Microwave dielectric and nonlinear optical studies on radio‐frequency sputtered Dy ₂ O ₃ ‐doped <scp>KNN</scp> thin films

Abstract

Abstract We report the effect of oxygen mixing percentage ( OMP ) on structural, microstructural, dielectric, linear, and nonlinear optical properties of Dy 2 O 3 ‐doped (K 0.5 Na 0.5 )NbO 3 thin films. The (K 0.5 Na 0.5 )NbO 3 + 0.5 wt%Dy 2 O 3 ( KNN 05D) ferroelectric thin films were deposited on to quartz and Pt/Ti/SiO 2 /Si substrates by RF magnetron sputtering. An increase in the refractive index from 2.08 to 2.21 and a decrease in the optical bandgap from 4.30 to 4.28 eV indicate the improvement in crystallinity, which is also confirmed from Raman studies. A high relative permittivity (ε r =281‐332) and low loss tangent (tanδ=1.2%‐1.9%) were obtained for the films deposited in 100% OMP , measured at microwave frequencies (5‐15 GHz). The leakage current of the films found to be as low as 9.90×10 −9 A/cm 2 at 150 kV/cm and Poole‐Frenkel emission is the dominant conduction mechanism in the films. The third order nonlinear optical properties of the KNN 05D films were investigated using modified single beam z‐scan method. The third order nonlinear susceptibility (ǀχ (3) ǀ) values of KNN 05D films increased from 0.69×10 −3 esu to 1.40×10 −3 esu with an increase in OMP . The larger and positive nonlinear refractive index n 2 =7.04×10 −6 cm 2 /W, and nonlinear absorption coefficient β=1.70 cm/W were obtained for the 100% OMP film, indicating that KNN 05D films are good candidates for the applications in nonlinear photonics and high‐frequency devices.