EAGER: Micro and Nanoscale Thin Film Pyroelectric Materials via Strain Engineering

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As thermal energy is ubiquitous and abundant, many materials, structures, and strategies have been studied and developed to harness heat energy. In applications where self-powered devices are preferred (for example, bio-implanted devices and extraterrestrial field robots), the ability to harvest the waste thermal energy from the ambient environment by small devices is needed. Micro and nanoscale pyroelectric materials and devices are one possible solution, as they can convert small and irregular temperature fluctuations into electricity. However, their extremely low power density is a major obstacle preventing practical applications. This EArly-concept Grant for Exploratory Research (EAGER) award supports research on designing, fabricating and achieving technologically useful micro and nanoscale thermal-to-electrical energy conversion materials and devices by elastic strain engineering. The research has potentially broad impacts on the development of environmentally-friendly thermal devices for sustainable energy harvesting. This research has potential to benefit the US economy in the sector of clean energy. In addition, the researchers will to reach out to K-12 students at local high schools through the demonstration of nanodevices for energy conversion.The objective of this research is to explore a potentially transformative micro and nanoscale pyroelectric hybrid thin film material with giant thermoelectric Figure of Merit. The innovative key concept is the transfer of the ultrafast thermal phase transition of strongly correlated oxides with colossal lattice dilation/contraction to conventional pyroelectric material. The material's pyroelectric coefficient is expected to be two to three orders of magnitude higher than conventional pyroelectrics. Specific aims are to demonstrate the fabrication of high-quality pyroelectric VO2/ZnO hybrid thin film system, and characterize the high Figure of Merit metrics in these materials and structures. The PIs will fabricate the materials and structures by radio frequency sputtering and optical lithography, and test the individual components' pyroelectric properties and the hybrid material's synthetic functionalities and performances. The PIs will explore the upper limit of the hybrid's high materials metrics in terms of pyroelectric coefficient, Figure of Merit, and power density. These activities will be designed and guided by computational modeling efforts. The intellectual significance of the work includes: new understanding on the unique design and working mechanism of pyroelectric materials; quantitative understanding and modeling of coupled processes including ultrafast phase transition, heat flow, strain/stress, and electrical polarization.