Chemical composition, thermal stability and hydrogen plasma treatment of laser-cut single-crystal diamond surface studied by X-ray Photoelectron Spectroscopy and Atomic Force Microscopy

Abstract

X-ray photoelectron spectroscopy examination shows that after laser cutting under ambient condition, the upper surface of diamond consists of a heavy oxidized layer consisting of a variety of carbon–oxygen chemical states comprising –C═O, –C–O–C– and –C–O–H species. The thickness of the oxide layer was estimated to be ∼22 Ǻ. Upon vacuum annealing to 700 °C the thickness of the oxide layer decreases to ∼10 A and the upper surface layer becomes more diamond-like through desorption of C–O species. Exposure of the laser cut diamond surface to a microwave hydrogen (MW-H) plasma results in removal of the oxide layer and exposure of the diamond phase. This is evidenced by the appearance of characteristic diamond surface and bulk plasmons which accompanied the C (1s) X-ray photoelectron peak. Our studies show that the surface chemical composition and thermal stability of the laser cut and polished surfaces both after MW-H exposure are nearly similar. The morphology of the laser cut surface shows an ill-defined laminar structure without any characteristic features which is not significantly affected by MW-H plasma exposure. This is in contrast to the polished surfaces for which exposure to the MW-H may result in its planarization.