High Temperature Growth of Graphene from Cobalt Volume: Effect on Structural Properties

Several transition metals other than the largely used Cu and Ni can be, in principle, employed to catalyze carbon precursors for the chemical vapor deposition of graphene, because the thermodynamics of their alloying with carbon is well known. For example, the wealth of information in the Co-C phase diagram can be used to predict the properties of graphene grown in this way. It is, in fact, expected that growth occurs at a temperature higher than in Ni, with beneficial consequences to the mechanical and electronic properties of the final product. In this work, the growth of graphene onto Co film is presented together with an extensive Raman characterization of the structural properties of the material so far obtained. Previous results reporting the full coverage with negligible defective areas, in spite of discontinuities in the underlying metal, are confirmed, together with the occurrence of strain in the graphene sheet. Strain is deeply investigated in this work, in view of possible employment in engineering the material properties. The observed strain is ascribed to the high thermal mismatch with the substrate, even if an effect of the crystallographic transition of Co cannot be excluded

Growth of room temperature ferromagnetic Ge1-xMnx quantum dots on hydrogen passivated Si (100) surfaces

A method for the synthesis of room-temperature ferromagnetic dilute semiconductor Ge1-xMnx (5 % < x < 8 %) quantum dots by molecular beam epitaxy by selective growth on hydrogen terminated silicon (100) surface is presented. The functionalized substrates, as well as the nanostructures, were characterized in situ by reflection high-energy electron diffraction. The quantum dots density and equivalent radius were extracted from field emission scanning electron microscope pictures, obtained ex-situ. Magnetic characterizations were performed by superconducting quantum interference device vibrating sample magnetometry revealing that ferromagnetic order is maintained up to room temperature: two different ferromagnetic phases were identified by the analysis of the field cooled – zero field cooled measurements

A Genotypic-oriented View of CFTR Genetics Highlights Specific Mutational Patterns Underlying Clinical Macro-categories of Cystic Fibrosis.

Cystic Fibrosis (CF) is a monogenic disease caused by mutations of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. The genotype-phenotype relationship in this disease is still unclear, and diagnostic, prognostic and therapeutic challenges persist. We enrolled 610 patients with different forms of CF and studied them from a clinical, biochemical, microbiological and genetic point of view. Overall, 125 different mutated alleles (11 of which with novel mutations and 10 of which complex) and 225 genotypes were found. A strong correlation between mutational patterns at the genotypic level and phenotypic macro-categories emerged. This specificity appears to be largely dependent on rare and individual mutations, as well as on the varying prevalence of common alleles in different clinical macro-categories. However, 19 genotypes appeared to underlie different clinical forms of the disease. The dissection of the pathway from the CFTR mutated genotype to the clinical phenotype allowed to identify at least two components of the variability usually found in the genotype - phenotype relationship. One component seems to depend on the genetic variation of CFTR, the other component on the cumulative effect of variations in other genes and cellular pathways independent from CFTR. The experimental dissection of the overall biological CFTR pathway appears to be a powerful approach for a better comprehension of the genotype - phenotype relationship. However, a change from an allele-oriented to a genotypic-oriented view of CFTR genetics is mandatory, as well as a better assessment of sources of variability within the CFTR pathway

Electrical stimulation of non-classical photon emission from diamond color centers by means of sub-superficial graphitic electrodes

Focused MeV ion beams with micrometric resolution are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as already demonstrated for different device applications. In this work we apply this fabrication method to the electrical excitation of color centers in diamond, demonstrating the potential of electrical stimulation in diamond-based single-photon sources. Differently from optically-stimulated light emission from color centers in diamond, electroluminescence (EL) requires a high current flowing in the diamond subgap states between the electrodes. With this purpose, buried graphitic electrode pairs, 10 μm spaced, were fabricated in the bulk of a single-crystal diamond sample using a 6 MeV C microbeam. The electrical characterization of the structure showed a significant current injection above an effective voltage threshold of 150 V, which enabled the stimulation of a stable EL emission. The EL imaging allowed to identify the electroluminescent regions and the residual vacancy distribution associated with the fabrication technique. Measurements evidenced isolated electroluminescent spots where non-classical light emission in the 560-700 nm spectral range was observed. The spectral and auto-correlation features of the EL emission were investigated to qualify the non-classical properties of the color centers