Epitaxial Graphene Growth on SiC Wafers (original) (raw)
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Physica E: Low-dimensional Systems and Nanostructures, 2016
The epitaxial growth of graphene by the sublimation of Si-terminated silicon carbide (SiC) is studied inside a graphite enclosure in a radio-frequency furnace by comparing different in-situ processes involving hydrogen etching and growth conditions. For the growth under vacuum, even with the surface preparation of hydrogen etching, the morphology of the synthesized graphene is found full of voids and defects in the form of a multilayer graphene film. For the growth under Ar, the hydrogen etching plays a vital role to improve the graphene quality in terms of the surface roughness, the number of graphene layers and the domain size. For the graphene samples grown with the proposed protocol, the original combination of micro-probe Raman spectroscopy and simultaneous optical transmission and reflection measurements reveals a detailed spatially resolved image of the graphene domains with monolayer domainsize of ~5 x 5 µm on about 2/3 of the total sample surface. The magnetotransport data yield charge-carrier mobilities up to 2900 cm 2 /Vs as found for high quality graphene on the Si-face of SiC. The observed magnetoquantum oscillations in the magnetoresistance confirm the expected behavior of single-layer graphene.
Selective epitaxial growth of graphene on SiC
Applied Physics Letters, 2008
We present an innovative method of selective epitaxial growth of few layers graphene (FLG) on a pre-patterned SiC substrate. The methods involves, successively, the sputtering of a thin AlN layer on top of a mono-crystalline SiC substrate and, then, patterning it with e-beam lithography (EBL) and wet etching. The sublimation of few atomic layers of Si from the SiC substrate occurs only through the selectively etched AlN layer. The presence of the Raman G-band at ~1582 cm-1 in the AlN-free areas is used to validate the concept, it gives absolute evidence of the selective FLG growth.
Analysis of the Formation Conditions for Large Area Epitaxial Graphene on SiC Substrates
Materials Science Forum, 2010
We are aiming at understanding the graphene formation mechanism on different SiC polytypes (6H, 4H and 3C) and orientations with the ultimate goal to fabricate large area graphene (up to 2 inch) with controlled number of monolayers and spatial uniformity. To reach the objectives we are using high-temperature atmospheric pressure sublimation process in an inductively heated furnace. The epitaxial graphene is characterized by ARPES, LEEM and Raman spectroscopy. Theoretical studies are employed to get better insight of graphene patterns and stability. Reproducible results of single layer graphene on the Si-face of 6H and 4H-SiC polytypes have been attained. It is demonstrated that thickness uniformity of graphene is very sensitive to the substrate miscut.
Growth kinetics of epitaxial graphene on SiC substrates
Physical Review B, 2010
Optical absorption and Raman scattering studies of epitaxial graphene structures obtained by annealing of carbon terminated face of 4H-SiC͑000-1͒ on-axis substrates using standard chemical-vapor deposition reactor are presented. Two series of samples grown at different argon pressures in the reactor and different annealing times were studied. Optical absorption and Raman scattering were used to determine the number of graphene layers formed on the substrate surface. The observed dependence of the number of graphene layers formed on annealing time and argon pressure strongly indicates that the growth kinetics of graphene is limited by Si evaporation and two-dimensional Si diffusion.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2010
Up to two layers of epitaxial graphene have been grown on the Si-face of two-inch SiC wafers exhibiting room-temperature Hall mobilities up to 1800 cm 2 V -1 s -1 , measured from ungated, large, 160 μm x 200 μm Hall bars, and up to 4000 cm 2 V -1 s -1 , from top-gated, small, 1 μm x 1.5 μm Hall bars. The growth process involved a combination of a cleaning step of the SiC in a Si-containing gas, followed by an annealing step in Argon for epitaxial graphene formation.
