We present a new technique to measure the complex surface impedance of the mixed state of superconducting thin films over the broad frequency range 45 MHz-20 GHz. The surface impedance is extracted from measurements of the complex reflection coefficient made on the film using a vector network analyzer. The technique takes advantage of a special geometry in which the self-fields from currents fl...

Superconducting thin films have the potential to overcome fundamental limitations of bulk niobium technology that is currently implemented in linear particle accelerators. Before these thin films can successfully be implemented, systematic studies on structureproperty correlations are necessary. Here, we present the characterization of niobium nitride thin films and multilayers. We explore the ...

We studied the changes in the superconducting properties of Nb films due to an array of Ni dots used as collective pinning sites. To determine the pinning mechanism, thin Ag layers of varying thicknesses were deposited on the Ni dots prior to the Nb film deposition. The Ag deposited on the pinning dots has little effect on the collective pinning phenomena, which implies that the main pinning me...

We have measured the maximum field for which vortices are completely expelled from a thin-film superconducting strip. Niobium strips of width W were field cooled and imaged with a scanning Hall-probe microscope. Below a critical field B(m) approximately Phi(0)/W(2) all flux was expelled; above this field vortices were observed with a density increasing approximately linearly with field. The sma...

We report measurements of bolometric absorption and absolute reflectivity of a thin film of NbN on a silicon substrate, above and below the superconducting transition temperature of 13.3 K. The opening of the gap at an energy of 3.9 kB Tc is seen clearly in both types of measurement. The data are compared with the predictions of the Mattis-Bardeen theory. The change in the reflectivity and the ...

We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350 mK and in magnetic fields up to 9 T, with thin film deposition and in situ single crystal cleaving capabilities. The main focus lies on the simple design of STM head and a sample holder design that allows us to get spectroscopic data on superconducting thin films...

We have made an experimental study of the tunneling density of states (DOS) in strong ferromagnetic thin films (CoFe) in proximity with a thick superconducting film (Nb) as a function of dF , the ferromagnetic thickness. Remarkably, we find that as dF increases, the superconducting DOS exhibits a scaling behavior in which the deviations from the normal-state conductance have a universal shape t...

The dc Josephson effect refers to the dissipationless electrical current – the supercurrent – that can be sustained across a weak link connecting two bulk superconductors.1 This effect is a probe of the fundamental nature of the superconducting state, which depends crucially on the spatial dimensionality of the superconducting electrodes. For bulk (i.e. threedimensional) superconductors, the su...

Morphology and physical properties of mono(YBa2Cu3O7) and multilayered (YBa2Cu3O7/SmBa2Cu3O7/ YBa2Cu3O7) superconducting thin films with thickness ranging from 90 nm to 28 nm have been investigated. For both types of samples, the superconducting properties degraded with reduction of film thickness. Structural and electromagnetic properties were visualized through scanning electron microscopy an...