Project R-3963

Linear antenna microwave chemical vapour deposition for thermionic emission from n-type doped CVD diamond surfaces (Research)

The goal of this project is to investigate the use of linear antenna microwave chemical vapour deposition (LA MW CVD) for n-type doping of diamond films to be used as thermionic electron emitter. The LA MW CVD technique has only been recently introduced as a novel way to grow thin nanocrystalline diamond (NCD) films with a high sp3/sp2 content ratio, but no experiments with n-type doping were reported. Thermionic emission provides direct energy conversion where thermal energy provides the necessary energy for electrons to escape from a material's surface into vacuum, inducing a flow of current. Hence, a material needs to provide enough charge carriers and the work function of the material should be as low as possible, facilitating an easy emission of electrons. Diamond is an excellent candidate as a hydrogen terminated diamond surface has a negative electron affinity, which allows electrons to escape from the surface without a potential barrier present. However, to provide appropriate conductivity levels, the diamond needs to be doped. The thermionic properties of phosphorus-doped and phosphorus/nitrogen-doped nanocrystalline diamond will be studied, together with their transport and surface properties, whose understanding is indispensable to understand the emission process in detail.

01 October 2012 - 30 September 2016