Electron energy bands in semiconductor films

The possible nature of the band structure in crystal films is examined on the basis of a consideration of the symmetry possessed by their structure.For germanium and silicon of the p- and n-types with various different orientations of the film the connection is found between the band structures of the film and of the bulk crystal. The result is obtained that with the orientation [111] an n-germanium film, like an n-silicon film with the same orientation must have a single-trough minimum.     

High spin bands in120Xe

High spin states in¹²⁰Xe were populated in the reaction¹⁰⁶Cd(¹⁸O, 4n) at a bombarding. energy of 90 MeV and the subsequent de- excitation was studied using γ- ray spectroscopic methods. New levels and several. spin and parity. assignments were established. The yrast band was observed up to theK ^π=22⁺state with two band crossins athw _c=0.39MeV and 0.45Mev Negative parity levels and a new positive parity band were also identified.     

Phenomenological electronic energy bands in graphite intercalation compounds

The electronic energy bands near the Fermi level for both donor and acceptor graphite intercalation compounds are modelled using a k_z-axis zone folded form of the SWMcC bands for pristine graphite. The effect of intercalation is included through terms for the intercalant and for the interaction between intercalant and graphite layers. Graphitic π-bands appropriate to both donor and acceptor compounds are presented.     

Scattering by Cu adatoms between image-potential bands on Cu(001)

With the increasing resolution and sensitivity of photoelectron spectroscopy, the influence of defects is becoming more and more obvious. Scattering processes induced by adsorbate atoms can be studied by time- and angle-resolved two-photon photoemission. We have examined the dynamics of electrons in image-potential states on the Cu(001) surface for statistically distributed Cu adatoms and have identified different scattering mechanisms. Scattering of electrons from the second (n=2) to the bottom of the first (n=1) image-potential band is observed, which we attribute to inelastic interband scattering with electrons in the bulk. At energies above the bottom of the n=2 band, resonant interband scattering from the n=2 to the n=1 image-potential band is found. The rate for these processes can be determined by modeling the time-resolved measurements via optical Bloch equations of a four-level system. Comparison of the transition and decay rates reveals that the decay rate of the n=2 electrons is almost exclusively changed by additional resonant interband-scattering processes upon adsorption. PACS 73.20.At; 79.60.Ht; 68.49.Jk     

Electronic energy bands in model three dimensional lattices

The paper presents a discussion of the energy bands in a three dimensional lattice in which the potential is assumed to have a constant nonvanishing value in a spherical region round each nucleus and vanishes in the interspace. Introducing some simplifying approximations, a relation between the electronic energy and the wave vector is obtained. The case of an ordered diatomic alloy is next considered and the splitting of the bands for such a lattice is clearly brought out. The significance of this result in the theory of antiferromagnetism is pointed out. Lastly it is noted that for our model alloy, the theorem enunciated bySaxon andHütner is valid.     

On two dimensional energy bands in organic materials

It is shown that the high trap densities associated with many organic materials may lead to the presence of trap energy bands similar to impurity bands in semiconductors. The possibility of a (high) two dimensional conductivity in certain materials is discussed.     

On the nature of energy bands in tetracyanoplatinates

Optical data and band calculations are presented for a series of tetracyanoplatinates with varying Pt—Pt-distance R. The band gap energies decrease according to R^-3 with decreasing R. The energy bands which determine the optical and electrical properties for E6 c originate from (Pt5d_z², 6s) and (Pt6p_z, CNπ¹) hybrid molecular states.     

High Miller-index photonic bands in synthetic opals

We present a detailed study of high Miller-index (h k l) photonic bands in a-SiO₂ synthetic opals. Polarized light transmission spectra of opals were studied in a wide wavelength range for all high symmetry directions on the Brillouin zone (BZ) in the face-centered cubic (fcc) lattice. It is shown that under the conditions of low dielectric contrast the dispersion of high Miller-index photonic bands is described well by the calculated dependences of Bragg wavelengths diffracted from the (h k l) crystallographic planes of the fcc lattice.     

High spin rotational bands in 65Zn

The nucleus ₃₀ ⁶⁵ Zn was studied using the ⁵²Cr(¹⁶O, 2pn)⁶⁵Zn reaction at a beam energy of 65 MeV. The level scheme is extended up to an excitation energy of 10.57 MeV for spin-parity (41/2?) with several newly observed transitions placed in it.     

Third neighbor linear-combination-of-atomic-orbitals energy bands of zincblende

It is shown that inclusion of third nearest neighbor interactions and omission of the usual two center approximation in the simplified Slater-Koster LCAO method leads to an improved interpolation formula for the energy bands of wide bandgap partially ionic II–IV compounds such as zinc sulfide.     

