| 1. |
- Aristov, Victor Yu., et al.
(författare)
-
Graphene Synthesis on Cubic SiC/Si Wafers. Perspectives for Mass Production of Graphene-Based Electronic Devices
- 2010
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:3, s. 992-995
-
Tidskriftsartikel (refereegranskat)abstract
- The outstanding properties of graphene, a single graphite layer, render it a top candidate for substituting silicon in future electronic devices, The so far exploited synthesis approaches, however, require conditions typically achieved in specialized laboratories and result in graphene sheets whose electronic properties are often altered by interactions with substrate materials. The development of graphene-based technologies requires an economical fabrication method compatible with mass production. Here we demonstrate for the fist Lime the feasibility of graphene synthesis on commercially available cubic SiC/Si substrates of >300 mm in diameter, which result in graphene flakes electronically decoupled from the substrate. After optimization of the preparation procedure, the proposed synthesis method can represent a further big step toward graphene-based electronic technologies.
|
|
| 2. |
- Cavar, Elizabeta, et al.
(författare)
-
A single h-BN layer on Pt(111)
- 2008
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:9, s. 1722-1726
-
Tidskriftsartikel (refereegranskat)abstract
- The structure and formation of an ultrathin hexagonal boron nitride (h-BN) film on Pt(111) has been studied by a combination of scanning tunneling microscopy, low energy electron diffraction, low energy electron microscopy, X-ray absorption and high resolution core level spectroscopy. The study shows that a single boron nitride layer is formed on Pt(111), resulting in a coincidence structure. High resolution scanning tunneling microscopy (STM) images of the h-BN ultrathin film display only one of the atomic species in the unit cell. Probing the boron and nitrogen related local density of states by near edge X-ray absorption fine structure measurements we conclude that the nitrogen sublattice is visible in STM images. The growth of the single hexagonal boron nitride layer by vapourized borazine in the pressure range of 1 x 10(-6)-1 x 10(-8) at 800 degrees C is further studied by low energy electron microscopy, and reveals that the number of nucleation sites and the perfection of the growth is strongly pressure dependent. A model for the single, hexagonal, boron nitride layer on Pt(111) is proposed.
|
|
| 3. |
- Krasnikov, Sergey A., et al.
(författare)
-
Formation of extended covalently bonded Ni porphyrin networks on the Au(111) surface
- 2011
-
Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 4:4, s. 376-384
-
Tidskriftsartikel (refereegranskat)abstract
- The growth and ordering of {5,10,15,20-tetrakis(4-bromophenyl)porphyrinato}nickel(II) (NiTBrPP) molecules on the Au(111) surface have been investigated using scanning tunnelling microscopy, X-ray absorption, core-level photoemission, and microbeam low-energy electron diffraction. When deposited onto the substrate at room temperature, the NiTBrPP forms a well-ordered close-packed molecular layer in which the molecules have a flat orientation with the porphyrin macrocycle plane lying parallel to the substrate. Annealing of the NiTBrPP layer on the Au(111) surface at 525 K leads to dissociation of bromine from the porphyrin followed by the formation of covalent bonds between the phenyl substituents of the porphyrin. This results in the formation of continuous covalently bonded porphyrin networks, which are stable up to 800 K and can be recovered after exposure to ambient conditions. By controlling the experimental conditions, a robust, extended porphyrin network can be prepared on the Au(111) surface that has many potential applications such as protective coatings, in sensing or as a host structure for molecules and clusters.
|
|
| 4. |
- Ng, May Ling, et al.
(författare)
-
Effect of substrate nanopatterning on the growth and structure of pentacene films
- 2010
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:11, s. 115449-
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of modulating the structure of thin pentacene (C22H14) films by a nanopatterned inert substrate, known as hexagonal boron nitride nanomesh, is reported. Films of different thickness are grown and characterized by x-ray absorption, core-level photoemission, low-energy electron microscopy, microbeam low-energy electron diffraction, and scanning tunneling microscopy. Initially the pentacene molecules adsorb with the molecular plane lying flat on the substrate but they tend to flip up with increasing coverage, forming well-ordered monolayer-thick islands of upright molecules with low nucleation density. The herringbone packing of the upright molecules is observed with scanning tunneling microscopy. The electronic structure of the adsorbed molecules is very similar to that of the gas-phase pentacene, implying weak interaction with the substrate and between the molecules. The periodic corrugation of the substrate surface causes the monolayer of upright pentacene molecules to form two different coincidence superstructures. The lattice parameters of the pentacene unit cell for each of these two substrate-induced domains are determined from the microdiffraction patterns. Both domains can occur in several equivalent configurations, thus resulting in a number of twins with a typical size of a few micrometers. The first monolayer grows in a layer-by-layer mode until it is completed while the second monolayer forms diffusion-limited fractal islands. Upon annealing, the pentacene films are thermally stable up to approximately 80 degrees C and thereafter the onset of desorption is observed.
|
|
| 5. |
- Niu, Yuran, et al.
