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We study the Casimir force F between two parallel anti-ferromagnetic slabs taking into account an external magnetic field in the Voigt configuration. Using a frequency and magnetic field dependent magnetic permeability tensor and a frequency independent dielectric permittivity, to describe the slabs, we calculate the Casimir force using non-normal incidence reflectivity of the electromagnetic waves in the free space between the slabs. We determine the Casimir force by performing two-dimensional calculations. F is investigated as a function of the layer thickness d , the vacuum gap width L between slabs, and the external magnetic field strength H . Features of F as function of the external field include the presence of sharp dips and peaks, which appear in the vicinity of the resonance frequency, and are consequences of the interaction of the external magnetic field with the electron spin. In addition, an external field may diminish F , which is an important effect not found in any other system.

Vapor-phase epitaxial ZnS : N,Ag/GaAs layers co-doped with Cl or In were investigated by Hall-effect and photoluminesnce measurements. Hall-effect measurements at room temperature revealed free hole concentrations and mobility values to be (1–7)×1017 cm−3 and 60–70 cm2/V s for ZnS : N, Ag, Cl layers, and to be (0.6–1.4)×1019 cm−3 and 10–25 cm2/V s for ZnS : N, Ag, In layers, respectively. Almost temperature independent free hole concentrations of these layers indicate the formation of impurity band. Concentrations of electrically active acceptor, donor, and neutral impurities were estimated from the temperature dependences of mobility values and hole concentrations. On the basis of the theory of ion pairing, the nearest-neighbor nitrogen-donor (In or Cl) pairs are suggested as the origin of neutral impurity centers contributing to the mobility. Appearance of the “blue-Ag emission” and low-resistive p-type conduction were compatible only for ZnS : N.Ag,In layers.

Origins of lines appearing in the exciton region spectra of CuGaS2 crystals at low temperatures under 4579, 4765 or 4880 A excitation of an Ar+ laser are discussed in terms of emissions from upper- and lower-branch excitonic polaritons (UBPs and LBPs) and multi-phonon Raman processes. The line at 2.500 eV is an emission from LBPs. The line at 2.504 eV seen in our samples under 4765 A excitation is shown to be interpretable as a three-phonon Raman process in resonance with UBP states, while the line reported at the same energy by Shirakata is likely to be an emission from UBPs.

In order to clarify the donor and acceptor levels in p- and n-type ZnS layers grown on GaAs substrates by vapor phase epitaxy, delayed photoluminescence excitation spectra were measured at some lapse of time after excitation. This method enabled us to observe a direct resonant excitation of the selective donor-acceptor pair transition having a certain Coulomb energy. Through comparison of the resonant and non-resonant portions of the excitation spectrum, the p-type layer grown under the simultaneous presence of NH 3 and excess Zn atmospheres was found to have a shallow acceptor level of either ≈60 meV or ≈100 meV ionization energy. A description is also given on the structures of the excitation spectra related to bound excitons and on decays of bound excitons.

We calculate transit time of electromagnetic Gaussian packets traversing a periodic structure of alternate layers of dielectric-metamaterial, the packets are tuned at the tunneling modes that appear in the gap and we find superluminal phenomenon.

The conductivity type control of ZnS was demonstrated for the open tube VPE growth on GaAs substrates from a ZnS powder source. The p-type character of the layer grown under the simultaneous addition of a few at% excess Zn and a large amount of NH 3 in the growth system was revealed mainly by the sign of the Seebeck effect and electron-beam induced current profile measurements at the cleaved faces of the epitaxial layers. Various kinds of changes corresponding to the change of the conduction type were observed in the photoluminescence spectra of the edge and bound exciton emissions, and trap levels examined by the transient thermoluminescence method. The role and meaning of the simultaneous addition of Zn and NH 3 are discussed together with the observed change of the amounts of Ga and As impurities from the substrate by EPMA.

Electrical and photoluminescence (PL) properties have been examined for N-doped and P-doped ZnS layers grown by vapor phase epitaxy on GaAs substrates at about 700 °C. Nitrogen doping was done during growth by adding ammonia in the hydrogen flow of an open tube growth system using a ZnS powder source. Phosphorus doping was done by thermal diffusion after growth in a sealed quartz ampoule kept at 500 °C. Incorporation of these impurities was confirmed by physical analyses. The room temperature resistivity values of the N-doped and P-doped layers were 10 6 Ω cm or higher for the former and 10 3 -10 4 Ω cm for the latter, respectively. These values are quite high compared to those of undoped layers, which are less than 0.2 Ω cm with n-type conduction and believed to be due to Ga impurities from the substrates. Compared to undoped samples, notable changes of PL spectra at 77 K include the appearance of a new UV emission at 390 nm and the disappearance of the Cu-related emissions but only for N-doped samples, not for P-doped samples. Concerning the trap levels measured by transient thermoluminescence (TTL) method, no difference was found between doped and undoped samples, except their concentrations. Discussions on these results are given in terms of substitutional nitrogen forming compensating acceptors and associated centers with Cu impurities.

Low-resistivity p-type ZnS layers have been grown on GaAs substrates by vapor-phase epitaxy from a Zn-added ZnS powder source, using an open tube system under a NH3-added hydrogen flow. The simultaneous addition of NH3 and Zn has been shown to be essential for the appearance of p-type conduction. The room temperature Hall-effect measurement of a grown layer revealed the hole concentration to be 6×1018 cm-3 and the mobility to be 40 cm2/(V·s). The p-ZnS/n-GaAs heterojunction showed good rectifying behavior and exhibited an infrared emission, having a peak photon energy corresponding to the band gap energy of GaAs under forward bias.