Nov 9, 2015
White light emission from a Si nanocrystal thin film
Si nanocrystals (Si-NCs) are a promising material for Si light sources which are of key importance for integrated Si optoelectronics. They are receiving a lot of interest concerning enhancements of their light emissions and optical gains. Reporting in Nanotechnology, researchers prepare a Si-NC thin film that can emit broadband photoluminescence (PL) from the blue to red region and show positive optical gains for its red, green and blue (RGB) components. The results suggest potential for application in white-light Si lasing and Si lighting.
Si nanocrystals with an average size Ø = 2.31 ± 0.35 nm are prepared by chemical etching of Si powder. After being mixed with SiO2 sol-gel (SOG) and thermally annealed, a broadband photoluminescence from the thin film of Si nanocrystals in SOG is observed. The RGB ratio of the PL (1.00/3.26/4.59 for the pure white light emission) can be tuned by changing the annealing temperature or atmosphere.
The optical gains of Si nanocrystals in SOG are measured by variable stripe length (VSL) and shifting excitation spot (SES) methods for the four components (λ = 400, 490, 560, 620 nm) of PL. Positive optical gains are obtained, which are 117.49, 123.20, 94.57, 89.93 cm-1 respectively.
It is established that the light emission from Si nanocrystals is related to their interfacial states whilst theoretical calculations suggest that the number of Si and O bond determines the wavelength of light emission. With white light emission and positive optical gains for the RGB components under ultraviolet excitation, Si nanocrystals in SOG have potential in white-light Si lasing and Si lighting.
More information about this research can be found in the journal Nanotechnology 26 475203.
About the author
Dong-Chen Wang is a PhD student with Department of Optical Science and Engineering, Fudan University, Shanghai, China. He received his Bachelor of Science degree from Department of Optical Science and Information, Shandong University in 2012. Ming Lu is a Professor within the Department of Optical Science and Engineering, Fudan University, Shanghai, China. He obtained his PhD degree from Physics Department, Fudan University in 1992. His research interest is in Si light emission and photovoltaics.