Abstract: Electron, hole, and exciton states in the stacks composed of three strained (InGa)As quantum rings were computed. We found considerable influence of strain on both the single particle and exciton spectra, while the oscillator strength for exciton recombination is reduced by the magnetic field.

Abstract: ITEM specimens of a LaAlO3/SrTiO3 multilayer are prepared by FIB with internal lift out. Using a Ga+1 beam of 5 kV, a final cleaning step yielding top, top-angle, side, and bottom-angle cleaning is performed. Different cleaning procedures, which can be easily implemented in a dual beam FIB system, are described and compared; all cleaning types produce thin lamellae, useful for HRTEM and HAADF-STEM work up to atomic resolution. However, the top cleaned lamellae are strongly affected by the curtain effect. Top-angle cleaned specimens show an amorphous layer of around 5 nm at the specimen surfaces, due to damage and redeposition. Furthermore, it is observed that the LaAlO3 layers are preferentially destroyed and transformed into amorphous material, during the thinning process.

Abstract: Laser-induced plasmas are transient systems rapidly aging in few nanoseconds of evolution. Time-of-flight spectrometry allowed studying initial plasma characteristics based on frozen translational degrees of freedom, hence overcoming intrinsic limitations of optical spectroscopy. Experimental ion velocity distributions were reconstructed as developed during the longitudinal plasma expansion. The obtained onset plasma temperatures are in the range of similar to 18-45 eV depending on the ablated metals. Also the ion angular spreads were found to be a function of ablated metal, e.g., the narrowest for Fe, the broadest for Al, due to different collisional coupling in the plasma population. (c) 2007 American Institute of Physics.

Abstract: Sr2FeMoO6/SrTiO3/CoFe2 trilayers grown by pulsed laser deposition on SrTiO3 (001) are investigated by transmission electron microscopy and electron energy loss spectroscopy. The stack is epitaxial, independent of whether the CoFe2 electrode is grown at 500 or at 50 degrees C. Thus it is possible to obtain epitaxy near room temperature. The SrTiO3/CoFe2 interface is quite sharp, while the Sr2FeMoO6/SrTiO3 interface presents regions of Fe depletion. The chemical composition of the films is close to the nominal stoichiometries. These results could be useful for the growth of heteroepitaxial devices and magnetic tunnel junctions. (C) 2007 American Institute of Physics.

Abstract: We compare the magnetic properties of pure and oxidized Co nanoparticles embedded in an amorphous Al2O3 matrix. Nanoparticles with diameters of 2 or 3 nm were prepared by alternate pulsed laser deposition in high vacuum conditions, and some of them were exposed to O-2 after production and before being embedded. The nanoparticles are organized in layers, the effective edge-to-edge in-depth separation being 5 or 10 nm. The lower saturation magnetizations per Co atom for the samples containing oxidized nanoparticles provide evidence for the formation of antiferromagnetic CoO shells in the nanoparticles. None of the samples with Co/CoO nanoparticles show exchange bias, while vertical hysteresis loop shifts and enhanced coercivities (as compared to samples with pure Co nanoparticles) are observed. This constitutes evidence for the nanoparticles size being in all cases smaller than the critical size for exchange bias. The difference in coercivity versus temperature dependences for the samples with pure and oxidized Co nanoparticles shows that the exchange anisotropy in Co/CoO nanoparticles appears at temperatures lower than 50 K. (c) 2007 American Institute of Physics.