| 1. |
- Jamnig, Andreas, et al.
(författare)
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3D-to-2D Morphology Manipulation of Sputter-Deposited Nanoscale Silver Films on Weakly Interacting Substrates via Selective Nitrogen Deployment for Multifunctional Metal Contacts
- 2020
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Ingår i: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:5, s. 4728-4738
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Tidskriftsartikel (refereegranskat)abstract
- The ability to reverse the inherent tendency of noble metals to grow in an uncontrolled three-dimensional (3D) fashion on weakly interacting substrates, including two-dimensional (2D) materials and oxides, is essential for the fabrication of high-quality multifunctional metal contacts in key enabling devices. In this study, we show that this can be effectively achieved by deploying nitrogen (N-2) gas with high temporal precision during magnetron sputtering of nanoscale silver (Ag) islands and layers on silicon dioxide (SiO2) substrates. We employ real-time in situ film growth monitoring using spectroscopic ellipsometry, along with optical modeling in the framework of the finite-difference time-domain method, and establish that localized surface plasmon resonance (LSPR) from nanoscale Ag islands can be used to gauge the evolution of surface morphology of discontinuous layers up to a SiO2 substrate area coverage of similar to 70%. Such analysis, in combination with data on the evolution of room-temperature resistivity of electrically conductive layers, reveals that presence of N-2 in the sputtering gas atmosphere throughout all film-formation stages: (i) promotes 2D growth and smooth film surfaces and (ii) leads to an increase of the continuous-layer electrical resistivity by similar to 30% compared to Ag films grown in a pure argon (Ar) ambient atmosphere. Detailed ex situ nanoscale structural analyses suggest that N-2 favors 2D morphology by suppressing island coalescence rates during initial growth stages, while it causes interruption of local epitaxial growth on Ag crystals. Using these insights, we deposit Ag layers by deploying N-2 selectively, either during the early precoalescence growth stages or after coalescence completion. We show that early N-2 deployment leads to 2D morphology without affecting the Ag-layer resistivity, while postcoalescence introduction of N-2 in the gas atmosphere further promotes formation of three-dimensional (3D) nanostructures and roughness at the film growth front. In a broader context this study generates knowledge that is relevant for the development of (i) single-step growth manipulation strategies based on selective deployment of surfactant species and (ii) real-time methodologies for tracking film and nanostructure morphological evolution using LSPR.
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| 2. |
- Colin, Jonathan, et al.
(författare)
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In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools
- 2020
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 10:11
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Forskningsöversikt (refereegranskat)abstract
- Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of similar to 2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal beta-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.
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| 3. |
- Jamnig, Andreas, et al.
(författare)
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Manipulation of thin metal film morphology on weakly interacting substrates via selective deployment of alloying species
- 2022
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 40:3
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a versatile concept for manipulating morphology of thin (& LE;25 nm) noble-metal films on weakly interacting substrates using growth of Ag on SiO2 as a model system. The concept entails deployment of minority metallic (Cu, Au, Al, Ti, Cr, and Mo) alloying species at the Ag-layer growth front. Data from in situ and real-time monitoring of the deposition process show that all alloying agents-when deployed together with Ag vapor throughout the entire film deposition-favor two-dimensional (2D) growth morphology as compared to pure Ag film growth. This is manifested by an increase in the substrate area coverage for a given amount of deposited material in discontinuous layers and a decrease of the thickness at which a continuous layer is formed, though at the expense of a larger electrical resistivity. Based on ex situ microstructural analyses, we conclude that 2D morphological evolution under the presence of alloying species is predominantly caused by a decrease of the rate of island coalescence completion during the initial film-formation stages. Guided by this realization, alloying species are released with high temporal precision to selectively target growth stages before and after coalescence completion. Pre-coalescence deployment of all alloying agents yields a more pronounced 2D growth morphology, which for the case of Cu, Al, and Au is achieved without compromising the Ag-layer electrical conductivity. A more complex behavior is observed when alloying atoms are deposited during the post-coalescence growth stages: Cu, Au, Al, and Cr favor 2D morphology, while Ti and Mo yield a more pronounced three-dimensional morphological evolution. The overall results presented herein show that targeted deployment of alloying agents constitutes a generic platform for designing bespoken heterostructures between metal layers and technologically relevant weakly interacting substrates.& nbsp;Published under an exclusive license by the AVS.
