Abstract
The development of large, high-quality flexible high-temperature superconducting films is a crucial focus in flexible electronics research, posing challenges and offering promising applications. Among candidate materials, YBCO is a high-performance high-temperature superconductor. However, the mechanical behavior and stress evolution of its flexible thin films remain a critical gap in current research, hindering further development. In this investigation, a YBa2Cu3O7/SrTiO3/Sr4Al2O7 heterostructure was synthesized on SrTiO3 substrates via pulsed laser deposition (PLD). By selectively etching the water-soluble Sr4Al2O7 sacrificial layer, crack-free, high-quality freestanding YBa2Cu3O7 films at the millimeter scale were successfully fabricated, and remarkable improvements in superconducting properties were achieved, with critical transition temperature and magnetic shielding response approaching the intrinsic characteristics of bulk YBa2Cu3O7. Bending experiments demonstrate that the superconductivity of freestanding YBCO films can be effectively modulated by mechanical strain. Under in‑plane compressive strain, the film exhibits an increased superconducting transition temperature, whereas in‑plane tensile strain diminishes superconductivity. This study not only presents a dependable approach for producing high-quality flexible high-temperature superconducting films but also establishes a fundamental strain-modulation mechanism. By controlling bending, achieved enhancement and continuous modulation of the superconducting properties. These results are essential for the advancement of new-generation flexible electronic devices based on high-temperature superconducting materials.