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To understand the plasma evolution mechanism of microwave ion source (MIS), a hybrid discharge heating (HDH) mode is proposed. That mode contains two parts: ignition discharge by surface wave plasma (SWP) and ionization by electron cyclotron resonance. Compared with the traditional electron cyclotron heating (ECH) mode, the HDH mode has a wider scope of application for MIS with a chamber diameter smaller than the cutoff size. The spatio-temporal evolution of electric field, power deposition, electron temperature, and electron density of a miniaturized microwave ion source (MMIS) at Peking University is investigated based on the HDH mode. In addition, the MMIS is optimized based on the theoretical results of the HDH mechanism. Preliminary experiments show that a mixed hydrogen continuous wave beam of up to 25 mA at 30 keV can be extracted with a power efficiency of 25 mA/100 W. [ABSTRACT FROM AUTHOR]

La0.625Ca0.375MnO3 (LCMO) films with thicknesses between 7 and 54 nm were epitaxially grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) [LSAT (001)] substrates by using pulsed laser deposition. For this epitaxial system, antiferromagnetic-insulator (AFI) state can be controlled by changing the film thickness and annealing time with various epitaxial strain states, although this phenomenon is absent in the relatively thick films or bulk samples. The consistency between magnetization and resistivity data suggests all these interesting transport behaviors are attributed to the fluctuation of AFI volume fractions and their instability. Especially, there are huge low-field magnetoresistance over -54% (32 nm) at 0.1 T and enhanced magnetoresistance over a broad temperature range. Based on these above results, annealing induced coherent evolutions of biaxial strain and AFI phase in LCMO epitaxial films is a consequence of the strain-driven orbital ordered state, and this may make an approach for a possible application of strongly correlated electron devices. [ABSTRACT FROM AUTHOR]

Focuses on the fabrication of epitaxial La0.35Nd0.35Sr0.3Mn03 (LNSMO) thin films and Pb(Zr052Ti0.48)03 (PZT)/LNSMO heterostructures. Use of pulsed laser deposition method; Oxygen concentration in the LNSMO films; Electrical measurements of platinum/PZT/LNSMO ferroelectric capacitor.

Deals with a study on the effect of annealing in reduced oxygen pressure on the electrical transport properties of epitaxial thin films and bulk materials. Details on the experiment; Results and discussion; Conclusions.

Provides information on a study which examined the possible mechanism associated with the effect of annealing on the diamagnetic transition of bismuth, strontium, calcium, copper and oxygen crystals. Characterization by x-ray diffraction; Growth of crystals after annealing; Variations in crystallinity.

Presents a study which examined the intensity distribution of the modulation-related reflections in exactly the b*c* reciprocal plane for high quality bismuth[sub2]strontium[sub2]calcium copper[sub2]oxygen[suby] crystal. Experimental procedure; Results; Discussion.

Presents information on a study which described two different micromodels in zinc oxide (ZnO) varistors containing seed grains. Establishment of micromodel; Effect of the amount of seed grains on characteristics of ZnO varistors; Measurement of the electric field.

Presents information on a study which examined the phase decomposition in a high quality bismuth compound single crystal annealed in air, using x-ray diffraction and scanning electron microscopy. Methods; Results; Discussion.

La0.625Ca0.375MnO3 films have been epitaxially grown on the (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) substrates at different oxygen pressures and show varying tetragonal distortion. Results indicate a tendency that larger tetragonal distortion can stabilize the antiferromagnetic-insulator phase in the thin films. Colossal magnetoresistance (CMR) and anisotropic magnetoresistance (AMR) have been greatly enhanced only in the strained films over a broad temperature, probably responding to the anisotropic fluctuation of the nanoscale orientation-ordered patterns near the temperature of the phase separation region or metal-insulator transition. Hence, the inhomogeneous phase competition may contribute to the CMR and the extraordinary AMR effect for manganite devices. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the oxygen loss effect under both reducing and oxidizing thermal treatments on superconductivity of single crystal bismuth[sub2]strontium[sub2]calcium copper[sub2]oxygen[sub8+y]. Methods; Results; Discussion.

Presents a study which induced phase decomposition in high quality Bi[sub2]Sr[sub2]CaCu[sub2]O[suby] single crystals by annealing treatments. Association of phase decomposition with the oxygen content in the annealing atmosphere; Influence of the evaporation of bismuth on the phase segregation in the annealing process; Changes in the structure of the single crystal surface.

