Interactions of PF3 and PD3 with Clean, P-Covered and H(D)-Covered (100)-OrientedW Foil

摘要

The interactions of PF3 and PD3 with clean, phosphorus- and hydrogen (deuterium)-covered (100)-oriented W foils have been studied using TPD and AES. At 140 K, both dissociative and molecular adsorption occurs. Desorption and additional decomposition occur when the temperature is increased. Electron-stimulated desorption of F(a) is very rapid. The maximum amount of PD3 and PF3 decomposed is 0.5 and 0.18 respectively. At high coverages, PD3(a) decomposes first to PD(a) with E sub d + 17.2 kcal/mol; then PD(a) decomposes to P(a) with E sub d = 20.8 kcal/mol. Pre-adsorbed deuterium (hydrogen) does not block the adsorption of PF3 (PD3), but does inhibit slightly their decomposition. Dosing PF3 (PD3) on D/W (H/W) shifts D2 (H2) desorption to lower temperature by about 100 K. This shift is attributed to the decomposition of PF3 and PD3, which increases the crowding of the surface and induces desorption of H2. Surface P(a) blocks the adsorption and inhibits the decomposition of PF3. Each P(a) adatom prevents the decomposition of one PD3 molecule. Both pre-adsorbed P(a) and D(a)(H(a)) alter the TPD spectra of molecular PF3 by direct, weak interactions with the F. Effects of P(a) and D(a) on the pi back-donation from W to PF3 may also play a role. Each P(a) adatom blocks four sites for D2 adsorption, but the activation energy for D2 desorption does not change. Reprints. (jes)