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[en] Zinc K-edge X-ray absorption near-edge (XANES) spectroscopy was conducted on 40 zinc mineral samples and organic compounds. The K-edge position varied from 9660.5 to 9666.0 eV and a variety of distinctive peaks at higher post-edge energies were exhibited by the materials. Zinc is in the +2 oxidation state in all analyzed materials, thus the variations in edge position and post-edge features reflect changes in zinc coordination. For some minerals, multiple specimens from different localities as well as pure forms from chemical supply companies were examined. These specimens had nearly identical K-edge and post-edge peak positions with only minor variation in the intensity of the post-edge peaks. This suggests that typical compositional variations in natural materials do not strongly affect spectral characteristics. Organic zinc compounds also exhibited a range of edge positions and post-edge features; however, organic compounds with similar zinc coordination structures had nearly identical spectra. Zinc XANES spectral patterns will allow identification of unknown zinc-containing minerals and organic phases in future studies.
[en] Metastability of states associated with point defects in semiconductors in an interesting fundamental property turning out to be more common than erstwhile. This article highlights two important examples of metastable defects, one in the elemental semiconductor silicon and the other in the compound semiconductor Zn Se, of significant current interest for blue-emitting devices. (author)
[en] The electronic structure of zinc chalcogenide crystals doped with nontransition V elements was studied in the cluster approximation on the basis of a physically adequate method accounting for boundary conditions. It is shown that the formation of A-centers is a specific manifestation of a general tendency toward the reconstruction (relaxation) of impurity centers, which is mainly caused by the change in crystal electronic structure upon doping. Specific features of the formation of reconstructed centers with different charge states are studied for a series of impurities and crystalline matrices. 19 refs., 3 tabs
[en] It is suggested that the existing classification of polytype structures of zinc sulfide be supplemented with an additional criterion: the characteristic of regular point systems (Wyckoff positions) including their type, number, and multiplicity. The consideration of the Wyckoff positions allowed the establishment of construction principles of known polytype series of different symmetries and the systematization (for the first time) of the polytypes with the same number of differently packed layers. the classification suggested for polytype structures of zinc sulfide is compact and provides a basis for creating search systems. The classification table obtained can also be used for numerous silicon carbide polytypes. 8 refs., 4 tabs
[en] ZnS polytypes are formed by martensitic transformations from their common parent, the hexagonal 2H structure, and their crystallographic characteristics depend on the detailed transformation mechanism. The ratio of the number of rhombohedral to the number of non-rhombohedral polytypes in the population of the currently identified polytypes is 1.5. It was formerly argued that the expected ratio is 2 and that the discrepancy indicates that the population is biased. An analysis based on the established properties of martensitic transformations in ZnS shows that the ratio of rhombohedral to non-rhombohedral polytypes depends on the transformation probability by a dislocation dipole; it is further shown that the experimental ratio of 1.5 can be derived by assuming the plausible value of 0.8±0.1 for this probability. (orig.)
[en] We investigated the properties of artificial pinning centers of YBCO multilayer films in which Y2O3 and ZnO nanoparticles are uniformly introduced by using the pulsed laser deposition (PLD) technique. Y2O3 and ZnO nanoparticles were deposited on top of YBCO buffer layer and the density of nanoparticles was controlled by varying the number of nanoparticle layers. YBCO superconducting layers with total thickness of 250 nm were deposited on top of Y2O3 and ZnO nanoparticles. Based on analyses of the surface morphology, the transition temperature Tc, and the critical current density Jc, we discussed the difference between the two kinds of nanoparticles as flux pinning centers.
[en] A triple-color photodetector with MSM structure based on the ZnO/MgZnO films was fabricated. There are three response peaks in the response spectrum for the triple-color photodetector, which response peaks are located at around 290, 320 and 360 nm, respectively. A further study on responsivity for the triple-photodetector is carried out. The rising velocity of cubic MgZnO (111) response peak is faster than hexagonal MgZnO (002) response peak, the different internal gain between the different crystal orientation is the main reason for the different of the response peaks between the two phases. This experiment would have a great significance for multiple-colors photodetectors field.
[en] This paper reports the resistive switching and synaptic capability of AZO/ZnO/ITO transparent and flexiblevalence change memory device structure. The device performs stable endurance for more than 50 cycles with sufficient ON/OFF ratio of one order of magnitude; no intermediate state (data error) is observed during the cycle-to-cycle test. By exploiting the analog switching characteristic of the device and employing identical pulses to the top electrode, a synaptic behavior can be achieved. A low programming voltage of 1.5V is used to modulate the conductance during potentiation and depression which indicate that the device is a logic-compatible. The conduction mechanism during the switching processand the device performance is discussed. (paper)