Morphology dependence of optical reflectance properties for a high-density array of silicon nanowires

Yamaguchi, Toshihisa; Shimizu, Tomohiro; Morosawa, Y.; Takase, Koichi; Chen, Tzu-Ling; Lu, Shin-Ming; Chien, H. C.; Shingubara, Shoso

doi:10.7567/jjap.53.06jf10

Cited by 12 publications

(9 citation statements)

References 31 publications

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“…The diameter and the height of the nanowires would affect the agglomeration behaviors, as reported by Yamaguchi et al 43 and Auliano et al, 13 thus affecting the geometric parameters of V-grooves. It is noteworthy that the nanowires tended to be embraced as nanowire diameter decreases and nanowire height increases, as shown in Figure 2.…”

Section: Methodsmentioning

confidence: 84%

Fast Capillary Wicking on Hierarchical Copper Nanowired Surfaces with Interconnected V-Grooves: Implications for Thermal Management

Jiang

Chen

Zhang

et al. 2021

ACS Appl. Nano Mater.

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Evaporation and boiling heat transfer on micro/nanostructured surfaces with superior wicking capability is an efficient cooling approach for high heat flux removal. The enhancement of the wicking capability has been identified as a key mechanism to enhance heat transfer efficiency and prevent thermal crisis. However, the capillary wicking capability is limited by the trade-off between the capillary pressure and the viscous resistance on the length scale of the structure feature. Here, we report a rapid capillary wicking capability on hierarchical nanowired surfaces with interconnected V-grooves, whose wicking coefficient reaches 6.54 mm/s0.5. This is attributed to the highly uniform copper nanowires which provide prominent capillary pressure while the interconnected V-grooves provide liquid film transport channels to reduce the viscous resistance. We experimentally investigated the effect of nanowire spacing, V-groove fraction, and V-groove depth on the wicking coefficient for various liquids with surface tension to viscosity ratios from 6 to 81. Larger fractions and depths of such V-grooves lead to higher wicking coefficients. Moreover, the wicking coefficient is increased as the surface tension to viscosity ratio of the liquid increases. This work offers guidelines for designing and optimizing hierarchical structures to enable ultrafast liquid film wicking, thus highlighting the thermal management potential.

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Section: Methodsmentioning

confidence: 84%

Fast Capillary Wicking on Hierarchical Copper Nanowired Surfaces with Interconnected V-Grooves: Implications for Thermal Management

Jiang

Chen

Zhang

et al. 2021

ACS Appl. Nano Mater.

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“…This can be explained considering that the wicking could depend on two contrasting forces such as the capillary force and viscous force of the flow. 32 By looking at the topography of the NW surface from the SEM top view in Figure 2a−c, as the height increases, the bundling effect becomes more prominent (as reported also by Yamaguchi et al (2014) 39 ), thus increasing the spacing between the NWs bundles and reducing the flow resistance. The shortest NW NW-A has the lowest power law coefficient np (as shown in Table 1).…”

Section: ■ Results and Discussionmentioning

confidence: 59%

Can Wicking Control Droplet Cooling?

Auliano

Fernandino

et al. 2019

Langmuir

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Wicking, defined as absorption and passive spreading of liquid into a porous medium, has been identified as a key mechanism to enhance the heat transfer and prevent the thermal crisis. Reducing the evaporation time and increasing the Leidenfrost point (LFP) are important for an efficient and safe design of thermal management applications, such as electronics, nuclear, and aeronautics industry. Here, we report the effect of the wicking of superhydrophilic nanowires (NWs) on the droplet vaporization from low temperatures to temperatures above the Leidenfrost transition. By tuning the wicking capability of the surface, we show that the most wickable NW results in the fastest evaporation time (reduction of 82, 76, and 68% compared with a bare surface at, respectively, 51, 69, and 92 °C) and in one of the highest shifts of the LFP of a water droplet (5 μL) in the literature (about 260 °C).

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“…The each sample with the nanostructure showed homogenous dark color at the surface, and reflectance spectra measured at different part on the sample indicated almost similar. However, the reflectance of the nanocone arrays is still higher than the reflectance of previously reported Si nanowire arrays in visible range [21,22]. The optimization of size and shape of the nanocone arrays is necessarily to realize further low reflectance.…”

Section: Resultsmentioning

confidence: 77%

Fabrication of nanocone arrays by two step metal assisted chemical etching method

Shimizu

Tanaka

Tada

et al. 2016

Microelectronic Engineering

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This work develops a novel method for preparing a moth eye structure, which has a sub-wavelength periodical Si nanocone structure on Si (100) substrate, using two-step metal assisted chemical etching (MACE). The 1 st and 2 nd MACE were respectively performed with the intention to form perpendicular Si nanowire arrays on a Si substrate and sharpening the Si nanowire arrays. We found the inhomogeneous absorption and aggregation of Au particles used as a catalyst for 2 nd MACE was important to obtain the nanocone shape. The obtained Si nanocone arrays showed superior anti-reflecting properties especially in wavelength below 600 nm compared to the Si nanowire arrays. A possible mechanism involved in the formation of the nanocone structure by the 2-step MACE is discussed in this paper.

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Morphology dependence of optical reflectance properties for a high-density array of silicon nanowires

Cited by 12 publications

References 31 publications

Fast Capillary Wicking on Hierarchical Copper Nanowired Surfaces with Interconnected V-Grooves: Implications for Thermal Management

Fast Capillary Wicking on Hierarchical Copper Nanowired Surfaces with Interconnected V-Grooves: Implications for Thermal Management

Can Wicking Control Droplet Cooling?

Fabrication of nanocone arrays by two step metal assisted chemical etching method

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