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BETA
Ivanov, Ivan GueorguievORCID iD iconorcid.org/0000-0003-1000-0437
Alternative names
Publications (10 of 132) Show all publications
Shi, Y., Jokubavicius, V., Höjer, P., Ivanov, I. G., Yazdi, G., Yakimova, R., . . . Sun, J. W. (2019). A comparative study of high-quality C-face and Si-face 3C-SiC(1 1 1) grown on off-oriented 4H-SiC substrates. Journal of Physics D: Applied Physics, 52(34)
Open this publication in new window or tab >>A comparative study of high-quality C-face and Si-face 3C-SiC(1 1 1) grown on off-oriented 4H-SiC substrates
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2019 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 52, no 34Article in journal (Refereed) Published
Abstract [en]

We present a comparative study of the C-face and Si-face of 3C-SiC(111) grown on off-oriented 4H-SiC substrates by the sublimation epitaxy. By the lateral enlargement method, we demonstrate that the high-quality bulk-like C-face 3C-SiC with thickness of ~1 mm can be grown over a large single domain without double positioning boundaries (DPBs), which are known to have a strongly negative impact on the electronic properties of the material. Moreover, the C-face sample exhibits a smoother surface with one unit cell height steps while the surface of the Si-face sample exhibits steps twice as high as on the C-face due to step-bunching. High-resolution XRD and low temperature photoluminescence measurements show that C-face 3C-SiC can reach the same high crystalline quality as the Si-face 3C-SiC. Furthermore, cross-section studies of the C- and Si-face 3C-SiC demonstrate that in both cases an initial homoepitaxial 4H-SiC layer followed by a polytype transition layer are formed prior to the formation and lateral expansion of 3C-SiC layer. However, the transition layer in the C-face sample is extending along the step-flow direction less than that on the Si-face sample, giving rise to a more fairly consistent crystalline quality 3C-SiC epilayer over the whole sample compared to the Si-face 3C-SiC where more defects appeared on the surface at the edge. This facilitates the lateral enlargement of 3C-SiC growth on hexagonal SiC substrates.

Place, publisher, year, edition, pages
Biopress Ltd, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-159101 (URN)10.1088/1361-6463/ab2859 (DOI)000475964100002 ()
Note

Funding agencies:  Swedish Research Council (Vetenskapsradet) [621-2014-5461, 2018-04670, 2016-05362, 621-2014-5825]; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) [2016-00559]; Swedish Foundation for International Cooperation

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-08-07
Deminskyi, P., Rouf, P., Ivanov, I. G. & Pedersen, H. (2019). Atomic layer deposition of InN using trimethylindium and ammonia plasma. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 37(2), Article ID 020926.
Open this publication in new window or tab >>Atomic layer deposition of InN using trimethylindium and ammonia plasma
2019 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 2, article id 020926Article in journal (Refereed) Published
Abstract [en]

Indium nitride (InN) is a low bandgap, high electron mobility semiconductor material of interest to optoelectronics and telecommunication. Such applications require the deposition of uniform crystalline InN thin films on large area substrates, with deposition temperatures compatible with this temperature-sensitive material. As conventional chemical vapor deposition (CVD) struggles with the low temperature tolerated by the InN crystal, the authors hypothesize that a time-resolved, surface-controlled CVD route could offer a way forward for InN thin film deposition. In this work, the authors report atomic layer deposition of crystalline, wurtzite InN thin films using trimethylindium and ammonia plasma on Si(100). They found a narrow atomic layer deposition window of 240-260 degrees C with a deposition rate of 0.36 A/cycle and that the flow of ammonia into the plasma is an important parameter for the crystalline quality of the film. X-ray diffraction measurements further confirmed the polycrystalline nature of InN thin films. X-ray photoelectron spectroscopy measurements show nearly stoichiometric InN with low carbon level (amp;lt;1 at. %) and oxygen level (amp;lt;5 at. %) in the film bulk. The low carbon level is attributed to a favorable surface chemistry enabled by the NH3 plasma. The film bulk oxygen content is attributed to oxidation upon exposure to air via grain boundary diffusion and possibly by formation of oxygen containing species in the plasma discharge. Published by the AVS.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-155541 (URN)10.1116/1.5079279 (DOI)000460437200030 ()
Note

Funding Agencies|Swedish Foundation for Strategic Research through the project "Time-resolved low temperature CVD for III-nitrides" [SSF-RMA 15-0018]; Knut and Alice Wallenberg foundation through the project "Bridging the THz gap" [KAW 2013.0049]; VR [VR 2016-05362]; Carl Trygger Foundation

