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DS: Fachverband Dünne Schichten

DS 22: Thin Film Applications

DS 22.8: Vortrag

Donnerstag, 4. April 2019, 11:30–11:45, H39

Microfabricated switchable THz flat lenses made out of VO₂ thin films — •Florian Kuhl¹, Angelika Polity¹, Yan Zhang², and Peter J. Klar¹ — ¹Institute of Experimental Physics I and Center for Materials Research (ZfM/LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, DE-35392 Giessen, Germany — ²Beijing Key Lab for Metamaterials and Devices, Capital Normal University, Beijing, China

Terahertz radiation and its various applications have gained a lot of interest in the last few years and, thus, the importance of switchable THz devices has increased. Thermochromic VO₂ shows a semiconductor to metal transition and hence is a suitable material for designing thermally switchable structures.
We present microfabricated resonator structures in rf-magnetron sputtered VO₂ thin films. It is necessary to choose the type of substrate and to optimize the properties of the buffer layer and the thin film. The resonator structures were transfered into the thin films via photo-lithography and ion-beam etching. Measurements on unstructured thin films of VO₂ show the typical switching behaviour in the infrared region and typical switching temperatures for thin films of about 55 ^∘C. The switching behaviour of structured thin films was investigated with terahertz time-domain spectroscopy (THz-TDS) at low and high temperatures to demonstrate the two desired operating modes of the designed structures. While no effect on incoming radiation could be observed at low temperatures, a focussing behaviour was detected at higher temperatures when the VO₂ micro resonators become metallic.