The result on his computer screen looked impossible.Late one night in 2009, Nate Orloff was alone in a laboratory, analyzing measurements from a set of experimental thin films sent to him by Darrell Schlom, the Tisch University Professor in Cornell University’s Department of Materials Science and Engineering.
Nate Orloff as a graduate student measuring Ruddlesden-Popper materials circa 2009, work that led to the first evidence that the material family could be electrically tuned.
“I jumped out of my chair and shouted, ‘Eureka,’” said Orloff, who at the time was a graduate student at the University of Maryland. “My computer immediately fell off the desk, crashed to floor, and broke the headphone jack.”What Orloff saw that night would help launch a scientific journey spanning 17 years, multiple institutions and generations of graduate student researchers.That journey culminated June 15 in a paper by a multi-disciplinary team published in Nature Electronics and the achievement of what was one of the most elusive goals in microwave electronics.‘Crazy Ruddlesden-Popper things’For more than two decades, scientists searching for better materials for wireless electronics have faced a seemingly unavoidable tradeoff: A material could be tunable – able to change its electrical properties on demand by applying a voltage – or efficient, losing very little energy as heat. Getting both properties at once could improve components used in wireless communications, radar systems, satellites and other devices that rely on controlling microwave signals with precision.A federal research program was initiated in 1999 to find such materials. Nearly every scientific team involved focused on using barium strontium titanate – all but one.“Our team was the only one working on these crazy Ruddlesden-Popper things that most considered a dead-end approach,” Schlom said.The layered crystalline materials, known as Ruddlesden-Popper thin films, were prized for exceptionally low energy loss at microwave frequencies. But according to the accepted understanding of their crystal symmetry, they shouldn't have been able to provide the tunability needed for practical devices.
