| 1. |
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| 2. |
- Beshkova, Milena, 1975-, et al.
(författare)
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Structural Properties of 3C-SiC Grown by Sublimation Epitaxy
- 2009
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Ingår i: ECSCRM2009,2009. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 181-184
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Konferensbidrag (refereegranskat)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.
(författare)
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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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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 102:21, s. 213116-
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Thickness uniformity and electron doping in epitaxial graphene on SiC
- 2013
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 740-742, s. 153-156
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Macrodefects in cubic silicon carbide crystals
- 2010
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Ingår i: Materials Science Forum, Vols. 645-648. - : Transtec Publications; 1999. ; , s. 375-378
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Konferensbidrag (refereegranskat)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.
(författare)
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Polarization doping of graphene on silicon carbide
- 2014
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Ingår i: Current Opinion in Chemical Engineering. - : IOP Publishing: Hybrid Open Access. - 2211-3398. ; 1:3, s. 035003-
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: HETEROSIC and WASMPE 2011. - : Trans Tech Publications Inc.. ; , s. 159-163
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Konferensbidrag (refereegranskat)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.
(författare)
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Cubic SiC formation on the C-face of 6H-SiC (0001) substrates
- 2012
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 348:1, s. 91-96
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Effect of initial substrate conditions on growth of cubic silicon carbide
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier Science B.V., Amsterdam.. - 0022-0248 .- 1873-5002. ; 324:1, s. 7-14
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Impact of extended defects on Hall and magnetoresistivity effects in cubic silicon carbide
- 2012
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Ingår i: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 45:22, s. 225102-
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Tidskriftsartikel (refereegranskat)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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| 11. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Influence of twin boundary orientation on magnetoresistivity effect in free standing 3C–SiC
- 2012
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 74, s. 203-205
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Tidskriftsartikel (refereegranskat)abstract
- Free standing 3C–SiC (111) samples with differently oriented twin boundaries were prepared using on-axis and slightly off-axis 6H–SiC substrates. The orientation of twin boundaries causes either an enhancement or suppression of the magnetoresistance mobility. The origin of carrier mobility difference is attributed to the specific structure of these defects. The height of the barriers created by twin boundaries was found to be 0.2 eV.
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| 12. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Nucleation Control of Cubic Silicon Carbide on 6H- Substrates
- 2012
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 12:1, s. 197-204
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Tidskriftsartikel (refereegranskat)abstract
- The nucleation of cubic (3C) SiC on on-axis 6H-SiC was investigated in the temperature range 1500–1775 °C by the technique of sublimation epitaxy. We have studied two different cases: (i) the initial homoepitaxial growth of 6H-SiC followed by nucleation of 3C-SiC and (ii) nucleation of homoepitaxial 6H-SiC islands. The supersaturation in the growth cell was calculated using the modeled source to substrate temperature difference. We show that, at low temperature and supersaturation, growth of 6H-SiC commences in spiral growth mode, which prepares the surface for 3C-SiC nucleation. Provided the supersaturation is high enough, the 3C-SiC nucleates as two-dimensional islands on terraces of the homoepitaxial 6H-SiC. Detailed structural study indicates that the 3C-SiC began to grow on defect free surfaces. From the experimental and modeling results, we show that the growth parameter window for 3C-SiC is rather narrow. Deviation from it can result in 6H-SiC growth in spiral or 2D-nucleation mode, which suggests the importance of knowledge of supersaturation.
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| 13. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Polytype Inclusions in Cubic Silicon Carbide
- 2013
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Ingår i: Silicon Carbide and Related Materials 2012. - : Trans Tech Publications. - 9783037856246 ; , s. 335-338
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Konferensbidrag (refereegranskat)abstract
- In this paper, we review our research on 6H-SiC polytype inclusions in 3C-SiC layers, which were grown on nominally on-axis 6H-SiC substrates using sublimation epitaxy. More than 90% coverage by 3C-SiC is typically achieved at growth temperature of 1775 degrees C. The main reason for the polytype inclusions to appear is local supersaturation non-uniformities over the sample surface which appear due to the temperature gradient and spiral growth nature of 6H-SiC. On the 6H-SiC spirals with small steps supersaturation is smaller and 3C-SiC nucleation and growth is diminished. Due to surface free energy and surface diffusion differences, polytype inclusions appear differently when 3C-SiC is grown on the Si- and C-faces. The 6H-SiC inclusions as well as twin boundaries act as neutral scattering centers and lower charge carrier mobility
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| 14. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Polytype transformation and structural characteristics of 3C-SiC on 6H-SiC substrates
- 2014
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 395, s. 109-115
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Tidskriftsartikel (refereegranskat)abstract
- The 3C-SiC (111) was grown on on-axis 6H-SiC substrates in a temperature interval ranging from 1675oC where 3C-SiC nucleated, to 1825oC where coverage of the substrate by 3C-SiC was nearly 100%. The 6H- to 3C-SiC transformation was not abrupt and two different transitions could be observed. The first one occurs before or during 3C-SiC nucleation and consists of 6H-, 3C-, 15R-SiC and other unresolved stacking sequences. The second one appears due to 6H-SiC and 3C-SiC competition during the growth and results in non flat needle-like interface. A proposed model elucidates connection between four-fold twins nucleating at the 6H-/3C-SiC interface and the formation of depressions at the surface of the 3C-SiC layer.
