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[en] The effect of magnetic dilution, through the production of samples of Mn_xZn_1-xPS₃, has been explored experimentally using a SQUID magnetometer and magnetic neutron scattering. The concentration and temperature dependence of the Neel temperature, T_N, can be explained by that of the dipolar anisotropy, and these results allow an estimate of the single ion anisotropy. This anisotropy, which is due to the electric field symmetry at the moment site, is found to be significant, and may explain critical neutron scattering results found in the literature. These results show that the critical scattering is of a planar, or XY, universality class rather than an Ising class, although the latter is what would be expected from the zero field, low temperature magnetic order. Also, the change in orientation of the magnetic moments with dilution agrees with a model of competing dipolar and single-ion anisotropies. We conclude that dipole-dipole interactions provide the dominant anisotropy mechanism in Mn_xZn_1-xPS₃. In conjunction with exchange and single-site effects, this anisotropy explains much of the observed behaviour

[en] Methodic of spectral measuring of electroluminescence (EL) on unit with plasma electrodes is presented. Possibilities of spectral separation of alkaline halogen crystals (AHC) layers luminescence are studied. It was shown, that on the unit it is possibly reliable spectrum separation of radiation of gas discharge and EL of non-activated and activated AHC samples. Measuring results of EL for KCl, NaCl, KBr spectra are cited

[en] It is well known that when light is incident on an undoped semiconductor, photo-created conduction electrons and valence holes form strongly bound pairs (excitons (X)) which dominate optical spectra. In 2D semiconductor systems the presence of a very small density of excess carriers causes the formation of negatively charged excitons (X^-)¹, which are an analogue of the negatively charged hydrogen atom (H^-). In contrast to bound states in 3D, which are completely screened by a large density of carriers, it is expected that in 2D the potential of a valence hole always contains a doubly occupied bound state (i.e. X^- always exists), even in the presence of high densities of carriers. When a valence band hole is introduced (optically) into a doped n-type semiconductor system, the free conduction band electrons react by attempting to screen the hole and the result is a singularity in absorption and photoluminescence (PL) spectra at transition energies that correspond to electron states close to the Fermi level. We have studied these problems experimentally using absolute absorption spectra from a series of modulation-doped GaAs/AlGaAs multiple quantum well samples with different carrier densities. We observe the evolution (as a function of carrier density) from the low density excitonic ground state to the FES at high carrier density and find that the results are in good agreement with theoretical calculations which include many-body effects and the doubly occupied bound state (X^-) in a realistic way. In particular, the evolution of the absorption lineshape in the experiment is found to be consistent with the predicted variation of the strength of the singularity (given by the calculated binding energy of the doubly occupied bound state)

[en] The time evolution of the amplitude of periodic nanoscale ripple patterns formed on Ar+ sputtered Si(OOl ) surfaces was examined using a recently developed in situ spectroscopic technique. At sufficiently long times, we find that the amplitude does not continue to grow exponentially as predicted by the standard Bradley-Harper sputter rippling model. In accounting for this discrepancy, we rule out effects related to the concentration of mobile species, high surface curvature, surface energy anisotropy, and ion-surface interactions. We observe that for all wavelengths the amplitude ceases to grow when the width of the topmost terrace of the ripples is reduced to approximately 25 nm. This observation suggests that a short circuit relaxation mechanism limits amplitude . growth. A strategy for influencing the ultimate ripple amplitude is discussed

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[en] The charge transport and photoconductivity of the chalcogenide vitreous semiconductors (ChVS) amorphous films with composition As₂ Se₃, As Se, As₃ Se₂ prepared by r.f. sputtering were studied. It was found that the samples with stoichiometric film composition have bipolar carriers transport and bipolar photo conductivities while the films containing excess of arsenic element have only mono polar electron transport. The results were interpreted by the used models of the charge structure effects of ChVS which depend on the Se an AS defects. (author)