| 1. |
- Tsetlin, M. B., et al.
(author)
-
Spatial Structures Formed during High-Temperature Vacuum Annealing of Diamond-Like Film Deposited on a Silicon Substrate
- 2009
-
In: Journal Of Surface Investigation-X-Ray Synchrotron And Neutron Techniques. - 1027-4510. ; 3:5, s. 752-755
-
Journal article (peer-reviewed)abstract
- The process of an ultrahigh vacuum annealing of a diamond-like carbon film deposited on a silicon substrate has been studied in situ using a photoemission microscope mounted at the MAX-lab synchrotron's radiation source. After the annealing the film was examined ex situ using an atomic force microscope. It is revealed that the graphitization of the film occurs and round formations of several microns in size with a core of similar to 0.2 mu m in size appear on its surface at the temperature exceeding 1000 degrees C. Photoemission images of these formations have shown the presence of silicon on their surface. Apparently, the interaction between the carbon film and silicon substrate begins in the middle of the formation and spreads to the adjacent region at the following stage.
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| 2. |
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| 3. |
- Bertolo, M, et al.
(author)
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Photoemission spectromicroscopy study of a Bi2Sr2CaCu2O8+delta single crystal
- 2003
-
In: Journal de Physique IV - Proceedings. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 104, s. 487-490
-
Conference paper (peer-reviewed)abstract
- Using photoemission spectromicroscopy at sub-micron lateral resolution we studied two superconductor systems of high fundamental and practical importance, such as Bi2Sr2CaCu2O8+delta and MgB2. Our findings demonstrate the importance of considering, for this class of systems, the possible presence of spatial inhomogeneities in interpreting the results of conventional photoemission experiments, which typically probe an area of the order of 1 mm(2). In particular, in the case of MgB2, we report a measured density of states directly comparable to the theoretical predictions, thus rejecting the claim for the existence of strong correlation effects proposed by previous spatially averaged measurements.
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| 4. |
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| 5. |
- Enquist, Henrik, et al.
(author)
-
FemtoMAX - An X-ray beamline for structural dynamics at the short-pulse facility of MAX IV
- 2018
-
In: Journal of Synchrotron Radiation. - 0909-0495. ; 25:2, s. 570-579
-
Journal article (peer-reviewed)abstract
- The FemtoMAX beamline facilitates studies of the structural dynamics of materials. Such studies are of fundamental importance for key scientific problems related to programming materials using light, enabling new storage media and new manufacturing techniques, obtaining sustainable energy by mimicking photosynthesis, and gleaning insights into chemical and biological functional dynamics. The FemtoMAX beamline utilizes the MAX IV linear accelerator as an electron source. The photon bursts have a pulse length of 100fs, which is on the timescale of molecular vibrations, and have wavelengths matching interatomic distances (Å). The uniqueness of the beamline has called for special beamline components. This paper presents the beamline design including ultrasensitive X-ray beam-position monitors based on thin Ce:YAG screens, efficient harmonic separators and novel timing tools.The FemtoMAX beamline facilitates studies of the structural dynamics of materials on the femtosecond timescale. The first commissioning results are presented.
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| 6. |
- Girard, R T, et al.
(author)
-
Electronic structure of ZnO(0001) studied by angle-resolved photoelectron spectroscopy
- 1997
-
In: Surface Science. - 0039-6028 .- 1879-2758. ; 373:2-3, s. 409-417
-
Journal article (peer-reviewed)abstract
- The electronic structure of the ZnO(0001) surface was studied by angle-resolved photoelectron spectroscopy. The recorded normal emission spectra give information about the Valence band states as well as the Zn 3d states. The dispersions of the four valence bands observed in the (0001) direction were compared with theory and are in good agreement with recent calculations which consider the Zn 3d electrons as part of the valence band. The Zn 3d states are seen to separate into two groups of four and six bands, which show dispersion with k(perpendicular to). This is in agreement with theoretical results but the location of these states were not accurately predicted. The present photoemission results show that they lie around 10.5 eV below E(F). Two surface states were observed on the (0001) surface. One, at 7.5 eV binding energy, was predicted by theory and is interpreted as arising from the ''back-bondings'' of the Zn 4s-O 2p mixed bulk states. The other one at 4.5 eV below E(F), most likely Zn 4p-0 2p derived, was not predicted by theoretical calculations and this is discussed further in the text. (C) 1997 Elsevier Science B.V.
