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Yakimova, Rositsa
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Backes, C., Abdelkader, A. M., Alonso, C., Andrieux-Ledier, A., Arenal, R., Azpeitia, J., . . . Garcia-Hernandez, M. (2020). Production and processing of graphene and related materials. 2D MATERIALS, 7(2), Article ID 022001.
Open this publication in new window or tab >>Production and processing of graphene and related materials
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2020 (English)In: 2D MATERIALS, ISSN 2053-1583, Vol. 7, no 2, article id 022001Article, review/survey (Refereed) Published
Abstract [en]

We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a hands-on approach, providing practical details and procedures as derived from literature as well as from the authors experience, in order to enable the reader to reproduce the results. Section I is devoted to bottom up approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers top down techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers and modified Hummers methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resource-consuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown. Section VIII discusses advances in GRM functionalization. A broad range of organic molecules can be anchored to the sp(2) basal plane by reductive functionalization. Negatively charged graphene can be prepared in liquid phase (e.g. via intercalation chemistry or electrochemically) and can react with electrophiles. This can be achieved both in dispersion or on substrate. The functional groups of GO can be further derivatized. Graphene can also be noncovalently functionalized, in particular with polycyclic aromatic hydrocarbons that assemble on the sp(2) carbon network by pi-pi stacking. In the liquid phase, this can enhance the colloidal stability of SLG/FLG. Approaches to achieve noncovalent on-substrate functionalization are also discussed, which can chemically dope graphene. Research efforts to derivatize CNMs are also summarized, as well as novel routes to selectively address defect sites. In dispersion, edges are the most dominant defects and can be covalently modified. This enhances colloidal stability without modifying the graphene basal plane. Basal plane point defects can also be modified, passivated and healed in ultra-high vacuum. The decoration of graphene with metal nanoparticles (NPs) has also received considerable attention, as it allows to exploit synergistic effects between NPs and graphene. Decoration can be either achieved chemically or in the gas phase. All LMs, can be functionalized and we summarize emerging approaches to covalently and noncovalently functionalize MoS2 both in the liquid and on substrate. Section IX describes some of the most popular characterization techniques, ranging from optical detection to the measurement of the electronic structure. Microscopies play an important role, although macroscopic techniques are also used for the measurement of the properties of these materials and their devices. Raman spectroscopy is paramount for GRMs, while PL is more adequate for non-graphene LMs (see section IX.2). Liquid based methods result in flakes with different thicknesses and dimensions. The qualification of size and thickness can be achieved using imaging techniques, like scanning probe microscopy (SPM) or transmission electron microscopy (TEM) or spectroscopic techniques. Optical microscopy enables the detection of flakes on suitable surfaces as well as the measurement of optical properties. Characterization of exfoliated materials is essential to improve the GRM metrology for applications and quality control. For grown GRMs, SPM can be used to probe morphological properties, as well as to study growth mechanisms and quality of transfer. More generally, SPM combined with smart measurement protocols in various modes allows one to get obtain information on mechanical properties, surface potential, work functions, electrical properties, or effectiveness of functionalization. Some of the techniques described are suitable for in situ characterization, and can be hosted within the growth chambers. If the diagnosis is made ex situ, consideration should be given to the preparation of the samples to avoid contamination. Occasionally cleaning methods have to be used prior to measurement.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2020
Keywords
processing of layered materials; inks of layered materials; characterization of layered materials; functionalization of layered materials; synthesis of graphene and related materials; growth of layered materials
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-163645 (URN)10.1088/2053-1583/ab1e0a (DOI)000510223300001 ()
Note

Funding Agencies|European Commission Graphene Flagship Core1 [696656, 785219]

