The influence of H&lt;sub&gt;2&lt;/sub&gt; and NH&lt;sub&gt;3&lt;/sub&gt; on catalyst nanoparticle formation and carbon nanotube growth

Pezone, R.; Vollebregt, S.; Sarro, Pasqualina M; Unnikrishnan, S.

doi:10.1016/j.carbon.2020.07.045

The influence of H₂ and NH₃ on catalyst nanoparticle formation and carbon nanotube growth

Title

The influence of H₂ and NH₃ on catalyst nanoparticle formation and carbon nanotube growth

Author

Pezone, R. (TU Delft Electronic Components, Technology and Materials; TNO)
Vollebregt, S. (TU Delft Electronic Components, Technology and Materials)
Sarro, Pasqualina M (TU Delft Electronic Components, Technology and Materials)
Unnikrishnan, S. (TNO)

Date

2020

Abstract

Control of the morphology of carbon nanotubes (CNT) is fundamental for many applications. It is known that the catalyst distributions influence the vertical alignment and the height of the CNT. In this work we investigate the influence of the pre-anneal time and reductant gases, specifically NH₃ and H₂ as well as combinations thereof, on the nanoparticle (NP) formation and CNT growth. The gases H_2, NH₃ show opposite roles during the dewetting of 1 nm Fe catalyst layer. The H₂ favours uniform NP distributions (mean diameter of 15 nm) and the NH₃ forms large clusters. Playing with double annealing steps H₂- NH₃ we obtained NP with larger mean diameters μ = 20 nm. We observed a mismatch between the diameters of the NP directly after annealing and the CNT after growth, due to a reshaping of the catalyst NP before the CNT nucleation. Furthermore, we found that longer annealing times decrease the CNT forest height and the H₂ exposure during the annealing improves the height and the alignment of the CNT.