Structural, Optical, and Dielectric Properties of Ion-Conducting LiAlO2 Thin Films Produced by Reactive Magnetron Co-sputtering

This study reports on the properties of LiAlO2 thin films compared to Al2O3 and Li2O thin films, considering their application as an ion-conducting dielectric in metal–insulator–metal (MIM) capacitors. The reactive magnetron co-sputtering method for the deposition of LiAlO2 is presented for the first time. This room-temperature method dedicates an amorphous LiAlO2 film with a smooth surface (R rms ∼ 0.34 nm) and uniform morphology, which was determined by X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques. UV–vis spectroscopy points to the formation of LiAlO2 with high transparency and a wide band gap. The fabricated MIM capacitors were analyzed using impedance spectroscopy to determine the cross-plane conductivity and dielectric properties. Incorporation of lithium ions into the alumina results in an ionic conduction mechanism with a room-temperature conductivity of 2.23 × 10–11 S cm–1 and activation energy of 0.69 eV consistent with the Arrhenius relation. The capacitance–frequency study for LiAlO2-based capacitors shows a stabilized behavior with a capacitance of 123.51 nF/cm2. The enhancement in the dielectric constant (k ∼ 25.76) coupled with a high band gap energy (E g ∼ 5.49 eV) is determined. These results suggest the production of thin film capacitors with better energy storage performance and lower loss by using an ion-conducting dielectric.