Electron spin resonance investigation of ion beam modified amorphous hydrogenated (diamondlike) carbon

Abstract

Electron spin resonance (ESR) measurements on diamondlike carbon films show that the as-grown material possesses a very high (2.5×1020 cm−3) concentration of dangling bonds. Upon irradiation with 50-keV C+ carbon ions, the number of ESR active centers increases by a factor of 3.5 and the linewidth narrows, but no shift in the g value is observed, and the resonant peak remains Lorentzian. These effects are concomitant with the previously observed dramatic decrease in the electrical resistivity (4–5 orders of magnitude). The ESR results verify that no graphitelike islands have formed as a result of the irradiation. The likely conduction mechanism is via hopping in band tail states, the number of which increases as a result of the ion impact.