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

- The post-treatments of the nanosheet film deposited by EPD were compared.
- The nanosheet film by EPD has a limitation in decomposing TBA+ by only UV treatment.
- An additional thermal treatment was proposed to overcome the UV limitation.
- Dielectric constant increased from 8 to 27, whereas tan δ decreased from 5% to 2%.

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+.