Vanadium dioxide (VO2) undergoes a metal-insulator transition (MIT) at 68°C, at which point its electrical conductivity changes by several orders of magnitude. This extremely fast transition (Δt < 100 fs) can be induced thermally, mechanically, electrically, or optically. The combination of fast switching times and response to a broad range of external stimuli make VO2 an ideal material for a variety of novel devices and sensors. While the MIT in VO2 has been exploited for a variety of microwave/terahertz applications (i.e. tunable filters and modulators), very few devices exploiting the fast switching time of VO2 have been reported. The electrical properties of thin film VO2 (conductivity, carrier concentration, switching speed, etc.) are highly dependent on growth and post-processing conditions. The optimization of these conditions is therefore critical to the design and fabrication of VO2 devices. This paper will report the effects of various pulsed laser deposition (PLD) growth conditions on the metal-insulator transition in thin film VO2. In particular, we report the effect of PLD growth conditions on the stress/strain state of the VO2 layer, and the subsequent change in electrical properties. Finally, results from fabricated VO2 devices (THz emitters and THz modulators) will be presented.
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Nicholas A. Charipar ; Kristin M. Charipar ; Heungsoo Kim ; Scott A. Mathews ; Eric Breckenfeld, et al.
Laser processing of VO2 thin films for THz devices and metamaterials applications
", Proc. SPIE 10091, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXII, 1009102 (February 20, 2017); doi:10.1117/12.2256120; http://dx.doi.org/10.1117/12.2256120