Infrared Transmission Characteristics of Phase Transitioning VO2 on Various Substrates

Abstract

Infrared transmission characteristics of VO2 thin films synthesized on multiple substrates, using a low-pressure direct oxidation technique, have been characterized. Material characterization of these films indicates high material quality, which resulted in large variation of electrical and optical properties at phase transition. A change in optical transmissivity greater than 80% was observed for these films utilizing infrared (IR) laser illumination at 1550 nm. Phase transition enabled by temperature change induced by a pulsed high-power laser beam resulted in modulated IR laser transmission with a low time constant in VO2 on transparent quartz and muscovite substrates. Investigation of the effect of mechanical strain on phase transition in VO2 grown on flexible muscovite substrate indicate shift in transition temperature to higher for tensile and lower for compressive strains.

VO2 Thin Film Enabled Free Space Modulation of Infrared Light Using Pulsed Electric Field

“…Prior to the deposition of Ti/Au metal fingers on the circular VO 2 thin films, they were investigated though multiple characterization methods. AFM images of the VO 2 thin films were captured (using a Veeco Dimension 3100 instrument) and the RMS roughness of the VO 2 film surface were determined as a measure of surface quality. , Structural characterization was performed through X-ray diffraction (XRD) using a Rigaku Ultima IV system (Cu Kα radiation, wavelength 15.406 nm), which provided information on their crystalline quality. According to the National Bureau of Standards, Silicon has been selected as the Standard Reference Materials (SRM-640) …”

“…In previous work, we demonstrated near-IR modulation using the VO 2 film on the GaN substrate for 790 and 1550 nm IR beam, which resulted in optical modulation of 7 and 14%, respectively, for up to 300 μs pulses. However, the IR modulation was demonstrated with the application of external heating to the VO 2 film to vary the temperature of the film and initiate phase transition and significant optical modulation. , In order to trigger the semiconductor-to-metal transition (SMT) with electric field only, past reports mentioned large voltage requirements to cause a noticeable transition. , In this work, we have synthesized a good quality VO 2 film on a small circular area of the GaN substrate and the oxidized silicon-on-insulator (SOI) substrate, using a modified synthesis method, , and have used interdigitated metal finger patterns on the VO 2 film layers to apply required electric field. The film quality and device geometry resulted in a fast phase transition via localized heating of the membrane, allowing for more than 50% intensity modulation at 2600 nm IR wavelength with frequencies exceeding 10 kHz.…”

“…However, the IR modulation was demonstrated with the application of external heating to the VO 2 film to vary the temperature of the film and initiate phase transition and significant optical modulation. 35,41 In order to trigger the semiconductor-to-metal transition (SMT) with electric field only, past reports mentioned large voltage requirements to cause a noticeable transition. 44,45 In this work, we have synthesized a good quality VO 2 film on a small circular area of the GaN substrate and the oxidized silicon-on-insulator (SOI) substrate, using a modified synthesis method, 35,41 and have used interdigitated metal finger patterns on the VO 2 film layers to apply required electric field.…”

“…35,41 In order to trigger the semiconductor-to-metal transition (SMT) with electric field only, past reports mentioned large voltage requirements to cause a noticeable transition. 44,45 In this work, we have synthesized a good quality VO 2 film on a small circular area of the GaN substrate and the oxidized silicon-on-insulator (SOI) substrate, using a modified synthesis method, 35,41 and have used interdigitated metal finger patterns on the VO 2 film layers to apply required electric field. The film quality and device geometry resulted in a fast phase transition via localized heating of the membrane, allowing for more than 50% intensity modulation at 2600 nm IR wavelength with frequencies exceeding 10 kHz.…”

“…Among these recent technologies, vanadium dioxide (VO 2 ), which is a well-known thermo- and electrochromic material, has emerged as an attractive candidate for IR modulation due to dramatic change in its optical properties as it undergoes a phase change from a monoclinic insulating phase to a rutile metallic phase at ∼68 °C. − Interestingly for VO 2 , phase transition can also be achieved with electric field and strain. ,, The phase change causes a dramatic change in resistance of the VO 2 thin films, by up to 3–4 orders of magnitude, and takes place on the order of ns, , opening up potential applications in high-speed switching devices. − While the insulator phase of VO 2 is quite transparent to IR radiation (more transparent at higher wavelength), it is much more reflective in the metallic phase. − Taking advantage of this behavior, optoelectronic devices utilizing IMT-based modulation of light for near-IR modulation have been demonstrated and reported earlier. , While growth of VO 2 thin films has been commonly reported on Si, SiO 2 , TiO 2 , quartz, and sapphire, ,− reports on wide-bandgap semiconducting materials as the VO 2 substrate is rather limited. ,− Compared to traditional substrates, the wide-bandgap substrate such as GaN film offers several advantages, including transparency at visible and infrared wavelengths, chemical inertness, and strong piezoelectric properties, which can lead to novel integrated platform for sensing and detection. ,, …”