INFLUENCE OF SURFACE MODIFICATIONS ON THE ELECTRONIC-PROPERTIES OF CVD DIAMOND FILMS

The effects of different surface treatments, including ex-situ H-2 and H-2 + O-2 plasma exposure, chromic acid treatment and in-situ vacuum annealing al elevated temperatures, on the electronic properties, part icularly the electron affinity of microwave plasma-grown polycrystalli ne diamond films, were investigated using UV photo-electron spectrosco py (UPS) and X-ray photo-electron spectroscopy (XPS), H-2 and H-2 + O- 2 plasma exposure results in a negative electron affinity (NEA) for al l diamond films, independent of morphology, thickness or phase purity. An additional peak in the region of low kinetic energies of the UPS s pectra correlates with plasma-generated defects that art removed by in -situ vacuum annealing for several minutes at 700 degrees C. NEA is no t affected by this annealing procedure. Oxidation of the diamond surfa ce by hot chromic acid results in a positive electron affinity (PEA) t hat correlates with a pronounced increase in film surface resistivity and complete suppression of electron emission. NEA alone is not suffic ient to ensure good electron emission properties.