Ultrananocrystalline diamond: New opportunities for the fabrication of novel sensors

The ultrananocrystallne diamond (UNCD) thin films are generally characterized by their small grain size (2-5 nm) with about 98% of the carbon atoms present in the sp³ bonded configuration and rest of the carbon atoms residing at the atomically abrupt grain boundaries mostly in mixed sp³ and sp² configuration. Previous studies carried out by our group have shown that the UNCD thin film has excellent chemical, mechanical, and electrical properties. The electrical conductivity of the UNCD thin films can be altered significantly by introducing impurities (such as nitrogen or boron) during the growth. Our recent work has demonstrated that the UNCD thin films can be carved into quasi-1 dimensional nanowires using a top-down nano fabrication process. I will discuss how the impurity presence (nitrogen or boron) and its location (within grain or grain boundary) can significantly affect the resistance of UNCD nanowires as a function of gas adsorption and pressure. This effect could be exploited further for developing extremely sensitive gas and pressure/displacement sensors. We believe that these results will open-up new opportunities and possibilities for the fabrication of novel UNCD-based sensors with increased sensitivity and new functionalities for a variety of applications.