Size-dependent polar ordering in colloidal GeTe nanocrystals.

Polking, Mark J; Urban, Jeffrey J; Milliron, Delia J; Zheng, Haimei; Chan, Emory; Caldwell, Marissa A; Raoux, Simone; Kisielowski, Christian F et al. · Nano Lett · 2011

basic_science · Level V

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Abstract

The question of the nature and stability of polar ordering in nanoscale ferroelectrics is examined with colloidal nanocrystals of germanium telluride (GeTe). We provide atomic-scale evidence for room-temperature polar ordering in individual nanocrystals using aberration-corrected transmission electron microscopy and demonstrate a reversible, size-dependent polar-nonpolar phase transition of displacive character in nanocrystal ensembles. A substantial linear component of the distortion is observed, which is in contrast with theoretical reports predicting a toroidal state.