Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 88: GHz Dielectrics - Materials for mobile communication II (DF with DY/HL/MM)

HL 88.3: Talk

Thursday, March 19, 2015, 15:50–16:10, EB 407

Microwave electric properties of thin-film Ba_xSr_1−xTiO₃ varactors with highly-conducting epitaxial SrMoO₃ oxide electrodes — •Arzhang Mani¹, Aldin Radetinac¹, Mohammad Nikfalazar², Sergiy Melnyk², Philipp Komissinskiy¹, Yuliang Zheng², Rolf Jakoby², and Lambert Alff¹ — ¹Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Deutschland — ²Institut für Mikrowellentechnik und Photonik, Technische Universität Darmstadt, 64283 Darmstadt, Deutschland

We present high-frequency properties of MIM thin-film varactors with dielectric Ba_xSr_1−xTiO₃ (x=0.4, 0.5, 0.6). Single crystalline Ba_xSr_1−xTiO₃ layers were grown epitaxially on highly-conducting oxide SrMoO₃ electrodes with room-temperature resistivity of 30 µΩ· cm. Au/Pt top electrodes were deposited by magnetron sputtering on top of the Ba_xSr_1−xTiO₃ / SrMoO₃ heterostructures and patterned with photolithography and lift-off. Influence of Ba content (x), thickness of Ba_xSr_1−xTiO₃ layer, and size of the top electrodes on performance of the varactors were investigated in the frequency range of 100 MHz to 10 GHz. Capacitance of 15 pF, quality factor of 15, and tunability of 40% at 0.3 MV/cm were obtained at 100 MHz. The obtained results suggest a high potential of the oxide perovskite electrode material SrMoO₃ [1] for fabrication of highly tunable varactors in microwave applications.

[1] A. Radetinac et al., Appl. Phys. Lett. 105, 114108 (2014).