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This paper presents an antenna-coupled non-linear vanadium dioxide (VO2) microbolometer operating in the non-linear metal–insulator transition (MIT) region with an ultra-high responsivity of 6.55 × 104 V/W. Sputtered VO2 films used in this device exhibit 104 times change in resistivity between the dielectric and conductive states. The VO2 microbolometer is coupled to a wideband dipole antenna operating at 31–55 GHz and a coplanar waveguide for probed measurement. To enhance the sensitivity, the sensor is suspended in air by micro-electro-mechanical systems process. The large thermal coefficient of resistance of VO2 is utilized by DC biasing the device in the MIT region. Measurements for the fabricated sensor were performed, and a high responsivity was demonstrated, owing to non-linear conductivity change in the transition region. The measured sensitivity is >102 times higher than the state-of-the-art sensors. In addition, the concept of utilizing the proposed VO2 sensor in a mmWave imager was demonstrated by the radiation pattern measurement of a 4 × 4 (16 elements) antenna-coupled VO2 sensor array. The results presented in this work reveal the initial step to employ VO2's MIT for a hyper-sensitive sensor in future mmWave sensing and imaging applications.
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Continuous Phase Control of Vanadium Dioxide Films
Abstract Vanadium dioxide (VO2) undergoes a metal-insulator transition (MIT) at approximately 68 °C, with associated sharp changes in its physical (e.g., optical, electrical, and mechanical) properties. This behavior makes VO2 films of interest in many potential applications, including memory devices, switches, sensors, and optical modulators. For ON/OFF like digital applications, an abrupt switching behavior is ideal. However, to continuously change VO2 metal/insulator phase ratio for analog-like operation, the intrinsic hysteresis characteristic of VO2 MIT renders the phase control becoming a formidable challenge. This paper considers the problem of controlling and tracking desired optical transmittance via continuous phase ratio change. The problem becomes worse while considering the differences of individual thin-film samples and the hysteresis associated with the phase change within a narrow temperature range. This paper reports a robust feedback controller using an optical transmittance measurement and based on an uncertainty and disturbance estimator (UDE) architecture. The proposed controller is capable of mitigating the adverse effect of hysteresis, while also compensating for various uncertainties. The effectiveness of the proposed methodology is demonstrated with experimental validation.
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- Award ID(s):
- 1728255
- PAR ID:
- 10199846
- Date Published:
- Journal Name:
- Journal of Dynamic Systems, Measurement, and Control
- Volume:
- 142
- Issue:
- 9
- ISSN:
- 0022-0434
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4046929
