Electronic Structure of δ-Pu and PuCoGa5 from Photoemission and the Mixed Level Model

2003 ◽  
Vol 802 ◽  
Author(s):  
John J. Joyce ◽  
John M. Wills ◽  
Tomasz Durakiewicz ◽  
Elzbieta Guziewicz ◽  
Martin T. Butterfield ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Fermi Level ◽  
Electronic Properties ◽  
Excellent Agreement ◽  
Fermi Energy ◽  
Photoelectron Spectroscopy ◽  
Spectral Intensity ◽  
Δ Phase ◽  
Level Model ◽  
Photoemission Data

ABSTRACTThe electronic structure of δ-phase Pu metal and the Pu-based superconductor PuCoGa5 is explored using photoelectron spectroscopy and a novel theoretical scheme. Excellent agreement between calculation and experiment defines a path forward for understanding electronic structure aspects of Pu-based materials. The photoemission results show two separate regions of 5f electron spectral intensity, one at the Fermi energy and another centered 1.2 eV below the Fermi level. A comparison is made between the photoemission data and five computational schemes for δ-Pu. The results for δ-Pu and PuCoGa5 indicate 5f electron behavior on the threshold between localized and itinerant and a broader framework for understanding the fundamental electronic properties of the Pu 5f levels in general within two configurations, one localized and one itinerant.

Electronic Structure and Surface Science of delta Plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
M. Butterfield ◽  
T. Durakiewicz ◽  
E. Guziewicz ◽  
J. J. Joyce ◽  
D. P. Moore ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Laser Ablation ◽  
High Resolution ◽  
Valence Band ◽  
Surface Science ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Instrument Resolution ◽  
Δ Phase

AbstractHigh resolution photoelectron spectroscopy (PES) studies were conducted on a δ-phase Plutonium sample cleaned by laser ablation and gas dosed with O2 and H2. The measurements were made with an instrument resolution of 60 meV and with the sample at 77 K. The PES data strongly support a model with Pu2O3 growth on the metal and then PuO2 growth on the Pu2O3 layer at this temperature. In vacuum, the PuO2 reduces to Pu2O3 at room temperature with a pressure of 6×10−11 Torr. In the case of H2 dosing the hydrogen appears to penetrate the surface and disrupt the valence band as evidenced by a drop in intensity of the peak at EF which is not accompanied by a drop in the main 5f manifold at ∼2eV.

Sheet Density and Well Thickness Effects on Photoluminescence from Pseudomorphic HEMT Structures

1988 ◽  
Vol 144 ◽  
Author(s):  
C. Colvard ◽  
N. Nouri ◽  
H. Lee ◽  
D. Ackley
Keyword(s):  
Low Temperature ◽  
Quantum Well ◽  
Fermi Level ◽  
Excellent Agreement ◽  
Fermi Energy ◽  
Carrier Density ◽  
Two Dimensional ◽  
Fermi Edge ◽  
Low Temperature Photoluminescence ◽  
Sheet Density

ABSTRACTLow temperature photoluminescence was studied in a large number of pseudomorphic HEMT's having an InxGa1−xAs quantum well. The spectra show strong qualitative differences when the Fermi level is above or below the second conduction subband, and in the latter case they are power dependent. A slight enhancement is seen at the Fermi edge only when it lies close to the higher subband. Excellent agreement is found between the measured Fermi energy and the two-dimensional carrier density in the well.

Electronic Properties of Chemically Etched CdTe Thin Films: Role of Te for Back-Contact Formation

2001 ◽  
Vol 668 ◽  
Author(s):  
D. Kraft ◽  
A. Thiβen ◽  
M. Campo ◽  
M. Beerbom ◽  
T. Mayer ◽  
...  
Keyword(s):  
Fermi Level ◽  
Electronic Properties ◽  
Photoelectron Spectroscopy ◽  
Valence Band Maximum ◽  
Ex Situ ◽  
Back Contact ◽  
Experimental Conditions ◽  
Band Bending ◽  
Fermi Level Position ◽  
Contact Formation

ABSTRACTImprovement of electric back contact formation is one of the major issues of the CdTe thin film solar cell research. Chemical etching of CdTe before metallization is accepted to improve contact formation. It is believed that a CdTe/Te contact is formed by this procedure leading to a Fermi level position in the CdTe close to the valence band maximum for low contact resistance. We have studied the electronic properties of chemically etched CdTe surfaces with photoelectron spectroscopy. Etching of the samples was performed in air (“ex-situ“) as well as in an electrochemical setup directly attached to the UHV system (“in-situ“). The formation of a Te layer is clearly shown by (S)XPS. In contrast to previous studies we could not detect the formation of a p-CdTe surface for different experimental conditions. The detected Fermi level position indicates still band bending and hence a blocking Schottky barrier.

