ИСТИНА

Single crystal diamond needles were produced by thermal oxidation of polycrystalline CVD diamond films [1]. Needles had a pyramidal shape with rectangular cross section with length of about 100 µm, thickness at the base of 1 µm and tip apex radius of 10 nm. Field electron emission (FE) measurements were performed using UHV system (4x10-10 Torr) equipped with electron energy analyser [2]. Diamond needles demonstrated excellent stability of emission current in time up to 10 µA. The FE current-voltage characteristics showed strong current saturation that is predicted by the basic theory of the electron emission from semiconductors. In the saturation region, the currents were extremely sensitive to temperature and increased by more than two orders of magnitude with changing of the temperature from 300 to 700 K. Using energy analyser, the total energy distribution (TED) of the emitted electrons was measured as a function of temperature and current. The position of the TED peak gives the voltage drop along the needle. Plotting the emitted current against the voltage drop is equivalent to a two point measurement of a current-voltage characteristic of the needle. This permitted the estimation of activation energy of the saturation current and definition of possible mechanisms of carrier transport. Obtained results show that despite the large band gap of 5.5 eV of diamond, the needles obtained by thermal oxidation of polycrystalline CVD diamond films without intentional doping can be used as field emitters. Possible applications of diamond needles in vacuum electronics will be discussed.