Manifestation of lattice distortions in the O 1s spectra in Ca1−xSrxRuO3

We investigate the effect of temperature on the electronic and crystal structures of Ca1−xSrxRuO3 via the evolution of O 1s core level spectra as a function of temperature and composition, xx. O 1s spectra of SrRuO3 exhibit a dominant sharp feature at all the temperatures with a small trace of an impurity feature at higher binding energies. The spectra of Ca doped samples, however, exhibit two distinct features. Analysis of the experimental spectral functions and the band structure results suggest that the different Madelung potentials at the two kinds of oxygen sites in the orthorhombically distorted structure lead to two distinct features in the O 1s spectra. Interestingly, the energy separation of these two features becomes smaller at low temperatures for the Ca dominated samples, suggesting significant structural modification of these samples at low temperatures.