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| 7. |
- Lindau, B M, et al.
(author)
-
Morphology of dental enamel and dentine-enamel junction in osteogenesis imperfecta.
- 1999
-
In: International journal of paediatric dentistry / the British Paedodontic Society [and] the International Association of Dentistry for Children. - 0960-7439. ; 9:1, s. 13-21
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: The aim of this study was to examine the morphology of primary and permanent human enamel, and the dentine-enamel junction, in individuals with osteogenesis imperfecta (OI) type I, III and IV in undecalcified sections using polarized light microscopy, microradiography and scanning electron microscopy (SEM), and to relate the findings to the type of OI. SAMPLE AND METHODS: Extracted or exfoliated teeth from 15 patients representing the OI types I, III and IV (12 primary teeth from seven patients, and 11 permanent teeth from eight patients). Ten primary and nine permanent teeth from normal healthy patients served as controls. The teeth were serially cut longitudinally in a bucco-lingual direction and contact microradiographs were made. The sections were examined in polarized light. Sections of primary and permanent teeth were examined by means of SEM. RESULTS: This study shows that the permanent enamel from patients with OI exhibits few structural changes. No relationships were found between enamel morphology and the types of OI (I, III, IV). Primary enamel appeared to be slightly more irregularly mineralized, especially in cases with the additional diagnosis dentinogenesis imperfecta. The major findings were deviations in association with the dentine-enamel junction, and locally a lower degree of mineralization. CONCLUSIONS: The mesodermal disease OI might also be manifested in ectodermal enamel, probably because of suboptimal mesenchymal-ectodermal interactions during amelogenesis.
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| 8. |
- Nyholm, R., et al.
(author)
-
Beamline I311 at MAX-LAB : A VUV/soft X-ray undulator beamline for high resolution electron spectroscopy
- 2001
-
In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0168-9002. ; 467-468, s. 520-524
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Journal article (peer-reviewed)abstract
- We describe a beamline based on a plane-grating monochromator and an end-station designed for high resolution photoemission and photoabsorption spectroscopy on surfaces and interfaces using undulator radiation in the energy range 30 1500 eV. The general design of the beamline is based on a horizontally focusing pre-mirror, an SX-700 type of plane-grating monochromator and re-focusing optics of Kirkpatrick-Baez design.
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| 9. |
- Nyholm, R., et al.
(author)
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ELECTRONIC AND STRUCTURAL-PROPERTIES OF THE CU-BI2CASR2CU2O8 INTERFACE
- 1991
-
In: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 180:1-4, s. 120-123
-
Journal article (peer-reviewed)abstract
- The formation of the Cu-Bi2CaSr2Cu2O8 interface has been studied by photoelectron spectroscopy using synchrotron radiation. Photon energies in the range 20-1000 eV were utilized in order to probe both the valence band and to monitor chemical changes upon Cu deposition, as revealed by the core-level shifts. A strong chemical reaction between Bi2CaSr2CuO8 and Cu is manifested by the formation of metallic Bi. From the intensity variations as a function of electron emission angle it is shown that the metallic Bi segregates to the top surface layer.
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| 10. |
- Nyholm, R., et al.
(author)
-
PHOTOEMISSION-STUDY OF THE BI2CASR2CU2O8 SUPERCONDUCTOR WITH CU, AG AND AU OVERLAYERS
- 1993
-
In: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 218:1-2, s. 103-108
-
Journal article (peer-reviewed)abstract
- In this paper, we present a photoemission study of the interaction of Cu, Ag and Au with clean single-crystal Bi2CaSr2Cu2O8 superconductor surfaces. Both the valence-band and the Bi 5d, O 1 s and Sr 3d core levels were monitored for all overlayers. Cu, Ag and Au were deposited as consecutively thicker layers starting with a third of a monolayer and progressing in steps up to a deposition in the range of eight monolayers. Comparing the results for the different overlayers reveals the Ag overlayer to be less reactive than Au which causes the formation of metallic Bi on cleaved Bi2CaSr2Cu2O8 surface. Cu is shown to be the most reactive of the three metals. The Au and Ag overlayers display an island-growth mode, while Cu grows in a layer-by-layer fashion.
