Size-dependent effect of energy transfer on photoluminescence from Si nanocrystals in close proximity with ZnO films

摘要

300 nm SiO_x layers grown on p-type (100) Si wafer have been annealed to form Si nanocrystals (NCs) within SiO_2.100 nm ZnO films have been then deposited on top of the SiO_2:Si NC layers and annealed to form hybrid structures of ZnO/Si NCs. The PL_(si) (photoluminescence from Si NCs) intensity of the hybrid structures increases almost linearly with decreasing size of Si NCs (d_(Si)) from 3.8 to 2.0 nm, whilst the PL_(zno) (PL from ZnO) gradually increases down to d_(si) = ～2.5 nm and then sharply decreases. In the SiO_2:Si NC layers without ZnO, the PL_(si) intensity sharply increases to a maximum at d_(si) = -2.5 nm, and by further decrease of d_(Si), it decreases. These results suggest that the energy transfer from Si NCs to ZnO occurred in the range of d_(si) = 3.8 to ～2.5 nm and vice versa below d_(Si) = ～2.5 nm.