Silicon nitride and oxide powder surface characterization by TPD

Surfaces of silicon nitride powders produced bl: three different production processes were analyzed by temperature programmed desorption (TPD) technique. The main desorbed species detected in the temperature range 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 and c). Powders SIO and SiO2(am) show much lai ger desorption quantities than the other powders investigated The distributions of desorbed species fractions reflect the production process and nitridation media. Powders 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 increase -NH2 and =NH groups (C5, C6). For a powder using NH3(g) + CH4 as nitridation media, the heat treatment in air does not seem to increase -OH (B2), however shows similar desorption distribution to the powder using NH3(g) as nitridation media, but produced by a different method (A2). The use of NH3(l) appears to enhance the formation of surface groups which evolve as NH3 and N-2, with respect to the use of NH3(g) (Al). (C) 1998 Elsevier Science Limited. All rights reserved.