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1.
By employing the perturbation formulae of the spin Hamiltonian parameters (SHPs) (g factors gxx, gyy, gzz, hyperfine structure constants Axx, Ayy, Azz and superhyperfine parameters Axx׳, Ayy׳, Azz׳) for a 3d1 ion in orthorhombically elongated octahedra and tetrahedra, the defect structures and the experimental EPR spectra are theoretically and systematically investigated for the two orthorhombic Ti3+ centers C1 and C2 in ZnWO4. Center C1 is ascribed to the impurity Ti3+ at host W6+ site associated with two nearest neighbor oxygen vacancies due to charge compensation. The resultant tetrahedral [TiO4]5– cluster is determined to undergo the local orthorhombic elongation distortion, characterized by the axial distortion angle Δθ (=θ–θ0≈–6.84°) of the local impurity-ligand bond angle θ related to θ0 (≈54.74°) and the perpendicular distortion angle Δε (=ε–ε0≈2.5°) related to ε0 (≈45°) of an ideal tetrahedron because of the Jahn–Teller effect. Center C2 is attributed to Ti3+ on Zn2+ site, and this octahedral [TiO6]9– cluster may experience the local axial elongation ΔZ (≈0.001 Ǻ) and the planar bond angle variation Δφ (≈9.1°) due to the Jahn–Teller effect, resulting in a more regular oxygen octahedron. All the calculated SHPs (i.e., g factors for both centers, the hyperfine structure constants for center C2 and superhyperfine parameters of next nearest neighbor ligand W for center C1) show good agreement with the observed values. However, the theoretical results based on the previous assignment of center C1 as Ti3+ on W6+ site with only one nearest planar oxygen vacancy (i.e., five-fold coordinated octahedral [TiO5]7– cluster) show much worse agreement with the experimental data. The defect structures and the SHPs (especially the g anisotropies) are discussed for both centers. The present studies on the superhyperfine parameters of ligand W6+ for center C1 would be helpful to further investigations on the superhyperfine interactions of cation ligands which were rather scarcely treated before. 相似文献
2.
Facile non‐lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene‐block‐polydimethylsiloxane films
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Zhe Qiang Maurice L. Wadley Bryan D. Vogt Kevin A. Cavicchi 《Journal of Polymer Science.Polymer Physics》2015,53(15):1058-1064
Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064 相似文献
3.
4.
The quantum states are presented in these processions of fabricating poly-Si films. Amorphous silicon films prepared by PECVD has been crystallized by conventional furnace annealing (FA) and rapid thermal annealing (RTA), respectively. It is found that the thin films grain size present quantum states with the increasing of the gas flow ratios of SiH4, H2 mixture, substrate temperatures, frequency power, annealing temperature and time. 相似文献
5.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
6.
利用室温下压电调制反射光(PzR)谱技术系统测量了N掺杂浓度为0.0%—3%的分子束外延生长GaNxAs1-x薄膜,并对图谱中所观察的光学跃迁进行了指认.在GaN0.005As0.995和GaN0.01As0.99薄膜的PzR谱中观察到此前只在椭圆偏振谱中才看到的N掺杂相关能态E1+Δ1+ΔN.当N掺杂浓度达到
关键词:
压电调制反射光谱(PzR)
xAs1-x薄膜')" href="#">GaNxAs1-x薄膜
分子束外延(MBE) 相似文献
7.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Diffraction in electron stimulated desorption has revealed a propensity for Cl+ desorption from rest atom vs. adatom areas and unfaulted vs. faulted zones of Cl-terminated Si(1 1 1)-(7 × 7) surfaces. We associate the 15 eV ± 1 eV threshold with ionization of Si-Cl σ-bonding surface states and formation of screened two-hole states with Si 3s character. Similar specificity is observed from A and B reconstructions. This can be due to reduced screening in unfaulted regions and increased hole localization in Si back-bonds within faulted regions. 相似文献
9.
Electron spin resonance spectra of Mn2+ in diluted solid solutions of MnO2 in Y2O3 have been studied at room temperature for Mn concentrations between 0.20 and 2.00 mol%. Isolated Mn2+ ions in sites with two different symmetries were observed, as well as Mn2+ ions coupled by the exchange interaction. The relative concentration of isolated to coupled Mn2+ ions decreases with increasing manganese concentration. The results are consistent with the assumption that the manganese ions occupy preferentially the C2 symmetry sites. A theoretical calculation based on this model yields an effective range of the exchange interaction between Mn2+ ions of 0.53 nm, of the same order as that of Mn2+ ions in CaO. 相似文献
10.
Fabio Schoen 《Journal of Global Optimization》1991,1(3):207-228
In this paper stochastic algorithms for global optimization are reviewed. After a brief introduction on random-search techniques, a more detailed analysis is carried out on the application of simulated annealing to continuous global optimization. The aim of such an analysis is mainly that of presenting recent papers on the subject, which have received only scarce attention in the most recent published surveys. Finally a very brief presentation of clustering techniques is given. 相似文献