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1

Electronic Resource

Effect of various obstacles on oscillatory magnetoconductance of quantum double-coupled channels (1994)

Fan, Xu-dong ; Gu, Ben-yuan ; Yang, Guo-zhen ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 75 (1994), S. 2466-2472

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The characteristics of the magnetoconductance of a nonuniform electron waveguide containing various shaped obstacles are investigated by using a model of two-coupled tight-binding chains and the transfer-matrix approach. The variation of the magnetoconductance as a function of total magnetic flux Φ threading the obstacle region is presented. The effect of the interchain tunneling modulation on the magnetoconductance for double-mode and single-mode transport processes is different. When the energy of the incident electrons is just above the threshold energy for the opening of the second propagating mode at zero magnetic field, at some magnetic flux, the conductance abruptly decreases owing to the presence of mode quenching. The magnetoconductance for various multiply connected structures and one-dimensional superlattice (1DSL) type tunneling modulation structures is also evaluated. Owing to the presence of the miniband gaps to be formed by 1DSL structures, different patterns in the magnetoconductance are found.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.356996

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2

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Optical and transport properties of Sb-doped SrTiO3 thin films (2001)

Wang, Huan-hua ; Cui, Da-fu ; Dai, Sou-yu ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 90 (2001), S. 4664-4667

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Optically transparent SrTi1−xSbxO3 (=0.05, 0.10, 0.15, and 0.20) thin films with transmittances higher than 85% in the visible region have been grown on SrTiO3 substrates by pulsed-laser deposition. Unless overdoped, the films possess a single-crystal phase and impurity conduction. The temperature dependence of the resistivities shows a metal–semiconductor transition for the film with x=0.05, and semiconducting behaviors for the films with x=0.10 and 0.15. The overdoped film with x=0.20 is an insulator. Sb concentration has a dominant effect on the electrical properties of the films, and the Anderson localization is probably the mechanism. X-ray photoelectron spectroscopy results indicate that the Sb impurity atoms provide donor electrons to form impurity states within the band gap, which is responsible for the electrical localized impurity. The wide band gap and the low density of states in the conduction band result in the transparency of the films. The disorder increases with Sb concentration, which is the main origin of the evolution of the electrical properties. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1408596

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3

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Theoretical analysis of thin film epitaxial growth monitored by differential reflectance (2000)

Yang, Guo-Zhen

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 87 (2000), S. 739-744

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The thin film growth at the level of a single molecular layer can be achieved via laser molecular beam epitaxy approach. Such a growth can be monitored not only via the reflection high-energy electron diffraction technique, but also with the use of relative reflectivity change between s- and p-polarized light. The epitaxy growth of thin film is modeled as a microscopic two-dimensional (2D) gratings on the surface of the substrate with a period over two orders of magnitude less than the wavelength of probe light. The solution of Maxwell's equations for such a 2D gratings leads to an effective multilayer medium model, from which the reflectance-difference (RD) signal in the process of epitaxy growth can be calculated in the framework of general optics. The simulation results demonstrate that the growth of thin film at the atomic level can be detected by such an optical RD technique. The theoretical calculations of RD signal are in agreement with the experimental measurements both in the order of magnitude and variation character of RD signal curve. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.371934

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4

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Effects of defect scattering on guided electron waves in two coupled quantum wires (1992)

