Dangling bond defects in SiGe nanocrystals (as small as 4nm in diameter), embedded in SiO2 thin films, were studied by using electron spin resonance. It was found that the electron spin resonance spectrum was the superposition of signals from Si and Ge dangling bonds at the interfaces between the nanocrystals and the SiO2 matrix (Si and Ge Pb centres). As the Ge concentration was increased, the signal from the Ge Pb centres increased while that from the Si Pb centres was almost independent of the Ge concentration. The increase in the number of Ge Pb centres was associated with strong quenching of the photoluminescence. An observed correlation between the 2 measurements suggested that the Ge Pb centres acted as efficient non-radiative recombination centres for photogenerated carriers; resulting in the quenching of the main photoluminescence.

Electron Spin Resonance Study of Defects in Si1-xGex Alloy Nanocrystals Embedded in SiO2 Matrices: Mechanism of Luminescence Quenching. K.Toshikiyo, M.Tokunaga, S.Takeoka, M.Fujii, S.Hayashi: Journal of Applied Physics, 2001, 89[9], 4917-20