# Scalable Fabrication of Highly Organized, Horizontally Aligned Sub‐5 nm Silicon Nanowires via Chemical Vapor Etching

## TL;DR

Researchers developed a scalable method to create highly organized sub-5 nm silicon nanowires that can be used for highly sensitive chemical and bio-sensing.

## Contribution

A scalable, catalyst-free chemical vapor etching process to fabricate highly ordered sub-5 nm silicon nanowires with unprecedented control and sensitivity.

## Key findings

- Sub-5 nm silicon nanowires were fabricated using a chemical vapor etching process.
- The nanowires enable single-molecule detection with high sensitivity.
- The structures show quantum confinement and enhanced optical response.

## Abstract

Herein, the scalable fabrication of hierarchical silicon structures featuring high‐density, horizontally super‐aligned sub‐5 nm silicon nanowires (SiNWs), is reported. These unprecedented, highly organized silicon architectures with tunable sizes and densities are fabricated using straightforward micro‐patterned SiO2/Si templates followed by a chemical vaporetching process. In time‐resolved structural analysis, it is revealed that rapid, aggressive etching is crucial for creating an inhomogeneous spatial distribution of vapor etchants, inducing surface defects acting as preferential sites for localized anisotropic silicon etching along <111> direction. The efficacy of this unique structure is demonstrated as a single‐molecule detectable surface‐enhanced Raman scattering sensor, incorporating sub‐10 nm silver plasmonic nanoparticles. Its distinct structural features—marked by quantum‐confined dimensions, ultrahigh surface area, dual‐scale roughness, and exceptional uniformity—enable significant enhancement of optical response and detection sensitivity down to 10−11 
m. These highly controlled sub‐5 nm SiNW architecture can broaden the applications of quantum nanowires in chemical and bio‐sensing and other emerging technologies.

An unprecedented silicon nano/micro‐hierarchical architecture featuring sub‐5 nm quantum silicon nanowires (SiNWs) is achieved via a single‐step, catalyst‐free chemical vapor etching process. Using a simple micro‐patterning technique, a scalable strategy for fabricating highly ordered SiNWs/micro‐pit arrays is developed. In the results, their exceptional potential is highlighted as an efficient template for single‐molecule detection.© 2025 WILEY‐VCH GmbH