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| 15. |
- Vasiliauskas, Remigijus
(författare)
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Sublimation Growth and Performance of Cubic Silicon Carbide
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Silicon carbide (SiC) is a wide band gap semiconductor satisfying requirements to replace silicon in devices operating at high power and high frequency at high temperature, and in harsh environments. Hexagonal polytypes of SiC, such as 6H-SiC and 4H-SiC are available on the power device markets. However, the cubic SiC (3C-SiC) polytype is still not industrially used, essentially due to the lack of 3CSiC substrates. This is mainly because of a high density of defects appearing in the crystals. Thus, it is critical to understand material growth and defect formation, and learn to control their appearance. Ensuring, that growth methods capable of large scale industrial production can be applied.The aim of this work was to develop operation conditions for fabrication of 3C-SiC crystals via understanding fundamentals of the growth process and to explore structural and electrical properties of the grown material, including its suitability for substrate applications. The physical vapor transport or sublimation process has already shown a capability to produce substantial quantities of large area and high quality hexagonal SiC substrates. In the present study a similar growth principle, but in a different geometry, namely sublimation epitaxy, was applied. Using this method very high growth rates (up to 1 mm/h) can be achieved for hexagonal polytypes while maintaining high material quality. Additionally, the growth process does not require expensive or hazardous materials, thus making the method very attractive for industrial use.When growing 3C-SiC directly on 6H-SiC, the substrate roughness does not have significant influence on the yield and quality of 3C-SiC. This is mostly due to the growth of homoepitaxial 6H-SiC which appears before the 3C-SiC. Structural characterization showed that 3C-SiC grown directly on 6HSiC exhibited the highest quality as compared with other substrate preparation, such as annealing or deposition of a 3C-SiC buffer layer. Thus, further investigation was devoted to the growth of 3C-SiC on 6H-SiC substrates.The parameter window for the growth of 3C-SiC is quite narrow. The temperature interval is from ~1675oC, where the material starts to nucleate, to ~1850oC, where an uncontrolled growth process begins. Si-rich conditions (high Si/C ratio) and high supersaturation are needed in the growth chamber for preferable 3C-SiC nucleation. Deviation from these parameters leads to the growth of homoepitaxial 6HSiC in spiral or 2D island mode along with cubic SiC with high defect density.Nucleation is the most important step in the growth process. The growth on 6H-SiC substrates commences from homoepitaxial 6H-SiC growth in spiral mode, which makes the surface perfect for 3CSiC nucleation. At temperature of ~1675oC the supersaturation is high enough and the 3C-SiC nucleation initiates in two-dimensional islands on the 6H-SiC spiral terraces. Control of the homoepitaxial 6H-SiC growth is a key element in the growth of 3C-SiC.SiC is a polar material having surfaces terminated by either silicon or carbon atoms, called Si- and C-face, respectively. The growth is different on both faces due to the different free surface energies. The lower surface free energy on the C-face causes more uniform nucleation of 3C-SiC and thereafter more uniform twinned domain distribution. Additionally, calculations showed that increase of growth temperature from 1675oC to 1775oC does not change the supersaturation ratio on the C-face due to a much higher surface diffusion length. This results in appearance of pits in the 3C-SiC layer with a 6H-SiC spiral. The pits were not observed on Si-face material as the supersaturation ratio was much higher. Pits formed in the early stages of growth were overgrown more effectively during the later stages.Characterization by transmission electron microscopy showed that transformation from 6H-SiC to 3C-SiC is not abrupt and can appear in two different modes. The first one is forming a few micrometers of polytypic transition zone consisting predominantly of 15R-, 6H- and 3C-SiC. The second one appears due to a competition between 3C-SiC and 6H-SiC resulting in a step-like intermixing zone between these polytypes. Four-fold twins were observed, which resulted in depressions at the surface of 3C-SiC. These defects expand proportionally to the layer thickness, thus drastically reducing usable area of thick layers.Electrical measurements revealed carrier mobility ~200 cm2/Vs at room temperature and the dominant charge carrier scattering is by neutral centers and phonons. The neutral centers originate from extended defects, such as 6H-SiC inclusions, stacking faults and twin boundaries. By growing 3C-SiC on atomically flat and vicinal substrates a preferential orientation of twin boundaries (TBs) was achieved. The mobility was higher in the material with twin boundaries parallel to the current flow, and lower when twin boundaries were perpendicular to the current flow. This was less pronounced at higher temperature as relatively fewer carriers have to overcome barriers created by TBs.Finally, the substrate capability of the 3C-SiC (111) was demonstrated by growth of a monolayer graphene, which was compared with graphene grown on hexagonal SiC poytypes. The quality of the graphene in terms of thickness uniformity and pit appearance was the best when grown on 3C-SiC. The lower quality on hexagonal substrates was attributed to a more difficult process control which is due to the more complex crystal structure.
