Vanadium Dioxide Research Opens Door to New, Multifunctional Spintronic Smart Sensors

Research from a team led by North Carolina State University is opening the door to smarter sensors by integrating the smart material vanadium dioxide (VO₂) onto a silicon chip and using lasers to make the material magnetic. The advance paves the way for multifunctional spintronic smart sensors for use in military applications and next-generation spintronic devices.

VO2 is currently used to make infrared sensors. By integrating VO₂ as a single crystal onto a silicon substrate, the researchers have made it possible to create infrared smart sensors, in which the sensor and computational function are embedded on a single chip. This makes the sensor faster and more energy efficient, since it doesn’t have to send data to another chip to be processed. Smart sensors are also lighter than conventional ones, since separate chips aren’t necessary.

“For military applications, sensor technology needs to be able to sense, manipulate, and respond to data quickly – and this work achieves that,” says Dr. Jay Narayan, John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and senior author of a paper describing the work.

In addition, the researchers used high-power nanosecond-pulsed laser beams to modify the VO₂ and make it magnetic. This will allow the creation of spintronic smart sensors that incorporate infrared sensors and magnetic sensors on a single chip. Spintronics refers to technologies used in solid-state devices that take advantage of the inherent spin in electrons and their related magnetic momentum. The potential advantages of spintronics include higher memory capacity, faster data transfer and more computational power on a computer chip.

The paper, “Diamagnetic to ferromagnetic switching in VO₂ epitaxial thin films by nanosecond excimer laser treatment,” is published online in Applied Physics Letters. Lead author of the paper is R. Molaei, a Ph.D. student at NC State. Co-authors include Dr. R. Bayati, a former Ph.D. student at NC State who now works at Intel Corporation; Dr. S. Nori, a postdoctoral researcher at NC State; Dr. D. Kumar, of North Carolina A&T University; and Dr. J.T. Prater of the Army Research Office, who is also an adjunct professor at NC State. The work was supported by the National Science Foundation, under grants DMR-1304607 and DMR-0803663.

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Note to Editors: The study abstracts follow.

“Diamagnetic to ferromagnetic switching in VO2 epitaxial thin films by nanosecond excimer laser treatment”

Authors: R. Molaei, S. Nori, and Jay Narayan, North Carolina State University; R. Bayati, Intel Corporation; D. Kumar, North Carolina A&T University; J.T. Prater, North Carolina State University and Army Research Office.

Published: Online Dec. 20, 2013, Applied Physics Letters

Abstract: VO₂(010)/NiO(111) epitaxial heterostructures were integrated with Si(100) substrates using a cubic yttria-stabilized zirconia (c-YSZ) buffer. The epitaxial alignment across the interfaces was determined to be VO2(010)‖NiO(111)‖c-YSZ(001)‖Si(001) and VO2[100]‖NiO(110)‖c-YSZ(100)‖Si(100). The samples were subsequently treated by a single shot of a nanosecond KrF excimer laser. Pristine as-deposited film showed diamagnetic behavior, while laser annealed sample exhibited ferromagnetic behavior. The population of majority charge carriers (e−) and electrical conductivity increased by about two orders of magnitude following laser annealing. These observations are attributed to the introduction of oxygen vacancies into the VO₂ thin films and the formation of V³⁺ defects.