Hard X-ray photoelectron spectroscopy: sensitivity to depth, chemistry and orbital character

Dallera, C.; Braicovich, L.; Duó, Lamberto; Palenzona, A.; Panaccione, G.; Paolicelli, G; Cowie, Bruce C. C.; Zegenhagen, J.

doi:10.1016/j.nima.2005.05.017

Cited by 16 publications

(7 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the hard X-ray regime, the emitted photoelectrons have sufficiently large kinetic energy, such that the forward scattering is the dominant interaction with the solid, thus we can ignore the effects of elastic scattering [ 47 ]. This means that the profile of escaping electrons should follow an exponential decay with the distance the electron must travel in order to escape the solid.…”

Section: Resultsmentioning

confidence: 99%

“…This is a severe problem for VO 2 , where even the partial reduction of vanadium at the surface can result in the formation of various V x O y metastable phases that can still display metal-insulator transitions. These surface reduction issues can be circumvented by use of HAXPES, which increases the effective probing depth and reduces the sensitivity to attenuating carbonate and hydroxyl overlayers compared to traditional PES [ 47 , 48 ]. The orbital and elemental sensitivity of XAS already reduces the need for atomically-clean surfaces.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

et al. 2015

View full text Add to dashboard Cite

Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe a low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Our results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. More generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Thus, it facilitates a bulk electronic structure investigation of materials. [15,16,17] In this work, we study bulk sensitive 2p core-level HX-PES (hν = 5.95 keV) of V 1.98 Cr 0.02 O 3 and the optimally doped high-T c cuprate (Bi2212) as typical examples of MH and CT systems, respectively. Single crystals of V 1.98 Cr 0.02 O 3 showed a sharp metal-insulator transition at 170 K, [7] while Bi2212 showed a superconducting T c of 90 K. [18] HX-PES measurements were performed in a vacuum of 1 × 10 −10 Torr at undulator beam line BL29XU, SPring-8 [19] using a Scienta R4000-10KV electron analyzer.…”

mentioning

confidence: 99%

Bulk screening in core-level photoemission from Mott-Hubbard and charge-transfer systems

et al. 2005

View full text Add to dashboard Cite

We report bulk-sensitive hard X-ray (hν = 5.95 keV) core-level photoemission spectroscopy (PES) of single crystal V1.98Cr0.02O3 and the high-Tc cuprate Bi2Sr2CaCu2O 8+δ (Bi2212). V1.98Cr0.02O3 exhibits low binding energy "satellites" to the V 2p "main lines" in the metallic phase, which are suppressed in the antiferromagnetic insulator phase. In contrast, the Cu 2p spectra of Bi2212 do not show temperature dependent features, but a comparison with soft X-ray PES indicates a large increase in the 2p 5 3d 9 "satellites" or 3d 9 weight in the bulk. Cluster model calculations, including full multiplet structure and a screening channel derived from the coherent band at the Fermi energy, give very satisfactory agreement with experiments.PACS numbers: 71.30.+h, 74.72.Hs, 78.20.Bh, Core-level photoemission spectroscopy (PES) has played a very important role in our understanding of the electronic structure of correlated transition metal (TM) and rare-earth compounds.[1] The appearance of strong satellite structure accompanying the main peaks in correlated systems is well known and systematic variations in the position and intensities of these satellites provide us important clues to their electronic structure.[2, 3, 4] The inter-atomic configuration-interaction approach, using a cluster model or Anderson impurity model , gives a quantitative interpretation for satellite intensities and positions, leading to an accurate description of the ground state and excitation spectrum. [2,3,4] In this approach, the physics of TM compounds can be described in terms of a few parameters, namely, the d-d Coulomb repulsion energy U , the charge-transfer energy ∆, the ligand p-TM d hybridization energy V , and the core-hole-d electron Coulomb attraction energy U dc . Zaanen, Sawatzky and Allen[5] proposed a classification scheme for TM compounds which soon evolved into a paradigm. In this scheme, the band gaps of late TM compounds are socalled charge-transfer (CT) type with U > ∆. NiO and CuO are typical examples of CT insulators while the high-T c cuprates are CT insulators driven metallic by doping. In contrast, the early TM compounds, with U < ∆ are Mott-Hubbard (MH) systems. V 2 O 3 , with its alloys, plays the role of a classic MH system displaying a correlation induced metal-insulator transition. [6,7,8] While the old picture of the MH metal-insulator transition involved a complete collapse or a coalescence of the lower and upper MH bands into a single band in the metal phase, photoemission studies showed the formation of a well-defined coherent band at the Fermi level in the presence of remnant MH bands for a series of correlated oxides [9] and very recently, also for V 2 O 3 .[10] The experimental results are in excellent agreement with calculations using dynamic mean-field theory (DMFT). [10,11] In spite of these successes of PES, the surface sensitivity of PES has often led to controversies regarding surface versus bulk electronic structure, and hence, hard Xray (HX)-PES is very important and promising. [12,13] With the develop...

show abstract

“…Photoelectron spectroscopy with soft x rays (PES) has been shown to be a very valuable technique for the investigation of the electronic states of rare-earth compounds [34][35][36], but suffers from surface effects. PES with hard x rays (HAX-PES), on the other hand, provides the bulk sensitivity of about 80 Å that is necessary to image the bulk electronic structure in these systems [37][38][39][40], especially in correlated electron systems where the degree of hybridization of the outermost surface layers can be reduced with respect to the bulk [39,41,42].…”

Section: Experiments and Simulationmentioning

confidence: 99%

Quantitative investigation of the 4f occupation in the quasikagome Kondo lattice CeRh1−xPdxSn

et al. 2021

View full text Add to dashboard Cite

CeRhSn with the Ce atoms forming a quasikagome lattice in the hexagonal plane has recently been discussed in the context of quantum criticality driven by magnetic frustration. Furthermore, it has been reported that the successive substitution of Rh by Pd leads to magnetic order. Here we have investigated the change of the 4 f occupation in the substitution series CeRh 1−x Pd x Sn for for x = 0, 0.1, 0.3, 0.5, 0.75 by means of photoelectron spectroscopy with hard x rays (HAXPES). The quantitative analysis of the core level spectra with a combined full multiplet and configuration interaction analysis shows a smooth decrease of the 4 f 0 contribution with rising x due to an increase of the effective 4 f binding energy ε 4 f and the reduction of the effective hybridization V eff . We further compare valence band data with the calculated partial density of states and find that the Pd 4d states are about 1 eV further away from the Ce 4 f states at the Fermi energy than the Rh 4d states. In fact, the effective binding energy ε 4 f of the 4 f states in the configuration interaction analysis of the core level spectra decreases by the same amount.

show abstract

Hard X-ray photoelectron spectroscopy: sensitivity to depth, chemistry and orbital character

Cited by 16 publications

References 35 publications

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

Bulk screening in core-level photoemission from Mott-Hubbard and charge-transfer systems

Quantitative investigation of the 4f occupation in the quasikagome Kondo lattice CeRh1−xPdxSn

Contact Info

Product

Resources

About