S.H. Moon

High critical current densities in superconducting MgB2 thin films

Superconducting MgB2 thin films were prepared on Al2O3(0001) and MgO(100) substrates. Boron thin films were deposited by the electron-beam evaporation followed by postannealing process with magnesium. Proper postannealing conditions were investigated to grow good superconducting MgB2 thin films. The x-ray diffraction patterns showed randomly oriented growth of MgB2 phase in our thin films. The surface morphology was examined by scanning electron microscope and atomic force microscope. Critical current density (JC) measured by transport method was about 107 A/cm2 at 15 K, and superconducting transition temperature (TC) was ∼39 K in the MgB2 thin films on Al2O3.

Realization and properties of YBa2Cu3O7−δ Josephson junctions by metal masked ion damage technique

We have developed a simple process to fabricate high-TC Josephson junctions by a combination of focused ion beam milling and 100 keV H2+ ion implantation. The resistively shunted junction-like current–voltage characteristics were observed in the temperature range of 48 to 4.2 K. The devices showed clear dc and ac Josephson effects. This technique is very promising in terms of simplicity and flexibility of fabrication and has potential for high-density integration.

YBa2Cu3O7−δ/NdBa2Cu3O7−δ/YBa2Cu3O7−δ edge junctions and SQUIDS

YBa2Cu3O7−δ (YBCO) Josephson junctions in a ramp edge geometry with NdBa2Cu3O7−δ (NBCO) barriers were fabricated by pulsed laser deposition on (100) SrTiO3 substrates. The barrier layer thicknesses were d=100, 200, and 300 A . The I–V characteristics of YBCO/NBCO/YBCO junctions changed from the resistively shunted junction type to flux‐creeplike behavior as temperature decreased. Shapiro steps due to the ac Josephson effect clearly developed under microwave irradiation. The interface between the superconducting (YBCO) and the normal layer (NBCO) turned out to be fairly clean with small interface resistance. The mean value of the measured IcRn product for junctions with 100‐A‐thick barriers was 71±34 μV at 77 K. The normal coherence length of the NBCO barrier material was ∼40 A. The SQUIDs, made of superconductor–normal metal–superconductor junctions, showed voltage modulation at 77 K.

A compact two-pole X-band high-temperature superconducting microstrip filter

In this paper we examine a microstrip line filter with three gaps separated by approximately a quarter wavelength. Two filters, one with gold and the other with YBCO were fabricated. The thickness of top conducting microstrips was 600 nm. The ground plane under the 0.5 mm-thick lanthanum aluminate (LaAlO/sub 3/) substrate was implemented with a 2 micron-thick gold layer for both filters. These filters showed similar frequency responses with 5% 3-dB bandwidth. The insertion loss, however, improved from 2.8 dB to 1.5 dB by using the superconductor. The performance of the filter was also tested by employing the three dimensional microwave FEM software, and the simulation result compared well with the measured data.<<ETX>>

Josephson effects in MgB/sub 2/ metal masked ion damage junctions

Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufacturable SNS type Josephson junctions in 100 nm thick MgB

MgB2 junctions and SQUIDs fabricated by focused ion beam

_{2}

Microwave and structural properties of large YBa2Cu3O7-δ films: a study on the homogeneity

with T

Interface-modified YBCO ramp-edge Josephson junctions by deionized water

_{C}

Double-sided YBa2Cu3O7-δ thin films made by off-axis pulsed laser deposition

of 38 K. The junctions show non-hysteretic current - voltage characteristics between 36 and 4.2 K. Experimental evidence for the dc and ac Josephson effects in MgB

Effect of ion beam damage and heat treatment on interface-modified junctions

_{2}