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Partially self-polarized BiFeO3 (BFO) film was fabricated on Pt(111)/Ti/SiO2/Si substrate by a metal organic decomposition process at 480 °C. The influence of soaking times on leakage properties was discussed. The soaking times considered were those that could keep the leakage currents being measured in a steady state condition during the leakage tests. The length of soaking time during leakage measurement should be greater than or equal to 500 ms to rule out the contribution of backswitching to leakage properties. Different leakage characteristics induced by the built-in negative field occurred under positive and negative fields. The "flat-band" feature of the leakage current curves may result from competition between domain switching and the switching of defect complexes. It is suggested that the "unswitched" mode should be adopted during leakage measurement in BFO films. Additionally, negative bias should be adopted in negatively polarized BFO films and positive bias should be adopted in positively polarized BFO films.

Zn-doped Na0.5Bi0.5TiO3 (Zn: NBT) thin films were prepared from precursor solutions with different concentrations (0.08, 0.20 and 0.35 M) via a metal organic decomposition process. The effects of the mole concentration of precursor solution on crystallization and electrical properties were investigated. All the films exhibit polycrystalline perovskite structure. The increasing degree of predominant (110) orientation with the decrease of the concentration is ascribed to the highly diluted of the solution, leading to the local grain-on-grain growth. Compared with other films, the 0.20 M-film exhibits a strong nonlinear dependence of the dielectric constant on the applied voltage due to the improvement of crystallinity and insulating property. Furthermore, the effect of applied voltage on the dielectric tunability for 0.20 M-film is discussed. A higher tunability of 36.8% and figure of merit of 7.4 in Zn: NBT film can be observed at ±16 V and 100 kHz.

The effects of annealing temperature on the structure, morphology, ferroelectric and dielectric properties of Na0.5Bi0.5Ti0.99W0.01O3+δ (NBTW) thin films are reported in detail. The films are deposited on indium tin oxide/glass substrates by a sol-gel method and the annealing temperature adopted is in the range of 560–620 °C. All the films can be well crystallized into phase-pure perovskite structures and show smooth surfaces without any cracks. Particularly, the NBTW thin film annealed at 600 °C exhibits a relatively large remanent polarization (Pr) of 20 μC/cm2 measured at 750 kV/cm. Additionally, it shows a high dielectric constant of 608 and a low dielectric loss of 0.094 as well as a large dielectric tunability of 62%, making NBTW thin film ideal in the room-temperature tunable device applications.

Na 0.5 Bi 0.5 (Ti 0.99 Zn 0.01 )O 3 (NBTZn) thin films were deposited on the indium tin oxide (ITO)/glass substrates annealed under different atmospheres (air, N 2 , O 2 , O 2 /N 2 ) via a metal organic decomposition process. The effects of annealing atmosphere on crystallization and electrical properties were mainly investigated. All the thin films exhibit single perovskite structures with predominant (110) orientation. Large grains are observed in N 2 due to the high content of oxygen vacancy. For the film annealed in O 2 /N 2 atmosphere, the lower leakage current density and higher dielectric tunability can be obtained, which may be ascribed to the improvement of crystallization with more homogeneous grain sizes and dense microstructure. Also, the effects of measuring frequency on dielectric constant–electric field characteristic are discussed. A higher tunability of 47.6% and figure of merit of 7.9 at 300 kV/cm and 100 kHz for NBTZn film can be observed.

Na 0.5 Bi 0.5 (Ti,Zn)O 3-δ (NBTZn) thin films with various single-coated layer thicknesses (35, 25, 20 and 15 nm) annealed at 550 °C were fabricated on indium tin oxide/glass substrates using a metal organic decomposition process. The effects of single-coated layer thickness on the crystal structure, morphology, leakage current as well as dielectric tunability are investigated. All the films exhibit polycrystalline perovskite structures with different relative intensities of (110) peaks. The highly preferred orientation in the film of 20 nm per layer (nm/ l ) is consistent with the typical columnar structure observed from cross-sectional morphology. Also, for the film with 20 nm/ l , it exhibits the higher tunability of 43.2% and figure of merit of 8.1 at 240 kV/cm and 100 kHz due to well-crystallization and lower content of defects. Meanwhile, the effects of electric field on the tunability for all the NBTZn films and frequency on the dielectric constant-electric field loops for the film of 20 nm/ l are discussed.

Na0.5Bi0.5(Ti0.94Fe0.06)O3−δ (NBTFe) thin film was deposited on indium tin oxide coated glass substrate by a metal organic decomposition process. The aging effect on the dielectric properties was mainly studied by the dielectric constant–electric field (er–E) curves. Obvious aging characteristic of abnormal double butterfly er–E loops was observed in the NBTFe film. This phenomenon can be attributed to the polarization backswitching behavior under the effect of defect dipoles. Furthermore, the double curve can gradually transform into a typical single one during the course of increasing the applied electric field or decreasing the measuring frequency, which can be explained by the progressively enhanced de-aging effect. These present results are discussed based on defect chemistry by the symmetry-conforming principle of defect dipoles.

The excised rat kidney slices were investigated using a simplified diffraction-enhanced imaging (DEI) configuration with only two crystals: the first one working as monochromator and the second one working as analyzer in the Bragg geometry that was developed at Beijing Synchrotron Radiation Facility (BSRF). Many fine anatomic structures of the sliced rat kidneys with thickness of 2 mm and 120 gm can be distinguished clearly in the DEI images that were obtained at the shoulder of a rocking curve. The authors would like to emphasize that the thick and thin slices DEI provides very different images; in the thick sample only the structure with the big density gradient or that near the surface where X-ray comes out can be distinguished, while in the thin ones some fine structures, which can not be distinguished at the thick sample under the same condition, can be seen very clearly. The reason related with the counteraction of delta(x, y, z) gradient in the integral process along the X-ray path inside the thick sample is discussed. (c) 2005 Elsevier B.V. All rights reserved.

The surface segregation of phosphorus in silicon at low temperatures is studied by using delta doping structures grown by molecular beam epitaxy. The samples are characterized by X-ray crystal truncation rod (CTR) scattering using synchrotron radiation as the light source. The l/e decay length of P segregation and segregation barrier energy are obtained by fitting the CTR curves within kinematical approximation of X-ray diffraction theory. The surface segregation of P is strong at a growth temperature of 450 degrees C, with a l/e decay length of 14 nm, while for growth temperatures below 350 degrees C, P segregation is negligible with a l/e decay length not larger than 4 nm. The segregation barrier energy is determined to be 0.43 eV. (c) 2005 Elsevier B.V. All rights reserved.

We report on an experimental study of spin-dependent exciton formation in films of π-conjugated polymers. We employed a spectroscopic/magnetic resonance technique, namely the photoinduced absorption (PA)-detected magnetic resonance technique, and showed that non-geminate recombination pairs of polarons form singlet excitons more efficiently than triplets. The experimental proof for this is achieved by detection of a resonant decrease of triplet exciton absorption and resonantly enhanced singlet photoluminescence (PL). In addition, resonantly enhanced absorption is observed which we assign to a singlet exciton precursor. Our study has important implications regarding the efficiency that can be achieved in polymer light-emitting diodes (PLEDs).