The absolute positions of calculated energy bands

The absolute positions of calculated crystalline energy bands depend upon the choice of charge cluster used to generate the total crystalline charge for the coulomb potential calculation. The coulomb potential (and hence the bands) will be shifted from the Ewald limit by 2π times the trace of the second moment tensor of the charge cluster divided by three times the volume of the unit cell. Energy bands obtained from different calculational models can thus all be corrected to the same Ewald limit. Energy bands can also be aligned more realistically with those in a finite crystal by calculating the shift in the bands from the Ewald limit due to a free atom or ion surface charge density.     

Conduction bands and invariant energy gaps in alkali bromides

Electronic structure calculations of the alkali bromides LiBr, NaBr, KBr, RbBr and CsBr are reported. It is shown that the conduction band has primarily bromine character. The size of the band gaps of bromides and alkali halides in general is reinterpreted. Received: 26 January 1998 / Revised: 16 March 1998 / Accepted: 23 March 1998     

One-dimensional 3d electronic bands of monatomic Cu chains

The electronic structure of an array of monatomic Cu chains grown on the Pt(997) surface has been examined by angle-resolved photoemission. The monatomic wires exhibit properties associated with 3d electron confinement in one dimension. Along the wire direction, the 3d bands states display a dispersive character, with periodicity in reciprocal space defined by the wire array geometry. These observations are compared and analyzed with ab initio calculations based on the full-potential linearized augmented plane-wave method.     

High energy x-ray satellites ofL 2,3 emission bands of Na,Mg, Al,and Si

The x-ray satellites found on the high energy sides of theL _2,3 emission bands of Na, Mg, Al, and Si have previously been attributed to the radiative decay of double ionization states. However, in some recent papers it has been proposed that the satellites in Al and Si may arise from the simultaneous radiative decay of a core ionization state and a volume plasmon. A detailed investigation of the high energy satellites of theL _2,3 x-ray emission bands of Na, Mg, Al, and Si have been made for incident electron energies from 500 eV to 5 keV and the results compared with the double ionization theory. Plasmon involvement is also considered. The present results lend additional support to the first interpretation; namely, that the satellites arise from the radiative decay of atoms with a double vacancy in theL _2,3 (2p) shell and not from the plasma phenomenon.     

Strain-split energy bands and piezooptical properties of Si

The energy bands of a crystal of Si under an axial force are calculated using a pseudopotential method including spin-orbit coupling effects. Good numerical agreement with experimentally determined deformation potentials is obtained. The wavelength modulated reflectivity spectra for several uniaxial forces along the [001] and [111] directions are calculated and compared with available experiments. The structure of the spectra is analyzed in terms of the shifts and splittings of the energy bands. It is shown that the optical structure corresponding to the main peak in reflectivity around 3·4 eV is due to transitions associated with several initial points related to the A line and it is well reproduced by an energy band model where the energy value of the L₃—L₁ transition is slightly larger than that corresponding to the Γ_25′–Γ₁₅ one.     

Magnetic quantization of the energy states in heavily doped semiconductors with nonparabolic energy bands

A formula for carrier concentration, and a relationship between mobility and diffusivity, have been presented for degenerate semiconductors with a nonparabolic energy band structure under the influence of a magnetic field. The relationships are general; they involve no approximation related to the comparative values of energy bandgap and spin orbit coupling. They should therefore, be applicable to both non-degenerate and degenerate semiconductors. They are quite suitable for the investigation of electrical transport in heavily doped semiconductors under the influence of a magnetic field. PACS 72.20.-I; 73.50.-h     

Excitation energy dependence of Raman bands in multiwalled carbon nanotubes

Vertically aligned multiwalled carbon nanotubes (MWCNTs) were grown on 1‐ and 3‐nm cobalt (Co) films, at various growth times by microwave plasma enhanced chemical vapor deposition technique and their microstructural properties were analyzed with the help of Raman spectra that were obtained from different sources of laser excitation energies (E_L: 2.41, 1.96 and 1.58 eV). The variation of D and G band positions in MWCNTs grown on 1‐ and 3‐nm Co films follows a similar behavior, and an anomalous behavior was observed in the E_L dependence of the D′‐band wavenumber. In the second‐order spectra, the G′ band varied strongly according to structure with the laser excitation energy (E_L). The I_D/I_G ratio decreased with the increase of E_L for all MWCNTs; however, for a fixed E_L, the I_D/I_G dispersion is higher at lower E_L. The crystallite sizes were estimated using I_DI_G and E_L. We have shown that, for all MWCNTs, I_D/I_G ratio is inversely proportional to . Copyright © 2010 John Wiley & Sons, Ltd.