Reconfigurable nanowires phononics for temperature sensing

Nanotechnology opens up novel opportunities to develop sensors and energy convertors that can be used in a wide range of applications. Due to their small size and increased functionality they can be integrated into systems with low “real-estate” cost while offering real-time asset monitoring for increased control and energy efficiency. An area where nanotechnology can have a large impact is phononics – the science of controlling heat conduction in systems – and thermoelectric (TE) applications. Decreasing the structure size allows electrical transport but hinders phonon (heat) transport. Thus, nanowire (NW)-based systems can boost the performance of TE generation and cooling, and may enable key absent technologies such as on-chip heat management and storage, heat recovery and information processing in thermal form for systems such as heat sensors and generators. In the proposed work, the combined control of phonon and electron transport will be used to implement temperature sensing and data processing. This will be achieved by fabricating semiconducting NWs for phonon-filtering with Schottky barrier contacts for electron energy filtering. Nanoscale metal-semiconductor (MS) contacts have the ability to increase the Schottky barrier height that controls hot electron injection from the metal into the semiconductor. It is known that the introduction of high potential barriers in the carrier stream increases the Seebeck coefficient and thus increases the open circuit voltage for a given temperature difference. The NW structure itself blocks the phonon transport to maintain a large temperature difference. Electron energy filtering via potential barriers has been previously explored in semiconductor-semiconductor junctions. MS junctions have been found to be less efficient. However, nanoscale Schottky contacts are expected to change the physical processes at the interface that could lead to increased potential barriers and better energy filtering. This makes NWs, in which the phonon transport is hindered, a suitable candidate for temperature sensing. In order to make the sensor active, it can be integrated in reconfigurable NW FETs (RFETs). RFETs are built on intrinsic NWs and have Schottky source and drain contacts. RFETs can operate with both n and p-type functionality depending on the program gate. Our hypothesis is that gating the source and drain contact junctions can control the energy filtering process and control electrical and thermal transport through the NWs. The combination of reconfigurable NWs with Schottky barrier energy filtering for temperature sensing has not yet been explored but offers future possibilities for monolithically integrated on-chip heat management, recovery and storage systems. The PhD research involves simulations studies and design of reconfigurable NWs, followed by fabrication and characterisation of the system.

J. E. Velazquez-Perez
J. E. Velazquez-Perez

Prof. J. E. Velazquez-Perez has over 25 years of experience in simulation (both TCAD and Monte Carlo models) and design of semiconductor devices for high speed (mm-waves and THz) and thermoelectronic applications and theory. He was a visiting researcher at ICL for several periods between 1998 and 2004, working with KF on SiGe FETs. He co-founded the USAL NanoLab that opened in 2014. Fabrication in the NanoLab focuses on THz, thermoelectric and sensing devices. He has led 15 R&D projects, published around 55 journal papers, 3 book chapters, made over 100 contributions to conferences and holds 1 patent.

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