Stoichiometry-controlled growth of BaxSr1−xTiO3 thin films and their electrical behavior in heterojunction assemblies

Abstract

We describe an optimized chemical synthesis route to obtain Ba_xSr_1−xTiO₃ (x = 0, 0.50, 0.67, 1.0) thin films with impeccable stoichiometry control. The molar ratios of the precursors were altered to produce the cubic phase of SrTiO_3, Ba_0.5Sr_0.5TiO₃, Ba_0.67Sr_0.33TiO₃ and the tetragonal phase of BaTiO₃ thin films on single crystalline p-Si (100) and quartz substrates. The obtained Raman spectra for the Ba_xSr_1−xTiO₃ thin films on quartz substrates showed characteristic vibration modes at ∼303, 515 and 716 cm⁻¹. The active modes of BaTiO₃ signify the tetragonal phase, which is important for its various technological advantages. The significant features of these materials were obtained through capacitance–voltage (C–V) measurements with Pt (or Ag)/Ba_xSr_1−xTiO₃/p-Si/Pt (or Ag) assemblies, at 1, 10 and 100 kHz. Substantial hysteresis (ΔV) of 315 mV (with Ag) and 219 mV (with Pt) was observed for Ba_0.5Sr_0.5TiO₃, whereas for BaTiO₃ and SrTiO₃ the obtained hysteresis was 256 mV and 96 mV, respectively. The largest hysteresis of 793 mV was observed for SrTiO₃ with a Pt electrode. The above findings are important for assessing the device compatibility of cost efficient solution processed Ba_xSr_1−xTiO₃ thin films.