Miniaturized planar Si-nanowire micro-thermoelectric generator using exuded thermal field for power generation

Abstract

For harvesting energy from waste heat, the power generation densities and fabrication costs of thermoelectric generators (TEGs) are considered more important than their conversion efficiency because waste heat energy is essentially obtained free of charge. In this study, we propose a miniaturized planar Si-nanowire micro-thermoelectric generator (SiNW-μTEG) architecture, which could be simply fabricated using the complementary metal–oxide–semiconductor–compatible process. Compared with the conventional nanowire μTEGs, this SiNW-μTEG features the use of an exuded thermal field for power generation. Thus, there is no need to etch away the substrate to form suspended SiNWs, which leads to a low fabrication cost and well-protected SiNWs. We experimentally demonstrate that the power generation density of the SiNW-μTEGs was enhanced by four orders of magnitude when the SiNWs were shortened from 280 to 8 μm. Furthermore, we reduced the parasitic thermal resistance, which becomes significant in the shortened SiNW-μTEGs, by optimizing the fabrication process of AlN films as a thermally conductive layer. As a result, the power generation density of the SiNW-μTEGs was enhanced by an order of magnitude for reactive sputtering as compared to non-reactive sputtering process. A power density of 27.9 nW/cm2 has been achieved. By measuring the thermal conductivities of the two AlN films, we found that the reduction in the parasitic thermal resistance was caused by an increase in the thermal conductivity of the AlN film and a decrease in the thermal boundary resistance.

Phonon and heat transport control using pillar-based phononic crystals

“…Moreover, PnCs can reduce the thermal conductivity [5,6]. Thus, PnCs can enhance the thermoelectric efficiency of poor thermoelectric materials, such as silicon [7–9], and be used in energy harvesting applications [10,11] along with other nanostructured [11–14] and hierarchical [15,16] materials.…”

Si and SiGe Nanowire for Micro-Thermoelectric Generator: A Review of the Current State of the Art

“…and low electrical/thermal contact resistance (Noroozi et al, 2017b). NiSi has also been a good choice for electrodes for those µTEG heated from the outside (Zhan et al, 2018). AlN films are adopted as thermally conductive layers for TEG with 300/500 nm thickness and the respective thermal conductivity is 4 and 11 W m −1 K −1 .…”

“…Generally, µTEGs with this structure are easy to design, and they have large output power and high conversion efficiency. However, the defects come from the difficult and expensive fabrication process, like the deepetching in the top-down methods, or the well-controlled NW synthesis and metal electrodes integration in the bottom-up methods (Zhan et al, 2018). The lateral structure µTEG, which is compatible with the CMOS process, is relatively easy to fabricate (Xie et al, 2010;Yu et al, 2012Yu et al, , 2015Noroozi et al, 2017b).…”

“…Moreover, the substrates are etched away to form thermally isolated Si NWs for high efficacy, resulting in a vulnerable structure and expensive fabrication cost. Generally, the high conversion efficiency is essential when the expensive specified heat source is applied, such as RTG, while power generation density is crucial for the heat source which is cheap or free, like waste heat (Zhan et al, 2018).…”

Research on X‐Ray Inspection of Basin Insulators and Wireless Image Sensing Technology

“…Nagy et al investigated the local discharge characteristics of artificial microdefects such as cracks, voids, and delamination generated using precise production control and demonstrated the effect of defects on insulator performance [7]. Zhan et al proposed to first use the cubic background of the weld image to be detected is simulated by curve fitting, and the simulated background image is numerically subtracted from the original weld image to obtain a weld image with a more uniform background grayscale distribution and a higher detail of defect information, and finally, an appropriate threshold is selected to extract and segment the defects in the weld image [8]. The method is effective in extracting relatively obvious defects to a certain extent, but it is not effective in extracting defects of complex shapes.…”