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| 16. |
- Vasiliauskas, Remigijus, et al.
(författare)
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Sublimation Growth and Structural Characterization of 3C-SiC on Hexagonal and Cubic SiC Seeds
- 2010
-
Ingår i: Materials Science Forum, Vols. 645-648. - : Transtec Publications; 1999. ; , s. 175-178
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Konferensbidrag (refereegranskat)abstract
- Epitaxial growth of cubic silicon carbide on 6H-SiC substrates, and 6H-SiC substrates with (111) 3C-SiC buffer layer, deposited by vapour liquid solid mechanism, was compared. The morphological details of the grown layers were studied by optical microscopy and their microstructure by transmission electron microscopy. The influence of the substrate on the nucleation of 3C-SiC, the initial homoepitaxial 6H-SiC nucleation before 3C-SiC as well as the formation of defects, are discussed.
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| 17. |
- Vasiliauskas, Remigijus, 1982-, et al.
(författare)
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Two-dimensional nucleation of cubic and 6H silicon carbide
- 2009
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Ingår i: ECSCRM2008,2008. - Materials Science Forum Vols. 615-617 : Trans Tech Publications. - 9780878493340 ; , s. 189-192
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Konferensbidrag (refereegranskat)abstract
- The initial stage of heteroepitaxial growth of 3C-SiC and homoepitaxial growth of 6H-SiC on nominal 6H-SiC on-axis substrates has been studied. Before 3C-SiC starts to nucleate, 6H-SiC grows in a step-flow growth mode due to a slight off-orientation of the substrate surface already at about 1500oC. In the 1650-1700oC temperature interval 3C-SiC nucleates as 2D islands. A distance away from the 3C-SiC island 6H-SiC grows in step-flow mechanism. In the vicinity of the 3C-SiC islands the 6H-SiC growth steps start to change direction and even split into two steps with the equal height of 0.5 nm, which is approaching the unit cell size of cubic SiC. When the supersaturation is lower in comparison with the conditions for 3C-SiC growth, there is only formation of 6H-SiC, i.e. homoepitaxial growth. The growth mode of 6H-SiC is dependent on temperature. At the lowest temperature there is spiral growth while at higher temperature 2D nucleation is preferred.
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| 18. |
- Yakimova, Rositsa, et al.
(författare)
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Progress in 3C-SiC growth and novel applications
- 2012
-
Ingår i: Materials Science Forum Vol 711. - : Trans Tech Publications Inc.. ; , s. 3-10
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Konferensbidrag (refereegranskat)abstract
- Recent research efforts in growth of 3C-SiC are reviewed. Sublimation growth is addressed with an emphasis on the enhanced understanding of polytype stability in relation to growth conditions, such as supersaturation and Si/C ratio. It is shown that at low temperature/supersaturation spiral 6H-SiC growth is favored, which prepares the surface for 3C-SiC nucleation. Provided the supersaturation is high enough, 3C-SiC nucleates as two-dimensional islands on terraces of the homoepitaxial 6H-SiC. Effect of different substrate surface preparations is considered. Typical extended defects and their electrical activity is discussed. Finally, possible novel applications are outlined.
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| 19. |
- Yazdi, Gholamreza, 1966-, et al.