Epitaxial growth and characterization of graphene on free-standing polycrystalline 3C-SiC
Journal of Applied Physics, 2011
The epitaxial growth of graphene on inexpensive, commercially available, free-standing polycrystalline 3 C-SiC has been achieved by solid state graphitization in ultrahigh vacuum. The structural and electronic properties of such epitaxial graphene (EG) have been explored by Raman spectroscopy, scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). The Raman results show that the grown EG is compressively stressed. The quality of such EG is similar to that on single-crystalline hexagonal SiC substrates. The STM measurements show that the EG grown on polycrystalline SiC presents atomically smooth surfaces across large regions of the underlying SiC substrate with some nanometer-scale features, such as one-dimensional (1-D) ridges, 1-D grain boundaries, and graphene in different stacking sequences. The STS measurements reveal the electronic properties of such EG at an atomic scale. Our approach suggests a more inexpensive way to grow high quality and large scale graphene and represents a promising step toward commercialization of graphene-based electronics.
Raman spectroscopy of epitaxial graphene on a SiC substrate
Physical Review B, 2008
The fabrication of epitaxial graphene (EG) on SiC substrate by annealing has attracted a lot of interest as it may speed up the application of graphene for future electronic devices. The interaction of EG and the SiC substrate is critical to its electronic and physical properties. In this work, Raman spectroscopy was used to study the structure of EG and its interaction with SiC substrate. All the Raman bands of EG blue shift from that of bulk graphite and graphene made by micromechanical cleavage, which was attributed to the compressive strain induced by the substrate. A model containing 13 × 13 honeycomb lattice cells of graphene on carbon nanomesh was constructed to explain the origin of strain. The lattice mismatch between graphene layer and substrate causes the compressive stress of 2.27 GPa on graphene.
CVD growth of SiC on sapphire substrate and graphene formation from the epitaxial SiC
Journal of Crystal Growth, 2013
6H-SiC epi-layer was grown on c-plane sapphire by chemical vapor deposition (CVD) and epitaxial graphene was grown on the SiC film using the thermal decomposition method. A thin ($ 300 nm) AlN was employed as a buffer layer since a direct growth on sapphire did not produce SiC. Raman spectroscopy, x-ray diffraction (XRD), and atomic force microscopy (AFM) confirmed the growth of high quality 6H-SiC on the AlN/sapphire at 1450 1C. The effect of AlN growth method/condition (HVPE and MBE) on the quality of final SiC film and epitaxial graphene was explored. Raman and XRD 2y-scan did not show any significant difference between the SiC films grown on HVPE-AlN and MBE-AlN. A sharper XRD rocking curve was observed on the SiC/HVPE-AlN but a smoother SiC was grown on the MBE-AlN. Graphitization of the SiC/AlN/sapphire was done at 1300-1400 1C under Ultra High Vacuum (UHV). The SiC on MBE-AlN survived at high temperatures (up to 1400 1C) without cracking and graphene was grown on it. However, the SiC on HVPE-AlN cracked and peeled off at 1300 1C resulting in no formation of graphene. The signatures of graphene were clearly observed by Raman spectroscopy with the 2D-peak to G-peak intensity (I 2D /I G) of approximately 2, the D-peak to G-peak intensity (I D /I G) of 0.4, and the 2D-peak width of 55 cm À 1 .
Epitaxial graphene formation on 3C-SiC/Si thin films
Journal of Physics D: Applied Physics, 2014
By forming a thin 3C-SiC film on Si substrates and by annealing it at ∼1500 K in vacuo, few-layer graphene is formed epitaxially on Si substrates. In this graphene-on-silicon (GOS) technology, graphene grows at least on three major low-index Si surfaces: (1 1 1), (1 0 0) and (1 1 0), which allows tuning of structural and electronic properties of epitaxial graphene by simply controlling the crystallographic orientation of the surface. A typical example can be found in the two types of graphene formed on 3C-SiC(1 1 1) surfaces; the one on 3C-SiC(1 1 1)/Si(1 1 1) shows a Bernal stacking with an interfacial buffer layer, while the one on 3C-SiC(1 1 1)/Si(1 1 0) shows a non-Bernal stacking without an interfacial buffer layer. Inserting an AlN interlayer between Si and 3C-SiC significantly contributes to improvement of the GOS quality. Moreover, thanks to the sealing effect of the AlN layer against Si out-diffusion, we can apply chemomechanical polishing of SiC surface to reduce the surface roughness, which can further accentuate the effect of H 2 annealing of the surface. As a result, a D to G band intensity ratio as low as 0.4 is obtained.