SILICON-NITRIDE AND OXIDE POWDER SURFACE CHARACTERIZATION BY TPD

Surfaces of silicon nitride powders produced bl: three different produ ction processes were analyzed by temperature programmed desorption (TP D) technique. The main desorbed species detected in the temperature ra nge 40-1300 degrees C are H-2, H2O, NH3 and N-2 from Si3N4 and Si2N2O powders, and H2 and H2O with small amounts of N-2 from SiO, SiO2(am an d c). Powders SIO and SiO2(am) show much lai ger desorption quantities than the other powders investigated The distributions of desorbed spe cies fractions reflect the production process and nitridation media. P owders produced using N-2 are strongly affected by the final treatment . Heating in air produces a powder with large amount of -OH groups (B1 ), meanwhile acid and water washings reduce the -OH groups and increas e -NH2 and =NH groups (C5, C6). For a powder using NH3(g) + CH4 as nit ridation media, the heat treatment in air does not seem to increase -O H (B2), however shows similar desorption distribution to the powder us ing NH3(g) as nitridation media, but produced by a different method (A 2). The use of NH3(l) appears to enhance the formation of surface grou ps which evolve as NH3 and N-2, with respect to the use of NH3(g) (Al) . (C) 1998 Elsevier Science Limited. All rights reserved.