| 201. |
- Virojanadara, Chariya, et al.
(författare)
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Homogeneous large-area graphene layer growth on 6H-SiC(0001)
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:24, s. 245403-
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous large-area graphene monolayers were successfully prepared ex situ on 6H-SiC(0001). The samples have been studied systematically and the results are compared with those from a sample cut from the same wafer and prepared by in situ heating. The formation of smaller graphene flakes was found on the in situ prepared sample, which is in line with earlier observations. Distinctly different results are observed from the ex situ graphene layers of different thicknesses, which are proposed as a guideline for determining graphene growth. Recorded C 1s spectra consisted of three components: bulk SiC, graphene (G), and interface (I), the latter being a 6 root 3 layer. Extracted intensity ratios of G/I were found to give a good estimate of the thickness of graphene. Differences are also revealed in micro low energy electron diffraction images and electron reflectivity curves. The diffraction patterns were distinctly different from a monolayer thickness up to three layers. At a larger thickness only the graphitelike spot was visible. The electron reflectivity curve showed a nice oscillation behavior with kinetic energy and as a function of the number of graphene layers. The graphene sheets prepared were found to be very inert and the interface between the substrate and the layer(s) was found to be quite abrupt. No free Si could be detected in or on the graphene layers or at the interface.
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| 202. |
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| 203. |
- Virojanadara, Chariya, et al.
(författare)
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Substrate orientation : A way towards higher quality monolayer graphene growth on 6H-SiC(0001)
- 2009
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 603:15, s. L87-L90
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Tidskriftsartikel (refereegranskat)abstract
- The influence of substrate orientation on the morphology of graphene growth on 6H-SiC(0 0 0 1) was investigated using low-energy electron and scanning tunneling microscopy (LEEM and STM). Large area monolayer graphene was successfully furnace-grown on these substrates. Larger terrace widths and smaller step heights were obtained on substrates with a smaller mis-orientation from on-axis (0.03 degrees) than on those with a larger (0.25 degrees). Two different types of a carbon atom networks, honeycomb and three-for-six arrangement, were atomically resolved in the graphene monolayer. These findings are of relevance for various potential applications based on graphene-SiC structures.
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| 204. |
- Vouroutzis, N, et al.
(författare)
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Behavior of micropipes during growth in 4H-SiC
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 395-398
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Konferensbidrag (refereegranskat)abstract
- The disturbance of the growth steps in SiC epitaxy and the formation of stacking faults (SFs) in the vicinity of a micropipe were studied by Atomic Force Microscopy and Transmission Electron Microscopy. Shallow trenches are observed in front of the micropipes due to the distortion of the growth steps towards of the micropipe. The trenches are related with extended (1 (1) over bar 00) type SFs bounded by 1/6 < 11 (2) over bar1 > partial dislocations. These results are also supported by synchrotron X-ray topography.
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| 205. |
- Vouroutzis, N, et al.
(författare)
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Characteristics of planar defects in shallow trenches related to the presence of micropipes
- 2003
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Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 277-280
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Konferensbidrag (refereegranskat)abstract
- The similarities of the trenches related with micropipes observed in 4H-SiC layers formed by sublimation epitaxy are compared with the line-shaped pits observed by optical microscopy in the vicinity of closing micropipes in 4H-SiC epilayers grown by the CVD method. The disturbance of the step-flow along the trenches and the related extended defects are discussed.
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| 206. |
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| 207. |
- Wang, Weimin, et al.
(författare)
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Flat-Band Electronic Structure and Interlayer Spacing Influence in Rhombohedral Four-Layer Graphene
- 2018
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:9, s. 5862-5866
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Tidskriftsartikel (refereegranskat)abstract
- The stacking order of multilayer graphene significantly influences its electronic properties. The rhombohedral stacking sequence is predicted to introduce a flat band, which has high density of states and the enhanced Coulomb interaction between charge carriers, thus possibly resulting in superconductivity, fractional quantum Hall effect, and many other exotic phases of matter. In this work, we comprehensively study the effect of the stacking sequence and interlayer spacing on the electronic structure of four-layer graphene, which was grown on a high crystalline quality 3C-SiC(111) crystal. The number of graphene layers and coverage were determined by low energy electron microscopy. First-principles density functional theory calculations show distinctively different band structures for ABAB (Bernal), ABCA (rhombohedral), and ABCB (turbostratic) stacking sequences. By comparing with angle-resolved photoelectron spectroscopy data, we can verify the existence of a rhombohedral stacking sequence and a nearly dispersionless electronic band (flat band) near the Fermi level. Moreover, we find that the momentum width, bandgap, and curvature of the flat-band region can be tuned by the interlayer spacing, which plays an important role in superconductivity and many other exotic phases of matter.
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| 208. |
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| 209. |
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| 210. |
- Wilhelm, Martin, et al.
(författare)
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Photoluminescence topography of fluorescent SiC and its corresponding source crystals
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications Inc.. ; , s. 421-424
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Konferensbidrag (refereegranskat)abstract
- The preparation and application of co-doped polycrystalline SiC as source in sublimation growth of fluorescent layers is a complex topic. Photoluminescence topographies of luminescent 6H-SiC layers and their corresponding source crystals have been studied in order to investigate the dependence of the epitaxial growth on the source material. It is shown that the homogeneity concerning the dopant incorporation and the layer luminescence intensity does not depend on the characteristics of the PVT grown source material. Therefore co-doped polycrystalline SiC is a promising source material in fast sublimation growth of luminescent 6H-SiC.
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