This project seeks to endow Si-compatible materials with increased optical functionality. Epitaxial architectures that arrange Ag islands in proximity to Ge/Si(100) quantum dots (QDs) will be investigated to assess plasmonic enhancements to luminescence efficiency. The localized surface plasmon (LSP) mode of the Ag island is predicted to improve both the absorption and emission of photons by the Ge QD. Increased absorption results from the dramatic field concentration near the Ag nanoparticle. The Purcell effect increases the spontaneous emission rate. Recent theoretical work suggests that plasmonic enhancements will be greatest for optimally arranged Ge dots and Ag islands if the LSP resonance frequency is close to that of the QD exciton. The near UV LSP resonance of the Ag islands will be tuned to match the near IR exciton energy of the Ge/Si(100) QDs using a combination of shape resonance effects and by varying their dielectric environment. In the ideal case, theory predicts the luminescence enhancement can approach two orders of magnitude.

One focus will be to determine whether the inhomogeneously strained planar surface of the Si layer that caps the buried Ge dots can affect the thermodynamics or kinetics of Ag island nucleation. The second focus will be on the nm-scale pits found immediately above the Ge dots just prior to completion of the Si cap layer.

This project will positively affect the education and future career of the student(s) involved in the research. They will be trained in the synthesis as well as the structural and optical characterization of materials and architectures in the rapidly growing field of plasmonics. Additionally, links to the highly successful Science is Fun program offered by the Leroy Eyring Center for Solid State Science at ASU will be established.

This program impacts on average 12,000 high and middle school students annually. The PI will work closely with Science is Fun staff and interns to develop hands-on, age-appropriate activities that demonstrate interaction of light with photonic structures using naturally occurring butterfly wings, bird feathers and seashells as "attention grabbers."