Detailed pathway for a fast low-temperature synthesis of strongly thermochromic W-doped VO 2 films with a low transition temperature

We report the discharge characteristics, and population of chosen atomic neutral (V, O and Ar) and ionic (V + , V 2+ , O + and Ar + ) species in the discharge during low-temperature (350 °C) depositions of W-doped VO x films onto a 170 nm thick Y-stabilized ZrO 2 layer on a 1 mm thick conventional soda-lime glass. The depositions were performed using reactive deep oscillation magnetron sputtering with a pulsed O 2 flow control and to-substrate O 2 injection into a high-density plasma in front of the sputter V-W target. The pre-selected critical values of the oxygen partial pressure were in the range from 82 mPa to 92 mPa. Optical emission spectroscopy proved a relatively high density of O atoms in front of the substrate, which is important for production of the W-doped VO 2 films. It was found that setting of the amount of O 2 in the gas mixture determines not only the elemental and phase composition of the films and their deposition rate but also the crystallinity of the thermochromic VO 2 phase in them. The crystalline W-doped VO 2 films with a low transition temperature of 28 °C exhibited a high modulation of the solar energy transmittance of 8.9%. The results are important for further improvement of this new scalable sputter deposition technique for a fast (53 nm min −1 at a target-substrate distance of 100 mm in this work) low-temperature synthesis of high-performance durable thermochromic VO 2 -based multilayer coatings designed for smart-window applications.