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-04-18
Nguyen, S. T., Stenberg, P., Jokubavicius, V., Ohshima, T., Ul-Hassan, J. & Ivanov, I. G. (2019). Ligand hyperfine interactions at silicon vacancies in 4H-SiC. Journal of Physics: Condensed Matter, 31(19), Article ID 195501.
Open this publication in new window or tab >>Ligand hyperfine interactions at silicon vacancies in 4H-SiC
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2019 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 31, no 19, article id 195501Article in journal (Refereed) Published
Abstract [en]

The negative silicon vacancy (V-Si(-)) in SiC has recently emerged as a promising defect for quantum communication and room-temperature quantum sensing. However, its electronic structure is still not well characterized. While the isolated Si vacancy is expected to give rise to only two paramagnetic centers corresponding to two inequivalent lattice sites in 4H-SiC, there have been five electron paramagnetic resonance (EPR) centers assigned to V-Si(-) in the past: the so-called isolated no-zero-field splitting (ZFS) V-Si(-) center and another four axial configurations with small ZFS: T-V1a, T-V2a, T-V1b, and T-V2b. Due to overlapping with Si-29 hyperfine (hf) structures in EPR spectra of natural 4H-SiC, hf parameters of T-V1a have not been determined. Using isotopically enriched 4H-(SiC)-Si-28, we overcome the problems of signal overlapping and observe hf parameters of nearest C neighbors for all three components of the S = 3/2 T-V1a and T-V2a centers. The obtained EPR data support the conclusion that only T-V1a and T-V2a are related to V-Si(-) and the two configurations of the so-called isolated no-ZFS V-Si(-) center, V-Si(-) (I) and V-Si(-) (II), are actually the central lines corresponding to the transition I-1/2 amp;lt;-amp;gt; I + 1/2 of the T-V2a and T-V1a centers, respectively.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
silicon vacancy; hyperfine interaction; electron paramagnetic resonance
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-155906 (URN)10.1088/1361-648X/ab072b (DOI)000461213400001 ()30763923 (PubMedID)
Note

Funding Agencies|Swedish Research Council [VR 2016-04068, VR 2016-05362]; Carl Trygger Stiftelse for Vetenskaplig Forskning [CTS 15:339]; Swedish Energy Agency [43611-1]; JSPS KAKENHI [A 17H01056]

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02
Shi, Y., Zakharov, A. A., Ivanov, I. G., Yazdi, G. R., Jokubavicius, V., Syväjärvi, M., . . . Sun, J. (2018). Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3CSiC (111). Carbon, 140, 533-542
Open this publication in new window or tab >>Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3CSiC (111)
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2018 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 140, p. 533-542Article in journal (Refereed) Published
Abstract [en]

Multilayer graphene has exhibited distinct electronic properties such as the tunable bandgap for optoelectronic applications. Among all graphene growth techniques, thermal decomposition of SiC is regarded as a promising method for production of device-quality graphene. However, it is still very challenging to grow uniform graphene over a large-area, especially multilayer graphene. One of the main obstacles is the occurrence of step bunching on the SiC surface, which significantly influences the formation process and the uniformity of the multilayer graphene. In this work, we have systematically studied the growth of monolayer and multilayer graphene on off-axis 3CSiC(111). Taking advantage of the synergistic effect of periodic SiC step edges as graphene nucleation sites and the unique thermal decomposition energy of 3CSiC steps, we demonstrate that the step bunching can be fully eliminated during graphene growth and large-area monolayer, bilayer, and four-layer graphene can be controllably obtained on high-quality off-axis 3CSiC(111) surface. The low energy electron microscopy results demonstrate that a uniform four-layer graphene has been grown over areas of tens of square micrometers, which opens the possibility to tune the bandgap for optoelectronic devices. Furthermore, a model for graphene growth along with the step bunching elimination is proposed.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-151054 (URN)10.1016/j.carbon.2018.08.042 (DOI)000450120200057 ()
Note

Funding agencies: Swedish Research Council (Vetenskapsradet) [621-2014-5461, 621-2014-5825]; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) [2016-00559]; Swedish Foundation for International Cooperation in Research and Higher 

Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2019-07-24
Shtepliuk, I. I., Vagin, M., Ivanov, I. G., Iakimov, T., Yazdi, G. & Yakimova, R. (2018). Lead (Pb) interfacing with epitaxial graphene. Physical Chemistry, Chemical Physics - PCCP, 20(25), 17105-17116
Open this publication in new window or tab >>Lead (Pb) interfacing with epitaxial graphene
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2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 25, p. 17105-17116Article in journal (Refereed) Published
Abstract [en]

