Surface Morphology of Heat-Treated Ceramic Thin Films

The morphology of surfaces of several ceramic materials has been examined using transmission electron microscopy. The approach used was to prepare a sample for examination in the microscope, carefully clean it, and then heat-treat it. In the case of the oxides studied (alumina and spinel) the samples were heated in air; the non-oxides (α-SiC and β -SiC) were annealed under vacuum. The morphology in all but one case was such that the surface faceted parallel to the nearest low-index plane to give well-defined terraces; these were separated by ledges which also tended to facet parallel to the traces of low-index planes. The exception was the {1100} alumina surface, which appears to be unstable in air at temperatures close to 1400°C. A computer program using a multislice approach was used to estimate the height of the steps on the (0001) surface; the step heights appear to be multiples of the c lattice parameter. A reconstruction of this surface as a result of this heat treatment is also proposed.