Enhanced sensitivity of partial O-terminated H-diamond for H2S detection at room temperature

The p-type surface conductivity of H-terminated diamond (HD) has opened new path ways to develop diamond based electronic devices, photo-catalysts, chemical and bio-sensors. Herein, we report on the room temperature H2S detection behaviour of pristine HD and the surface modified HD films with partial O-termination (OHD) through ozonation. The response of the pristine HD and partial OHD devices that are ozonated for 30, 60 and 90 s, is found to be similar to 55, 1420, 810 and 95 % respectively, for exposing 900 ppb of H2S under ambient atmosphere at room temperature. Here, the optimally partial OHD sensor displays an enhanced sensitivity by about an order of magnitude due to the catalytic activity of the sparsely populated O-functional groups on HD surface. Moreover, the gas sensor response is found to be higher in wet background atmospheres such as N-2 and synthetic air as compared to their respective dry atmospheres. Also, the response curve of these sensors exhibits a peculiar decrease in resistance immediately after exposure to H2S under wet background atmosphere while such oxidative behaviour is absent under dry atmospheres. Based on these observations, the plausible sensing mechanism of these H-diamond based sensors is proposed with the concept of humidity induced H2S hydrolyzation.