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)Ta2O5−xTiO2 and (1−x)Ta2O5−xWO3 thin films are found to be improved compared to those of pure Ta2O5 thin films. In particular, thin films with x=0.08 composition of additive TiO2 or WO3 to Ta2O5 exhibited superior dielectric and insulating properties. The maximum dielectric constant and charge storage density of composite films are about 20 and 53.6 fC/μm2, respectively, higher than those of pure Ta2O5 films (about 13 and 34.5 fC/μm2). The temperature coefficient of the dielectric constant of composite films dramatically decreases from 65 ppm/°C for pure Ta2O5 to less than 11 ppm/°C. The leakage current density of composite films is lower than 1×10−9 A/cm2 up to an applied electric field of 3 MV/cm. The dominant conduction is Poole–Frenkel conduction in the films according to the measurement temperature dependence of the I−V characteristics.
Polycrystalline (1-x)Ta2O5–xTiO2 thin films were formed on a Si substrate by metalorganic decomposition (MOD) at an annealing temperature of 900°C. Thin films with 0.92Ta2O5–0.08TiO2 (x=0.08) composition exhibited superior insulating properties compared to other compositions. The main reason for the improvement in the insulating properties could be the charge compensation of excess oxygen by the TiO2 additive. The leakage current density was lower than 1×10-9A/cm2 up to an applied electric field of 3 MV/cm. The bulk-limited Poole-Frenkel conduction dominates the current–voltage characteristics. capacitance–voltage characteristics of these films showed good dielectric properties with a maximum dielectric constant of 16 and a charge-storage density of 42.5 fC/µm2 at 3 MV/cm.
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