Enhanced dielectric properties in bismuth-doped alumina films prepared by atomic layer deposition

• Bismuth-doped alumina thin films are fabricated by atomic layer deposition method.
• The permittivity increases with the bismuth concentration in the doped alumina films.
• An analysis method based on the complex impedance spectroscopy is proposed.
• The universal dielectric response in the films is affected by the bismuth doping.

Amorphous bismuth-doped Al2O3 thin films have been fabricated by atomic layer deposition method. The dielectric constant of the samples increases with the concentration of bismuth. Detailed electric processes are discussed based on the impedance spectroscopy and equivalent circuit model. It is found that the universal dielectric response (UDR) is ubiquitous in amorphous Al2O3. The dimensionality of the conduction space associated with the UDR process is not affected by the bismuth doping, but the alternating current conductivity associated with the UDR process increases with the bismuth concentration. The enhancement of dielectric properties is attributed to the 6s lone pair electrons of bismuth. The result of capacitance vs. voltage measurement demonstrates that the bismuth-doped Al2O3 film is suitable for the insulation layer in metal-oxide-semiconductor structure.