My research involves investigations of structure-property relationships in thin films and heterostructures. Of particular interest are the effects of strain relaxation (dislocations, surface and interface roughness), alloy formation (phase separation, clustering, ordering), and diffusion (and interdiffusion) on electronic and optical properties. These phenomena are investigated in a variety of materials systems, including compound semiconductor heterostructures, metallic superlattices, metal-semiconductor interfaces, and superconducting oxide structures. Characterization techniques which probe a range of length scales are used for the investigations. Structural properties are studied with x-ray diffraction, transmission electron microscopy, and scanning tunneling microscopy. Electronic properties are determined using Hall and magnetoresistance measurements, as well as scanning tunneling spectroscopy. Optical properties are studied with photoluminescence spectroscopy and cathodoluminescence imaging.