Temperature dependence of electron spin resonance in fluorinated amorphous carbon films

Electron spin resonance (ESR) measurements were carried out at 9.2 GHz in the temperature range between 5 and 300 K on fluorinated amorphous carbon (a-C:F) films prepared by plasma chemical vapor deposition (CVD) with different fluorine concentrations and dangling bond densities. The observed temperature dependences of the line width are interpreted in terms of motional narrowing due to hopping motion of dangling bond electrons and also surrounding fluorine motion, taking into account that the original line broadening arises from hyperfine splitting due to surrounding fluorine nuclei. From the temperature dependences of the line width, we conclude that several types of dangling bond centers with different environments are present with different relative densities among a-C:F samples.