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We report on ultraviolet photovoltaic effects in a BiFeO3/Nb-doped SrTiO3 heterostructure prepared by a pulsed laser deposition method. The heterostructure exhibits rectifying behaviors in the temperature range from 80 K to 300 K. The photovoltage of heterostructure is about 0.33 V at T = 80 K when it is illuminated by a KrF excimer laser with a wavelength of 248 nm. The peak photovoltages decrease with increasing the temperature because of the accumulation of photogenerated carriers. Moreover, the peak photovoltages of heterostructure almost linearly increase with an increase of the power density of laser at T = 300 K. The results reveal some properties that may be useful for possible applications in multiferroic photoelectric devices. [ABSTRACT FROM AUTHOR]

Bi1-xLaxFe1-yCoyO3 (x=0, 0.1; y=0, 0.05, 0.1) polycrystalline thin films were fabricated on Pt/Ti/SiO2/Si(111) substrates via chemical solution deposition method. X-ray diffraction analysis revealed a phase transition in La–Co codoped BiFeO3 (BFO) thin films. Saturated ferroelectric hysteresis characteristics in La–Co codoped BFO thin films were observed, and the conduction behavior of Bi1-xLaxFe1-yCoyO3 thin films investigated to understand the leakage mechanisms. In the low applied field, the conduction mechanism of Bi1-xLaxFe1-yCoyO3 thin films was found to be dominantly Ohmic. In the high applied field, the conduction mechanisms of pure and La doped BFO thin films were found to be trap-filled-limited and Poole–Frenkel emission, and that of Co doped and La–Co codoped BFO thin films Schottky emission. The dielectric constant of Bi0.9La0.1Fe0.9Co0.1O3 thin film, in the frequency range of 1 to 2000 kHz, was nearly two times higher than that of pure BFO thin film while the dielectric loss tan δ was small at values below 0.07. It was found that saturation magnetization in BFO thin films could be enhanced by La or Co doping, and obviously by La–Co codoping too. [ABSTRACT FROM AUTHOR]

We discuss a newly developed x-ray standing-wave/wedge (swedge) method for probing the composition, magnetization, and electronic densities of states in buried interfaces and layers in spintronic nanostructures. In work based on photoemission, this method has permitted determining concentration and magnetization profiles through giant magnetoresistive (GMR) and magnetic tunnel junctions structures, as well as individual layer densities of states near the Fermi level in a tunnel junction. Using x-ray emission and resonant inelastic x-ray scattering for detection has permitted probing deeper layers and interfaces in a GMR structure. Various future applications of this method in nanomagnetism are suggested, including using more energetic hard x-ray standing waves so as to probe more deeply below a surface and standing-wave excitation in spectromicroscopy to provide depth sensitivity. [ABSTRACT FROM AUTHOR]

Optical properties of ZnO quantum dots (QDs) capped with polyvinyl pyrrolidone (PVP) molecules have been investigated. It is demonstrated that surface modification by PVP can dramatically change the emission spectra of the ZnO QDs. At the optimized condition with a PVP/Zn[sup 2+] ratio of 3:5, the photoluminescence (PL) spectrum of ZnO QDs shows a strong ultraviolet (UV) emission while the low energy green emission is fully quenched. This is a result of the surface passivation of the ZnO QDs by the PVP molecules. The origin of the green emission is attributed to the surface states associated with oxygen vacancies. Temperature and excitation power dependent PL studies suggest that the UV emission is associated with localized states. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]