Synthesis of Chemically Sharp Interface in NdNiO₃/SrTiO₃ Heterostructures

【摘要】 The nickel-based superconductivity provides a fascinating new platform to explore high-Tc superconductivity.As the infinite-layer nickelates are obtained by removing the apical oxygens from the precursor perovskite phase,the crystalline quality of the perovskite phase is crucial in synthesizing high quality superconducting nickelates.Especially, cation-related defects, such as the Ruddlesden–Popper-type（RP-type） faults, are unlikely to disappear after the topotactic reduction process and should be avoided during the growth of the perovskite phase.Herein, using reactive molecular beam epitaxy, we report the atomic-scale engineering of the interface structure and demonstrate its impact in reducing crystalline defects in Nd-based nickelate/SrTiO₃ heterostructures. A simultaneous deposition of stoichiometric Nd and Ni directly on SrTiO₃ substrates results in prominent Nd vacancies and Ti diffusion at the interface and RP-type defects in nickelate films. In contrast, inserting an extra[NdO] monolayer before the simultaneous deposition of Nd and Ni forms a sharp interface and greatly eliminates RP-type defects in nickelate films. A possible explanation related to the polar discontinuity is also discussed. Our results provide an effective method to synthesize high-quality precursor perovskite phase for the investigation of the novel superconductivity in nickelates.更多还原

【Abstract】 The nickel-based superconductivity provides a fascinating new platform to explore high-Tc superconductivity.As the infinite-layer nickelates are obtained by removing the apical oxygens from the precursor perovskite phase,the crystalline quality of the perovskite phase is crucial in synthesizing high quality superconducting nickelates.Especially, cation-related defects, such as the Ruddlesden–Popper-type（RP-type） faults, are unlikely to disappear after the topotactic reduction process and should be avoided during the growth of the perovskite phase.Herein, using reactive molecular beam epitaxy, we report the atomic-scale engineering of the interface structure and demonstrate its impact in reducing crystalline defects in Nd-based nickelate/SrTiO₃ heterostructures. A simultaneous deposition of stoichiometric Nd and Ni directly on SrTiO₃ substrates results in prominent Nd vacancies and Ti diffusion at the interface and RP-type defects in nickelate films. In contrast, inserting an extra[NdO] monolayer before the simultaneous deposition of Nd and Ni forms a sharp interface and greatly eliminates RP-type defects in nickelate films. A possible explanation related to the polar discontinuity is also discussed. Our results provide an effective method to synthesize high-quality precursor perovskite phase for the investigation of the novel superconductivity in nickelates.更多还原