Evidence for Single-gap Superconductivity in Mg(B_{1-x}C_x)_2 Single Crystals with x=0.132 from Point-Contact Spectroscopy

We report the results of the first directional point-contact measurements in Mg(B_{1-x}C_{x})_2 single crystals with 0.047 <= x <= 0.132. The two-gap superconductivity typical of MgB_2 persists up to x=0.105. In this region, the values of the gaps Delta_{sigma} and Delta_{pi} were determined by fitting the Andreev-reflection conductance curves with a two-band Blonder-Tinkham-Klapwijk (BTK) model, and confirmed by the single-band BTK fit of the sigma- and pi-band conductances, separated by means of a magnetic field. At x=0.132, when T_{c}=19 K, we clearly observed for the first time the merging of the two gaps into one of amplitude Delta~3 meV.Comment: 5 pages, 5 figures. One figure and one panel added; text and discussion update

Point-Contact Spectroscopy in MgB_2: from Fundamental Physics to Thin-Film Characterization

In this paper we highlight the advantages of using point-contact spectroscopy (PCS) in multigap superconductors like MgB_2, both as a fundamental research tool and as a non-destructive diagnostic technique for the optimization of thin-film characteristics. We first present some results of crucial fundamental interest obtained by directional PCS in MgB_2 single crystals, for example the temperature dependence of the gaps and of the critical fields and the effect of a magnetic field on the gap amplitudes. Then, we show how PCS can provide useful information about the surface properties of MgB_2 thin films (e.g. Tc, gap amplitude(s), clean or dirty-limit conditions) in view of their optimization for the fabrication of tunnel and Josephson junctions for applications in superconducting electronics.Comment: 11 pages, 7 figures; Proceedings of 6th EUCAS Conference (14-18 September 2003, Sorrento - Italy

Evidence for Single-gap Superconductivity in Mg(B1-xCx)2 Single Crystals with x=0.132 from Point-Contact Spectroscopy

We report the results of the first directional point-contact measurements in MgsB1−xCxd2 single crystals with 0.047<x<0.132. The two-gap superconductivity typical of MgB2 persists up to x=0.105. In this region, the values of the gaps Ds and Dp were determined by fitting the Andreev-reflection conductance curves with a two-band Blonder-Tinkham-Klapwijk sBTKd model, and confirmed by the single-band BTK fit of the s- and p-band conductances, separated by means of a magnetic field. At x=0.132, when Tc=19 K, we clearly observed the merging of the two gaps into one of amplitude D=3 meV

Meso-ALPO prepared by thermal decomposition of the organic-inorganic composite: A FTIR study

Mesoporous ALPO was synthesised using cetyltrimethylammonium bromide (CTAB) as a structure-directing agent. FTIR spectroscopy was used to follow the formation of the ALPO mesophase by thermal decomposition of the aluminophosphate/surfactant composite and NH3 was used as probe molecule to monitor the surface acidity of the product

Meso-alpo Prepared By Thermal Decomposition Of The Organic-inorganic Composite: A Ftir Study

Mesporous ALPO was synthesised using cetyltrimethylammonium bromide (CTAB) as a structure-directing agent. FTIR spectroscopy was used to follow the formation of the ALPO mesophase by thermal decomposition of the aluminophosphate/surfactant composite and NH3 was used as probe molecule to monitor the surface acidity of the product.141417422Estermann, M., McCuster, L.B., Baerlocher, C., Merrouche, A., Kessler, H., (1991) Nature, 352, p. 320Davis, M.E., Saldarriaga, C., Montes, C., Garces, J., Crowder, C., (1998) Nature, 331, p. 698Kimura, T., Sugahara, Y., Kuroda, K., (1998) Micropor. Mesopor. Mater., 22, p. 115Masson, N.C., Pastore, H.O., (2001) Micropor. Mesopor. Mater., 44, p. 173Oliveira, E.C., Masson, N.C., Mascarenhas, A.J.S., Pastore, H.O., Colloids and SurfacesPeña, M.L., Dellarocca, V., Rey, F., Corma, A., Coluccia, S., Marchese, L., (2001) Microporous Mesoporous Mat., 44-45, p. 345Marchese, L., Gianotti, E., Maschmeyer, T., Martra, G., Coluccia, S., Thomas, J.M., (1997) Il Nuovo Cimento, 19 D, p. 1707Gianotti, E., Dellarocca, V., Martra, G., Marchese, L., Coluccia, S., Maschmeyer, T., in preparatio