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Investigation of the high-field conductivity and dielectric strength of nitrogen containing polycrystalline diamond films


Journal of applied physics (1994)
ISSN: 0021-8979
ISSN: 1089-7550
Journal Article
Fraunhofer IST ()
Diamant; diamond; dielectric strength; electrical property; elektrische Eigenschaft; nitrogen; Spannungsfestigkeit; Stickstoff

The influence of nitrogen doping on the electrical properties of polycrystaline diamond films has been studied. The films were prepared in a microwave plasma CVD process usind a H2/CH4/N2 gas mixture. The CH4 concentration was held constant at 0.5% and the nitrogen to carbon automatic ratio was varied between 0.01 and 0.2. The phase purities, surface morphologies and the nitrogen contents of the films were analysed by Raman spectroscopy, scanning electron microscopy, and secondary-ion mass spectroscopy, respectively. From current-voltage characteristics at field strengths up to 10 high 6 V cm high -1 and the temperature range between 300 K and 800 K the conductivity was determined. The dielectric strength was obtained from the breakdown voltage measured using a voltage ramping rate between 50 V sec high -1 and 100 V sec high -1. A minimum in high field and high temperature conductivity and a maximum in dielectric strength were found for the samples prepared with a nitrogen to carbon at omic ratio of 0.02. Compared with nitrogen free samples the conductivity is lowered by more than three orders of magnitude and the dielectric strength is enhanced by a factor of two. The results will be discussed in terms of compensation of acceptor states by nitrogen donors and structural changes of the films.