Epitaxial growth of BaTiO 3 thin films at a low temperature under 300 °C with temperature-controlled BaTiO 3 buffer layer

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The epitaxial growth of BaTiO 3 (BTO) thin films on LaAlO 3 (0 0 1) substrates by laser molecular beam epitaxy was studied using real-time reflection-high-energy-electron-diffraction (RHEED). Atomic force microscopy (AFM) was employed to investigate the surface topography. When the BTO thin films were directly grown at 320 °C with a thickness of above two monolayers (ML), the RHEED patterns vanished rapidly, indicating the failure of crystallinity. However, the growth of eight ML BTO layers can be controlled by decreasing temperature from 600 °C step-by-step to 300 °C. The evolution of diffraction streaks revealed a scaling behavior with temperature and film thickness, demonstrating the evolution of the quasi-two-dimensional BTO islands growth and distribution. Furthermore, subsequently deposited 30 ML BTO thin films with a good crystallinity were obtained on the eight ML BTO buffer layers at a low temperature of 280 °C. It is found that the nucleation centers formed during decreasing temperature play a key role in determining the subsequent crystallization of BTO thin films at a lower temperature.