We have investigated the optoelectronic characteristics of bulk single-crystal SrTi O3 (STO) and epitaxial STO on Si by photoluminescence and cathodoluminescence (CL) techniques. In particular, we have explored to what extent these techniques can offer information about crystal quality. We have complemented these observations with atomic force microscopy, transmission electron microscopy (TEM), and micro-Raman measurements. Panchromatic CL imaging of bulk STO revealed contrast features associated with growth-related striations, extended defects, and mechanical damage. CL imaging of undoped high-resistivity substrates was limited by beam charging effects. The weak nature of the CL signal from epitaxial STO (relative to bulk material) made it very difficult to visualize any features by analog detection. On the other hand, spectrally resolved CL measurements of epitaxial STO using single-photon counting techniques, revealed sensitivity to the defect content and film quality across a 3-in wafer. Preliminary results indicate a qualitative correlation in the room-temperature near band-edge luminescence properties (3.2-3.5 eV) and crystalline quality as determined by micro-Raman spectroscopy and TEM. © 2005 American Institute of Physics.