Optical and Thermal Properties of Nanoporous Material and Devices

Abstract

In this thesis, we investigate the optical and thermal properties of porous silicon and its applications. In first part, porous silicon's optical properties and application as a highly sensitive refractive index sensor is studied. An integrated Mach-Zehnder interferometer waveguide fabricated from nanoporous silicon is shown to exhibit high sensitivity and measurement stability that exceeds previously demonstrated porous sensors. In second part, we discuss experimental methods to characterize the thermal conductivity of nanoporous silicon films. We use the 3-ω method to characterize the exceptionally low thermal conductivity of porous silicon. Finally, we employ an improved heat conduction analysis method for the 3-ω method to measure the anisotropy in thermal conductivity. Our measurement show that porous silicon has very low in-plane thermal conductivity compared to cross-plane conductivity. We confirmed this anisotropy using direct numerical simulation of the anisotropic heat equation.