Event
Ph.D. Dissertation Defense: Kyowon Kim
Wednesday, July 8, 2015
10:00 a.m.
IREAP Large Conference Room (ERF 1207)
William Churma
301 405 0680
churma@umd.edu
ANNOUNCEMENT: Ph.D. Dissertation Defense
Name: Kyowon Kim
Committee:
Professor Thomas E. Murphy, Chair/Advisor
Professor Christopher Davis
Professor Romel Gomez
Professor Yu Chen
Professor Oded Rabin, Dean's Representative
Date/Time: Wednesday, July 8, 2015 at 10:00 am
Location: IREAP Large Conference Room (ERF 1207)
Title: Optical and Thermal Properties of Nanoporous Material and Devices
Abstract:
In this thesis, we investigated optical, thermal properties of porous silicon and its applications.
In first part, porous silicon's optical properties and application as a highly sensitive refractive type sensor is studied.Optical waveguides comprised of nanoporous materials are uniquely suited for on-chip sensing applications, because they allow for a target chemical or analyte to directly infiltrate the optical material that comprises the core of the waveguide. We fabricated and characterized nanoporous waveguides, and demonstrated their usefulness in measuring small changes in refractive index when exposed to a test analyte. We used a process of electrochemical etching and laser oxidation to produce channel waveguides and integrated on-chip Mach-Zehnder structures, and we measured the responsivity by selectively applying isopropanol to a small waveguide segment in one arm of the interferometer. Sensitivity analysis revealed that our device surpass previously reported devices in sensitivity. Compared to fiber-based interferometer device, integrated interferometer is shown to provide more stable response.
In second part, porous silicon's thermal conductivity and experimental method are discussed. Porous silicon exhibits thermal conductivity 2-3 order of magnitude smaller than crystalline silicon, which is comparable or even lower than common thermal insulation material such as silicon dioxide. In addition, it's matching coefficient of thermal expansion with crystalline silicon provide a unique advantage as a thermal insulator. We measured porous silicon's thermal conductivity with 3-omega method, and the result agreed with previous reported studies. Despite porous silicon's strong structural anisotropy, its anisotropy in thermal property has not been investigated. We used both 2D heat flow analysis based on 3-omega measurement and numerical simulation to measure in-plane and cross-plane thermal conductivity of porous silicon. The result showed that porous silicon's in-plane thermal conductivity is 1-2 order of magnitude lower than cross-plane component.
