An investigation of the structural, magnetic and electronic properties of ≈ 3 nm thick Mn5Ge3 films epitaxially grown on a Ge(1 1 1)-c(2 × 8) reconstructed surface is reported. High resolution transmission electron microscopy and selected area electron diffraction give evidence of 2.2% in-plane compressive strain between the Mn5Ge3 film and the Ge substrate. Magnetooptical Kerr effect measurements show that the films are ferromagnetic with a Curie temperature of ≈ 325 K. The analysis of Ge 3d core level photoelectron spectra of the Mn5Ge3 films allows determining an upper limit of 76 meV for the Ge 3d5/2 core-hole lifetime broadening. The Ge 3d3/2 core-hole lifetime broadening is found to be 15 meV larger than that of the Ge 3d5/2 core hole, because of the existence of a Coster–Kronig decay channel due to the metallic character of Mn5Ge3.

Here, we report an in situ study of the effect of morphological/structural aging processes on polymer-based photovoltaic cell performances. The devices were provided with a fullerene film as a barrier layer between the active element and the metallic cathode. The experimental method adopted consists of the joint use of atomic force microscopy (AFM) and energy dispersive X-ray reflectivity (EDXR), an original coupling particularly effective in the Study of stratified media. These techniques were applied first to the intermediate stages of the device construction and, finally, to a complete cell. The problems related with the surface/interface modifications of the devices elements in operating conditions were investigated in depth, with particular concern on the role of the C-60 barrier layer. The C-60 film surface topography was monitored by AFM experiments during illumination, which evidenced a Surface reorganization of the C-60 layer molecules over time. Conversely, the C-60 film bulk and its interface with the active layer, investigated by EDXR analysis in the same conditions, turned out to remain unchanged. Then the cathode buried interface of a complete cell was studied, by EDXR measurements in working conditions, thus demonstrating that tire C-60 layer guarantees a good structural stability of the cell. In addition, the in situ AFM/EDXR characterization established that the observed reorganization process of the C-60 layer molecules does not affect the film physical barrier role. This finding was confirmed by power conversion efficiency measurements, showing that the C-60/LiF/Al cathode cell efficiency is preserved over time. This work also demonstrates how the morphological properties of organic device layered components, investigated in Situ by the two noninvasive and independent AFM and EDXR techniques, may provide a structural interpretation of the performance preservation or fading.

Human HaCaT cells, exposed for 24 h to a 1 mT (rms) 50 Hz sinusoidal magnetic field in a temperature-regulated solenoid, suffer detectable changes in their biochemical properties and shapes. By using infrared wavelength-selective scanning near-field optical microscopy, we observed changes in the distribution of the inner chemical functional groups and in the cell morphology with a resolution of 80-100 nm.

The stability and degradation of calcium/aluminium cathode organic solar cells are investigated in situ by time-resolved energy dispersive X-ray reflectometry. They combine the good charge carrier separation and transport properties of the poly(3-hexylthiophene-2,5-diyl):C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction blend and the capability of the calcium/aluminium cathode to improve the fill factor and the open circuit voltage, with respect to aluminium cathodes cells. The study focuses on the crucial problem of the device structural/morphological stability in working condition. It aims to detect and control possible morphological variations at the various interfaces and to correlate these changes to the device aging.

The crucial requirement of device stability in the development of organic electronics was addressed. In particular, the nanoscale morphology of bulk heterojunction organic films for photovoltaic applications was studied by time-resolved energy dispersive X-ray reflectometry in synergy with atomic force microscopy analysis. A reorganization of the organic molecules in the film upon illumination was detected. The occurrence of two distinct processes (characterized by a reorganization of the blend bulk and an increase of its surface roughness, respectively) was revealed. Furthermore, the effect of the morphological instability on the device efficiency over time was quantified. Finally, the effect of thermal annealing treatments and of the choice of different cathodes was verified.

The structural, electronic, and magnetic properties of the Mn0.06Ge0.94 diluted magnetic semiconductor, grown at 520 K by molecular-beam epitaxy on Ge(001)2x1, have been investigated. Diluted and highly ordered alloys, containing Mn5Ge3 nanocrystals, were grown. The valence band photoelectron spectrum of Mn0.06Ge0.94 shows a feature located at -4.2 eV below the Fermi level, which is the fingerprint of substitutional Mn atoms in the Ge matrix. Magnetization measurements show the presence of a paramagnetic component due to substitutional Mn atoms and of a ferromagneticlike component due to Mn5Ge3 nanocrystallites. The Mn L-2,L-3 x-ray absorption spectrum of this polyphase film shows no marked multiplet structure, but a bandlike character.

We have measured the X-ray resonant magnetic scattering at the 2p edge of Mn in diluted magnetic semiconductor Mn0.06Ge0.94/Ge(001)2×1 thin films. Large magnetic effects in the resonant reflectivity were observed over a wide temperature range. The asymmetry ratio of the magnetic scattering increases with increasing temperature, in accordance to the temperature dependence of the magnetization obtained from SQUID measurements. This is attributed to the contribution of ferromagnetic Mn5Ge3 nanoclusters present in the Mn0.06Ge0.94 film.

