The Application Of Atomic Layer Deposition Technology In Dielectric Energy Storage Devices

Dielectric energy storage capacitors are widely used in electronic devices for pulse discharge and power regulation because they have an extremely fast charge/discharge rate.Among them,energy storage capacitors with thin film materials as the dielectric layer are very conducive to the miniaturization and integration of electronic devices.However,compared with other energy storage devices such as electrochemical supercapacitors and batteries,the dielectric capacitors currently have a relatively low energy density.Therefore,it is necessary to study the main factors affecting the performance of dielectric energy storage devices so as to improve the device structure and preparation process.Atomic layer deposition(ALD),as a thin film deposition method based on self-limiting saturation adsorption,can simply realize atomic-scale thickness control and component adjustment by altering the number of deposition cycles.What's more,the atomic-layer-deposited film has excellent substrate conformality.In this paper,ALD technology was used as the main film preparation method.In order to improve the energy storage performance of dielectric thin film capacitors,studies have been carried out and results have been achieved in the following aspects:(1)The influence of different thickness and number of inserted ultra-thin Al₂O₃layers on the dielectric properties and the energy storage performance of the Ba(Zr_0.2Ti_0.8)O₃(BZT)film was found,providing a feasible scheme to improve energy storage characteristics of ferroelectric thin film capacitors.By using ALD technology,ultra-thin Al₂O₃ intercalations of different thickness and different number of layers were introduced into the BZT relaxation ferroelectric films prepared by sol-gel method.The phase structure,micromorphology,dielectric properties and energy storage performance of the BZT-Al₂O₃ composite films were studied.The results show that when the thickness of single Al₂O₃ layer exceeds the threshold thickness(0.45?0.9nm),the leakage current of composite films can be effectively suppressed and the voltage endurance capability of composite films can be greatly improved compared with the pure BZT film.At the same time,the voltage endurance capability of the film can be further enhanced by increasing the number of Al₂O₃ layers.Due to the improvement of electrical performance,BZT-Al₂O₃ composite film capacitors showed significantly improved energy storage efficiency and achieved higher energy storage density under higher electric field.The research shows that the introduction of ultrathin,highly insulated intercalations with controllable thickness into ferroelectric films by ALD technology is an effective way to reduce the leakage current and enhance the voltage endurance capability,so as to improve the energy storage performance of ferroelectric-based capacitors.(2)The atomic layer deposition preparation of Bi-Al₂O₃ composite films was realized.The influence of Bi metal particles on the dielectric property and energy storage performance of Al₂O₃ film as well as the mechanism involved was revealed,proposing a method to improve the energy storage performance of linear dielectric film capacitors.Different content of Bi particles were introduced into Al₂O₃ films by ALD method.The component content,microstructure,micromorphology,dielectric properties and energy storage performance of Bi-Al₂O₃ composite films were investigated.The results show that the Bi-Al₂O₃ composite film forms a microstructure with Bi element nanocrystalline region embedded in the amorphous Al₂O₃ matrix.Based on the Maxwell-Wagner effect of the interface between Bi metal particles and Al₂O₃ matrix,the dielectric constant of composite films is effectively improved.In addition,due to the amorphous matrix and low content of Bi,composite films can still maintain low DC leakage current.Compared with the pure Al₂O₃ film,Bi-Al₂O₃composite films exhibit higher energy storage density under the same electric field and maintain a high energy storage efficiency in the range of electric field below 8 MV/cm.Among them,the sample with a Bi/(Bi+Al)atomic ratio of 0.28 shows optimum energy storage performance which achieves energy storage density of up to 67 J/cm³ and energy storage efficiency of about 80%under the external electric field of 10.5 MV/cm.The study shows that the introduction of Bi particles can effectively improve the energy storage performance of Al₂O₃ films.The introduction of metal particles in linear dielectric matrix by ALD technology is an effective method to improve the dielectric constant and thus the energy storage performance of devices.