Fig. 3
From: Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films
X-ray absorption spectroscopy at the oxygen K edge. a X-ray absorption spectra at O-K edge for polarizations parallel (solid line) and perpendicular (dashed line) to the c-axis of the LaNiO3 films. b Normalized polarization-averaged XAS spectra of the oxygen pre-edge region for films with various thicknesses. c Fitting of the pre-edge peak for the 4 u.c. film (green line) using two Gaussian functions (dashed blue line). d Normalized pre-edge peak for 1.5 u.c. films grown at 1, 5, and 7 Pa oxygen pressures, respectively. e Spectral weight of the shoulder peak, Ashoulder/Atotal, where A is the area under the peak, and the energies of the main and shoulder peaks vs. thickness of the LaNiO3 film grown under 7 Pa oxygen pressure. The error bars for the spectral weight are the standard errors of the mean from the Gaussian fitting of the pre-edge peak areas. f Temperature-dependent resistivity curves for 2 u.c. LaNiO3 films grown under oxygen pressures of 1, 5, and 7 Pa, respectively. Red arrow points to the metal to insulator transition temperature for the film grown at 7 Pa
