Polar State in Freestanding Strontium Titanate Nanoparticles

Monodispersed strontium titanate nanoparticles were prepared and studied in detail. It is found that $\sim$ 10 nm as-prepared stoichiometric nanoparticles are in a polar structural state (with possibly ferroelectric properties) over a broad temperature range. A tetragonal structure, with possible reduction of the electronic hybridization is found as the particle size is reduced. In the 10 nm particles, no change in the local Ti-off centering is seen between 20 and 300 K. This work is supported by DOE Grant DE-FG02-07ER46402.