Figure 5
O 1s PE spectra \(\textrm{O}(\gamma _1)\), \(\textrm{O}(\gamma _2)\) and \(\textrm{O}(\gamma _3)\) integrated over the respective exit angle ranges in the BTO/SRO/DSO (a), BTO/SRO/GSO (b), and BTO/SRO/SSO (c) samples. Each spectrum is normalized to the respective maximum PE intensity. Shaded component areas \(\mathrm {O(1)}\), \(\mathrm {O(2)}\), \(\mathrm {O(3)}\), and \(\mathrm {O(4)}\) refer to \(\textrm{O}(\gamma _3)\) spectra. Components \(\mathrm {O(1)}\), \(\mathrm {O(2)}\), \(\mathrm {O(3)}\), and \(\mathrm {O(4)}\) originate from O atoms in the lattice (\(\mathrm {O_L}\)), \(\mathrm {O_LH}^-\) species, \(\mathrm {CO_x}\) species, and \(\textrm{OH}^-\) and/or \(\mathrm {O_2}^-\) species, respectively. The ratio of component \(\mathrm {O(2)}\) [\(\mathrm {O(4)}\)] over component \(\mathrm {O(1)}\) as a function of exit angle range \(\gamma\) is displayed in panel (d) [(e)] for the three samples under study.
