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Yakimova, Rositsa
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Publications (10 of 402) 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
Li, F., Jokubavicius, V., Jennings, M., Yakimova, R., Tomas, A. P., Russell, S., . . . La Via, F. (2019). Electrical Characterisation of Thick 3C-SiC Layers Grown on Off-Axis 4H-SiC Substrates. Materials Science Forum, 963, 353-356
Open this publication in new window or tab >>Electrical Characterisation of Thick 3C-SiC Layers Grown on Off-Axis 4H-SiC Substrates
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2019 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 963, p. 353-356Article in journal (Refereed) Published
Abstract [en]

300 μm thick 3C-SiC epilayer was grown on off-axis 4H-SiC(0001) substrate with a high growth rate of 1 mm/hour. Dry oxidation, wet oxidation and N2O anneal were applied to fabricate lateral MOS capacitors on these 3C-SiC layers. MOS interface obtained by N2O anneal has the lowest interface trap density of 3~4x1011 eV-1cm-2. Although all MOS capacitors still have positive net charges at the MOS interface, the wet oxidised sample has the lowest effective charge density of ~9.17x1011 cm-2.

Place, publisher, year, edition, pages
Trans Tech Publications, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-160225 (URN)10.4028/www.scientific.net/MSF.963.353 (DOI)2-s2.0-85071861789 (Scopus ID)
Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2019-09-17Bibliographically approved
Zakharov, A., Vinogradov, N. A., Aprojanz, J., Nguyen, T. T., Tegenkamp, C., Struzzi, C., . . . Jokubavicius, V. (2019). Wafer Scale Growth and Characterization of Edge Specific Graphene Nanoribbons for Nanoelectronics. ACS Applied Nano Materials, 2(1), 156-162
Open this publication in new window or tab >>Wafer Scale Growth and Characterization of Edge Specific Graphene Nanoribbons for Nanoelectronics
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2019 (English)In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 2, no 1, p. 156-162Article in journal (Refereed) Published
Abstract [en]

One of the ways to use graphene in field effect transistors is to introduce a band gap by quantum confinement effect. That is why narrow graphene nanoribbons (GNRs) with width less than 50 nm are considered to be essential components in future graphene electronics. The growth of graphene on sidewalls of SiC(0001) mesa structures using scalable photolithography was shown to produce high quality GNRs with excellent transport properties. Such epitaxial graphene nanoribbons are very important in fundamental science but if GNRs are supposed to be used in advanced nanoelectronics, high quality thin (<50 nm) nanoribbons should be produced on a large (wafer) scale. Here we present a technique for scalable template growth of high quality GNRs on Si-face of SiC(0001) and provide detailed structural information along with transport properties. For the first time we succeeded now to avoid SiC-facet instabilities in order to grow high quality GNRs along both [11̅00] and [112̅0] crystallographic directions on the same substrate. The quality of the grown nanoribbons was confirmed by comprehensive characterization with atomic resolution STM, dark field LEEM, and transport measurements. This approach generates an entirely new platform for both fundamental and application driven research of quasi one-dimensional carbon based magnetism and spintronics.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-160224 (URN)10.1021/acsanm.8b01780 (DOI)000464491500018 ()
Available from: 2019-09-11 Created: 2019-09-11 Last updated: 2019-09-17Bibliographically approved
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
Nachawaty, A., Yang, M., Nanot, S., Kazazis, D., Yakimova, R., Escoffier, W. & Jouault, B. (2018). Large nonlocality in macroscopic Hall bars made of epitaxial graphene. Physical Review B, 98(4), Article ID 045403.
Open this publication in new window or tab >>Large nonlocality in macroscopic Hall bars made of epitaxial graphene
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 4, article id 045403Article in journal (Refereed) Published
Abstract [en]

We report on nonlocal transport in large-scale epitaxial graphene on silicon carbide under an applied external magnetic field. The nonlocality is related to the emergence of the quantum Hall regime and persists up to the millimeter scale. The nonlocal resistance reaches values comparable to the local (Hall and longitudinal) resistances. At moderate magnetic fields, it is almost independent on the in-plane component of the magnetic field, which suggests that spin currents are not at play. The nonlocality cannot be explained by thermoelectric effects without assuming extraordinary large Nernst and Ettingshausen coefficients. A model based on counterpropagating edge states backscattered by the bulk reproduces quite well the experimental data.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-149682 (URN)10.1103/PhysRevB.98.045403 (DOI)000437110900005 ()
Note

Funding Agencies|French Agence Nationale de la Recherche [ANR-16-CE09-0016]; grant NEXT [ANR-10-LABX-0037]

Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-08-14
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
Jokubavicius, V., Syväjärvi, M. & Yakimova, R. (2018). Silicon Carbide Surface Cleaning and Etching. In: Konstantinos Zekentes and Konstantin Vasilevskiy (Ed.), Advancing Silicon Carbide Electronics Technology I: (pp. 1-26). Materials Research Forum LLC
Open this publication in new window or tab >>Silicon Carbide Surface Cleaning and Etching
2018 (English)In: Advancing Silicon Carbide Electronics Technology I / [ed] Konstantinos Zekentes and Konstantin Vasilevskiy, Materials Research Forum LLC , 2018, p. 1-26Chapter in book (Refereed)
Abstract [en]

Silicon carbide (SiC) surface cleaning and etching (wet, electrochemical, thermal) are important technological processes in preparation of SiC wafers for crystal growth, defect analysis or device processing. While removal of organic, particulate and metallic contaminants by chemical cleaning is a routine process in research and industrial production, the etching which, in addition to structural defects analysis, can also be used to modify wafer surface structure, is very interesting for development of innovative device concepts. In this book chapter we review SiC chemical cleaning and etching procedures and present perspectives of SiC etching for new device development.