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| 11. |
- Nyholm, R., et al.
(author)
-
SYNCHROTRON-RADIATION SOFT-X-RAY PHOTOEMISSION-STUDY OF LEAD ON BI2CASR2CU2O8
- 1992
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:10, s. 6488-6494
-
Journal article (peer-reviewed)abstract
- In this paper we present a study of the interaction of Pb with a clean single-crystal Bi2CaSr2Cu2O8 superconductor surface based on photoemission and low-energy electron diffraction (LEED). Deposition of Pb on a Bi2CaSr2Cu2O8 Crystal kept at room temperature gives rise to the formation of metallic Bi and oxidized Pb at the interface. This behavior could not be observed when the crystal was kept at 100 K during Pb deposition. For all investigated Pb overlayers on a cold crystal (100 K), surface-sensitive photoelectron spectroscopy revealed the growth of a covering metallic Pb overlayer film. The growth at 100 K, contrary to the growth at room temperature, preserved the original LEED 5 X 1 pattern even for Pb depositions corresponding to a 24-angstrom thick overlayer indicating epitaxial growth. Furthermore, a rigid 0.4-eV shift of the valence band and the Bi 5d core levels is observed upon initial Pb deposition and is tentatively attributed to electron doping.
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| 12. |
- Nylén, H., et al.
(author)
-
O KVV Auger emission versus resonant photoemission at the O K edge of high-Tc superconductors
- 1998
-
In: Physica C: Superconductivity and its Applications. - 0921-4534. ; 300:3-4, s. 161-170
-
Journal article (peer-reviewed)abstract
- Photoelectron spectroscopy results on single crystals of the superconductors Bi2Sr2CaCu2O8,Bi2Sr 2CuO6, Ba0.6K0.4BiO3 and the semiconductor Ba0.9K0.1BiO3 are reported for the photon energy region around the O K absorption threshold. The development of the O-KVV Auger structure has been carefully monitored as a function of photon energy. A non-monotonic behavior displaying a feature at a constant binding energy of about 14 eV was found for Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 in a narrow photon energy region of 1 eV at the main edge of the O K absorption spectrum around 530 eV. The corresponding enhancement, connected with the autoionization of O 2 p states, is absent in Ba1-xKxBiO3 in contrast to Bi2Sr2CaCu2O8 and Bi2Sr2CuO6. The resonant enhancement is more pronounced for Bi2Sr2CuO6 as compared to Bi2Sr2CaCu2O8, which can be explained by a lower charge carrier concentration in the former case, leading to a more localized nature of intermediate O 2 p states. The model parameters Cu d-d and O p-p Coulomb interactions and the charge transfer energy Δ are estimated from the experiments.
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| 13. |
- Qvarford, M, et al.
(author)
-
Doping dependence of the O 1s is core-level photoemission in bi-Sr-Ca-Cu-O superconductors
- 1996
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 53:22, s. 14753-14756
-
Journal article (peer-reviewed)abstract
- The O 1s core level of three different Bi-Sr-Ca-Cu-O superconductors has been studied by means of high-resolution x-ray-photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS). The O 1a XPS spectra could be decomposed into three components that were unambiguously assigned to the emission from the three different oxide layers in the crystal structure. These are, in order of increasing binding energy, Cu-O-2, Sr-O, and Bi-O. Furthermore, the component assigned to the Cu-O-2 layers exhibits a shift which depends on the hole doping as monitored by the XAS spectra.
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| 14. |
- Qvarford, M, et al.
(author)
-
Doping dependence of the O 1s is core-level photoemission in bi-Sr-Ca-Cu-O superconductors
- 1996
-
In: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 53:22, s. 14753-14756
-
Journal article (other academic/artistic)abstract
- The O 1s core level of three different Bi-Sr-Ca-Cu-O superconductors has been studied by means of high-resolution x-ray-photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS). The O 1a XPS spectra could be decomposed into three component
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| 15. |
- Qvarford, M, et al.
