Thin insulating and c-axis oriented films of La2CuO4 are grown using a molecular beam epitaxy technique. Subsequently, these films are oxidized electrochemically using a 1N KOH solution. This approach is used to induce superconductivity, leading to a maximum Tc0 of 31 K,, measured both resistively and inductively. The surface morphology, lattice constants and the resistivity before and after the electrochemical treatment are compared. 相似文献
Zinc oxide (ZnO) nanocrystals doped with different groups of impurities, e.g., Li, Na, Cu, Pr and Mg synthesized by solid-state reaction method under similar conditions exhibit different morphology. XRD showed monophasic wurtzite structure but change in lattice parameters and Zn-O bond length indicates incorporation of dopant ion in ZnO lattice. The morphology of ZnO nanocrystals exhibited striking dependence on type of dopant ion with the shape changing from nanorods, spherical to petal like particles. Photoluminescence (PL) shows pronounced UV emission and negligible visible emission for Li, Na and Cu doped ZnO nanocrystals with peak positions coinciding with that of undoped ZnO. Whereas signature emission of Pr3+ ion as well as broad visible emission from Mg doped ZnO revealed the role of intra gap metastable states formed by the dopant ion in the emission process. 相似文献
The effect of nanosize grains to enhance dielectric tunability in chemically prepared (Pb1−xSrx)TiO3 (PST) (x=0.1 to 0.5) thin films has been observed. The grain size is evaluated from X-ray diffraction patterns and atomic force microscopy.
The average grain size lies in the range of 80–23 nm with varying Sr content. The nanosize grains in the PST films control
the dielectric behavior up to the higher frequency region and exhibit large tunability with low loss factor at room temperature.
The current–voltage characteristics show a large tunability as electron transport takes place within a highly resistive Fermi
gap. 相似文献
Zinc oxide (ZnO) nanorods with hexagram cross-section were prepared by vapor-phase transport method. The growth mechanism
of the nanorods was discussed by considering diffusion effects of reactant gasses at high supersaturation. A strong ultraviolet
peak at 391 nm and a weak visible band depending on the excitation wavelength were observed under the excitation by infrared
femtosecond laser. The UV and the visible emission were respectively attributed to four-photon induced photoluminescence (FPPL)
and third harmonic generation (THG). The characteristics and the generation mechanism of the FPPL were discussed. 相似文献
Nanocrystalline silicon material has made rapid progress in the last several years and at present it can be defined as real
device quality as a photoactive layer for solar cells. A number of innovative ideas, such as the deposition at the crystalline
to amorphous transition, at high pressure depletion condition, by taming of the ion energy, by grading of the material growth,
at reduced unwanted dopant incorporation, have helped to reach an efficiency of 10% for single junction nanocrystalline silicon
cells. In situ plasma and gas phase diagnosis have contributed to the fast optimisation of deposition process parameters.
Deposition rate, open circuit voltage and light confinement are some of most critical issues that are currently pursued. Materials
with a defect density as low as 1015 cm−3 have been made, however, they are still not good enough for n–p junctions; the device structure is still of drift type in
a p–i–n or n–i–p configuration. 相似文献
Phase transformations of an electropulsing-treated ZA22 alloy were studied after tensile deformation by using scanning electron
microscopy and transmission electron microscopy. It was found that electropulsing tremendously accelerated phase transformations
consequentially in the two stages: (a) quenching from supersaturated state approaching the final stable state, i.e., α+ε→T′+η, and (b) up-quenching from the final stable state to a higher temperature state, i.e., T′+η→α+ε. The mechanism of electropulsing-induced phase transformation is discussed from the point of view of Gibbs free energy, and
electropulsing kinetics. 相似文献
Microcrystalline silicon thin film pin solar cells with a highly crystallized intrinsic μc‐Si:F:H absorber were prepared by RF‐plasma enhanced chemical vapour deposition using SiF4 as the gas precursor. The cells were produced with a vacuum break between the doped layer and intrinsic layer depositions, and the effect of different subsequent interface treatment processes was studied. The use of an intrinsic μc‐Si:H p/i buffer layer before the first air break increased the short circuit current density from 22.3 mA/cm2 to 24.7 mA/cm2. However, the use of a hydrogen‐plasma treatment after both air breaks without an interface buffer layer improved both the open circuit voltage and the fill factor. Although the material used for the absorber layer showed a very high crystalline fraction and thus an increased spectral response at long wavelengths, an open‐circuit voltage (VOC) of 0.523 V was nevertheless observed. Such a value of VOC is higher than is typically obtained in devices that employ a highly crystallized absorber as reported in the literature (see abstract figure). Using a hydrogen‐plasma treatment, a single junction μc‐Si:F:H pin solar cell with an efficiency of 8.3% was achieved.
We report new measurements of the rotational spectrum of monodeuterated methane (CH3D) in the range of 690-1200 GHz which allow for an accurate prediction of all lines in the range of the high-resolution spectrometer of the Herschel Space Observatory. Comparison is also made with the previous analysis based on infrared combination differences. Three lines of 13CH3D were measured in natural abundance. 相似文献
The Shubnikov-de Haas (S-dH) results at 1.5 K for AlxGa1−xN/AlN/GaN heterostructures and the fast Fourier transformation data for the S-dH data indicated the occupation by a two-dimensional electron gas (2DEG) of one subband in the GaN active layer. Photoluminescence (PL) spectra showed a broad PL emission about 30 meV below the GaN exciton emission peak at 3.474 eV that could be attributed to recombination between the 2DEG occupying in the AlN/GaN heterointerface and photoexcited holes. A possible subband structure was calculated by a self-consistent method taking into account the spontaneous and piezoelectric polarizations, and one subband was occupied by 2DEG below the Fermi level, which was in reasonable agreement with the S-dH results. These results can help improve understanding of magnetotransport, optical, and electronic subband properties in AlxGa1−xAs/AlN/GaN heterostructures. 相似文献