Quantitative TEM analysis of 3-D grain structure in CVD-grown SiC films using double-wedge geometry

We have characterized the structure of chemical vapor deposition-grown polycrystalline cubic SiC films by quantitative transmission electron microscopy. A new double-wedge sample geometry allowed accurate statistical measurements of the grain size as a function of distance from the substrate. The data are well described by the van der Drift model of faceted film growth with a 〈1 1 1〉 texture that narrows with distance h from the substrate. It was found that the distribution of grain sizes d(h) is self-similar and the mean grain size follows a power law of the type 〈d〉 ∝ hν. However, the measured exponent ν = 0.68 ± 0.1 is significantly larger than that previously predicted from mean field models and computer simulations of three-dimensional film growth (ν = 0.4). This difference may be due to the polarity of SiC, its low stacking fault energy and abundant defects, or impurities. The accuracy of the experimental observations due to the new sample geometry reported here is sufficient to enable statistical tomography or provide guidelines for improved computer modeling.