Adaptive tuning of infrared emission using VO2 thin films

Abstract

Phase-transition materials provide exciting opportunities for controlling optical properties of photonic devices dynamically. Here, we systematically investigate the infrared emission from a thin film of vanadium dioxide (VO 2). We experimentally demonstrate that such thin films are promising candidates to tune and control the thermal radiation of an underlying hot body with different emissivity features. In particular, we studied two different heat sources with completely different emissivity features, i.e. a black body-like and a mirror-like heated body. The infrared emission characteristics were investigated in the 3.5-5.1 μm spectral range using the infrared thermography technique which included heating the sample, and then cooling back. Experimental results were theoretically analyzed by modelling the VO 2 film as a metamaterial for a temperature range close to its critical temperature. Our systematic study reveals that VO 2 thin films with just one layer 80 nm thick has the potential to develop completely different dynamic tuning of infrared radiation, enabling both black-body emission suppression and as well as mirror emissivity boosting, in the same single layer device. Understanding the dynamics and effects of thermal tuning on infrared emission will benefit wide range of infrared technologies including thermal emitters, sensors, active IR filters and detectors. The possibility to tune the spectral features of a device, triggered by a thermal, electrical or optical stimulation, paves the way for many applications such as perfect infrared absorbers 1-4 , smart intelligent window coatings 5,6 , thermal rectification devices 7 or diodes/rectifiers 8. Thermochromic materials, such as niobium dioxide (NbO 2), vanadium sesquioxide (V 2 O 3), and vanadium dioxide (VO 2) undergo an abrupt phase transition from semiconductor to metallic state at a specific phase transition temperature 9-11. This phase change transition, from insulating monoclinic phase into a metallic tetragonal (rutile) phase, is accompanied by drastic changes in electrical, optical and magnetic properties as a function of the temperature. Among them, VO 2 is widely employed since it pertains the lowest phase transition temperature, T c = 341 K (68 °C) 12. The strong and reproducible changes in optical properties due to phase transition, have generated a burgeoning amount of theoretical and experimental studies focusing on the thermal emissivity variation activated by temperature in VO 2 13,14 in the IR 15 and THz radiation ranges 16. The thermal hysteresis intrinsic to the phase transition has been widely investigated and was found to be affected by several factors such as the film deposition temperature 17 , the use of different substrates 18-20 , the wavelength range 21 , the introduction of metallic dopants 22 and the dimensions of metallic grains 23. In particular, if metallic grain size is smaller than the wavelength of excitation, diffraction effects result in enhanced transmitted signal. When temperature increases, the grain sizes of exp...

Metal–Insulator Transition Detection of Vanadium Dioxide Thin Films by Visible Light Reflection

“…The transition temperature setting of vanadium dioxide is usually controlled via impurity doping with lower- and higher-valence transition metals, such as W, Nb, Cr, Mo, and Ti. − However, to obtain highly effective thermochromic and electrochromic properties, a thin film of pure-phase VO 2 is required. For this purpose, various synthesis methods, such as strain-induced single-crystal substrates with the most preferred orientation, buffer layers, narrow oxygen partial pressures, and optimal growth temperatures, have already been studied. − More recently, VO 2 has been adopted as a next-generation material with dynamic color adjustment for reflectors or transmitters because of its significantly low phase change, low power consumption, low toxicity, low-effort manufacture, wide range of fabrication techniques, stability, and reversible electrically and optically activated tuning. − In particular, changes in optical properties, if induced in the visible spectral range, offer considerable benefits and ease of detection. Recently, photonic materials that are color-tunable in the visible spectral range, making them extremely attractive for application in temperature indicators, displays, memory, and other switchable optoelectronic devices, have been developed. − For example, Song et al reported, based on their modeling results, that vanadium dioxide-based metamaterial absorbers for active color rendering and multiband photodetection can be realized .…”

Tuning of Optical Phonons in α-MoO3–VO2 Multilayers

“…When the temperature applied to VO 2 increases beyond a critical point (T c ), insulator-to-metal transition (IMT) takes place, which renders its monoclinic (insulator) phase rutile (metallic). 10 While the microscopic dynamics of this intriguing phase transition for VO 2 remains elusive, 11 the experimental implementation of it in devices has been successful in the recent decade. The lower T c required for the IMT of VO 2 than that of other phase-change materials, 9,12 along with a variety of possible routes to achieve IMT (thermally, 13 electrically, 14 mechanically, 15 and optically 16,17 ), has provided ample opportunities to tailor the IMT of VO 2 to numerous applications.…”

“…18,19 The essence of optical modulation in the mentioned photonic applications is the IMT of VO 2 , which marks a sizeable change in the refractive index of this material. Some of the notable applications include optical diodes, 20 tunable metamaterials, 21−23 thermal emitters, 10,24 and infrared absorbers. 25 Marrying the tunability of VO 2 and the rich optical response of vdW materials through intricate designs, researchers have successfully demonstrated devices with tunable optical responses.…”

“…Since the first revelation of its dynamic phase-change properties in 1959, the interest in the active modulation properties of VO 2 has been thriving. When the temperature applied to VO 2 increases beyond a critical point ( T c ), insulator-to-metal transition (IMT) takes place, which renders its monoclinic (insulator) phase rutile (metallic) . While the microscopic dynamics of this intriguing phase transition for VO 2 remains elusive, the experimental implementation of it in devices has been successful in the recent decade.…”

“…The lower T c required for the IMT of VO 2 than that of other phase-change materials, , along with a variety of possible routes to achieve IMT (thermally, electrically, mechanically, and optically , ), has provided ample opportunities to tailor the IMT of VO 2 to numerous applications. , The essence of optical modulation in the mentioned photonic applications is the IMT of VO 2 , which marks a sizeable change in the refractive index of this material. Some of the notable applications include optical diodes, tunable metamaterials, − thermal emitters, , and infrared absorbers …”