96 research outputs found
Direct bandgap silicon quantum dots achieved via electronegative capping
We propose a novel concept of achieving silicon quantum dots with radiative
rates enhanced by more than two orders of magnitude up to the values
characteristic for direct band gap semiconductors. Our tight-binding
simulations show how the surface engineering can dramatically change the
density of confined electrons in real- and -space and give rise to the new
conduction band levels in -valley, thus promoting the direct radiative
transitions. The effect may be realized by covering the silicon dots with
covalently bonded electronegative ligands, such as alkyl or teflon chains
and/or by embedding in highly electronegative medium.Comment: 5 pages, 3 figures+ Supplementary Material
Fluorescent Silicon Clusters and Nanoparticles
The fluorescence of silicon clusters is reviewed. Atomic clusters of silicon
have been at the focus of research for several decades because of the relevance
of size effects for material properties, the importance of silicon in
electronics and the potential applications in bio-medicine. To date numerous
examples of nanostructured forms of fluorescent silicon have been reported.
This article introduces the principles and underlying concepts relevant for
fluorescence of nanostructured silicon such as excitation, energy relaxation,
radiative and non-radiative decay pathways and surface passivation.
Experimental methods for the production of silicon clusters are presented. The
geometric and electronic properties are reviewed and the implications for the
ability to emit fluorescence are discussed. Free and pure silicon clusters
produced in molecular beams appear to have properties that are unfavourable for
light emission. However, when passivated or embedded in a suitable host, they
may emit fluorescence. The current available data show that both quantum
confinement and localised transitions, often at the surface, are responsible
for fluorescence. By building silicon clusters atom by atom, and by embedding
them in shells atom by atom, new insights into the microscopic origins of
fluorescence from nanoscale silicon can be expected.Comment: 5 figures, chapter in "Silicon Nanomaterials Sourcebook", editor
Klaus D. Sattler, CRC Press, August 201
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