scholarly journals Electronic Structure, Localization and 5f Occupancy in Pu Materials

2012 ◽  
Vol 1444 ◽  
Author(s):  
Miles F. Beaux ◽  
John J. Joyce ◽  
Tomasz Durakiewicz ◽  
Kevin S. Graham ◽  
Eric D. Bauer ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Fermi Energy ◽  
Photoelectron Spectroscopy ◽  
Electronic Configuration ◽  
Multiplet Structure ◽  
Temperature Dependent ◽  
Small Component ◽  
Narrow Peak ◽  
Valence Electronic Structure

ABSTRACTThe electronic structure of delta plutonium (δ-Pu) and plutonium compounds is investigated using photoelectron spectroscopy (PES). Results for δ-Pu show a small component of the valence electronic structure which might reasonably be associated with a 5f6 configuration. PES results for PuTe are used as an indication for the 5f6 configuration due to the presence of atomic multiplet structure. Temperature dependent PES data on δ-Pu indicate a narrow peak centered 20 meV below the Fermi energy and 100 meV wide. The first PES data for PuCoIn5 indicate a 5f electronic structure more localized than the 5fs in the closely related PuCoGa5. There is support from the PES data for a description of Pu materials with an electronic configuration of 5f5 with some admixture of 5f6 as well as a localized/delocalized 5f5 description.

Localized and Itinerant States in Pu Materials

2005 ◽  
Vol 893 ◽  
Author(s):  
John Joyce ◽  
J.M. Wills ◽  
T. Durakiewicz ◽  
M.T. Butterfield ◽  
E. Guziewicz ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Photoelectron Spectroscopy ◽  
The Other ◽  
Computational Results ◽  
Additional Insight ◽  
Dual Nature ◽  
Conduction Electrons ◽  
Delta Phase ◽  
Level Model ◽  
5F Electrons

AbstractThe electronic structure of Pu materials is examined using photoelectron spectroscopy. For delta-phase Pu metal as well as PuCoGa5 and PuIn3, the 5f electrons appear to be at the threshold between localized and itinerant character. A mixed level model computational scheme is used which results in non-magnetic solutions for the electronic structure and agrees well with the photoemission measurements. Several other computational schemes are assessed against photoemission results for delta Pu. Additional insight is provided by O2 and H2 dosing of the delta Pu samples and consideration of surface effects. The experimental and computational results are consistent with the 5f electrons in Pu materials exhibiting a dual nature with some fraction of the 5f levels localized and not participating in the bonding while the other fraction of 5f character is involved in bonding and hybridization with the conduction electrons.

Electronic Structures

2003 ◽  
Author(s):  
Toshiaki Enoki ◽  
Morinobu Endo ◽  
Masatsugu Suzuki
Keyword(s):  
Electronic Structure ◽  
Electronic Properties ◽  
Graphene Sheet ◽  
Fermi Energy ◽  
Reciprocal Lattice ◽  
Tight Binding ◽  
Electron System ◽  
Interlayer Interaction ◽  
Binding Model ◽  
Weak Interlayer

In the structure of graphite, graphene hexagon sheets are stacked in an AB stacking mode as shown in Figure 1.3. Such as mode is characterized by strong in-plane C-C bonds and weak interlayer interaction. This structural feature imparts two-dimensionality to its electronic structure. In the in-plane hexagon carbon network, the combination of sp2 σ- and π-bonds is the origin of the strong intralayer interaction, while the overlap of π-bonds between adjacent graphene sheets contributes to the weak interlayer interaction. In discussing the electronic properties around the Fermi energy, which is particularly important for the electronic structure of GICs, the π-electron orbitals play an essential role, giving graphite its unique properties. On the other hand, σ-bands, which have larger energy than π-bands, are located far from the Fermi energy. Thus they do not contribute to any serious change in the electronic properties when intercalates are introduced in the graphitic galleries. Here, we start with the electronic structure of graphite on the basis of the tight binding model. The discussion is first devoted to a graphene sheet, which is considered to be an infinite 2D hexagonal conjugated π-electron system (Wallace, 1947). Figure 5.la presents a unit cell of graphene sheet comprising two kinds of carbon atoms, α and β, where τ2 is the vector connecting the two atoms. The corresponding Brillouin zone in the reciprocal lattice is shown in Figure 5.1b.

