Improved thermal isolation of silicon suspended platforms for an all-silicon thermoelectric microgenerator based on large scale integration of Si nanowires as thermoelectric material

Fonseca, L.; Dönmez, İnci; Salleras, M.; Calaza, C.; Gadea, Gerard; Santos, Jose-Domingo; Morata, Álex; Tarancón, Albert

doi:10.1088/1742-6596/660/1/012113

Cited by 2 publications

(1 citation statement)

References 5 publications

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“…An interesting engineering approach to that problem is to design an arbitrary long bridging distance between the platform and the surrounding silicon rim and to populate it with appropriated equi-spaced silicon trenches, which will be occupied by silicon NWs at the same time in a single well-optimized CVD process for that reasonable length target. Additional thermal performance improvements have been added to the presented architecture by modifying the ancillary supports for the metal legs in order to increase also their thermal resistance [ 30 , 31 ]. Such ancillary supports were long and narrow bulk silicon bridges in earlier generations and wide, short and thin nitride supports in the later generations.…”

Section: Methodsmentioning

confidence: 99%

Transitioning from Si to SiGe Nanowires as Thermoelectric Material in Silicon-Based Microgenerators

et al. 2021

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The thermoelectric performance of nanostructured low dimensional silicon and silicon-germanium has been functionally compared device-wise. The arrays of nanowires of both materials, grown by a VLS-CVD (Vapor-Liquid-Solid Chemical Vapor Deposition) method, have been monolithically integrated in a silicon micromachined structure in order to exploit the improved thermoelectric properties of nanostructured silicon-based materials. The device architecture helps to translate a vertically occurring temperature gradient into a lateral temperature difference across the nanowires. Such thermocouple is completed with a thin film metal leg in a unileg configuration. The device is operative on its own and can be largely replicated (and interconnected) using standard IC (Integrated Circuits) and MEMS (Micro-ElectroMechanical Systems) technologies. Despite SiGe nanowires devices show a lower Seebeck coefficient and a higher electrical resistance, they exhibit a much better performance leading to larger open circuit voltages and a larger overall power supply. This is possible due to the lower thermal conductance of the nanostructured SiGe ensemble that enables a much larger internal temperature difference for the same external thermal gradient. Indeed, power densities in the μW/cm2 could be obtained for such devices when resting on hot surfaces in the 50–200 °C range under natural convection even without the presence of a heat exchanger.

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Section: Methodsmentioning

confidence: 99%

Transitioning from Si to SiGe Nanowires as Thermoelectric Material in Silicon-Based Microgenerators

et al. 2021

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Power Response of a Planar Thermoelectric Microgenerator Based on Silicon Nanowires at Different Convection Regimes

Santos

Salleras

Dönmez

et al. 2016

Energy Harvesting and Systems

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A thermoelectric microgenerator based on multiple silicon nanowire arrays is fabricated and its performance evaluated for different convection regimes. Mature silicon microfabrication technology is used to fabricate the device structure. As a post-process, a bottom-up approach is used to grow silicon nanowires by a VLS-CVD mechanism. The thermal design of the microgenerator features a thermally isolated silicon platform which is connected to the bulk silicon rim through several arrays of silicon nanowires. Simulations are carried out to evaluate the need of an external heat sink to improve the thermal gradient seen by the nanowires and the power output of the microgenerator. Results show a significant improvement with a heat sink raising the thermal gradient from 3 K to approximately 100 K when the external temperature gradient is 300 K. Experimental measurements with different convection regimes also show a radical improvement on the power output comparing natural convection and two different forced convection regimes. The first forced convection regime is a broad airflow from a commercial CPU fan placed on top of the device, while the second (air jet forced convection) uses a syringe to focus the airflow from the compressed air line to the platform. The maximum output power for a natural convection regime is 2.2 nW for a hotplate temperature of 200°C, while the air jet forced convection regime generates up to 700 nW, which correspond to 35 µW/cm 2 considering a device footprint of 2 mm 2 .

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Improved thermal isolation of silicon suspended platforms for an all-silicon thermoelectric microgenerator based on large scale integration of Si nanowires as thermoelectric material

Cited by 2 publications

References 5 publications

Transitioning from Si to SiGe Nanowires as Thermoelectric Material in Silicon-Based Microgenerators

Transitioning from Si to SiGe Nanowires as Thermoelectric Material in Silicon-Based Microgenerators

Power Response of a Planar Thermoelectric Microgenerator Based on Silicon Nanowires at Different Convection Regimes

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