Ferroelectric Properties of PbZrO₃/PbTiO₃ Artificial Superlattices by Scanning Probe Microscopy

Abstract

PbZrO₃ (PZO)/PbTiO₃ (PTO) artificial superlattices have been grown on La_0.5Sr_0.5CoO₃ (LSCO) (100)/MgO (100) substrate by pulsed laser deposition (PLD) with various stacking periods from 1 to 100 unit-cells. The ferroelectric properties of the superlattices were investigated by scanning probe microscopy (SPM). We have compared the superlattices to Pb(Zr_0.5Ti_0.5)O₃ (PZT) thin films with respect to topographic features (roughness and grain size) and local polarization behavior. The polarization of PZT and superlattices was evaluated by measuring the surface potential using Kelvin force microscopy (KFM). The roughness and grain size of the superlattices were smaller than that of PZT thin films. The surface potential of superlattice with a 2 unit cell-stacking period (PZO₂/PTO₂) was as large as 1009 mV compared to PZT thin films with same thickness (i.e., 50 nm). As the total thickness of PZO₂/PTO₂ decreased, the corresponding surface potential decreased. The polarized domain size of the superlattice was dependent of the applied voltage pulse. The polarized domain as small as 80 nm in 20 nm thick PZO₂/PTO₂ superlattice was formed by applying 1 s pulse of −1 V.

Keywords:

• PbZrO₃/PbTiO₃ artificial superlattices
• pulsed laser deposition
• SPM
• surface potential

ACKNOWLEDGEMENTS

This work is partially supported by the Korea Ministry of Science and Technology through the National R&D Project for Nano Science and Technology (Project M1-0212-29-0000).