Professor, Department of Physics & Astronomy
Location: 4222 Biomed Phys Sci
Our research team is among a handful of groups in the world actively developing ultrafast electron diffraction and imaging technologies for studying materials and molecular processes in the ultrafast time scale and with atomic scale resolution. graphIn many ways complementary to the uses of X-rays, obtained from the powerful synchrotron and in the future hard-X-ray free electron lasers facilities, the electron technology is advantageous in nondestructive investigation of nanomaterials and interfaces due to its strong scattering with atomic nuclei. In the past few years, our researches have been directed in understanding the photophysical and photochemical processes in nanomaterials, including: searches for optical route of graphite-to-diamond transformation, and investigating plasmonic effects in nanoparticles, phase transitions of small particles, and the cooperative phenomena of charge density waves. # Education: * 2000: Ph.D., University of Texas, Austin We recently discovered that by properly analyzing the pulsed electron scattering pattern, the ultrafast electron diffraction is sensitive to the crystal potential changes and charge ordering, thus offering new ways to investigate collective electronic processes. Efforts have been made to understand the laser induced hot electron dynamics and photoemission from various functional materials, and strongly correlated materials exhibiting optical switching. Beyond investigating the fundamental physics, mechanistic understanding of the elemental processes in light-induced phase transition and energy transport in nanoscale materials and interfaces are important to implement an array of applications in optoelectronics, such as memory, nanoelectronics technologies, and clean energy sciences, such as photovoltaics, and photocatalysis. labThese research efforts are intimately coupled with continuing development of methods to provide the necessary resolutions and throughput to resolve the critical sciences. Currently, the team members are developing an environmental cell for solution phase ultrafast diffraction, robust methods for dynamical diffraction analyses, and, through collaborating with experts in laser, electron microscope, and accelerator/beam sciences, constructing a new generation of high-brightness ultrafast diffraction camera. # Education: * 2000: Ph.D., University of Texas, Austin
- Direct observation of optically induced transient structures in graphite using ultrafast electron crystallography (Phys. Rev. Lett. 101, 077401 (2008)).
- Dynamics of size-selected gold nanoparticles studied by ultrafast electron nanocrystallography (Nano Lett. 7, 1290 (2007)).
- Electronically driven fragmentation of Ag nanocrystals revealed by ultrafast electron crystallography (Phys. Rev. Lett. 104, 123401(2010))
- Photovoltage dynamics of the hydroxylated Si(111) surface investigated by ultrafast electron diffraction (Phys. Rev. B 77, 245329 (2008)).
- Ultrafast imaging of photoelectron packets generated from graphite surface (Appl. Phys. Lett. 95, 181108(2009))