Band structure of platinum from angle resolved photoemission experiments

Leschik, G.; Courths, R.; Wern, H.; Hüfner, S.; Eckardt, H.; Noffke, J.

doi:10.1016/0038-1098(84)90631-8

Cited by 42 publications

(8 citation statements)

References 14 publications

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“…The band structure of platinum has been determined by angleresolved ultraviolet photoemission spectroscopy (ARUPS) with general agreement with fully relativistic self-consistent calculations. 16 The lowest valence band (mostly s character) does not cross the Fermi level, suggesting an electronic configuration close to s 2 d 8 , in agreement with IEM predictions. However, calculations of the d occupancy vary significantly.…”

Section: Platinum Clusterssupporting

confidence: 82%

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Chemisorption of Organics on Platinum. 1. The Interstitial Electron Model

1998

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Using first principles quantum mechanics (nonlocal density functional theory), we studied the bonding and electronic states for clusters of Pt atoms. These calculations suggest the interstitial electron model (IEM) in which (i) the 6s valence orbitals from the four atoms of a tetrahedron combine to form an interstitial bonding orbital at the center of the tetrahedron that is occupied by two electrons to form the interstitial electron bond (IEB), (ii) the 5d valence orbitals from each atom form a band of bonding and antibonding states sufficiently dense that the optimum occupation is high spin (Hund's rule) or nearly so, and (iii) bonds of organics to the Pt surface lead to covalent σ bonds to d orbitals localized on individual Pt atoms. This simple model explains the bonding and lowest electronic state of essentially all clusters studied. The IEM suggests that the bonding in three-dimensional face-centered cubic (fcc) systems has two electrons from each atom in the IEB, leaving the remaining eight valence electrons in d-like orbitals. For bulk Pt, this leads to a 6s 2 5d 8 effective electronic configuration. The IEM suggests that the (111) surface of Pt would have a 6s 1 5d 9 effective electronic configuration. This suggests that to model the chemistry of the Pt(111) surface we should use clusters leading to the (6s) 1 (5d) 9 configuration. This suggests the interstitial electron surface model (IESM) in which a simple planar cluster with eight atoms serves to model the chemistry of the Pt (111) surface. This is used in the accompanying paper (part 2) to examine CH x and C 2 H x species chemisorbed on Pt(111).

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Section: Platinum Clusterssupporting

confidence: 82%

“…16 The lowest valence band (mostly s character) does not cross the Fermi level, suggesting an electronic configuration close to s 2 d 8 , in agreement with IEM predictions. However, calculations of the d occupancy vary significantly.…”

Section: Implications Of the Iem For Bulk Ptsupporting

confidence: 80%

Chemisorption of Organics on Platinum. 1. The Interstitial Electron Model

1998

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“…Using equation (4) the reason for the existence of such a spin polarization component is identified: a phase shift of two complex matrix elements defining two outgoing partial waves leaving the crystal in two different hole states with identical energy as shown in figure 27 (right part). The two complex transition dipole matrix elements have been identified to describe the transition from initial 4 5 and 3 5 bands at the X-point of the band structure calculated by Noffke [53,54] in the hybridization region as given in figure 28. It is worth noting that the quantum mechanical interference of two outgoing partial waves describing the photoelectrons which result in a spin polarization perpendicular to the reaction plane is, of course, a final state effect, although the corresponding bands which show hybridization are initial bands in figure 28.…”

Section: Phase-shift-determined Spin Polarization In the Angle-resolv...mentioning

confidence: 99%

Spin–orbit-induced photoelectron spin polarization in angle-resolved photoemission from both atomic and condensed matter targets

