Silicon nanowires with controlled sidewall profile and roughness fabricated by thin-film dewetting and metal-assisted chemical etching

Azeredo, Bruno; Sadhu, Jyothi; Ma, Jan; Jacobs, Kyle E.; Kim, J; Lee, K; Eraker, J. H.; Li, X; Sinha, Sanjiv; Fang, Nicholas X.; Ferreira, Placid M.; Hsu, Kuo Chin

doi:10.1088/0957-4484/24/22/225305

Cited by 67 publications

(55 citation statements)

References 36 publications

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“…Most of the heat is carried by MFPs less than 1 micron, with some heat being carried by longer MFPs in the partially specular case. Additionally, most actual nanowires have surface roughness higher than 0.1 nm4142, and in this case long MFP phonons contribute only a small amount to heat conduction. Due to the relatively large diameter of the nanowire, changes to the phonon dispersion for thermal phonons due to phonon confinement are unlikely43.…”

Section: Discussionmentioning

confidence: 99%

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

Zhang

Hua

Ding

et al. 2015

Sci Rep

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Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron.

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Section: Discussionmentioning

confidence: 99%

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

Zhang

Hua

Ding

et al. 2015

Sci Rep

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“…5. Figure 5(a) is a photograph of Si NWs fabricated on a 2-inch substrate showing the anti-reflective nature of the NWs [79]. Figure 5(b) is a high-resolution transmission electron microscopy (HRTEM) image of a MAC-etched Si NW with an electron diffraction pattern inset showing the single crystalline nature of the Si NW, which can now be grown with a high degree of uniformity in length and sidewall morphology over large-area wafers [59].…”

Section: Bottom-up Vs Top-down Nw Fabricationmentioning

confidence: 99%

Metal-assisted chemical etching of silicon and the behavior of nanoscale silicon materials as Li-ion battery anodes

2015

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This review outlines the developments and recent progress in metal-assisted chemical etching of silicon, summarizing a variety of fundamental and innovative processes and etching methods that form a wide range of nanoscale silicon structures. The use of silicon as an anode for Li-ion batteries is also reviewed, where factors such as film thickness, doping, alloying, and their response to reversible lithiation processes are summarized and discussed with respect to battery cell performance. Recent advances in improving the performance of silicon-based anodes in Li-ion batteries are also discussed. The use of a variety of nanostructured silicon structures formed by many different methods as Li-ion battery anodes is outlined, focusing in particular on the influence of mass loading, core-shell structure, conductive additives, and other parameters. The influence of porosity, dopant type, and doping level on the electrochemical response and cell performance of the silicon anodes are detailed based on recent findings. Perspectives on the future of silicon and related materials, and their compositional and structural modifications for energy storage via several electrochemical mechanisms, are also provided.

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“…Metal-assisted chemical etching (MACE) is one alternative directional wet etching method for semiconductors. [ 25 ] A large portion of MACE research focuses on understanding defect generation, namely pores that are created in the substrate, via fundamental studies. In the case of patterning silicon, it has been reported to produce high aspectratio (>100) features [ 23 ] with sub-10 nm resolution [ 24 ] and tunable sidewall profi le with taper ranging from 0° to 13°.…”

Section: Introductionmentioning

confidence: 99%

Direct Imprinting of Porous Silicon via Metal‐Assisted Chemical Etching

Azeredo

Lin

Avagyan

et al. 2016

Adv Funct Materials

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2929wileyonlinelibrary.com drug delivery, [ 8,9 ] and biosensing [ 10,11 ] are derived from such integration. However, micro-and nanopatterning of PS has remained a challenge due to the inability of standard microfabrication processes (e.g., photolithography, wet and dry etching) to effectively pattern PS. [ 12 ] In this paper, we demonstrate a low-cost, low-stress, ambient and high-throughput chemical nanoimprint approach to patterning smooth 3D curvilinear PS surfaces in a single imprinting operation. As a demonstration of this process, sinusoidal and parabolic surfaces with potential uses as diffraction gratings and concentrators are fabricated to demonstrate potential onchip micro-optical components.Traditional approaches to patterning Si do not extend to PS because of the permeability and reactivity of the latter. During photolithography and micromachining, photoresist, developers, and etchants infi ltrate the pores, leading to contamination of the substrate, poor sidewall control and over-etching and, in general, poor fi delity of pattern transfer. [ 12,13 ] A simple route to bypass these issues is to perform lithography prior to anodization. The patterned photoresist fi lm is used as a mask during the anodization step leading to 2D embedded PS patterns with micron-scale resolution. [ 14 ] Cost-effective wet-etching processes such as KOH cannot selectively etch PS since multi ple crystal facets are exposed. Recipes for dry etching methods must be specifi cally tailored to a particular pore morphology of the PS being etched and high-aspect ratio features are seldom reported. [ 12 ] To circumvent these issues, micro-contact printing (MP), [ 15 ] dry-removal soft-lithography (DWSL), [ 16 ] and direct imprinting of PS (DIPS) [ 17,18 ] methods have been developed to pattern PS. The MP method uses a stamp that blocks diffusion of reactants during anodization of the silicon surface. As a result, it offers few degrees of freedom for 3D patterning and, thus, is limited to fabricating shallow corrugated patterns. The latter two patterning methods exploit the controlled fracturing or collapsing of the brittle porous material to selectively strip or compress PS. While DWSL is restricted to 2D patterning with microscale resolution, DIPS can generate 3D features with sub-100 nm resolution. DIPS relies on the compaction of PS leading to permanent deformation of the substrate and, thus, modifying spatially the porous morphology and the optical Conventional lithographical techniques used for bulk semiconductors produce dramatically poor results when used for micro and mesoporous materials such as porous silicon (PS). In this work, for the fi rst time, a high-throughput, single-step, direct imprinting process for PS not involving plastic deformation or high-temperature processing is reported. Based on the underlying mechanism of metal-assisted chemical etching (MACE), this process uses a pre-patterned polymer stamp coated with a noble metal catalyst to etch PS immersed in an HF-oxidizer mixture. The process not only overcome...

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Silicon nanowires with controlled sidewall profile and roughness fabricated by thin-film dewetting and metal-assisted chemical etching

Cited by 67 publications

References 36 publications

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

Metal-assisted chemical etching of silicon and the behavior of nanoscale silicon materials as Li-ion battery anodes

Direct Imprinting of Porous Silicon via Metal‐Assisted Chemical Etching

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