Energy losses of hot electrons in a thin layer of SiO2 on Si

In vacuo photoemission from SiO2-covered Si shows that the quantum yield and the energy threshold depend on the SiO2 layer in the 10- to 120-Å thickness range. These effects have been explained by electron-optical phonon scattering in the thin SiO2 layer before one Si-emitted electron escapes into the vacuum. An approximate value of the phonon energy at the center of the Brillouin zone (ΔE = 83 meV) and a mean free path for phonon scattering (l = 35 Å) are given.