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February

Picture of the Month - February 2026

Influence of post-growth temperature treatment on surface structure of ion-beam sputtered vanadium oxide

Thermochromic smart windows dynamically regulate optical transmittance in response to temperature, offering a promising approach to reducing building energy consumption. Vanadium dioxide (VO₂) is a leading thermochromic material due to its sharp insulator-to-metal transition and strong modulation of infrared (IR) transmittance. While VO₂ formation typically requires high substrate temperatures during deposition, post-deposition annealing provides a more practical and scalable route, enabling lower growth temperatures and controlled modification of surface morphology.

In this work, VOₓ thin films are deposited by ion-beam sputter deposition (IBSD) and systematically annealed to obtain phase-pure VO₂. We show that film morphology and phase evolution are strongly influenced by annealing temperature, film thickness, and annealing conditions, demonstrating post-growth annealing as an effective strategy for optimizing thermochromic vanadium oxide films for smart window applications.

The picture shows a schematic illustration of the post-growth annealing strategy for tailoring VO₂ thin films. A furnace represents the annealing process and phase formation within the vanadium oxide system, while control knobs denote key parameters — atmosphere, temperature, time, and pressure — that govern phase evolution and microstructural development. The schematically depicted range of surface morphologies highlights the structural tunability enabled by controlled post-deposition annealing, emphasizing its effectiveness for optimizing thermochromic VO₂ thin films.

Note: This work is submitted to JVST A Special Collection: Phase Change Materials: Fundamentals, Innovations, and Applications.

This picture was submitted by Dr. Martin Becker (group of Prof. Dr. Peter J. Klar).

Further insights into the research activities of the ZfM groups can be found in the Gallery.