Grain growth, anomalous scaling, and grain boundary grooving in polycrystalline CdTe thin films

We examine the evolution of the surface morphology as well as the dynamics of grain growth and grain boundary (GB) grooving in polycrystalline CdTe films sputter deposited on CdS/glass substrates. Anomalous scaling behavior is found with local roughness exponent αloc = 1 and global (local) growth exponent β = 0.36 (βloc = 0.14). In good agreement with the scaling relation, βloc = β − nαloc, we obtain the correlation length exponent n=1/z≃0.23. We also find that the grain size coarsening exponent p and GB groove growth exponent βg are both equal to β, while the grain size distribution is well described by a log-normal distribution. These results suggest that GB grooving is responsible for the enhanced anomalous scaling and a deviation from the theoretical prediction of p = 1/2, along with the observed log-normal grain size distribution.