Nitrogen and hydrogen in thick diamond films grown by microwave plasma enhanced chemical vapor deposition at variable H-2 flow rates

The presence and concentration of nitrogen and hydrogen impurities in thick diamond films grown by microwave plasma chemical vapor deposition at vario us H-2 gas flow rates, keeping a constant [CH4]:[H-2]=2.5% concentration ra tio, have been determined by electron spin resonance and optical absorption spectroscopy. The relative concentration of both impurities, present as pa ramagnetic atomic species with different relaxation properties, has been fo und by ESR measurements to decrease exponentially with the increase in the H-2 gas flow rate. Moreover, the resulting values were proportional to the content of substitutional nitrogen and CHx groups obtained from infrared an d ultraviolet-visible optical absorption measurements, respectively. The de crease in the concentration of both impurities with an increase in the qual ity of the studied diamond films, early observed from high resolution elect ron microscopy studies on the same samples, strongly suggests that the inco rporation of both impurities, as paramagnetic atomic species, is directly r elated to the concentration of the extended lattice defects. (C) 2000 Ameri can Institute of Physics. [S0021- 8979(00)08611-4].