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1

Easy Vortex Motion in an Artificial Channel of YBa_2Cu_3O_{7-δ} Superconducting Films

100%

Jukna A., Barboy I., Jung G., Abrutis A., Li X., Wang D., Sobolewski R.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

959-962

EN

Quasi-Josephson effect produced by a coherent vortex motion in the horizontal part of the laser-performedΠ-shaped channel of a YBa_2Cu_3O_{7-δ} superconducting bridge was investigated by means of electric transport measurements. We observed that in our structures, in a limited range of temperatures and bias currents, the vortices were confined in the channel only and moved coherently with the velocity of 3×10^4 m/s. The corresponding current-voltage characteristics of the bridge exhibited Josephson-like voltage steps with the amplitude dependent on temperature, but independent of the bias current.

2

Investigation Details of Vortex Density in Laser-Written Π-Shaped Channel of YBCO Bridge by Means of I-V Dependences

84%

Steponaviciene L., Sulcas J., Jukna A., Jung G., Plausinaitiene V., Abrutis A., Maneikis A., Gong M., Sobolewski R.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

180-182

EN

A current-self-induced magnetic field H_{j}, such that H_{c1} < H_{j} < H_{c2} at T < T_{c}, penetrates a thin-film, type-II superconductor forming the Abrikosov magnetic vortex-antivortex pairs in the film's areas of weakest superconductivity. Our atomic force microscopy and scanning tunneling microscopy images confirm that in 50 μm wide, 100 μm long and 0.3 μm thick YBa_2Cu_3O_{7 - x} superconducting devices magnetic flux penetrates first into a 5 μm wide, Π-shaped and partially deoxygenated (x ≈ 0.2) channel for easy vortex motion. When the Lorentz force overcomes pinning force in the channel, the flux starts to move and its drift dissipates energy inducing dc voltage. This work reports on the density of coherently moving vortices along the channel vs. temperature in range from 0.93T_{c} to 0.97T_{c}. Our simulations show that the vortex density vs. temperature dependence extracted from I-V measurements of our devices follows the temperature dependence of magnetic field penetration depth and the coherence length of the superconductor.

3

Current Distribution in Y-Ba-Cu-O Superconducting Microbridges Containing Π-Shaped Channel for Easy Vortex Motion

84%

Sulcas J., Steponaviciene L., Jukna A., Jung G., Plausinaitiene V., Abrutis A., Gong M., Sobolewski R.

Acta Physica Polonica A

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2011

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vol. 119

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issue 2

183-185

EN

A mixed state in dc-biased thin films of II-type superconductors realizes the Abrikosov magnetic vortices/antivortices, which are the result of the current-self magnetic field penetration into the film at temperatures lower than its critical temperature T_{c}. A nucleation of vortices/antivortices at the superconducting film's edges, their motion perpendicular to the direction of biasing current, and the annihilation in the film's center originates from a current dissipation in the superconductor and expresses itself in experiments as a dc voltage. This work reports on the results of simulation of current density in a 50 μm wide, 100 μm long, and 0.3 μm thick YBa_2Cu_3O_{7 - x} microbridges containing Π-shaped 5 μm wide single channel of easy vortex motion fabricated by means of laser-writing technique. Analyzing a two-dimensional-net of resistors and assuming that, due to the Meissner-Ochsenfeld effect, the magnetic flux penetration into superconducting film is nonlinear, we demonstrate that presence of a Π-shaped channel causes a non-homogeneous distribution of current in the microbridge.

4

Ultrafast Phenomena in Freestanding LT-GaAs Devices

68%

Marso M., Mikulics M., Adam R., Wu S., Zheng X., Camara I., Siebe F., Förster A., Güsten R., Kordoš P., Sobolewski R.

Acta Physica Polonica A

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2005

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vol. 107

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issue 1

109-117

EN

We report on the fabrication and high-frequency performance of our photodetectors and photomixers based on freestanding low-temperature-grown GaAs. The MBE-grown low-temperature GaAs layers are lifted from the native GaAs substrate and transferred on top of variety of host substrates. The freestanding devices exhibit breakdown electrical fields above 200 kV/cm and dark currents below 3×10^{-7} A at 100 V bias. Device photoresponse shows 0.55 ps wide electrical transients with voltage amplitudes up to 1.3 V, measured using an electro-optical sampling technique with 100 fs wide laser pulses. Photomixing experiments at 460 GHz yield a 9 times higher output power for the freestanding device on Si/SiO_2 host substrate compared to the native substrate.

