Urbana-Champaign, IL--Researchers at the University of Illinois at Urbana-Champaign have found that reducing the dimensions of ferroelectrics increases their susceptibility to the size- and strain-induced effects that make then valuable for pyroelectric night-vision and other IR sensors. Rather than conventional bulk materials, future nanoscale pyroelectric devices will increasingly require ferroelectric thin films.
“Measuring the pyroelectric response of thin films is difficult and has restricted the understanding of the physics of pyroelectricity, prompting some to label it as ‘one of the least-known properties of solid materials,'” says Lane Martin, an assistant professor of materials science and engineering (MatSE) at Illinois. “This work provides the most complete and detailed modeling and experimental study of this widely unknown region of materials and has direct implications for next-generation devices."
The group’s paper, “Effect of 90-degree domain walls and thermal expansion mismatch on the pyroelectric properties of epitaxial PbZr0.2Ti0.8O3 thin films,” appears in the journal Physical Review Letters.
“By moving to a ‘bottom-up’ approach that produces nanoscale versions of these materials as thin films, we have observed, for the first time, that certain features, namely domain walls, can be incredibly important and even dominate the temperature-dependent response and performance of these materials," says Martin.
According to J. Karthik, a MatSE graduate researcher and the lead author on the group’s paper, thin-film epitaxy has been developed to provide a set of parameters (for example film composition, epitaxial strain, electrical boundary conditions, and thickness) that allow for precise control of ferroelectrics and has been instrumental in understanding the physics of dielectric and piezoelectric effects.
“We investigated the contribution of 90º domain walls and thermal expansion mismatch to pyroelectricity in ferroelectric PbZr0.2Ti0.8O3 thin films, a widely used material whose bulk ferroelectric and piezoelectric properties are well understood,” says Karthik.
This research was supported by the Office of Naval Research, the Army Research Office, and the Air Force Office of Scientific Research.
John Wallace | Senior Technical Editor (1998-2022)
John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.