Spectroscopic SHG and spectroscopic ellipsometry study of silicon nanocrystals embedded in SiO$_{2}$

POSTER

Abstract

The light-emitting silicon nanocrystals (Si NCs) embedded in silica matrix open up the possibility for silicon photonics. Optical spectroscopy can help elucidate unique, but poorly understood, bonding structures at the nano-interfaces that are responsible for the efficient photoluminescence. Here we present SHG amplitude and phase spectra of a 1$\mu$m-thick layer of 3 nm $\pm$ 30{\%} diameter Si NCs prepared by implanting Si ions into SiO$_{2}$ then annealing in Ar or H$_{2}$/Ar mixture at 1100$^{\circ}$C using cross-polarized two-beam second-harmonic generation (XP2-SHG). We also measure the linear dielectric function of the NC layer using spectroscopic ellipsometry (SE). The linear spectra show a significant reduction in the dielectric functions in Si NCs compared to bulk silicon. The pronounced E$_{2}$ critical point transition peak is somewhat blueshifted to the bulk E$_{2}$ peak while E$_{1}$ transition is strongly suppressed. The SHG spectra are only slightly perturbed by annealing in hydrogen. A fit of the SHG amplitude and phase spectra using model resonance functions yields resonances different from the linear spectra. A model with an intermediate transition layer of variable composition between the Si NC core and the amorphous SiO$_{2}$ matrix is introduced to explain the linear and SHG spectra.

Authors

  • Junwei Wei

    University of Texas at Austin, Department of Physics

  • Sacha Kopp

    Texas Lutheran, Texas Lutheran University, Bastrop ISD, Lego Education, LEGO Education, South Texas Chapter, Health Physics Society, Waxahachie Early College High School, Navarro College, and Texas A\&M Commerce, PTRA/AAPT, National Instruments, Department of Physics, University of Texas at Austin, Texas A&M University - Commerce, University of Dallas, Austin Community College, Angelo State University, K-12 Science Consultant Birdville ISD, Energy Institute, University of Texas at Austin, Southern Univertisy Baton Rouge, Univ. of Arkansas, Univ. of Central Florida, JQI, NIST and Univ. of Maryland, UT Austin, Center for Ultrafast Optical Science, University of Michigan, Lawrence Berkeley National Laboratory, University of Texas at Austin, Lockheed Martin, NASA, South Plains College, LBNL-ALS, Berkeley, Denison U., Granville, U. of Nevada, Reno, Justus-Liebig-Universitat, Giessen, Western Michigan U., Kalamazoo, University of Texas at Austin, Department of Physics, Institute for Applied Physics, University of Muenster

  • Michael C. Downer

    University of Texas at Austin, University of Texas at Austin, Department of Physics, Univ. of TX at Austin, University of Texas at Austin, Department of Physics, Austin, TX 78712-1081, USA