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| 4. |
- Jamnig, Andreas, 1991-, et al.
(författare)
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On the effect of copper as wetting agent during growth of thin silver films on silicon dioxide substrates
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 538
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Tidskriftsartikel (refereegranskat)abstract
- We study the effect of Cu incorporation on the morphological evolution and the optoelectronic properties of thin Ag films deposited by magnetron sputtering on weakly-interacting SiO2 substrates. In situ and real time spectroscopic ellipsometry data show that by adding up to 4at.% Cu throughout the entire film deposition process, wetting of the substrate by the metal layer is promoted, as evidenced by a decrease of the thickness at which the film becomes continuous from 19.5nm (pure Ag) to 15nm (Ag96Cu4). The in situ data are consistent with ex situ x-ray reflectometry analyses which show that Cu-containing films exhibit a root mean square roughness of 1.3nm compared to the value 1.8nm for pure Ag films, i.e., Cu leads to smoother film surfaces. These morphological changes are coupled with an increase in continuous-layer electrical resistivity from 1.0×10-5Ωcm (Ag) to 1.25×10-5Ωcm (Ag96Cu4). Scanning electron microscopic studies of discontinuous layers reveal that the presence of Cu at the film growth front promotes smooth surfaces (as compared to pure Ag films) by hindering the rate of island coalescence. To further understand the effect of Cu on film growth and electrical properties, in a second set of experiments, we deploy Cu with high temporal precision to target specific film-formation stages. The results show that longer presence of Cu in the vapor flux and the film growth front promote flat morphology. However, both a flat surface and a continuous-layer electrical resistivity that is equal to that of pure Ag films can only be achieved when Cu is deployed during the first 2.4nm of film deposition, during which morphological evolution is, primarily, governed by island coalescence. Our overall results highlight potential pathways for fabricating high-quality multifunctional metal contacts in a wide range of optoelectronic devices based on weakly-interacting oxides and van der Waals materials.
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| 5. |
- Jamnig, Andreas, et al.
(författare)
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The effect of kinetics on intrinsic stress generation and evolution in sputter-deposited films at conditions of high atomic mobility
- 2020
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 127:4
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Tidskriftsartikel (refereegranskat)abstract
- Vapor-based metal film growth at conditions that promote high atomic mobility is typically accompanied by compressive stress formation after completion of island coalescence, while an apparent stress relaxation is observed upon deposition interruption. Despite numerous experimental studies confirming these trends, the way by which growth kinetics affect postcoalescence stress magnitude and evolution is not well understood, in particular, for sputter-deposited films. In this work, we study in situ and in real-time stress evolution during sputter-deposition of Ag and Cu films on amorphous carbon. In order to probe different conditions with respect to growth kinetics, we vary the deposition rate F from 0:015 to 1:27 nm/s, and the substrate temperature T-S from 298 to 413 K. We find a general trend toward smaller compressive stress magnitudes with increasing T-S for both film/substrate systems. The stress-dependence on F is more complex: (i) for Ag, smaller compressive stress is observed when increasing F; (ii) while for Cu, a nonmonotonic evolution with F is seen, with a compressive stress maximum for F = 0.102 nm/s. Studies of postdeposition stress evolution show the occurrence of a tensile rise that becomes less pronounced with increasing T-S and decreasing F, whereas a faster tensile rise is seen by increasing F and T-S. We critically discuss these results in view of ex situ obtained film morphology which show that deposition-parameter-induced changes in film grain size and surface roughness are intimately linked with the stress evolution. (c) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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| 6. |
- Papaderakis, Athanasios, et al.