Heinzmann

Dil

2012

J. Phys.: Condens. Matter

117

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The existence of highly spin polarized photoelectrons emitted from non-magnetic solids as well as from unpolarized atoms and molecules has been found to be very common in many studies over the past 40 years. This so-called Fano effect is based upon the influence of the spin-orbit interaction in the photoionization or the photoemission process. In a non-angle-resolved photoemission experiment, circularly polarized radiation has to be used to create spin polarized photoelectrons, while in angle-resolved photoemission even unpolarized or linearly polarized radiation is sufficient to get a high spin polarization. In past years the Rashba effect has become very important in the angle-resolved photoemission of solid surfaces, also with an observed high photoelectron spin polarization. It is the purpose of the present topical review to cross-compare the spin polarization experimentally found in angle-resolved photoelectron emission spectroscopy of condensed matter with that of free atoms, to compare it with the Rashba effect and topological insulators to describe the influence and the importance of the spin-orbit interaction and to show and disentangle the matrix element and phase shift effects therein.The relationship between the energy dispersion of these phase shifts and the emission delay of photoelectron emission in attosecond-resolved photoemission is also discussed. Furthermore the influence of chiral structures of the photo-effect target on the spin polarization, the interferences of different spin components in coherent superpositions in photoemission and a cross-comparison of spin polarization in photoemission from non-magnetic solids with XMCD on magnetic materials are presented; these are all based upon the influence of the spin-orbit interaction in angle-resolved photoemission.

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“…14, while the quite high electron mass in Pt was experimentally measured in Ref. 19. Figure 2 shows that the transmission coefficient has several peaks that correspond to distinct discrete states in the structure, the position of these peaks being very sensitive to the gate voltage, which influences the value of ⌬E.…”

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confidence: 88%

Voltage-controlled high-frequency oscillations based on suspended semiconducting carbon nanotubes

Dragoman

2006

Phys. Rev. B

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A series of tunable negative differential conductance regions at room temperature is demonstrated in semiconducting carbon nanotubes suspended over a trench with a metallic gate at its bottom. The substrateless carbon nanotube is in fact a wide quantum well that experiences a series of negative differential conductance regions due to the very large difference between the effective masses in the well and the tunneling contacts. The positions of these regions can be tuned by modifying the gate voltage. Since the negative differential conductance is the key element of high-frequency oscillators, the suspended nanotube is a voltage-controlled oscillator able to work up to THz frequencies. This device could have important applications in high-frequency nanoelectronic devices and multivalued logic.Single-walled or multiwalled semiconducting carbon nanotubes ͑CNTs͒ are key elements for CNT diodes or transistors working up to a few terahertz ͑THz͒ since they show a very high mobility and very long mean free paths at room temperature. A review of the physical properties of CNTs and their applications for microwave and millimeterwave devices is found in Ref. 1 while Refs. 2 and 3 report the first experimental data, which demonstrate the huge potential of CNTs in the high-frequency domain.The single-or multiwalled CNTs in a substrateless geometry consisting of a CNT suspended over a trench a few m in depth, which has on the bottom a patterned metallic electrode that plays the role of the gate, are a basic configuration because a multitude of physical effects take place uniquely in this geometry. For example, the ballistic transport of carriers at room temperature over a mean free path exceeding 1.5 m, 4 the ballistic phonon propagation, 5 the electrical generation and absorption of phonons, 6 Fabry-Perot interferences, the single-electron transistor effect, 7 the Coulomb blockade effect, 8 the Aharonov-Bohm effect, 9 and the roomtemperature negative differential conductance ͑NDC͒ at low electric fields, 10 were experimentally evidenced in substrateless CNTs. This wealth of physical phenomena originates in the suspended geometry, which forbids the interactions between the nanotube and the supporting substrate. 11 The NDC at room temperature in semiconducting CNTs due to resonant tunneling was theoretically predicted 12 and experimentally demonstrated in various CNT configurations. 13,14 However, no reference to NDC tunability appears in these works. It is thus the main aim of this paper to investigate the NDC tunability with the gate voltage, due to its paramount importance in miniaturized high-frequency oscillators able to work up to THz. In this context, voltagecontrolled sub-THz oscillations of resonant tunneling diodes implemented with AIII-BV semiconductor heterostructures and integrated with slot antennas were recently evidenced experimentally. 15 The tunability occurs in this case due to the variation of the capacity of the resonant tunneling diode. In contrast, we show that in substrateless gated CNTs several NDC reg...

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Band structure of platinum from angle resolved photoemission experiments

Cited by 42 publications

References 14 publications

Chemisorption of Organics on Platinum. 1. The Interstitial Electron Model

Chemisorption of Organics on Platinum. 1. The Interstitial Electron Model

Spin–orbit-induced photoelectron spin polarization in angle-resolved photoemission from both atomic and condensed matter targets

Voltage-controlled high-frequency oscillations based on suspended semiconducting carbon nanotubes

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