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Mnx Zr1-x O2 (MnZO) thin films were grown by pulsed-laser deposition on single crystalline yttria-stabilized zirconia (YSZ) and a-plane sapphire substrates with manganese contents from 0 up to about 50 at.%. A fully stabilized cubic structure occurs for Mn contents x equal or larger than 20 at. % on YSZ substrates. For x ≈0.5, phase separation of Mn-oxides occurs. Below 11 at. %, only the monoclinic phase is observed. The thin films are electrically insulating up to x = 0.3. By further increasing the Mn content or by reducing the structural quality, the resistivity ρ decreases from 3×109Ωcm down to 3×104Ωcm. For MnZO thin films on a-plane sapphire substrates, Seebeck-effect measurements verify a transition from p-type conductivity to n-type conductivity around 500 K with increasing temperature, which is probably governed by an enhanced ionic conduction. Cathodoluminescence measurements clearly show a Mn-related emission at about 2.8 eV, correlated to an Mn-induced electronic state in the bandgap of MnZO. From electron paramagnetic resonance measurements and x ray photoelectron spectroscopy, we conclude that both Mn3+ and Mn4+ is present in our MnZO thin films. [ABSTRACT FROM AUTHOR]

Ferromagnetic ordering is found for both undoped and Mn-doped zirconia (ZrO2 : Mn) thin films with 0 at% #8804; Mn #8804; 50 at% grown homoepitaxially on ZrO2 : Y2O3(0 0 1) substrates. Highly crystalline films show ferromagnetic saturation magnetization and coercive field at room temperature up to 1 emu cm-3 and 50mT, respectively. The Curie temperature is in all ferromagnetic samples above 300 K. Comparing optimum films with different Mn content, cubic ZrO2 :Mn films with about 25 at% Mn show reproducibly the highest magnetization, in relation to monoclinic and tetragonal films. In contrast, less crystalline films grown heteroepitaxially on LaAlO3(0 0 1) or under non-ideal conditions show negligible magnetic effects. The fraction of paramagnetically active Mn atoms in a ZrO2 film with 27% Mn at 5K is only about 1/5 of the incorporated Mn atoms, corresponding well to the share of 20% Mn4+ in XPS. Magnetic trace impurities in the 100 ppm range cannot account for the observed effects. Our results indicate that the observed defect-induced magnetic ordering in nominally non-magnetic zirconia thin films requires a certain balance of overall crystallinity, dislocation density and film mosaicity. [ABSTRACT FROM AUTHOR]

Abstract: Growth control of nonpolar and polar quantum wells (QWs) is demonstrated by in situ RHEED during the pulsed laser deposition process. Nonpolar QWs were grown homoepitaxially on m-plane and on a-plane ZnO single crystals. For m-plane () ZnO QWs we report a change of growth mode from a two dimensional layer by layer growth evidenced by RHEED oscillations to the formation of surface nanostripes as observed by atomic force microscopy. The aspect ratio of the self organized nanostripes depends on the oxygen partial pressure. a-lane () ZnO QW-structures show a smooth surface with a rms-roughness of 0.3nm. Homoepitaxial nonpolar QWs do not show the quantum-confined Stark effect while polar quantum wells on a-plane sapphire does with an internal electric field of approximately 0.53MV/cm. Furthermore, by implementing a low temperature buffer layer, the interface quality of heteroepitaxially grown polar QWs on a-plane sapphire substrates is considerably improved. RHEED oscillations were observed during the whole growth of such QWs. [Copyright &y& Elsevier]

Abstract: Arabinogalactan protein JC from Jatropha curcas seed endosperm (mean molecular weight 140kDa) was isolated by cold water extraction and characterized concerning sugar and amino acid composition. At 10 and 100µg/mL JC stimulated mitochondrial activity (MTT test) of human skin cells (HaCaT keratinocytes, fibroblasts) and the ATP status of primary keratinocytes. JC did not influence the cellular proliferation, while primary keratinocytes were triggered into differentiation status. Investigations on a potential mode of action of JC were performed on complex organotypic skin equivalents. JC induced the production of HGF, KGF and TGFβ, with TGFβ being the main inductor for the differentiation-inducing effect of JC. Also the expression of GM-CSF was stimulated strongly by JC. This in vitro activity profile indicated JC to be a potent inductor of cellular differentiation via stimulation of growth hormones and TGF-β-induced cell signaling. [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of single quantum wells grown by pulsed laser deposition on sapphire substrates as well as on ZnO substrates were studied by photoluminescence measurements. The transition energy of the excitons shows a clear blue shift with decreasing well width due to the quantum confinement. A detailed comparison of our results with the literature indicates the lack of a stringent theory to calculate the exciton transition energies. The experimentally determined full width of half maximum (FWHM) of the luminescence of hetero- and homoepitaxial grown ZnO quantum wells compared with the calculated ones suggests that an additional contribution has to be taken into account to determine the luminescence linewidth correctly. We assume an additional alloy disorder in the quantum well itself due to the diffusion of Mg. Using time-resolved photoluminescence we found a monoexponential decay in the quantum well. [Copyright &y& Elsevier]

We report on luminescence properties from T=2 K up to room temperature of ZnO/Zn1-xCdxO/ZnO double heterostructures grown by pulsed-laser deposition on a-plane sapphire substrates. Depending on the growth conditions, the spectral position of the Zn1-xCdxO related maximum has been tuned from 3.19 to 3.056 eV, corresponding approximately to Cd contents between 2.1% and 5.6%. Independent of x we observe intense phonon replicas of the photoluminescence (PL) maximum. The quenching of the luminescence intensity indicates the presence of two thermal activation energies, one of them being assigned to the delocalization of excitons from donors. The temperature-dependent PL spectra exhibit the so-called "S-shape" behavior as function of temperature for the Zn1-xCdxO due to the superposition of the usual S-shape, caused by the alloy, and a change in the peak character from donor-bound exciton to free exciton. [ABSTRACT FROM AUTHOR]