Electronic Properties of Thin PD Overlayers on Au(111): Relationship to Chemisorption Properties

1985 ◽  
Vol 47 ◽  
Author(s):  
Xinyin Shena ◽  
D. J. Frankel ◽  
J. Hermanson ◽  
G. J. Lapeyre ◽  
R. J. Smith
Keyword(s):  
Electronic Structure ◽  
Single Crystal ◽  
Electronic Properties ◽  
Fermi Energy ◽  
Chemical Properties ◽  
Multilayer Films ◽  
State Density ◽  
Photoemission Spectroscopy ◽  
Co Chemisorption ◽  
And Chemical Properties

ABSTRACTWe present results for the electronic structure and chemical properties of thin Pd films grown epitaxially on Au(lll) single-crystal substrates. Photoemission spectroscopy is used to monitor the development of the Pd d-bands near the Fermi energy (EF ) as a function of overlayer thickness. The state density aF E is relatively small for the single Pd monolayer (ML), but increases monotonically with overlayer thickness, resembling the bulk Pd electronic structure for films thicker than 5 ML. At the same time we observe that the 1 ML Pd film is iner with respect to CO chemisorption, while the multilayer films readily chemisorb CO, similar to bulk Pd. We examine possible models for the inert behavior of the Pd monolayer, based on related slab calculations which show the substrate-induced modification of the electronic structure in the overlayer.

ELECTRONIC STRUCTURE OF ASSEMBLED CLUSTERS WITHIN THE STABILIZED JELLIUM MODEL

1996 ◽  
Vol 03 (01) ◽  
pp. 1001-1006
Author(s):  
HENRIK GRÖNBECK ◽  
ARNE ROSÉN
Keyword(s):  
Electronic Structure ◽  
Binding Energy ◽  
Fermi Level ◽  
Electronic Properties ◽  
Closed Shell ◽  
Building Blocks ◽  
Jellium Model

The electronic structure of assembled closed shell clusters have been analyzed using a spherical, stabilized jellium description of the clusters. The effects of including stabilization terms to the jellium model were investigated by calculating the properties of cluster dimers, (Na20)2 and ( Cu 20)2. In addition, the electronic properties of a material consisting of closed shell Al 12X clusters, where X is C or Si, were investigated using a model of six clusters. The large gap at the Fermi level present for the building blocks was also found to appear for the cluster-assembled material. The binding energy of the clusters in the cluster-assembled material was compared with that of an atomic Al lattice.

Electronic structure of Ti-doped Sr4Sc2Fe2As2O6 as a possible parent phase for the new FeAs superconductors

Open Physics ◽  
2010 ◽  
Vol 8 (3) ◽  
Author(s):  
Igor Shein ◽  
Alexander Ivanovskii
Keyword(s):  
Electronic Structure ◽  
Fermi Level ◽  
Electronic Properties ◽  
Parent Phase ◽  
Oxide Phase ◽  
Sharp Contrast ◽  
First Principle ◽  
Ti Doping ◽  
Feas Based Superconductors ◽  
Feas Superconductors

AbstractFirst principle FLAPW-GGA calculations have been performed with the purpose to understand the effect of Ti-doping on the electronic properties for the newly discovered tetragonal iron arsenide-oxide Sr4Sc2Fe2As2O6 (abbreviated as FeAs42226) as the possible parent phase for the new FeAs superconductors. Our results show that the insertion of Ti into Sc sublattice of this five-component iron arsenide-oxide phase leads to the resolute change of electronic structure of FeAs42226. Namely, the insulating oxygen-containing [Sr4Sc2O6] blocks in Ti-doped FeAs42226 became conducting, and this differs essentially from the known picture for all others FeAs superconductors where the conducting [Fe2As2] blocks are alternated with insulating blocks. Moreover in sharp contrast with FeAs-based superconductors with Fe 3d bands near the Fermi level, for Ti-doped FeAs42226 in this region the Ti 3d states are dominated, whereas the Fe 3d states are suppressed.

Ab Initio Calculations of Electronic Properties of Al Doped LaMnO3 Perovskite Manganites

2015 ◽  
Vol 754-755 ◽  
pp. 762-765
Author(s):  
A. Chik ◽  
S. Saad ◽  
R.M. Zaki ◽  
F. Che Pa ◽  
C.K. Yeoh
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Fermi Level ◽  
Ab Initio ◽  
Electronic Properties ◽  
Density Functional ◽  
Perovskite Manganites ◽  
Functional Theory ◽  
Temperature Range ◽  
Energy Approximation

The electronic structure of the perovskite manganites LaMnO3 and La2/3 Al1/3 MnO3 was presented. The calculations were made within density functional theory (DFT) and PBE exchange correlations energy approximation. It was found that inclusion of Al dopants add additional states near the Fermi level and decreasing the resistivity values for all temperature range.

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