Here, we report the electrochemical deposition of lead (Pb) as a model metal on epitaxial graphene fabricated on silicon carbide (Gr/SiC). The kinetics of electrodeposition and morphological characteristics of the deposits were evaluated by complementary electrochemical, physical and computational methods. The use of Gr/SiC as an electrode allowed the tracking of lead-associated redox conversions. The analysis of current transients passed during the deposition revealed an instantaneous nucleation mechanism controlled by convergent mass transport on the nuclei locally randomly distributed on epitaxial graphene. This key observation of the deposit topology was confirmed by low values of the experimentally-estimated apparent diffusion coefficient, Raman spectroscopy and scanning electron microscopy (SEM) studies. First principles calculations showed that the nucleation of Pb clusters on the graphene surface leads to weakening of the interaction strength of the metal-graphene complex, and only spatially separated Pb adatoms adsorbed on bridge and/or edge-plane sites can affect the vibrational properties of graphene. We expect that the lead adatoms can merge in large metallic clusters only at defect sites that reinforce the metal-graphene interactions. Our findings provide valuable insights into both heavy metal ion electrochemical analysis and metal electroplating on graphene interfaces that are important for designing effective detectors of toxic heavy metals.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-149854 (URN)10.1039/c8cp01814f (DOI)000436571800024 ()29896595 (PubMedID)
Note

Funding Agencies|VR grant [621-2014-5805]; SSF [SSF GMT14-0077, SSF RMA15-0024]; Angpanneforeningens Forskningsstiftelse [16-541]

Available from: 2018-08-02 Created: 2018-08-02 Last updated: 2018-08-20
Nagy, R., Widmann, M., Niethammer, M., Dasari, D. B. .., Gerhardt, I., Soykal, O. O., . . . Wrachtrup, J. (2018). Quantum Properties of Dichroic Silicon Vacancies in Silicon Carbide. Physical Review Applied, 9(3), Article ID 034022.
Open this publication in new window or tab >>Quantum Properties of Dichroic Silicon Vacancies in Silicon Carbide
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2018 (English)In: Physical Review Applied, E-ISSN 2331-7019, Vol. 9, no 3, article id 034022Article in journal (Refereed) Published
Abstract [en]

Although various defect centers have displayed promise as either quantum sensors, single photon emitters, or light-matter interfaces, the search for an ideal defect with multifunctional ability remains open. In this spirit, we study the dichroic silicon vacancies in silicon carbide that feature two well-distinguishable zero-phonon lines and analyze the quantum properties in their optical emission and spin control. We demonstrate that this center combines 40% optical emission into the zero-phonon lines showing the contrasting difference in optical properties with varying temperature and polarization, and a 100% increase in the fluorescence intensity upon the spin resonance, and long spin coherence time of their spin-3/2 ground states up to 0.6 ms. These results single out this defect center as a promising system for spin-based quantum technologies.

National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-147280 (URN)10.1103/PhysRevApplied.9.034022 (DOI)000428168800003 ()
Available from: 2018-04-12 Created: 2018-04-12 Last updated: 2018-04-24
Hänninen, T., Schmidt, S., Ivanov, I. G., Jensen, J., Hultman, L. & Högberg, H. (2018). Silicon carbonitride thin films deposited by reactive high power impulse magnetron sputtering. Surface & Coatings Technology, 335, 248-256
Open this publication in new window or tab >>Silicon carbonitride thin films deposited by reactive high power impulse magnetron sputtering
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2018 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 335, p. 248-256Article in journal (Refereed) Published
Abstract [en]

Amorphous silicon carbonitride thin films for biomedical applications were deposited in an industrial coating unit from a silicon target in different argon/nitrogen/acetylene mixtures by reactive high power impulse magnetron sputtering (rHiPIMS). The effects of acetylene (C2H2) flow rate, substrate temperature, substrate bias voltage, and HiPIMS pulse frequency on the film properties were investigated. Low C2H2 flow rates (<10 sccm) resulted in silicon nitride-like film properties, seen from a dense morphology when viewed in cross-sectional scanning electron microscopy, a hardness up to ∼22 GPa as measured by nanoindentation, and Si-N bonds dominating over Si-C bonds in X-ray photoelectron spectroscopy core-level spectra. Higher C2H2 flows resulted in increasingly amorphous carbon-like film properties, with a granular appearance of the film morphology, mass densities below 2 g/cm3 as measured by X-ray reflectivity, and a hardness down to 4.5 GPa. Increasing substrate temperatures and bias voltages resulted in slightly higher film hardnesses and higher compressive residual stresses. The film H/E ratio showed a maximum at film carbon contents ranging between 15 and 30 at.% and at elevated substrate temperatures from 340 °C to 520 °C.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Magnetron sputtering, Silicon carbonitride, Acetylene, Hardness, H/E
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-145178 (URN)10.1016/j.surfcoat.2017.12.037 (DOI)000424720800028 ()
Funder
EU, FP7, Seventh Framework Programme, GA-310477Carl Tryggers foundation , 15:219; 14:431
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2018-04-03
Schmidt, S., Czigany, Z., Wissting, J., Greczynski, G., Janzén, E., Jensen, J., . . . Hultman, L. (2016). A comparative study of direct current magnetron sputtering and high power impulse magnetron sputtering processes for CNX thin film growth with different inert gases. Diamond and related materials, 64, 13-26
Open this publication in new window or tab >>A comparative study of direct current magnetron sputtering and high power impulse magnetron sputtering processes for CNX thin film growth with different inert gases
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2016 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 64, p. 13-26Article in journal (Refereed) Published
Abstract [en]