(författare)
-
MAXPEEM : a spectromicroscopy beamline at MAX IV laboratory
- 2023
-
Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 30:Pt 2, s. 468-478
-
Tidskriftsartikel (refereegranskat)abstract
- MAXPEEM, a dedicated photoemission electron microscopy beamline at MAX IV Laboratory, houses a state-of-the-art aberration-corrected spectroscopic photoemission and low-energy electron microscope (AC-SPELEEM). This powerful instrument offers a wide range of complementary techniques providing structural, chemical and magnetic sensitivities with a single-digit nanometre spatial resolution. The beamline can deliver a high photon flux of ≥1015 photons s−1 (0.1% bandwidth)−1 in the range 30–1200 eV with full control of the polarization from an elliptically polarized undulator. The microscope has several features which make it unique from similar instruments. The X-rays from the synchrotron pass through the first beam separator and impinge the surface at normal incidence. The microscope is equipped with an energy analyzer and an aberration corrector which improves both the resolution and the transmission compared with standard microscopes. A new fiber-coupled CMOS camera features an improved modulation transfer function, dynamic range and signal-to-noise ratio compared with the traditional MCP-CCD detection system.
|
|
| 6. |
- Vinogradov, Nikolay, et al.
(författare)
-
Formation and Structure of Graphene Waves on Fe(110)
- 2012
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 109:2
-
Tidskriftsartikel (refereegranskat)abstract
- A very rich Fe-C phase diagram makes the formation of graphene on iron surfaces a challenging task. Here we demonstrate that the growth of graphene on epitaxial iron films can be realized by chemical vapor deposition at relatively low temperatures, and that the formation of carbides can be avoided in excess of the carbon-containing precursors. The resulting graphene monolayer creates a novel periodically corrugated pattern on Fe(110). Using low-energy electron microscopy and scanning tunneling microscopy, we show that it is modulated in one dimension forming long waves with a period of similar to 4 nm parallel to the [001] direction of the substrate, with an additional height modulation along the wave crests. The observed topography of the graphene/Fe superstructure is well reproduced by density functional theory calculations, and found to result from a unique combination of the lattice mismatch and strong interfacial interaction, as probed by core-level photoemission and x-ray absorption spectroscopy.
|
|
| 7. |
- Vinogradov, Nikolay, et al.
(författare)
-
Hole doping of graphene supported on Ir(111) by AlBr3
- 2013
-
Ingår i: Applied Physics Letters. - : American Chemical Society (ACS). - 0003-6951 .- 1077-3118. ; 102:6, s. 061601-
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter we report an easy and tenable way to tune the type of charge carriers in graphene, using a buried layer of AlBr3 and its derivatives on the graphene/Ir(111) interface. Upon the deposition of AlBr3 on graphene/Ir(111) and subsequent temperature-assisted intercalation of graphene/Ir(111) with atomic Br and AlBr3, pronounced hole doping of graphene is observed. The evolution of the graphene/Br-AlBr3/Ir(111) system at different stages of intercalation has been investigated by means of microbeam low-energy electron microscopy/electron diffraction, core-level photoelectron spectroscopy and angle-resolved photoelectron spectroscopy.
|
|
| 8. |
- Vinogradov, Nikolay, et al.
(författare)
-
One-Dimensional Corrugation of the h-BN Monolayer on Fe(110)
- 2012
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:3, s. 1775-1781
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a new nanopatterned structure represented by a single atomic layer of hexagonal boron nitride (h-BN) forming long periodic waves on the Fe(110) surface. The growth process and the structure of this system are characterized by X-ray absorption (XAS), core-level photo-emission spectroscopy (CL PES), low-energy electron microscopy (LEEM), microbeam low-energy electron diffraction (mu LEED), and scanning tunneling microscopy (STM). The h-BN monolayer on Fe(110) is periodically corrugated in a wavy fashion with an astonishing degree of long-range order, periodicity of 2.6 nm, and the corrugation amplitude of A. The wavy pattern results from a strong chemical bonding between h-BN and Fe in combination with a lattice mismatch in either [(1) over bar 11] or [1 (1) over bar1] direction of the Fe(110) surface. Two primary orientations of h-BN on Fe(110) can be observed corresponding to the possible directions of lattice match between h-BN and Fe(110), with approximately equal area of the boron nitride domains of each orientation.
|
|
| 9. |
- Abb, Marcel J.S., et al.
