Electron field emission from thin fine-grained CVD diamond films

The field emission properties of thin, fine-grained diamond films were investigated by measuring emission currents versus electric field curves. The measurements were performed with a spherical electrode attached to a piezoelectric positioning system. The lateral distribution was analyzed by accelerating emitted electrons onto a fluorescent screen. In addition the transient behavior of the emission current was investigated. These characterization techniques were applied to a large number of CVD diamond films deposited by microwave plasma-assisted CVD. The samples were prepared with various methane concentrations (0.5-7%) and deposition temperatures (700-900 degrees C). Undoped as well as boron- and nitrogen-doped samples were studied. Under optimized conditions threshold field strengths as low as 2 V/ mu m were realized, yielding current densities in the range of several mA/cm2 at 5 V/ mu m. The density of emission sites is on the order of 104 sites/cm2