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Ivanov, Ivan GueorguievORCID iD iconorcid.org/0000-0003-1000-0437
Alternative names
Publications (10 of 126) Show all publications
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
Khranovskyy, V., Shtepliuk, I., Ivanov, I. G., Tsiaoussis, I. & Yakimova, R. (2016). Light emission enhancement from ZnO nanostructured films grown on Gr/SiC substrates. Carbon, 99, 295-301
Open this publication in new window or tab >>Light emission enhancement from ZnO nanostructured films grown on Gr/SiC substrates
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2016 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 99, p. 295-301Article in journal (Refereed) Published
Abstract [en]

We report on the application of a single layer graphene substrates for the growth of polycrystalline ZnO films with advanced light emission properties. Unusually high ultraviolet (UV) and visible (VIS) photoluminesce was observed from the ZnO/Gr/SiC structures in comparison to identical samples without graphene. The photoluminescence intensity depends non-monotonically on the films thickness, reaching its maximum for 150 nm thick films. The phenomena observed is explained as due to the dual graphene role: i) the dangling bond free substrate, providing growth of relaxed thin ZnO layers ii) a back reflector active mirror of the Fabry-Perot cavity that is formed. The reported results demonstrate the potential of two-dimensional carbon materials integration with light emitting wide band gap semiconductors and can be of practical importance for the design of future optoelectronic devices.

Place, publisher, year, edition, pages
Pergamon Press, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-123947 (URN)10.1016/j.carbon.2015.12.010 (DOI)000369069800035 ()
Note

Funding agencies:  Linkoping Linnaeus Initiative for Novel Functional Materials (LiLi-NFM); Angpanneforeningens Forskningsstiftelse [14-517]; European Union [604391]

Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
Eriksson, J., Puglisi, D., Strandqvist, C., Gunnarsson, R., Ekeroth, S., Ivanov, I. G., . . . Lloyd Spetz, A. (2016). Modified Epitaxial Graphene on SiC for Extremely Sensitive andSelective Gas Sensors. Paper presented at ICSCRM 2015, The International Conference on Silicon Carbide and Related Materials, 4-9 October 2015, Giardini Naxos, Italy. Materials Science Forum, 858, 1145-1148
Open this publication in new window or tab >>Modified Epitaxial Graphene on SiC for Extremely Sensitive andSelective Gas Sensors
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2016 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, p. 1145-1148Article in journal (Refereed) Published
Abstract [en]

Two-dimensional materials offer a unique platform for sensing where extremely high sensitivity is a priority, since even minimal chemical interaction causes noticeable changes inelectrical conductivity, which can be used for the sensor readout. However, the sensitivity has to becomplemented with selectivity, and, for many applications, improved response- and recovery times are needed. This has been addressed, for example, by combining graphene (for sensitivity) with metal/oxides (for selectivity) nanoparticles (NP). On the other hand, functionalization or modification of the graphene often results in poor reproducibility. In this study, we investigate thegas sensing performance of epitaxial graphene on SiC (EG/SiC) decorated with nanostructured metallic layers as well as metal-oxide nanoparticles deposited using scalable thin-film depositiontechniques, like hollow-cathode pulsed plasma sputtering. Under the right modification conditions the electronic properties of the surface remain those of graphene, while the surface chemistry can betuned to improve sensitivity, selectivity and speed of response to several gases relevant for airquality monitoring and control, such as nitrogen dioxide, benzene, and formaldehyde.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2016
Keywords
Epitaxial graphene, graphene hybrid materials, gas sensor
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128078 (URN)10.4028/www.scientific.net/MSF.858.1145 (DOI)
Conference
ICSCRM 2015, The International Conference on Silicon Carbide and Related Materials, 4-9 October 2015, Giardini Naxos, Italy
Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2018-03-26
Winters, M., Habibpour, O., Gueorguiev Ivanov, I., ul-Hassan, J., Janzén, E., Zirath, H. & Rorsman, N. (2015). Assessment of H-intercalated graphene for microwave FETs through material characterization and electron transport studies. Carbon, 81, 96-104
Open this publication in new window or tab >>Assessment of H-intercalated graphene for microwave FETs through material characterization and electron transport studies
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2015 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 81, p. 96-104Article in journal (Refereed) Published
Abstract [en]

