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1.
U. Schwingenschlögl C. Schuster 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):409-411
By means of band structure calculations within the density functional
theory and the generalized gradient approximation, we investigate the
electronic structure of self-organized Pt nanowires on the Ge(001) surface.
In particular, we deal with a novel one-dimensional surface state confined
in the nanowire array and clarify its origin. Due to large Pt contributions,
the novel state is rather a mixed Ge–Pt hybrid state than a confined Ge
surface state. Moreover, we compare our results to data from scanning
tunneling microscopy. 相似文献
2.
A.M. Mazzone 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):407-412
Full-potential Linearized Augmented Plane Wave calculations are performed to investigate the properties of the electronic
charge of metallic multilayers formed by non-magnetic and magnetic elements (i.e. Ag, Cu and Fe). The multilayer structure is of the type An, A
n
B
n or (AB)n where A, B indicate Ag, Cu and Fe and n is the number of layers of the element A or B. The problem addressed by this study is the transition from the 2D behavior of the isolated monolayer to the 3D bulklike
character. Therefore the calculations, carried out at paramagnetic level, illustrate the dependence of the density of states
on the multilayer thickness and composition. For the three elements the main feature of the inter-layer coupling is the absence
of charge intermixing and hybridization. For structures with a number of layers n? 5 the density of states bandwidth has a decrease, with respect to the bulk value, approximately proportional to the reduced
coordination. At the critical thickness n = 5 and above, a noticeable difference exists between the charge in the outer layers, with reduced coordination and bandwidth,
and the central layers with a bulklike density of states. Averaging between these contributions leads to the re-installment
of bulklike properties. These results are in essential agreement with analytical band theories and quantum mechanical calculations
for similar systems and with experiments.
Received 3 October 2001 相似文献
3.
Y. P. Chen Y. E. Xie X. H. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):333-338
We have studied the transmission resonances for a confined array of
antidots, using the lattice Green's function method. Two kinds of resonant
peaks via quasibound states are found. One kind of resonant peak corresponds
to the split quasibound states. The split states originate from the
superposition of quasibound states respectively localized in different (T or
crossed) junctions, while the number of quasibound states in each junction
is associated with the arm-width of the junction. Electrons in these split
states are mainly localized in the junctions. The other kind of resonant
peaks correspond to the high quasibound states which exist in (transverse
and longitude) multi-period confined arrays of antidots. It is interesting
to note that electrons in some of the high quasibound states are mainly
localized in the intersection of the junctions rather than in the junctions
themselves. 相似文献
4.
Hideo Kaiju Mao NishiyamaYuki Otaka Naoaki SakaguchiKazuo Shiiki 《Journal of magnetism and magnetic materials》2006
The oxidation states of Al-oxide layer and the leakage current density in coercive differential spin tunneling junctions Co/Al-oxide/Co have been investigated in order to clear the mechanism of the increasing resistance change. X-ray photoelectron spectroscopy analysis shows that the resistance change increases with decreasing unoxidized Al, which can be qualitatively explained by using first-principle band calculation based on linear-muffin-tin-orbital atomic-sphere-approximation method. The resistance change decreases with increasing leakage current density, which originates from Schottky effect. Reduction of unoxidized Al and leakage current density originating from Schottky effect is required to obtain the large resistance change in spin tunneling junctions. 相似文献
5.
Rastei MV Heinrich B Limot L Ignatiev PA Stepanyuk VS Bruno P Bucher JP 《Physical review letters》2007,99(24):246102
Low-temperature scanning tunneling spectroscopy over Co nanoislands on Cu(111) showed that the surface states of the islands vary with their size. Occupied states exhibit a sizable downward energy shift as the island size decreases. The position of the occupied states also significantly changes across the islands. Atomic-scale simulations and ab initio calculations demonstrate that the driving force for the observed shift is related to size-dependent mesoscopic relaxations in the nanoislands. 相似文献
6.
C. L. Lu C. P. Chang M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):161-169
In this study, we apply the tight-binding method to
magneto-electronic properties of the AA- and ABC-stacked graphites,
which are strongly dependent on the interlayer interactions, the
magnetic field, and the stacking sequences. First of all, the
interlayer interactions induce the significant changes in the energy
dispersions, the band symmetry about the Fermi level, the overlap
between valence and conduction bands, the band width, and the
band-edge states or the symmetry points. Then, the magnetic field
induces the Peierls phase in the Bloch functions and thus strongly
affects the energy dispersions of the Landau Levels, the subband
spacings, the energy width, and the special structures in density of
states (DOS). Finally, the stacking sequences dominates over the
low-energy band overlap and the anisotropy of energy bands. The
effects mentioned above are exactly reflected in the density of
state. Here, DOS exhibits the 3D, 2D, and 1D characteristics. 相似文献
7.
