Floating catalyst CVD synthesis of single walled carbon nanotubes from ethylene for high performance transparent electrodes

Abstract

We have developed the floating catalyst chemical vapor deposition (FCCVD) synthesis of single walled carbon nanotubes (SWCNTs) using C2H4 hydrocarbon as a carbon source and iron nanoparticles as the catalyst in an environmentally friendly and economical process. For the first time, ethylene was used as the only carbon source in FCCVD with N2 as the main carrier gas. No sulphur and less than 15% H2 in a N2 carrier gas were used. By varying the ferrocene concentration, the diameter of the SWCNTs was tuned in the range of 1.3-1.5 nm with the optimized control of ferrocene concentration. The process produced SWCNTs with an average length of 13 μm and with a low level of bundling, that is a high proportion (28%) of individual tubes. The electron diffraction (ED) pattern indicated a random chirality distribution of the tubes between armchair and zigzag structures. The ED analysis also revealed that 35-38% of tubes are metallic. As a result of having long SWCNTs with a low level of bundling and a high fraction of metallic tubes, we produced a highly conductive transparent film with a sheet resistance of 51 Ohm per sq. for 90% transmission at 550 nm after HNO3 treatment, this being one of the lowest sheet resistance values reported for SWCNT thin films.

Roles of sulfur in floating-catalyst CVD growth of single-walled carbon nanotubes for transparent conductive film applications

“…Moreover, the Fe SWCNTs were found randomly distributed from zig-zag to armchair edges with the mean chiral angle of 16.06±8.35 o having 61% of semiconducting nanotubes. This result is consistent with the ferrocene (Fe(C H ) ) based Fe SWCNTs using ethylene as a carbon source [63]. Hence, our result demonstrated that in the FC-CVD method, for the similar composition of catalyst particles, choice of the catalyst precursor has no significant effect in tuning the chirality distribution of SWCNTs.…”

“…It includes both through premade catalyst particles and in-situ catalyst synthesis processes. The growth has been observed in Fe, Co, Ni, Co-Ni catalysts from spark discharge generator with C2H4 as a carbon source [11] and from Fe catalyst particles obtained from in-situ decomposition of ferrocene (FeCp2) with C2H4 [63], C2H5OH [48] and CH4 as carbon sources (see Table 5.1). However, it's worth mentioning that in all these systems growth conditions of purely CNTs and graphene-CNTs hybrid material are different and one can get graphene-CNTs hybrid by precisely controlling growth parameters.…”

“…5.22. Gas-phase synthesis of SWCNT-graphene hybrid from a) Fe-spark, C2H4 [11], b) Co-spark, C2H4 [11], d) Fe-FeCp2, C2H4 [63], e) Fe-FeCp2, C2H5OH [48] and f)…”

Fast and Ultraclean Approach for Measuring the Transport Properties of Carbon Nanotubes

“…The hereby presented transistor array method is compatible with various types of FC‐CVD CNTs. To illustrate the compatibility, larger‐diameter FC‐CVD SWCNTs ( d ≈ 1.5 nm), grown with ethylene as the carbon feedstock, have been used . In the literature, the mean diameter of SWCNTs for measuring mobility is 1.5 nm or larger .…”

“…Thicker SWCNTs (mean diameter: 1.5 nm, length: 12.61 ± 4.48 µm) were grown using the FC‐CVD process with ferrocene as the catalyst precursor and ethylene as the carbon feedstock. A detailed description of the SWCNT growth system was published earlier …”