Precision sub-monolayer manipulation of diamond surface chemistry using laser direct write oxidation in air

Manipulation and patterning of diamond surface chemistry is of interest for a wide range of diamond-based technologies. We report the patterned oxidation of hydrogen-terminated diamond surfaces with sub-monolayer (ML) precision by a deep-UV two-photon process performed in air. Using focused laser pulses of photon energy 4.66 eV (266 nm; below the diamond bandgap of 5.47 eV), hydrogen-terminated (001) surfaces were exposed with calibrated doses to remove carbon with a precision of 0.02 ML. The measurement of the electrical properties of the laser-exposed zone between ohmic electrodes enabled monitoring of the transition from a conducting H-terminated surface to insulating O-terminated. The surface resistance increases by more than 7 orders of magnitude for doses corresponding to 0.5 ML, and the I-V characteristics show a transition from linear to nonlinear for doses above 0.30 ML. We show that this behavior agrees well with a surface percolation model for carrier diffusion in which the laser etch rate for the H-terminated top layer is the same as for O-terminated. Hence, this work reveals an ultra-precise method for modifying the sub-monolayer surface chemistry with the practical advantages of a laser-induced mechanism compared to conventional plasma or chemical processing methods.