Abstract :
The electrical and optical properties of porous silicon layers deposited on silicon substrates are determined by their
electrochemical preparation conditions. Porous silicon layers (PSL) deposited on low resistivity (10m3 R cm) boron doped
p+ Si exhibits channel structure, whereas layers formed on p type (l-3 n cm) Si wafers are sponge type. In the abundant
literature on PSL, little attention was paid to their electron spectra. We presented in this paper, a study of p+ and p type PSL
samples by elastic peak electron spectroscopy (EPES). The elastic reflection coefficient r&E, P) is strongly affected by
physical parameters of the sample as the porosity, the substrate Si type as well the presence of H adatoms within the pores.
r,(E, P) spectra are measured in absolute units (%) with a retarding field analyzer. A general tendency of spectra was the
decrease of intensity with P (porosity) and E (primary electron energy). We have observed that HF treatment of the samples
is producing a dramatic decrease of re,(E, P) in the low energy range (E = 50-150 eV). r&E, P) intensities were
measured at E = 50, 100 and 150 eV. We observed that the excess reflection (coming from the pores sides) becomes
important for porosity P > 0.6. A phenomenological model is presented based on the intact Si surface and reflection of
electrons from the pores.