(författare)
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Ternary IrO2-Pt-Ni deposits prepared by galvanic replacement as bifunctional oxygen catalysts
- 2020
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : ELSEVIER SCIENCE SA. - 1572-6657. ; 877
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Tidskriftsartikel (refereegranskat)abstract
- Bifunctional oxygen catalysts with IrO2 and Pt active components have been prepared by means of galvanic partial replacement of Ni layers electrodeposited on glassy carbon substrates (Ni/GC). The resulting IrO2Pt(Ni)/GC electrodes have a homogeneous and compact morphology (SEM), while surface electrochemistry and spectroscopic measurements (EDS, XPS) confirm the ternary bulk structure (EDS: 56.39% Ir- 7.60% Pt - 36.01% Ni atomic ratio) and the existence of a IrO2-Pt thin skin on the outermost layers of the deposits (XPS: Ir+ Pt atomic ratio of 21.7). IrO2Pt (Ni)/GC electrodes were evaluated as bifunctional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reactions in acid, by means of steady-state current-potential measurements and linear sweep voltanunetry at a Rotating Disc Electrode (RDE) respectively. The OER overpotential required for a current density (per substrate geometric area) of 1 (eta(1)) and 10 mA cm(-2) (eta(10)) on the prepared electrodes was 235 and 302 my respectively, which is in the range of some typical thermally produced IrO2-based DSAs. Their intrinsic OER catalytic activity (as estimated by normalization of the recorded currents at an overpotential of 260 mV by the oxides charge) was found to be 0.29 mA mC(-1) comparable or better to other thermally produced IrO2 and Pt-IrO2 systems. Koutecky-Levich analysis shows that ORR proceeds on the ternary catalysts via the four electrons pathway. The overall ORR catalytic activity (0.4 mA cm(-2) at +0.8 V vs. SIIE) is found to be in the range of that recorded on nanoparticle catalysts, while a suppression of the intrinsic activity compared to bulk Pt is observed most probably due to the presence of IrO2, the latter being in line with similar non-alloyed Pt-IrO2 systems reported in the literature.
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| 7. |
- Pliatsikas, Nikolaos, et al.
(författare)
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Energetic bombardment and defect generation during magnetron-sputter-deposition of metal layers on graphene
- 2021
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 566
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we elucidate the interplay among energetic bombardment effects in magnetron sputtering and defect generation in two-dimensional (2D) materials. Using deposition of gold (Au) layers on single-layer graphene (SLG) as a model system, we study the effect of pressure-distance (pd) product during magnetron sputtering on the pristine SLG properties. Raman spectroscopy, complemented by X-ray photoelectron spectroscopy, shows that for pd = 8.2 Pa center dot cm, Au layer deposition causes defects in the SLG layer, which gradually diminish and eventually disappear with increasing pd to 82.5 Pa center dot cm. Stochastic and deterministic simulations of the sputtering process, the gas-phase transport, and the interaction of sputtered and plasma species with the substrate surface suggest that defects in SLG primarily emanate from ballistic damage caused by backscattered Ar atoms with energies above 100 eV. With increasing pd, and thereby gas-phase scattering, such high energy Ar species become thermalized and hence incapable of causing atomic displacements in the SLG layer. The overall results of our study suggest that control of backscattered Ar energy is a potential path toward enabling magnetron sputtering for fabrication of multifunctional metal contacts in devices founded upon 2D materials.
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| 8. |
- Pliatsikas, Nikolaos, et al.
