Dresden 2017 – scientific programme

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KR: Fachgruppe Kristallographie

KR 1: Various Topics I (with DF)

KR 1.6: Talk

Monday, March 20, 2017, 11:30–11:50, GER 37

Interface engineering in all-oxide Ba_xSr_1−xTiO₃ thin-film varactors with highly conducting SrMoO₃ electrodes — •Patrick Salg¹, Aldin Radetinac¹, Dominik Walk², Holger Maune², Rolf Jacoby², Philipp Komissinskiy¹, and Lambert Alff¹ — ¹Institute of Materials Science, TU Darmstadt, Germany — ²Institute for Microwave Engineering and Photonics, TU Darmstadt, Germany

We present epitaxial varactor heterostructures utilizing highly conducting oxide SrMoO₃ bottom electrodes with a room-temperature resistivity of 30 µΩcm [1] grown by pulsed laser deposition using SrMoO₄ targets. During thin film synthesis, highly reductive conditions are essential to achieve a Mo⁴⁺ state in the SrMoO₃ thin film. In contrast to the growth conditions of SrMoO₃, the growth of Ba_xSr_1−xTiO₃ films requires a high oxygen partial pressure of 1.5 mTorr. In order to prevent oxidation of the underlying SrMoO₃ layers during growth of Ba_xSr_1−xTiO₃, a SrTiO₃ layer was grown between SrMoO₃ and Ba_xSr_1−xTiO₃. The effectivity of this SrTiO₃ interlayer as an oxygen diffusion barrier was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The use of a SrTiO₃ interlayer allows a successful epitaxial growth of varactor heterostructures with high electric tunability of up to 80 % and low losses at microwave frequencies.

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