Niobium microbolometers for far-infrared detection

A terahertz detector operating at room temperature

“…To ensure good performances of a detector, it is crucial to have high temperature coefficient of resistance ( TCR ), which is defined as dT dR R 1 TCR (1) in Fig.4. we can see the detector's TCR is about 0.9% at room temperature (T=300K), which is much larger than that of Nb and Bi bolometers at the same temperature 6,7 .…”

“…The resistance change can be written as iv R (3) dT dR G 1 (4) here is the response coefficient and G is the thermal conductance of the detector. Solving for v and differentiating with respect to i gives (5) The differential resistance of a detector as a function of bias current i at room temperature is presented in Fig.5.The responsivity is an important parameter for a THz detector, which can be written as i (6) The best responsivity estimated from Eq.5 and Eq.6 is about 140 V/W at a bias current of 2 mA. However, a value of 100.5 V/W is experimentally got, revealing about 72% couple efficiency of testing system for the THz radiation signal.…”

Perspective Material and Applications of Uncooled Metal Bolometers

“…Here Vn is determined by [8]- [10] = √ 2 + ℎ 2 + 1/ 2 + 2 (2) where VJ, Vph, and V1/f are the Johnson, phonon (temperature fluctuations) and 1/f noise voltages of the bolometer, and Vamp is the input noise voltage of the amplifier. At present, the lowest value Vamp is 0.9 nV in a one hertz output bandwidth with a frequencies more than 200 Hz (for example LME49990, and ADA4898) for the uncooled precision ultralow noise operational amplifiers.…”

“…Therefore, uncooled thin film metal bolometers usually operate in the frequency range of white noise. For uncooled metal bolometers the main component of white noise is the Johnson noise voltage (VJ >> Vph) [8] that is determined by…”

“…For example, if to compare the sensitivity of two bolometers from different metals, by using the equality of resistance [3], [8], in this case the thickness of the resistive elements from low-resistivity metals will be an order of magnitude less than the thickness of the resistive elements from high-resistivity metals (for the same size of the sensitive area). Consequently, the bolometers based on the resistive elements with the smallest thickness will have the better sensitivity and performance.…”