Note: Improvement of the 3<i>ω</i> thermal conductivity measurement technique for its application at the nanoscale

Pennelli, Giovanni; Dimaggio, Elisabetta; Macucci, Massimo

doi:10.1063/1.5008807

Cited by 13 publications

(9 citation statements)

References 20 publications

(20 reference statements)

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“…For the proper application of the 3ω technique it is essential to choose the correct model for data reduction. Although an analytical model has been developed for 2D structures [23] (thin membranes), in our case we have fitted the data by means of an approach based on FEM (Finite Element Method) simulations that we have developed [24], using the thermal conductivity as a fitting parameter. The simulation takes into account the thermoelectric transport in the metal and in the silicon nanostructures, considering the measured electrical conductivities.…”

Section: Device Fabricationmentioning

confidence: 99%

Thermal Conductivity Reduction in Rough Silicon Nanomembranes

Pennelli

Dimaggio

Macucci

2018

IEEE Trans. Nanotechnology

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Nanostructured silicon is a promising material for thermoelectric conversion, because the thermal conductivity in silicon nanostructures can be strongly reduced with respect to that of bulk materials. We present thermal conductivity measurements, performed with the 3ω technique, of suspended monocrystalline silicon thin films (nanomembranes or nanoribbons) with smooth and rough surfaces. We find evidence for a significant effect of surface roughness on phonon propagation: the measured thermal conductivity for the rough structures is well below that predicted by theoretical models which take into account diffusive scattering on the nanostructure walls. Conversely, the electrical conductivity appears to be substantially unaffected by surface roughness: the measured resistance of smooth and rough nanostructures are comparable, if we take into account the geometrical factors. Nanomembranes are more easily integrable in large area devices with respect to nanowires and are mechanically stronger and able to handle much larger electrical currents (thus enabling the fabrication of thermoelectric devices that can supply higher power levels with respect to current existing solutions). * g.pennelli@iet.unipi.it, tel. +39 050 2217 699, fax. +39 050 2217522

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Section: Device Fabricationmentioning

confidence: 99%

Thermal Conductivity Reduction in Rough Silicon Nanomembranes

Pennelli

Dimaggio

Macucci

2018

IEEE Trans. Nanotechnology

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“…In the specific case of this work, the fabricated devices can be used for the measurement of the thermal conductivity of the grids of nanostructures. Future work will consist in applying an all-electrical technique, such as the three ω method [13], for thermal conductivity measurement: to this end, it will be exploited the Joule heating achieved by the bias of the metal resistor fabricated at the center of the grids. Moreover, the fabrication process will be improved to achieve nanostructures 100 nm wide and 1 µm tall.…”

Section: Discussion and Future Workmentioning

confidence: 99%

On-chip all-silicon thermoelectric device

Masci¹,

Dimaggio²,

Pennelli³

2021

Preprint

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“…The electrical conductivity was calculated from the measured values of resistance ( R ) and the morphological data of the NW, from room temperature to 620 K. Thermal conductivity measurements were performed with AC measurements, applying the 3ω method, and using a Standford Research SR830 Lock‐in amplifier for acquiring the third harmonic signal and as the voltage output source. [ 92 ] A balance resistor in series with the NW was used for current control (Figure S9, Supporting Information). [ 93 ] Further details on the approaches followed and on the set‐up are given in Supporting Information Section S6.…”

Section: Methodsmentioning

confidence: 99%

Superior Thermoelectric Performance of SiGe Nanowires Epitaxially Integrated into Thermal Micro‐Harvesters

Gordillo

Sierra

Gadea

et al. 2023

Small

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of trillions of delocalized sensors will require the development of robust micropower sources. [1] While primary batteries are nowadays the preferred solution, the current scenario cannot be extended much longer, as the exponentially growing number of connected devices require too complex logistics, both for their periodic replacement and disposal of such batteries. In this context, energy harvesting combined with small energy buffers (rechargeable batteries or capacitors) represents a more sustainable alternative to single-use batteries. [2][3][4] In particular, thermoelectric harvesters are solid-state devices capable of directly converting waste heat into electricity, with efficiencies in the range of 1%-10%. Among their main advantages, an absence of movable parts, high reliability, and the recently explored possibility of miniaturization make them promising candidates to power the IoT revolution. [5][6][7] The efficiency of a ThermoElectric (TE) system is measured using the so-called zT Figure of Merit, a dimensionless parameter that relates the main TE properties of the materials as zT = S 2 σT/κ, where S is the Seebeck coefficient, σ electrical conductivity, and κ its thermal conductivity. Although the thermoelectric effect is known since the 19 th century, currently, best-performing TE materials are still based on scarce, expensive, environmentally Semiconductor nanowires have demonstrated fascinating properties with applications in a wide range of fields, including energy and information technologies. Particularly, increasing attention has focused on SiGe nanowires for applications in a thermoelectric generation. In this work, a bottom-up vapour-liquidsolid chemical vapour Deposition methodology is employed to integrate heavily boron-doped SiGe nanowires on thermoelectric generators. Thermoelectrical properties -, i.e., electrical and thermal conductivities and Seebeck coefficient -of grown nanowires are fully characterized at temperatures ranging from 300 to 600 K, allowing the complete determination of the Figure-of-merit, zT, with obtained values of 0.4 at 600 K for optimally doped nanowires. A correlation between doping level, thermoelectric performance, and elemental distribution is established employing advanced elemental mapping (synchrotron-based nano-X-ray fluorescence). Moreover, the operation of p-doped SiGe NWs integrated into silicon micromachined thermoelectrical generators is shown over standalone and series-and parallel-connected arrays. Maximum open circuit voltage of 13.8 mV and power output as high as 15.6 µW cm −2 are reached in series and parallel configurations, respectively, operating upon thermal gradients generated with hot sources at 200 °C and air flows of 1.5 m s −1 . These results pave the way for direct application of SiGe nanowire-based micro-thermoelectric generators in the field of the Internet of Things.

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Note: Improvement of the 3ω thermal conductivity measurement technique for its application at the nanoscale

Cited by 13 publications

References 20 publications

Thermal Conductivity Reduction in Rough Silicon Nanomembranes

Thermal Conductivity Reduction in Rough Silicon Nanomembranes

On-chip all-silicon thermoelectric device

Superior Thermoelectric Performance of SiGe Nanowires Epitaxially Integrated into Thermal Micro‐Harvesters

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