Nanopattern-stimulated superconductor-insulator transition in thin TiN films

We present the results of the comparative study of the influence of disorder on transport properties in continuous and nanoperforated TiN films. We show that nanopatterning turns a thin TiN film into an array of superconducting weak links and stimulates both, the disorder- and magnetic field-driven superconductor-to-insulator transitions, pushing them to lower degree of disorder. We find that nanopatterning enhances the role of the two-dimensional Coulomb interaction in the system transforming the originally insulating film into a more pronounced insulator. We observe magnetoresistance oscillations reflecting collective behaviour of the multiconnected nanopatterned superconducting film in the wide range of temperatures and uncover the physical mechanism of these oscillations as phase slips in superconducting weak link network.Comment: 6 pages, 4 figure

Performance of nano-structured multilayer PVD coating TiAlN/VN in dry high speed milling of aerospace aluminium 7010-T7651

A low-friction and wear resistant TiAlN/VN multilayer coating with TiAlN/VN bilayer thickness 3 nm has been grown by using the combined cathodic arc etching and unbalanced magnetron sputtering deposition on high speed steel tools for dry cutting of aluminium alloys. In this paper, in-lab and industrial high speed milling tests have been performed on an aerospace aluminium alloy 7010-T7651. The results show that the TiAlN/VN coated tools achieved lower cutting forces, lower metal surface roughness, and significantly longer tool lifetime by three times over the uncoated tools as a result of the low friction and eliminated tool-metal adhesion. Under the same conditions, a TiAlN based multicomponent coating TiAlCrYN also increased the tool lifetime by up to 100% despite the high cutting forces measured

Optical Properties of TiN Thin Films close to the Superconductor-Insulator Transition

We present the intrinsic optical properties over a broad spectral range of TiN thin films deposited on a Si/SiO$_2$ substrate. We analyze the measured reflectivity spectra of the film-substrate multilayer structure within a well-establish procedure based on the Fresnel equation and extract the real part of the optical conductivity of TiN. We identify the metallic contribution as well as the finite energy excitations and disentangle the spectral weight distribution among them. The absorption spectrum of TiN bears some similarities with the electrodynamic response observed in the normal state of the high-temperature superconductors. Particularly, a mid-infrared feature in the optical conductivity is quite reminiscent of a pseudogap-like excitation

Electrochemical behavior of Sn-Zn alloys with different grain structures in chloride-containing solutions

In the present research the electrochemical behavior of the Sn-Zn alloys (Sn-1 wt.%Zn, Sn-4 wt.%Zn and 8.9 wt.%Zn) in 3% NaCl solution is analyzed using potentiodynamic cyclic polarization measurements and Electrochemical Impedance Spectroscopy (EIS) technique. Specimens were longitudinally solidified with simultaneous heat extraction in two opposite directions. Working electrodes were constructed using longitudinal and cross sections of the specimens with both types of structure: columnar and equiaxed. Results obtained from the polarization curves indicated that the two types of grain structures of Sn-Zn alloys (Sn-1 wt.%Zn, Sn-4 wt.%Zn and Sn-8.9 wt.%Zn) corresponding to longitudinal section present a pseudo passive zone. In the case of specimens from cross sections of the samples, the columnar and equiaxed zones of Sn-8.9 wt.%Zn are the only ones that do not have this pseudo passive region. In addition, the interdendritic zone of alloys is susceptible to corrosion by dealloying because this phase is zinc-rich. This type of corrosion also occurs in the zinc rich lamellar structure present in the eutectic. The percentage of zinc in the alloy increases with increasing susceptibility to pitting corrosion. The EIS values obtained revealed that the susceptibility to corrosion increases with increasing zinc content in alloys, for both the columnar and equiaxed zones. In addition, the columnar zones of Sn-4 wt.%Zn and Sn-8.9 wt.%Zn specimens are more resistant to corrosion than the equiaxed grain specimens. However, the equiaxed zone of Sn-1 wt.%Zn alloy is less susceptible to corrosion than the columnar zone. After adjustment by equivalent circuits it is revealed that the equiaxed zone of Sn-8.9 wt.%Zn alloy has a second porous layer composed of corrosion products on the electrode surface.Fil: Mendez, Claudia Marcela. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Scheiber, Verónica L.. Provincia de Misiones. Comité de Desarrollo e Innovación Tecnológica. Centro de Desarrollo e Innovación Tecnológica; ArgentinaFil: Rozicki, Roberto S.. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; ArgentinaFil: Kociubczyk, Alex Iván. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Ares, Alicia Esther. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin

Quantum Metallicity on the High-Field Side of the Superconductor-Insulator Transition

We investigate ultrathin superconducting TiN films, which are very close to the localization threshold. Perpendicular magnetic field drives the films from the superconducting to an insulating state, with very high resistance. Further increase of the magnetic field leads to an exponential decay of the resistance towards a finite value. In the limit of low temperatures, the saturation value can be very accurately extrapolated to the universal quantum resistance h/e^2. Our analysis suggests that at high magnetic fields a new ground state, distinct from the normal metallic state occurring above the superconducting transition temperature, is formed. A comparison with other studies on different materials indicates that the quantum metallic phase following the magnetic-field-induced insulating phase is a generic property of systems close to the disorder-driven superconductor-insulator transition.Comment: 4 pages, 4 figures, published versio

Characterization study of polycrystalline tin oxide surfaces before and after reduction in CO

Polycrystalline tin oxide surfaces have been examined before and after reduction in 40 Torr of CO at 100 and 175 C using Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA), ion scattering spectroscopy (ISS) and electron stimulated desorption (ESD). The changes in the surface composition and chemical states of the surface species generally are subtle for the reductive conditions used. However, significant changes do occur with regard to the amounts and the chemical forms of the hydrogen-containing species remaining after both the 100 and 175 C reductions