Berlin 2024 – scientific programme

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DS: Fachverband Dünne Schichten

DS 6: Thin Film Properties I

DS 6.5: Talk

Tuesday, March 19, 2024, 11:00–11:15, A 060

Anatase-to-Rutile transformation in CuTiO₂ alloys — •Hao Lu^1,2, Martin Becker^1,2, Jan Luka Dornseifer^1,2, and Peter J. Klar^1,2 — ¹Institute of Experimental Physics I, Justus-Liebig-University, Giessen, Germany — ²Heinrich-Buff-Ring

Alloying the TiO₂ with CuO₂ yielding Cu_xTi_1−xO₂ may provide a suitable buffer layer for optical smart windows based on VO₂. We successfully grew polycrystalline Cu_xTi_1−xO₂ alloys with x up to 31% on float glass and quartz substrates by conventional rf-sputtering employing a TiO₂ ceramic target and Cu wires as Cu source. The surface morphology was measured by SEM. Systematic variations in film morphology were observed concomitant with alterations in the Cu content. We determined the crystal phase of the deposited thin films by XRD and Raman spectroscopy and established a 2D phase map versus substrate temperature during growth and Cu content x. It shows that increasing Cu content considerably lowers the growth temperature where rutile Cu_xTi_1−xO₂ thin films can be obtained. For x = 23.5%, the minimum growth temperature for the rutile phase still can be as low as 200 ^∘C. Transmission spectroscopy and ellipsometry reveal that the band gap of the Cu_xTi_1−xO₂ decreases with increasing x. Furthermore, we find that the morphology of the Cu_xTi_1−xO₂ thin films changes with increasing x. Currently, we are assessing the trade-off between band gap, morphology, and growth temperature required for obtaining the most suitable rutile Cu_xTi_1−xO₂ buffer layer from the viewpoints of the best materials properties as well as a suitability for future commercialization in smart windows.