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Performance comparison of Nb and NbN antenna-coupled microbolometers



Charles Dietlein, A. Luukanen, J. S. Penttila, H. Sipola, L. Gronberg, H. Seppa, P. Helisto, Erich N. Grossman


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 parameters from device to device exceeds any systematic difference in performance between the materials.
Conference Dates
April 9-13, 2007
Conference Location
Orlando, FL, USA
Conference Title
SPIE - The International Society for Optical Engineering, Defense & Security Symposium


bolometer, millimeter-wave, terahertz


Dietlein, C. , Luukanen, A. , Penttila, J. , Sipola, H. , Gronberg, L. , Seppa, H. , Helisto, P. and Grossman, E. (2007), Performance comparison of Nb and NbN antenna-coupled microbolometers, SPIE - The International Society for Optical Engineering, Defense & Security Symposium, Orlando, FL, USA, [online], (Accessed April 18, 2024)
Created April 8, 2007, Updated October 12, 2021