Time-resolved photoemission electron microscopy of semiconductor interfaces

Semiconductor interfaces are at the heart of the functionality of many devices for opto-electronic applications. At these interfaces, the importance of ultrafast dynamics - processes that occur on sub-nanosecond timescales - has been long understood. While these ultrafast spectroscopic studies have revealed important information, there remains a rich array of physics that is hidden within sub-micrometer length scales when using spatially-averaged techniques. However, powerful tools that could access material dynamics in semiconductors simultaneously at ultrafast time- and sub-micrometer length scales are challenging to implement. Here, we review recent developments in time-resolved photoemission electron microscopy as a technique to study ultrafast electron dynamics at semiconductor interfaces at the nanoscale. In particular, we review recent work in traditional semiconductor interfaces and heterojunctions, low-dimensional materials, and semiconductors for photovoltaic applications.