Room-temperature ferroelectricity in strained SrTiO3
Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature are useful for devices. Adjusting the ferroelectric transition temperature (T-c) is traditionally accomplished by chemical substitution - as in BaxSr1-xTiO3, the material widely investigated for microwave devices in which the dielectric constant (epsilon(r)) at GHz frequencies is tuned by applying a quasi-static electric field(1,2). Heterogeneity associated with chemical substitution in such films, however, can broaden this phase transition by hundreds of degrees(3), which is detrimental to tunability and microwave device performance. An alternative way to adjust Tc in ferroelectric films is strain(4-8). Here we show that epitaxial strain from a newly developed substrate can be harnessed to increase Tc by hundreds of degrees and produce room-temperature ferroelectricity in strontium titanate, a material that is not normally ferroelectric at any temperature. This strain-induced enhancement in T-c is the largest ever reported. Spatially resolved images of the local polarization state reveal a uniformity that far exceeds films tailored by chemical substitution. The high er at room temperature in these films ( nearly 7,000 at 10 GHz) and its sharp dependence on electric field are promising for device applications(1,2).
Schlom, Dg Penn State Univ, Dept Mat Sci & Engn, University Pk, PA 16802 USA Penn State Univ, Dept Mat Sci & Engn, University Pk, PA 16802 USA Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA USN, Res Lab, Washington, DC 20375 USA Inst Crystal Growth, D-12489 Berlin, Germany Univ Michigan, Dept Mat Sci & Engn, Ann Arbor, MI 48109 USA Los Alamos Natl Lab, Mat Sci & Technol Div MST8, Los Alamos, NM 87545 USA Motorola Labs, Tempe, AZ 85284 USA Ecole Polytech Fed Lausanne, Lab Ceram, CH-1015 Lausanne, Switzerland Argonne Natl Lab, Div Mat Sci, Argonne, IL 60439 USA
Cited References Count:31
Record created on 2006-08-21, modified on 2016-08-08