Microstructure and dielectric properties with CuO additions to liquid phase sintered BaTiO₃ thin films

The refractory nature of BaTiO₃ leads to limited densification and grain growth for films processed at low temperatures and a modest nonlinear dielectric response due to a marked sensitivity to physical scale and material quality. Adding liquid-forming sintering AIDS, common in bulk ceramics, to thin films enhances mass transport, leading to enhanced grain growth at lower temperatures. This work explores the effectiveness of a sputtered CuO buffer layer with BaO-B₂O₃ (BBO) fluxes to engineer the microstructure of BaTiO₃ films. Grain size and homogeneity increase in the presence of even a ∼1 nm CuO layer. In general, grain size increases from 75 to 370 nm with an addition of 2.2% BBO and 8 nm CuO. Room temperature capacitance in fluxed films increases by a factor of 5 over pure films, and ferroelectric phase transitions are clearly observable in dielectric measurements. CuO-BBO proves effective on (0001) Al₂O₃ and (100) MgO substrates, although all microstructures are notably finer for the latter.