Igor M. Dmitrenko

Spatially resolved characterization of superconducting films and cryoelectronic devices by means of low temperature scanning laser microscope

Abstract The work describes the low temperature scanning laser microscopy technique used for spatially resolved characterization of superconducting films and film-based cryoelectronic circuits in the temperature range from 2 to 300 K. The determination of superconducting parameters for separate elements of a high T c Josephson junctions array and imaging of the resistive transition in a high T c superconducting polycrystalline film are demonstrated. The spatial evolution of the resistive state of a Sn thin film strip associated with the phase slip lines formation is visualized.

Laser scanning visualization of evolution of vortex instability in current-carrying superconducting strips

The low temperature scanning laser microscopy is used to study spatial characteristics of current-induced resistive states in wide superconducting Sn films. The irregularities of edge potential barrier and the current distribution in a film cross section are visualized. The results are in good qualitative agreement with Aslamazov-Lempitsky theory.

A low temperature system with a pulse UV laser for scribing HTSC films and single crystals

Abstract A simple laser scribing equipment used to pattern high-Tc films and single crystals within a micron accuracy is described. A focused beam of a UV pulsed laser serves as a cutting tool. A low temperature attachment enables all operations to be performed at sample temperatures ranging from 65 to 300 K. Thus it provides a means to fit the critical current of any element in a cryoelectronic circuit to a desirable value during its operational conditions.

Superconducting and normal properties of the set of Mo/Si superlattices with variable Si layer thickness

We report the results of the superconducting and kinetic parameter measurements (transition temperature Tc, parallel and perpendicular critical fields Hc2, resistivity in the normal state) on a set of Mo/Si superconducting superlattices with a constant metal layer thickness dMo=22 A and variable semiconducting one dSi(14–44 A). Our data show a monotonic dependence of all measured parameters on dSi. It is found that the Josephson interlayer coupling energy depends exponentially on the spacer thickness. The data obtained allowed us to determine the characteristic electron tunneling length for amorphous silicon with high precision. It is equal to 3.9 A. Enhancement of interlayer coupling leads to the Mo. Si multilayer transition temperature increasing, in agreement with Horovitz theory and with the experimental data on high-Tc materials.

Spatially resolved study of transition to the phase-slip lines resistive state in wide superconducting strips

The voltage images of nonequilibrium resistive state associated with a phase-slip lines (PSLs) formation in a current-carrying superconducting Sn strip were obtained using low-temperature scanning laser microscopy (LTSLM). The transition to the PSLs started from dynamic-mixed state by single PSL nucleation. The number of PSLs increases rapidly while increasing the current density, the spatial rearrangement of the whole resistive structure being observed.

Direct measurement of critical currents of individual weak links in DC interferometerby scanning laser microscope

Abstract This paper describes the non-destructive technique of in situ measurement of critical currents Ic of individual weak links in thin film superconducting quantum do interferometers (dc SQUDs). The low temperature scanning laser microscope (LTLSM) is used to study the SQUID resistive response to the laser radiation and to measure the critical currents I c1 and I c2 of the weak links separately.

Experimental studies of weakly coupled superconductors (Review)

A review is given of the main experimental results obtained in research on weakly coupled superconductors after 1964 at the Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Kharkov (ILTPE).

Phase transition in the electron subsystem of high-Tc YBa2Cu3O7

Time-dependent XRD and resistivity data on the orthorhombic high-Tc (Tc≥90K) YBa2Cu3O7 (123) phase at the low temperature transformation YBa2Cu3O7→YBa2Cu4O8 (124) are presented. This transformation is accompanied by the phase separation of mother’s 123 structure into two 123 structures. We analyse the difference in the tructures and the electrophysical features of these two phases and reveal that two qualitatively different HTS states of the electron subsystem may exist in the orthorhombic 123 structure as function of the type and a degree of its cation subsystem imperfection.

Low temperature scanning laser microscope for studies in high magnetic fields

The low temperature scanning laser microscope (LTSLM) for investigation of thin film superconducting objects in the temperature range of 2.5–300 K and magnetic field up to 5 T is described.