The effect of growth conditions on the structural and electronic properties of the polar/non-polar LaCrO$_3$/SrTiO$_3$ (LCO/STO) interface has been investigated. The interface is either insulating or metallic depending on growth conditions. A high sheet carrier concentration of 2x10$^{16}$ cm$^{-2}$ and mobility of 30,000 cm$^2$/V s is reported for the metallic interfaces, which is similar to the quasi-two dimensional gas at the LaAlO$_{3}$/SrTiO$_{3}$ interface with similar growth conditions. High-resolution synchrotron X-ray-based structural determination of the atomic-scale structures of both metallic and insulating LCO/STO interfaces show chemical intermixing and an interfacial lattice expansion. Angle resolved photoemission spectroscopy of 2 and 4 uc metallic LCO/STO shows no intensity near the Fermi level indicating that the conducting region is occurring deep enough in the substrate to be inaccessible to photoemission spectroscopy. Post-growth annealing in flowing oxygen causes a reduction in the sheet carrier concentration and mobility for the metallic interface while annealing the insulating interface at high temperatures and low oxygen partial pressures results in metallicity. These results highlight the critical role of defects related to oxygen vacancies on the creation of mobile charge carriers at the LCO/STO heterointerface.
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