(author)
-
Photoemission and x-ray absorption study of superconducting and semiconducting Ba1-xKxBiO3 single crystals
- 1996
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:9, s. 6700-6707
-
Journal article (peer-reviewed)abstract
- Semiconducting Ba0.9K0.1BiO3 and superconducting Ba0.6K0.4BiO3 single crystals cleaved in situ have been studied by core level and valence band photoelectron spectroscopy and O K edge x-ray absorption spectroscopy. It was found that the general shape of the valence band spectrum agrees with the shape predicted by band structure calculations, but the intensity near the Fermi level, was lower in the experimental spectrum as compared to the calculated. The O K edge spectra showed that the metallic phase is not related to the presence of doping inducted O 2p holes. This property of Ba1-xKxBiO3 shows that the semiconductor-metal transition of this system is of a different nature than that of the hole doped cuprate high-T-c superconductors. The core level photoemission spectra of the cations showed a small asymmetry for Ba0.9K0.1BiO3. Corresponding spectra for Ba0.6K0.4BiO3 showed a larger asymmetry resulting in a resolved high binding energy shoulder in the Bi 4f spectrum. The origin of this feature is discussed.
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| 16. |
- Qvarford, M., et al.
(author)
-
Polarisation-dependent X-ray absorption in high- and low-Tc Bi2Sr2Can-1CunO4+2n superconductors
- 1993
-
In: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 214:1-2, s. 119-126
-
Journal article (peer-reviewed)abstract
- Taking advantage of the linear polarisation of synchrotron radiation, the polarisation dependence of the O K and Cu L3 X-ray absorption edges has been compared for in situ cleaved Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 single crystals. The X-ray absorption spectra were measured by means of total electron yield detection. The spectra show for both crystals that the lowest unoccupied Cu 3d and O 2p orbitals are dominantly oriented parallel to the a-b plane, but also the presence of a small amount of unoccupied orbitals oriented perpendicular to the a-b plane can be deduced from both the O K and Cu L3 absorption spectra. A shift of the order of 0.5 eV between absorption into the in-plane and the out-of-plane Cu 3d orbitals was measured for the Bi2Sr2CaCu2O8 crystal, but no such shift was found for the Bi2Sr2CuO6 crystal.
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| 17. |
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| 18. |
- QVARFORD, M, et al.
(author)
-
X-RAY-ABSORPTION AND RESONANT-PHOTOEMISSION STUDY OF CA IN THE HIGH-TEMPERATURE SUPERCONDUCTOR BI2SR2CACU2O8
- 1992
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 46:21, s. 14126-14133
-
Journal article (peer-reviewed)abstract
- The electronic structure of Ca in the high-temperature superconductor Bi2Sr2CaCu2O8 has been studied by x-ray-absorption spectroscopy and resonant-photoemission at the Ca L2,3 absorption edge. In the x-ray-absorption spectrum no edge structure is seen at the energy corresponding to the Ca 2p3/2 core-level binding energy, in agreement with the very low Ca density of states at the Fermi level predicted by band-structure calculations. Furthermore, the crystal-field splitting of the Ca 3d level, which is characteristic of ionic Ca compounds, is clearly observed in the x-ray-absorption spectrum. The photoemission spectra display strong resonant enhancements of the Ca 3s and 3p core levels as well as strong changes in the intensity and the line shape of the Ca L2,3M2,3M2,3 Auger structure at the Ca L2,3 threshold, showing the localized nature of the 3d states in core ionized Ca. The 3d induced spectator shift of the Ca L2,3M2,3M2,3 complex is fairly small as compared to what has been reported for CaF2, indicating that the screening of the normal Auger final state by the charge carriers in the surrounding Cu-O2 layers is quite efficient. From the Ca L2,3M2,3M2,3 data it is also suggested that, at the Ca L2 threshold, the excited 3d electron participates in a Coster-Kronig-type decay resulting in a 2p3/2 core hole followed by a normal L3M2,3M2,3 Auger decay.
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| 19. |
- Qvarford, M., et al.
(author)
-
X-ray absorption study of oxygen in the high-Tc superconductor Bi2Sr2CaCu2O8 near the interfaces to Cu, Ag and Au
- 1996
-
In: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 265:1-2, s. 113-120
-
Journal article (peer-reviewed)abstract
- The influence on O 2p holes in single crystalline Bi2Sr2CaCu2O8 upon the interface formation to Cu, Ag and Au has been studied by O K edge X-ray absorption measurements. It was found that Cu reduces the amount of doping induced O 2p holes significantly in the vicinity of the interface, whereas Ag and Au gave a much smaller reduction of these states. Photoemission spectra confirmed previous findings that Cu causes a strong chemical reaction at the Bi-O surface of Bi2Sr2CaCu2O8, in contrast to Ag and Au which induced only a minimal reaction. The results support the opinion that the Bi-O layers are essential for the doping of the Cu-O2 layers in Bi2Sr2CaCu2O8.
