Tuning the Thermoelectric Properties of Boron‐Doped Silicon Nanowires Integrated into a Micro‐Harvester

Gordillo, Jose Manuel Sojo; Estrada‐Wiese, Denise; Duque‐Sierra, Carolina; Gadea‐Díez, Gerard; Salleras, M.; Fonseca, L.; Morata, Álex; Tarancón, Albert

doi:10.1002/admt.202101715

Cited by 10 publications

(14 citation statements)

References 68 publications

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“…The result is consistent with studies relating the degree of surface roughness with an enhanced phonon scattering. [41,42] The value also matches 𝜅 estimations performed using fully electrical measurements [26] in the same kind of wires and is also consistent with the theoretical predictions for rough NWs [43][44][45] employing again a fully diffuse model (specularity parameter p = 0) and estimated surface-to-volume ratios in the order of 0.015 nm −1 .…”

Section: Thermal Conductivity Determinationsupporting

confidence: 86%

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Local Heat Dissipation and Elasticity of Suspended Silicon Nanowires Revealed by Dual Scanning Electron and Thermal Microscopies

Sojo‐Gordillo,

Gadea‐Diez,

Renahy

et al. 2023

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A novel combined setup, with a scanning thermal microscope (SThM) embedded in a scanning electron microscope (SEM), is used to characterize a suspended silicon rough nanowire (NW), which is epitaxially clamped at both sides and therefore monolithically integrated in a microfabricated device. The rough nature of the NW surface, which prohibits vacuum‐SThM due to loose contact for heat dissipation, is circumvented by decorating the NW with periodic platinum dots. Reproducible approaches over these dots, enabled by the live feedback image provided by the SEM, yield a strong improvement in thermal contact resistance and a higher accuracy in its estimation. The results—thermal resistance at the tip‐sample contact of 188±3.7K µW−1 and thermal conductivity of the NW of 13.7±1.6W m−1 K−1—are obtained by performing a series of approach curves on the dots. Noteworthy, the technique allows measuring elastic properties at the same time—the moment of inertia of the NW is found to be (6.1±1.0) × 10−30m4—which permits to correlate the respective effects of the rough shell on heat dissipation and on the NW stiffness. The work highlights the capabilities of the dual SThM/SEM instrument, in particular the interest of systematic approach curves with well‐positioned and monitored tip motion.

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Section: Thermal Conductivity Determinationsupporting

confidence: 86%

“…The NW studied in this work is expitaxially integrated at both ends in the same way as those NWs reported in prior works, [ 21,25,26 ] as illustrated in Figure a. The NW has a length of 17.3 µm, an average diameter of 57.2 nm, and it is suspended at a distance of 2.5 µm over the substrate (see Figure , Supporting Information).…”

Section: Resultsmentioning

confidence: 97%

Local Heat Dissipation and Elasticity of Suspended Silicon Nanowires Revealed by Dual Scanning Electron and Thermal Microscopies

Sojo‐Gordillo,

Gadea‐Diez,

Renahy

et al. 2023

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“…[ 50 ] Contrary, the observed reduction is likely related to the suppression of the phonon drag contribution driven by the nanostructuration which doubtlessly affects the thermal conductivity. This effect is not expected to be as important as in the case of pure silicon [ 51–53 ] since germanium alloying already induces an important phonon suppression enhancement. However, it might still contribute to this reduction at the low‐temperature range.…”

Section: Resultsmentioning

confidence: 99%

“…Because at the scales of the studied NW (Φ NW ≈ 87 nm) no alteration of the electronic structure is expected -typically happening for Φ NW < 10 nm -size effects can be discarded as responsible for the observed reduced S. [50] Contrary, the observed reduction is likely related to the suppression of the phonon drag contribution driven by the nanostructuration which doubtlessly affects the thermal conductivity. This effect is not expected to be as important as in the case of pure silicon [51][52][53] since germanium alloying already induces an important phonon suppression enhancement. However, it might still contribute to this reduction at the low-temperature range.…”

Section: Thermoelectrical Propertiesmentioning

confidence: 97%

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

Gordillo

Sierra

Gadea

et al. 2023

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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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“…[135][136][137] High concentrations of phosphorous (n-type) and boron (p-type) dopants have been frequently used to increase phonon scattering for lower thermal conductivity and increase charge carriers for higher PFs. [41,[138][139][140] Liu et al [17] found that increasing phosphorus doping in a GaP/Si composite 2 stoichiometric percentage to 5 stoichiometric percentage increased electrical conductivity by 30% and decreased thermal conductivity by 40%. The phosphorus increased the carrier concentration and [120] Copyright 2017, Elsevier.…”

Section: Siliconmentioning

confidence: 99%

Recent Advances in the Nanomaterials, Design, Fabrication Approaches of Thermoelectric Nanogenerators for Various Applications

Kim

Kumar

Annamalai

et al. 2022

Adv Materials Inter

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power-dense, owing to their tuneable nanostructures. Hence, smaller TENGs are better suited for small form-factor applications like wearable electronics, internet of things (IoT) devices, and self-powered sensors. However, the higher complexity and cost of TENGs than TEGs inhibit their widespread adoption. This review appraises the latest advances in TENG materials, design, and fabrication in optimizing the performance of TENGs, making TENGs more viable for real-world applications. More precisely, this work examines how nanostructure engineering, nanomaterial compositing, and post-synthesis treatment approaches have enhanced the TE properties of common and promising TE materials, including tellurides, selenides, metal oxides, metal alloys, silicon, carbon nanomaterials, and organic compounds. Given that the TE material is a key component in TENGs, this review highlights how to optimize other vital parameters, including the TENG configuration, contact interface, form factor, heat sink use, and folded shape for specific applications. Lastly, critical attributes of TENGs used in wearable electronics, sensors, implantable electronics, solar energy conversion, and waste heat recovery are analyzed.

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Tuning the Thermoelectric Properties of Boron‐Doped Silicon Nanowires Integrated into a Micro‐Harvester

Abstract: The data that support the findings of this study are openly available in Thermoelectric properties of p-doped rough silicon nanowires at https://doi.org/10.5281/zenodo.5806683, reference number 1194.

Cited by 10 publications

References 68 publications

Local Heat Dissipation and Elasticity of Suspended Silicon Nanowires Revealed by Dual Scanning Electron and Thermal Microscopies

Local Heat Dissipation and Elasticity of Suspended Silicon Nanowires Revealed by Dual Scanning Electron and Thermal Microscopies

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

Recent Advances in the Nanomaterials, Design, Fabrication Approaches of Thermoelectric Nanogenerators for Various Applications

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