This research is a collaborative project with Prof. Brongersma of Stanford University to study the laser induced nucleation of semiconductor quantum dot (QD) nanocrystals in glass microspheres. CO2 laser beam processing will be used to melt the tip of a glass fiber resulting in microsphere formation and subsequent nucleation of QDs. Preliminary results show that we can form CdTe QDs in microspheres (10 mm - 200mm diameter) by this method. The main goal of this research is to investigate the nucleation and growth characteristics to enable controlled processing and nanostructure formation in the glass microsphere geometry. The semiconductor quantum dots in the microspheres will be characterized by electron microscopy (SEM, TEM, HRTEM), small angle X-ray scattering (SAXS), and ultra-sensitive optical spectroscopies that exploit the high Q optical resonances of the microsphere. In these optical modes, light can orbit around the equator of the microsphere for millions of times allowing multiple sampling and strong interaction with the nanoparticles in the sphere. We will develop the procedures for using microspheres as "optical microtest laboratories" and provide general recipes for studying a wide variety of nucleation and growth phenomena glass microspheres.
The project provides a strong science base to nanotechnologies based on optical devices made from materials containing semiconductor nanocrystals in glass microspheres. It also has important practical applications such as ultra-compact and tunable light sources and lasers. The graduate educational program will include under-represented groups.
