Concept and system aspects of MEMS magnetically tunable THz-filters based on metasurfaces

Inhalt:
In this work, we present the concept and system aspects of magnetically tunable MEMS THz-filters using so-called metasurfaces (MS). As possible MS-designs for electromagnetically tunable MEMS-filters, two different designs of Split ring resonators (SRR) are investigated in which cantilever arms coated with a magnetic thin-film layer interact strongly with an external magnetic field (H). The THz-frequency response of geometrically varying SRR structures with a con-ductive-magnetic bilayer are simulated and show a tunability of 51 GHz, i.e., 8%. As first experimental studies, different techniques for magnetic layers are investigated: commercial magnetic spray, sputtering nickel (Ni) and sputtering permalloy (Ni80Fe20 or py). They are deposited on aluminium coated silicon cantilevers. The fabricated films are characterised in terms of thickness, surface homogeneity, intrinsic layer stress and qualitative magnetic testing. In comparison to the spray coated and nickel samples, py films deflect in an external (H) already at the smallest thickness of 114 nm. The stress induced deformation of py coated beams is smaller than of Ni coated beams. Additionally, no crack formation has been observed in py coatings compared to the prior coatings. However, a columnar grain growth is observed for 0.5 µm thick py-films.