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| 20. |
- ROGELET, T, et al.
(author)
-
ELECTRONIC-STRUCTURE OF NIO(1 0 0) WITH ADSORBED NA
- 1993
-
In: Solid State Communications. - 0038-1098 .- 1879-2766. ; 85:7, s. 657-660
-
Journal article (peer-reviewed)abstract
- Adsorption of Na on single crystals of NiO(1 0 0) at room temperature has been investigated via angle-resolved photoemission spectroscopy and measurements of work-function changes. The drastic changes in the valence band spectra upon Na deposition are assigned to a chemical reaction between Na and O where metallic Ni is left as by-product. At short deposition times, Na mainly acts as an inert electron donor, and at these coverages no dispersion is observed in the angle-resolved photoemission spectra which indicates that the electronic states are localized. The measurements were performed both for a polished and an in-situ cleaved NiO crystal.
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| 21. |
- Soderholm, S, et al.
(author)
-
A photoelectron spectroscopy and x-ray absorption study of Bi2Sr2CaCu2O8 single crystal with adsorbed Cs : On the origin of the states affected by electron doping and evidence for spatially resolved electron doping
- 1996
-
In: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 8:9, s. 1307-1320
-
Journal article (peer-reviewed)abstract
- The influence of electron doping, via deposition of small amounts of Cs, on the electronic structure of Bi2Sr2CaCu2O8 has been studied by high-resolution photoelectron spectroscopy (PES) and x-ray absorption spectroscopy (XAS), utilizing synchrotron radiation. The changes in the electronic structure were monitored by PES of the valence band and of the O Is, Bi 4f, Bi 5d, Ca 2p and Sr 3d core levels, and by XAS at the O Is, Cu 2p and Ca 2p edges. The experimental data suggest that the loss of the Fermi edge and the loss of spectral intensity down to about 2 eV below the Fermi level, and the substantial loss of spectral intensity of the pre-edge structure in the O 1s XAS spectrum are mainly due to annihilation of states with O 2p character in the Cu-O layer. It is evident from bulk- and surface-sensitive XAS spectra that the electron doping by Cs affects the electronic structure more strongly close to the surface. This implies that the doping occurs locally and that the charge transfer between the different layers in the unit cell is not uniform. Thus it seems possible to alter the electronic properties of Bi2Sr2CaCu2O8 locally through spatially resolved electron doping. When larger amounts of Cs are deposited, a chemical reaction occurs which causes a disruption of the Bi-O layer. This deposition regime is characterized by the presence of caesium oxide and reduced (metallic) Bi.
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| 22. |
- Thorild, I, et al.
(author)
-
Caries in 4-year-old children after maternal exposure to chewing gums containing combinations of xylitol, sorbitol, chlorhexidine and fluoride.
- 2006
-
In: European archives of paediatric dentistry : official journal of the European Academy of Paediatric Dentistry. ; 7:4, s. 241-245
-
Journal article (peer-reviewed)abstract
- Aim: To evaluate the effect of maternal use of chewing gums containing combinations of xylitol, sorbitol, chlorhexidine and fluoride on caries prevalence in a group of mother’s 4-year-old children. Study design: Randomised controlled trial. Methods: After screening 416 women with newborn babies, 173 mothers with high counts of salivary mutans streptococci (MS) were randomly assigned into three experimental chewing gum groups containing A) xylitol (n=61), B) chlorhexidine/xylitol/sorbitol (n=55), and C) sodium fluoride/ xylitol/sorbitol (n=57). The intervention started when each child was 6 months old, was terminated one year later. All of the mothers were instructed to chew one piece of the appropriate gum for 5 minutes, three times a day. The outcome measure was the presence of cavitated and non-cavitated (enamel) lesions in the primary dentitions of the children at the age of 4 years. Results: The drop-out rate in the experimental groups was 15-20%. The mean defs, on examination at aged 4 years was 0.4 ±1.0 in group A, 0.7 ±1.7 in group B and 1.4 ±3.0 in group C. The difference between group A and C was statistically significant (p<0.05). Conclusions: Less caries was observed in children of mothers who chewed gums with xylitol as the single sweetener during the time of eruption of the first primary teeth compared with those who used gums containing fluoride, sorbitol and lower amounts of xylitol.
