Carbon:nickel (C: Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD).
TEM lamella preparation of the C: Ni templates after pre-treatment and CNT growth was done by lift-out using a Zeiss Crossbeam NVision 40 system.
To protect the sensitive surface, a carbon cap layer was deposited beginning with electron beam assisted and subsequently followed by Ga focused ion beam (FIB) assisted precursor decomposition.
SWCNT diameter distribution and the presence of multi-walled CNTs were analysed by SEM and Raman spectroscopy.
It is demonstrated that SWCNT diameters strongly depend on the NCT type applied for CVD synthesis.
NCT type I comprises predefined catalyst NPs, while for NCT type II the catalyst NPs are formed formed catalyst particles.
Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were applied to characterize the NCTs before and after the CVD process and to determine the size distribution of the catalyst particles.
SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I.
About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm.
The NPs appear to be well-aligned with a mean NP center to center distance of (4.3 ± 0.3) nm.
Lattice fringes were resolved for approximately 40% of 27 NPs analyzed in detail (Fig. Fast Fourier Transform (FFT) analysis gave lattice spacings grouped into (a) 0.22 nm to 0.24 nm and (b) 0.20 to 0.21 nm.
In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution from 0.80 to 1.40 nm covering 88% of all SWCNTs are obtained from NCT type II.