R. Gunnella

Phase separation and dilution in implanted MnxGe1-x alloys

The structural and electronic properties of MnxGe1−x alloys (x⩽0.15) fabricated by ion implantation are investigated by means of x-ray diffraction and synchrotron radiation photoemission spectroscopy. The diffraction patterns point to the presence of ferromagnetic Mn5Ge3 nanoparticles; however, valence band spectra, interpreted by means of accurate ab initio calculations including Hubbard-like correlations, show clear fingerprints of an effective substitutional Mn dilution in the Ge semiconducting host.

Structural, electrical, electronic and optical properties of melanin films

We present thick, uniform and rather flat melanin films obtained using spray deposition. The morphology of the films was investigated using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Temperature-dependent electrical resistance of melanin thin films evidenced a semiconductor-like character and a hysteretic behavior linked to an irreversible process of water molecule desorption from the melanin film. X-ray Photoelectron Spectroscopy (XPS) was carried out to analyze the role of the functional groups in the primary and secondary structure of the macromolecule, showing that the contribution of the 5,6-dihydroxyindole-2-carboxylic acid (DHICA) subunit to the molecule is about 35%. Comparison of the optical absorption of the thick (800nm) and thin (80nm) films showed a spectral change when the thickness increases. From in vacuum photoconductivity (PC) measured at controlled temperatures, we suggest that the melanin films exhibit a possible charge transport mechanism by means of delocalized

Direct structural evidences of Mn dilution in Ge

\pi

EIS: the scattering beamline at FERMI

states along the stacked planar secondary structure.

MSPHD: A full multiple scattering code for low energy photoelectron diffraction

X-ray diffraction, transmission electron microscopy, extended x-ray absorption fine structure spectroscopy, and x-ray photoemission spectroscopy have been used to study the structural properties of MnxGe1−x ion implanted alloys (x≃0.04) at 240 and 270°C substrate temperatures. Between 40% and 50% of the Mn atoms are found to occupy substitutional sites. No interstitial Mn atoms are found. The Mn–Ge coordination distance is 2.50(2)A. Moreover, in the subsurface implanted layer [up to 32(2)nm depth] all the Mn atoms are effectively diluted in the Ge matrix, reaching a peak doping concentration of 7±1%.

Variability of physical characteristics of electro-sprayed poly(3-hexylthiophene) thin films

The Elastic and Inelastic Scattering (EIS) beamline at the free-electron laser FERMI is presented. It consists of two separate end-stations: EIS-TIMEX, dedicated to ultrafast time-resolved studies of matter under extreme and metastable conditions, and EIS-TIMER, dedicated to time-resolved spectroscopy of mesoscopic dynamics in condensed matter. The scientific objectives are discussed and the instrument layout illustrated, together with the results from first exemplifying experiments.

Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water.

We describe a Full Multiple Scattering (MS) code for the calculation of photoelectron diffraction (PD) patterns from solid surfaces. The use of a complex potential allows the calculation of complex phase shifts which describe realistically the damping of the electronic wave during its path to the detector. Full convergence in the scattering path expansion due to the inversion of the multiple scattering matrix makes this method particularly reliable in the surface sensitive energy range of the photoelectron, where approximate solutions in terms of series expansion and/or real potential calculations lead to inaccuracies in the determination of structural parameters. In this form the code is suitable to applications to clean surfaces such as Surface Core Level Shift Photoelectron Diffraction (SCLS-PD).

Rubbing effects on the structural and optical properties of poly(3­hexylthiophene) films

Structural and electronic properties of homogeneous poly(3-hexylthiophene) (P3HT) films obtained from the electro-spray method were presented by means of grazing incidence x-ray diffraction, atomic force microscopy, optical absorption, photoelectron spectroscopy, and (photo)electrical conductivity. Starting from different solution concentrations and flow rate conditions, differently assembled thin films were obtained whose physical properties were peculiarly different from those ones obtained by other deposition methods. If properly refined, the method could in principle broaden the spectrum of the existing nano and microscale structures of the P3HT thin films. V C 2011 American Institute of Physics. [doi:10.1063/1.3633519]

Growth and magnetic properties of MnGe films for spintronic application.

The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation.

Angular dependence of the EXFAS (extended fine Auger structure) in MgO(100) surfaces: short-range order versus diffraction effects

Steady state photoconductivity and x-ray diffraction combined with optical and electronic spectroscopies were applied to study spin coated poly(3-hexylthiophene) (P3HT) films mechanically rubbed using a teflon bar. As expected, photoconductivity evidenced a strong increase in the photo-response along the rubbing direction. But, while rubbing during annealing at a temperature of 70 °C resulted in a sizeable photocurrent anisotropy along the direction parallel or perpendicular to the rubbing, the samples rubbed at room temperature (RT) showed an isotropic and comparatively stronger enhancement of absorption and photoconductivity spectral features. According to these observations, rubbing at RT resulted in a significant increase in local order and macroscopic alignment of the film, while a higher degree of global order but with a relaxed local structure was obtained after rubbing at 70 °C.