| 1. |
- Butorin, S. M., et al.
(författare)
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Probing the Mn3+ sublattice in La0.5Ca0.5MnO3 by resonant inelastic soft X-ray scattering at the MnL2,3 edge
- 2002
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Ingår i: Surface review and letters. - : World Scientific. - 0218-625X .- 1793-6667. ; 9:2, s. 989-992
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Tidskriftsartikel (refereegranskat)abstract
- Resonant soft X-ray scattering spectra of a La0.5Ca0.5MnO3 thin film were measured at varying energies of the incident photon beam across Mn 2p thresholds. The data are analyzed within the framework of the Anderson impurity model and full multiplet theory. The scattering profiles of the film are reasonably well reproduced by model calculations for the Mn3+ system, in contrast to the absorption spectrum at the Mn L2,L3 edge for which the contribution of the Mn4+ sublattice is required to be taken into account. The obtained agreement between calculations and experiment indicates that in this case resonant inelastic scattering mainly probes the local electronic structure at the Mn3+ sites in the La0.5Ca0.5MnO3 film. In turn, Mn4+ sites mainly contribute to ordinary L-alpha,L-beta X-ray emission due to relaxations in the intermediate state of the spectroscopic process. Such a situation can occur when the system favors a phase separation rather than checkerboard charge ordering of Mn3+ and Mn4+ sites.
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| 2. |
- Cao, Wei, et al.
(författare)
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X-ray photoemission electron microscope determination of origins of room temperature ferromagnetism and photoluminescence in high co-content coxzn1-xo films.
- 2014
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Ingår i: Surface Review and Letters. - 0218-625X. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we reported on the X-ray photoemission electron microscope (XPEEM) determination of magnetic and luminescence origins for two CoxZn1-xO films. The cobalt fraction x of radio frequency co-sputtered samples were 0.86(2) and 0.92(2), respectively. Films were ferromagnetic and semiconductive. Unique narrow green color lines beside the ZnO intrinsic emissions were found with a decay time in microsecond range at room temperature. Origins of magnetic and luminescence properties were determined with XPEEM. The X-ray absorption near edge structure at the CoL3-edge denoted that Co was partially oxidized, and phase-contrast images together with chemical composition identification further proved that Co and CoO co-existed in the samples. The ferromagnetism was attributed to ferromagnetism of Co clusters partially canceled by the antiferromagnetism of its oxide, and the photoluminescence to bound exciton in ZnO nanoclusters and defect related centers of ZnO nanoclusters in a Co-rich matrix. Present results show possibilities for adjusting magnetic and luminescence properties of Co-ZnO compounds by changing the cobalt concentration.
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| 3. |
- Carabineiro, S A C, et al.
(författare)
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Resonant photoemission of N2O on Ir(110)
- 2004
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Ingår i: Surface Review and Letters. - 0218-625X. ; 11:4-5, s. 385-389
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of N2O on Ir(110) was investigated with high-resolution resonant photoemission at 135 K. The results obtained show evidence of molecular adsorption of N2O, along with some dissociation. It is found that the nitrogen photoemission spectra measured at the terminal and central nitrogen energy positions of the N2O/Ir(110) system are equivalent to those of N2O in the gas phase. In contrast, the oxygen spectrum shows little resemblance to the gas phase oxygen spectrum of N2O. In the nitrogen resonant photoemission spectra one can only discover resonant behavior with constant binding energy peaks. In contrast, the oxygen resonant photoemission spectra shows dominantly Auger behavior with peaks at constant kinetic energies. Both observations reveal that the oxygen is bonded to the Ir surface. A systematic study as a function of coverage and temperature and a comparison with other surfaces differing in structure and composition is needed to understand the variations in the adsorption behavior of N2O On metal surfaces.
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| 4. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Structure changes for Cu(111)/Li observed via discrete quantum well states
- 1997
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Ingår i: Surface Review and Letters. - 0218-625X. ; 4:6, s. 1233-1237
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Tidskriftsartikel (refereegranskat)abstract
- Via photoemission in the near UV from discrete quantum well states, four different types of atom rearrangements are observed for Cu(111)/Li. In the monolayer range a gradual energy shift reflects a gradual compression of the Li layer as more atoms are adsorbed. The onset of Li substitution and formation of a (2×2) structure when, at RT, monolayer Li coverage is exceeded is monitored via the appearance of a quantum well state characteristic of the new phase. A small energy shift indicates that, if it is cooled (170 K), the new structure is unstable with respect to Li adsorption. Finally, an energy downshift with increasing coverage observed for a state characteristic of 2 ML Li is ascribed to an increasing area for one-atomic-layer-high islands formed by Li atoms on top of the first full layer.
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| 5. |
- Johansson, Leif, et al.
(författare)
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Changes induced in the surface electronic structure of Be(0001) after Si adsorption
- 2002
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Ingår i: Surface Review and Letters. - 0218-625X. ; 9:2, s. 687-691
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Konferensbidrag (refereegranskat)abstract
- A study of effects induced in the Be 1s core level spectrum and in the surface band structure after Si adsorption on Be(0001) is reported. The changes in the Be 1s spectrum are quite dramatic. The number of resolvable surface components and the magnitude of the shifts do decrease and the relative intensities of the shifted components are drastically different compared to the clean surface. The surface band structure is also strongly affected after Si adsorption and annealing. At G the surface state is found to move down from 2.8 to 4.1 eV. The band also splits at around 0.5 Å-1 along both the G-K and G-M directions. At M and beyond K only one surface state is observed in the band gap instead of the two for the clean surface. Our findings indicate that a fairly small amount of Si in the outer atomic layers strongly modifies the electronic properties of these layers.