(författare)
-
Thermal Stability of Single-Crystalline IrO2(110) Layers : Spectroscopic and Adsorption Studies
- 2020
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:28, s. 15324-15336
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of ultrathin single-crystalline IrO2(110) films with the gas phase proceeds via the coordinatively unsaturated sites (cus), in particular Ircus, the undercoordinated oxygen species on-top O (Oot) that are coordinated to Ircus, and bridging O (Obr). With the combination of different experimental techniques, such as thermal desorption spectroscopy, scanning tunneling microscopy (STM), high-resolution core-level spectroscopy (HRCLS), infrared spectroscopy, and first-principles studies employing density functional theory calculations, we are able to elucidate surface properties of single-crystalline IrO2(110). We provide spectroscopic fingerprints of the active surface sites of IrO2(110). The freshly prepared IrO2(110) surface is virtually inactive toward gas-phase molecules. The IrO2(110) surface needs to be activated by annealing to 500-600 K under ultrahigh vacuum (UHV) conditions. In the activation step, Ircus sites are liberated from on-top oxygen (Oot) and monoatomic Ir metal islands are formed on the surface, leading to the formation of a bifunctional model catalyst. Vacant Ircus sites of IrO2(110) allow for strong interaction and accommodation of molecules from the gas phase. For instance, CO can adsorb atop on Ircus and water forms a strongly bound water layer on the activated IrO2(110) surface. Single-crystalline IrO2(110) is thermally not very stable although chemically stable. Chemical reduction of IrO2(110) by extensive CO exposure at 473 K is not observed, which is in contrast to the prototypical RuO2(110) system.
|
|
| 10. |
- Ahmad, Y., et al.
(författare)
-
NMR and NEXAFS Study of Various Graphite Fluorides
- 2013
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:26, s. 13564-13572
-
Tidskriftsartikel (refereegranskat)abstract
- Graphite fluorides with different structural types (CyF)(n) (y = 2.5, 2, and 1) and room temperature graphite fluorides were studied by solid state,NMR and NEXAFS. Data extracted from those two techniques are complementary, providing information about the C-F bonding and the hybridization character of the carbon atom valence states. The comparison of data obtained by different methods such as NMR, Raman, and X-ray absorption leads to similar conclusions regarding the chemical bonding in fluorographites. Several major configurations of fluorinated graphites are discussed, that is, planar sheets with mainly sp(2) hybridization in room temperature graphite fluorides and corrugated sheets with sp(3) hybridization in covalent high temperature graphite fluoride. Different references such as highly oriented pyrolytic graphite (HOPG), graphitized carbon nanodiscs (graph-CNDs) and nanodiamonds (NDs) have also been investigated for comparison.
|
|
| 11. |
- Appelfeller, Stephan, et al.
(författare)
-
Self-organized formation of unidirectional and quasi-one-dimensional metallic Tb silicide nanowires on Si(110)
- 2023
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 607
-
Tidskriftsartikel (refereegranskat)abstract
- Terbium induced nanostructures on Si(110) and their growth are thoroughly characterized by low energy electron diffraction, scanning tunneling microscopy and spectroscopy, core-level and valence band photoelectron spectroscopy, and angle-resolved photoelectron spectroscopy. For low Tb coverage, a wetting layer forms with its surface fraction continuously decreasing with increasing Tb coverage in favor of the formation of unidirectional Tb silicide nanowires. These nanowires show high aspect ratios for high annealing temperatures or on substrates already containing Tb in the bulk. Both wetting layer and nanowires are stable for temperatures up to 750°C. In contrast to the nanowires, the wetting layer is characterized by a band gap. Thus, the metallic nanowires, which show a quasi-one-dimensional electronic band structure, are embedded in a semiconducting surrounding of wetting layer and substrate, insulating the nanowires from each other.
|
|
| 12. |
- Aristov, V. Yu., et al.
