Size-dependent intrinsic radiative decay rates of silicon nanocrystals at large confinement energies

PHYS 214

Milan Sykora, sykoram@lanl.gov1, Lorenzo Mangolini2, Richard D. Schaller, rdsx@lanl.gov3, Uwe Kortshagen, uk@me.umn.edu2, David Jurbergs4, and Victor Klimov1. (1) Physical Chemistry and Applied Spectroscopy, Los Alamos National Laboratory, Los Alamos, NM 87544, (2) Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, (3) Chemistry Division, Los Alamos National Laboratory, TA-46, MS-J567, Los Alamos, NM 87545, (4) Innovalight, Inc, 3303 Octavius Drive, Santa Clara, CA 95054
Following the initial observation of efficient photoluminescence (PL) from porous Si, there has been a great interest in understanding of the mechanism of PL enhancement in Si nanostructures compared to bulk Si. In spite of significant effort the mechanism for high-efficiency PL from Si nanostructures is still under debate. In the presented work we study evolution of PL dynamics on time-scales from femtoseconds to microseconds for Si nanocrystals (NCs)prepared by two different methods. We show that the PL consists of contributions from both the surface localized states and NC core, quantized states. Based on instantaneous PL intensities measured 2 ps after excitation, we determine intrinsic radiative decay rates for NCs of different sizes. These rates sharply increase for confinement energies greater than ~1 eV indicating a fast, exponential increase in the oscillator strength of zero-phonon, pseudodirect transitions.
 

Spectroscopy, Chemistry, and Imaging through Nanophotonics
8:00 AM-12:00 PM, Tuesday, April 8, 2008 Morial Convention Center -- Rm. 345, Oral

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008