High-temperature electrical behavior of nanocrystalline and microcrystalline diamond films

Chemical vapor deposition of diamond has opened up new applications in microelectronics, microelectromechanical systems (MEMS), and coating technologies. This paper compares and contrasts the high-temperature electrical behavior of microcrystalline versus nanocrystalline diamond films. Through-thickness current–voltage characteristics between room temperature and 823 K are presented for a series of films synthesized with different gas phase concentrations of nitrogen and argon. One set of samples was characterized by measurements between room temperature and 823 K and a second set by two-step thermal cycling from room temperature to 573 and 823 K. It was found that with increasing nitrogen concentration (up to 0.1% N₂), the resistivity slightly increased followed by a decrease at higher concentrations. Activation energies and barrier heights were in general lower for the more defective films. These results in conjunction with material characterization indicated that more defective diamond films were synthesized at higher nitrogen concentrations in the gas phase.