Abstract
Scanning tunnelling microscopy (STM) and current imaging tunnelling currentspectroscopy (CITS) methods were performed on polycrystalline diamond filmsgrown on silicon substrates grown by microwave plasma-enhanced chemical vapourdeposition. Large tunnelling currents were observed at some grain boundariesand crystal surfaces with secondary grains. Following atomic force microscopy(AFM) measurements, we performed scanning probe contact current (SPCC)measurements to investigate the spatial variation of electrical resistance on the surface byusing an AFM cantilever in contact mode. The conducting grain boundaries andfacets were observed on both boron-doped and undoped samples. For microscalecharacterization of the field emission properties, we performed scanning probefield emission current (SPFEC) measurements. From the results of STM/CITS,AFM/SPCC and SPFEC, it is concluded that the specific grain boundaries andfacets on polycrystalline diamonds work as initial points of electron emission andcause high field emission current through a conducting pass formed in the bulk.
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