Excitation and non-radiative de-excitation processes in Er-doped Si nanocrystals

Our recent work on the interaction among Er ions and Si nanocrystals (nc) is presented. Silicon nanocrystals embedded within SiO2 were produced by plasma enhanced chemical vapor deposition followed by high temperature annealing. Erbium ions were then introduced at different concentrations by implantation and a final annealing at 900°C was performed to eliminate the implantation damage. These samples exhibit a room temperature photoluminescence (PL) orders of magnitude higher than both Er in SiO2 and in crystalline Si. A detailed study of the excitation and de-excitation processes demonstrated that Er is efficiently excited through an exciton recombination in the nc which act as sensitizers for the Er excitation. Indeed, when an Er ion is located close by a nc will become dark transferring preferentially its energy to it. An effective cross-section for Er excitation through this process has been determined to be ∼1×10−16 cm2, a value orders of magnitude above that of Er in insulating hosts. Moreover, the de-excitation processes typically present for Er in crystalline Si are absent in this case. We have identified the concentration quenching and the Auger interaction of excited Er ions with excited nc as the main non-radiative de-excitation processes. These data will be presented and their implications discussed.