Surface conductivity induced electron field emission from an indium cluster sitting on a diamond surface

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Abstract
Electron field emission has been performed from a 5 μm indium cluster sitting on a nitrogen doped diamond (100) surface (3×3×1 mm3). The motivation to study such a system arose from the fact that electron field emission from N-doped diamond was reported in literature. However, the emission mechanism is not really known and still the subject of an intense discussion in the diamond/amorphous carbon community. We have chosen this setup to conduct a model experiment with well-defined parameters. The emission properties were analyzed by energy resolved field emission (FEED). We found that electron emission takes place at the apex of the indium grain for a hydrogenated diamond surface. However, large energy shifts were observed in the FEED spectra due to a potential drop across the hydrogen saturated surface. An oxygen termination kills the emission. By sputtering the surface the emission reappears with much lower energy shifts in the FEED spectra due to the conductive sp2 layer. We present a model taking into account the ohmic surface resistivity of the diamond surface and discuss the impact on emission properties of nanoclustered films. The results presented in this article show that surface conduction (hydrogen terminated or sputtered surface) can lead to electron field emission with large shifts in the FEED spectra. While the emission stems from a metallic micron sized tip, the electron supply is guaranteed by surface conduction.