An amorphic diamond-like film can be deposited from the plasma ablated by a laser from pure carbon feedstock. In this technique the output from Nd-YAG laser is focused on a graphite target placed in a UHV environment. The gross effect of the laser beam is to eject a plume of carbon vapor and then to ionize it. The resulting plasma traverses a drift space to the substrate to be coated. The deposited material generally appears smooth and transparent having an index of refraction of 2.2 to 2.5 and displays bright interference colors. Unrecognized variation of process variables sometimes produces a brownish coloration to the film. On Si(100), Ge, quartz, and glass electrical resistivity is high and the materials seem to fall into the same class of "dehydrogenated" materials as are traditionally produced by the ion beam methods. However, growth rates are much higher with this laser plasma source, routinely reaching 0.5 μm/hr. No seeding or heating of the substrate is needed and substrate temperatures seem to remain at ambient room values during processing. Progress in the characterization of this material will be reported.
|