Molecular volume and electronic and vibrational polarizibilities for amorphous LaAlO3

Grazing incidence x-ray reflectivity measurements are used to determine the density of sputter-deposited LaAlO3 and anodized LaAl films. Together with refractive index and dielectric constant measurements, it is demonstrated that a coherent picture emerges explaining the low dielectric constant of the amorphous films (similar to13) as compared to the single-crystal value (similar to26). The importance of molecular volume dependence of the electronic and vibrational molecular polarizabilities is underlined. (C) 2004 American Institute of Physics.