We report on a joint morphological/photoelectrical study of polymer-based photovoltaic (PV) cells in working conditions. The bulk heterojunction devices investigated are based on an active layer of poly(3-hexyl thiophene) blended with methano-fullerene, combining good PV performances with promising stability. The set-up adopted allowed the electrical properties of the device to be directly correlated to the modification of the electrode morphological parameters (thickness and roughness), which were obtained by in situ energy dispersive X-ray reflectometry (EDXR). The results of this joint time-dependent characterization demonstrated how the observed photo-induced oxidation process, limited to the buried electrode interface, is responsible for a fast decrease in the photo-current. The time-resolved measurements allowed to rule out the dynamics of the morphological changes and showed that the interface morphology may be stabilized by annealing treatments, with a significant improvement of the cell efficiency.

We investigated the structural and magnetic properties of MnxGe1−x, with 0.02⩽x⩽0.1. The MnxGe1−x samples were grown on Ge(001)2×1 by molecular beam epitaxy, at a substrate temperature of 520K. The samples were characterized in situ by reflection high-energy electron diffraction and ex situ by high-resolution transmission electron microscopy, energy dispersive X-ray reflectivity and magneto-optical Kerr effect. From microscopy images we evidenced on all samples the presence of Mn5Ge3 nanocrystallites in addition to the MnxGe1−x diluted magnetic semiconductor with an estimated Mn concentration x≈1.5%. The size and the density of the Mn5Ge3 precipitates were found to increase with increasing the Mn concentration x. Magnetic analysis showed ferromagnetism with a Curie temperature of 280K for all samples.

The authors observed changes in the biochemical properties of eukaryotic cells exposed to an ac magnetic field by infrared scanning near-field optical microscopy. They specifically investigated the changes in the distribution of the inner chemical functional groups and in the cell morphology induced by a 24h exposure to a 1mT (rms), 50Hz sinusoidal magnetic field in a temperature-regulated solenoid. These results accentuate the crucial questions—raised by several recent studies—about the impact of low-frequency electromagnetic field on human cells.

We investigate clean and atomic hydrogen exposed beta-SiC(100) 3 x 2 surfaces by synchrotron radiation-based Si 2p core-level photoemission spectroscopy. The clean 3 x 2 surface reconstruction exhibits three surface and subsurface components. Upon hydrogen exposures, those surface and subsurface components are shifted to lower binding energies by large values, indicating significant charge transfer to the surface and subsurface regions, in excellent agreement with the recently discovered H-induced beta-SiC(100) 3 x 2 surface metallization. In addition, the interaction of hydrogen results in a large reactive component at Si 2p supporting an asymmetric charge transfer in the third plane below the surface, in agreement with previous experimental investigations. However, the results are inconsistent with recent ab initio theoretical "frozen" calculations predicting H atom to be in a bridge-bond position.

We investigated the electronic structure of ultra thin interface of organic titanium bis-phthalocyanine TiPc2 deposited oil InAs(001)(4 x 2)c-(8 x 2) clean surface, by means of high-resolution core-levels and valence band (VB) photoelectron spectroscopies. ln4d, As3d, and Cls core levels were measured for different TiPC2 thicknesses up to I monolayer. Surface core level shifts were found on both In4d and As3d core levels. These shifts originate from the interaction between 4 x 2-c(8 x 2) InAs reconstruction and organic molecules suggesting the presence of strong bounds. Cls core level exhibits a line shape attributed to the C-C and C-N bonds. The VB spectroscopy shows dramatic changes related to the interaction of the TiPc2 molecule with the InAs related surface states.

We study the persistence for long times of the solutions of some infinite-dimensional discrete hamiltonian systems with formal hamiltonian Sigma(i=1)(infinity) h(A(i)) + V(phi), (A, phi) is an element of R-N x T-N. V(phi) is not needed small and the problem is perturbative being the kinetic energy unbounded. All the initial data (A(i) (0), phi(i) (0)), i is an element of N in the phase-space R-N x T-N, give rise to solutions with \A(i)(t) - A(i)(0)\ close to zero for exponentially-long times provided that A(i)(0) is large enough for \i\ large. We need partial derivative h/partial derivative A(i) (A(i)(0)) unbounded for i --> +infinity making phi(i) a fast variable; the greater is i, the faster is the angle phi(i) (avoiding the resonances). The estimates are obtained in the spirit of the averaging theory reminding the analytic part of Nekhoroshev-theorem.

We have investigated the temperature effect on Mn dilution into InSb substrates by means of high-resolution core level spectroscopy, surface EXAFS, and by X-ray Magnetic Circular Dichroism (XMCD) using synchrotron radiation. Samples were prepared by manganese deposition of 1, 2, 4 and 8 ML at room temperature (RT) and at 500K on InSb(001) (4 x 2)c(8 x 2) surfaces. By fitting In 4d and Sb 4d core level spectra with Voigt-functions, we identify metallic In and Sb atoms segregated on the surface. EXAFS results show MnSb-like compound formation with hexagonal structure in which Mn atoms replace some antimony atoms in the first nearest neighbours shell.