Investigation on preparation and electric field tunable dielectric properties of novel bismuth magnesium niobate transparent capacitors for opto-electronic devices

Transparent capacitors, based on bismuth magnesium niobate (Bi_1.5MgNb_1.5O₇, BMN), have been fabricated on indium tin oxide glass substrates by rf magnetron sputtering. The effect of post-annealing conditions on structural, electrical, and optical properties of BMN thin films was investigated. X-ray diffraction patterns and scanning electron microscopy reveal that the BMN thin films post-annealed at an oxygen partial pressure of 0.1 MPa have the best crystalline quality compared to BMN films post-annealed under all other conditions. The BMN thin films exhibit an average transmittance of 85% in the visible light range (380–780 nm), while the value of optical absorption edge is 3.59 eV. Dielectric measurements indicate that the thin films exhibit a medium dielectric constant of about 99, a low loss tangent of 0.0037, and superior tunable dielectric properties at room temperature. Calculations of dielectric tunability and the figure of merit (FOM) display a maximum value of 28% at 1.3 MV cm⁻¹ and ∼57, respectively. The results show that BMN thin films have great potential for use in electric field tunable transparent capacitors.