title: Anodization-based process for the fabrication of all niobium nitride Josephson junction structures.
abstract: We studied the growth and oxidation of niobium nitride (NbN) films that we used to fabricate superconductive tunnel junctions. The thin films were deposited by dc reactive magnetron sputtering using a mixture of argon and nitrogen. The process parameters were optimized by monitoring the plasma with an optical spectroscopy technique. This technique allowed us to obtain NbN as well as good quality AlN films and both were used to obtain NbN/AlN/NbN trilayers. Lift-off lithography and selective anodization of the NbN films were used, respectively, to define the main trilayer geometry and/or to separate electrically, different areas of the trilayers. The anodized films were characterized by using Auger spectroscopy to analyze compounds formed on the surface and by means of a nano-indenter in order to investigate its mechanical and adhesion properties. The transport properties of NbN/AlN/NbN Josephson junctions obtained as a result of the above described fabrication process were measured in liquid helium at 4.2 K.
authors.affiliation: Dipartimento di Fisica and MINAS Lab, Università di Roma Tor Vergata, 00133 Roma, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Lucci
authors.affiliation: Dipartimento di Fisica and MINAS Lab, Università di Roma Tor Vergata, 00133 Roma, Italy.
authors.forename: Ivano
authors.initials: I
authors.lastname: Ottaviani
authors.affiliation: Dipartimento di Fisica and MINAS Lab, Università di Roma Tor Vergata, 00133 Roma, Italy; CNR-SPIN Institute, Via Giovanni Paolo II, 84084 Fisciano (SA), Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Cirillo
authors.affiliation: Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata", Via del Politecnico, 00133 Roma, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: De Matteis
authors.affiliation: Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata", Via del Politecnico, 00133 Roma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Francini
authors.affiliation: Dipartimento di Fisica and MINAS Lab, Università di Roma Tor Vergata, 00133 Roma, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Merlo
authors.affiliation: Dipartimento di Fisica and MINAS Lab, Università di Roma Tor Vergata, 00133 Roma, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Davoli
keywords: Josephson effect; superconductors; thin films; tunneling