Temperature-independent physical properties of electrophoretic Ti₅NbO₁₄ films for high-temperature capacitors

Ti₅NbO₁₄ (T5NO) films were developed on Pt/Ti/SiO₂/Si substrates by electrophoretic method by using T5NO³⁻ nanosheets. The film deposited at room temperature (RT) contained organic defects, which were almost eliminated in the film annealed at 700 °C. The film deposited at RT revealed (100) planes with an inter-planar distance of 1.1 nm because of the existence of TBA⁺ defects. However, for the films annealed at higher temperatures (≥400 °C), two types of structures formed: (100) planes with 0.55 nm inter-planar distance (group-1 structure), and (100) planes with 1.42 nm inter-planar distance (group-2 structure). The dielectric constant (ε_r) of the film annealed at 700 °C was 61 with a low dielectric loss of 1.0%. Variations in the ε_r according to the film thickness, electric field, and temperature were small. This film displayed a high insulating property up to 300 °C with a small temperature coefficient of capacitance (−56.7 ppm/K) up to 400 °C.