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Tungsten diselenide (WSe2) was analyzed using x-ray photoelectron spectroscopy. A freshly exfoliated, oxygen-free flake was analyzed. Spectral regions for O 1s, W 4d, W 4f, W 5p, Se 3d and an extended region encompassing Se 3p, Se 3s, W 4d, Se LMM, and C 1s were acquired along with the valence band. Bulk quantitative analyses by x-ray fluorescence and x-ray diffraction indicated the material was stoichiometric and phase pure, respectively. [ABSTRACT FROM AUTHOR]

We have investigated optical properties and electrical properties of electrically degraded ZnSe layers by heavy Al doping, where their electron concentrations lie in the range of 7×1017–6×1018 cm-3. Low-temperature photoluminescence exhibits two dominant radiative trap centers of 1.97 eV (RD1) and 2.25 eV (RD2), which are ascribed to VZn-related complex defects. Deep-level-transient spectroscopy shows two electron-trap centers at 0.16 eV (ND1) and 0.80 eV (ND2) below the conduction-band minimum. On the other hand, it is found that RD2 is dominant in relatively lightly doped ZnSe:Al layers below 7×1018 cm-3 and RD1 is dominant in more heavily doped layers near 1×1019 cm-3, while ND1 and ND2 are independent of Al doping concentration and their trap densities are estimated be below 3×1016 cm-3. This indicates that RD1 and RD2 cause the carrier compensation in heavily doped ZnSe:Al layers. Their electron transport mechanism can be explained by ionized-impurity scattering mechanism. [ABSTRACT FROM AUTHOR]

Photon stimulated ion desorption and Auger decay spectra were measured for condensed thiophene around the S 1s-edge. Three kinds of ions, H+, S+, and S2+, were observed as main desorbed species. Partial ion yields (PIY) have been determined for these three fragment ions as a function of the photon energy. It was found that the indirect x-ray induced electron stimulated desorption mechanism plays an important role in H+ ion desorption. For S+ ion desorption, on the other hand, a pronounced enhancement at ∼3 eV away from the first core-to-valence resonance was observed in the PIY curve. On the basis of the results for the Auger decay spectra, the enhancement of S+ desorption at ∼3 eV away from the first resonance is interpreted in terms of the effective screening of positive holes due to the existence of Rydberg electrons. [ABSTRACT FROM AUTHOR]

Both p-type and n-type dilute-nitrogen GaNAs epitaxial layers grown by metal-organic chemical vapor deposition were characterized by deep-level transient spectroscopy (DLTS). For each case, the dominant DLTS signal corresponds to an electron trap having an activation energy of about 0.2–0.3 eV for p-type GaNAs and about 0.3–0.4 eV for n-type GaNAs. In p-type GaNAs, the electron traps fill slowly, as the DLTS signal reaches saturation using zero-bias filling pulses with widths of 1 s. The electron traps fill quickly in the n-type GaNAs, as the DLTS signal does not typically increase after the shortest fill time of 10 μs. The electron-trap densities are calculated using modeling that accounts for the spatial region where traps fill and emit during DLTS measurement. A set of p-type samples with mid-1016 cm-3 net acceptors has N content ranging from 0.02% to 1.2%, and the resulting electron-trap concentrations range from 1.4×1017 to 4.3×1017 cm-3. A set of n-type samples with mid-1017 cm-3 doping has N content ranging from 0.011% to 0.45%, and the resulting electron-trap concentrations range from 7.6×1014 to 3.6×1016 cm-3. Additionally, a set of p-type samples with ∼0.25% N content has hole concentrations ranging from 4.3×1016 to 1.3×1017 cm-3, and the resulting electron-trap concentrations increase with acceptor doping ranging from 3.1×1017 to 7.2×1017 cm-3. A set of n-type samples with ∼0.25% N content has electron concentrations ranging from 4.5×1016 to 7.8×1017 cm-3. The resulting electron-trap concentrations also increase with donor concentration from 5.7×1015 to 3.5×1016 cm-3. The modeling of the Poole-Frenkel effect predicts that the trap may be about 100 meV deeper than implied by the measured activation energies. [ABSTRACT FROM AUTHOR]

A single subband model for InAs/GaAs quantum dots (QDs) and quantum rings (QRs), where the energy dependence of the electron effective mass is defined by the Kane formula, is used. Model assumptions lead to the nonlinear Schrödinger equation in a three-dimensional space. Geometrical parameters of the model are based on the fabrication of QRs from a QD procedure for which the experimental capacitance-gate voltage (CV) data are available. The confinement state energies of QDs (QRs) are calculated. Obtained results for single electron energy levels reveal a good agreement with the CV spectroscopy experiments. [ABSTRACT FROM AUTHOR]

Presents a novel method for determining the K-electron absorption edge of heavy elements using continuous bremsstrahlung radiation produced by a weak beta source. Recording of the spectrum of radiation transmitted through an elemental target; Identification of the sharp discontinuity observed in the spectrum as the absorption-edge energy.

[formula] cleavage surfaces were investigated by cross-sectional scanning tunneling microscopy and spectroscopy combined with calculations of the tunnel current. The different contributions to the tunnel current and their origins are determined by comparison of the experimental results with calculated tunnel currents for both pinned and unpinned GaN surfaces. It is found that both the N and Ga derived intrinsic dangling bond surface states are outside of the fundamental band gap and lead to electron tunneling out of the valence and into the conduction band, respectively. The band edges of both intrinsic surface states are located at the [formula] point of the surface Brillouin zone. The observed Fermi level pinning 1.0 eV below the conduction band edge is attributed to the high defect density at the surface, but not to intrinsic surface states. The defects give rise to a current due to electrons tunneling out of the defect states within the band gap. [ABSTRACT FROM AUTHOR]