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Williams GA 《Physical review letters》2004,92(19):197003
Vortex-loop renormalization techniques are used to calculate the magnitude of the critical Casimir forces in superfluid films. The force is found to become appreciable when the size of the thermal vortex loops is comparable to the film thickness, and the results for TT(c). When applied to a high-T(c) superconducting film connected to a bulk sample, the Casimir force causes a voltage difference to appear between the film and the bulk, and estimates show that this may be readily measurable. 相似文献
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The surface impurity effect on the surface-state conductivity and weak antilocalization(WAL) effect has been investigated in epitaxial Bi(111) films by magnetotransport measurements at low temperatures. The surface-state conductivity is significantly reduced by the surface impurities of Cu, Fe, and Co. The magnetotransport data demonstrate that the observed WAL is robust against deposition of nonmagnetic impurities, but it is quenched by the deposition of magnetic impurities which break the time reversal symmetry. Our results help to shed light on the effect of surface impurities on the electron and spin transport properties of a 2D surface electron systems. 相似文献
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Persistent superconductivity in ultrathin Pb films: a scanning tunneling spectroscopy study 总被引:1,自引:0,他引:1
By using a low temperature scanning tunneling microscope we have probed the superconducting energy gap of epitaxially grown Pb films as a function of the layer thickness in an ultrathin regime (5-18 ML). The layer-dependent energy gap and transition temperature (Tc) show persistent quantum oscillations down to the lowest thickness without any sign of suppression. Moreover, by comparison with the quantum-well states measured above Tc and the theoretical calculations, we found that the Tc oscillation correlates directly with the density of states oscillation at E(F) . The oscillation is manifested by the phase matching of the Fermi wavelength and the layer thickness, resulting in a bilayer periodicity modulated by a longer wavelength quantum beat. 相似文献
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Yamada TK Bischoff MM Heijnen GM Mizoguchi T Van Kempen H 《Physical review letters》2003,90(5):056803
We report the observation of a magnetic contrast of up to 20% in the scanning tunneling spectroscopy dI/dV maps obtained with Fe-coated tips on Mn(001) layers grown on an Fe(001) whisker at 370 K. These nanometer resolution microscopy results show that the layers couple antiferromagnetically. By normalizing the dI/dV curves by tunneling probability functions, we found a spin-dependent peak on the body-centered-tetragonal (bct) Mn(001) surface at +0.8 V, whose high spin polarization gives rise to the dI/dV map contrast. Band structure calculations allow one to identify the +0.8 V peak as due to two spin-polarized d(z(2)) surface states. 相似文献
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我们在单晶MgO(100)、Si(100)和SiOx/Si基片上成功生长了纳米厚度的超薄NbN薄膜,利用现代分析手段:X射线衍射(XRD)、透射电子显微镜(TEM)、原子力显微镜(AFM)等技术分析研究了所制备的超薄NbN薄膜的微观结构、厚度、表面界面情况等物理特性。研究表明,在MgO(100)基片上获得了外延生长的单晶NbN超薄薄膜,在Si(100)和SiOx/Si基片上获得的是多晶NbN超薄薄膜。厚度均约6nm左右。这些超薄薄膜的超导转变温度分别为:MgO上薄膜是14.46K,Si和SiOx上薄膜分别是8.74K和9.01K. 相似文献
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Jiankui Hao Fei Jiao Datao Xie Kui Zhao 《Physica C: Superconductivity and its Applications》2006,450(1-2):101-104
A new type of superconducting film is studied at Peking University in order to improve the properties of sputter-coated films for superconducting cavities. NbN film and NbN–Nb film have been prepared by DC diode sputtering technology at certain nitrogen content and temperature. NbN film is prepared between copper and Nb film as a barrier against copper diffusion into Nb. Micro-structure analyses show that the NbN–Nb films grow well on the copper substrate. The Tc of the Cu–NbN–Nb increases to 9.5 K compared to the 9.2 K transition temperature of bulk Nb. 相似文献
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High precision measurements of the complex sheet conductivity of superconducting a-Mo77Ge23 thin films have been made from 0.4 K through T(c). A sharp drop in the inverse sheet inductance, L-1(T), is observed at a temperature, T(c), which lies below the mean-field transition temperature T(c0). Just below T(c), the suppression of L-1(T) below its mean-field value indicates that longitudinal phase fluctuations have nearly their full classical amplitude, but they disappear rapidly as T decreases. We argue that there is a quantum crossover at about 0.94T(c0), below which classical phase fluctuations are suppressed. 相似文献
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《Physics letters. A》1988,130(1):43-46
The same mean-field theory for an array of Josephson junctions that describes the onset of superconductivity at normal state resistance RN(c) yields the kinetic inductance, L, for RN<RN(c). The predicted universal behavior of L, as a function of RN/RN(c), provides a further test of the theory of quantum fluctuations. 相似文献
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A square hole array is fabricated over a micro-bridge of NbN thin
film by electron beam lithography and reactive ion milling.
