpha-Si3N4 powder by an acid leach. (C) 1997 American Institute o f Physics.