Role ofO2negative-ion formation in low-energy electron-induced oxidation of InP(110)

We report surface oxidation induced by (1–8) eV electrons incident on ${\mathrm{O}}_2$ condensed on InP(110) at 30 K. The measured reaction cross sections are very much energy dependent with values of (8±4)×${10}^{\mathrm{-}18}$, (1±0.5)×${10}^{\mathrm{-}17}$, (8±4)×${10}^{\mathrm{-}17}$, and (2±1)×${10}^{\mathrm{-}16}$ ${\mathrm{cm}}^2$ for electrons with energies of 1, 2, 5, and 8 eV, respectively. These cross sections exhibit the same energy dependence as molecular-oxygen negative-ion formation, and they are much larger than those related to dissociative electron attachment. The results show that resonant negative-ion formation of ${\mathrm{O}}_2^{\mathrm{-}}$ is important in surface reactions induced by electron irradiation.