Properties of thermochromic VO2 films prepared by HiPIMS onto unbiased amorphous glass substrates at a low temperature of 300 °C

Abstract The paper deals with thermochromic VO2 films deposited by reactive high-power impulse magnetron sputtering with a pulsed reactive gas flow control under exceptionally industry-friendly conditions: onto amorphous glass substrates without any interlayer, without any substrate bias voltage and at low temperatures (Tdep) down to 300 °C. We show that (and how) strongly thermochromic VO2 films can be prepared even under these unfavorable conditions, and compare their properties with those achieved under more favorable but less industry-friendly conditions. We focus on the film structure studied by X-ray diffraction and Raman spectroscopy, electrical resistivity, and especially optical properties studied by spectroscopic ellipsometry and spectrophotometry. The properties achieved at Tdep = 300 °C include e.g. transition temperature (Ttr) below 60 °C, extinction coefficient at 550 nm of around 0.50, modulation of the extinction coefficient at 2000 nm between 0.35 (room temperature) and 3.77 (above Ttr) or modulation of the resistivity between 5.3 × 10−3 Ωm (room temperature) and 1.5 × 10−5 m (above Ttr). The results are important for the design of pathways for the preparation of thermochromic coatings under industry-friendly conditions, and, in turn, significantly increase the application potential of these coatings.