Dielectric properties of single crystal Sr₂Nb₃O₁₀ dielectric nanosheet thin films by electrophoretic deposition (EPD) and post deposition treatments

Sr₂Nb₃O₁₀ (SNO) nanosheets were obtained by exfoliating from a perovskite layered structure of HSr₂Nb₃O₁₀ (HSNO). The nanosheets were deposited on substrates simultaneously with unintended tetrabutylammonium cations (TBA⁺) by electrophoretic deposition (EPD) process. To eliminate TBA⁺ from the SNO dielectric nanosheet thin films, the films were exposed to ultraviolet (UV). Since UV exposure can't decompose TBA⁺ completely, thermal annealing was additionally conducted by employing different furnaces at various atmospheres. XRD shows the reduction in lattice constant after UV and thermal treatments, indicating that TBA cations were decomposed in the interlayer of nanosheets. FT-IR spectra analysis depicted that the organic materials were eliminated through the post deposition treatments. In addition, XPS data indicated that films treated by a combination of UV and thermal had a lower relative atomic ratio of carbon and nitrogen than as-deposited and only-UV treated films. The optimum process conditions for improving dielectric properties were UV exposure for 15 h and subsequent thermal annealing in a box furnace in the air at 600 °C for 1 h. When compared to the as-deposited film, the dielectric constants of films further annealed by the box furnace in the air were increased from 8 to 27 at 1 MHz whereas dielectric loss (tan δ) decreased from 5% to 2%. Additional thermal treatment strongly affects nanosheets to decompose TBA⁺.