A number of new fabrication techniques are developed and optimized in order to fit the requirements of contemporary superconducting electronics. To achieve ultimate performance of integrated submm receivers with operational frequency of 1 THz, tunnel junctions with AlN tunnel barrier having a value as low as 1 m 2 have been developed. High quality characteristics of Nb/AlN/Nb tunnel junctions with = 16 and = 10 m 2 have been demonstrated. Electron Beam Lithography (EBL) in combination with Chemical Mechanical Polishing (CMP) has been incorporated to produce Nb/AlN/Nb junctions with 0.03 m 2 area. A new approach to get overdamped Nb/AlO /Nb tunnel junction has been proposed and realized. The dependencies of the main parameters of novel junctions on the currents density and circuits geometry have been studied. These junctions may have a good potential in Josephson Junction Arrays and Single-Flux-Quantum applications (RSFQ).

Abstract. -The superconducting current-phase relation (CPR) of Nb/Au/(001)YBa2Cu3Ox heterojunctions prepared on epitaxial c-axis oriented YBa2Cu3Ox thin films has been measured in a single-junction interferometer. For the first time, the second harmonic of the CPR of such junctions has been observed. The appearance of the second harmonic and the relative sign of the first and second harmonics of the CPR can be explained assuming, that the macroscopic pairing symmetry of our YBa2Cu3Ox thin films is of the d + s type.Introduction. It is now well established that the dominant component of the superconducting order parameter in the cuprates has d-wave symmetry (see [1] and references therein). Moreover, it has become clear that in orthorhombic materials such as YBa 2 Cu 3 O x (YBCO), a finite component with s-wave symmetry is admixed to the dominant d-wave order parameter. The early in-plane phase sensitive experiments imply that the d-wave component remains coherent through the whole sample [1], while an elegant c-axis tunneling experiment shows directly that the s-wave order parameter component does change sign across the twin boundary [2].The above picture of the YBCO pairing state is challenged by the experimental observation of a finite c-axis Josephson current between heavily twinned YBCO and a Pb counterelectrode [3]. Namely, the contribution of the s-wave part of the YBCO order parameter to

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DC heating effects in superconductor–insulator–superconductor (SIS) tunnel junctions are studied by comparing junctions sandwiched between niobium or aluminum layers. With niobium a temperature rise of several Kelvin is observed, which is reduced by an order of magnitude by using aluminum. A simple model satisfactorily explains this observation and predicts a 30% increase in the subgap current due to the elevated temperature. At the operating voltage for heterodyne mixing the receiver noise temperature increases by only 2%.

This paper presents a new type of 3-dB power divider that achieves wide-band, low-loss, and symmetric power division. In the paper, we discuss the design considerations and present results of measurements at 10 and 100 GHz. The power divider symmetry is examined as a function of the termination loads mismatch. The simplicity of the presented divider makes it very suitable for application at millimeter and submillimeter bands. The predicted and the measured performance are in very good agreement.Index Terms-Millimeter-wave, power divider, side band separation receiver, waveguide-to-microstrip transition.