Collaborative Research: Electrically Modulated Near-field Thermophotonics with Metal-Oxide-Semiconductor Nanostructures

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Collaborative Research: Electrically Modulated Near-field Thermophotonics with Metal-Oxide-Semiconductor Nanostructures Thermophotonics is crucial to heat-to-power conversion, non-contact thermal management, thermal imaging, and laser manufacturing, where dynamically tunable thermal emission or absorption are highly desired with great controllability and versatility. We aim to employ metal-oxide-semiconductor (MOS) nanostructures to achieve significant modulation of radiative heat transfer via electrical tuning with heat flux exceeding the far-field blackbody limit. The success of this project would ultimately lead to novel applications of tunable thermoelectric conversion, heat control, thermal circuits with thermophotonic means. The research outcomes will be quickly disseminated through journal publications, conference presentations and course teaching. The PIs will train the next generation of workforce with an emphasis on broader participation of underrepresented groups such as female and minority students. Graduate students will learn the fundamentals of multiple disciplines, which will well prepare them for solving future energy challenges in engineering communities. The undergraduate research programs at ASU and UA offer a great opportunity for undergraduate students to participate in the research activities in the PIs’ labs. The PIs will engage local K-12 students through various outreaching programs at ASU and UA, aiming to spark their interests in STEM. It is known that the capacitance of planar MOS structures varies with the gate voltage which causes depletion or accumulation of free charge carriers within the semiconductor, but it occurs only in the ultrathin active region very close to the oxide interface on the order of ~10 nm approximated by the Debye length. With the infrared penetration depth of planar semiconductor on the order of micrometers, the absorption variation within such ultrathin active region could barely cause appreciable modulation absorption/emission within the whole structure. The proposed near-field MOS nanostructure would overcome this challenge by utilizing a fin field-effect transistor with the wrap-around ultrathin metal electrode and oxide gate layers as well as near-field effect. The carrier concentration of the semiconductor nanostructures whose diameter is about several tens of nanometers will change significantly with depletion or accumulation upon electrical gating. The drastically varied dielectric functions of the nanostructure layer will lead to electrically modulated near-field radiative heat transfer. By placing the MOS nanostructure in close proximity to an emitting surface with nanometric gap distances, the near-field effect with coupled evanescent waves could occur to enhance the radiative energy significantly surpassing the far-field blackbody limit. The proposed research project will be carried out with a combination of theoretical and experimental tasks including design and theoretical modeling, sample fabrication and characterization, near-field measurements and metrology development, as well as validation and optimization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.