Formation of Ge alloy nanocrystals embedded in silica Eugene E. Haller, University of California-Berkeley, DMR Above: High-angle annular dark field (HAADF) scanning transmission electron microscope (STEM) image of Ag-Ge bi-lobed nanoparticles embedded in SiO 2. The bright regions are Ag and the darker regions are Ge. Thin films of SiO 2 are co-sputtered with Ag and Ge. The bi-lobed nanoparticle forms in a glass matrix due to phase segregation of the constituents and is thermodynamically stable at room temperature. Intellectual Merit Gold and silver structures, with sizes of nm, exhibit a resonance condition when interacting with visible and near infra-red light. This localized surface plasmon resonance causes extreme electric field intensities at the surface of the structure which can enhance optical processes such as Raman scattering, light absorption and flourescence. Although many applications exploiting the enhanced optical processes utilize a single gold or silver nanoparticle, hybrid- nanostructures that contain a second component made of a metal, dielectric or semiconductor are being designed. We introduce a novel metal-semiconductor bi-lobed nanoparticle comprised of a lobe of Ag and lobe of Ge (image to the right). The semispherical shape of the silver fraction and the shared Ag-Ge interface produce a unique localized surface plasmon resonance in the visible to near infra-red range. It is proposed that the Ag surface plasmon couples to the semiconductor at the shared interface. This coupling will be probed with a surface-enhanced Raman experiment. 5 nm Plasmonic Ag-Ge Nanoparticles

Formation of Ge alloy nanocrystals embedded in silica Eugene E. Haller, University of California-Berkeley, DMR Education and Broadening Participation of Underrepresented groups : Karen Bustillo, a returning graduate student, is the major contributor to this project. In addition to managing the Photoluminescence Laboratory, she is learning advanced techniques on the transmission electron microscope including electron energy loss spectroscopy (image to the left) and energy filtered imaging. She is expected to complete her PhD degree August Technological Outputs: The plasmonic properties of gold and silver nanoparticles are exploited in applications addressing diverse problems. Gold nanoparticles are used in medical diagnostics, medical imaging and photothermal therapy. Highly sensitive handheld detection systems employing plasmonic particles are envisioned as environmental sensors. Utilizing gold or silver nanostructures as a method to couple light into optical devices holds promise for optical communications. Researchers in the fields of solar energy and catalysis have examined plasmonic nanostructures as avenues for improvements in their respective technologies. Above: Electron energy loss spectroscopy (EELS) in the transmission electron microscope allows one to probe the intensity of the electric field at the individual particle surface. The energy loss spectrum collected from the location marked with an x indicates a response near 3.1 eV or 400 nm (blue light) which corresponds to the localized surface plasmon resonance measured using spectrophotometry. Numerical calculations are being employed to corroborate the EELS data. X