Electron spin resonance study of defects in Si1-xGex alloy nanocrystals embedded in SiO2 matrices: Mechanism of luminescence quenching

摘要

Dangling bond defects in Si1-xGex alloy nanocrystals (nc-Si1-xGex) as small as 4 nm in diameter embedded in SiO2 thin films were studied by electron spin resonance (ESR), and the effects of the defects on photoluminescence (PL) properties were discussed. It was found that the ESR spectrum is a superposition of signals from Si and Ge dangling bonds at the interfaces between nc-Si1-xGex and SiO2 matrices (Si and Ge P-b centers). As the Ge concentration increased, the signal from the Ge P-b centers increased, while that from the Si P-b centers was nearly independent of Ge concentration. The increase in the number of Ge P-b centers was accompanied by strong quenching of the PL. The observed correlation between the two measurements suggests that the Ge P-b centers act as efficient nonradiative recombination centers for photogenerated carriers, resulting in the quenching of the main PL. (C) 2001 American Institute of Physics. References: 24