Micromechanical IR thermal detector using torsional oscillation: Improvement of resonator profile for high sensitivity

Abstract

An infrared (IR) thermal detector, which used the torsional oscillation of a micromechanical resonator, was developed to achieve a high sensitivity. The detector has a bimaterial structure consisting of a tense Si film (oscillating body) and a metal film (IR absorber). Owing to the difference in thermal expansion between the two materials, the resonator is bent by light incidence. Because the axis of torsion is bent from the initial flat state, the spring for torsional oscillation hardens and resonant frequency shifts. To enhance bending, an Al film with a large coefficient of thermal expansion was used. In addition, the tension in the polycrystalline Si film was enhanced by metal-induced lateral crystallization using biomineralized Ni nanoparticles. The fabricated detector was flat under initial conditions and showed a bending response to the light incidence and heating. The present IR detector achieved a thermal coefficient of frequency of 1000 ppm/K, which was one order larger than that of the conventional micromechanical IR sensors.

Shape memory polymer resonators as highly sensitive uncooled infrared detectors

“…The best TCF is ~8% K −1 at an operation temperature of T sub = 45 °C. This TCF is 2 orders of magnitude higher than the best TCF reported so far (~0.1% K −1 ) for IR resonant sensors 25 . In addition, the TCF is more than an order of magnitude higher than resonant temperature sensors 45–47 , for which the best reported TCF is 1.7% K −1 .…”

“…The TCF were calculated according to the normalized frequency change within each 5 °C step using the measurements from Figure 2.a. The best TCF is around 8% at the operation temperature of Tsub=45 °C; which is 2 order of magnitude higher than the best TCF reported so far for IR resonant sensors 25 . Since there is a tradeoff between the TCF and Q, the operation temperature of Tsub=45 °C has very high AD value for the integration time τ=500 ms as it is illustrated in Figure 3.b.…”

“…) consists of the two key parameters that are specific for resonant IR sensors. High sensitivity can be achieved by increasing the TCF 25,26 and/or improving the frequency stability [27][28][29] .…”

Terahertz Detectors Using Microelectromechanical System Resonators

“…A number of groups have demonstrated that MEMS/NEMS resonators can work as fast and highly sensitive THz/IR detectors. Depending on the vibrational mode and geometrical shape, they can be categorized as torsional mode [72][73][74][75][76], bending mode [59,77], or membranous shape [57,78,79]. Table 1 provides a survey of the performance of THz/IR detectors based on MEMS/NEMS resonators, allowing for an objective comparison of existing MEMS bolometers.…”

Mechanical Characterization of Torsional Micropaddles Using Atomic Force Microscopy

“…Their use as micromirrors has led to the rapid advances in digital light processing [1]; they have been shown to act as thermal infrared detectors [2,3] and also as resonant mass sensing devices [4,5]. A resonant micropaddle is one such resonant torsional system and has been considered as a potential bio/chemical sensor platform [6,7].…”