(författare)
-
Electronic properties of potassium-doped FePc
- 2010
-
Ingår i: Organic Electronics. - : Elsevier BV. - 1566-1199. ; 11:8, s. 1461-1468
-
Tidskriftsartikel (refereegranskat)abstract
- The evolution of electronic structure of the organic semiconductor iron-phthalocyanine with potassium doping has been studied by means of photoemission spectroscopy, near-edge X-ray absorption fine structure and density functional theory (DFT) calculations. The DFT study and detailed analysis of the core-level spectra permit us to suggest possible lattice sites for the potassium ions. The data disclosed filling of the lowest unoccupied molecular orbital upon doping and associated changes of the core level absorption spectra. None of the films prepared in our studies showed a finite electronic density of states at the Fermi level. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 13. |
- Biasin, Pietro, et al.
(författare)
-
From borophene polymorphs towards a single honeycomb borophane phase : reduction of hexagonal boron layers on Al(111)
- 2023
-
Ingår i: Nanoscale. - 2040-3364. ; 15:45, s. 18407-18414
-
Tidskriftsartikel (refereegranskat)abstract
- The recent interest in characterizing 2D boron polymorphs has led to claims of the first stabilization of a honeycomb phase with conical Dirac-like electron dispersion. However, the synthesis of chemically stable, single, and homogeneous 2D boron phases still represents a significant experimental challenge. This is ascribed to the intrinsic boron electronic configuration that, at variance with carbon, leads to the formation of multi-center covalent bonds. External charge compensation by substrate-induced doping can steer the geometry of the layer, both in the buckling and in the density of B vacancies, like in the case of the recently achieved stabilization of honeycomb boron layers on Al(111). The price to pay is however a strong boron-support interaction, resulting in general in a limiting kinetic hindrance with respect to the synthesis of homogenous single phases. In the specific case of Al(111) an AlB2 layer is known to form at the surface, quite far from a desirable quasi-freestanding borophene monolayer and at variance with graphene, which can be easily synthesized in an almost freestanding configuration e.g. on Ir(111). We provide here evidence for the (reversible) formation of well-ordered honeycomb borophane upon hydrogenation of the honeycomb boron phase on Al(111).
|
|
| 14. |
- Biasin, Pietro, et al.
(författare)
-
Growth and Redox Properties of Boron on Al(111) : Competing Affinities in the Case of Honeycomb AlB2
-
Ingår i: ACS Nano. - 1936-0851.
-
Tidskriftsartikel (refereegranskat)abstract
- The complexity of the geometric and electronic structure of boron allotropes is associated with the multicentric bonding character and the consequent B polymorphism. When growth is limited to two-dimensions (2D), the structural and electronic confinement yields the borophenes family, where the interaction with the templating substrate actually determines the stability of inequivalent boron phases. We report here a detailed study of the growth of the honeycomb AlB2 phase on Al(111), followed by an investigation of its oxidation and reduction properties. By means of a combined experimental and theoretical approach, we show that the structure of the B/Al interface is affected by the complex interplay between B, Al, and common reactive agents like oxygen and hydrogen. While kinetic effects associated with diffusion and strain release influence the AlB2 growth in vacuo, Al, B, O, and H chemical affinities determine its redox behavior. Reduction with atomic hydrogen involves the B layer and yields an ordered honeycomb borophane H/AlB2 phase. Instead, oxidation takes place at the Al interface, giving origin to buried and 1D surface aluminum oxide phases.
|
|
| 15. |
- Brzhezinskaya, M. M., et al.
(författare)
-
Electronic structure of fluorinated multiwalled carbon nanotubes studied using x-ray absorption and photoelectron spectroscopy
- 2009
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 79:15
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes (MWCNTs) with different fluorine contents (10-55 wt %) and reference compounds (highly oriented pyrolytic graphite crystals and "white" graphite fluoride) using x-ray absorption and photoelectron spectroscopy at C 1s and F 1s thresholds. Measurements were performed at BESSY II (Berlin, Germany) and MAX-laboratory (Lund, Sweden). The analysis of the soft x-ray absorption and photoelectron spectra points to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. It was established that within the probing depth (similar to 15 nm) of carbon nanotubes, the process of fluorination runs uniformly and does not depend on the fluorine concentration. In this case, fluorine atoms interact with MWCNTs through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton (phase 1) and this bonding is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp(2)) to tetrahedral (sp(3)) hybridization and by a large electron transfer between carbon an fluorine atoms. In the MWCNT near-surface region the second fluorine-carbon phase with weak electron transfer is formed; it is located mainly within two or three upper graphene monolayers, and its contribution becomes much poorer as the probing depth of fluorinated multiwalled carbon nanotubes (F-MWCNTs) increases. The defluorination process of F-MWCNTs on thermal annealing has been investigated. The conclusion has been made that F-MWCNT defluorination without destruction of graphene layers is possible.
|
|
| 16. |
- Dedkov, Y S, et al.
