Annealing-induced morphological evolution of iron nanocatalysts for carbon nanotube growth

Abstract

The synthesis of iron nanocatalysts on silicon substrates via the Electron Beam Physical Vapor Deposition method has garnered significant attention due to its catalytic uses. The influence of annealing temperature (500°C, 550°C, and 600°C) on the structural and morphological characteristics of Fe nanocatalysts and their use in the growth of carbon nanotubes via Chemical Vapor Deposition is investigated in this study. Atomic Force Microscopy and Scanning Electron Microscopy measurements reveal that an increase in the annealing temperature reduces the average nanocluster size, and annealing at 600°C yields nanoclusters with an average size of approximately 30 nm; hence, they are more effective as catalysts. Raman spectroscopy proved that carbon nanotube growth was only observed on the 600°C-annealed substrate, and it exhibits a high ID/IG ratio (<1), indicating high crystallinity and low defect concentration. The absence of Radial Breathing Mode peaks represents additional evidence that the synthesized carbon nanotubes are multi-walled. These findings indicate that nanocluster size and distribution must be controlled with high accuracy using Electron Beam Physical Vapor Deposition and thermal treatment in order to maximize Fe nanocatalysts for carbon nanotubes growth