Impact of nanostructural features of thermochromic VO2/TiO2 bilayers on their electrical and optical properties

• VO 2 /TiO 2 bilayer thin films were deposited on glass, quartz, and fused silica substrates. • Interface strain and TiO 2 phase influenced VO 2 crystallinity and phase transition. • Strain mapping confirmed local M2 phase stabilization in VO 2 films. • A clear trade-off between film thickness, transparency, and switching amplitude was observed. • Optimized VO 2 films balance high luminous transmittance and resistivity contrast for smart windows. VO 2 -based thermochromic thin films are promising for energy-efficient smart window applications due to their reversible metal–insulator transition near 68 °C. However, practical limitations such as high transition temperature, limited visible transmittance and substrate compatibility remain challenges. In this study, VO 2 /TiO 2 bilayer thin films were deposited via PLD on glass, fused silica, and quartz substrates to investigate the effect of buffer layer, film thickness, and strain on their structural, optical, and electrical properties. Comprehensive characterization using in situ grazing incidence X-ray diffraction, synchrotron GIXRD, and high-resolution Transmission Electron Microscopy revealed that TiO 2 buffer layers, in the anatase or brookite phase, significantly influences the growth orientation and strain distribution in VO 2 films. Residual strain mapping indicated up to 5 % compressive strain in VO 2 and >10 % tensile strain in the TiO 2 , promoting partial stabilization of the intermediate M2 phase. Thickness-dependent studies showed a strong trade-off between optical transmittance and electrical switching amplitude: thinner films exhibited higher luminous transmittance (up to 30 %) and sharper IR switching, while thicker films yielded larger resistivity switching contrast. These results demonstrate that interfacial strain, film thickness, and substrate choice are critical parameters for tailoring VO 2 -based coatings and optimizing thermochromic performance for scalable smart window technologies.