Effects of additive elements on improvement of the dielectric properties of Ta2O5 films formed by metalorganic decomposition

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Abstract
Ta 2 O 5 -based composite thin films formed by metalorganic decomposition have been investigated with respect to their dielectric properties. The dielectric and insulating properties of composite (1−x) Ta 2 O 5 −x TiO 2 and (1−x) Ta 2 O 5 −x WO 3 thin films are found to be improved compared to those of pure Ta 2 O 5 thin films. In particular, thin films with x=0.08 composition of additive TiO 2 or WO 3 to Ta 2 O 5 exhibited superior dielectric and insulating properties. The maximum dielectric constant and charge storage density of composite films are about 20 and 53.6 fC /μ m 2 , respectively, higher than those of pure Ta 2 O 5 films (about 13 and 34.5 fC /μ m 2 ). The temperature coefficient of the dielectric constant of composite films dramatically decreases from 65 ppm/°C for pure Ta 2 O 5 to less than 11 ppm/°C. The leakage current density of composite films is lower than 1×10 −9 A / cm 2 up to an applied electric field of 3 MV/cm. The dominant conduction is Poole–Frenkel conduction in the films according to the measurementtemperature dependence of the I−V characteristics.