Blue electroluminescence of ytterbium clusters in SiO2 by co-operative up-conversion.

Metal-oxynitride-oxide-silicon (MONOS) structures containing SiO2 layer implanted with different concentrations of ytterbium atoms were investigated. The electroluminescence (EL) measurements show that the MONOS:Yb devices can operate as blue or near infrared light emitters depending on the Yb concentration and annealing time. For an Yb concentration of up to 1.5% and annealing times of 30 min the near infrared EL with a peak at 975 nm corresponding to the 2F5/2→2F7/2 transition dominates. The short time annealed (6 s) sample containing 3% of Yb atoms exhibits mainly the blue EL due to co-operative up-conversion emission in the Yb3+-Yb3+ system. An enhancement of the red EL at 650 nm due to up-conversion energy transfer from the 2F5/2 excited state to the nonbridging oxygen hole center (NBOHC) is also presented.