Ceramics-Silikáty 56, (3) 177 - 186 (2012)

Mesoscopic high aspect ratio ferroelectric tube structures of a diverse range of compositions with tailored physical properties can be used as key components in miniaturized flexible electronics, nano- and micro-electro-mechanical systems, nonvolatile FeRAM memories, and tunable photonic applications. They are usually produced through advanced “bottom-up” or “topdown” fabrication techniques. In this study, a template wetting approach is employed for fabrication of Pb(Zr_0.52Ti_0.48)O₃ (PZT) microtubes. The method is based on repeated infiltration of precursor solution into macroporous silicon (Si) templates at a sub-atmospheric pressure. Prior to crystallization at 750^oC, free-standing tubes of a 2-µm outer diameter, extending to over 30 µm in length were released from the Si template using a selective isotropic-pulsed XeF₂ reactive ion etching. To facilitate rapid electrical characterization and enable future integration process, directed positioning and aligning of the PZT tubes was performed by dielectrophoresis. The electric field-assisted technique involves an alternating electric voltage that is applied through pre-patterned microelectrodes to a colloidal suspension of PZT tubes dispersed in isopropyl alcohol. The most efficient biasing for the assembly of tubes across the electrode gap of 12 µm was a square wave signal of 5 V_rms and 10 Hz. By varying the applied frequency in between 1 and 10 Hz, an enhancement in tube alignment was obtained.