Spatial distribution of electron emission sites for sulfur doped and intrinsic nanocrystalline diamond films

摘要

We have investigated high sp~2 content intrinsic and sulfur doped nanocrystalline diamond films to study field emission properties by electron emission microscopy operated in different modes. Electron emission microscopy enables real time imaging of the electron emission from a surface with a lateral resolution of approx 15 nm. The nanocrystalline intrinsic diamond films exhibit electron emission at room temperature from localized emission sites with weak temperature dependence, and a density of approx 10~3-10~4/cm~2. In contrast, sulfur doped diamond films show similar emission characteristics at room temperature, but at elevated temperatures the emission significantly increases from the localized regions and a thermionic component is identified in the I/V dependence. We discuss the role of S-donor states to explain the enhanced emission of the S-doped nanocrystalline diamond.