Department of Chemistry and Biochemistry Seminar
- Friday, November 6, 2020 at 3:10pm
Dr. Joanna Atkin, Assistant Professor at University of North Carolina Department of Chemistry will present “Near-field Optical Spectroscopy for the Study of Electronic Properties in Semiconducting Nanostructures.”
Abstract: Semiconducting nanostructures have been proposed as platforms for a wide variety of photonic, electronic, and photovoltaic elements. In order to realize these applications, careful design and characterization of electronic properties such as dopant concentration, activation, and distribution are needed. I will discuss the use of near-field optical microscopy as a non-destructive method for chemical, structural, and electronic imaging in nanomaterials. Near-field optical techniques can break the diffraction limit to provide nanometer scale information through the lightning-rod properties of an atomic force microscopy tip, but interpretation can be challenging due to convolutional effects. I will focus on two applications in semiconducting nanostructures that illustrate the importance of understanding the influence of the tip and controlling near-field interactions. In the first example, we use infrared near-field spectroscopy to resolve free-carriers in axially-doped silicon nanowires (SiNWs). We can detect local changes in the electrically-active doping concentration from the free-carrier absorption in both n-type and p-type doped SiNWs. The high spatial resolution (< 20 nm) allows us to directly measure dopant transition abruptness in single and multi-junction SiNWs. This is especially valuable in boron-doped p-type SiNWs, for which nanometer-scale information on the junction properties is difficult to obtain without intensive processing. In the second example, we use nano-Raman spectroscopy to study functionalized graphene, a derivative of graphene with a band gap. The high degree of chemical and physical disorder can be resolved with near-field spectroscopy, demonstrating its utility in understanding how local properties of nanomaterials affect functionality in optoelectronic and photovoltaic devices.
Prof. Erik Grumstrup host.
- Department of Chemistry and Biochemistry