INP(110) OXIDATION WITH O2, NO, AND N2O AT 20 K - TEMPERATURE AND PHOTON-ENERGY DEPENDENCIES

Interfaces formed at 20 K by condensing O2, NO, and N2O on InP(110) reveal striking differences in reactivity when they are heated, illuminated with visible light, or irradiated with soft x rays [h-nu = 170 eV, photon exposures of (1-1000) x 10(14) cm-2]. Synchrotron-radiation photoemission studies show that O2 and N2O desorb from the surface without reacting when annealed above approximately 100 K but that oxidelike In and P bonding configurations are produced by NO reactions when heated to approximately 150 K. Flood-lamp illumination induces reaction for O2/InP and NO/InP at 20 K but not for N2O/InP (h-nu = 0.5-4.5 eV, photon exposure approximately 10(19) cm-2). Irradiation with 170-eV photons yields surface oxides for all three oxygen-bearing condensates. Investigations of the reaction cross sections for these systems indicate that surface chemistry is mediated by the capture of photogenerated low-energy electrons. Electron-attachment processes that produce negative ions are less likely for N2O than for NO or O2.