Thermoelectric Properties of Silicon Nanowire Array and Spin-on Glass Composites Fabricated with CMOS-compatible Techniques

ABSTRACTSilicon nanowires (NWs) are promising thermoelectric materials as they offer large reductions in thermal conductivity over bulk Si without a significant decrease in the Seebeck coefficient or electrical conductivity. In this work, interference lithography was used to pattern a square lattice photoresist template over 2 cm x 2 cm Si substrates. The resulting vertical Si NW arrays were 1 μm tall with a packing density of ~15%, and the diameter of the Si NWs were 80 - 90 nm. The Si NW arrays were then embedded in spin-on glass (SOG) to form a dense composite material with a measured thermal conductivity of 1.45 W/m-K at 300 K. Devices were fabricated for cross-plane Seebeck coefficient measurements and the Si NW/SOG composite was found to have a Seebeck coefficient of roughly -284 μV/K, which is similar to bulk Si with the same doping. We also report a combined power generation of 29.3 μW from both the Si NW array and Si substrate with a temperature difference of 56 K and 50 μm x 50 μm device area.

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Simultaneous Measurements of Thermal Conductivity and Seebeck Coefficients of Roughened Nanowire Arrays

MRS Proceedings ◽

10.1557/opl.2012.1371 ◽

2012 ◽

Vol 1456 ◽

Author(s):

J. S. Sadhu ◽

T. Hongxiang ◽

J. Ma ◽

J. Kim ◽

S. Sinha

Keyword(s):

Thermal Conductivity ◽

Seebeck Coefficient ◽

Silicon Nanowires ◽

Nanowire Array ◽

Temperature Drop ◽

Nanowire Arrays ◽

Measured Temperature ◽

Si Substrates ◽

Seebeck Coefficients ◽

Simultaneous Measurements

ABSTRACTWe report simultaneous measurements of thermal conductivity and Seebeck coefficient on array-scale silicon nanowires fabricated by metal assisted chemical etching. The measurements are conducted on the solid and the mesoporous nanowire arrays (NWAs) obtained from etching 1 ohm-cm and 0.002 ohm-cm Si substrates respectively. We demonstrate control on sidewall morphology and doping of the arrays that have an aspect ratio up to 20 and 30 % areal coverage. We employ differential frequency-domain measurements, separately on the array and the corresponding substrate to obtain the temperature drop and Seebeck voltage contribution of the nanowire array. The technique is validated by measurements on bulk silicon across the resistivity 0.002-1 ohm-cm. The Seebeck measurements reveal quenching of the phonon drag in the nanowires in comparison to the bulk in the measured temperature range of 300 K- 500 K. The Seebeck coefficient shows a ~18 % decrease in the solid NWAs and ~22 % increase in the mesoporous NWAs at room temperature. The thermal conductivity is close to Casimir limit for the solid wires while it drops to ~2.5 W/mK in the mesoporous nanowires.

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A review and analysis on growth and optical absorption properties of silicon nanowire array for photovoltaic applications

Modern Physics Letters B ◽

10.1142/s0217984915300070 ◽

2015 ◽

Vol 29 (30) ◽

pp. 1530007 ◽

Cited By ~ 2

Author(s):

Ritu Sharma ◽

Lalit Kumar Dusad

Keyword(s):

Solar Cells ◽

Silicon Nanowires ◽

Silicon Nanowire ◽

Nanowire Array ◽

Major Research ◽

Absorption Properties ◽

Silicon Nanowire Array ◽

Photovoltaic Applications ◽

Research Findings ◽

Experimental Approaches

In this paper, optical absorptions in silicon nanowires (SiNWs) arrays obtained from theoretical studies and experimental approaches have been reviewed. A brief description on the different growth techniques for SiNW arrays reported so far is presented. Comparative analysis based on major research findings has been done and the advantages of SiNW-based solar cells over thin film solar cells are presented. Furthermore, future aspects of the use of SiNWs for photovoltaic applications are discussed.

