X-ray photoelectron spectroscopy study on Fe and Co catalysts during the first stages of ethanol chemical vapor deposition for single-walled carbon nanotube growth

Abstract

Optimized chemical vapor deposition processes for single-walled carbon nanotube (SWCNT) can lead to the growth of dense, vertically aligned, mm-long forests of SWCNTs. Precise control of the growth process is however still difficult, mainly because of poor understanding of the interplay between catalyst, substrate and reaction gas. In this paper we use x-ray photoelectron spectroscopy (XPS) to study the interplay between Fe or Co catalysts, SiO2 and Al2O3 substrates and ethanol during the first stages of SWCNT forest growth. With XPS we observe that ethanol oxidizes Fe catalysts at carbon nanotube (CNT) growth temperatures, which leads to reduced carbon nanotube growth. Ethanol needs to be decomposed by a hot filament or other technique to create a reducing atmosphere and reactive carbon species in order to grow vertically aligned single-walled carbon nanotubes from Fe catalysts. Furthermore, we show that Al2O3, unlike SiO2, plays an active role in CNT growth using ethanol CVD. From our study we conclude that metallic Fe on Al2O3 is the most optimal catalyst/substrate combination for high-yield SWCNT forest growth, using hot filament CVD with ethanol as the carbon containing gas.

The density factor in the synthesis of carbon nanotube forest by injection chemical vapor deposition

“…20 The intricate physics and chemistry involved in the catalyst particles evolution in the CVD process has since been extensively investigated. [21][22][23][24][25] Control of catalyst predeposition CVD as demonstrated by the synthesis of A4-sized single-walled CNT forests 2 and the continuous production of multi-walled CNT forests 26 presents potential technologies toward industrial-scale productions.…”

Fundamental properties of high-quality carbon nanofoam: from low to high density

“…In particular, XPS reveals important bonding information about carbons with nanoscale units such as carbon nanotubes [31], diamond-like carbon films [32], nanostructured carbon films [33], tetrahedral amorphous carbon films [34], amorphous carbon [35], nanoporous carbon [36], activated carbon [37], or carbon black [38]. In addition, XPS is important for the analysis of chemical structure [39], in particular, for the investigation of the sp 2 /sp 3 hybridization ratio [35].…”

Influence of activated charcoal on the structural and morphological characteristics of ceramic based on silicon oxycarbide (SiOC): A promising approach to obtain a new electrochemical sensing platform

“…The majority of structures revealed a concentric morphology, suggesting the formation of multiwall carbon nanotubes (MWCNT). The growth of carbon nanotubes (CNT) in systems without using of metallic catalyst, such as Fe, Co and Ni [49,50], has been reported [51,52]. Takagi et al [53] proposed that the catalyst is responsible to generate a template for the formation of a cap that is adequate to growth of the nanostructures.…”