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

热光子学对热-功率转换、非接触式热管理、热成像和激光制造至关重要，在这些领域，动态可调的热发射或热吸收是非常需要的，具有很强的可控性和多功能性。我们的目标是利用金属氧化物半导体（MOS）纳米结构来实现热流超过远场黑体极限的电调谐对辐射传热的显著调制。该项目的成功将最终导致可调热电转换，热控制，热电路与热光子手段的新应用。研究成果将通过期刊出版物、会议报告和课程教学迅速传播。ppi将培训下一代劳动力，重点是让女性和少数族裔学生等代表性不足的群体更广泛地参与进来。研究生将学习多学科的基础知识，这将为他们解决未来工程领域的能源挑战做好准备。亚利桑那州立大学和亚利桑那大学的本科生研究项目为本科生提供了参与pi实验室研究活动的绝佳机会。这些pi将通过亚利桑那州立大学和亚利桑那大学的各种外展项目吸引当地K-12学生，旨在激发他们对STEM的兴趣。已知平面MOS结构的电容随栅极电压的变化而变化，导致半导体内自由载流子的耗尽或积累，但这种变化只发生在非常靠近氧化物界面的超薄活性区，约为10 nm（德拜长度）。当平面半导体的红外穿透深度在微米量级时，这种超薄有源区域内的吸收变化几乎不能引起整个结构内明显的调制吸收/发射。所提出的近场MOS纳米结构将通过利用带有包裹超薄金属电极和氧化栅极层的翅片场效应晶体管以及近场效应来克服这一挑战。在直径为几十纳米的半导体纳米结构中，载流子浓度会随着电栅的损耗或积累而发生显著变化。纳米结构层介电函数的剧烈变化将导致电调制的近场辐射传热。通过将MOS纳米结构放置在具有纳米间隙距离的发射表面附近，可以产生耦合倏逝波的近场效应，从而显著提高辐射能量，超过远场黑体极限。拟议的研究项目将结合理论和实验任务进行，包括设计和理论建模，样品制造和表征，近场测量和计量发展，以及验证和优化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.