ELECTRON EMISSION MICROSCOPY MEASUREMENTS OF NITROGEN AND SULFUR DOPED CARBON FILMS

摘要

We have employed a high resolution electron emission microscope to image photo-electron emission and field emission from nitrogen and sulfur doped carbon films. The measurements obtained as a function of sample temperature up to 1000℃ display thermionic field emission images. N-doped hydrogen terminated diamond films have been produced by MPCVD with a N/C gas phase ratio of 48. The hydrogen terminated surfaces display uniform emission in photo electron emission microscopy at all temperatures. No field emission microscopy images are detectable below 500℃. Depending on the surface treatment of the nitrogen doped diamond films, we find enhanced electron emission at elevated temperatures starting at around 600℃ that increases with increasing temperature. At elevated temperatures the electron emission for the nitrogen doped films as imaged with the electron emission microscope shows a uniform distribution over a wide surface region. Sulfur doped carbon films exhibit electron emission at room temperature originating mainly from 'hot spots' on the surface. At temperatures as low as 340℃ we find a strong increase in electron emission from those localized regions.