| Sputter deposited cobalt-based alloy thin films have structural heterogeneities consisted of two phase structures those are composed of cobalt-rich particles and oxide-rich boundaries. Size of the particles increases with increasing incident angle of sputtered atoms. The films sputter deposited with negative substrate bias show so-called `high temperature` structures with large and relaxed particle shapes, mainly due to the less effect of oxygen. Size of the particles decreases with increasing substrate temperature below 300℃ during sputter deposition. Pure Co thin films show decreasing particle size by polymorphic transformation from hcp and fcc mixed structure to fcc structure. CoB alloy thin films deposited without substrate bias show also decreasing particle size by increasing number of nucleation sites based on selective oxidation of boron. On the other hand, CoB alloy films deposited with negative substrate bias do not show any changes of particle size keeping columnar structures. However, at substrate temperature above 300℃, particle growth is dominant resulting in increasing particle size. Post depostion annealing of all cobalt-based thin films used in this experiment causes particle growth, high temperature structures, and two phase structures with structural and compositional heterogeneities. |
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