  Emergent behavior at complex oxide interfaces has driven much of the research
in the oxide thin film community for the past twenty years. Interfaces have
been engineered for potential applications in spintronics, topological quantum
computing, and high-speed electronics in cases where the bulk materials would
not exhibit the desired properties. Advances in thin film growth have made the
synthesis of these interfaces possible, while surface characterization tools
such as X-ray photoelectron spectroscopy have been critical to understanding
surface and interfacial phenomena in these materials. In this review we discuss
the leading research in the oxide field over the past 5-10 years with a focus
on connecting the key results to the X-ray photoelectron spectroscopy studies
that enabled them. We describe how in situ integration of synthesis and
spectroscopy can be used to improve the film growth process and to perform
immediate experiments on specifically tailored interfacial heterostructures.
These studies can include determination of interfacial intermixing, valence
band alignment, and interfacial charge transfer. We also show how advances in
synchrotron-based spectroscopy techniques have answered questions that cannot
be addressed in a lab-based system. By further tying together synthesis and
spectroscopy through in situ techniques, we conclude by discussing future
opportunities in the field through the careful design of thin film
heterostructures that are optimized for X-ray studies.
