Structure, morphology, and dielectric properties of nanocomposite oxide films fo

2020-02-02 14:20:51

The dielectric films oxide Tantalum

责任者: Mozalev, A.;Sakairi, M.;Takahashi, H. 单位: Graduate Sch. of Eng., Hokkaido Univ., Sapporo, Japan 来源出处: Journal of the Electrochemical Society(J. Electrochem. Soc. (USA)),2004/11/,151(11):257-68 摘要: Anodizing of Ta-Al bilayers (aluminum deposited on tantalum) was performed in 0.2 M H2C2O4 solution to transform the aluminum metal into its nanoporous oxide followed by pore widening and reanodizing to different voltages in the range of 100-600 V. The anodic films consist of an upper layer of nano-sized tantala columns penetrating into the pores and a lower layer of continuous tantalum oxide under the porous alumina film. The columns are mainly composed of tantalum pentoxide and tantalum sub-oxides TaO2, Ta2O3, and TaO while the lower film layer is tantalum monoxide. At the boundary between the columns and alumina cells, a region of mixed (composite) Ta2O5 and Al2O3 is formed due to channeling of the ionic current through the outer part of the alumina cell walls. The relationship between the layers and the ionic transport during oxide growth depend on pore size and formation voltage. The dielectric properties of the anodic films are close to those of an ideal capacitor. Voltage-independent apparent dielectric constant of 12.6 was determined for the films formed by normal reanodizing. The relatively higher dielectric constant for the films formed by reanodizing through the widened pores rises from 17.6 to 24.0 in the voltage range of 270-400 V, which is due to the change in morphology, relative amount and chemical composition of anodic tantala in the complex film structure. The nanocomposite anodic films can be used as dielectrics for high-voltage low-leakage current electrolytic capacitors 关键词: aluminium;aluminium compounds;anodisation;dielectric thin films;interface structure;ionic conductivity;nanocomposites;permittivity;surface morphology;tantalum;tantalum compounds;X-ray chemical analysis;dielectric properties;nanocomposite oxide films;anodizing;surface morphology;TaAl bilayers;H2C2O4 solution;aluminum metal;nanoporous oxide;pore widening;anodic films;nano sized tantala columns;Ta2O3 layer;alumina cell walls;ionic current;ionic transport;complex film structure;chemical composition;leakage current electrolytic capacitors;sputter deposition;dielectric constant;100 to 600 V;Ta2O5-Al2O3;Ta-Al