Site-specific Forest-assembly of Single-Wall Carbon Nanotubes on Electron-beam Patterned SiOx/Si Substrates

TL;DR

This study demonstrates a method to create site-specific assemblies of single-wall carbon nanotubes on electron-beam patterned SiOx/Si substrates by leveraging electron-induced surface modifications and metal-assisted functionalization.

Contribution

It introduces a novel approach combining electron-beam patterning and Fe3+ assisted self-assembly to precisely position SWNTs on substrates, enabling advanced nanostructure fabrication.

Findings

Electron-beam irradiation creates oxygen vacancies and dangling bonds on SiOx surfaces.

Irradiated regions absorb more Fe3+ ions, facilitating selective metal functionalization.

Patterned SWNT assemblies are achieved and confirmed by resonance Raman spectroscopy.

Abstract

Based on electron-beam direct writing on the SiOx/Si substrates, favorable absorption sites for ferric cations (Fe3+ ions) were created on the surface oxide layer. This allowed Fe3+-assisted self-assembled arrays of single-wall carbon nanotube (SWNT) probes to be produced. Auger investigation indicated that the incident energetic electrons depleted oxygen, creating more dangling bonds around Si atoms at the surface of the SiOx layer. This resulted in a distinct difference in the friction forces from unexposed regions as measured by lateral force microscopy (LFM). Atomic force microscopy (AFM) affirmed that the irradiated domains absorbed considerably more Fe3+ ions upon immersion into pH 2.2 aqueous FeCl3 solution. This rendered a greater yield of FeO(OH)/FeOCl precipitates, primarily FeO(OH), upon subsequent washing with lightly basic dimethylformamide (DMF) solution. Such selective metalfunctionalization established the basis for the subsequent patterned forest-assembly of SWNTs as demonstrated by resonance Raman spectroscopy.