Abstract
We have combined ultrafast pump-probe spectroscopy with optical microscopy to study the charge carrier dynamics in semiconductor nanowires with both spatial and temporal resolution. Photoexcited charge carriers are produced at a localized spot within a single nanowire by a focused femtosecond pump pulse. The electron-hole recombination dynamics at specific points within the structure are then monitored by changes in intensity of a focused probe pulse. The motion of charge carriers through the nanowire is imaged using a spatially-separated pump-probe (SSPP) configuration in which the nanowire is excited in one location and probed in another. The SSPP method has been used to directly observe carrier diffusion in Si nanowires and charge separation in nanowires encoded with an axial p-i-n junction.
Biography
John Papanikolas received his undergraduate degree in Chemistry from Bowdoin College in 1987, before moving to the University of Colorado at Boulder. There, he earned his PhD in Chemical Physics in 1994 with Carl Lineberger, and pursued postdoctoral work with Stephen Leone. In 1997 he moved to the University of North Carolina at Chapel Hill to join the faculty in the Department of Chemistry. Since 2009 he has served as Deputy Director of the UNC Energy Frontier Research Center. His research interests are in use of ultrafast laser spectroscopies to study the fundamental energy and electron transfer processes that underpin solar energy conversion.