Magneto-resistance is measured across the micro-bridge filled with a
hole array near the superconducting transition temperature. It is
found that magneto-resistance minima occur when the number of
vortices is an integer multiple or a fractional multiple of the
number of holes. The temperature and the current dependences of the
matching effect are studied. 相似文献
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Gomoyunova M. V. Grebenyuk G. S. Pronin I. I. Solov’ev S. M. Marchenko D. E. Vyalikh D. V. 《Physics of the Solid State》2011,53(3):606-611
Physics of the Solid State - The phase composition, electronic structure, and magnetic properties of ultrathin layers of iron and iron silicides formed upon deposition of 1- to 25-Å-thick Fe... 相似文献
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V. K. Dolganov V. M. Zhilin K. P. Meletov 《Journal of Experimental and Theoretical Physics》1999,88(5):1005-1009
Surface molecular ordering in ultrathin molecular films is investigated. The optical transmission spectra of molecular films
ranging in thickness from 2 to 13 smectic layers (6.7–43 nm) in the region of the electronic absorption bands in the smectic
A phase of cyanobiphenyl CB9 are measured. The thickness and temperature dependences of the permittivity are determined. It
is found that the orientational ordering of the molecules depends on the film thickness. The penetration depth of the surface
molecular orientational order does not exceed two smectic layers (<7 nm).
Zh. éksp. Teor. Fiz. 115, 1833–1842 (May 1999) 相似文献
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To alleviate the cavitation damage of metallic engineering components in hydrodynamic systems operating in marine environments, a NbN nanoceramic coating was synthesized on to a Ti-6Al-4V substrate via a double cathode glow discharge technique. The microstructure of the coating consisted of a ~13 μm thick deposition layer of a hexagonal δ′-NbN phase and a diffusion layer ~2 μm in thickness composed of face-centered cubic (fcc) B1-NaCl–structured (Ti,Nb)N. The NbN coating not only exhibited higher values of H/E and H2/E than those measured from NbN coatings deposited by other techniques, but also possessed good adhesion to the substrate. The cavitation erosion resistance of the NbN coating in a 3.5 wt% NaCl solution was investigated using an ultrasonic cavitation-induced apparatus combined with a range of electrochemical test methods. Potentiodynamic polarization measurements demonstrated that the NbN coated specimens demonstrated both a higher corrosion potential (Ecorr) and lower corrosion current density (icorr) than the uncoated substrate. Mott-Schottky analysis, combined with the point defect model (PDM), revealed that, for a given cavitation time, the donor density (ND) of the passive film on the NbN coating was reduced by 1 ~ 2 orders of magnitude relative to the uncoated Ti-6Al-4V, and the diffusivity of the point defects (D0) in the passive film grown on the NbN coating was nearly one order of magnitude lower than that on the uncoated substrate. In order to better understand the experimental observations obtained from Mott-Schottky analysis and double-charge layer capacitance measurements, first-principles density-functional theory was employed to calculate the energy of vacancy formation and the adsorption energy for chloride ions for the passive films present on both the NbN coating and bare Ti-6Al-4V. 相似文献
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K.-I. Akabori K. Tanaka A. Takahara T. Kajiyama T. Nagamura 《The European physical journal. Special topics》2007,141(1):173-180
Mechanical relaxation behavior in ultrathin polystyrene
(PS) films supported on silicon oxide (SiOx) and gold (Au) substrates
has been studied by dynamic viscoelastic measurement. Based on the method,
