| Records |
| Author |
Lindgren, M.; Trifonov, V.; Zorin, M.; Danerud, M.; Winkler, D.; Karasik, B. S.; Gol’tsman, G. N.; Gershenzon, E.M. |
| Title |
Transient resistive photoresponse of YBa2Cu3O7−δ films using low power 0.8 and 10.6 μm laser radiation |
Type |
Journal Article |
| Year |
1994 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
64 |
Issue |
22 |
Pages |
3036-3038 |
| Keywords |
YBCO HTS HEB, nonequilibrium |
| Abstract |
Thin YBa2Cu3O7−δ laser deposited films were patterned into devices consisting of ten parallel 1 μm wide strips. Nonequilibrium picosecond and bolometric photoresponses were studied by the use of 17 ps full width at half‐maximum laser pulses and amplitude modulated radiation from an AlGaAs laser up to 10 GHz and from a CO2 laser up to 1 GHz. The time and frequency domain measurements were in agreement. The fast response can be explained by electron heating. The use of low optical power and a sensitive measurement system excluded any nonlinear transient processes and kinetic inductance changes in the superconducting state. At 1 GHz modulation frequency, the responsivity was ∼1.2 V/W both for 0.8 and 10.6 μm wavelengths. The sensitivity of a fast and spectrally broadband infrared detector is discussed. |
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0003-6951 |
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1639 |
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| Author |
Danerud, M.; Winkler, D.; Lindgren, M.; Zorin, M.; Trifonov, V.; Karasik, B. S.; Gol’tsman, G. N.; Gershenzon, E. M. |
| Title |
Nonequilibrium and bolometric photoresponse in patterned YBa2Cu3O7−δ thin films |
Type |
Journal Article |
| Year |
1994 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
| Volume |
76 |
Issue |
3 |
Pages |
1902-1909 |
| Keywords |
YBCO HTS HEB detector, nonequilibrium response |
| Abstract |
Epitaxial laser deposited YBa2Cu3O7−δ films of ∼50 nm thickness were patterned into detectors consisting of ten parallel 1 μm wide strips in order to study nonequilibrium and bolometric effects. Typically, the patterned samples had critical temperatures around 86 K, transition widths around 2 K and critical current densities above 1×106A/cm2 at 77 K. Pulsed laser measurements at 0.8 μm wavelength (17 ps full width at half maximum) showed a ∼30 ps response, attributed to electron heating, followed by a slower bolometric decay. Amplitude modulation in the band fmod=100 kHz–10 GHz of a laser with wavelength λ=0.8 μm showed two different thermal relaxations in the photoresponse. Phonon escape from the film (∼3 ns) is the limiting process, followed by heat diffusion in the substrate. Similar relaxations were also seen for λ=10.6 μm. The photoresponse measurements were made with the film in the resistive state and extended into the normal state. These states were created by supercritical bias currents. Measurements between 75 and 95 K (i.e., from below to above Tc) showed that the photoresponse was proportional to dR/dT for fmod=1 MHz and 4 GHz. The fast response is limited by the electron‐phonon scattering time, estimated to 1.8 ps from experimental data. The responsivity both at 0.8 and 10.6 μm wavelength was ∼1.2 V/W at fmod=1 GHz and the noise equivalent power was calculated to 1.5×10−9 WHz−1/2 for the fast response. |
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0021-8979 |
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1637 |
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Voronov, B. M.; Gershenzon, E. M.; Gol'tsman, G. N.; Gubkina, T. O.; Semash, V. D. |
| Title |
Superconductive properties of ultrathin NbN films on different substrates |
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Journal Article |
| Year |
1994 |
Publication |
Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
Abbreviated Journal |
Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
| Volume |
7 |
Issue |
6 |
Pages |
1097-1102 |
| Keywords |
NbN films |
| Abstract |
A study was made on dependence of surface resistance, critical temperature and width of superconducting transition on application temperature and thickness of NbN films, which varied within the range of 3-10 nm. Plates of sapphire, fused and monocrystalline quartz, MgO, as well as Si and silicon oxide were used as substrates. NbN films with 160 μθ·cm specific resistance and 16.5 K (Tc) critical temperature were obtained on sapphire substrates. Intensive growth of ΔTc was noted for films, applied on fused quartz, with increase of precipitation temperature. This is explained by occurrence of high tensile stresses in NbN films, caused by sufficient difference of thermal coefficients of expansion of NbN and quartz. |
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Russian |
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0131-5366 |
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Сверхпроводниковые свойства ультратонких пленок NbN на различных подложках |
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1631 |
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Sergeev, A. V.; Semenov, A. D.; Kouminov, P.; Trifonov, V.; Goghidze, I. G.; Karasik, B. S.; Gol’tsman, G. N.; Gershenzon, E. M. |
| Title |
Transparency of a YBa2Cu3O7-film/substrate interface for thermal phonons measured by means of voltage response to radiation |
Type |
Journal Article |
| Year |
1994 |
Publication |
Phys. Rev. B Condens. Matter. |
Abbreviated Journal |
Phys. Rev. B Condens. Matter. |
| Volume |
49 |
Issue |
13 |
Pages |
9091-9096 |
| Keywords |
YBCO films |
| Abstract |
The transparency of a film/substrate interface for thermal phonons was investigated for YBa2Cu3O7 thin films deposited on MgO, Al2O3, LaAlO3, NdGaO3, and ZrO2 substrates. Both voltage response to pulsed-visible and to continuously modulated far-infrared radiation show two regimes of heat escape from the film to the substrate. That one dominated by the thermal boundary resistance at the film/substrate interface provides an initial exponential decay of the response. The other one prevailing at longer times or smaller modulation frequencies causes much slower decay and is governed by phonon diffusion in the substrate. The transparency of the boundary for phonons incident from the film on the substrate and also from the substrate on the film was determined separately from the characteristic time of the exponential decay and from the time at which one regime was changed to the other. Taking into account the specific heat of optical phonons and the temperature dependence of the group velocity of acoustic phonons, we show that the body of experimental data agrees with acoustic mismatch theory rather than with the model that assumes strong diffusive scattering of phonons at the interface. |
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0163-1829 |
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PMID:10009690 |
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1648 |
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Gol'tsman, G. N.; Goghidze, I. G.; Kouminov, P. B.; Karasik, B. S.; Semenov, A. D.; Gershenzon, E. M. |
| Title |
Influence of grain boundary weak links on the nonequilibrium response of YBaCuO thin films to short laser pulses |
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Journal Article |
| Year |
1994 |
Publication |
J. Supercond. |
Abbreviated Journal |
J. Supercond. |
| Volume |
7 |
Issue |
4 |
Pages |
751-755 |
| Keywords |
YBCO HTS detector, nonequilibrium response |
| Abstract |
The transient voltage response in both epitaxial and granular YBaCuO thin films to 80 ps pulses of YAG∶Nd laser radiation of wavelength 0.63 and 1.54 μm was studied. In the normal and resistive states both types of films demonstrate two components: a nonequilibrium picosecond component and a bolometric nanosecond one. The normalized amplitudes are almost the same for all films. In the superconducting state we observed a kinetic inductive response and two-component shape after integration. The normalized amplitude of the response in granular films is up to five orders of magnitude larger than in epitaxial films. We interpret the nonequilibrium response in terms of a suppression of the order parameter by the excess of quasiparticles followed by the change of resistance in the normal and resistive states or kinetic inductance in the superconducting state. The sharp rise of inductive response in granular films is explained both by a diminishing of the cross section for current percolation through the disordered network of Josephson weak links and by a decrease of condensate density in neighboring regions. |
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0896-1107 |
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1636 |
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