Reactive direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) discharges of carbon in different inert gas mixtures (N-2/Ne, N-2/Ar, and N-2/Kr) were investigated for the growth of carbon-nitride (CNX) thin films. Ion mass spectrometry showed that energies of abundant plasma cations are governed by the inert gas and the N-2-to-inert gas flow ratios. The population of ion species depends on the sputter mode; HiPIMS yields approximately ten times higher flux ratios of ions originating from the target to process gas ions than DCMS. Exceptional are discharges in Ne with N-2-to-Ne flow ratios &lt;20%. Here, cation energies and the amount of target ions are highest without influence on the sputter mode. CNX thin films were deposited in 14% N-2/inert gas mixtures at substrate temperatures of 110 degrees C and 430 degrees C. The film properties show a correlation to the substrate temperature, the applied inert gas and sputter mode. The mechanical performance of the films is mainly governed by their morphology and composition, but not by their microstructure. Amorphous and fullerene-like CN0.14 films exhibiting a hardness of similar to 15 GPa and an elastic recovery of similar to 90% were deposited at 110 degrees C in reactive Kr atmosphere by DCMS and HiPIMS.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2016
Keywords
Magnetron sputtering; Inert gases; Plasma analysis; Langmuir probe measurement; CNX film stress; CNX hardness
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128146 (URN)10.1016/j.diamond.2016.01.009 (DOI)000374608100003 ()
Note

Funding Agencies|Carl Tryggers Foundation for Scientific Research; Hungarian Academy of Sciences

Available from: 2016-05-19 Created: 2016-05-19 Last updated: 2017-11-30
Booker, I. D., Farkas, I., Ivanov, I. G., Ul Hassan, J. & Janzén, E. (2016). Chloride-based SiC growth on a-axis 4H-€“SiC substrates. Paper presented at 6th South African Conference on Photonic Materials (SACPM 2015), Mabula Game Lodge, South Africa, 4 – 8 May 2015. Physica. B, Condensed matter, 480, 23-25
Open this publication in new window or tab >>Chloride-based SiC growth on a-axis 4H-€“SiC substrates
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2016 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 480, p. 23-25Article in journal (Refereed) Published
Abstract [en]

Abstract SiC has, during the last few years, become increasingly important as a power-device material for high voltage applications. The thick, low-doped voltage-supporting epitaxial layer is normally grown by CVD on 4° off-cut 4H–SiC substrates at a growth rate of 5 – 10 ÎŒ m / h using silane (SiH4) and propane (C3H8) or ethylene (C2H4) as precursors. The concentrations of epitaxial defects and dislocations depend to a large extent on the underlying substrate but can also be influenced by the actual epitaxial growth process. Here we will present a study on the properties of the epitaxial layers grown by a Cl-based technique on an a-axis (90° off-cut from c-direction) 4H–SiC substrate.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
4H–SiC; a-face; DLTS; Photoluminescence; Raman; Epitaxy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-123948 (URN)10.1016/j.physb.2015.08.038 (DOI)000365600300005 ()
Conference
6th South African Conference on Photonic Materials (SACPM 2015), Mabula Game Lodge, South Africa, 4 – 8 May 2015
Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
Jokubavicius, V., Sun, J., Liu, X., Yazdi, G., Ivanov, I. G., Yakimova, R. & Syväjärvi, M. (2016). Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum. Journal of Crystal Growth, 448, 51-57
Open this publication in new window or tab >>Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum
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2016 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 448, p. 51-57Article in journal (Refereed) Published
Abstract [en]

We demonstrate growth of thick SiC layers (100–200 µm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10−5 mbar) at temperatures varying from 1700 to 1975 °C with growth rates up to 270 µm/h and 70 µm/h for 6H- and 4H–SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C–SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200 µm thick homoepitaxial 6H–SiC layer co-doped with nitrogen and boron in a range of 1018 cm−3 at a growth rate of about 270 µm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer.

Keywords
Mass transfer;Substrates;Single crystal growth;Semiconducting materials
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-128610 (URN)10.1016/j.jcrysgro.2016.05.017 (DOI)
Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2017-11-30
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1000-0437

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