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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 (SF6) 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. 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 inabsorption edge due to quantum confinement in the SiNPs is observed with increasing flow of SF6. 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. While PL may allow size-induced shifts in the bandgap of SiNPs to be monitored, it cannot be relied on to give an accurate value for the bandgap asmore » a function of size.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [1]
  1. Colorado School of Mines, Golden, CO (United States)
  2. Colorado School of Mines, Golden, CO (United States); Michigan Technological Univ., Houghton, MI (United States)
  3. Colorado School of Mines, Golden, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
OSTI Identifier:
1229545
Report Number(s):
NREL/JA-5J00-65505
Journal ID: ISSN 0003-6951
DOE Contract Number:
AC36-08GO28308
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 16; Related Information: Applied Physics Letters
Research Org:
NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE silicon; band gap; x-ray diffraction; optical absorption; phototherma spectroscopy