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A Novel Top-Down Fabrication Process for Vertically-Stacked Silicon-Nanowire Array

Applied Sciences ◽

10.3390/app10031146 ◽

2020 ◽

Vol 10 (3) ◽

pp. 1146 ◽

Cited By ~ 3

Author(s):

Kangil Kim ◽

Jae Keun Lee ◽

Seung Ju Han ◽

Sangmin Lee

Keyword(s):

Silicon Nanowires ◽

Silicon Nanowire ◽

Nanowire Array ◽

Nanowire Arrays ◽

Fabrication Method ◽

Top Down ◽

Silicon Nanowire Arrays ◽

Sensing Applications ◽

Silicon Nanowire Array ◽

Cross Sectional Dimension

Silicon nanowires are widely used for sensing applications due to their outstanding mechanical, electrical, and optical properties. However, one of the major challenges involves introducing silicon-nanowire arrays to a specific layout location with reproducible and controllable dimensions. Indeed, for integration with microscale structures and circuits, a monolithic wafer-level process based on a top-down silicon-nanowire array fabrication method is essential. For sensors in various electromechanical and photoelectric applications, the need for silicon nanowires (as a functional building block) is increasing, and thus monolithic integration is highly required. In this paper, a novel top-down method for fabricating vertically-stacked silicon-nanowire arrays is presented. This method enables the fabrication of lateral silicon-nanowire arrays in a vertical direction, as well as the fabrication of an increased number of silicon nanowires on a finite dimension. The proposed fabrication method uses a number of processes: photolithography, deep reactive-ion etching, and wet oxidation. In applying the proposed method, a vertically-aligned silicon-nanowire array, in which a single layer consists of three vertical layers with 20 silicon nanowires, is fabricated and analyzed. The diamond-shaped cross-sectional dimension of a single silicon nanowire is approximately 300 nm in width and 20 μm in length. The developed method is expected to result in highly-sensitive, reproducible, and low-cost silicon-nanowire sensors for various biomedical applications.

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A Systematic Study of Metal-assisted Chemical Etching Parameters for Well-Ordered Silicon Nanowire Array Fabrication

MRS Proceedings ◽

10.1557/opl.2012.41 ◽

2012 ◽

Vol 1408 ◽

Author(s):

Arif S. Alagoz ◽

Tansel Karabacak

Keyword(s):

Silicon Nanowires ◽

Chemical Etching ◽

Crystalline Silicon ◽

Silicon Nanowire ◽

Etching Rate ◽

Nanowire Array ◽

Lithium Ion ◽

Nanowire Diameter ◽

Silicon Nanowire Array ◽

Metal Assisted Chemical Etching

ABSTRACTMetal-assisted chemical etching is a simple and low-cost silicon nanowire fabrication method which allows control of nanowire diameter, length, shape and orientation. In this work, we fabricated well-ordered silicon nanowire array by patterning gold thin film by nanosphere lithography and etching single crystalline silicon wafer by metal-assisted chemical etching technique. We investigated relation between etched solution concentration and nanowire morphology, wafer crystal orientation, etching rate. This well-ordered silicon nanowires arrays have the potential applications in many fields but especially next generation energy related applications from solar cells to lithium-ion batteries.

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Reusable Surface-Enhanced Raman Spectroscopy Substrates Made of Silicon Nanowire Array Coated with Silver Nanoparticles Fabricated by Metal-Assisted Chemical Etching and Photonic Reduction

Nanomaterials ◽

10.3390/nano9111531 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1531 ◽

Cited By ~ 2

Author(s):

Shi Bai ◽

Yongjun Du ◽

Chunyan Wang ◽

Jian Wu ◽

Koji Sugioka

Keyword(s):

Silver Nanoparticles ◽

Chemical Etching ◽

Silicon Nanowire ◽

Nanowire Array ◽

Surface Enhanced Raman Spectroscopy ◽

Sers Substrate ◽

Silicon Nanowire Array ◽

Surface Enhanced ◽

Surface Enhanced Raman ◽

Metal Assisted Chemical Etching

Surface-enhanced Raman spectroscopy (SERS) has advanced over the last four decades and has become an attractive tool for highly sensitive analysis in fields such as medicine and environmental monitoring. Recently, there has been an urgent demand for reusable and long-lived SERS substrates as a means of reducing the costs associated with this technique To this end, we fabricated a SERS substrate comprising a silicon nanowire array coated with silver nanoparticles, using metal-assisted chemical etching followed by photonic reduction. The morphology and growth mechanism of the SERS substrate were carefully examined and the performance of the fabricated SERS substrate was tested using rhodamine 6G and dopamine hydrochloride. The data show that this new substrate provides an enhancement factor of nearly 1 × 108. This work demonstrates that a silicon nanowire array coated with silver nanoparticles is sensitive and sufficiently robust to allow repeated reuse. These results suggest that this newly developed technique could allow SERS to be used in many commercial applications.

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