Thickness (nm) Wavelength (nm) Tunable asymmetric reflectance in percolating silver films Miriam Deutsch, University of Oregon, DMR Nanostructured thin metal films with controllable dispersions are of particular technological interest. In particular, studies have shown that the incident- photon-to-current conversion efficiencies of photovoltaic cells with semi-transparent rough metal substrates are significantly higher than those of standard smooth-mirror devices. Enhanced light scattering induced by such hazy substrates leads to multiple scattering, enhancing overall optical path length and absorption efficiency of the trapped light. This project focuses on optical characterization of such granular silver films exhibiting tunable optical reflectance asymmetries, ∆R. Films are obtained using a multi-step process, where a nanocrystalline silver film is chemically deposited on a glass substrate and then subsequently coated with additional silver via thermal vacuum-deposition. The resulting films exhibit reflectance asymmetries [1] whose dispersions may be tuned both in sign and in magnitude, as well as a universal, tunable spectral crossover point. We obtain a correlation between the optical response and charge transport [2] in these films, with the spectral crossover point indicating the onset of charge percolation. [1] A. Chen, K. Hasegawa, V.A. Podolskiy, M. Deutsch, Opt. Lett. 32, 1770 (2007) [2] M.S.M. Peterson, M. Deutsch, J. Appl. Phys. 106, (2009) ∆R plotted against vacuum-deposited film thickness (left panels) and wavelength (right) for films with metal filling fraction of 15% (top panels) and 61% (bottom.) Arrows in left panels indicate a crossover in ∆R, as well as the observation of the onset of charge percolation. Color coded traces in the right panels denote the dispersion of ∆R plotted for different thicknesses of vacuum-deposited films. The onset of percolation is accompanied by a change in the sign of the dispersion of ∆R.

The mission of SPICE is to collaborate in creating a learning environment where girls can thrive in Science, Technology, Engineering and Mathematics (STEM.) This broad goal is achieved by enhancing the science experiences of middle and high school girls, through a set of proven intervention strategies, including: Mentoring Early hands-on research experience Role models Access to Information and Equipment Building a Community of Young Scientists The goals of SPICE are: To increase the number of women participating in all levels of STEM careers, particularly the physical sciences. To increase the number of women attaining advanced degrees in all STEM fields. To contribute to a scientifically literate society by introducing a new generation of women to scientific inquiry. SPICE is supported by the University of Oregon’s Office of Institutional Equity and Diversity, LaserFest, NSF and private donors. Science Program to Inspire Creativity and Excellence – SPICE Miriam Deutsch, University of Oregon, DMR SPICE participant compares soil samples during Crime Scene Investigation Camp which took place in June