Thickness dependent charge transport in ferroelectric BaTiO3 heterojunctions

Abstract

We have investigated the effect of ferroelectric barium titanate (BaTiO3) film thickness on the charge transport mechanism in pulsed laser deposited epitaxial metal–ferroelectric semiconductor junctions. The current (I)–voltage (V) measurements across the junctions comprising of 20–500 nm thick BaTiO3 and conducting bottom electrode (Nb: SrTiO3 substrate or La2/3Ca1/3MnO3 buffer layer) demonstrate the space charge limited conduction. Further analysis indicates a reduction in the ratio of free to trapped carriers with increasing thickness in spite of decreasing trap density. Such behaviour arises the deepening of the shallow trap levels (<0.65 eV) below conduction band with increasing thickness. Moreover, the observed hysteresis in I–V curves implies a bipolar resistive switching behaviour, which can be explained in terms of charge trapping and de-trapping process.