Monday, June 16, 2008
Room 1 (McKimmon Conference Center)
224

Use of Non-Linear Microscopy to Probe ZnO Nanostructures

Ralph L. House, Brian P. Mehl, Chuan Zhang, Abhineet Uppal, Amanda Reams, and John M. Papanikolas. University of North Carolina at Chapel Hill, Chapel Hill, NC

It has long been known that nanoscale objects with dissimilar shapes exhibit different dynamics, yet the exploration of how these dynamics vary within the object have not been explored. Due in part to its wide band gap (3.37 eV) and large exciton-binding energy (60 meV), the potential application of ZnO in nanostructured devices and optoelectronics has led to extensive research to synthesize and characterize various nanostructures. We have developed methods to grow faceted single-crystal ZnO structures that range in length from 1 to 30 um, using hydrothermal and solution phase techniques. By coupling our ultrafast laser system with a home built inverted optical microscope, we imaged these structures using a combination of non-linear optical microscopy techniques. Single-point emission spectra were obtained by positioning the laser spot over different points in the nanorod and scanning the monochromator. The results indicate that measurements from different locations yield different emission spectra. Furthermore, by integrating our time-correlated single-photon counting apparatus with the non-linear microscope we successfully time resolved the emission at spatially distinct locations within a single structure. The emission transients exhibit different decay kinetics, suggesting that recombination times vary from one location in the rod to the next. Although ZnO is the initial target, we envision future efforts focusing on a wide variety of metal oxide and chalcogenide materials.