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Gol'tsman, G. N.; Karasik, B. S.; Okunev, O. V.; Dzardanov, A. L.; Gershenzon, E. M.; Ekstrom, H.; Jacobsson, S.; Kollberg, E. |
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Title |
NbN hot electron superconducting mixers for 100 GHz operation |
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1995 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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5 |
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2 |
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3065-3068 |
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Keywords |
NbN HEB mixers |
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Abstract |
NbN is a promising superconducting material for hot-electron superconducting mixers with an IF bandwidth larger than 1 GHz. In the 1OO GHz frequency range, the following parameters were obtained for 50 /spl Aring/ thick NbN films at 4.2 K: receiver noise temperature (DSB) /spl sim/1000 K; conversion loss /spl sim/10 dB; IF bandwidth /spl sim/1 GHz; and local oscillator power /spl sim/1 /spl mu/W. An increase of the critical current of the NbN film, increased working temperature, and a better mixer matching may allow a broader IF bandwidth up to 2 GHz, reduced conversion losses down to 3-5 dB and a receiver noise temperature (DSB) down to 200-300 K. |
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1051-8223 |
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About LO power required |
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255 |
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Yagubov, P.; Gol'tsman, G.; Voronov, B.; Seidman, L.; Siomash, V.; Cherednichenko, S.; Gershenzon, E. |
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Title |
The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate |
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Conference Article |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 7th Int. Symp. Space Terahertz Technol. |
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290-302 |
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NbN HEB mixers, fabrication process |
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We report on some unusual features observed during fabrication of ultrathin NbN films with high Tc. The films were used to fabricate HEB mixers, which were evaluated for IF bandwidth measurements at 140 GHz. Ultrathin films were fabricated using reactive dc magnetron sputtering with a discharge current source. Reproducible parameters of the films are assured keeping constant the difference between the discharge voltage in pure argon, and in a gas mixture, for the same current. A maximum bandwidth of 4 GHz at optimal LO and dc bias was obtained for mixer chip based on NbN film 35 A thick with Tc = 11 K. |
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Charlottesville, Virginia, USA |
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266 |
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Semenov, Alexei; Richter, Heiko; Smirnov, Konstantin; Voronov, Boris; Gol'tsman, Gregory; Hübers, Heinz-Wilhelm |
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Title |
The development of terahertz superconducting hot-electron bolometric mixers |
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2004 |
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Supercond. Sci. Technol. |
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Supercond. Sci. Technol. |
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17 |
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5 |
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436-439 |
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Keywords |
NbN HEB mixers |
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We present recent advances in the development of NbN hot-electron bolometric (HEB) mixers for flying terahertz heterodyne receivers. Three important issues have been addressed: the quality of the source NbN films, the effect of the bolometer size on the spectral properties of different planar feed antennas, and the local oscillator (LO) power required for optimal operation of the mixer. Studies of the NbN films with an atomic force microscope indicated a surface structure that may affect the performance of the smallest mixers. Measured spectral gain and noise temperature suggest that at frequencies above 2.5 THz the spiral feed provides better overall performance than the double-slot feed. Direct measurements of the optimal LO power support earlier estimates made in the framework of the uniform mixer model. |
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357 |
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Author |
Kroug, M.; Yagoubov, P.; Gol'tsman, G.; Kollberg, E. |
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Title |
NbN quasioptical phonon cooled hot electron bolometric mixers at THz frequencies |
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Conference Article |
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1997 |
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Inst. Phys. Conf. Ser. |
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Inst. Phys. Conf. Ser. |
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1 |
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405-408 |
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NbN HEB mixers |
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Veldhoven |
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Bristol |
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0951-3248 |
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3rd Eur. Conf. on Applied Superconductivity |
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1600 |
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Cherednichenko, S.; Yagoubov, P.; Il'In, K.; Gol'tsman, G.; Gershenzon, E. |
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Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates |
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1997 |
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Proc. 8th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 8th Int. Symp. Space Terahertz Technol. |
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245-257 |
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Keywords |
NbN HEB mixers, fabrication process |
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The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature. |
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276 |
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