title: Origin of blue photoluminescence from colloidal silicon nanocrystals fabricated by femtosecond laser ablation in solution.
abstract: We present a detailed investigation into the origin of blue emission from colloidal silicon (Si) nanocrystals (NCs) fabricated by femtosecond laser ablation of Si powder in 1-hexene. High resolution transmission electron microscopy and Raman spectroscopy observations confirm that Si NCs with average size 2.7 nm are produced and well dispersed in 1-hexene. Fourier transform infrared spectrum and x-ray photoelectron spectra have been employed to reveal the passivation of Si NCs surfaces with organic molecules. On the basis of the structural characterization, UV-visible absorption, temperature-dependent photoluminescence (PL), time-resolved PL, and PL excitation spectra investigations, we deduce that room-temperature blue luminescence from colloidal Si NCs originates from the following two processes: (i) under illumination, excitons first form within colloidal Si NCs by direct transition at the X or Γ (Γ25 → Γ'2) point; (ii) and then some trapped excitons migrate to the surfaces of colloidal Si NCs and further recombine via the surface states associated with the Si-C or Si-C-H2 bonds.
authors.affiliation: College of Material Engineering, Shanghai University of Engineering Science, 333 Long Teng Road, Shanghai 201620, People's Republic of China.
authors.forename: H L
authors.initials: HL
authors.lastname: Hao
authors.forename: W S
authors.initials: WS
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: L K
authors.initials: LK
authors.lastname: Wu
authors.forename: W Z
authors.initials: WZ
authors.lastname: Shen