Search results for "PHOTOEMISSION"
showing 10 items of 174 documents
WOx phase growth on SiO2/Si by decomposition of tungsten hexacarbonyl:Influence of potassium on supported tungsten oxide phases
2009
International audience; Synchrotron based photoemission spectroscopy was used to study the adsorption of tungsten hexacarbonyl on SiO2 surfaces modified by potassium. Results were compared with the ones obtained when no potassium was present. Experiments using W4f and Si2p intensities variations show that, at 140 K, the tungsten hexacarbonyl growth proceeds via a simultaneous multilayer mode for the two kinds of surfaces but with differences in compositions of growing layers. Indeed, it is evidenced that, even at cryogenic temperatures, the presence of potassium induces decomposition of a significant part of tungsten hexacarbonyl molecules through a strong interaction between tungsten and p…
Electronic structure of tetraphenyldithiapyranylidene : A valence effective Hamiltonian theoretical investigation
1992
We present a theoretical investigation of the electronic structure of tetraphenyldithiapyranylidene (DIPSΦ4) using the nonempirical valence effective Hamiltonian (VEH) method. Molecular geometries are optimized at the semiempirical PM3 level which predicts an alternating nonaromatic structure for the dithiapyranylidene (DIPS) framework. The VEH one‐electron energy level distribution calculated for DIPSΦ4 is presented as a theoretical XPS simulation and is analyzed by comparison to the electronic structure of its molecular components DIPS and benzene. The theoretical VEH spectrum is found to be fully consistent with the experimental solid‐state x‐ray photoelectron spectroscopy (XPS) spectrum…
High-pass energy-filtered photoemission electron microscopy imaging of dopants in silicon.
2008
Differently doped areas in silicon can show strong electron-optical contrast in dependence on the dopant concentration and surface conditions. Photoemission electron microscopy is a powerful surface-sensitive technique suitable for fast imaging of doping-induced contrast in semiconductors. We report on the observation of Si (100) samples with n- and p-type doped patterns (with the dopant concentration varied from 10(16) to 10(19) cm(-3)) on a p- and n-type substrate (doped to 10(15) cm(-3)), respectively. A high-pass energy filter of the entire image enabled us to obtain spectroscopic information, i.e. quantified photo threshold and related photoyield differences depending on the doping lev…
Optical magnetic circular dichroism in threshold photoemission from a magnetite thin film
2011
Threshold photoemission excited by polarization-modulated ultraviolet femtosecond laser light is exploited for phase-sensitive detection of magnetic circular dichroism (MCD) for a magnetite thin film. Magnetite (Fe(3)O(4)) shows a magnetic circular dichroism of ∼(4.5 ± 0.3) × 10(-3) for perpendicularly incident circularly polarized light and a magnetization vector switched parallel and antiparallel to the helicity vector by an external magnetic field. The asymmetry in threshold photoemission is discussed in comparison to the magneto-optical Kerr effect. The optical MCD contrast in threshold photoemission will provide a basis for future laboratory photoemission studies on magnetic surfaces.
Investigating spintronics thin film systems with synchrotron radiation
2009
Abstract Spintronics is a research field involving a wide variety of different magnetic materials. Synchrotron radiation in the VUV and soft X-ray regime is ideally suited to investigate the relationships between magnetic properties and electronic structure of spintronics thin film stacks. Complex layered structures and nanomagnets are the main building blocks for current and future spintronics applications. In this contribution we describe the study of spintronics model systems with respect to the static and dynamic behavior with an emphasis on interfaces.
Orbital Rashba effect in a surface-oxidized Cu film
2020
Recent experimental observation of an unexpectedly large current-induced spin-orbit torque in surface oxidized Cu on top of a ferromagnet pointed to a possibly prominent role of the orbital Rashba effect (ORE) in this system. Here, we use first principles methods to investigate the ORE in a system of oxygen monolayer deposited on top of a Cu(111) film. We show that surface oxidization of the Cu film leads to a gigantic enhancement of the ORE near the Fermi energy. The resulting chiral orbital texture in the momentum space is exceptionally strong, reaching as much as $\ensuremath{\sim}0.5\ensuremath{\hbar}$ in magnitude. We find that resonant hybridization between O $p$ states and Cu $d$ sta…
Observation of quantized subband states and evidence for surface electron accumulation in CdO from angle-resolved photoemission spectroscopy
2008
The electronic structure of well-ordered single-crystal thin films of CdO100 has been studied using angleresolved photoemission spectroscopy. Quantized electron subbands are observed above the valence-band maximum. The existence of these states provides evidence of an intrinsic electron accumulation space-charge layer near the CdO surface, an interpretation supported by coupled Poisson-Schrodinger calculations. The origin of the accumulation layer result is discussed in terms of the bulk band structure of CdO calculated using quasiparticle-corrected density-functional theory, which reveals that the conduction-band minimum at the Brillouin-zone center lies below the charge neutrality level.
Surface resonance of thin films of the Heusler half-metal Co2MnSi probed by soft x-ray angular resolved photoemission spectroscopy
2019
Heusler compounds are promising materials for spintronics with adjustable electronic properties including 100% spin polarization at the Fermi energy. We investigate the electronic states of ${\mathrm{AlO}}_{x}$ capped epitaxial thin films of the ferromagnetic half-metal ${\mathrm{Co}}_{2}\mathrm{MnSi}$ ex situ by soft x-ray angular resolved photoemission spectroscopy (SX-ARPES). Good agreement between the experimental SX-ARPES results and photoemission calculations including surface effects was obtained. In particular, we observed in line with our calculations a large photoemission intensity at the center of the Brillouin zone, which does not originate from bulk states, but from a surface r…
Bulk spin polarization of magnetite from spin-resolved hard x-ray photoelectron spectroscopy
2021
Physical review / B 104(4), 045129 (1-10) (2021). doi:10.1103/PhysRevB.104.045129
Magnetic dichroism in photoemission with unpolarized light.
1994
A magnetic dichroism in photoemission from ferromagnets induced by unpolarized light is observed for the first time in the valence band region as well as for surface states. The study was carried out with magnetized Fe(110), Co(0001), and Gd(0001) films grown epitaxially on W(110). This phenomenon leads to an intensity asymmetry for opposite directions of the sample magnetization. It can be easily used for a routine laboratory diagnostic of magnetic behavior. A simple theoretical interpretation of the phenomenon based on the atomic model is given.