Abstract
A pulsed filtered vacuum are deposition system was used to prepare
ta-C thin films and granular Co-C films. The ta-C films prepared at various substrate bias voltages were characterized using Raman
spectroscopy and spectroscopic ellipsometry of which the results
confirmed that these ta-C films exhibit high sp3 fraction of over 80%. The composition of the granular Co-C films prepared by the same
system was determined by non-Rutherford backscattering
spectrometry. The properties of these Co-C Films, as deposited and
after vacuum annealing at various temperatures, were studied using
Raman spectroscopy, electrical measurements, magnetic measurements by
a SQUID magnetometer, atomic force microscopy and magnetic force
microscopy. It was found that the dependence of the Raman spectra of
these films on annealing temperature was associated with the formation
and dissociation of a cobalt carbide phase and the graphitization of
amorphous carbon. The magnetic properties showed complicated
composition and annealing temperature dependence. The optimum
annealing temperature for the maximum coercivity was found to depend
on the composition of the film. For a film of Co65C35 after annealing at 623K in vacuum for one hour, the coercivity was measured
to be 460 Oe at 300K and 1380 Oe at 3K. Clear MFM images of the domain structures were observed for films after annealing at sufficiently
high temperature, showing that there was perpendicular magnetic
anisotropy in these films. A nearly-temperature-independent electrical
resistance in the range from 20K to 300K was also observed. A more
detailed analysis indicated that the low temperature electrical
transport is consistent with a theory for granular metal films.