DefinePK

Abstract

The photoelectrical properties of the hydrogen-terminated diamond surface in the presence of a surface conducting layer has not been reported in the literature. This paper presents a preliminary study of the photoelectrical behavior of the air-induced and fluoro fullerene-induced surface conducting diamond. The photoconductivity observed is attributed to the excitation of electrons from the near-surface valence band into trap states, giving rise to a higher sub-surface hole current. A photocurrent buildup was observed upon laser exposure, with the highest photocurrent up to 56% higher than the initial (dark) current at the diamond surface in the case of doping with C60F48. This appears to be considerably higher than the same sample when doped with water. The observed behavior suggests a possible influence on the level of photoconductivity due to the nature of the acceptor layer, but may alternatively reflect a trend that a reduced (dark) surface conductivity results in a higher relative increase in the photocurrent when exposed to light. The subsequent persistent decay of the photocurrent suggests the role of charge trapping at the trap states. The decay of the photoconductivity takes the form of a stretched exponential typical of a persistent photoconductivity, with the decay exponent, ß values found to be below 0.4 and the decay constants in the range of 46-286 s.