Kei Inumaru  Kazuya Baba  Shoji Yamanaka 《Applied Surface Science》2006,253(5):2863-2869

Molybdenum nitride Mo₂N_x films were grown on MgO(0 0 1) and on α-Al₂O₃(0 0 1) substrates by molecular beam epitaxy under nitrogen radical irradiation. X-ray photoelectron spectroscopy revealed that the composition of the film varied in the range of Mo₂N_1.4-Mo₂N_2.8 depending on the growth temperature. The deposition at 973 K gave well-crystallized films on both substrates. The high-resolution reciprocal space mapping by X-ray diffraction showed that the nitrogen-rich γ-Mo₂N crystalline phase (the composition: Mo₂N_1.4) was epitaxially grown on MgO at 923 K with a slight tetragonal distortion (a = 0.421 and c = 0.418 nm) to fit the MgO lattice (a = 0.421 nm). On α-Al₂O₃(0 0 1), nitrogen-rich γ-Mo₂N (Mo₂N_1.8) was grown at 973 K with (1 1 1) planes parallel to the substrate surface. X-ray diffraction analysis with a multi-axes diffractometer revealed that the γ-Mo₂N on α-Al₂O₃(0 0 1) had a slight rhombohedral distortion (a = 0.4173(2) and α = 90.46(3)°). Superconductivity was observed below 2.8-3 K for the films grown at 973 K on MgO and on α-Al₂O₃(0 0 1).  相似文献   

    

Anna Gorczyca  Mariusz Krawiec  Maciej M. Maka  Marcin Mierzejewski 《physica status solidi b》2007,244(7):2448-2452

There is still no consensus on the mechanism that is responsible for a particle–hole asymmetry observed in scanning tunneling spectroscopy of high‐temperature superconductors. According to the most popular hypothesis this asymmetry results from strong Coulomb correlations in a nearly half‐filled band. In the present paper we propose another mechanism that leads to such asymmetry. It originates from the coupling between the superconductor and the substrate that the system is deposed on. We show that this coupling gives rise to the particle–hole asymmetry only in the case of an anisotropic superconductivity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

L. Doyennette  A. Vardi  F. Guillot  L. Nevou  M. Tchernycheva  A. Lupu  R. Colombelli  G. Bahir  E. Monroy  F. H. Julien 《physica status solidi b》2006,243(15):3993-3997

GaN/AlN quantum dot photodetectors based on intraband absorption and in‐plane carrier transport have been fabricated and characterized. These photodetectors operate at room temperature at telecommunication wavelengths (1.3–1.55 μm). Their TM‐polarized intraband absorption is ascribed to the transition from the ground state s to the excited state p_z of the GaN dots. The responsivity peaked at 1.41 μm is as high as 8 mA/W at room temperature for the interdigitated contact photodetector. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

T. Vnsk  M. Lindberg  J. Olsen  D. Sundholm 《physica status solidi b》2006,243(15):4035-4045

Powerful computational methods are presented for studies of energy levels, photon‐recombination rates, and phonon‐relaxation rates of neutral and charged multiexciton complexes at correlated levels of theory. The electron–hole system is described by a two‐band effective‐mass Hamiltonian. The one‐particle functions are expanded in a basis set consisting of anisotropic Gaussian functions. The many‐body Hamiltonian constructed in the space of the antisymmetric products of one‐particle functions is diagonalized using general coupled‐cluster and configuration‐interaction methods. The expansion coefficients of the coupled‐cluster and configuration‐interaction wave functions are obtained by solving the corresponding equations using direct iterative algorithms. We demonstrate the potential of the computational approaches by calculating total energies of multiexciton complexes at coupled‐cluster and configuration‐interaction levels. Computational methods for studies of radiative recombination and phonon‐relaxation rates have also been developed and results are reported for radiative recombination rates and recombination energies of the exciton, biexciton, and of the positive and the negative trions confined in a InGaAs/GaAs quantum‐dot sample. Phonon‐relaxation rates have been calculated for a few low‐lying Δ _g states of the exciton complex of the same quantum‐dot sample. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

