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These results reflect what is believed to be the first observation of electron emission from carbon-doped boron nitride (BN). The n-type BN films were synthesized on n-type polycrystalline diamond on (100)Si using reactive laser ablation. The electron emission current density measured at room temperature shows a power law dependence. Emission currents as high as 60 mA  cm−2 have been measured from 150 nm thick n-type BN films on a 24 μm n-type polycrystalline diamond film on a (100)Si substrate. These films show a current density/applied field behavior indicative of negative electron affinity.

Electron emission from a ∼100-nm-thick, laser ablated and laser annealed, carbon-doped BN film deposited on polycrystalline diamond was measured at room temperature and at pressures of about 1×10−8 Torr. For a 500-μm-diam extraction electrode, currents of several mA were obtained which corresponds to current densities of >1 A/cm2. At low currents, the current–voltage characteristics follow the classical Fowler–Nordheim behavior. At higher currents, deviations occur which are correlated to a nonlinear BN film resistance which ranges from 3×106 Ω to 5×104 Ω. For comparison, similar measurements were performed for the polycrystalline diamond film. Current densities of only 1 mA/cm2 were obtained which is attributed to a much higher sample resistance of about 1×109 Ω.

The seeding for large-area mosaic diamond films approaching single-crystal quality is described. The technique includes patterned etching of relief structures in Si substrates, deposition from a slurry and orientation of macroscopic diamond seed crystals in the structures, and chemical vapor deposition overgrowth of the diamond seeds to form a continuous film. The film comprises ∼100 μm single crystals, which are separated by low-angle grain boundaries of a few degrees or less. We believe that these low-angle grain boundaries will not affect the electrical properties of majority-carrier devices.

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