(författare)
-
Correlations in the electronic structure of half-metallic ferromagnetic CrO2 films: An x-ray absorption and resonant photoemission spectroscopy study
- 2005
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:6
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of high-quality CrO2(100) films was investigated by means of x-ray absorption and resonant photoemission spectroscopy at the 2p-3d excitation threshold. The obtained binding energy of the occupied Cr 3d states is in agreement with the results predicted within the local spin-density approximation using the dynamical mean-field theory [L. Craco , Phys. Rev. Lett. 90, 237203 (2003)]. The reported data support a model of CrO2 as a half-metallic ferromagnet with strong electron-correlation effects.
|
|
| 17. |
- Dedkov, Yu. S., et al.
(författare)
-
Spin-resolved photoemission of a ferromagnetic Mn5Ge3(0001) epilayer on Ge(111)
- 2009
-
Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 105:7
-
Tidskriftsartikel (refereegranskat)abstract
- Here we present a study of the electronic structure of epitaxial ferromagnetic Mn5Ge3(0001) films on Ge(111) by means of x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, and spin-resolved photoelectron spectroscopy. Spin-polarization (P) value of +(15 +/- 5)% at the Fermi energy (E-F) is measured with a photon energy of h nu = 21.2 eV. Our findings are in contrast to recent band structure calculations, predicting P=-41% at E-F for the ferromagnetic bulk Mn5Ge3. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3103336]
|
|
| 18. |
|
|
| 19. |
- Doyle, Catherine M., et al.
(författare)
-
Ni-Cu ion exchange observed for Ni(II)-porphyrins on Cu(111)
- 2014
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 50:26, s. 3447-3449
-
Tidskriftsartikel (refereegranskat)abstract
- A Ni-Cu ion exchange has been observed for (5,15-dibromo-10,20-diphenylporphyrinato)nickel(II) (NiDBrDPP) and (5,10,15,20-tetrakis-(4-bromophenyl) porphyrinato)nickel(II) (NiTBrPP) on Cu(111). The ion exchange proceeds at a faster rate for the NiDBrDPP/Cu(111) system compared to NiTBrPP/Cu(111). This is explained in terms of the macrocycle-substrate distance and the distortions
|
|
| 20. |
- Doyle, Catherine M., et al.
(författare)
-
Surface Mediated Synthesis of 2D Covalent Organic Networks : 1,3,5-Tris(4-bromophenyl)benzene on Au(111)
- 2019
-
Ingår i: Physica Status Solidi (B) Basic Research. - : Wiley. - 0370-1972. ; 256:2
-
Tidskriftsartikel (refereegranskat)abstract
- Covalent organic networks derived from surface-mediated self-assembly of 1,3,5-tris(4-bromophenyl)benzene into two-dimensional networks on Au(111) have been studied by scanning tunneling microscopy (STM) and by X-ray spectroscopic methods. High resolution soft X-ray photoemission spectroscopy (SXPS) using synchrotron radiation have been used to study the formation of the 1,3,5-tris(4-bromophenyl)benzene-derived 2D networks by observing temperature-dependent C 1s and Br 3d core level XPS spectra. X-ray absorption (XA) measurements of the formation of these 2D networks have been obtained at the C K-edge where their temperature and angular dependence are examined. The results of these XPS and XA spectroscopic measurements are compared to detailed ab initio electronic structure calculations of 1,3,5-tris(4-bromophenyl)benzene molecules to aid the interpretation of the features of these spectra.
|
|
| 21. |
- Eidhagen, Josefin, et al.
