Grain boundary field electron emission from CVD diamond films

Results are reported on microscopic study of electronic and structural prop erties of field emission centers for chemical vapor deposition diamond film s. The field electron emission (FEE) for the best films studied was observe d at >3 V mu m(-1), and ultralow (<0.1 eV) values of effective work functio n derived from Fowler-Nordheim plot fitting are discussed. A specially desi gned high vacuum scanning tunneling-field emission microscope was applied f or simultaneous mapping of FEE intensity, morphology, work function and loc al electroconductivity evaluation. It was found that the emission centers w ere not associated with sharp morphology protrusions. On the contrary, they correspond to morphology pits (grain boundaries) which also show a low val ue of the work function. A mechanism of the low-FEE near grain boundaries i ncluding field enhancement of narrow conductive channels between insulating diamond grains is discussed. (C) 1999 Elsevier Science S.A. All rights res erved.