(författare)
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Manipulation of thin silver film growth on weakly interacting silicon dioxide substrates using oxygen as a surfactant
- 2020
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 38:4
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Tidskriftsartikel (refereegranskat)abstract
- The authors study the morphological evolution of magnetron-sputtered thin silver (Ag) films that are deposited on weakly interacting silicon dioxide (SiO2) substrates in an oxygen-containing (O-2) gas atmosphere. In situ and real-time monitoring of electrically conductive layers, along with ex situ microstructural analyses, shows that the presence of O-2, throughout all film-formation stages, leads to a more pronounced two-dimensional (2D) morphology, smoother film surfaces, and larger continuous-layer electrical resistivities, as compared to Ag films grown in pure argon (Ar) ambient. In addition, the authors data demonstrate that 2D morphology can be promoted, without compromising the Ag-layer electrical conductivity, if O-2 is deployed with high temporal precision to target film formation stages before the formation of a percolated layer. Detailed real-space imaging of discontinuous films, augmented by in situ growth monitoring data, suggests that O-2 favors 2D morphology by affecting the kinetics of initial film-formation stages and most notably by decreasing the rate of island coalescence completion. Furthermore, compositional and bonding analyses show that O-2 does not change the chemical nature of the Ag layers and no atomic oxygen is detected in the films, i.e., O-2 acts as a surfactant. The overall results of this study are relevant for developing noninvasive surfactant-based strategies for manipulating noble-metal-layer growth on technologically relevant weakly interacting substrates, including graphene and other 2D crystals.
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| 9. |
- Shtepliuk, Ivan, et al.
(författare)
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Clustering and Morphology Evolution of Gold on Nanostructured Surfaces of Silicon Carbide: Implications for Catalysis and Sensing
- 2021
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 4:2, s. 1282-1293
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental understanding of the behavior of gold (Au) nanostructures deposited on functional surfaces is imperative to discover and leverage interface-related phenomena that can boost the efficiency of existing electronic devices in sensorics, catalysis, and spintronics. In the present work, Au layers with nominal thickness of 2 nm were sputter-deposited on graphenized SiC substrates represented by buffer layer (BuL)/4H-SiC and monolayer epitaxial graphene (MLG)/4H-SiC. Morphometric analysis by means of scanning electron microscopy shows that Au on BuL self-assembles in nearly round-shaped plasmonically active islands, while on MLG, a fractal growth of considerably larger and ramified islands is observed. To correlate the experimentally established differences in surface morphology on the two types of graphenized substrates with energetics and kinetics of Au nanostructure growth, the deposit-substrate interaction strength was studied using density functional theory (DFT) calculations, molecular dynamics simulations, and optical measurements. The theoretical considerations involve participation of Au clusters with different sizes and energetics at the initial stages of the metal nanostructure formation. The results indicate that gold exhibits a considerably stronger interaction with BuL than with MLG, which can be considered as a key aspect for explaining the experimentally observed morphological differences. From the statistical analysis of Raman spectra, indications of Au intercalation of MLG are discussed. The current research shows that, due to its unique surface chemistry, buffer layer has peculiar affinity to gold when compared to other atomically flat surfaces, which is beneficial for boosting high-performance catalytic and sensing technologies based on low-dimensional materials.
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| 10. |
- Shtepliuk, Ivan, et al.
(författare)
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Electrochemical performance of gold-decorated graphene electrodes integrated with SiC
- 2023
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 278
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigate the interface properties of gold (Au) decorated graphenized surfaces of 4H-SiC intended for electrochemical electrodes. These are fabricated using a two-step process: discontinuous Au layers with a nominal thickness of 2 nm are sputter-deposited onto 4H-SiC substrates with different graphenization extent—zero-layer graphene (ZLG) and monolayer epitaxial graphene) —followed by thermal annealing. By performing combined morphometric analysis, Raman mapping analysis, conductive atomic force microscopy, and electrochemical impedance spectroscopy measurements, we shed light on the relationship between physical processes (Au intercalation, particle re-shaping, and de-wetting) caused by thermal annealing and the intrinsic properties of graphenized SiC (vertical electron transport, charge-transfer properties, vibrational properties, and catalytic activity). We find that the impedance spectra of all considered structures exhibit two semicircles in the high and low frequency regions, which may be attributed to the graphene/ZLG/SiC (or Au/graphene/ZLG/SiC) and SiC/ZLG/graphene/electrolyte (or SiC/ZLG//Au/electrolyte) interfaces, respectively. An equivalent circuit model is proposed to estimate the interface carrier transfer parameters. This work provides an in-depth comprehension of the way by which the Au/2D carbon/SiC interaction strength influences the interface properties of heterostructures, which can be helpful for developing high performance catalytic and sensing devices.
