Probing and Manipulating the Luminescence Properties of Porous Semiconductor Nanoparticles

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Steven Buratto of the University of California at Santa Barbara is supported by the Experimental Physical Chemistry Program for research that aims to probe and manipulate luminescence properties of porous silicon nanoparticles. To avoid deleterious averaging effects, optical properties will be probed on isolated nanoparticles derived from bulk porous silicon, using single molecule spectroscopic techniques. Project goals include obtaining a detailed understanding of the luminescence properties of these nanoparticles and how such properties depend on the surface functionality, the size of the emitting silicon quantum dot (i.e. porosity of the bulk porous silicon) and the dopant concentration of the silicon starting material. Another goal is to correlate more accurately the size of the emitting species with the luminescence wavelength, in order to determine the degree of quantum confinement. Finally, experiments will determine if the single nanoparticles under study consist of a single two-level system by measuring antibunching in the sample emission. Outcomes are expected to enable new understandings of nanoparticle luminescence properties, aid in the development of porous silicon as an optical material, and suggest new directions to maximize the optical properties of porous silicon. The observation of visible light emission from porous silicon has stimulated tremendous interest over the past several years due to its applications in optoelectronic devices and lasers, and the potential for integration with current silicon processing technologies. Luminescence from porous silicon was first observed over a decade ago, and since that time scientists have struggled to develop a mechanism to describe the photophysical properties of this material. Although a consistent physical description is still lacking, a host of test devices has been produced making use of the tunable luminescence and high surface area of porous silicon. These devices include molecular sensors, light emitting diodes, optical switches, and photovoltaic cells. Successful outcomes for this research are expected to impact the development of further useful devices using porous silicon.