presented by Naomi Ginsberg (University of California, Berkeley)

Hosted by Prof. Andrew Musser

Abstract: 

The energy and communication demands of modern life ask a lot of semiconductors, not only in electronics but also in display technology and solar cells. We typically think of semiconductors being built of atoms, like silicon. Yet, creating semiconductors and other electronic materials from basic building blocks more complex than individual atoms not only opens the possibility to create and study a wider range of emergent properties but also reveals new relationships between a material’s structure and function. The hierarchy of strong intra-building block and weaker inter-building block interactions in a next generation of semiconductors even allows these materials to be formed near room temperature and starting from liquid precursors, albeit with nanoscale structural heterogeneities and disorder that can strongly impact their macroscopic optoelectronic properties. To elucidate the multiscale relationships between material formation, form, and emergent function I will describe examples of such phase transformations and of how energy flows through hierarchical structures in both actual and model complex semiconductors. We reveal the underlying mechanisms only by virtue of my group’s sustained development of a suite of spectroscopic nano-imaging tools that allow us to access the most appropriate combinations of spatial and temporal resolution. In particular, I will take you first on a journey with transient optical elastic scattering microscopy to reveal the nature of energy flow–structure correlations for various photogenerated species in virtually any semiconductor. We will then explore the structural dynamics of phase transitions away from equilibrium using low-dose scanning electron microscopy and cathodoluminescence.