Plasmonic nanostructures on silicon

Abstract

The intersection of silicon technology with the rapidly growing field of nanoplasmonics, provides a fertile ground for development of synergistic technologies. The optical and electrical properties of silicon are well understood and well characterized. In this thesis we explore the interactions of plasmonic nanostructures with both passive and active silicon substrates. In the case of a passive silicon substrate, we characterize the properties of propagating surface plasmon waves supported by copper and silver gratings on silicon. We simulate the properties of gold colloid, nanoshells and dielectric particles on lightly doped n-type substrates, through the use of the finite element method. In the case of active silicon substrates, we deposit gold colloid, nanoshells, and dielectric particles on an embedded p+n diode structure. We examine the influence of parameters such as nanoparticle size and plasmon resonance position on the photocurrent measured, in the visible and near infrared wavelength regimes. Both ensemble and local photocurrent measurements are made experimentally. Dielectric particles and Au nanospheres enhance the photocurrent in the 500 nm to 980 nm wavelength range, with a maximum enhancement of 10% observed in the case of both types of nanoparticles. Au nanoshells exhibit a more complex size and wavelength dependent photocurrent alteration pattern, decreasing the photocurrent at wavelengths of 532 and 633 nm, and enhancing photocurrent at wavelengths of 780 and 980 nm. The maximum photocurrent enhancement of 19% was observed for a nanoshell with an inner radius of 96 nm and a outer radius of 116 nm, at a wavelength of 980 nm.