Description:
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Hydrogenated amorphous carbon films with a high content of sp<jats:sup>3</jats:sup> bonds were prepared by a glow-discharge-decomposition of CH<jats:sub>4</jats:sub> and H<jats:sub>2</jats:sub> mixture. With exposure to light at 77 K, the films exhibit a new ESR signal with <jats:italic>g</jats:italic>=2.011 and a half width of 23 G in addition to an enhancement of the signal at <jats:italic>g</jats:italic>=2.003 due to C dangling bonds. The new signal is attributable to trapped holes in the valence-band-tail-state, and its density decreases with increasing hydrogen content in the film.
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