Noncatalytic synthesis of carbon nanotubes, graphene and graphite on SiC
Introduction
Remarkable potential of CNTs [1] for applications including electronics, electrical energy storage, composites, gas sensors, and field emitters [2] led to development of many methods for their synthesis. However, the yield, purity, controlled synthesis and integration of CNTs on wafers for device applications remain challenging. It is known that both graphene [3] and CNTs can be produced by high temperature decomposition of SiC by the reaction [4]:with most attention directed towards graphene during the past year or two [5]. Kusunoki et al. [6], [7], [8] observed formation of CNTs growing normally to the carbon terminated C-face of hexagonal SiC with primarily zigzag chirality [9] and graphite growth on the Si terminated (0 0 0 1) Si-face. In contrary, Derycke et al. [10] reported single-wall carbon nanotubes (SWCNTs) with 1.2–1.6 nm diameter on the Si-face growing parallel to the crystal surface. Nagano et al. claimed CNT formation on both carbon and silicon faces of hexagonal 6H–SiC [11] and cubic 3C–SiC [12] after HF etching, with tubes growing normal to the surface. However, transmission electron microscope (TEM) images of “nanotubes” show anisotropic graphite lamellas instead [13]. While TEM evidence of small-diameter CNTs has been presented [6], [7], [8], only a single Raman spectrum containing two weak peaks which were assigned to RBM modes of nanotubes has been published [14], raising a question about the content of nanotubes in these films. Our recent work on vacuum decomposition of β-SiC whiskers showed well ordered graphene layers but no nanotube formation [15]. The most recent study [16] suggested the growth of CNTs at 1400–1700 °C on both C- and Si-faces of 4H SiC, but with different growth rates, following the reaction:No satisfactory explanation of differences in the carbon growth on Si- and C-terminated surfaces of SiC has been offered so far. The mechanism of nanotube formation on SiC is not clear and results suffer from poor reproducibility.
Here, we report on a systematic experimental study of vacuum decomposition of 6H SiC single crystals that elucidates the nanotube formation mechanisms and conditions for the growth of nanotubes.
Section snippets
Experimental
6H-SiC single crystal wafers, 0.37 mm in thickness with epi-ready polished (0 0 0 1) Si-face and optical polished C-face on axis without any dopants (resistivity > 105 Ω cm) were obtained from Intrinsic Semiconductor Corporation (Fig. 1). The as-received samples were heated at six temperatures 1400, 1500, 1600, 1700, 1800, and 1900 °C for 4 h in a Solar Atmospheres (US) vacuum (10−6 and 10−4 Torr) furnace with an electric resistance carbon heater. The heating rate was 5 °C min−1. Arkema multi-wall
Results and discussion
Raman microspectroscopy analysis (Fig. 2a) showed that the decomposition rate of SiC on the C-face at 10−6 Torr is higher than that on the Si-face. G-band of graphite is clearly seen on the C-face after annealing at 1400 °C and carbon completely shields SiC bands in the samples annealed at 1600 °C and above (Fig. 2b). On the Si-face, G-band only becomes pronounced at 1600 °C, but formation of graphene layers can be observed on the Si-surface at 1400 °C by monitoring second order peaks of graphite
Summary and conclusions
Our work shows that the structure (graphene, graphite or CNT) and thickness of carbon coating on SiC can be controlled by changing the silica structure, its thickness or removal rate; Si evaporation rate, temperature of the substrate, composition of the environment or by producing a diffusion barrier for Si (graphene formation or pre-deposited coating). As a result, either graphene (or relatively thick graphite) films or CNT carpets can be produced on C- and Si-faces of SiC (Fig. 11). This
Acknowledgments
We thank Prof. J.E. Fischer, Dr. M. Nikiforov (University of Pennsylvania), and Mr. M. Kurtoglu for helpful discussions; Prof. C. Li (both at Drexel University) for providing access to the thermobalance, Solar Atmospheres for the vacuum furnace, Dr. E. Flahaut (Toulouse, France), Arkema and Superior Graphite for providing carbon samples, and Instrinsic for SiC wafers. Materials Characterization Facility of the A.J. Drexel Nanotechnology Institute provided access to microscopes and spectrometers
References (41)
- et al.
Selective synthesis of zigzag-type aligned carbon nanotubes on SiC wafers
Chem Phys Lett
(2002) - et al.
Etching of hexagonal SiC surfaces in chlorine-containing gas media at ambient pressure
Surf Sci
(2006) - et al.
STM and XPS studies of early stages of carbon nanotube growth by surface decomposition of 6H-SiC under various oxygen pressures
Diam Relat Mater
(2007) - et al.
Elimination of D-band in Raman spectra of double-wall carbon nanotubes by oxidation
Chem Phys Lett
(2005) - et al.
Optical properties of single-wall carbon nanotubes
Synthetic Met
(1999) - et al.
Physics of carbon nanotubes
Carbon
(1995) - et al.
Scanning–tunneling-microscopy of the formation of carbon nanocaps on SiC )
Chem Phys Lett
(2006) - et al.
Carbon nanotubes – the route toward applications
Science
(2002) - et al.
Controlling the electronic structure of bilayer graphene
Science
(2006)
Carbide derived carbon
The rise of graphene
Nature Mater
Formation of self-aligned carbon nanotube films by surface decomposition of silicon carbide
Phil Mag Lett
A formation mechanism of carbon nanotube films on SiC
Appl Phys Lett
Epitaxial carbon nanotube film self-organized by sublimation decomposition of silicon carbide
Appl Phys Lett
Catalyst-free growth of ordered single-walled carbon nanotube networks
Nano Lett
Effects of surface oxides of SiC on carbon nanotube formation by surface decomposition
Jpn J Appl Phys
Preparation of silicon-on-insulator substrate on large free-standing carbon nanotube film formation by surface decomposition of SiC film
Jpn J Appl Phys
Production of highly oriented carbon nanotube films by surface decomposition of silicon carbide polycrystalline films
Jpn J Appl Phys Part 2
Characterization of small-diameter carbon nanotubes and carbon nanocaps on SiC (0 0 0 1) using Raman spectroscopy
Jpn J Appl Phys Part I
Cited by (128)
Reduction of graphene oxide on polyethylene terephthalate surface by using transmission femtosecond laser
2023, Applied Surface ScienceTribology of SiC ceramics under lubrication: Features, developments, and perspectives
2022, Current Opinion in Solid State and Materials ScienceA review of tribological properties for boron carbide ceramics
2021, Progress in Materials ScienceProgress in tribological research of SiC ceramics in unlubricated sliding-A review
2020, Materials and DesignGraphene nanoparticles: The super material of future
2020, Materials Today: Proceedings