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| 2. |
- Beshkova, Milena, 1975-, et al.
(author)
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Structural Properties of 3C-SiC Grown by Sublimation Epitaxy
- 2009
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In: ECSCRM2009,2009. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 181-184
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Conference paper (peer-reviewed)abstract
- The present paper deals with morphological and structural investigation of 3C-SiC layers grown by sublimation epitaxy on on axis 6H-SiC(0001) at source temperature 2000 °C, under vacuum conditions (<10-5 mbar) and different temperature gradients in the range of 5-8 °C/mm. The layer grown at a temperature gradient 6 °C/mm has the largest average domain size of 0.4 mm2 assessed by optical microscope in transmission mode. The rocking curve full width at half maximum (FWHM) of (111) reflection is 43 arcsec which suggests good crystalline quality. The AFM image of the same layer shows steps with height 0.25 nm and 0.75 nm which are characteristic of a stacking fault free 3C-SiC surface and c-axis repeat height, respectively.
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| 3. |
- Darakchieva, Vanya, et al.
(author)
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Large-area microfocal spectroscopic ellipsometry mapping of thickness and electronic properties of epitaxial graphene on Si- and C-face of 3C-SiC(111)
- 2013
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:21, s. 213116-
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Journal article (peer-reviewed)abstract
- Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene grown by high-temperature sublimation on 3C-SiC (111) substrates is reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C-SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at ∼4.5 eV and the free-charge carrier scattering time, on the other are established. It is shown that the interface structure on the Si- and C-polarity of the 3C-SiC(111) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.
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| 4. |
- Eriksson, Jens, et al.
(author)
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Thickness uniformity and electron doping in epitaxial graphene on SiC
- 2013
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In: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 740-742, s. 153-156
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Journal article (peer-reviewed)abstract
- Large variations have been observed in the thickness uniformity and carrier concentration of epitaxial graphene grown on SiC by sublimation for samples grown under identical conditions and on nominally on-axis hexagonal SiC (0001) substrates. We have previously shown that these issues are both related to the morphology of the graphene-SiC surface after sublimation growth. Here we present a study on how the substrate polytype, substrate surface morphology and surface restructuring during sublimation growth affect the uniformity and carrier concentration in epitaxial graphene on SiC. These issues were investigated employing surface morphology mapping by atomic force microscopy coupled with local surface potential mapping using scanning Kelvin probe microscopy.
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| 5. |
- Jokubavicius, Valdas, et al.
(author)
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Macrodefects in cubic silicon carbide crystals
- 2010
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In: Materials Science Forum, Vols. 645-648. - : Transtec Publications; 1999. ; , s. 375-378
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Conference paper (peer-reviewed)abstract
- Different sublimation growth conditions of 3C-SiC approaching a bulk process have been investigated with the focus on appearance of macrodefects. The growth rate of 3C-SiC crystals grown on 6H-SiC varied from 380 to 460 mu m/h with the thickness of the crystals from 190 to 230 mu m, respectively. The formation of macrodefects with void character was revealed at the early stage of 3C-SiC crystal growth. The highest concentration of macrodefects appears in the vicinity of the domain in samples grown under high temperature gradient: and fastest temperature ramp up. The formation of macrodefects was related to carbon deficiency which appear due to high Si/C ratio which is used to enable formation of the 3C-SiC polytype.
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| 6. |
- Mammadov, Samir, et al.
(author)
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Polarization doping of graphene on silicon carbide
- 2014
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In: Current Opinion in Chemical Engineering. - : IOP Publishing: Hybrid Open Access. - 2211-3398. ; 1:3, s. 035003-
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Journal article (peer-reviewed)abstract
- The doping of quasi-freestanding graphene (QFG) on H-terminated, Si-face 6H-, 4H-, and 3C-SiC is studied by angle-resolved photoelectron spectroscopy close to the Dirac point. Using semi-insulating as well as n-type doped substrates we shed light on the contributions to the charge carrier density in QFG caused by (i) the spontaneous polarization of the substrate, and (ii) the band alignment between the substrate and the graphene layer. In this way we provide quantitative support for the previously suggested model of polarization doping of graphene on SiC (Ristein et al 2012 Phys. Rev. Lett. 108 246104).
