Effect of Surface Passivation on Stability of Luminescence from Nanocrystalline Silicon Particles in Pure Water

Abstract

ABSTRACTWe have investigated the stability of luminescence in pure water from a nanocrystalline silicon (nc-Si) particles passivated with various chemical elements such as a hydrogen, carbon and oxygen atoms. Each sample emitted red light with a peak wavelength in a range from 690 to 800 nm. When the hydrogen- and/or carbon-passivated samples were immersed in pure water, the intensity of red luminescence was decreased by aging after a short period of time. At the same time, the peak wavelength was also shifted toward shorter wavelength. These were caused by the generation of defects (Pb-centers) and the reduction of particle size due to the desorption of hydrogen and/or carbon atoms and the replacement from the Si-H and/or Si-C bonds to the Si-O bond, respectively, at the surface of nc-Si particles. On the other hand, the oxygen-passivated sample showed stable luminescence in addition to the slight blue-shift of peak wavelength under the immersion in pure water for 400 hours. The good stability was attributed to the formation of stable surface condition. These results are a strong indication that the stability of the luminescence in pure water can be remarkably improved by the oxygen-passivation to the surface of nc-Si particles.