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4 May 2007 Performance comparison of Nb and NbN antenna-coupled microbolometers
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We report the experimental results of a comparison between free-standing Nb and NbN microbolometer bridges coupled to equiangular spiral antennas on Si substrates. Because of the difference in material resistivity, bolometer resistance and aspect ratio is varied independently. Room-temperature antenna patterns measured at 650 GHz with a backward-wave oscillator are presented, as are I-V curves at T = 300 K and at T = 4 K. At room temperature, zero-bias resistance and specific responsivity are examined, and at 4 K, normal-state resistance and saturation power are studied. Nb devices display significantly lower saturation powers than NbN devices whose dimensions have been adjusted to provide equal resistance. However, for both materials, the inferred thermal conductances are higher than predicted by the Wiedemann-Franz relation, by approximately a factor of ~2 for Nb and a factor of ~5 for NbN. In general, and especially for the room-temperature responsivity, the substantial spread in device parameters from device to device exceeds any systematic difference in performance between the materials.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
C. Dietlein, A. Luukanen, J. S. Penttilä, H. Sipola, L. Grönberg, H. Seppä, P. Helistö, and E. N. Grossman "Performance comparison of Nb and NbN antenna-coupled microbolometers", Proc. SPIE 6549, Terahertz for Military and Security Applications V, 65490M (4 May 2007);

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