Confined three-dimensional plasmon modes inside a ring-shaped nanocavity on a silver film imaged by cathodoluminescence microscopy

The confined modes of surface plasmon polaritons in boxing ring-shaped nanocavities have been investigated and imaged by using cathodoluminescence spectroscopy. The mode of the out-of-plane field components of surface plasmon polaritons dominates the experimental mode patterns, indicating that the electron beam locally excites the out-of-plane field component of surface plasmon polaritons. Quality factors can be directly acquired from the spectra induced by the ultrasmooth surface of the cavity and the high reflectivity of the silver (Ag) reflectors. Because of its three-dimensional confined characteristics and the omnidirectional reflectors, the nanocavity exhibits a small modal volume, small total volume, rich resonant modes, and flexibility in mode control.

Evidence for thermal spin-transfer torque

Large heat currents are obtained in Co/Cu/Co spin valves positioned at the middle of Cu nanowires. The second harmonic voltage response to an applied current is used to investigate the effect of the heat current on the switching of the spin valves. Both the switching field and the magnitude of the voltage response are found to be dependent on the heat current. These effects are evidence for a thermal spin-transfer torque acting on the magnetization and are accounted for by a thermodynamic model in which heat, charge and spin currents are linked by Onsager reciprocity relations.

Effects of annealing on the ferromagnetism and photoluminescence of Cu-doped ZnO nanowires

Room temperature ferromagnetic Cu-doped ZnO nanowires have been synthesized using the chemical vapor deposition method. By combining structural characterizations and comparative annealing experiments, it has been found that both extrinsic (CuO nanoparticles) and intrinsic (Zn(1-x)Cu(x)O nanowires) sources are responsible for the observed ferromagnetic ordering of the as-grown samples. As regards the former, annealing in Zn vapor led to a dramatic decrease of the ferromagnetism. For the latter, a reversible switching of the ferromagnetism was observed with sequential annealings in Zn vapor and oxygen ambience respectively, which agreed well with previous reports for Cu-doped ZnO films. In addition, we have for the first time observed low temperature photoluminescence changed with magnetic properties upon annealing in different conditions, which revealed the crucial role played by interstitial zinc in directly mediating high T(c) ferromagnetism and indirectly modulating the Cu-related structured green emission via different charge transfer transitions.

Competition between quantum fluctuations and antiferroelectric order in Ru-doped Sr(0.8)Ca(0.2)Ti(1-x)Ru(x)O(3)

The competition between quantum fluctuations and the antiferroelectric state in Sr(0.8)Ca(0.2)Ti(1-x)Ru(x)O(3) is investigated by measuring the low-temperature dielectric permittivity and by Raman spectroscopy. We demonstrate the significant impact of quantum fluctuations on the stability of the antiferroelectric polar order. It is revealed that the structural phase transitions can be modified by the quantum fluctuations, enhancing the stability of the high-symmetry phase and suppressing the antiferroelectric transitions. More importantly, a quantum antiferroelectric state, exhibiting similar behavior as the quantum ferroelectric state in terms of dielectric response, is identified. In addition, the effect of quantum fluctuations on the increasing permittivity at low temperature is also discussed.

Fabrication of oriented ZnO nanorod arrays and their optical performances

The well-aligned ZnO nanorod arrays were fabricated through a simple chemical process under low temperature. The nanorod arrays were characterized by XRD, SEM, TEM, HRTEM and SAED, and their optical performances were investigated with Raman and PL spectroscopy. The results show that the as-prepared ZnO nanorod arrays are dense, the individual ZnO nanorod is hexagonal shape and grows along c-axis perpendicular to the substrate surface with good single crystal in nature. The Raman property of nanorod arrays displays change with the altering the preparation conditions. Moreover, the PL performances of ZnO nanorod arrays exhibit tunable character with adjusting the synthesis conditions.

Polarity determination for the CdxZn1-xS nanocombs by EELS

Comb-like Cd(x)Zn(1-x)S nanostructures have been synthesized by one-step metallo-organic chemical vapor deposition (MOCVD). The microstructure and composition were characterized by analytical transmission electron microscopy (TEM). The ribbon of the comb-like structure is along [2-1-10] (the a-axis), and the nanotips are along [0001] (the c-axis). The atomic location by channeling-enhanced microanalysis (ALCHEMI) technique was used to determine the polarity of the crystal via electron energy-loss spectroscopy (EELS). The thickness dependence, delocalization and beam convergent effect are discussed here. The investigations reveal that the growth mechanism is consistent with the asymmetric growth.

Calibration of the spring constant of AFM cantilever

Several methods have been developed in recent years to calibrate the spring constant of atomic force microscopy (AFM) cantilever. In the present work, an effective and practical improvement is made on these methods to provide a more convenient calibration method. Simplifying the originally tedious procedures by just examining the cantilever's dimensions in scanning electron microscopy (SEM) and the resonance frequency of the cantilever from Q curves in AFM system, the spring constants of different cantilevers are calculated by the methods of Cleveland and Sader. The results are close to the nominal values provided by the manufacturers, which indicates that simplifying the procedures is valid and reliable. Moreover, it shows that spring constants acquiring by Cleveland method is more close to their nominal values than Sader's method does.

