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ABSTRACT: Angle-resolved photoemission spectroscopy reveals the presence of a two-dimensional electron gas at the surface of In_{2}O_{3}(111). Quantized subband states arise within a confining potential well associated with surface electron accumulation. Coupled Poisson-Schrödinger calculations suggest that downward band bending for the conduction band must be much bigger than band bending in the valence band. Surface oxygen vacancies acting as doubly ionized shallow donors are shown to provide the free electrons within this accumulation layer. Identification of the origin of electron accumulation in transparent conducting oxides has significant implications in the realization of devices based on these compounds.
Physical Review Letters 02/2013; 110(5):056803. · 7.37 Impact Factor
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F Offi,
P Vilmercati,
L Petaccia, S Gorovikov,
A Ruocco,
M I Trioni,
A Rizzo,
A GOLDONI,
G Stefani,
G Panaccione,
S Iacobucci
Physical Review B 01/2012; 85:-. · 3.69 Impact Factor
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ABSTRACT: Photoelectron emission spectra in a photon energy range between 7.5 and 21 eV are measured for in situ grown polycrystalline Yb films. By comparing bulk and surface core level shifted 4f components we give an estimation of the effective attenuation length (EAL) for low energy (6-20 eV) electrons in Yb, establishing a moderate increase of the EAL upon electron energy decrease. The experimental EAL data are found to be a factor of four smaller than those predicted from the so-called 'universal curve'.
Journal of Physics Condensed Matter 08/2010; 22(30):305002. · 2.55 Impact Factor
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Physical Review B 01/2010; 82:-. · 3.69 Impact Factor
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F Rodolakis,
B Mansart,
E Papalazarou, S Gorovikov,
P Vilmercati,
L Petaccia,
A Goldoni,
J P Rueff,
S Lupi,
P Metcalf,
M Marsi
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ABSTRACT: We present an angle resolved photoemission study of V2O3, a prototype system for the observation of Mott transitions in correlated materials. We show that the spectral features corresponding to the quasiparticle peak in the metallic phase present a marked wave vector dependence, with a stronger intensity along the GammaZ direction. The analysis of their intensity for different probing depths shows the existence of a characteristic length scale for the attenuation of coherent electronic excitations at the surface. This length scale, which is larger than the thickness of the surface region as normally defined for noncorrelated electronic states, is found to increase when approaching the Mott transition. These results are in agreement with the behavior of quasiparticles at surfaces as predicted by Borghi et al.
Physical Review Letters 03/2009; 102(6):066805. · 7.37 Impact Factor
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ABSTRACT: Vicinal Rh(111) surfaces are studied with high resolution core level photoemission. We demonstrate the possibility to distinguish between the different kinds of surface atoms on these surfaces by virtue of their 3d core level binding energies. In particular, the low coordinated step atoms are found to exhibit a clear fingerprint in Rh 3d spectra. We demonstrate how this may be used to show that initial oxygen adsorption occurs on the steps and not on the terraces of the vicinal surfaces.
Physical Review Letters 09/2003; 91(5):056102. · 7.37 Impact Factor
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ABSTRACT: At the Elettra synchrotron light laboratory, a new undulator-based beamline with photon energy ranging from about 4.6 to 40 eV has been installed and opened to users. The beamline, based on a 4 m normal-incidence monochromator (NIM) with spherical gratings and movable exit slit, serves an end station to perform primarily high-resolution angle-resolved photoemission spectroscopy experiments in the low photon energy regime. The salient features of the instrument and some of the commission data are reported in this paper.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 606(3):780-784. · 1.21 Impact Factor
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B. Mansart,
V. Brouet,
E. Papalazarou,
M. Fuglsang Jensen,
L. Petaccia, S. Gorovikov,
A. N. Grum-Grzhimailo,
F. Rullier-Albenque,
A. Forget,
D. Colson,
M. Marsi
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ABSTRACT: We report a high-momentum and energy resolution angle-resolved photoemission study of superconducting Ba(Fe1-xCox)2As2. Polarization-dependent measurements performed at low photon energy along high-symmetry directions in the Brillouin zone made it possible to get new insight into the role of the five Fe 3d orbitals in the complex electronic structure of this compound close to the Fermi level, in particular, into the nature of the holelike pockets. Two distinct inner α pockets could be disentangled, suggesting that their origin is probably due to hybridized dxz and dyz. We also show that the complex outer β pocket is mainly of dz2 nature, with contributions of other orbitals of different symmetry only in specific points of the Brillouin zone, in the proximity of the kz=1 [4π/c] plane. The identification of a dz2 nature for β contributes to our understanding of the role of electron correlations in 122 pnictide superconductors and of the enhancement of the three-dimensional character of the Fermi surface in Co-doped compounds.
Phys. Rev. B. 83(6).