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| 6. |
- Johansson, Leif, et al.
(författare)
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The surface band structure of Li/Be(10(1)over-bar0)
- 2002
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Ingår i: Surface review and letters. - 0218-625X. ; 9:3-4, s. 1493-1496
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Tidskriftsartikel (refereegranskat)abstract
- A photoemision study of the surface states on Be(10 (1) over bar0) after Li adsorption at room temperature is reported. The surface band structure was mapped along four high symmetry directions of the SBZ. Fairly large shifts in the surface band locations were obtained but all surface states observed experimentally after Li adsorption were found to correspond to Be-derived states and no Li-derived surface states could be identified. The surface state bands located close to the Fermi level (E-F) were found to be affected the most and it is suggested that one surface state band which on the clean surface is located above E-F is pulled down below E-F after Li adsorption.
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| 7. |
- Kikas, A, et al.
(författare)
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NaK photoabsorption and resonant KLL Auger spectra in naf and NaCl
- 2002
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Ingår i: Surface Review and Letters. - 0218-625X. ; 9:2, s. 1303-1308
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Tidskriftsartikel (refereegranskat)abstract
- The nature of Na Is photoabsorption in NaF and NaCl is investigated using the resonant Auger decay of Na Is core excitations. The appearance of new peaks in Auger spectra, when the energy of excitation coincides with the photoabsorption thresholds, shows that the core excitons are created in the threshold region of the Na 1s photoabsorption spectrum. The core excitons around 1074.2 eV originate from the dipole-forbidden 1s(-1)3s final state, the population of which is made possible by the symmetry disruption at the photoabsorption site. Another core exciton, excited at photon energies of 1076.8 eV in NaF and 1076.3 eV in NaCl, originates from 1s(-1)3p states similar to atoms of Ne and Na. Resonant Auger spectra show also that in NaCl the first sharp photoabsorption maximum at 1076.6 eV has only partially excitonic character.
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| 8. |
- Lu, J. -L., et al.
(författare)
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Structure, thermal stability, and CO adsorption properties of Pd nanoparticles supported on an ultra-thin SiO2 film
- 2007
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Ingår i: Surface review and letters. - 0218-625X. ; 14:5, s. 927-934
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Tidskriftsartikel (refereegranskat)abstract
- Nucleation, growth, and thermal stability of Pd particles vapor-deposited on an ultra-thin crystalline silica film grown on Mo(112) have been studied by scanning tunneling microscopy, X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and temperature-programmed desorption of CO. No preferential nucleation of Pd on the silica film is found at room temperature deposition: the hemispherical Pd nanoparticles are homogenously dispersed on the support at all coverages studied (0.01-1ML(mono layer)). The Pd particles are resistant toward sintering up to 700K as judged by STM; however, CO adsorption studies have revealed surface chemical modification at temperatures as low as 550K. Strong morphological changes are observed above 800K (ultimately resulting in elongated rectangular islands at similar to 1000 K), which is accompanied by strong alterations of CO adsorption properties. The results are rationalized in terms of Pd and Mo substrate interdiffusion at elevated temperatures, while the silica film basically preserves its structure.
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| 9. |
- Lushchik, A, et al.
(författare)
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Control of excitonic and electron-hole processes in wide-gap crystals by means of elastic uniaxial stress
- 2002
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Ingår i: Surface Review and Letters. - 0218-625X. ; 9:1, s. 299-304
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Tidskriftsartikel (refereegranskat)abstract
- The time-resolved emission spectra and the excitation spectra of the main emissions have been measured for the first time in stressed and unstressed RbI crystals using synchrotron radiation of 10-30 eV at 8 K. It has been shown that the applied elastic uniaxial stress (EUS) offers promise for the separation of the elementary multiplication mechanisms of electronic excitations. A different influence of EUS on the self-trapping of excitons or holes at 8 K has been discussed. The mean free path of free excitons decreases, while that of valence holes increases in a stressed RbI crystal.
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| 10. |
- Rius, J., et al.
(författare)
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Selective fragmentation of valence- and core-electron-excited CD4 and SF6 molecules
- 2002
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Ingår i: Surface review and letters. - 0218-625X. ; 9:1, s. 117-123
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Tidskriftsartikel (refereegranskat)abstract
- Electron-ion coincidence measurements with energy-resolved electrons are a powerful tool in studies of molecular fragmentation processes, since fragmentation from a specific doorway state can be monitored while the remaining reactions are discriminated. Presently, we have applied this technique in measurements of coincidence spectra of the CD4 and SF6 molecules after valence and core electron excitation. The newly constructed energy-resolved electron-ion coincidence station developed for this project has been used. Our results on CD4 are the first demonstration of a correlation between vibrations and molecular dissociation observed in this molecule. The SF6 spectra reveal strong selectivity in dissociation following distinct electronic states of the molecule. This selectivity reflects the bonding properties of the potential surfaces involved in the studied processes. The obtained results exemplify the potential of the new multicoincidence station used in this work.
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