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| 11. |
- Shtepliuk, Ivan, et al.
(författare)
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Exploring the Interface Landscape of Noble Metals on Epitaxial Graphene
- 2021
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley-VCH Verlagsgesellschaft. - 1862-6300 .- 1862-6319. ; 218:17
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the interaction between noble metals (NMs) and epitaxial graphene is essential for the design and fabrication of novel devices. Within this framework, a combined experimental and theoretical investigation of the effect of vapor-deposited NM (silver [Ag] and gold [Au]) nanostructures on the vibrational and electronic properties of monolayer epitaxial graphene (MLG) on 4H-SiC is presented. Large sets of Raman scattering data are analyzed using supervised classification and statistical methods. This analysis enables identification of the specific Raman fingerprints of Au- and Ag-decorated MLG originating from different dispersion interactions and charge transfer at the metal nanostructure/MLG interface. It is found that Raman scattering spectra of Au-decorated MLG feature a set of allowed phonon modes similar to those in pristine MLG, whereas the stronger Ag physisorption triggers an activation of defect-related phonon modes and electron doping of MLG. A principal component analysis (PCA) and linear discriminant analysis (LDA) are leveraged to highlight the features in phonon dispersion of MLG that emanate from the NM deposition process and to robustly classify large-scale Raman spectra of metal-decorated graphene. The present results can be advantageous for designing highly selective sensor arrays on MLG patches decorated with different metals.
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| 12. |
- Shtepliuk, Ivan, et al.
(författare)
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Interplay between thin silver films and epitaxial graphene
- 2020
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 381
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Tidskriftsartikel (refereegranskat)abstract
- Thin Ag films, with nominal thickness in the range 2 to 30 nm, are deposited using direct current magnetron sputtering and film morphology is studied by means of plan-view scanning electron microscopy. We find that for 2 mn nominal thickness the film surface consists of isolated circular nanoscale islands, which become interconnected as further material is deposited, leading to a continuous film at a nominal thickness of 30 nm. Our experimental findings are discussed in the context of the density functional theory results, which show that van der Waals forces dominate the interaction between Ag and epitaxial graphene. We also performed micro-Raman analysis and we find that the G and 2D modes of epitaxial graphene exhibit a red-shift upon Ag-layer deposition; which is interpreted as a result of charge transfer at the Ag/graphene interface. Moreover, we observed a pronounced enhancement of the G peak amplitude and area irrespective of the film nominal thickness and morphology, which we attribute to a combination of the charge transfer and plasmonic resonance effects. Our observations provide a critical information on the interaction between Ag and epitaxial graphene, which can be useful to design electronic and sensing devices based on Ag-epitaxial graphene hybrids.
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| 13. |
- Shtepliuk, Ivan, et al.