Epitaxial graphene is grown on semi-insulating (SI) 4H-SiC in a hot wall CVD reactor by graphitization and in-situ intercalation with (H)ydrogen. A holistic material characterization is performed in order to ascertain the number of layers, layer uniformity, and electron transport properties of the epi-layers via electronic test structures and Raman spectroscopy. Bilayer graphene field effect transistors (GFETs) are fabricated using a full electron beam lithography (EBL) process which is optimized for low contact resistances of r(c) less than 0.2 Omega mm. Mobilities of order 2500 cm(2)/V s are achieved on bilayer samples after fabrication. The devices demonstrate high transconductance g(m) = 400 mS/mm and high current density I-ds = 1.8 A/mm. The output conductance at the bias of maximum transconductance is g(ds) = 300 mS/mm. The GFETs demonstrate an extrinsic f(t)(ext) and f(max)(ext) of 20 and 13 GHz, respectively and show 6 dB power gain at 1 GHz in a 50 Omega system, which is the highest reported to date.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-113163 (URN)10.1016/j.carbon.2014.09.029 (DOI)000345682900011 ()
Note

Funding Agencies|European Science Foundation (ESF) under the EUROCORES Program EuroGRAPHENE; EU Graphene Flagship [604391]; Swedish Foundation for Strategic Research (SSF); Knut and Alice Wallenberg Foundation (KAW); EPIGRAT project

Available from: 2015-01-14 Created: 2015-01-12 Last updated: 2017-12-05
Yazdanfar, M., Kalered, E., Danielsson, Ö., Kordina, O., Nilsson, D., Ivanov, I. G., . . . Pedersen, H. (2015). Brominated chemistry for chemical vapor deposition of electronic grade SiC. Chemistry of Materials, 27(3), 793-801
Open this publication in new window or tab >>Brominated chemistry for chemical vapor deposition of electronic grade SiC
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2015 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 3, p. 793-801Article in journal (Refereed) Published
Abstract [en]

Chlorinated chemical vapor deposition (CVD) chemistry for growth of homoepitaxial layers of silicon carbide (SiC) has paved the way for very thick epitaxial layers in short deposition time as well as novel crystal growth processes for SiC. Here, we explore the possibility to also use a brominated chemistry for SiC CVD by using HBr as additive to the standard SiC CVD precursors. We find that brominated chemistry leads to the same high material quality and control of material properties during deposition as chlorinated chemistry and that the growth rate is on average 10 % higher for a brominated chemistry compared to chlorinated chemistry. Brominated and chlorinated SiC CVD also show very similar gas phase chemistries in thermochemical modelling. This study thus argues that brominated chemistry is a strong alternative for SiC CVD since the deposition rate can be increased with preserved material quality. The thermochemical modelling also suggest that the currently used chemical mechanism for halogenated SiC CVD might need to be revised.

National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-111075 (URN)10.1021/acs.chemmater.5b00074 (DOI)000349934500016 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2018-06-19Bibliographically approved
Westlund, A., Winters, M., Ivanov, I. G., Ul-Hassan, J., Nilsson, P.-A. -., Janzén, E., . . . Grahn, J. (2015). Correction: Graphene self-switching diodes as zero-bias microwave detectors (vol 106, 093116, 2015). Applied Physics Letters, 106(15), Article ID 159902.
Open this publication in new window or tab >>Correction: Graphene self-switching diodes as zero-bias microwave detectors (vol 106, 093116, 2015)
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2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 15, article id 159902Article in journal (Other academic) Published
Abstract [en]

n/a

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2015
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-118246 (URN)10.1063/1.4916581 (DOI)000353160700053 ()
Available from: 2015-06-04 Created: 2015-05-22 Last updated: 2017-12-04
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1000-0437

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