The photoemission study of NdNiO3/NdGaO3 thin films, through the metal-insulator transition

The electronic structure of thin films NdNiO₃/NdGaO₃ with various thicknesses (from 17 nm to 150 nm), have been studied by photoemission spectroscopy at 300 K and 169 K. The XPS results are consistent with the literature ab initio calculations of the NdNiO₃ electronic structure. A noticeable variation attributed to the metal-insulator (MI) transition has been found only for the films with relatively high thickness (150 nm). Furthermore, the photoemission spectra and their temperature dependence have been discussed with regard to the results of dc electrical resistivity measurements which also exhibit large thickness dependence. Finally, these new results support a possible large hetero-epitaxial effect on the thinnest sample (17 nm) which could stress the NdNiO₃ structure and consequently makes its electronic structure nearly stabilized.