We studied the microstructure and dielectric properties of Ba0.5Sr0.5TiO3 thin films on polycrystalline alumina substrates with film thicknesses in the range 90–400 nm. Upon annealing at 900 °C the films crystallized in a pure perovskite phase with uniform and dense microstructures consisting predominantly of columnar grains. The dielectric permittivity in kHz and GHz ranges and tunability exhibited a nonlinear dependence on the film thickness, reaching the peak values at about 240 nm, which was explained by the dielectric grain-size effect for the thinner films and release of biaxial stress by formation of nanocracks for the thicker films.
COBISS.SI-ID: 28751655
The influence of neutron and gamma-ray irradiation on the kilohertz- and microwave-range dielectric properties of Ba0.5Sr0.5TiO3 thin films was also investigated. We observed that microstructural features, such as grain boundaries, pores and microcracks, as well as crystal-lattice defects have an effect on the irradiation-damage accumulation rate, and we concluded that the microstructure of the pristine films is decisive for the irradiation hardness of ferroelectric thin films used for microwave applications.
COBISS.SI-ID: 28378407
We presented a simulation analysis for coplanar-plate capacitors made on ferroelectric thin films. Simulations were performed with the help of commercially available Maxwell’s equation solvers based on the most commonly used numerical methods. The modelled values of capacitance were compared to the experimental results obtained on Ba0.5Sr0.5TiO3 films with thicknesses in the 100-nm range on alumina substrates in the kHz- and GHz-frequency ranges. Problems that are specific to each method were described, and optimized approaches for the simulation of structures made on thin films presented.
COBISS.SI-ID: 28402983