Wang, Jian-Qing ; Gu, Ben-Yuan ; Yang, Guo-Zhen

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 72 (1992), S. 2299-2311

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: We have investigated how the presence of a defect in two coupled quasi-one-dimensional quantum wires influences the propagation properties of guided electron waves in the system. The defect potential in the two dimensional electron gas is modeled by a two dimensional δ function. In elastic scattering, the transfer of the electron among various eigenstates of the uncoupled quantum wires and from one wire to the other is largely affected by the defect potential. For the single mode shallow potential well system, the defect causes incomplete energy transfer between the channels. As the position of the defect varies along the channel, the characteristics of the mode amplitude functions change dramatically as the defect passes through nodes of the amplitude function of the incident waves in the channel. When the defect position is away from these nodes the amplitude functions of the transmitted waves reduce greatly due to the large reflection by the defect. And their variation never reaches zero as in the case without defect. When the defect position is near these nodes the tunneling characteristics between the two channels are as if the defect is absent since the reflection is minimal. For the strong scatterer we find a pinning effect in that the mode amplitude function of the channel where the defect is located always has one of its transmission minima pinned down to the defect. We introduce a possible way of injecting the propagating electron into a particular channel and at a given longitudinal position, by controlling the position of the defect in the structure. In the multimode deep potential well structure, the transfer from an eigenstate of the uncoupled quantum wires to the other states is greatly enhanced and the characteristics of the amplitude functions are dramatically changed by intersubband scatterings.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.351572

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5

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Electrical and optical properties of strongly reduced epitaxial BaTiO3−x thin films (2000)

Zhao, Tong ; Chen, Zheng-Hao ; Chen, Fan ; [et al.]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 77 (2000), S. 4338-4340

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ISSN: 1077-3118

Source: AIP Digital Archive

Topics: Physics

Notes: A series of BaTiO3−x (x=0, 0.07, 0.18, and 0.48) thin films with c-axis oriented tetragonal perovskite structures were epitaxially grown on SrTiO3 (100) and MgO (100) substrates by laser molecular-beam epitaxy under various oxygen pressures. The electrical conductivity of the deposited thin films increases with decreasing the oxygen pressure. A metallic conduction is observed in the oxygen most deficient BaTiO2.52 thin film whose oxygen content (2.52) and electrical resistivity (6.0×10−5 Ω cm) are both the minimum values among literature. An optical absorption peak is observed in each oxygen deficient BaTiO3−x thin film. The peak position shifts to lower energy, and the peak width becomes larger with decreasing the oxygen pressure. The influence of oxygen pressure on the electrical and optical properties in the reduced BaTiO3−x thin films is discussed. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1334353

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6

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Bolometric observation of nonradiative decay of surface plasmons in silver (1989)

Xie, Yuan -Lin ; Li, Hua ; Zhou, Yue -Liang ; [et al.]

Springer

Applied physics 48 (1989), S. 497-500

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ISSN: 1432-0630

Keywords: 07.60 ; 07.62 ; 78.65

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract A bolometric technique was used to observe the nonradiative decay of surface plasmons in a silver film. This technique allowed us to separate the radiative and nonradiative relaxations of the plasmons and to determine the radiative quantum efficiency. It is suitable for both cw and pulsed laser beams and for both polarized and nonpolarized light.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00619725

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7

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Improvement of absolute band gaps in 2D photonic crystals by anisotropy in dielectricity (1999)

Li, Zhi-Yuan ; Gu, Ben-Yuan ; Yang, Guo-Zhen

Springer

The European physical journal 11 (1999), S. 65-73

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ISSN: 1434-6036

Keywords: PACS. 78.20.Ci Optical constants (refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) - 78.20.Fm Birefringence - 42.50.-p Quantum optics - 81.10.Aj Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract: Two-dimensional (2D) photonic band gaps (PBG) structure fabricated from anisotropic dielectric is studied by solving Maxwell's equations with use of plane-wave expansion method. Numerical simulations show that absolute photonic band gaps can be substantially improved in two dimensional square and triangular lattices of cylinders by introducing anisotropy in material dielectricity. Owing to different refractive indices for electromagnetic waves with E- and H-polarization, the quasi-independent adjustment of band gaps for the E- and H-polarization modes can be implemented by uniaxial crystals with their extraordinary axis parallel to the cylinders. Large absolute band gaps can be created for uniaxial cylinders in air with a positive anisotropy. In the case of air holes in background uniaxial dielectric with even a weak negative anisotropy, the absolute band gap can be increased 2-3 times. Large absolute band gap can also be obtained in other complex configurations of uniaxial and biaxial materials and this enables a full exploitation of potential utilization for anisotropic materials available in nature. Such a mechanism of band gap adjustment should open up a new scope for designing band gaps in 2D PBG structures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1088/0953-8984/11/10/001

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