Free carriers reactivation on p+-mesoporous silicon through ammonia adsorption: a FTIR study

Interaction at room temperature of ammonia with porous silicon (PS) causes a loss of transparency of the sample to the IR radiation: the spectra in such conditions show a Drude-like behaviour indicating the presence of carriers. When ammonia is outgassed the original sample transparency is restored. The same phenomenon, when measured at low temperature, was previously interpreted in a way similar to that proposed for polar liquids by Timoshenko et al. [Phys. Stat. Solidi A 182 (1990) 1046], i.e. to be related to a change in the dielectric constant into the PS voids. At room temperature, any formation of liquid or dense phase can be ruled out.