Growth of a single freestanding multiwall carbon nanotube on each nanonickel dot

TLDR

Using this method, devices that require freestanding vertical carbon nanotubes—such as scanning probe microscopes and field‑emission displays—can be fabricated. A thin‑film nickel grid on silicon was patterned by microlithography, and plasma‑enhanced hot‑filament CVD with acetylene as the carbon source and ammonia as catalyst/dilution gas grew the nanotubes. Patterned growth of single freestanding carbon nanotubes on submicron nickel dots was achieved by PE‑HF‑CVD, producing hollow tubes with ~150 nm bases, 0.1–5 µm heights, sharp tips, tunable dimensions via dot size and growth time, and compatibility with silicon integrated‑circuit processing.

Abstract

Patterned growth of freestanding carbon nanotube(s) on submicron nickel dot(s) on silicon has been achieved by plasma-enhanced-hot-filament-chemical-vapor deposition (PE-HF-CVD). A thin film nickel grid was fabricated on a silicon wafer by standard microlithographic techniques, and the PE-HF-CVD was done using acetylene (C2H2) gas as the carbon source and ammonia (NH3) as a catalyst and dilution gas. Well separated, single carbon nanotubes were observed to grow on the grid. The structures had rounded base diameters of approximately 150 nm, heights ranging from 0.1 to 5 μm, and sharp pointed tips. Transmission electron microscopy cross-sectional image clearly showed that the structures are indeed hollow nanotubes. The diameter and height depend on the nickel dot size and growth time, respectively. This nanotube growth process is compatible with silicon integrated circuit processing. Using this method, devices requiring freestanding vertical carbon nanotube(s) such as scanning probe microscopy, field emission flat panel displays, etc. can be fabricated without difficulty.