Dynamics of Nanometer Gap Formation in Thermo-Tunneling Devices for Energy Conversion

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Thermo-tunneling is a term used to describe combined emission of hot electrons (thermionic emission) and tunneling of electrons through a narrow potential barrier between two surfaces (field emission). Thermo-tunneling of hot electrons across a few-nanometer gap has application to vacuum electronics and flat panel displays, and holds great potential in thermo-electric cooling and energy generation. Theoretical and experimental studies on thermo-tunneling nano-structures have shown that the heat removal efficiency of these structures could approach the theoretical limit known as Carnot efficiency. This project aims to test a new method for constructing thermo-tunneling devices by forming a very narrow (1 nanometer wide) vacuum gap across two very smooth surfaces. Unfortunately, establishment of a nanometer vacuum gap over sufficiently large areas required for practical use of thermo-tunneling devices is very challenging and so far has not been demonstrated. The goal of this proposal, therefore, is to explore and demonstrate the feasibility of creating nanometer vacuum gaps over extended areas using a dynamic equilibrium between Lorentz, Van der Waals, and electrostatic forces. The methods of modern dynamical system analysis and boundary control of distributed parameter systems will be applied to demonstrate theoretically and experimentally the feasibility of forming such gaps and to produce a new class of high-efficiency energy conversion devices. If successful, the proposed research will result in a novel nanometer gap-forming technique that can be used in solid-state cooling devices, solid-state thermoelectric generators, and high-speed vacuum electronic devices for defense (radiation hard) applications. The energy conversion efficiency of such devices approaches the thermodynamic (Carnot) limit, therefore the project could lead to tremendous energy savings in cooling and power-generation applications by replacing mechanical compressors in cooling applications, or producing a more efficient thermo-electric generators. The research will provide invaluable training opportunities for graduate students in the Applied Mathematics Interdisciplinary Program at the University of Arizona and for graduate student exchange with the world-renowned Department of Applied Mechanics at the Budapest Technical University of Technology and Economics.