Structural, optical, dielectric and electrical studies on RF sputtered nanocrystalline Zr doped MgTiO3 thin films

Mg(Zr0.05Ti0.95)O3 (MZT) thin films have been deposited onto amorphous SiO2 and platinized silicon (Pt/TiO2/SiO2/Si) substrates by RF magnetron sputtering at different oxygen mixing percentages (OMP). The effect of OMP and post annealing temperature at 600 °C on crystal orientation, surface morphology, optical, electrical and dielectric properties of crystallined MZT films are investigated. A change of preferred orientation from (1 0 4) to (1 1 0) has been observed with increasing OMP from 0% to 100%. The preferred orientation growth has been explained on the basis of Lotgering model by calculating the orientation factor. The optical properties such as refractive index and bandgap were strongly influenced with O2 content. It is also observed that the refractive index and packing density decreases with increasing OMP, leading to an enhancement in the optical bandgap from 4.19 to 4.52 eV. The dielectric constant and dielectric loss of the films ranged between 5.0-15.69 and 0.082-0.0135. The MZT thin films deposited at 100% OMP exhibited the high dielectric constant and low loss tangent. Further, the DC conductivity with frequency follows Jonscher law and the activation energy found to be 0.32 eV for MZT films deposited in pure oxygen atmosphere. Nyquist plots of MZT films revealed two semi circular arcs and are explained on the basis of equivalent circuit model. A series of two parallel RC combination in series fit with experimental data. The I-V characteristics reveals that the leakage current density decreases from 1.136 × 10−8 to 4.69 × 10−9 A/cm2 for OMP, 0-100%, respectively for electric field strength of 200 kV/cm.