Collaborative Research/GOALI: Engineered Crystallization Behavior of Phase Change Materials to Enable Advanced Optical Functionalities

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NON-TECHNICAL DESCRIPTION: Tunable optical components, ones where their properties can be altered to realize different physical and optical behavior, are of widespread interest for diverse applications ranging from spectroscopy to imaging. Most of these components sacrifice optical performance for tunability and they are manufactured using structures and processes that are difficult to miniaturize. In this collaborative project, researchers from the University of Central Florida, Pennsylvania State University, and Lockheed Martin are optimizing infrared chalcogenide materials and nanostructures that exhibit reversible amorphous-to-crystalline phase transitions to have tailored refractive index values and dispersive properties that are continuously tunable. The availability of such chalcogenide phase change materials will enable the development of new compact, tunable optical components by exploiting the exceptionally large refractive index change associated with the phase transition. The chalcogenide materials and processes being developed in this project are broadly available through the NSF-funded National Nanotechnology Infrastructure Network.TECHNICAL DESCRIPTION: Optical materials with compositionally tailored properties that are spectrally tunable and reversible are attractive for producing optical components with unique functionalities. Chalcogenide phase change materials (PCMs) exhibit rapid and reversible amorphous-to-crystalline phase transitions in response to pulsed thermal, optical, or electrical stimuli. However, current optical devices based on chalcogenide PCMs have only exploited the large change in optical reflectance associated with the transition between the pure amorphous and the pure crystalline states of the material. In this collaborative project, researchers from the University of Central Florida, Pennsylvania State University, and Lockheed Martin are conducting experimental studies to identify a chalcogenide composition that enables controlled nucleation and growth of spatially dispersed nanocrystals, which will produce a continuously tunable and reproducible change in the infrared refractive index and dispersion of the composite glass ceramic material. For each composition, bulk, thin film, and nanopatterned films are being characterized to understand the role of device-relevant boundary conditions on the nucleation and growth process induced by external optical or thermal excitation. Complementary techniques are being applied to understand the fundamental relationship between the intrinsic material response and the tailored optical performance, including thermal, structural, and optical measurement and analysis. The structure-property data being collected during this project will provide the critical input needed to design fully tunable optical components using chalcogenide PCMs. A new mentoring team program, which links university and industry partnered researchers, trains graduate and undergraduate students to have globally-relevant workforce skills. The chalcogenide phase change materials and processes being developed in this project are available to the broader external academic and industrial community through the NSF-funded National Nanotechnology Infrastructure Network (NNIN) located at Pennsylvania State University.