(författare)
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Employing discontinuous and continuous growth modes for preparation of AlN nanostructures on SiC substrates
- 2007
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Ingår i: ECSCRM 2006, Newcastle, UK. - : Trans Tech Publications, Switzerland. ; , s. 1031-1034
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Konferensbidrag (refereegranskat)abstract
- In this report we present results on growth and characterization of AlN wires and thinfilms on SiC substrates. We have employed PVT technique in close space geometry for AlNdeposition on SiC off oriented substrates, most of which were prepared to have scratch-free smoothas-grown surface by SiC sublimation epitaxy. By manipulating the surface kinetics we have beenable to determine growth conditions yielding discontinuous or continuous morphologiescorresponding to nanowires and thin films, respectively. A particular feature of the latterexperiments is the fast temperature ramp up at the growth initiation. The AlN surface morphologywas characterized by optical, AFM and XRD tools, which showed good crystal quality independentof the growth mode.
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| 20. |
- Yazdi, Gholamreza, 1966-, et al.
(författare)
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Fabrication of free-standing AlN crystals by controlled microrod growth
- 2008
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 300:5, s. 935-939
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to propose a growth procedure for preparation of crack-free thick aluminum nitride (AlN) layers that can be easily separated from the substrate. The overall process is based on the physical vapor transport method employing a seed and a source material. In this case, the substrate is an epitaxial 4H-SiC layer and the growth of AlN is initiated at etch pits formed during the ramp up time prior to establishing growth temperature. Development of hexagonal pyramids on which arrays of microrods are formed is the core of the growth procedure. Free-standing wafers having 10 mm diameter and about 120 μm thick have been fabricated.
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| 21. |
- Yazdi, Gholamreza, et al.
(författare)
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Growth of large area monolayer graphene on 3C-SiC and a comparison with other SiC polytypes
- 2013
-
Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 57, s. 477-484
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial graphene growth was performed on the Si-terminated face of 4H-, 6H-, and 3C-SiC substrates by silicon sublimation from SiC in argon atmosphere at a temperature of 2000 degrees C. Graphene surface morphology, thickness and band structure have been assessed by using atomic force microscopy, low-energy electron microscopy, and angle-resolved photoemission spectroscopy, respectively. Differences in the morphology of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. The uniformity of silicon sublimation is a decisive factor for obtaining large area homogenous graphene. It is also shown that a lower substrate surface roughness results in more uniform step bunching with a lower distribution of step heights and consequently better quality of the grown graphene. Large homogeneous areas of graphene monolayers (over 50 x 50 mu m(2)) have been grown on 3C-SiC (1 1 1) substrates. The comparison with the other polytypes suggests a similarity in the surface behaviour of 3C- and 6H-SiC.
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| 22. |
- Yazdi, G. Reza, et al.
(författare)
-
Growth of quality graphene on cubic silicon carbide
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The growth of epitaxial graphene was performed on the Si-face of 4H-SiC, 6H-SiC and 3C-SiC substrates by Si sublimation of SiC in Ar atmosphere at a temperature of 2000oC. Graphene surface morphology and thickness have been evaluated using low-energy electron microscopy (LEEM) and atomic force microscopy (AFM). Large homogeneous areas of graphene monolayers (over 50x50 μm2) have been successfully grown on 3C-SiC substrates. Differences in the morphology of graphene layers, grown on different SiC polytypes, are related to a large extent to minimization of the terrace surface energy during the step bunching process. The uniformity of Si sublimation is a decisive factor for obtaining large area homogeneous graphene. It is also shown that better quality graphene is grown on 3C-SiC substrates with smoother surface, because of less pronounced step bunching and lower distribution of step heights on polished surface.
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| 23. |
- Zoulis, Georgios, et al.
(författare)
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Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy
- 2010
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Ingår i: Silicon Carbide and Related Materials 2009. ; , s. 179-182
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Konferensbidrag (refereegranskat)abstract
- Both, n-type and p-type 3C-SiC samples grown on 6H-SiC substrates by sublimation epitaxy have been investigated. From low temperature photoluminescence studies, we demonstrate a low level of residual (n and/or p-type) doping with weak compensation, which is confirmed by secondary ion mass spectroscopy in the case of p-type samples.
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| 24. |
- Zoulis, G., et al.
(författare)
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Seeding layer influence on the low temperature photoluminescence intensity of 3C-SiC grown on 6H-SiC by sublimation epitaxy
- 2012
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Ingår i: HETEROSIC and WASMPE 2011. - : Trans Tech Publications Inc.. ; , s. 149-153
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Konferensbidrag (refereegranskat)abstract
- We report on n-type 3C-SiC samples grown by sublimation epitaxy. We focus on the low temperature photoluminescence intensity and show that the presence of a first conversion layer, grown at low temperature, is not only beneficial to improve the homogeneity of the polytype conversion but, also, to the LTPL signal intensity. From the use of a simple model, we show that this comes from a reduced density of non-radiative recombination centers.
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