TUNING THE ELECTRON-AFFINITY OF CVD DIAMOND WITH ADSORBED CESIUM AND OXYGEN LAYERS

The adsorption of Cs on CVD diamond is observed to produce the conditi on of negative electron affinity (NEA). The intensity of the NEA photo electron peak together with the thermal and chemical stability of the NEA condition are measured and are found to be sensitive to the chemic al species terminating the diamond surface prior to caesiation. Diamon d surfaces that have been etched with acid and annealed to 1400 K, or simply oxidised at 300 K before caesiation aisplay strong NEA characte ristics that are chemically stable in air and thermally stable to 650 K. Diamond surfaces that have been hydrogenated prior to caesiation sh ow a comparatively weaker NEA condition that is thermally and chemical ly unstable, The results are rationalised on the basis of band bending and reactive interface formation. (C) 1997 Elsevier Science S.A.