The electronic structure of carbon films deposited in rf argon-hydrogen plasma

The electronic structure of C films deposited by sputtering a graphite target in rf. Ar-H2 plasma is investigated by photoemission, Auger emission and electron energy loss spectroscopy (EELS) as a function of the H2 concentration in the feed gas, referred to as [H2]. Adding hydrogen to the plasma causes the films to change from a graphite-like unhydrogenated structure to a non-graphitic hydrogenated structure. The film mass density, as derived from the π + σ plasmon energy, decreases upon H2 addition to the gas mixture, goes through a minimum at low [H2] and increases with increasing [H2]. It reveals a non-monotonous behavior of the film H content as a function of [H2], the maximum H incorporation occurring at low [H2]. This appears to be a characteristic of C deposition via graphite sputtering in Ar-H2 plasma and it is discussed in connection with previous results on the subject.