Correlation between surface composition and luminescence of nanocrystalline silicon particles dispersed in pure water

Abstract

The stability of the luminescene of nanocrystalline silicon (nc-Si) particles passivated with a number of different elements, including hydrogen, carbon, and oxygen, has been investigated in pure water. Each sample emitted red light with a peak wavelength in the range of 740–800nm. The intensity of red luminescence decreased after a short period of time when the hydrogen- and/or carbon-passivated samples were immersed in pure water. Further, the peak wavelength concomitantly shifted toward a shorter wavelength. These effects were attributed to the generation of defects (Pb centers), the reduction in particle size due to the desorption of hydrogen and/or carbon atoms, and the replacement of the Si–H and/or Si–C bonds, respectively, with Si-O bonds on the surface of nc-Si particles. On the other hand, the oxygen-passivated samples showed stable luminescence in addition to a slight blueshift of the peak wavelength upon immersion in pure water for 400h. This stability was attributed to the development of stable surface conditions. These results are a strong indication that the stability of luminescence in pure water can be remarkably improved by oxygen passivation on the surface of nc-Si particles.