Significant Suppression of Cracks in Freestanding Perovskite Oxide Flexible Sheets Using a Capping Oxide Layer.

Gong, Lizhikun; Wei, Mian; Yu, Rui; Ohta, Hiromichi; Katayama, Tsukasa · ACS Nano · 2022

basic_science · Level V

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Abstract

Flexible and functional perovskite oxide sheets with high orientation and crystallization are the next step in the development of next-generation devices. One promising synthesis method is the lift-off and transfer method using a water-soluble sacrificial layer. However, the suppression of cracks during lift-off is a crucial problem that remains unsolved. In this study, we demonstrated that this problem can be solved by depositing amorphous Al<sub>2</sub>O<sub>3</sub> capping layers on oxide sheets. Using this simple method, over 20 mm<sup>2</sup> of crack-free, deep-ultraviolet transparent electrode La:SrSnO<sub>3</sub> and ferroelectric Ba<sub>0.75</sub>Sr<sub>0.25</sub>TiO<sub>3</sub> flexible sheets were obtained. By contrast, the sheets without any capping layers broke. The obtained sheets showed considerable flexibility and high functionality. The La:SrSnO<sub>3</sub> sheet simultaneously exhibited a wide bandgap (4.4 eV) and high electrical conductivity (>10<sup>3</sup> S/cm). The Ba<sub>0.75</sub>Sr<sub>0.25</sub>TiO<sub>3</sub> sheet exhibited clear room-temperature ferroelectricity with a remnant polarization of 17 μC/cm<sup>2</sup>. Our findings provide a simple transfer method for obtaining large, crack-free, high-quality, single-crystalline sheets.