The excitation power density effect on the Si nanocrystals photoluminescence

Abstract: In the present work we have studied the photoluminescence (PL) behavior from Si nanocrystals (NCs) as a function of the excitation power density and annealing time. The NCs were produced in a SiO2 matrix by Si implantations from room temperature (RT) up to 700°C, followed by post-annealing in N2 atmosphere at high temperature. With this aim we have changed the excitation power density (from 2×10−3 W/cm2 up to 15W/cm2) and the annealing time (from 10min up to 15h). The strong PL signal, which at 15W/cm2 is composed by a single-peak structure (650–1000nm) centered at around 780nm, expands up to 1200nm showing a two-peak structure when measured at 20×10−3 W/cm2. The peak structure located at the short wavelength side is kept at ∼780nm, while the second peak, starting at around 900nm, redshifts and increases its intensity with the implantation temperature and annealing time. The effect of the annealing time on the PL spectra behavior measured at low excitation power agrees by the first time with the Si NC growth according to quantum confinement effects. [Copyright &y& Elsevier]