| 1. |
- Bevilacqua, Stella, 1981, et al.
(author)
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Characterisation and Modeling of MgB2 HEBs IF impedance
- 2016
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In: Swedish Microwave Days March 15-16, 2016, Linköping, Sweden. ; , s. 55-
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Conference paper (peer-reviewed)abstract
- Here we present the method which allows to measure quiteaccurately the HEB impedance employing just one cooling.By knowing the HEB IF impedance a coupling matchingnetwork can be designed for a possible packaged receiver.
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| 2. |
- Bevilacqua, Stella, 1981, et al.
(author)
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HEB mixers for THz radio astronomy
- 2014
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In: Swedish Microwave Days March 11-12, 2014.
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Conference paper (peer-reviewed)abstract
- Hot-Electron Bolometer (HEB) mixers made of 10 nm superconducting MgB2 films are discussed for high sensitivity high spectral resolution spectrometers for radio astronomy. The key advantage of the used MgB2 films is in achievement of wider Intermediate Frequency (IF) bandwidth.
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| 3. |
- Bevilacqua, Stella, 1981, et al.
(author)
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Low noise MgB2 terahertz hot-electron bolometer mixers
- 2012
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:3
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Journal article (peer-reviewed)abstract
- We report on low noise terahertz bolometric mixers made of MgB2 superconducting thin films. For a 10-nm-thick MgB2 film, the lowest mixer noise temperature was 600 K at 600 GHz. For 30 to 10-nm-thick films, the mixer gain bandwidth is an inverse function of the film thickness, reaching 3.4 GHz for the 10-nm film. As the critical temperature of the film decreases, the gain bandwidth also decreases, indicating the importance of high quality thin films for large gain bandwidth mixers. The results indicate the prospect of achieving a mixer gain bandwidth as large as 10-8 GHz for 3 to 5-nm-thick MgB2 films.
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| 4. |
- Bevilacqua, Stella, 1981, et al.
(author)
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MgB2 Hot-Electron Bolometer Mixers at Terahertz Frequencies
- 2015
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3, s. 2301104-
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Journal article (peer-reviewed)abstract
- In this paper, we compare the performance of MgB2 Hot-Electron Bolometer Mixers operating at Local Oscillator frequencies of 0.6 and 1.63 THz. The minimum noise temperatures that were obtained are 700 and 1150 K for 0.6 and 1.63 THz, respectively. The receiver noise bandwidth is of the order of 2.2-3 GHz for 10-nm-thick HEB devices with a Tc of 8.5 K. Sub-micrometer size HEBs were also fabricated with no degradation of the initial film quality when a 20-nm MgB2 film with a Tc of 22 K was used. In the direct detection mode, the maximum voltage responsivity is in the range of 1-2 kV/W at 1.63 THz and the optimal bias current is around 1/4-1/3 of the Ic at 4.2 K.
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| 5. |
- Bevilacqua, Stella, 1981, et al.
(author)
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Study of IF bandwidth of MgB2 phonon-cooled hot-electron bolometer mixers
- 2013
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In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 3:4, s. 409-415
-
Journal article (peer-reviewed)abstract
- A noise bandwidth (NBW) of 6-7 GHz was obtained for Hot-Electron Bolometer (HEB) mixers made of 10 nm MgB2 films. A systematic investigation of the (IF) gain bandwidth as a function of the MgB2 film thickness (30 nm, 15 nm and 10 nm) is also presented. The gain bandwidth (GBW) of 3.4 GHz was measured for a 10 nm film, corresponding to a mixer time constant of 47 ps. For 10 nm films a reduction of the GBW was observed with the reduction of the critical temperature (Tc). Experimental data were analyzed using the two-temperature model. From the theoretical analysis, the electron-phonon time (τe-ph), the phonon escape time (τesc) and the electron and phonon specific heats (ce, cph) were extrapolated giving the first model for HEB mixers of MgB2 films.
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| 6. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Submicrometer MgB2 hot electron bolometer mixers
- 2013
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In: The 24th International Symposium on Space Terahertz Technology.