(författare)
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Manipulation of epitaxial graphene towards novel properties and applications
- 2020
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Ingår i: MATERIALS TODAY-PROCEEDINGS. - : ELSEVIER. - 2214-7853. ; , s. 37-45
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Konferensbidrag (refereegranskat)abstract
- The integration of epitaxial graphene on 4H-SiC with different metals may allow tunability of electronic and optical properties of graphene, enabling novel high-performance devices. Here we present a Raman spectroscopy study on epitaxial graphene decorated with electrodeposited Pb and Li adatoms and with magnetron sputtered 5 nm-thick Ag nano-island films. We find that the presence of metals on the epitaxial graphene surface generates defects and induces n-type doping, which is evidenced by the observation of the defect related Raman modes (namely D, D and D + G) and systematic red-shift of the main characteristic modes of graphene. In-depth statistical analysis of the Raman data before and after metal deposition complemented by density functional theory (DFT) calculations allowed to link the interaction strength between the three selected metals and graphene with the metal-induced changes in the vibrational/electronic properties of graphene. Large-area uniform electron doping of epitaxial graphene and surface-enhanced Raman scattering (SERS) effect are reached by room temperature deposition of Ag nano-island films. Very promising results have been obtained from graphene subjected to electrochemical intercalation by Li, which can serve as prerequisites of the construction of Li batteries. The strong interaction between Li or Pb with graphene implies the possibility to exploit the epitaxial graphene as an efficient material for energy storage or for heavy metal sensing, while predominant van der Waals interaction between Ag and graphene favors the formation of extremely thin silver coatings towards two-dimensional metal systems. The present results give better understanding of the nature of epitaxial graphene response to metal deposition and can be useful to design high-performance energy storage devices, optical sensors and heavy metal detection systems. (C) 2019 Elsevier Ltd. All rights reserved.
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| 14. |
- Shtepliuk, Ivan, et al.
(författare)
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Probing the uniformity of silver-doped epitaxial graphene by micro-Raman mapping
- 2020
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Ingår i: Physica. B, Condensed matter. - : ELSEVIER. - 0921-4526 .- 1873-2135. ; 580
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Tidskriftsartikel (refereegranskat)abstract
- We present a Raman spectroscopy study on epitaxial graphene decorated with thin Ag films (2-15 nm), which are deposited using magnetron sputtering. We find that the presence of Ag on the graphene surface induces doping, the uniformity and efficiency of which is determined by Ag nominal thickness. Deposition of Ag films with thicknesses up to 5 nm favors the effective electron transfer from Ag to epitaxial graphene. A significant redshift and broadening of the 2D peak are observed with increasing the Ag-layer thickness above 5 nm, which is indicative of large strain and doping fluctuations. We also observe a non-trivial linear growth of 2D/G peak intensity ratio with increasing D/G ratio for all Ag-decorated samples, which is explained by increase of peak amplitude due to surface enhanced Raman scattering and charged impurity-induced screening caused by the presence of Ag on the graphene surface.
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| 15. |
- Shtepliuk, Ivan, et al.
(författare)
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Silver nanoparticle array on weakly interacting epitaxial graphene substrate as catalyst for hydrogen evolution reaction under neutral conditions
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:15
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Tidskriftsartikel (refereegranskat)abstract
- The paucity of research on hydrogen evolution reaction (HER) under neutral conditions, which is a more sustainable way to produce H-2 compared to acidic and alkaline HER, encourages the development of efficient catalytic materials and devices and deeper investigation of the mechanisms behind neutral HER. We present an electrode concept for facilitating HER under neutral conditions. The concept entails the use of annealing-reshaped silver (Ag) nanoparticle array on monolayer epitaxial graphene (MEG) on 4H-SiC. Measurements of HER performance show more positive onset potential of the cathodic HER for Ag-decorated MEG compared to that for pristine MEG, indicating improved water dissociation at Ag/MEG electrodes. Complementary morphological characterization, absorption measurements, and Raman mapping analysis enable us to ascribe the enhanced catalytic performance of electrodes decorated with 2 nm thick annealed Ag on the synergetic effect originating from simultaneous water reduction on circular Ag nanoparticles of 31 nm in diameter and on compressively strained Ag-free graphene regions. The overall results pave the way toward development of stable van der Waals heterostructure electrodes with a tunable metal-carbon interaction for fast HER under neutral conditions. (C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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