Characteristics of ta²O⁵ thin film prepared by electron beam heating method

Abstract

A Ta2O5 film formed by ϵ‐beam evaporation (EB‐Ta2O5) was nonstoichiometric because of oxygen deficiency, resulting in electron trapping. As a result, the dielectric constant was higher than that of bulk material. the trapped fixed‐charge density increased with a decrease of film thickness. When the film was 300 nm, the trapped fixed Charge density was as high as 1016 cm−3. However, when the film was thicker than 300 nm, it decreased rapidly. the dielectric constant approached the bulk value as the film thickness increased, and the film resistance was low because of oxygen deficiency. When the film was 300 nm, the resistivity p was 107 − 108 ω ‐cm (5 × 105 V/cm). When the electric field reached about 7 × 105 V/cm, only the current density increased in spite of the slight increase of the electrical field. When the film was thicker than 300 nm, the resis tivity increased and the clamp field became unclear with an increase of thickness. an EL (electroluminescent) device was formed using the EB‐Ta2O5 film sandwiched with SiO2 films as the luminescent film. the luminance of the device was 100 cd/2. the luminescence spectrum had peaks at 380, 430, 475, and 540 nm, indicating that there were energy levels at 3.2, 2.9, 2.6, and 2.3 eV.