Electromechanical Manipulation of Topological Defects to Yield Giant Piezoelectric Response in Epitaxial Lead Zirconate Titanate Bilayers on Silicon

The combination of topological defect mobility and exploitation of the boundary conditions in bilayer heterostructures presents an enormous opportunity for enhancing actuation responses from modest external stimuli in electromechanical applications. Tetragonal PbZr0.3Ti0.7O3 and underlying rhombohedral PbZr0.54Ti0.46O3 ferroelectric bilayers are epitaxially grown on silicon substrates. The topmost layer shows crystallographic symmetry lower than a typical tetragonal structure but is arranged in-plane with a mosaic pattern of superdomains and ferroelastic a1/a2 nanodomains within. The domain pattern also shows a series of vortex/anti-vortex pairs induced in the pseudo-tetragonal film, which can be manipulated to either migrate across the film or annihilate one another in the presence of an external electrical bias. The mobility of defect pairs and domain walls, through reduced substrate clamping by the underlying rhombohedral film, is the driving force for endowing the bilayer with a approximate to 45% increased effective d(33) response compared to a rhombohedral single layer on silicon. Furthermore, a square in-plane polarization loop (approximate to 32 mu C cm(-2)) provides further evidence of the mobility and large-scale polarization switching. An improvement of this magnitude demonstrates the opportunity to implement bilayer technology while exploiting a functional silicon substrate for enhanced, industry-ready, smart material applications.

Automated summary

The combination of topological defect mobility and exploitation of boundary conditions in bilayer heterostructures has led to an approximate 45% increase in effective d(33) response compared to a single layer on silicon, demonstrating the potential for enhanced actuation responses. The bilayer structure also exhibits large-scale polarization switching on a silicon substrate.