Dielectric properties of amorphous Ta-Ge-O and Ta-Si-O thin films

作者：Nad T A^*; van Dover R B

来源：Journal of Applied Physics, 2018, 123(24): 244103.

DOI：10.1063/1.5022336

We have investigated the structural and dielectric properties of two complementary amorphous oxide systems, Ta-Ge-O and Ta-Si-O. We found that these two chemically similar amorphous systems exhibit substantially different composition-property trends. In particular, the dielectric constant of Ta-Ge-O is strongly enhanced in Ta2O5-rich films as previously reported, while only a slight enhancement was observed for any Ta-Si-O compositions and the index of refraction does not show any appreciable enhancement in either system. We determined the effective polarizabilities of the mixed oxides by directly inferring the density of the films, avoiding the assumption that atomic polarizations are additive. The results confirm that Ta2O5-rich compositions in the Ta-Ge-O system exhibit an ionic polarizability that is strongly enhanced over the value expected using the rule of mixtures, which suggests that even small levels of incorporation of GeO2 have a substantial effect on the vibrational structure of the oxide. In this work, we have explored the limitations of the Clausius-Mossotti relation, showing that calculating the dielectric constant using tabulated atomic polarizabilities and experimentally inferred molecular volumes systematically underestimates the dielectric constant for both systems. Only by directly measuring densities and dielectric properties, are we able to expose trends that can be definitively interpreted. Published by AIP Publishing.

• 出版日期2018-6-28