Dependence of the electronic structure of SrRuO3 and its degree of correlation on cation off-stoichiometry

We have grown and studied high quality SrRuO3 films grown by molecular beam epitaxy as well as pulsed laser deposition. By changing the oxygen activity during deposition, we were able to make SrRuO3 samples that were stoichiometric (low oxygen activity) or with ruthenium vacancies (high oxygen activity). This ability to control the ruthenium stoichiometry has permitted us to make a systematic study of the dependence of the degree of electron correlation in SrRuO3 on stoichiometry using transport and photoemission experiments. We have compared the measured ultraviolet photoemission spectroscopy spectra with calculated density of states spectra and offer explanations for the large observed differences between the two.