Size-dependent intrinsic radiative decay rates of silicon nanocrystals at large confinement energies.
We study ultrafast photoluminescence (PL) dynamics of Si nanocrystals (NCs). The early-time PL spectra (<1 ns), which show strong dependence on NC size, are attributed to emission involving NC quantized states. The PL spectra recorded for long delays (>10 ns) are almost independent of NC size and are likely due to surface-related recombination. Based on instantaneous PL intensities measured 2 ps after excitation, we determine intrinsic radiative rate constants for NCs of different sizes. These constants sharply increase for confinement energies greater than approximately 1 eV indicating a fast, exponential growth of the oscillator strength of zero-phonon, pseudodirect transitions.
Sykora
Milan
M
Chemistry Division, Los Alamos National Laboratory, MS-J567, Los Alamos, New Mexico 87545, USA.
Mangolini
Lorenzo
L
Schaller
Richard D
RD
Kortshagen
Uwe
U
Jurbergs
David
D
Klimov
Victor I
VI