effects of free surface and substrate interface on the segmental dynamics
were discussed. In the case of thin PS films with a thickness of
approximately 200 nm, αa-relaxation process corresponding to
the segmental motion did not show any deviation from the bulk behavior. In
contrast, for the films thinner than about 50 nm, the relaxation time
distribution for the αa-process became broader, probably due to
a mobility gradient in the surface and interfacial regions. When we
sandwiched an ultrathin PS film between SiOx layers, another relaxation
process, in addition to the original αa-process, appeared at a
higher temperature side that we assigned to the interfacial αa-relaxation
process. However, this was never seen for an ultrathin PS
film between Au layers, implying that restriction from the substrate
interface might be weak in this case. 相似文献
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Fen Wu Linyu Song Yiping Guo Song Jin Enbing Bi Han Chen Huanan Duan Hua Li Hezhou Liu Hongmei Kang 《Applied Physics A: Materials Science & Processing》2014,117(3):1301-1306
The photovoltaic (PV) effect of a bilayer anatase TiO2/BiFeO3 (BFO) film has been studied. The 20-nm ultrathin BFO layers were deposited on the fluorine-doped tin oxide (FTO) glass substrates by the chemical solution deposition method. An anatase TiO2 layer is deposited subsequently on the BFO surface via a screen-printing technique. It is found that the FTO/TiO2/Au cell exhibits negligible PV effect under solar exposure, while the one after introducing an ultrathin BFO film between TiO2 and FTO leads to a considerable PV effect with an open-circuit voltage of ?0.58 V and a photocurrent density of 18.27 µA/cm2. The FTO/BiVO4 (BVO)/TiO2/Au cell was constructed to investigate the underlying mechanism for the observed effect. A negligible PV effect of the FTO/BVO/TiO2/Au cell indicates that the PV effect of the FTO/BFO/TiO2/Au cell arises mainly from a built-in electric field in the BFO film induced by the self-polarization. Our work opens up a new path to utilize TiO2 and may influence the future design of solar cells. 相似文献
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The collective excitation in Al films deposited on Si(1 1 1)-7 × 7 surface was investigated by high-resolution electron-energy-loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). At the Al film thickness d < 10 ML, the surface plasmon of Al film has only a small contribution to the observed energy-loss peaks in the long wavelength limit (q∥≈0), while its contribution becomes significant for q∥>d-1. More interestingly, for thin Al films, the initial slope of the surface plasmon dispersion curve is positive at q∥∼0, in a sharp contrast to bulk Al surface where the energy dispersion is negative. These observations may be explained based on the screening interaction of the space charge region at the Al-Si interface. 相似文献
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A. V. Belousov V. A. Kovarskii 《Journal of Experimental and Theoretical Physics》1998,87(6):1053-1057
We examine nonradiative transitions in molecules with allowance for the effect of a classical polar exterior medium on tunneling
charge transport. The approach allows for the vibrational frequencies of a molecule in the electron transition. In the case
of slow fluctuations, the theory predicts a low-temperature (non-Arrhenius) increase in the tunneling nonradiative transition
rate, and the results agree qualitatively with the experimental data. When the fluctuations of the exterior medium are rapid,
at certain values of the molecular parameters the tunneling decay rate is found to decrease with increasing temperature because
the conditions needed for resonant tunneling are violated.
Zh. éksp. Teor. Fiz. 114, 1944–1953 (December 1998) 相似文献