Giant dielectric constant in TiO2/Al2O3 nanolaminates grown on doped silicon substrate by pulsed laser deposition

High quality amorphous nanolaminates by means of alternate Al2O3 and TiO2 oxide sublayers were grown with atomic scale thickness control by pulsed laser deposition. A giant dielectric constant (>10 000), strongly enhanced compared to the value of either Al2O3 or TiO2 or their solid solution, was observed. The dependence of the dielectric constant and the dielectric loss on the individual layer thickness of each of the constituting materials was investigated between 0.3 nm and 1 nm, in order to understand the prevailing mechanisms and allow for an optimization of the performances. An impedance study confirmed as the key source of the giant dielectric constant a Maxwell-Wagner type dielectric relaxation, caused by space charge polarization in the nanolaminate structure. The current work provides better insight of nanolaminates and their sublayer thickness engineering for potential applications. (C) 2014 AIP Publishing LLC.