The surface reactivity of CVD diamond films, which function as UV photocathodes, with thermal and electronically excited O2, as well as atomic oxygen, has been explored. The CVD films show a low, but measurable reactivity with O2, which increases markedly with electronic excitation, to form dilute oxygen adlayers which are stable thermally to 800 K. In contrast, reaction with atomic O produces significantly higher surface concentrations of oxygen, although these adlayers decompose thermally below 500 K, evolving CO2. Greater surface reaction probabilities are observed if the diamond surface is pre-hydrogenated before interaction with oxygen. The consequences of these observations for the stable operation of H-terminated diamond photocathodes are discussed. © 2001 Elsevier Science B.V. All rights reserved.
