In July, a research team headed by Alexander Gray, assistant professor of physics, completed the construction and testing of a unique university-based instrument to study complex multilayer quantum material systems. Gray's hard X-ray photoemission spectrometer, equipped with a six-axes cryogenic goniometer and a wide-acceptance-angle electrostatic electron analyzer, is the first such laboratory-based system in the U.S. and the most versatile lab-based hard X-ray system in the world.
"The ever-growing demand for miniaturization and increased speeds in next-generation electronic devices has taken science to the quantum frontier, a frontier where emergent nanoscale phenomena require us to clearly differentiate among the properties found at the surfaces, the bulk or interiors and the interfaces of various materials," says Gray. "These types of measurements require an extremely energetic source of X-rays."
It is possible to conduct such research at a handful of large-scale synchrotron radiation sources at several national and international laboratories. However, the demand is so high that individual researchers often are limited to using such technology only a few days per year, and after a rigorous international peer-review competition process, according to Gray.
"We expect that this system will change the way in which hard X-ray photoemission experiments are currently carried out," says Gray, who is also a researcher with the Temple Materials Institute. "Without the need for a synchrotron source and with unlimited continuous experimental time, we can now carry out comprehensive studies which cannot be done elsewhere."
According to Gray, modern day devices consist of many layers of different materials. "This instrument allows us to probe beyond the surface layers, and to see what's happening in the entire device, including buried layers and interfaces," Gray explains. "Gaining such an understanding is not just important for basic science, but could be potentially transformative to modern computing. It could bring us closer to new devices that can be operated with minimal energy expenditure, at speed limits governed only by the fundamental laws of physics."
Temple's new spectrometer can measure such novel devices while they are actually operating. Gray is currently researching the interfaces between different oxide materials, which are relevant for the next-generation memory and logic devices. He is also investigating so-called quantum materials, materials which exhibit sharp changes in electronic properties at their surfaces and interfaces with other materials. This amazing property gives rise to a myriad of new functionalities and thus holds significant promise as a powerful materials platform for spintronic and quantum devices.
Gray spent the past four years designing and building the new instrument. The bulk of it was funded by Temple University as part of his laboratory start-up funding. The last critical item, a state-of-the-art wide-acceptance-angle photoelectron analyzer, was funded by a $200,000 grant from the Army Research Office and $100,000 from the College of Science and Technology's Dean's Office.
Gray is a recent recipient of the U.S. Army Research Office Young Investigator Program award, as well as the U.S. Department of Energy's Early Career Research Program award.