CHARACTERIZATION OF COPPER-DIAMOND(100), COPPER-DIAMOND(111), AND COPPER-DIAMOND(110) INTERFACES - ELECTRON-AFFINITY AND SCHOTTKY-BARRIER

In this study ultraviolet photoemission spectroscopy was employed to c orrelate the electron affinity and Schottky:barrier height of Cu films on type-IIb (p-type) diamond (100), (111), and (110) surfaces. Furthe rmore, field emission measurements were correlated with the effective electron affinity of the samples. Prior to deposition the diamond samp les were cleaned by various annealings and plasma treatments in ultrah igh vacuum. Annealing the diamond substrates to 1150 degrees C resulte d in adsorbate-free surfaces with a positive electron affinity. A nega tive electron affinity (NEA) was induced after depositing 1 Angstrom o f Cu on the clean surface. The Schottky barrier heights for the clean surfaces ranged from 0.30 eV for the (111) surface to 0.70 eV for the (100) surface. Depositing Cu onto H-terminated surfaces exhibiting a N EA still resulted in a NEA on all surfaces. However, the Schottky barr ier heights were larger, ranging from 0.50 eV for the (111) surface to 0.90 eV for the (100) and (110) surfaces. The metal-induced NEA has b een found to be stable to exposure to air. Following a 500 degrees C a nnealing an oxygen-terminated (100) surface with a positive electron a ffinity was obtained. Cu deposition resulted in a positive electron af finity and the largest Schottky barrier height with 1.60 eV. A field e mission threshold held of 79 V/mu m was obtained for an oxygen-termina ted diamond (100) surface. Values of 20, 25, and 53 V/mu m were measur ed for Cu on clean, H- and O-terminated surfaces, respectively. Based on these experiments, it is suggested that chemisorbed species such as H or O on diamond surfaces cause an increase in the Schottky barrier as well as in the held emission threshold field after Cu deposition. [ S0163-1829(98)04627-X].