The 4d and 5d transition metal oxides have exhibited a wide spectrum of attracting phenomena. Here, we demonstrate modulations on crystal structure, electrical properties, and spin-orbit couplings (SOCs) in perovskite CaIr1−xRuxO3 (CIRO, 0 ≤ x ≤ 1) thin films. First, all our coherently-grown CIRO films exhibit the orthorhombic perovskite structure, of which the orthorhombicity is tuned by the doping level x. This is different from the post-perovskite structure that is usually observed in the bulk CaIrO3. Second, the metal-semiconductor transition in the perovskite CIRO layers is triggered by changing either the doping level or the layer thickness. Our data suggest the important roles of SOC and disorders in determining the electrical properties in perovskite CIRO layers. Third, the sign reversal of Hall coefficient in CIRO films reveals the complex evolution of electronic structure depending on x and temperature, suggesting the perovskite CIRO films as a new accessible platform for investigating rich physics in 4d and 5d transition metal oxides. [ABSTRACT FROM AUTHOR]

The effect of deposition oxygen pressure (PO) on phase separation (PS) induced in epitaxial La0.67Ca0.33MnO3/NdGaO3(001) films was investigated. Fully oxygenated films grown at high PO are anisotropically strained. They exhibit PS over a wide temperature range, because of the large orthorhombicity of NdGaO3 substrates. The paramagnetic insulator-to-ferromagnetic metal (FM) and FM-to-antiferromagnetic insulator (AFI) transitions gradually shift to lower temperatures with decreasing PO. The AFI state is initially weakened (PO ≥ 30 Pa), but then becomes more robust against the magnetic field (PO < 30 Pa). The out-of-plane film lattice parameter increases with decreasing PO. For films grown at PO ≥ 30 Pa, the slight oxygen deficiency may enlarge the lattice unit cell, reduce the anisotropic strain, and suppress the AFI state. Films deposited at PO < 30 Pa instead experience an average compressive strain. The enhanced compressive strain and structural defects in the films may lead to the robust AFI state. These results aid our understanding of PS in manganite films. [ABSTRACT FROM AUTHOR]

The control of charge-ordering-insulating (COI) phase in epitaxial La1-xCaxMnO3/NdGaO3(001) (x=0.30–0.45) thin films with essentially the ferromagnetic metal ground state as observed for the bulk counterparts has been realized via the anisotropic strain relaxation. This epitaxial system is special in that there is a negligible average lattice mismatch but a large anisotropic strain in between the film and the substrate. By changing the film thickness, postannealing temperature, along with the doping level for strain relaxation, the COI phase in the films can be tuned to either melt completely under 1 T, producing a huge low-field magnetoresistance (MR) in a wide temperature range (e.g., for the 20 nm film with x=0.33 and annealed at 780 °C, the MR can be over 70% at 0.2 T and 97% at 0.5 T in 10–200 K), or survive under a high magnetic field of 6 T. The results demonstrate the crucial role of anisotropic strain relaxation in inducing the inhomogeneity in manganites films, thus providing a forward understanding of the strain field in manganite physics. [ABSTRACT FROM AUTHOR]

Perovskite-type transparent and conductive oxide films, Sb-doped SrSnO3 (SSSO), were grown on SrTiO3(001) substrates by the pulsed laser deposition method. It is revealed that the films can be grown at relatively lower temperatures and show high single crystallinity with a cubic perovskite structure with lattice constant of 4.036 Å. These films show good optical transmittance in the visible range, with the direct allowed band gap of 4.53 eV, and behave as an n-type semiconductor with resistivity of 23 mΩ cm at room temperature. The effect of growth temperature on structural, electrical, and optical properties of the SSSO films was probed, and a diode based on n-SSSO/p-La0.67Ca0.33MnO3 structure was also demonstrated. [ABSTRACT FROM AUTHOR]

We report that (La0.07Ba0.93)SnO3 films grown epitaxially on SrTiO3(001) substrates by laser ablation at 760 °C show a cubic perovskite structure of lattice constant 4.121 Å, excellent optical transmittance in the visible range, and a weak metallic behavior with low resistivity of about 4 mΩ cm within 10–300 K. The transparent perovskite oxide films are n-type conductors, with carrier concentration and mobility at room temperature of about 2×1021 cm-3 and 0.69 cm2/V s, respectively, and a direct allowed band gap of 4.02 eV. The effect of deposition temperature on structural, optical, and electric properties of the Sb-doped Ba(Sn0.93Sb0.07)O3 films was also demonstrated. [ABSTRACT FROM AUTHOR]