ELECTRON-EMISSION FROM METAL-DIAMOND(100), METAL-DIAMOND(111) AND METAL-DIAMOND(110) INTERFACES

Electron emission characteristics of Cu, Co or Zr films on diamond (10 0), (111) and (110) surfaces were measured by employing ultraviolet ph otoemission spectroscopy (UPS) and field emission measurements. Prior to metal deposition, the diamond substrates were terminated with oxyge n, hydrogen or were free of adsorbates. Deposition of thin Cu or Co fi lms induced a NEA on clean and H-terminated surfaces. A positive elect ron affinity was observed for Cu or Co on oxygenated surfaces, and dep ositing thin Zr films resulted in a NEA on all surfaces considered. UP S can be used to correlate the electron affinity and Schottky barrier height. Schottky barriers of metals on clean surfaces were the lowest, whereas they were the highest on oxygen-covered surfaces. Values for the Schottky barrier height ranged from 0.70 eV to 1.60 eV for Cu, 0.3 5 eV to 1.40 eV for Co and 0.70 eV to 0.95 eV for Zr. A field emission threshold of 79 V mu m(-1) was measured for oxygenated (100) surfaces . The lowest value of 20 V mu m(-1) was observed for Zr on the clean ( 100) surface. For all the metals studied, it was found that a lower Sc hottky barrier height results in a lower electron affinity, and a lowe r electron affinity results in a lower field emission threshold. (C) 1 998 Elsevier Science S.A.