8.
W. Müller R. Schiller W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):705-718
The aim of this work is to find a simple analytic model to explain some principal aspects of the behavior of surface states
in correlated electron systems. We start from the analytic expression for the Green function of the semi-infinite tight binding
linear chain. This Green function in case of modification of the center of gravity of the first atom and the change in coupling
between the first and the second atom is evaluated as an exact analytic expression. Conditions for the existence and classification
of surface states are given. The spectral weight of surface states and the local density of states are evaluated. The method
is applied to a s.c. (100) surface of a local moment crystal. Conditions for the existence of surface states are derived and
their locations in the Brillouin zone are predicted. It is shown that it is possible to include correlation effects within
the framework of the discussed model. The comparison with former numerical results is performed.
Received 8 March 2000 相似文献
9.
R. Schiller W. Müller W. Nolting 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(2):249-257
The electronic quasiparticle structure of a ferromagnetic local moment film is investigated within the framework of the s-f
model. For the special case of a single electron in an otherwise empty energy band being exchange coupled to a fully ordered
localised spin system the problem can be solved exactly and, for the spin- electron, some marked correlation effects can be found. We extend our model to incorporate the influence of the surface on
the electronic structure. Therefore we modify the hopping integrals in the vicinity of the surface. This leads to the existence
of surface states, both for the spin- and the spin- spectral density of states. The interplay between the modification of the hopping integrals and the existence of surface
states and correlation effects is discussed in detail.
Received: 22 September 1997 / Revised: 12 December 1997 /
Accepted: 15 December 1997 相似文献
10.
A model is proposed that treats electrons at surfaces as a combination of two-dimensional and three-dimensional degrees of
freedom. This yields a simple formula for the surface state induced resonant enhancement of the transfer of electrons through
a surface. The model also yields analytic approximations for the transition between two-dimensional and three-dimensional
distance laws in the correlations between electrons in surface states.
Received 6 August 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: rainer@sask.usask.ca 相似文献
11.
S. Bhattacharjee S. M. Jaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):305-311
The influence of correlation and temperature on the electronic structure of bulk and
thin film GdN
has been studied using the s-f model, which combines
the one electron band structure with a many body procedure.
The tight binding linear muffin tin orbital (TB-LMTO) method was used to obtain
the one electron band structure of
the system. The s-f exchange coupling constants
for each band were obtained from the spin polarized band structure of
the system using a mean field model.
Correlation effects are found to be present in the system. However they
are not sufficiently strong to cause a correlation induced splitting in the
spectrum. Some bands of the thin films of GdN exhibit splitting at T=Tc
and it is due to the combined effect
of correlation and temperature. The conduction bands of both the bulk and
the thin films of GdN exhibit a red shift with respect to temperature. 相似文献
12.
J. Jalkanen O. Trushin E. Granato S. C. Ying T. Ala-Nissila 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):175-183
We study the equilibrium shape, shape transitions and optimal size
of strained heteroepitaxial nanoislands with a two-dimensional
atomistic model using simply adjustable interatomic pair potentials.
We map out the global phase diagram as a function of
substrate-adsorbate misfit and interaction. This phase diagram
reveals all the phases corresponding to different well-known growth
modes. In particular, for large enough misfits and attractive
substrate there is a Stranski-Krastanow regime, where nano-sized
islands grow on top of wetting films. We analyze the various terms
contributing to the total island energy in detail, and show how the
competition between them leads to the optimal shape and size of the
islands. Finally, we also develop an analytic interpolation formula
for the various contributions to the total energy of strained
nanoislands. 相似文献
13.
A. Michel V. Pierron-Bohnes J.P. Jay P. Panissod S. Lefebvre M. Bessière H.E. Fischer G. Van Tendeloo 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):225-239
Epitaxial Co/Mn multilayers (0.75 to 6 nm Co, 0.4 nm Mn layer thickness) have been grown on mica substrates covered by a (0002)
Ru buffer layer. The structural properties of these layers have been studied using X-ray diffraction, nuclear magnetic resonance
(NMR), and high resolution transmission electron microscopy (HRTEM). The Co layers, grown as face centred cubic (fcc), were
found to be stabilised by the very thin Mn layers. Data obtained using X-ray diffraction and NMR were analysed and found to
be in good agreement, while Monte-Carlo simulations were used to interpret the data and calculate the expected diffracted
intensity and NMR spectra. The HRTEM data show that the Mn layers give rise to a large strain contrast extending, in the growth
direction, over a distance which exceeds the thickness of the Mn layers. The superlattices could be described as having an
fcc structure containing randomly located stacking faults with varying densities. The results verify the presence of a dominant,
almost perfect phase of fcc stacking, and of a faulted hcp phase, while the number of defects increases with the Co layer
thickness.