Available from: 2020-02-18 Created: 2020-02-18 Last updated: 2020-03-12
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
Keywords
Quality management; Layers; Two dimensional materials; Chemical structure; Scanning tunneling microscopy
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: 2020-03-25Bibliographically approved
Rodner, M., Puglisi, D., Yakimova, R. & Eriksson, J. (2018). A platform for extremely sensitive gas sensing: 2D materials on silicon carbide. In: : . Paper presented at Materials for Energy, Efficiency and Sustainablility: TechConnect Briefs (pp. 101-104). , 2
Open this publication in new window or tab >>A platform for extremely sensitive gas sensing: 2D materials on silicon carbide
2018 (English)Conference paper, Published paper (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-162244 (URN)978-0-9988782-3-2 (ISBN)
Conference
Materials for Energy, Efficiency and Sustainablility: TechConnect Briefs
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-12-05Bibliographically 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
Santangelo, M. F., Shtepliuk, I. I., Puglisi, D., Filippini, D., Yakimova, R. & Eriksson, J. (2018). Epitaxial graphene sensors combined with 3D printed microfluidic chip for heavy metals detection. Paper presented at EUROSENSORS 2018. Proceedings, 2(13), Article ID 982.
Open this publication in new window or tab >>Epitaxial graphene sensors combined with 3D printed microfluidic chip for heavy metals detection
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2018 (English)In: Proceedings, ISSN 2504-3900, Vol. 2, no 13, article id 982Article in journal (Refereed) Published
Abstract [en]

Two-dimensional materials may constitute key elements in the development of a sensing platform where extremely high sensitivity is required, since even minimal chemical interaction can generate appreciable changes in the electronic state of the material. In this work, we investigate the sensing performance of epitaxial graphene on Si-face 4H-SiC (EG/SiC) for liquid-phase detection of heavy metals (e.g., Pb). The integration of preparatory steps needed for sample conditioning is included in the sensing platform, exploiting fast prototyping using a 3D printer, which allows direct fabrication of a microfluidic chip incorporating all the features required to connect and execute the Lab-on-chip (LOC) functions. It is demonstrated that interaction of Pb2+ ions in water-based solutions with the EG enhances its conductivity exhibiting a Langmuir correlation between signal and Pb2+ concentration. Several concentrations of Pb2+ solutions ranging from 125 nM to 500 µM were analyzed showing good stability and reproducibility over time.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
heavy metals detection; epitaxial graphene; high sensitivity; 3D printed flow cell; reusable lab-on-chip
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:liu:diva-162243 (URN)10.3390/proceedings2130982 (DOI)
Conference
EUROSENSORS 2018
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-12-03Bibliographically approved
Rodner, M., Puglisi, D., Helmersson, U., Ivanov, I. G., Yakimova, R., Uvdal, K., . . . Eriksson, J. (2018). Iron oxide nanoparticle decorated graphene for ultra-sensitive detection of volatile organic compounds. Paper presented at EUROSENSORS 2018. Proceedings, 2(13), Article ID 985.
Open this publication in new window or tab >>Iron oxide nanoparticle decorated graphene for ultra-sensitive detection of volatile organic compounds
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2018 (English)In: Proceedings, ISSN 2504-3900, Vol. 2, no 13, article id 985Article in journal (Refereed) Published
Abstract [en]

It has been found that two-dimensional materials, such as graphene, can be used as remarkable gas detection platforms as even minimal chemical interactions can lead to distinct changes in electrical conductivity. In this work, epitaxially grown graphene was decorated with iron oxide nanoparticles for sensor performance tuning. This hybrid surface was used as a sensing layer to detect formaldehyde and benzene at concentrations of relevance in air quality monitoring (low parts per billion). Moreover, the time constants could be drastically reduced using a derivative sensor signal readout, allowing detection at the sampling rates desired for air quality monitoring applications.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
epitaxial graphene; metal oxide nanoparticle; gas sensor; volatile organic compounds; benzene; formaldehyde; derivative sensor signal
National Category
Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-162242 (URN)10.3390/proceedings2130985 (DOI)
Conference
EUROSENSORS 2018
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2020-01-14Bibliographically approved
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
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