Structural, optical and dielectric properties of Yttrium (Y) doped MgO thin films fabricated by water based solution processing

This paper establishes the high performance of an ecological water-based solution processing in creating Magnesium oxide (MgO) thin films with various doping levels of Yttrium (Y) (0, 05, 10, and 15 atomic %), on ITO glass substrates. No mixed and secondary phases have been observed by XRD patterns revealing an amorphous nature in all the films. From FTIR, the characteristic peaks of oxides have been found with no significant traces of impurities while EDX analysis has confirmed the elemental signatures of Mg, O, and Y in the deposited films. The SEM images have shown a change in the surface morphology from smooth to inhomogeneous filament type grains having voids in the surface as the Y doping level is increased. The transmittance is increased, while the optical band gap is decreased from 4.00 to 3.75 eV. The refractive index and extinction coefficient are found improved as compared to pristine MgO film. The red luminescence band excited in MgO is observed around 700 nm. All the films exhibit ohmic conduction with resistivity decrease by an order of magnitude (∼10³ Ωcm) as the Y content increases. Strong dependence of the dielectric constant (real and imaginary), tangent loss, impedance and electric modulus on both the frequency and dopant has been observed. The spectra are well referred to the Maxwell-Wagner type of polarization of Koop’s theory. The analysis further leads to the predominant contribution of grain boundaries and a non-Debye relaxation phenomenon. The films are found suitable for low frequency electronic applications.