Microstructure, dielectric and optical properties of transparent flexible high-k Bi1.5MgNb1.5O7 thin films

Abstract

High-k insulation materials can effectively reduce the operating voltage and leakage current of TFT devices, improving device performance owing to their high dielectric constant and insulation properties. Transparent flexible Bi1.5MgNb1.5O7 (BMN) dielectric thin films were synthesized via RF magnetron sputtering at room temperature. The impact of argon to oxygen ratio (Ar:O2) on the microstructure, elemental composition, optical, and dielectric properties of the BMN dielectric films was systematically explored. X-ray photoelectron spectroscopy, scanning electron microscopy, and optical property tests revealed that the proportion of metallic Bi and grain size play crucial roles in the optical transmittance and optical bandgap of the BMN films. Moreover, the dielectric properties were significantly influenced by the space charge polarization resulting from the percolation capacitance model formed by metallic Bi in the samples. To further optimize the dielectric properties of BMN films, sandwich structured OAO (BMNO/BMNAr/BMNO) composite films were designed. The OAO composite film exhibited the best overall performance, with an average transmittance of 92.27 %, a dielectric constant of 84, a dielectric loss of 0.00672, and a leakage current density of approximately 1.4 × 10−8 (5 V) when the thickness of the BMNO layer was 15 nm. These results highlight the significant potential of BMN as a transparent flexible high-k dielectric material.