High nitrogen amounts incorporated-diamond films deposited by the addition of nitrogen in a hot-filament CVD system

Nitrogen-doped diamond films have been synthesized by hot-filament chemical vapor deposition using a CH4/N-2/H-2 gas mixture. The influence of the addition of a large amount of nitrogen in the gas phase on the nucleation and the growth of diamond films and on the binding structure and the content of the nitrogen species in the deposited thin films has been investigated. The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The results have shown that the crystal size decreased and the nucleation density increased with increasing nitrogen concentration in the mixture gas. With the addition of a large amount of nitrogen, the crystal structure of the grown films transformed from micrographite to amorphous, and then to microcrystalline diamond with an increase in methane concentration in the range of 1-4 vol.%. From the X-ray photoelectron spectroscopy analysis, nitrogen was chemically bonded into diamond films to a maximum content of about 3.3 at.%. (C) 1999 Elsevier Science All rights reserved.