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Title: Size dependence of the bandgap of plasma synthesized silicon nanoparticles through direct introduction of sulfur hexafluoride

Developing silicon nanoparticle (SiNP) synthesis techniques that allow for straightforward control of nanoparticle size and associated optical properties is critical to potential applications of these materials. In addition, it is, in general, hard to probe the absorption threshold in these materials due to silicon's low absorption coefficient. In this study, size is controlled through direct introduction of sulfur hexafluoride (SF{sub 6}) into the dilute silane precursor of plasma synthesized SiNPs. Size reduction by nearly a factor of two with high crystallinity independent of size is demonstrated. The optical absorption spectra of the SiNPs in the vicinity of the bandgap are measured using photothermal deflection spectroscopy. Bandgap as a function of size is extracted taking into account the polydispersity of the samples. A systematic blue shift in absorption edge due to quantum confinement in the SiNPs is observed with increasing flow of SF{sub 6}. Photoluminescence (PL) spectra show a similar blue shift with size. However, a ∼300 meV difference in energy between emission and absorption for all sizes suggests that PL emission involves a defect related process. This shows that, while PL may allow size-induced shifts in the bandgap of SiNPs to be monitored, it cannot be relied on to give anmore » accurate value for the bandgap as a function of size.« less
Authors:
; ; ; ; ;  [1] ;  [2] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [2]
  1. Department of Physics, Colorado School of Mines, Golden, Colorado 80401 (United States)
  2. (United States)
  3. Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401 (United States)
  4. Renewable Energy Materials Research Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401 (United States)
Publication Date:
OSTI Identifier:
22485947
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 16; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ABSORPTION SPECTRA; CONFINEMENT; MATERIALS; MEV RANGE 100-1000; NANOPARTICLES; OPTICAL PROPERTIES; PHOTOLUMINESCENCE; PLASMA; PRECURSOR; SILANES; SILICON; SULFUR FLUORIDES