Size dependence of Pb-type photoluminescence quenching defects at the Si nanocrystal interface

Size-controlled Si nanocrystals (nc's) of ∼ 2 to 5 nm diameter embedded in amorphous (a-)SiO2 are extensively studied by electron spin resonance (ESR) and photoluminescence (PL). The PL quenching Pb-type (Si dangling bond) interface defects ––Pb(0) and Pb1 centers–– are investigated as a function of Si nc's size and effective interface area with the embedding SiO2. It is shown that the effective areal Pb-type defect density at the nc-Si/SiO2 interface remains approximately constant, indifferent of the nc size. While Si nc's larger than ≈3.5 nm are found to house, on average, at least one PL quenching Pb-type defect, about 75% of the as-annealed 2 nm Si nc's appear Pb-free. Additional study on the effect of heat treatment in H2 indicates this step to be more efficient in inactivating Pb(0) than Pb1 for all Si nc sizes.