Karl Franzens University Graz | Graz University of Technology | |
VISIBLY PHOTOLUMINESCENT SILICON NANOSTRUCTURES AND THEIR USES Silicon dominates electronics but has played a minor role in optoelectronics to date. Bulk crystalline silicon is an indirect bandgap semiconductor with restricted light emission capabilities. However it is now established that many nanoscale forms of silicon (eg. nanoparticles, nanowires, nanosheets, superlattices, nanocomposites, porous silicon) have markedly different bandstructure and optoelectronic properties. This talk will survey progress made over the last 25 years in optimizing, understanding and utilizing the efficient visible luminescence of nanoscale silicon. Quantum confinement effects combined with optimized surface passivation can produce tunable wavelength, photo-excited output of remarkably high quantum efficiency (>50%). Many hundreds of publications now exist on unravelling the complex origin of this phenomenon. Emphasis will be given to spectroscopic studies rather than phenomenological ones. The tremendous progress made in size control, PL efficiency and tunability will also be highlighted. Although the original motivation was the development of electroluminescent devices for optical interconnect, many uses of the efficient photoluminescence itself have now emerged. These include down-converters for solar cells, biological and medical imaging agents, color converters for white LED’s, nano-thermometry probes, fluorescence-based sensing and optical brighteners for cosmetics. |