Characterization of boron doped polycrystalline CVD diamond by ultra high vacuum scanning tunneling microscopy

The atomic scale microstructure and electron emission properties of boron d oped polycrystalline chemical vapor deposited (CVD) diamond were simultaneo usly investigated using ultra high vacuum scanning tunneling microscopy (ST M) and current imaging tunneling spectroscopy (CITS) measurement techniques . Secondary grains with average grain size less than 10 nm were observed to be on top of the isolated crystalline surfaces, and the surface roughness generally increased with increasing doping concentration and deposition tim e. Initiation of electron emission at the grain boundary was observed. Howe ver, not all grain boundaries were active for electron emission. High elect ron emission was observed only at some crystalline facets, while other face ts showed relatively no measurable emission. The difference in electron aff inity of each crystalline facet is believed to the origin of this preferent ial emission. This study implies that the electrons transport through grain boundaries and emit preferentially at low electron affinity facets. (C) 20 00 Elsevier Science S.A. All rights reserved.