Capacitively coupled hot-electron nanobolometer with SIN tunnel junctions

Leonid S. Kuzmin; M. Fominsky; A. Kalabukhov; D. Golubev; M. Tarasov

doi:10.1117/12.459193

17 February 2003 Capacitively Coupled Hot-Electron Nanobolometer with SIN Tunnel Junctions

Leonid S. Kuzmin, M. Fominsky, A. Kalabukhov, D. Golubev, M. Tarasov

Proceedings Volume 4855, Millimeter and Submillimeter Detectors for Astronomy; (2003) https://doi.org/10.1117/12.459193
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

A capacitively coupled hot-electron nanobolometer (CC-HEB) is the simplest and most effective antenna-coupled bolometer. The bolometer consists of a small absorber connected to the superconducting antenna by tunnel junctions. The tunnel junctions used for high-frequency coupling also give perfect thermal isolation of hot electrons in the small volume of the absorber. The same tunnel junctions are used for temperature measurements and electron cooling. This bolometer does not suffer from the frequency limitations in the submillimeter range due to the high potential barrier of the tunnel junctions as does the microbolometer with Andreev mirrors (A-HEB), which is limited by the superconducting gap. Theoretical analyses show that the two-junction configuration more than doubles the sensitivity of the bolometer in current-biased mode compared to the single-junction configuration used for A-HEB. Another important advantage of CC-HEB is its simple two-layer technology for sample fabrication. Samples were fabricated with an absorber made of a bilayer of Cr and Al to match the impedance of the antenna. Electrodes were made of Al and tunnel junctions were formed over the Al oxide layer. The coupling capacitances of the tunnel junctions, C ≈ 20 fF, in combination with the inductance of the 10 μm absorber create a bandpass filter with a central frequency around 300 GHz. Bolometers are integrated with log-periodic and double-dipole planar antennas made of Au. The temperature response of bolometer structures was measured at temperatures down to 256 mK. In our experiment we observed dV/dT=1.3 mV/K, corresponding to responsivity S=0.2.10⁹ V/W. For amplifier noise V_na=3nV/Hz^1/2at 1 kHz the estimated total noise equivalent power is NEP=1.5.10^-17 W/Hz^1/2. The intrinsic bolometer self noise V_nbol=0.5 nV/Hz^1/2 corresponds to NEP=3.10^-18 W/Hz^1/2. For microwave evaluation of bolometer sensitivity we used a black body radiation source comprising a thin NiCr stimulator placed on the cold plate of cryostat in front of a CC-HEB attached to an extended hemisphere sapphire lens. This measurements were consistent with estimates based on the dc responsivity of the bolometer.

Citation Download Citation

Leonid S. Kuzmin, M. Fominsky, A. Kalabukhov, D. Golubev, and M. Tarasov "Capacitively Coupled Hot-Electron Nanobolometer with SIN Tunnel Junctions", Proc. SPIE 4855, Millimeter and Submillimeter Detectors for Astronomy, (17 February 2003); https://doi.org/10.1117/12.459193

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