Sputtered thin film boron nitride cold emitters on metal substrates

Carbon-doped BN films of about 100nm thickness were deposited by reactive magnetron sputtering on "smooth" and beadblasted Mo and Nb substrates. Electron emission, at a given extraction voltage, is orders of magnitude larger from the BN coated surfaces. Emission from the beadblasted surfaces is enhanced over emission from the smooth surfaces due to increased field emission from the beadblasted-induced surface protrusions. With a 0.5mm diameter extraction electrode, current densities of 0.35A/cm(2) were obtained Emission stays constant to pressures of about 1x10(-4) Torr.