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| 23. |
- Tjernberg, O, et al.
(author)
-
Evidence of pseudogap related core level shifts in Bi2Sr2Ca1-xYxCu2O8+delta
- 1997
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 79:3, s. 499-502
-
Journal article (peer-reviewed)abstract
- Photoelectron spectroscopy data from Bi2Sr2Ca1-xYxCu2O8+delta Single crystals, for x = 0, 0.16, and 0.55, are presented. It is shown that there are core level shifts related to the opening of a pseudogap and that similar shifts are observed at the opening of the superconducting gap in optimally doped samples. This result is in agreement with pair formation above T-c as suggested by V.J. Emery and S.A. Kivelson [Nature (London) 374, 434 (1995)].
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| 24. |
- Tjernberg, O, et al.
(author)
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Evidence of pseudogap related core level shifts in Bi2Sr2Ca1-xYxCu2O8+delta
- 1997
-
In: PHYSICAL REVIEW LETTERS. - : AMER INST PHYSICS. - 0031-9007. ; 79:3, s. 499-502
-
Journal article (other academic/artistic)abstract
- Photoelectron spectroscopy data from Bi2Sr2Ca1-xYxCu2O8+delta Single crystals, for x = 0, 0.16, and 0.55, are presented. It is shown that there are core level shifts related to the opening of a pseudogap and that similar shifts are observed at the opening
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| 25. |
- Tjernberg, O, et al.
(author)
-
Influence of magnetic ordering on the NiO valence band
- 1996
-
In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:15, s. 10245-10248
-
Journal article (peer-reviewed)abstract
- The influence of magnetic ordering on the NiO valence band has been studied by angle resolved photoelectron spectroscopy. Measurements have been performed at temperatures above and below the Neel temperature (T-N), as well as at room. temperature. The results show temperature dependence but no significant changes in the valence band structure are detected in connection to the passing of T-N. The reported data suggest that the magnetic phase transition does not influence the valence band structure significantly.
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| 26. |
- Tjernberg, O, et al.
(author)
-
Resonant photoelectron spectroscopy on NiO
- 1996
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 53:15, s. 10372-10376
-
Journal article (peer-reviewed)abstract
- Resonant photoelectron spectroscopy studies have been performed on the NiO valence band at photon energies corresponding to the Ni 2p, 3p, and O 1s absorption thresholds. Strong resonances are seen in the vicinity of the Ni 2P threshold, which confirm earlier conclusions from the weaker resonances seen at the Ni 3p threshold. No valence-band resonance is observed at the O 1s threshold. The analysis of this data confirms the picture of NiO as a strongly correlated charge-transfer insulator by identifying the highest-lying states as being of mainly 3d(8)L final-state character. The existence of localized excited Ni states, as well as the delocalized nature of the O states, are confirmed. Comparisons with the configuration-interaction model and quasiparticle calculations are also made.
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| 27. |
- Zakharov, A. A., et al.
(author)
-
Metal-dielectric transition in Ba0.6K0.4BiO3-y single crystals studied by scanning photoelectron microscopy
- 1997
-
In: Physical Review B (Condensed Matter). - 0163-1829. ; 56:10
-
Journal article (peer-reviewed)abstract
- The electronic structure of Ba0.6K0.4BiO3-y single crystals has been studied using a scanning photoelectron microscope with a lateral resolution in the one micrometer range. It is possible to change the oxygen content (y) and convert the surface from the metallic to the dielectric state presumably by breaking the Bi-O bonds by using the focused zero-order light to irradiate the sample surface. The electronic states close to the Fermi level after such a treatment show a different doping dependence as compared to the case of potassium doping. By imaging the surface on the micrometer scale we find significant variations in the valence band intensity over the surface and observe a rather large intensity of the density of states close to the Fermi level. This will have a large impact on the discussions of dynamical lattice distortion and pseudogap behavior in the metallic phase.
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