High-T/sub c/ transition-edge bolometer for detecting guided millimeter waves

Janik, Dieter; May, Daniel; Wolf, H.; Schneider, R.

doi:10.1109/77.233927

Cited by 8 publications

(10 citation statements)

References 7 publications

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“…3,4 This includes the onset of the several stages of the transition, the intergrain critical currents, the effect of magnetic fields, the role of inhomogeneities and other kinds of disorder, and the dynamics of the vortex motion in the material. 5 Noise associated with conductivity fluctuations ͑or resistance fluctuations͒ 6,7 has the following characteristic:…”

Section: B Noise In High-t C Superconducting Materialsmentioning

confidence: 99%

Noise characteristics and detectivity of YBa2Cu3O7 superconducting bolometers: Bias current, frequency, and temperature dependence

Fardmanesh

Rothwarf

Scoles

1996

Journal of Applied Physics

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Meander line patterned infrared detectors, with values of resistance R onset at the onset temperature T c onset of 3-5 k⍀, were fabricated from YBa 2 Cu 3 O 7Ϫx superconducting material on MgO and SrTiO 3 crystalline substrates. Noise voltages from the samples were measured versus bias current, radiation modulation frequency, and temperature, in both the normal and superconducting states. Four major types of voltage noise were identified according to where they occurred in temperature relative to T c onset and the zero resistance temperature T c zero , and their dependence on frequency and bias current. They were also associated with the granularity of the superconducting film, which is related to the substrate material used. From these observations a specific cause for each type of noise is suggested. The results are as follows. ͑i͒ In the normal state with temperature T Ͼ T c onset , noise with a magnitude that is consistent with thermal ͑Johnson͒ noise is seen, but it depends linearly on bias current above a threshold value, at low frequencies. The suggested noise source is conductivity fluctuations due to Cooper pairs. ͑ii͒ Noise was found to occur below T c zero in granular films. With increasing bias current its magnitude increases, and it shifts to a lower temperature range; however, the noise magnitude becomes constant as the current goes to zero. It is weakly dependent on frequency above 400 Hz. Suggested cause is voltage fluctuations in superconductor-normal-superconductor junctions at grain boundaries. ͑iii͒ This noise also occurs below T c zero with peaks at various temperatures. With increasing bias current the peaked noise spreads to lower temperatures, but the noise goes to zero as the bias current goes to zero. Its suggested cause is magnetic flux tube motion. ͑iv͒ This noise occurs between T c onset and T c zero and is present in all samples, but lowest on samples prepared on SrTiO 3 substrates. Its suggested cause is fluctuations in the volume fraction of the superconducting phase along the current path. While the measured detectivity D* of our samples at a wavelength of 20 m was only 10 6 cm Hz 1/2 /W, engineering changes can be expected to raise the value to above 10 10 cm Hz 1/2 /W.

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Section: B Noise In High-t C Superconducting Materialsmentioning

confidence: 99%

Noise characteristics and detectivity of YBa2Cu3O7 superconducting bolometers: Bias current, frequency, and temperature dependence

Fardmanesh

Rothwarf

Scoles

1996

Journal of Applied Physics

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“…1 shows this effect for one of our samples. The shifting ofto lower temperatures has been interpreted to be an intrinsic shift by some groups [1], [5], [8], [12]. At high-bias currents this shift increases the value of the film obtained from the measured versus curve, but this is different from the real versus of the film.…”

Section: B Large-area Patternsmentioning

confidence: 98%

“…This gradient can cause an error in the dc characterizations because in most of the setups the temperature of the cold finger (holder) or the bottom of the substrate is monitored [1]- [12], while the temperature of the film is higher [2], [3]. At high-bias currents this can cause a shift oftoward the lower temperatures in the measured versus curve, as has been observed in many cases [1]- [3], [7], [8], [11]. The shift is related to the temperature gradient across the film-substrate or the substrate-cold-finger interfaces, depending on the film and the substrate dimensions.…”

Section: Introductionmentioning

confidence: 99%

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DC characteristics of patterned YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting thin-film bolometers: artifacts related to Joule heating, ambient pressure, and microstructure

Fardmanesh

Scoles

Rothwarf

1998

IEEE Trans. Appl. Supercond.

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Cataloged from PDF version of article.Joule heating due to the bias current and resistance of the material in patterned YBa2Cu3O7-x superconducting films on 250-500-mu m-thick MgO, LaAlO3, and SrTiO3 crystalline substrates, results in a number of effects: 1) a temperature rise in the film with respect to the measured temperature at the bottom of the substrate; 2) a possible thermal runaway, which may be local or uniformly distributed in the film, depending upon the dimensions of the superconducting pattern relative to that of the substrate; 3) an apparently sharper normal-to-superconducting transition in the measure R versus T curve; and 4) decrease of T-c to 60 K (Delta T-x > 20 K) after being subjected to high-bias currents j similar to 10(5) A/cm(2) under vacuum, with recovery of T-c after exposure to room atmosphere. The magnitude of R at Tc-onset is found to be dependent on bias current in granular samples, with a lower R at currents higher than some on-set value. The slope of R versus T in the transition region in our granular samples is found to be lower at higher bias currents, since the widening of the transition overcomes the shift caused by the Joule heating. These various phenomena impact the responsivity of bolometers made from these films, as well as the predictions of possible attainable responsivity and speculations of mechanisms occurring in the films. In particular, misinterpretation of the Joule heating sharpening of the R versus T curve has led to predictions of responsivities over one order of magnitude higher than are justified, and shifts in properties of the films due to heating have been misinterpreted as nonequilibrium responses of the films

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“…The effect of instability in the temperature of the film caused by high bias currents will appear as an unrealistically sharp transition in the R versus T curve. 2,5,16 The increase of the response that is due to the sharper transition dR͞dT dominates the effect of this decrease in the maximum allowed I b in Eq. ͑3͒, producing an overall increase in the responsivity for films with sharper transitions.…”

Section: Effects Of Substrate Properties and The Bias Current On Rmentioning

confidence: 99%

Control of the responsivity and the detectivity of superconductive edge-transition YBa_2Cu_3O_7–x bolometers through substrate properties

1999

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The detectivity D* limits of YBa(2)Cu(3)O(7-x) bolometers on 0.05-cm-thick crystalline substrates are investigated, and a method to increase D* to greater than 10(9) (cm Hz(1/2))/W at a 20-microm wavelength is proposed. Because the response increases proportionally with the bias current I(b), whereas the noise near T(c) (the transition or critical temperature) of our MgO and SrTiO(3) substrate samples does not, an increase in D* of these samples is obtained by an increase in I(b). Another limiting factor is the dc thermal conductance G(0) of the device, which, although controlled by the substrate-holder thermal boundary resistance for our samples, can be changed by means of thinning the substrate to increase D*. The optimal amount of thinning depends on the substrate's thermal parameters and the radiation modulation frequency. D* in our samples is also found to follow the spectral-radiation absorption of the substrate material.

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High-T/sub c/ transition-edge bolometer for detecting guided millimeter waves

Cited by 8 publications

References 7 publications

Noise characteristics and detectivity of YBa2Cu3O7 superconducting bolometers: Bias current, frequency, and temperature dependence

Noise characteristics and detectivity of YBa2Cu3O7 superconducting bolometers: Bias current, frequency, and temperature dependence

DC characteristics of patterned YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting thin-film bolometers: artifacts related to Joule heating, ambient pressure, and microstructure

Control of the responsivity and the detectivity of superconductive edge-transition YBa_2Cu_3O_7–x bolometers through substrate properties

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