Dielectric dynamics of the polycrystalline Ba_0.5Sr_0.5TiO₃ thin films

¹ Jožef Stefan Institute - Jamova cesta 39, SI-1000 Ljubljana, Slovenia
² Jožef Stefan International Postgraduate School - Jamova cesta 39, SI-1000 Ljubljana, Slovenia
³ Faculty of Physics, Vilnius University - 10222 Vilnius, Lithuania
⁴ School of Electronic and Information Engineering, Xi'an Jiaotong University - 28 XianNing West, Xi'an 710049, China
⁵ CEA Grenoble, LETI, Minatec Campus - 17 Rue des Martyrs, F-38054 Grenoble, France

^(a) Present address: IPDiA - 2 Rue de la Girafe, F-14000 Caen, France; sebastjan.glinsek@ijs.si

Received: 17 March 2016
Accepted: 27 May 2016

Abstract

Polycrystalline Ba_0.5Sr_0.5TiO₃ films, with thicknesses between 90 and 600 nm, were prepared on alumina substrates at 900 °C by chemical solution deposition (CSD) and a dielectric spectroscopy investigation of the in-plane properties was performed. The 5-kHz permittivity ε′ shows a non-monotonic thickness dependence, reaching 1230 at room temperature for the 310-nm-thick film, whose grain size is ∼75 nm. Its 15-GHz-value and losses are 1105 and 0.05, respectively. The temperature of the permittivity maximum T_max at 5 kHz decreases with increasing thickness from 277 to 250 K for the 170- and 600-nm-thick films, respectively, which has been linked to the residual biaxial stress. A hysteresis is observed in the permittivity ε′-electric field E_DC characteristics in all the films up to ∼50 K above T_max. Frequency dispersion in which permittivity decreases with increasing frequency is present below T_max in films thicker than 90 nm. The high permittivity values of the thinnest films, which are among the highest reported in the (Ba,Sr)TiO₃ films with grain sizes below 75 nm, are a direct proof of the optimized CSD processing conditions.