(författare)
-
Synchrotron XPS and Electrochemical Study of Aging Effect on Passive Film of Ni Alloys
- 2023
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:2, s. 021506-
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate aging effect on the passive film of Ni23Cr15Mo and Ni22Cr9Mo3Nb, synchrotron-based X-ray photoelectron spectroscopy (XPS) was used to analyze the structure and composition of the air-formed passive film on the alloys. The corrosion resistance of the two Ni alloys in 1 M NaCl solution was evaluated with electrochemical cyclic polarization measurement. The synchrotron XPS measurement provided detailed information about chemical states of alloying elements in the passive film, showing that the passive film consists of an inner oxide layer and an outer hydroxide layer. The XPS data allowed precise determination of the chemical composition and the thickness of the outer hydroxide layer, the inner oxide layer, and the underlying subsurface alloy layer. The Cr-oxide in the inner layer grows thicker with aging time, leading to Cr-depletion in the subsurface region. Mo and Nb in the alloy form mixed oxides and hydroxides, and aging in air leads to transformation of the lower valence oxides into higher valence oxides. The freshly formed oxide film exhibits similar barrier properties as the aged oxide film. The stability of the passive film formed on Ni22Cr9Mo3Nb seems to be better than that on Ni23Cr15Mo.
|
|
| 22. |
- Generaloy, Alexander V., et al.
(författare)
-
Evolution of CuI/Graphene/Ni(111) System during Vacuum Annealing
- 2015
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:22, s. 12434-12444
-
Tidskriftsartikel (refereegranskat)abstract
- We present a combined core-level spectroscopy and low-energy electron diffraction study of the evolution of thin CuI layers on graphene/Ni(111) during annealing. It has been found that the annealing of the CuI/graphene/Ni(111) system up to 160 degrees C results in the formation of an ordered CuI overlayer with a (root 3 x root 3) R30 degrees structure on top of the graphene surface. At annealing temperatures of about 180 degrees C or higher, the CuI overlayer decomposes with a simultaneous intercalation of Cu and I atoms underneath the graphene monolayer on Ni(111). Nearly complete intercalation of graphene by Cu and I atoms can be achieved by deposition of about 20 angstrom of CuI, followed by annealing at 200 degrees C. The intercalated graphene layer is p-doped due to interfacial iodine atoms.
|
|
| 23. |
- Gericke, Sabrina M., et al.
(författare)
-
Effect of Different In 2 O 3 (111) Surface Terminations on CO 2 Adsorption
- 2023
-
Ingår i: ACS Applied Materials & Interfaces. - 1944-8252 .- 1944-8244. ; 15:38, s. 45367-45377
-
Tidskriftsartikel (refereegranskat)abstract
- In2O3-based catalysts have shown high activity and selectivity for CO2 hydrogenation to methanol; however, the origin of the high performance of In2O3 is still unclear. To elucidate the initial steps of CO2 hydrogenation over In2O3, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO2 on the In2O3(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO2 adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO2 is hindered by hydroxyl groups on the hydroxylated surface.
|
|
| 24. |
- Gericke, Sabrina M., et al.
(författare)
-
Effect of Different In2O3(111) Surface Terminations on CO2 Adsorption
- 2023
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 15:38, s. 45367-45377
-
Tidskriftsartikel (refereegranskat)abstract
- In2O3-based catalysts have shown high activity and selectivity for CO2 hydrogenation to methanol; however, the origin of the high performance of In2O3 is still unclear. To elucidate the initial steps of CO2 hydrogenation over In2O3, we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO2 on the In2O3(111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO2 adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO2 is hindered by hydroxyl groups on the hydroxylated surface.
|
|
| 25. |
- Guo, Yefei, et al.
(författare)
-
Electronic Correlations in Multiferroic Van der Waals CuCrP2S6 : Insights from X-ray Spectroscopy and DFT
-
Ingår i: Journal of Physical Chemistry C. - 1932-7447. ; 128:18, s. 7830-7839
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of high-quality van der Waals multiferroic CuCrP2S6 crystals was investigated by applying photoelectron spectroscopy methods in combination with DFT analysis. Using X-ray photoelectron and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Cu L2,3 and Cr L2,3 absorption edges, we determine the charge states of ions in the studied compound. Analyzing the systematic NEXAFS and resonant photoelectron spectroscopy data at the Cu/Cr L2,3 absorption edges allowed us to assign the CuCrP2S6 material to a Mott-Hubbard type insulator and identify different Auger-decay channels (participator vs spectator) during absorption and autoionization processes. Spectroscopic and theoretical data obtained for CuCrP2S6 are very important for the detailed understanding of the electronic structure and electron-correlations phenomena in different layered materials, which will drive their further applications in different areas, like electronics, spintronics, sensing, and catalysis.
|
|
