Influence of bias voltage on dielectric relaxation of nanocrystalline anatase TiO2 using modulus formalism

Abstract

Dielectric relaxation in sol–gel-derived anatase titanium oxide nanocrystals (6, 9, and 20 nm) has been investigated using impedance spectroscopy in a wide frequency range from 1 Hz to 1 MHz as a function of applied DC bias voltage, ranging from 0 to 4.2 V in a periodic interval of 0.3 V. Under the equilibrium condition, around three order of magnitude variations in the dielectric relaxation time (τ) was observed for the grain size if reduced to 6 nm from 20 nm. An unambiguous evidence for the absence of such a crystallite size effect was experimentally observed in higher biased conditions because of grain boundary Schottky potential barrier height suppression. These experimental results obey the “grain boundary double Schottky barrier model.”