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91.
In this work, we demonstrate the thin AlAs layer insertion into GaAs/AlGaAs quantum well (QW) structures and its influence in energy transition in the frequency range of mid-infrared. To realize the more accurate calculation, the graded interface model of QW structures is integrated into our self-consistent solving of Schrodinger and Poisson equations to obtain the energy level and envelope wave functions of QW. We find the thin AlAs layer inserted at various positions in the well can obviously tune intersubband optical transitions. The corresponding tuning range can be 50 meV. We find that the thicker AlAs layer (2 monolayers) can provide wider tuning range and larger oscillator strength between subbands 1 and 3, compared with the thinner one (1 monolayer). Our results suggest that thin semiconductor layer may be an idea optimization design for the quantum well terahertz lasers which are based on optical pumping with mid-infrared lasers. 相似文献
92.
93.
V.G. Bazhenov S.V. Zefirov L.N. Kramarev Ye.V. Pavlenkova 《Journal of Applied Mathematics and Mechanics》2008,72(2):226-232
Generalized two-dimensional problems of the torsion of elastoplastic solids of revolution of arbitrary shape for large deformations under non-uniform stress-strain conditions are formulated and a method for their numerical solution is proposed. The use of this method to construct strain diagrams of materials based on experiments on the torsion of axisysmmetric samples of variable thickness until fracture occurs is described. Experimental and numerical investigations of processes of elastoplastic deformation, loss of stability and supercritical behaviour of solid cylindrical steel samples of variable thickness under conditions of monotonic kinematic loading with a torque, a tension and a combined load are presented. The mutual influence of torsion and tension on the deformation process and the limit states is estimated, and the universality (the independence of the form of the stress-strain state) of the “stress intensity – Odqvist parameter” diagram for steel for large deformations is proved. 相似文献
94.
95.
In single-slip-oriented copper single crystals, which were cyclically deformed under constant plastic shear strain amplitude control, a persistent slip band (PSB) was initiated on the persistent slip line (PSL) that first formed in the matrix vein dislocation structure. During intermediate temperature recovery (ITR) treatment in vacuum at 245 to 400°C, the variations in dislocation configurations and other defects of fatigued specimens were studied by using the scanning electron microscopy (SEM) electron channelling contrast (ECC) and the positron annihilation life (PAL) techniques. The results show that the ladders in the PSBs became curved and broken, or escaped locally until the PSBs disappeared completely during ITR treatment. The annihilation of the PSBs and other dislocation structures in the fatigued specimens prolonged the fatigue life to a certain extent. 相似文献
96.
97.
Ling-yan Li Hui Gu Yong-jun Tian Toshiyuki Nishimura Joachim Bill 《Journal of Non》2009,355(48-49):2390-2395
Inner pore channels were commonly found in precursor-derived Si–C–N ceramics. After annealing in air at 1420 °C, their oxidation structures were investigated by analytical TEM. A carbon-rich ring was frequently observed under the silica layer inside the pore channels, which consisted of graphite-like clusters in size of 20–30 nm. Origin of such interfacial structure is due to the excessive free-carbon in the amorphous Si–C–N matrix that had survived the oxidation process. This graphitic interface could further improve the oxidation resistance of the SiO2 over-layer. This novel interfacial structure was also found by annealing in N2, reaffirming the effect of composition of Si–C–N matrix. 相似文献
98.
V. I. Voronin V. V. Shchennikov I. F. Berger V. P. Glazkov D. P. Kozlenko B. N. Savenko S. V. Tikhomirov 《Physics of the Solid State》2001,43(11):2165-2170
The structure of HgSe1?x Sx ternary mercury chalcogenides at high pressures up to 35 kbar is investigated by neutron diffraction. It is found under pressure, that the HgSe1?x Sx compounds undergo, a phase transition from the cubic sphalerite-type to the hexagonal cinnabar-type structure, which is accompanied by a jump-wise change in the unit cell volume and interatomic distances. The unit cell parameters and the positional parameters of Hg and Se (S) atoms in the high-pressure hexagonal phase are determined. A two-phase state is revealed in the phase transition region. 相似文献
99.
A.A. Kordyuk V.B. Zabolotnyy D.V. Evtushinsky D.S. Inosov T.K. Kim B. Büchner S.V. Borisenko 《The European physical journal. Special topics》2010,188(1):153-162
We review the search for a mediator of high-T
c superconductivity focusing on ARPES experiment. In case of HTSC cuprates, we summarize and discuss a consistent view of electronic
interactions that provides natural explanation of both the origin of the pseudogap state and the mechanism for high temperature
superconductivity. Within this scenario, the spin-fluctuations play a decisive role in formation of the fermionic excitation
spectrum in the normal state and are sufficient to explain the high transition temperatures to the superconducting state while
the pseudogap phenomenon is a consequence of a Peierls-type intrinsic instability of electronic system to formation of an
incommensurate density wave. On the other hand, a similar analysis being applied to the iron pnictides reveals especially
strong electron-phonon coupling that suggests important role of phonons for high-T
c superconductivity in pnictides. 相似文献
100.