Lead zirconate titanate nanotubes processed via soft template infiltration
Bernal, Ashley Lynn
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Nanoscale ferroelectric materials have numerous possible applications such as actively tunable photonic crystals, terahertz emitters, ultrasound transducers, and energy harvesters. One of most technologically relevant ferroelectric materials is lead zirconate titanate (PZT) due to its large piezoelectric response. However, there are limited methods currently available for creating nanoscale PZT structures. Current top-down patterning methods include material removal via a high energy beam, which damages the piezoelectric's 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 and lack site specific registry. In this work, a bottom-up approach for creating PbZr₀.₅₂Ti₀.₄₈O₃ nanotubes was developed using soft-template infiltration by a sol-gel solution. This method allows excellent control of the structures produced, overcoming current manufacturing limitations. PZT nanotubes were fabricated with diameters ranging from 100 to 200 nm, aspect ratios (height to 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 are discussed.