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Conference paper (peer-reviewed)abstract
- Phonon-cooled hot electron bolometer mixers based on MgB2 film are promising candidates for THz radio astronomy at frequency above 1 THz. The short electron-phonon interaction time and the high critical temperature of the MgB2 (39 K in the bulk), compared to other intermetallic compounds, make it suitable for applications where wide IF bandwidth and low noise are needed. The currently achieved gain and noise bandwidths are 3.4 GHz and 7 GHz for HEBs fabricated in 10 nm MgB2 films. The noise temperature of 800 K was measured at 600 GHz local oscillator (LO) frequency using the Y-factor technique.MgB2 has been demonstrated to be sensitive to the oxygen as well as water, therefore it makes the fabrication of sub-µm HEBs very challenging. HEBs were fabricated using electron beam lithography in 10 nm MgB2 films with a bolometer area in the range of 0.09 and 0.25 µm2. We report the performance of the devices respect to the noise temperature at LO frequency up to 2.5 THz. Using the isothermal technique the LO power requirement was estimated respect to the bolometer area. Based on the material parameters obtained from the experiments, the two temperature model simulations showed a gain bandwidth as large as 8-10 GHz for thin MgB2 films.
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| 7. |
- Bevilacqua, Stella, 1981, et al.
(author)
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Wideband MgB2 Hot-Electron Bolometer Mixers: IF Impedance Characterisation and Modeling
- 2016
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In: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 26:3, s. 2300105-
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Journal article (peer-reviewed)abstract
- In this paper we present a method for low signal S11 parameter vector measurements of a cryogenic device in the microwave frequency range. In particular, the intermediate frequency (IF) impedance of MgB2 Hot-electron Bolometer (HEB) mixers was investigated over a frequency range of 100 MHz to 10 GHz. A new cryogenic calibration technique, which employs the HEB as a calibration kitandrequires two consecutive thermal cycles, was developed for this purpose.The real part of measured IF impedance showed a strong correlationwith the differential resistance (dV/dI) obtained from the dc I-V curves while the imaginary partwas capacitive for almost the entire frequency range.
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| 8. |
- Cherednichenko, Serguei, 1970, et al.
(author)
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Study of MgB2 HEB mixers vs the LO frequency and the bath temperature
- 2015
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In: 26th International Symposium on Space Terahertz Technology March 16-18, 2015, Cambridge, United States. ; , s. M2-1
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Conference paper (peer-reviewed)abstract
- We investigate the noise and the gain of MgB2 Hot-Electron Bolometer (HEB) mixers at 1.63THz LO. The critical temperature of the HEB was 22K and the film thickness was 20nm. At 4.2K and 12K bath temperatures the lowest obtained receiver noise temperatures are 1700K and 2100K,respectively, with a noise bandwidth of about 4.6GHz. The gain bandwidth is about 3GHz in both cases.
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| 9. |
- Novoselov, Evgenii, 1988, et al.
(author)
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Effect of the Critical and Operational Temperatures on the Sensitivity of MgB2 HEB Mixers
- 2016
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In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 6:2, s. 238-277
-
Journal article (peer-reviewed)abstract
- In this paper, we present a study of the noise and thegain of MgB hot-electron bolometer mixers with different critical temperatures and at various operation temperatures. At a local oscillator (LO) frequency of 1.63 THz the minimum input receiver noise temperature was 700 K with a gain of 18 dB for a device with a of 8.5 K. For a device with a of 22.5 K the corresponding values were 1700 K and 19 dB. For the latter device the was 2150 K at a bath temperature of 12 K, which is not achievable with Nb-compound based HEB mixers. We present and compare different methods for measurements of the HEB mixer gain and the output noise.
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| 10. |
- Novoselov, Evgenii, 1988, et al.
(author)
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Noise measurements of the low Tc MgB2 HEB mixer at 1.6THz and 2.6THz
- 2015
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In: 26th International Symposium on Space Terahertz Technology March 16-18, 2015, Cambridge, United States. ; , s. P-31
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Conference paper (peer-reviewed)abstract
- We present results on MgB2 hot-electron bolometer noise measurements to show reproducibility of achieved results and robustness of the fabricated devices, which being passivated with silicon nitride shows the same performance after 1.5 year storing in nitrogen atmosphere. Noise temperature measurements were performed for the HEB made of 10nm MgB2 thin film on Al2O3 with Tc of 8.5K for 1.6THz LO at 2.7K and 4.2K. The minimum double side band noise temperatures corrected for optical losses for different bath temperatures were 700K and 1150K, whereas the noise bandwidth was 3.2GHz and 3.5GHz, respectively. The mixer output noise temperature and the conversion gain were 26K and -17.7dB, 27K and -14.9dB, respectively. For 2.6THz LO at 2.7K the corresponding values are 1200K and 3.7GHz.
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