Non-exponential photoluminescence decay dynamics of localized carriers in disordered InGaN/GaN quantum wells: the role of localization length

In this article, we report a combined experimental and theoretical study on the luminescence dynamics of localized carriers in disordered InGaN/GaN quantum wells. The luminescence intensity of localized carriers is found to exhibit an unusual non-exponential decay. Adopting a new model taking the radiative recombination and phonon-assisted hopping transition between different localized states into account, which was recently developed by Rubel et al., the non-exponential decay behavior of the carriers can be quantitatively interpreted. Combining with precise structure characterization, the theoretical simulations show that the localization length of localized carriers is a key parameter governing their luminescence decay dynamics.

Electron microscopy investigation of gallium oxide micro/nanowire structures synthesized via vapor phase growth

Large-scale micro/nanosized Ga(2)O(3) structures were synthesized via a simple vapor p9hase growth method. The morphology of the as-grown structures varied from aligned arrays of smooth nano/microscale wires to composite and complex microdendrites. We present evidence that the formation of the observed structure depends strongly on its position relative to the source materials (the concentration distribution) and on the growth temperature. A growth model is proposed, based on the vapor-solid (VS) mechanism, which can explain the observed morphologies.

Microstructural and compositional characteristics of GaN films grown on a ZnO-buffered Si (111) wafer

Polycrystalline GaN thin films have been deposited epitaxially on a ZnO-buffered (111)-oriented Si substrate by molecular beam epitaxy. The microstructural and compositional characteristics of the films were studied by analytical transmission electron microscopy (TEM). A SiO(2) amorphous layer about 3.5 nm in thickness between the Si/ZnO interface has been identified by means of spatially resolved electron energy loss spectroscopy. Cross-sectional and plan-view TEM investigations reveal (GaN/ZnO/SiO(2)/Si) layers exhibiting definite a crystallographic relationship: [111](Si)//[111](ZnO)//[0001](GaN) along the epitaxy direction. GaN films are polycrystalline with nanoscale grains ( approximately 100 nm in size) grown along [0001] direction with about 20 degrees between the (1l00) planes of adjacent grains. A three-dimensional growth mode for the buffer layer and the film is proposed to explain the formation of the as-grown polycrystalline GaN films and the functionality of the buffer layer.

TEM investigations on ZnO nanobelts synthesized via a vapor phase growth

Unusual ZnO nanostructures have been successfully synthesized via selenium-controlled chemical vapor phase growth on Si (111) substrates at about 500 degrees C. The microstructure and chemical compositional characteristics of the ZnO nanomaterials have been systematically investigated by means of analytical transmission electron microscopy (TEM), including energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. Most of the nanostructures have a belt-like morphology with typical widths of approximately 150 nm and lengths up to several micrometers. All the investigated materials are found to be stoichiometric ZnO with a hexagonal crystal structure. The growth directions for the nanobelts are found to be [1010] and [2110] respectively. Regular-triangle and needle-like heads with diameters only approximately 25-35 nm have been found in the straight nanobelts. High-resolution TEM images indicate that all the nanostructures are single crystals and free of defects. The growth mechanisms of such interesting and unique morphologies are briefly discussed.

[A study on pathogenesis and therapy of hemorrhagic fever with renal syndrome]

581 early cases of typical hemorrhagic fever with renal syndrome (HFRS) were dynamically studied on the clinical manifestations and laboratory findings from 1986 to 1989. All the patients were treated with various methods. The results showed: (1) The manifestations of microvascular damage, proteinuria and thrombocytopenia can be found at the first day of the onset in 80.0%, 72.2% and 33.3% respectively. In a word, the characteristic features of HFRS appear at the onset of the disease. (2) In 446 early cases the initial severity of the disease corresponded with the final severity at a rate of 89.2%; it indicated that the damage of HFRS may result from the first attack. (3) The time of the onset, peak and persistence of all the characteristic features were similar; it is suggested that the course of HFRS may be self-limited. (4) Based on the clinical understanding and the effective results in the 446 early cases treated with fluid therapy alone, we consider that the effective treatment of HFRS is early and reasonable fluid therapy.

[A study of the role of plasma thromboxane B2 and 6-keto-prostaglandin F1 alpha in epidemic hemorrhagic fever]

Plasma concentrations of Thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were dynamically measured with radioimmunoassay in 30 patients of epidemic hemorrhagic fever (EHF). It was found that the levels plasma TXB2 significantly increased and 6-keto-PGF1 alpha decreased in EHF patients as compared with those in controls. The more severe the patient's condition, the higher the level of TXB2 and the lower the level of 6-keto-PGF1 alpha. The ratio of TXB2/6-keto-PGF1 alpha was parallel with the severity of the patient's condition. Plasma TXB and TXB2/6-keto-PGF1 alpha ratio increased significantly in the hemorrhagic and shock group, while 6-keto-PGF1 alpha decreased significantly in the shock group. The results showed that there is a distinct imbalance of TXA2-PGI2 mediated through the increase of TXA2 and decrease of PGI2 in EHF. The imbalance of TXA2-PGI2 participates in the pathogenesis and pathophysiology of hemorrhage, shock and renal dysfunction.