Study of carbon material surface layers modified by nitrogen and argon ion irradiation

We present the results of the study of the elemental composition and defects of the electronic structure of the surface layer modified by high-dose irradiation (1018–1019 ion/cm2) of highly oriented pyrolytic graphite (UPV-1T) by 30-keV N 2 + and Ar+ ions in the temperature range from 180 to 400°C. The EPR spectra observed during irradiation with argon ions at high temperatures and with nitrogen ions at temperatures near the liquid-nitrogen temperature T = 77 K exhibit anomalously narrow lines which probably result from the exchange interaction inside paramagnetic clusters of displaced carbon atoms. During nitrogen ion irradiation at room and higher temperatures, paramagnetic defects typical of many carbon materials (single EPR lines with g = 2.0027–2.0029) and belonging to carbon atoms bound to one or three nitrogen atoms were detected.