Nanoparticles: Understanding the Polar Phases and Possible Ferrroelectricity*

Previous work revealed that 10 nm SrTiO3 (STO) nanoparticles host a polar and possibly ferroelectric phase stable under high pressure and over a broad range of temperatures. In this work, a full range of free standing nanoparticle samples between 2 and 60 nm have been studied and compared to bulk STO. Detailed structural and optical measurements are used to explore the evolution of the structure and corresponding phonon modes for varying temperatures and pressures. To understand the nature of the polar state and the existence of ferroelecricity, nonlinear optical measurements were conducted.