Recently, attention has been focused upon laser plasma sources of thin-film diamond. These depend upon laser-ignited discharges in which intense pulsed currents flow through the small volume of carbon plasma ablated from graphite feedstock by a focused laser beam. The materials produced in this way generally resemble the hard amorphic films deposited by ion beams. This paper reports a detailed characterization of these films which we call amorphic diamond. The combination of an optical band gap of 1.0 eV with a grain size of 100–200 Å places this material far outside the range of possibilities available to the model of graphitic islands. A structure of very fine grained diamond would more readily explain the hardness of 13 GPa determined in the absence of any measurable fraction of hydrogen. Such amorphic diamond films have been grown uniformly on 100-cm2 areas at ambient room temperatures with no seeding or abrasion of the substrate.

Diamond-like carbon films have been deposited onto clean, unseeded substrates using a hybrid ion beam technique. In this method the ion fluences available for acceleration were particularly enhanced by the use of laser ablation plumes ejected from highly purified graphite targets. The combination of levels of purity characteristic of ultrahigh vacuum environments, large ratios of ion to neutral concentrations, and high fluences showed considerable merit for the growth of large-area (10 cm2 ) films of optical quality and uniformity at deposition rates approaching 20 μm/h.

Amorphic diamond films characterized by a high percentage of sp3 bonds have been prepared in an UHV environment with a laser plasma source of carbon ions. Peak power densities in excess of 1011 W/cm2 were found necessary to produce films at growth rates of 0.5 μm/h over areas of 20 cm2 having optical quality sufficient to show bright interference colors.

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