Competition of nitrogen doping and graphitization effect for field electron emission from nanocrystalline diamond films

摘要

Field electron emission properties were investigated for nitrogen-doped nanocrystalline diamond films grown on Si substrates from CH4/Ar/N-2 gas mixtures by direct current arc plasma chemical vapor deposition (CVD). Different nitrogen content in the gas mixtures and different deposition temperatures were used for the growth to get the films with different nitrogen content, microstructure, and field emission properties. In addition, higher growth temperature for some of the films assists to partial graphitization of the diamond films that can improve the emission too. The film surface and microstructure was studied using atomic force microscopy, scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and electron energy-loss spectra to find correlations between the field emission and other film properties. The field electron emission was studied using both a macroscopic phosphor screen setup and a microprobe setup. It was found that nitrogenated CVD diamond films show different microstructure than the films prepared without nitrogen. The field electron emission for the nitrogenated films was typically better than for the "pure" diamond films. On the other hand, partially graphitized films grown at higher temperatures (with or without nitrogen in the gas mixtures) typically show the best field emission properties with emission threshold fields of as low as 1-2 V/mum, higher density of emission sites, and higher working limit of the emission current. (C) 2004 American Vacuum Society.