5

Ultrathin NbN Films for Superconducting Single-Photon Detectors

68%

Słysz W., Guziewicz M., Borysiewicz M., Domagała J., Pasternak I., Hejduk K., Rzodkiewicz W., Ratajczak J., Bar J., Węgrzecki M., Grabiec P., Grodecki R., Węgrzecka I., Sobolewski R.

Acta Physica Polonica A

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2011

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vol. 120

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issue 1

200-203

EN

We present our research on fabrication and structural and transport characterization of ultrathin superconducting NbN layers deposited on both single-crystal Al_2O_3 and Si wafers, and SiO_2 and Si_3N_4 buffer layers grown directly on Si wafers. The thicknesses of our films varied from 6 nm to 50 nm and they were grown using reactive RF magnetron sputtering on substrates maintained at the temperature 850°C. We have performed extensive morphology characterization of our films using the X-ray diffraction method and atomic force microscopy, and related the results to the type of the substrate used for the film deposition. Our transport measurements showed that even the thinnest, 6 nm thick NbN films had the superconducting critical temperature of 10-12 K, which was increased to 14 K for thicker films.

6

Technology of Ultrathin NbN and NbTiN Films for Superconducting Photodetectors

68%

Guziewicz M., Slysz W., Borysiewicz M., Kruszka R., Sidor Z., Juchniewicz M., Golaszewska K., Domagala J., Rzodkiewicz W., Ratajczak J., Bar J., Wegrzecki M., Sobolewski R.

Acta Physica Polonica A

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2011

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vol. 120

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issue 6A

A-76-A-79

EN

We report fabrication and characterization of ultrathin NbN and NbTiN films designed for superconducting photodetectors. Our NbN and NbTiN films were deposited on Al_2O_3 and Si single-crystal wafers by a high-temperature, reactive magnetron sputtering method and, subsequently, annealed at 1000°C. The best, 18 nm thick NbN films deposited on sapphire exhibited the critical temperature of 15.0 K and the critical current density as high as ≈ 8 × 10^6 A/cm^2 at 4.8 K.

7

Dynamics of Hotspot Formation in Nanostructured Superconducting Stripes Excited with Single Photons

68%

Jukna A., Kitaygorsky J., Pan D., Cross A., Perlman A., Komissarov I., Sobolewski R., Okunev O., Smirnov K., Korneev A., Chulkova G., Milostnaya I., Voronov B., Gol'tsman G.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

955-958

EN

Dynamics of a resistive hotspot formation by near-infrared-wavelength single photons in nanowire-type superconducting NbN stripes was investigated. Numerical simulations of ultrafast thermalization of photon-excited nonequilibrium quasiparticles, their multiplication and out-diffusion from a site of the photon absorption demonstrate that 1.55 μm wavelength photons create in an ultrathin, two-dimensional superconducting film a resistive hotspot with the diameter which depends on the photon energy, and the nanowire temperature and biasing conditions. Our hotspot model indicates that under the subcritical current bias of the 2D stripe, the electric field penetrates the superconductor at the hotspot boundary, leading to suppression of the stripe superconducting properties and accelerated development of a voltage transient across the stripe.

Refine search results

Easy Vortex Motion in an Artificial Channel of YBa_2Cu_3O_{7-δ} Superconducting Films

Investigation Details of Vortex Density in Laser-Written Π-Shaped Channel of YBCO Bridge by Means of I-V Dependences

Current Distribution in Y-Ba-Cu-O Superconducting Microbridges Containing Π-Shaped Channel for Easy Vortex Motion

Ultrafast Phenomena in Freestanding LT-GaAs Devices

Ultrathin NbN Films for Superconducting Single-Photon Detectors

Technology of Ultrathin NbN and NbTiN Films for Superconducting Photodetectors

Dynamics of Hotspot Formation in Nanostructured Superconducting Stripes Excited with Single Photons