Competition between ferroelectric and semiconductor properties in Pb(Zr0.65Ti0.35)O3 thin films deposited by sol–gel

Abstract

Asymmetric metal-ferroelectric-metal ͑MFM͒ structures were manufactured by sol-gel deposition of a lead zirconate-titanate ͑PZT with Zr/Ti ratio 65/35͒ film on Pt-coated Si, with a Au top electrode. The average remnant polarization of 9 C/cm 2 and the coercive field of 39 kV/cm were obtained from the hysteresis loop measurements. A detailed analysis of the polarization-electric field ( P -E), capacitance-voltage (C -V), and current-voltage (I -V) measurement results allowed us to estimate the near-electrode space-charge region thickness ͑roughly half of the film thickness at zero voltage͒, net doping concentration ͑around 10 18 cm Ϫ3 ), built-in potential ͑in the 0.4 -0.8 V range, depending on the injecting electrode͒, and dynamic dielectric constant ͑5.2͒. The current logarithm-voltage dependence for the field-enhanced Schottky emission obeys a ''1/4'' law. The spectral distribution of the short circuit current measured under continuous light illumination in the 290-800 nm range exhibits a cutoff wavelength at 370 nm and a maximum sensitivity at about 340 nm. The estimated band-gap energy of the PZT material is 3.35 eV. The MFM structure is discussed in terms of two back-to-back Schottky diodes with a ferroelectric material in between. It is concluded that the semiconductor properties of the films are not negligible and, in certain conditions, are dominating over the ferroelectric ones.

Evolution of polarization and space charges in semiconducting ferroelectrics

“…Specifically, U 1 < U 2 results in a larger negative coercive field compared to the positive coercive field and vice versa when U 1 > U 2 . These observations are consistent with experimental observations, [38][39][40] including those by Feng et al, 41 who studied the hysteresis loops of P(VDF-TrFE) thin films with the following metal electrode configurations: Al=Al, Al=Ni, Ni=Al, and Ni=Ni.…”

Metal-ferroelectric-metal heterostructures with Schottky contacts. I. Influence of the ferroelectric properties

“…35,36,51 We will try in the following to discuss the conditions under which the (15) and (16) can be applied and which are the limitations.…”

Properties of (001)-textured Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films

“…Consequently, it is considered that the conductivity mechanism is primarily interface-controlled. Boerasu et al [12] demonstrated that, for metal/film/metal structure, Pb (Zr 0.65 Ti 0.35 )O 3 thin films obey the "1/4 law", which was described using the following formula:…”