Electron field emission from the 2D hole gas in hydrogen terminated, polycrystalline diamond

The results of field emission measurements from hydrogen and non-hydrogen terminated polycrystalline, B-doped and undoped diamond surfaces are reported. The field emission from the undoped polycrystalline diamond show different current density vs. electric field characteristics than field emission from hydrogen terminated polycrystalline B-doped diamond and from hydrogen terminated single crystal undoped diamond. These differences are attributed to differences in the conduction mechanisms, being bulk conductivity in B-doped diamond and surface conductivity in undoped hydrogen terminated single crystalline and polycrystalline diamond. In contrast to the hydrogen terminated single crystal undoped diamond case, where discrete jumps in the current density vs. electric field curves are observed [L. Gan, E. Baskin, C. Saguy and R. Kalish, Phys. Rev. Lett. 96, 196808 (2006).] the results for the undoped polycrystalline case follow the Fowler Nordheim formalism, reflecting the presence of an ensemble of 2D surface energy states due to the various angles between the crystallite surfaces and the electric field. The parameters extracted from the Fowler Nordheim representation of the data for hydrogen terminated B-doped and undoped polycrystalline diamond, yield a Fermi energy level near the surface region for of 0.34 eV below the valance band maximum for the undoped sample.