Place, publisher, year, edition, pages
Materials Research Forum LLC, 2018
Series
Materials Research Foundations, ISSN 2471-8890, E-ISSN 2471-8904 ; 37
Keywords
Silicon Carbide, Chemical Cleaning, Wet Etching, Electrochemical Etching, Porous SiC
Identifiers
urn:nbn:se:liu:diva-151048 (URN)10.21741/9781945291852-1 (DOI)9781945291845 (ISBN)9781945291852 (ISBN)
Available from: 2018-09-11 Created: 2018-09-11 Last updated: 2018-09-24Bibliographically approved
Shavanova, K., Bakakina, Y., Burkova, I., Shtepliuk, I., Viter, R., Ubelis, A., . . . Khranovskyy, V. (2016). Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology. Sensors, 16(2)
Open this publication in new window or tab >>Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology
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2016 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 16, no 2Article, review/survey (Refereed) Published
Abstract [en]

The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

Place, publisher, year, edition, pages
MDPI AG, 2016
Keywords
transition metal dichalcogenides; transducers; beyond graphene; biosensors; two-dimensional materials; two-dimensional oxides; transition metal oxides
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-126850 (URN)10.3390/s16020223 (DOI)000371787800102 ()26861346 (PubMedID)
Note

Funding Agencies|EC FP-7 International Research Staff Exchange Scheme (IRSES) Grant [318520]; Linkoping Linnaeus Initiative for Novel Functional Materials (LiLi-NFM); European Union [604391]; Swedish Research Council (VR) Marie Sklodowska Curie International Career Grant [2015-00679]

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-11-30
Beshkova, M., Hultman, L. & Yakimova, R. (2016). Device applications of epitaxial graphene on silicon carbide. Vacuum, 128, 186-197
Open this publication in new window or tab >>Device applications of epitaxial graphene on silicon carbide
2016 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 128, p. 186-197Article, review/survey (Refereed) Published
Abstract [en]

Graphene has become an extremely hot topic due to its intriguing material properties allowing for ground-breaking fundamental research and applications. It is one of the fastest developing materials during the last several years. This progress is also driven by the diversity of fabrication methods for graphene of different specific properties, size, quantity and cost. Graphene grown on SiC is of particular interest due to the possibility to avoid transferring of free standing graphene to a desired substrate while having a large area SiC (semi-insulating or conducting) substrate ready for device processing. Here, we present a review of the major current explorations of graphene on SiC in electronic devices, such as field effect transistors (FET), radio frequency (RF) transistors, integrated circuits (IC), and sensors. The successful role of graphene in the metrology sector is also addressed. Typical examples of graphene on SiC implementations are illustrated and the drawbacks and promises are critically analyzed. (C) 2016 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Graphene FET; RF-transistors; IC; Graphene sensors; Detectors; Quantum Hall resistance
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-129150 (URN)10.1016/j.vacuum.2016.03.027 (DOI)000376052500026 ()
Note

Funding Agencies|European Union [604391]; Swedish Research Council [VR 621-2014-5805]; LiU Linnaeus Grant

Available from: 2016-06-13 Created: 2016-06-13 Last updated: 2017-11-28
Shtepliuk, I., Khranovskyy, V. & Yakimova, R. (2016). Effect of c-axis inclination angle on the properties of ZnO/Zn1-xCdxO/ZnO quantum wells. Thin Solid Films, 603, 139-148
Open this publication in new window or tab >>Effect of c-axis inclination angle on the properties of ZnO/Zn1-xCdxO/ZnO quantum wells
2016 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 603, p. 139-148Article in journal (Refereed) Published
Abstract [en]

The development of optoelectronic devices based on highly-promising Zn1 - xCdxO semiconductor system demands deep understanding of the properties of the Zn1 - xCdxO-based quantum wells (QWs). In this regard, we carried out a numerical study of the polarization-related effects in polar, semi-polar and non-polar ZnO/ Zn1 - xCd xO/ZnO QWs with different parameters of the quantum well structure. The effects of well width, barrier thickness, cadmium content in the active layer and c-axis inclination angle on the distribution of the electron and hole wave function and transition energy were investigated using the 6 x 6 k center dot p Hamiltonian and one-dimensional self-consistent solutions of nonlinear Schrodinger-Poisson equations with consideration of spatially varying dielectric constant and effective mass. The strong sensitivity of the internal electric field, transition energy and overlap integral to cadmium content and well thickness in the angle range from 0 to 40 degrees was revealed. An unexpected change of the internal electric fields sign was observed at the angles ranging from 70 to 90 degrees. We also found a difference in the electronic properties between (0001)-, (11 (2) over bar2)-and (10 (1) over bar0)-oriented QWs.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2016
Keywords
Inclination angle; Quantum well; Polarization; ZnCdO alloy; Transition energy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-127431 (URN)10.1016/j.tsf.2016.02.007 (DOI)000372794900022 ()
Note

Funding Agencies|Swedish Institute scholarship

Available from: 2016-05-01 Created: 2016-04-26 Last updated: 2017-11-30
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