Role of hydrogen on field emission from chemical vapor deposited diamond and nanocrystalline diamond powder

The field emission properties of diamond-graphite composites were investiga ted as a function of composition both for oxidized and hydrogen covered dia mond. The composites consist of mixtures of nanocrystalline diamond and gra phite particles. In this way their composition could be varied at will whil e the field enhancement factor of the individual crystallites remained unch anged. The measurements prove that graphite is the phase responsible for lo w threshold field emission. The apparent emission threshold is strongly inf luenced by the conductivity of the composites. Hydrogenation has two benefi cial effects. It provides a conducting path to the emission sites via the h ydrogen induced surface conductivity of diamond. It also lowers the effecti ve emission threshold of graphite in contact with diamond that exhibits neg ative electron affinity after hydrogenation. The latter effect was experime ntally verified by photoelectron yield spectroscopy. (C) 2000 American Inst itute of Physics. [S0021-8979(00)02418-X].