Dependence of the catalytic decomposition of PH₃ on wire material

The decomposition processes of PH₃ on heated W, Mo, Ta, and Ir surfaces were studied using mass spectrometric and laser spectroscopic techniques. For all wire materials, the decomposition efficiency saturated to around 50% at high wire temperatures. The P-atom density also saturated showing only minor dependence on the wire materials. At lower temperatures, however, the production rate of P atoms on Ta was higher than that on W, while that for Mo was lower, suggesting that the decomposition processes are not thermal but catalytic. The production rate on Ir was similar to that on W. Possible decomposition mechanisms are discussed