FIB milled PZT nanocapacitors tested using PFM

Recently there has been much interested on the generation of nanoscale ferroelectric islands to determine the minimum size that ferroelectric material can sustain inherent ferroelectric behaviour. In this paper we report the generation of ferroelectric capacitors with surface areas ranging from 6 × 10 ^-14 to 3 × 10 ^-12 m ² in the form of circular capacitors with lateral diameters between 90 nm and 2 μm. We have shown that these capacitors exhibit piezoelectric behaviour by studying the response to applied electric fields though the technique of piezo-force-response microscopy (PFM Capacitors show typical 'butterfly' type loops to a quasi DC applied field and enhanced displacements consistent with those measured from capacitive structures fabricated from epitaxial lead zirconium titanate (PZT) films [1]. Piezoresponse force microscopy (PFM) was used to measure the piezoresponse of nanocapacitors with lateral diameters between 90 nm to 2 μm incorporating Pb(Ti _0.7, Zr _0.3)O ₃ (PZT(30/70). A conductive cantilever with a 10 V (±5 V) low frequency signal applied, back electrode held at ground. Electromechanical deformation induced by the alternating field was measured by the deflection of the cantilever; piezoelectric loops were obtained by plotting displacement against time-varying voltage. Enhanced displacement up to 4 times predicted for (PZT(30/70) was observed for capacitors of 200 nm and 300 nm diameter. Calculated δ ₃₃ values for the capacitors were found to vary from 70 pmV ^-1 to 250 pmV ^-1. The coercive field was found to be 10 (+/-2) Vμm ^-1 for all structures characterized.