T. Meunier  K.‐J. Tielrooij  I. T. Vink  F. H. L. Koppens  H. P. Tranitz  W. Wegscheider  L. P. Kouwenhoven  L. M. K. Vandersypen 《physica status solidi b》2006,243(15):3855-3858

We demonstrate experimentally a read‐out method that distinguishes between two‐electron spin states in a quantum dot. This scheme combines the advantages of the two existing mechanisms for spin‐to‐charge conversion with single‐shot charge detection: a large difference in energy between the two states and a large difference in tunnel rate between the states and a reservoir. As a result, a spin measurement fidelity of 97% was achieved, which is much higher than previously reported fidelities. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Seung‐Seok Ha  Chun‐Yeol You 《physica status solidi (a)》2007,204(12):3962-3965

This study perform numerical analysis for a Joule heated nano‐pillar system, which has a tunneling barrier, using the hot electrons' dissipation concept. The main focus was on the temperature dependence of the radius, thickness of the nano‐pillar and input power using the finite element method. The published experimental conditions were considered for the calculations. It was found that the peak temperature T (t =t_p ) depends on the dimensions of the nano‐pillar and input power. Surprisingly, the increase in temperature was in the order of only 1 Kelvin. The reason for such a small increase in temperature is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Ji Hyun Min  Jun Hua Wu  Ji Ung Cho  Ju Hun Lee  Young‐Dong Ko  Hong‐Ling Liu  Jin‐Seok Chung  Young Keun Kim 《physica status solidi (a)》2007,204(12):4158-4161

Fabrication of Co‐Pt nanowire arrays with fcc‐Co₃Pt phase was accomplished by DC electrodeposition in anodic aluminum oxide (AAO) nanotemplates. The microstructural and magnetic properties of the nanowires were investigated as a function of the deposition current density (Co concentration). The nanowires possess fcc‐Co₃Pt phases and are ferromagnetic. Their crystallinity and magnetic performance was enhanced after annealing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Z. Beji  T. Ben Chaabane  L. S. Smiri  S. Ammar  F. Fivet  N. Jouini  J. M. Grenche 《physica status solidi (a)》2006,203(3):504-512

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Cludio Geraldo Schn  Bruno Geoffroy Scuracchio 《physica status solidi (a)》2006,203(10):2365-2369

The “as‐cast” microstructure of Fe–30Al–6Cr and Fe–30Al–10Ti high purity alloys was investigated using Electron Backscatter Diffraction. The first alloy is characterized by a highly textured columnar grain microstructure with large grains, while the second is characterized by an equiaxed grain microstructure with small grains and a random texture. These differences are discussed with regard to the higher reactivity of Ti compared with Cr, leading to nanometric nitride or oxide, which may act as sites for heterogeneous nucleation, and the ordered state of the BCC phase in equilibrium with the liquid during solidification and its effect upon dendrite growth kinetics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

A. Goker 《physica status solidi b》2010,247(1):129-133

We investigate electron transport through a diatomic molecule parallelly coupled to ferromagnetic source and drain contacts. We utilize a model Hamiltonian involving a Hubbard term in which the contacts are modeled using recently developed complex source and sink potentials. The zero bias transmission spectrum for a symmetrically coupled system as a function of the Fermi energy acquires a Fano lineshape as the Hubbard interaction is turned on. For large values of U, the Fano lineshape broadens and shifts to higher energy values disappearing eventually. Meanwhile, the Breit–Wigner resonance located at the bonding resonance in the noninteracting limit survives but its position is shifted twice the coupling between the atoms in the molecule in the infinite U limit and its linewidth is reduced to half. We attribute this behavior to the unavailability of one of the transmission channels.  相似文献