Investigation of TiAlV as absorber and WO3-VxOy as active material for terahertz microbolometers

2022-6-28
Atik, Bahar
Terahertz technology continues to evolve rapidly from laboratory setups to commercial devices. The foreseen future of the THz technology has accelerated the fabrication of detectors that are sensitive in this frequency range. Current efforts for THz imaging applications have focused on using the mature microbolometer technology which has proven to be useful in the IR region. In microbolometers, the incoming radiation becomes absorbed in the absorber layer resulting in an increase in temperature. The electrical resistance of the active material layer changes with temperature, and the resultant resistance change is read by readout circuits. The objective of this thesis is to evaluate these two critical layers, absorber and active material layers, for THz microbolometer applications. For broadband THz imaging purposes, TiAlV thin film is investigated as the potential absorber layer. Owing to its lower conductivity compared to other metals and compatibility to microfabrication techniques, by tailoring the sheet resistance with control in layer thickness, significant enhancement in THz absorption is observed. Here, the absorption of THz radiation will not increase the temperature as much as the more energetic IR waves. Hence, it is essential for a THz microbolometer to have a high temperature coefficient of resistance (TCR). For this purpose, the effect of V-W reactive co-sputtering is studied, and WO3-VxOy is investigated as the potential active material layer. As the sputtering power of W increased, new phases appeared, and this has opened a pathway toward tuning the TCR of the film to a desired value by changing the characteristics of VxOy films. In addition, properties of VxOy and WO3-VxOy layers are evaluated in the THz region as a function of temperature for the first time. Nondestructive characterization of these temperature sensitive materials gives a deep insight on their use in THz microbolometers.

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Citation Formats
B. Atik, “Investigation of TiAlV as absorber and WO3-VxOy as active material for terahertz microbolometers,” M.S. - Master of Science, Middle East Technical University, 2022.