Received 27 October 1999 and Received in final form 29 May 2000 相似文献
14.
P. V. Aleksandrova V. K. Gueorguiev Tz. E. Ivanov S. Kaschieva 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(3):355-359
The influence of high energy electron (23 MeV) irradiation on the electrical
characteristics of p-channel polysilicon thin film transistors (PSTFTs) was
studied.
The channel 220 nm thick LPCVD (low pressure chemical vapor deposition)
deposited polysilicon layer was phosphorus doped by ion implantation. A 45 nm thick, thermally grown, SiO2 layer served as
gate dielectric. A self-alignment technology for boron doping of the source and drain regions was used. 200 nm thick polysilicon
film was deposited as a gate electrode.
The obtained p-channel PSTFTs were irradiated with different high energy
electron doses.
Leakage currents through the gate oxide and transfer characteristics of the
transistors were measured. A software model describing the field enhancement
and the non-uniform current distribution at textured polysilicon/oxide
interface was developed. In order to assess the irradiation-stimulated
changes of gate oxide parameters the gate oxide tunneling conduction and
transistor characteristics were studied. At MeV dose of 6×1013 el/cm2, a negligible degradation of the transistor properties was
found. A significant deterioration of the electrical properties of PSTFTs at
MeV irradiation dose of 3×1014 el/cm2 was observed. 相似文献
15.
Electronic properties of (Ag, Co) nanostructures grown on Au(1 1 1) vicinal surfaces have been studied by angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy and spectroscopy (STM/STS). The growth and self-assembling of Co and Ag nano dots on Au(7 8 8) surface are described. Co island growth leads to the formation of repulsive energy barriers for the surface state, and subsequently to the appearance of confined states in between each group of four Co dots. On the contrary, when Ag nano dots are grown, the potential barrier for the surface electrons is not enough to suppress their dispersive behavior. Nevertheless, inside Ag islands appear new quantized states whose energies can be tailored by varying the deposition rate of the adsorbate and/or the Miller index of the vicinal surfaces. In both systems, high homogeneity of the electronic properties is achieved over a macroscopic scale. 相似文献
16.
T. Matsuse T. Takizawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):49-52
The 3-dimensional Mesh-Hartree-Fock-Kohn-Sham (3D-MHFKS)
calculation is applied to study the magnetic (B-) field dependence of the electronic
structures of circular-shaped vertical quantum dot (Q-dot) with
electron number (N) in double
barrier structure (DBS) and also coupled double Q-dots in triple
barrier structure (TBS). One of the advantageous points of the
3D-MHFKS calculation is that the strength of coupling between
two dots are explicitly evaluated by introducing the realistic
barrier in TBS as a straightforward extension of 3D-MHFKS
calculation of the single Q-dot in DBS. The calculated chemical
potentials represented in B-N
phase diagram are consistently and systematically discussed by
showing the B-field
dependence of the occupied single particle energy levels from
the view point how the electronic states transfer sequentially
from Fock-Darwin (FD) to lowest Landau (LL) and from LL to the
spin flip (SF) and from SF to spin-polarized maximum density
droplet (MDD) domains as increasing B-field in the Q-dots. 相似文献
17.
18.
M. Saint Jean S. Hudlet C. Guthmann J. Berger 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):471-477
In triboelectric phenomena, electric charges are transferred when two materials are touched or rubbed together. We present
in this paper a study of this effect performed on metallic oxides at the nanometric scale by an Atomic Force Microscope in
the resonant mode. We show that following the electrification processes, positive or negative charges can be deposited. From
our experimental data, we conclude that the charge transfer results in an equilibrium final state, the occupied states in
the gap being “surface states” with large density and spread under the surface along a characteristic distance of about 100
nm.
Received 18 March 1998 and Received in final form 8 July 1998 相似文献
19.
A. Haran R. Naaman G. Ashkenasy A. Shanzer T. Quast B. Winter I.V. Hertel 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):445-451
Synchrotron radiation (SR) pulses are used to eject electrons from a gold substrate covered with organized organic thin films
(OOTF) in order to investigate their transmission probability through the OOTF as a function of the electron initial kinetic
energy. By variation of the SR photon energy within a few eV above the Au-4f binding energy levels we controlled the initial kinetic energy of the substrate electrons. The observed oscillations in the
transmission probability for porphyrin-based films as a function of the kinetic energy is argued to be due to effects of band
structure above the vacuum level in the well-ordered molecular adsorbate. We also present valence photoemission spectra (PES)
of different type OOTF and demonstrate how their coverage of the substrate affects the PES.
Received 24 July 1998 相似文献