[16p-A409-1~17] 6.1 Ferroelectric thin films

▼ [16p-A409-4] Flexible BaTiO₃ Epitaxial Films with Bulk-like Ferroelectricity and Piezoelectricity

〇Lizhikun Gong¹, Binjie Chen¹, Rui Yu¹, Hiromichi Ohta², Katayama Tsukasa^2,3 (1.IST, Hokkaido Univ., 2.RIES, Hokkaido Univ., 3.JST-PRESTO)

Keywords:Flexible oxide film, Ferroelectric oxide film

Flexible electronic devices based on epitaxially-grown oxide films have attracted considerable attention in recent years, owing to their diverse functions such as ferroelectricity and piezoelectricity. However, due to the limit of processing techniques, most of the perovskite oxides are only processible with poor crystal quality even though they were hetero-epitaxially grown on a flexible single crystalline substrate like Mica, leading to much lower performances of film compared to epitaxial films on single crystalline oxide substrates. Recently, a Sr₃Al₂O₆ (SAO) sacrificial layer was utilized to peel-off the epitaxial oxide films ^[1]. However, many cracks are introduced to the peel-offed film due to release of lattice strain in the case of BaTiO₃ (BTO) on SAO buffered SrTiO₃ substrate. To overcome this difficulty, we found covering a 300-nm-thick amorphous AlO_x film on the epitaxial oxide film surface is effective to suppress crack generation ^[2]. In this study, we demonstrated a method to obtain flexible epitaxially-grown oxide films with ferroelectricity and piezoelectricity on arbitrary substrate. Through this method, large-size (25 mm²) crack-free epitaxially-grown rolled and flat BTO sheets were obtained on glass or PET substrate with covered an amorphous AlO_x/ITO bilayer film, by directly placing as-grown film in deionized water and transferring using tweezers (Figure a), demonstrating the excellent flexibility and strong toughness of the film. The BTO films exhibited ferroelectricity and piezoelectricity similar to the bulk single-crystal (Figures b and c).