Photo induced electron emission from nitrogen doped diamond films on silicon
Contributors: Tianyin Sun, Franz A.M. Koeck, Aram Rezikyan, Michael M.J. Treacy, and Robert J. Nemanich
ABSTRACT
Diamond films are known for their property of obtaining a negative electron affinity (NEA) after hydrogen passivation [1]. The electron affinity is defined as the energy required to remove an electron from the conduction band minimum (CBM) of a semiconductor to vacuum. For nanocrystalline diamond n-type doping has been achieved by incorporation of nitrogen, with a donor level of nitrogen at 1.7 eV below the CBM [2]. NEA and n-type doping lead to lowering of the electron emission barrier, i.e. the effective work function. This enables low temperature thermionic emission from doped diamond films. For films on absorbing substrates, photoinduced electron emission has been observed with visible light excitation [3]. The configuration of a diamond film on a semiconductor substrate provides both thermionic and photo-generated electrons which are emitted into vacuum through the low work function surface. It has been proposed that with a proper film-substrate configuration, the photon enhanced thermionic emission (PETE) mechanism can substantially enhance the emission current at elevated temperatures [4]. At moderate temperatures both direct photoemission and PETE contribute to the emission. This research presents an investigation of photo-induced electron emission from nitrogen-doped diamond film on Si substrates.