SUMMARY

Nanoscale ferroelectric materials are of increasing interest due to their numerous possible piezoelectric and ferroelectric applications such as actively tunable photonic and phononic crystals, terahertz emitters, ultrasound transducers, energy harvesters, and nanoelectromechanical system (NEMS) sensors and actuators. One of most technologically relevant ferroelectric materials is lead zirconate titanate (PZT) due to its large piezoelectric response, specially at the morphotropic phase boundary composition (PbZr0.52Ti 0.48O3). However, there are limited methods currently available for creating nanoscale PZT structures. Current top-down methods used to pattern PZT films into nanostructures include material removal via a high energy beam, which damages its properties, and wet etching, which is an isotropic process that results in poor edge definition. Similarly, current bottom-up approaches such as hard template-growth and hydrothermal processing have limited control over the aspect ratio of the structures produced on a single substrate, in addition to lack of site specific registry. In this work, a bottom-up approach for creating PbZr0.52Ti 0.48O3 nanotubes was developed using soft-template infiltration by a sol-gel solution. This method allows excellent control of lateral dimensions of the piezoelectric structures with variable design on a single substrate and sub-micron detail, overcoming current manufacturing limitations. PZT nanotubes were fabricated with diameters ranging from 100 to 200 nm, aspect ratios (height to outer tube diameter) from 1.25:1 to 5:1, and wall thicknesses from 5 to 25 nm. The piezoelectric and ferroelectric nature of the nanotubes was characterized via scanning probe microscopy in order to investigate nanoscale phenomena. Specifically, the effects of lateral constraint, substrate clamping, and critical size on the extrinsic contribution to the piezoelectric response were studied and the results will be discussed.