Regensburg 2016 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 6: Focus Session: Applications of Dielectric Materials in Microwave Technology

DF 6.7: Vortrag

Montag, 7. März 2016, 18:00–18:20, H26

Stoichiometry effect on microwave properties of all-oxide BST thin film varactors — •Patrick Salg¹, Arzhang Mani¹, Mohammad Nikfalazar², Aldin Radetinac¹, Rolf Jacoby², Lambert Alff¹, and Philipp Komissinskiy¹ — ¹Institute of Materials Science, TU Darmstadt, Germany — ²Institute for Microwave Engineering and Photonics, TU Darmstadt, Germany

We present all-oxide ferroelectric varactors using a bottom electrode of the highly conducting perovskite SrMoO₃ [1]. Thin-film epitaxial heterostructures of SrMoO₃ with a room-temperature resistivity of 30 µΩcm and the functional tunable dielectric Ba_xSr_1−xTiO₃ with (x = 0.2 − 0.6) were grown by pulsed laser deposition. As top electrode, sputtered amorphous Au/Pt layers were used and patterned by lift-off. The effect of stoichiometry of the Ba_xSr_1−xTiO₃ layer on the microwave properties of the varactors was investigated at frequencies up to 10 GHz at room temperature. A zero-bias quality factor of the varactors with Ba_0.4Sr_0.6TiO₃ of 110 at 1 GHz and 20 at 10 GHz was achieved. These values are more than 10 times higher than the ones previously reported in the literature for varactors with other oxide electrodes. The capacitance tunability of the varactors is above 50% at 8 V and stable in a broad frequency range from 100 MHz up to 10 GHz. The obtained results suggest a high potential of all-oxide ferroelectric varactors for microwave applications.

[1] A. Radetinac et al., Highly conducting SrMoO₃ thin films for microwave applications, Appl. Phys. Lett. 105, 114108 (2014).