PNNL

Abstract

SrTiO3 (STO) is an incipient ferroelectric perovskite oxide for which the onset of ferroelectric order is suppressed by quantum fluctuations1,2. This property results in a very large increase in dielectric constant from ~300 at room temperature to ~20,000 at liquid He temperature in bulk single crystals 2. However, the low-temperature dielectric constant of epitaxial STO films is typically a few hundred, and has never exceeded a few thousand3,4. Here we use all-epitaxial capacitors of the form n-STO/undoped STO/n-STO(001) prepared by hybrid molecular beam epitaxy, to demonstrate intrinsic dielectric constants exceeding 25,000. We show that the n-STO/undoped STO interface plays a vital role in determining the dielectric properties and must be properly accounted for to determine the intrinsic dielectric constant. These results provide new insights into the interpretation of the electronic properties of STO-based complex oxide heterostructures.