Electrode Effect on Ferroelectricity in Free-Standing Membranes of PbZr_0.2Ti_0.8O₃

Abstract

We report the effects of screening capacity, surface roughness, and interfacial epitaxy of the bottom electrodes on the polarization switching, domain wall (DW) roughness, and ferroelectric Curie temperature (T C ) of PbZr 0.2 Ti 0.8 O 3 (PZT)based free-standing membranes. Singe crystalline 10−50 nm (001) PZT and PZT/La 0.67 Sr 0.33 MnO 3 (LSMO) membranes are prepared on Au, correlated oxide LSMO, and two-dimensional (2D) semiconductor MoS 2 base layers. Switching the polarization of PZT yields nonvolatile current modulation in the MoS 2 channel at room temperature, with an on/off ratio of up to 2 × 10 5 and no apparent decay for more than 3 days. Piezoresponse force microscopy studies show that the coercive field E c for the PZT membranes varies from 0.75 to 3.0 MV cm −1 on different base layers and exhibits strong polarization asymmetry. The PZT/LSMO membranes exhibit significantly smaller E c , with the samples transferred on LSMO showing symmetric E c of about −0.26/+0.28 MV cm −1 , smaller than that of epitaxial PZT films. The DW roughness exponent ζ points to 2D random bond disorder dominated DW roughening (ζ = 0.31) at room temperature. Upon thermal quench at progressively higher temperatures, ζ values for PZT membranes on Au and LSMO approach the theoretical value for 1D random bond disorder (ζ = 2/3), while samples on MoS 2 exhibits thermal roughening (ζ = 1/2). The PZT membranes on Au, LSMO, and MoS 2 show T C of about 763 ± 12, 725 ± 25, and 588 ± 12 °C, respectively, well exceeding the bulk value. Our study reveals the complex interplay between the electrostatic and mechanical boundary conditions in determining ferroelectricity in free-standing PZT membranes, providing important material parameters for the functional design of PZT-based flexible nanoelectronics.

Tuning Exciton Emission via Ferroelectric Polarization at a Heterogeneous Interface between a Monolayer Transition Metal Dichalcogenide and a Perovskite Oxide Membrane

“…Recent work has demonstrated the vertical stacking of perovskite oxide membranes with 2D TMDs in field effect transistors (FETs). − Yang et al and Huang et al used released SrTiO 3 (STO) membranes as dielectric layers in 2D TMD-based FETs, exploiting STO’s large dielectric constant to achieve a high ON/OFF ratio (10 8 ) and low leakage current arising from the sub-one-nanometer capacitance equivalent thickness . Wu et al integrated freestanding PbZr 0.2 Ti 0.8 O 3 (PZT) with few-layer MoS 2 in FETs, achieving an ON/OFF ratio up to 10 5 .…”