Dong, Yongqi; Ma, Zhiyuan; Luo, Zhenlin; Zhou, Hua; Fong, Dillon; Wu, Wenbin; Gao, Chen
Much like epitaxial strain, engineering oxygen octahedral rotations (OORs) in perovskite oxide thin films can be a powerful means of manipulating their physical and chemical properties. Here, it is demonstrated that the fundamental character of the metal-insulator transition (MIT) can be sensitively controlled by the structure of the oxygen sublattice for NdNiO3 thin films grown epitaxially on NdGaO3 (110) substrates. The MIT is sharp and hysteretic for a Ni-O-Ni bond angle of 154.0 degrees (6 nm thick film) like the bulk behavior, while it is diffuse and largely nonhysteretic for a bond angle of 149.5 degrees (3 nm thick film), stemming from the smaller bond angle of the NdGaO3 substrate. Using synchrotron X-ray diffraction to quantify the geometric framework of the oxygen sublattice, it is found that the influence of the substrate OORs propagates and decays after a few nanometers into the ultrathin film. The sublattice structure in the 6 nm thick film is similar to that for bulk NdNiO3, leading to the sharp and hysteretic MIT.