  This study shows that the dielectric function of crystalline Si quantum wells
(c-Si QW) is influenced by both carrier confinement and electron-phonon
interactions. The energy shifts and lifetime broadening of the excitonic E1
direct gap transition of c-Si QWs from 2 to 10 nm are found to have a
significant dimensional and temperature dependence that can be traced to
changes in the phonon dispersion of nanoscale films. The influence of
electron-phonon interactions on the dielectric function was verified by
altering the phonon dispersion using different dielectric layers above a 5 nm
c-Si QW.
