Functional properties of silicon nanocrystals in oxygen-rich amorphous matrices formed by laser irradiation of substoichiometric silicon oxides

Abstract

Silicon-based nanostructured thin films have been obtained through laser irradiation of amorphous silicon oxides. The optoelectronic properties of nanostructured films largely differ from their amorphous counterpart, exhibiting optical gap narrowing, wavelength-dependent spectral modification of the photoluminescence (PL) and conduction mechanism variations. In particular, following the hydrogen effusion and related defect density increase, a spectral red shift and PL intensity quenching is detected for λ exc=514.5 nm, whereas PL enhancement and spectral blue shift is observed at λ exc=632.8 nm. Different thermal activation regimes of conductivity are also detected by conductivity measurements. Such results are discussed in terms of microstructural changes from an hydrogenated amorphous network to a nanostructured two-phase material where wavelength-selective excitation of radiative recombination channels and temperature-dependent conductivity paths occurs.