Electrical and dielectric behavior of MgO doped Ba 0.7Sr0.3TiO 3 thin films on Al2 O3 substrate

Abstract

In this letter, we present the results of the fabrication and characterization of 5 mol % MgO doped ${\mathrm{Ba}}_{\text{0.7}}{\mathrm{Sr}}_{\text{0.3}}{\mathrm{TiO}}_3$ (BST) films grown on $\mathrm{Pt}/\mathrm{TiN}/{\mathrm{SiO}}_2$ coated on ${\mathrm{Al}}_2{\mathrm{O}}_3$ substrates using the rf magnetron sputtering technique. The dielectric and electrical properties of ${\mathrm{Ba}}_{\text{0.7}}{\mathrm{Sr}}_{\text{0.3}}{\mathrm{TiO}}_3$ thin film were found to improve obviously by means of MgO doping. The leakage current density of BST thin film decreased about 1 order of magnitude on MgO doping, while BST film with MgO doping had a higher dielectric constant than that without MgO doping. The dielectric constant of the films increased with increasing annealing temperature due to the consistent increase in grain size and crystallinity. The 750 °C annealed, 100 nm thick film indicated a high dielectric constant of 440 at 100 kHz and the lattice constant of 3.986 Å. The improvement of the electrical properties of BST films was associated with the reduced oxygen vacancies due to improved oxygenation of BST films in the presence of MgO. The MgO doped BST films exhibited a high tunability of 25% and dc resistivity of ${\text{6×10}}^{10}\mathrm{\hspace{0.17em}\Omega }\mathrm{cm}$ at an applied electric field of 200 kV/cm. The time-dependent dielectric breakdown studies indicated that the films had a longer lifetime of over 10 yrs on operation at the electric field of 0.4 MV/cm which is better than undoped BST film.