Measuring Device and Material ZT in a Thin-Film Si-Based Thermoelectric Microgenerator.

Pablo Ferrando-Villalba,Antonio Pablo Pérez-Marín,Aitor F Lopeandia,Gemma Garcia,Llibertat Abad,Gustavo Gonçalves Dalkiranis,Javier Rodriguez-Viejo

doi:10.3390/nano9040653

Pablo Ferrando-Villalba, Antonio Pablo Pérez-Marín + Show 5 more

Open Access

https://doi.org/10.3390/nano9040653

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Abstract

Thermoelectricity (TE) is proving to be a promising way to harvest energy for small applications and to produce a new range of thermal sensors. Recently, several thermoelectric generators (TEGs) based on nanomaterials have been developed, outperforming the efficiencies of many previous bulk generators. Here, we presented the thermoelectric characterization at different temperatures (from 50 to 350 K) of the Si thin-film based on Phosphorous (n) and Boron (p) doped thermocouples that conform to a planar micro TEG. The thermocouples were defined through selective doping by ion implantation, using boron and phosphorous, on a 100 nm thin Si film. The thermal conductivity, the Seebeck coefficient, and the electrical resistivity of each Si thermocouple was experimentally determined using the in-built heater/sensor probes and the resulting values were refined with the aid of finite element modeling (FEM). The results showed a thermoelectric figure of merit for the Si thin films of = 0.0093, at room temperature, which was about 12% higher than the bulk Si. In addition, we tested the thermoelectric performance of the TEG by measuring its own figure of merit, yielding a result of ZT = 0.0046 at room temperature.

Highlights

Thermoelectricity is the ability of some materials to produce voltage when exposed to a temperature gradient, and to produce a temperature gradient when electrons pass through them.The thermoelectric figure of merit of a material establishes the efficiency in energy conversion of the material, and it is defined as ZT = σS2 k, where σ is the electrical conductivity, S is the Seebeck coefficient and k is the thermal conductivity
We presented the thermoelectric characterization at different temperatures of the Si thin-film based on Phosphorous (n) and Boron (p) doped thermocouples that conform to a planar micro thermoelectric generators (TEGs)
The thermal conductivity, the Seebeck coefficient, and the electrical resistivity of each Si thermocouple was experimentally determined using the in-built heater/sensor probes and the resulting values were refined with the aid of finite element modeling (FEM)

Summary

Introduction

Thermoelectricity is the ability of some materials to produce voltage when exposed to a temperature gradient, and to produce a temperature gradient when electrons pass through them. An alternative means of characterization consists of separately measuring the three extrinsic parameters related ZT: the total heat conductance from the hot side to the cold side, the electrical resistance (produced by the active material plus the contact resistances), and the total Seebeck coefficient produced by all of the TEG legs. This is an advantageous approach when treating with microTEGs, where thermal dynamics are much faster than in bulk systems, the heat fluxes can be better controlled, and the thermal contact resistance between deposited films can be neglected. A 3D FEM was developed to subtract the current crowding effect in the electrical conductance measurements

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