High efficiency and negligible dark-count rates of transition-edge sensor\ud (TES) microcalorimeters as single photon detector at telecommunications and optical\ud visible wavelengths make them powerful tools for quantum information and quantum computation. In this work we report details on the fabrication of Au/Ti for\ud photon counting and analyse the effects on the critical temperature and the transition\ud steepness of the structuring process and wiring material. Au/Ti films deposited by electron-beam at substrate temperature lower than 435 K show sharp transition and reproducible Tc. Moreover, we observe that TES with Al wiring are more stable\ud and have better characteristics of TES with Nb wiring. Using 20 micron×20 micron Ti/Au TES single photon detection has been obtained in the UV-visible range

Monodisperse silica nanospheres with sizes ranging from 250 to 725 nm were prepared and assembled into monolayers to produce regularly distributed light hot spots at the surface of oxidized silicon substrates when illuminated by a laser. Single UV nanosecond laser pulses were employed with energies above the local ablation threshold for the silicon dioxide layer, resulting in the direct formation of 2D periodically porous membranes on top of the silicon. The periodicity of the array was driven by the size of the self-assembled nanospheres. While the local field enhancement was strongly dependent on the sphere size due to Mie resonances, the size and morphology of the produced features could be maintained for all tested situations by balancing the change in local fields with the laser pulse energy. This work demonstrates the fabrication of 90 nm thick porous membranes with pore size of about 100 nm and periodicity ranging from 250 to 725 nm.

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Overdamped Josephson junctions based on a Nb/Al-AlOx/Nb superconductor-normal metal-insulator-superconductor structure were realized at the submicrometer scale by using focused ion beam nano-sculpting technique. This approach represents an alternative solution to the classical electron beam lithography and allows for an accurate control of the junction dimensions. Superconductor-normal metal-insulator-superconductor structured junctions were downscaled to about 300 x 300 nm(2) and electrically measured at 4.2 K. The simple fabrication process, leading to high current density, J(c), and characteristic voltage, V-c, values and good uniformity, makes these junctions promising as elementary cell in complex circuits for rapid single flux quantum and ac voltage standard applications

Cryogen-free operation of is essential to spread applications of superconductivity and is indeed unavoidable in some cases. In electrical metrology applications, higher temperature operation to reduce the refrigerator size and complexity is not yet possible, since arrays of Josephson junctions for voltage standard applications made with high-temperature superconductors are not yet available. The superconductor-normal metal-insulator-superconductor (SNIS) technology developed at INRIM uses low temperature superconductors, but allows operation well above liquid helium temperature. It is thus interesting for application to a compact cryocooled standard. We studied SNIS devices cooled with a closed-cycle refrigerator, both in DC and under RF irradiation. Issues related to thermal design of the apparatus are analyzed. The dependence of RF steps on the number of junctions observed is discussed in detail and interpreted as a consequence of power dissipated inside the chip