Low-dimensional silicon-based materials have shown a great potential for thermoelectric applications due to their enhanced figure of merit ZT and high technology compatibility. However, their implementation in real devices remains highly challenging due to the associated large contact resistances (thermal and electrical). Herein we demonstrate ultralow contact resistance silicon nanowires epitaxially grown on scalable devices with enhanced ZT. Temperature dependent figure of merit was fully determined for monolithically integrated individual silicon nanowires achieving a maximum value of ZT = 0.2 at 620 K. Sidewise, this work accounts for the first time nearly zero thermal and electrical contact resistances in monolithically integrated bottom-up nanowires.

Semiconductor nanowires have demonstrated fascinating properties with application in a wide range of fields including energy and information technologies. In particular, increasing attention has been focused on Si and SiGe...

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.

Self‐powered sensors running on small differences of temperature are considered promising candidates to cover the increasing demand of sustainable and maintenance‐free wireless sensor networks for the Internet of Things (IoT). Under this context, a cost‐effective and self‐powered hydrogen thermoelectric sensor is presented here as a proof of concept for battery‐less IoT nodes. The device is based on low‐density paper‐like fabrics made of functionalized thermoelectric silicon nanotubes able to harvest energy from the heat released by exothermic reactions, such as the hydrogen catalytic oxidation. This gives an accurate value of the reacting gas concentration without any external power requirement. Experimental results confirm that this self‐powered sensor can autonomously measure concentrations as low as 250 ppm of hydrogen in air while generating power densities up to 0.5 μW cm−2 for 3% H2 at room temperature that can be eventually used to store or send the reading. Due to the universality of the concept, this new class of devices will positively contribute toward the development of other advanced self‐powered sensor nodes in the advent of the Internet of things to be used in different safety scenarios.

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.