G. Savorianakis1, K. Mita2, T. Shimizu3, S. Konstantinidis1, M. Voué4, B. Maes5

1) Plasma-Surface Interaction Chemistry (ChIPS), Research Institute for Materials. Science and Engineering, University of Mons, 20 Place du Parc, Mons B-7000, Belgium
2) Materials Physics Design Research Section, Applied Physics Research Laboratory, Technical Development Group, Kobe Steel, LTD. 1-5-5, Takatsukadai, Nishi-ku, Kobe, Hyogo 651-2271, Japan
3) Department of Mechanical System Engineering, Tokyo Metropolitan University, 6-6 Asahigaoka, Hinoshi, Tokyo 191-0065, Japan
4) Physics of Materials and Optics (LPMO), Research Institute for Materials Science and Engineering, University of Mons, 20 Place du Parc, Mons B-7000, Belgium
5) Micro- and Nanophotonic Materials Group (MMNP), Research Institute for Materials Science and Engineering, University of Mons, 20 Place du Parc, Mons B-7000, Belgium

This work presents a structuration strategy to achieve high luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of vanadium dioxide (VO2) thermochromic thin films. We validate that optical properties of VO2 monoclinic films synthesized by reactive magnetron sputtering show a good agreement with the computational results. Then, the numerical simulation on ordered VO2 nanoribbons demonstrates an increased transmittance due to the vertical apertures, leading to a variety of photonic phenomena. A series of optimisations by varying the column width, period and film thickness determines that 20 nm wide nanoribbons separated by 10 nm for a film thickness of 250 nm reaches a Tlum of 47.6% and a ΔTsol of 14.2%. So, the transparency (related to Tlum) is significantly improved, in contrast to a dense film without nanostructuration, while ΔTsol remains unaffected. In addition, the resulting colour is less opaque, thus the strategy could be beneficial for thermochromic applications, such as smart windows.