Interface Transparency of Nb/Pd Layered Systems

We have investigated, in the framework of proximity effect theory, the interface transparency T of superconducting/normal metal layered systems which consist of Nb and high paramagnetic Pd deposited by dc magnetron sputtering. The obtained T value is relatively high, as expected by theoretical arguments. This leads to a large value of the ratio $d_{s}^{cr}/ \xi_{s}$ although Pd does not exhibit any magnetic ordering.Comment: To be published on Eur. Phys. J.

Superconducting nanowire quantum interference device based on Nb ultrathin films deposited on self-assembled porous Si templates

Magnetoresistance oscillations were observed on networks of superconducting ultrathin Nb nanowires presenting evidences of either thermal or quantum activated phase slips. The magnetic transport data, discussed in the framework of different scenarios, reveal that the system behaves coherently in the temperature range where the contribution of the fluctuations is important.Comment: accepted for publication on Nanotechnolog

Nonlinear current-voltage characteristics due to quantum tunneling of phase slips in superconducting Nb nanowire networks

We report on the transport properties of an array of N about 30 interconnected Nb nanowires, grown by sputtering on robust porous Si substrates. The analyzed system exhibits a broad resistive transition in zero magnetic field, H, and highly nonlinear V(I) characteristics as a function of H which can be both consistently described by quantum tunneling of phase slips.Comment: accepted for publication on Appl. Phys. Let

Quantum phase slips in superconducting Nb nanowire networks deposited on self-assembled Si templates

Robust porous silicon substrates were employed for generating interconnected networks of superconducting ultrathin Nb nanowires. Scanning electron microscopy analysis was performed to investigate the morphology of the samples, which constitute of polycrystalline single wires with grain size of about 10 nm. The samples exhibit nonzero resistance over a broad temperature range below the critical temperature, fingerprint of phase slippage processes. The transport data are satisfactory reproduced by models describing both thermal and quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires.Comment: accepted for publication on Applied Physics Letter

High quality MgB2 thin films in-situ grown by dc magnetron sputtering

Thin films of the recently discovered magnesium diboride (MgB2) intermetalic superconducting compound have been grown using a magnetron sputtering deposition technique followed by in-situ annealing at 830 C. High quality films were obtained on both sapphire and MgO substrates. The best films showed maximum Tc = 35 K (onset), a transition width of 0.5 K, a residual resistivity ratio up to 1.6, a low temperature critical current density Jc > 1 MA/cm2 and anisotropic critical field with gamma = 2.5 close to the values obtained for single crystals. The preparation technique can be easily scaled to produce large area in-situ films.Comment: 7 pages, 4 figure

Іон-селективні польові транзистори. Розрахунок порогової напруги

Ion-selective field-effect transistors (ISFET) are being developed and improved to study ion solution composition. It is necessary to determine threshold ISFET voltage on the basis of process data for design and improvement of sensor control circuit. The threshold voltage analytical calculation for p-channel ISFET is presented in this article.Разрабатываются и усовершенствуются сенсоры на основе ион-селективных полевых транзисторов(ИСПТ) для исследования ионного состава растворов. Для проектирования и усовершенствования схем управления сенсорами необходимо определять пороговое напряжение ИСПТ, исходя из данных технологического процесса. В статье приведен аналитический расчет порогового напряжения р-канального ИСПТРозробляються та вдосконалюються сенсори на основі іон-селективних польових транзисторів(ІСПТ) для дослідження іонного складу розчинів. Для проектування та вдосконалення схем управління сенсорами необхідно визначати порогову напругу ІСПТ за даними технологічного процесу. У статті наведено аналітичний розрахунок порогової напруги p-канального ІСПТ

Anisotropic temperature dependent interaction of ferromagnetic nanoparticles embedded inside CNT

We analyze the magnetization versus magnetic field curves of Fe-based nanoparticles embedded inside CNT. Measurements were performed at different temperatures and orientations of the magnetic field. We demonstrate that, for the parallel field the magnetic anisotropy dominates and the coherent anisotropy is of great importance at low temperatures. At high temperatures, the exchange coupling becomes stronger, but the coherent anisotropy still occurs. For the perpendicular field, the coherence anisotropy is absent, and the dimensionality of the system reduces to 2D. The results are discussed in the framework of the correlation functions of the magnetic anisotropy axes

НОВЫЕ ЭЛЕМЕНТЫ СВЕРХПРОВОДНИКОВОЙ ЭЛЕКТРОНИКИ И СПИНТРОНИКИ

The basic results of development and research of new elements of superconducting electronics on the base of porous templates and superconductor - ferromagnet heterostructures are presented shortly. The fundamental aspects of original achievements in the region of the superconducting nanoelectronics, quantum physics interpretation processes in nanoscale self-assembled superconducting nanowires, the coexistence of superconductivity and magnetism are reviewed.Кратко изложены основные результаты разработки и исследования новых элементов сверхпроводниковой электроники на основе пористых подложек и гетероструктур типа сверхпроводник-ферромагнетик. Приведены принципиальные аспекты оригинальных достижений в области сверхпроводниковой наноэлектроники, трактовки физики квантовых процессов в наноразмерных самоформирующихся сверхпроводниковых нанопроводах, сосуществования сверхпроводимости и магнетизма

Superconducting properties of Nb thin films deposited on porous silicon templates

Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering on the porous Si substrates, inherited their structure made of holes of 5 or 10 nm diameter and of 10 to 40 nm spacing, which provide an artificial pinning structure. The superconducting properties were investigated by transport measurements performed in the presence of magnetic field for different film thickness and substrates with different interpore spacing. Perpendicular upper critical fields measurements present peculiar features such as a change in the H_c2(T) curvature and oscillations in the field dependence of the superconducting resistive transition width at H=1 Tesla. This field value is much higher than typical matching fields in perforated superconductors, as a consequence of the small interpore distance.Comment: accepted for publication on Journal of Applied Physic