Er3+ luminescence and cooperative upconversion in ErxY2-xSiO5 nanocrystal aggregates fabricated using Si nanowires

Er3+ luminescence and cooperative upconversion in ErxY2-xSiO5 nanocrystal aggregates fabricated using Si nanowires is investigated. X-ray diffraction and photoluminescence spectroscopy indicate that the composition of the final nanocrystals can be varied continuously from pure Y2SiO5 to pure Er2SiO5 while keeping the crystal structure the same. Analysis of concentration and pump-power dependence of the Er3+ photoluminescence intensity and decay time shows that while cooperative upconversion occurs at high Er concentrations, the cooperative upconversion coefficient is only (2.2 +/- 1.1) x 10(-18) cm(3)/s at a Er concentration of 1.2 x 10(21) cm(-3). This is nearly ten times lower at more than ten times higher Er concentration than that reported from Er-doped silica and demonstrates the viability of using such silicates for compact, high-gain Si-based optical material for Si photonics. (c) 2008 American Institute of Physics.