Ultrafast photoluminescence in silicon nanocrystals studied by femtosecond up-conversion technique

Abstract

Photoluminescence dynamics in silicon nanocrystals measured by a femtosecond up-conversion technique are reported. The samples were prepared by embedding porous silicon grains in a sol-gel derived SiO2 matrix. Efficient initial relaxation of the excess energy of photoexcited carriers with the effective rate ⩾3.8eV∕ps was observed. A fast decay component (400fs) of the photoluminescence signal was found and interpreted in terms of quenching the interior exciton radiative recombination by carrier trapping on the nanocrystal surface. The ultrafast photoluminescence dynamics are followed by a microsecond decay of the stretched-exponential type.