Electrical properties of unconstrained ferroelectric Pb(Zr0.52Ti0.48)O3 microtubes

High aspect ratio (< 30:1) ferroelectric structures have potential applications in areas such as tunable photonic crystals, biosensors and miniaturized transducers. Mechanically unconstrained and free standing Pb(Zr0.52,Ti0.48)O3 (PZT) tubes (1??2 microns in diameter) were processed with pre-patterned porous silicon templates using a Liquid Source Misted Chemical Deposition (LSMCD) technique. After pyrolysis at 300 ??C for 2 min, these arrays were released using a combination of reactive ion etching and a XeF2 silicon etch methods. Surface contamination on these tubes was dissolved with a mild (0.1 M) boric acid treatment prior to rapid thermal crystallization (750 ??C for 1 min). Pervoskite phase formation was confirmed by X-ray diffraction. Small signal electrical properties on a single PZT tube were measured using a set of interdigitated electrodes. The measured capacitance was 7 fF with 5 % loss. The ferroelectric switching was confirmed with capacitance ! vs. dc bias response with a coercive voltage of 8 V. The temperature dependent nonlinear dielectric response in these free standing structures were quantified using Rayleigh analysis down to 10 K. A comparison between PZT thin films and tube of similar wall thickness was made. These measurements suggest that domain wall contributions in thin films are limited by substrate clamping, whereas mechanically unconstrained tube structures have higher extrinsic domain wall contribution to the dielectric and piezoelectric properties.