ROLE OF O2 NEGATIVE-ION FORMATION IN LOW-ENERGY ELECTRON-INDUCED OXIDATION OF INP(110)

We report surface oxidation induced by (1-8)-eV electrons incident on O2 condensed on InP(110) at 30 K. The measured reaction cross sections are very much energy dependent with values of (8 +/- 4) x 10(-18), (1 +/- 0.5) x 10(-17), (8 +/- 4) x 10(-17), and (2 +/- 1) x 10(-16) cm2 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 O2- is important in surface reactions induced by electron irradiation.