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| 7. |
- Scajev, P., et al.
(author)
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On applicability of time-resolved optical techniques for characterization of differently grown 3C-SiC crystals and heterostructures
- 2012
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In: HETEROSIC and WASMPE 2011. - : Trans Tech Publications Inc.. ; , s. 159-163
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Conference paper (peer-reviewed)abstract
- We applied a number of time-resolved optical techniques for investigation of optical and photoelectrical properties of cubic SiC grown by different technologies on different substrates. The excess carriers were injected by a short laser pulse and their dynamics was monitored by free-carrier absorption, light-induced transient grating, and photoluminescence techniques in a wide excitation range. Combining an optical and electrical probe beam delay, we found that free carrier lifetimes in differently grown layers vary from few ns up to 20 mu s. Temperature dependences of carrier diffusivity and lifetime revealed a pronounced carrier trapping in thin sublimation grown layers. In free-standing layers and thick sublimation layers, the ambipolar mobility was found the highest (120 cm(2)/Vs at room temperature). A linear correlation between the room-temperature band edge emission and carrier lifetime in differently grown layers was attributed to defect density, strongly dependent on the used growth conditions.
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| 8. |
- Vasiliauskas, Remigijus, et al.
(author)
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Cubic SiC formation on the C-face of 6H-SiC (0001) substrates
- 2012
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 348:1, s. 91-96
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Journal article (peer-reviewed)abstract
- Nucleation and subsequent growth of cubic SiC (111) on Si- and C-faces of nominally on-axis 6H-SiC substrates was investigated. More uniform nuclei and twin boundary distribution was observed when 3C-SiC was grown on the C-face. This was attributed to a lower critical supersaturation ratio. A new type of defects which appear as pits in the C-face 3C-SiC layers related to homoepitaxial 6H-SiC spiral growth was found and described. The evaluation of the growth driving force for both polar faces showed that the homoepitaxial 6H-SiC spirals were not overgrown on the C-face due to low maximum supersaturation ratio. The XRD ω-rocking characterization shows a better structural quality of the 3C-SiC was grown on the Si-face, however on the C-face the uniformity over the whole sample was higher. Unintentional doping by N (~1016 cm-3) was slightly higher on the C-face while Al doping was higher (~1014 cm-3) on the Si-face of the grown material, similarly to the doping of hexagonal SiC polytypes.
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| 9. |
- Vasiliauskas, Remigijus, et al.
(author)
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Effect of initial substrate conditions on growth of cubic silicon carbide
- 2011
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In: Journal of Crystal Growth. - : Elsevier Science B.V., Amsterdam.. - 0022-0248 .- 1873-5002. ; 324:1, s. 7-14
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Journal article (peer-reviewed)abstract
- In order to analyze the epitaxial growth of cubic silicon carbide by sublimation epitaxy on different substrates, four different 6H-SiC substrate preparations were used: (i) as-received, (ii) re-polished, (iii) annealed and covered by silicon layer and (iv) with (1 1 1) 3C-SiC buffer layer. Almost 100% coverage and low twin density was achieved when grown on the buffer layer. The XRD and TEM characterizations show better material quality when the layer is grown directly on 6H-SiC substrates. Background doping evaluated by LTPL is in the range of 10(16) cm(-3) for N and 10(16) cm(-3) for Al in all grown layers.
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| 10. |
- Vasiliauskas, Remigijus, et al.
(author)
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Impact of extended defects on Hall and magnetoresistivity effects in cubic silicon carbide
- 2012
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In: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 45:22, s. 225102-
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Journal article (peer-reviewed)abstract
- From magnetoresistivity effect measurements the carrier mobility at room- temperature is 200 cm2/Vs in heteroepitaxially grown 3C-SiC on 6H-SiC by sublimation epitaxy. The main scattering mechanisms are found to be scattering by neutral impurities at low temperature and by phonons at higher temperature. The carrier concentration is in the range of 1016 cm-3, which corresponds to the concentration of residual doping by nitrogen acquired from photoluminescence measurements. Using magnetoresistance and Hall mobility data we have created a simple model which quantifies the volume of the samples influenced by extended defects. A higher doping near extended defects is either not present in the samples or might be screened by the electrostatic field created by these defects.
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