Dissociative thermal-electron attachment at a surface: CN- emission from nitrogen ion irradiated graphite

We report an observation of strong thermal-emission of CN- ions from nitrog en ion irradiated graphite surface. Careful monitoring of thermal desorptio n of both neutral and charged species demonstrates that the desorbed nitrog en-containing species is dominated by N-2 and C2N2 Molecules and emission o f CN- occurs as a consequence of dissociative thermal-electron attachment t o C2N2 molecules at the surface. An activation energy of 5.0 +/- 0.2 eV for ionization is derived from the temperature dependence of the CN yield whic h is related to the surface work function governing the surface thermal-ele ctron emission. (C) 2001 Elsevier Science B.V. All rights reserved.