Another device which can utilise polycrystalline CVD diamond, and which is causing a great deal of interest at the moment, is the idea of using diamond as an electron emitter in flat panel displays. The electronic properties of diamond are such that when a negative voltage is applied across it in vacuum, electrons are ejected from its surface. This process is also common in most metals, except that in metals the electrons have to overcome an energy barrier, or work function, to escape from the surface. In diamond this barrier has been measured and found to be very small, maybe even negative, and this has given rise to the term 'negative electron affinity'. In practice, this means that devices based on the electron emission properties of diamond could consume very low power levels and hence be extremely efficient. The electrons emitted from the surface are accelerated using a positive grid, and strike a phosphor screen, causing light to be emitted. Each emitting diamond crystal, or group of crystals, would form a 'pixel' on a flat panel display screen. Unlike their major competitors (liquid crystal displays), diamond cold cathode field emission displays would have high brightness, have a large viewing angle, and be insensitive to temperature variations. Also, because of their relative simplicity, it is possible that diamond emitting displays could be scaled up to large areas that would be impossible with liquid crystals - maybe even metres square!
Was this article helpful?