Structural and optical properties of RF-sputtered ZnFe₂O₄thin films

Abstract

Thin films of zinc ferrite (ZnFe2O4) were deposited on glass substrates at room temperature in pure argon and pure oxygen environments by RF-magnetron sputtering. The structural and optical properties of the films were studied as a function of pure O2 pressure using an RF power of 100 W. The XRD data show the film having a spinel structure. The AFM images show the nanocrystalline nature of the films. The particle size depends on the environment and varies between 55 and 75 nm. The smaller value is obtained for the film deposited under the pure argon environment. The optical constants of the films were extracted from the transmission spectra by the envelope method. The estimated direct energy band gap values for the film deposited at 8 mTorr of gas pressure in pure Ar is 2.43 eV. For the films deposited in pure O2, the band gap increases from 2.48 to 2.61 eV as the O2 pressure is increased from 8 to 31 mTorr. The dispersion of the refractive index (n) is discussed in terms of the single-oscillator Wemple–DiDomenico model. This model is also used to estimate the dispersion parameters and the static refractive index.