Journal
NANOTECHNOLOGY
Volume 29, Issue 35, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1361-6528/aac9ef
Keywords
silicon nanocrystals; photoluminescence; surface functionalization; conjugated surface groups; in-gap states; scanning tunneling microscopy/spectroscopy; quantum dots
Funding
- DFG IRTG [2022]
- NSERC CREATE programs
- NSERC DG program
- Studienstiftung des Deutschen Volkes
- AITF
- ISF [661/16]
- Harry de Jur Chair in Applied Science
- Enrique Berman Chair in Solar Energy Research
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Developing new methods, other than size and shape, for controlling the optoelectronic properties of semiconductor nanocrystals is a highly desired target. Here we demonstrate that the photoluminescence (PL) of silicon nanocrystals (SiNCs) can be tuned in the range 685-800 nm solely via surface functionalization with alkynyl(aryl) (phenylacetylene, 2-ethynylnaphthalene, 2-ethynyl-5-hexylthiophene) surface groups. Scanning tunneling microscopy/spectroscopy on single nanocrystals revealed the formation of new in-gap states adjacent to the conduction band edge of the functionalized SiNCs. PL red-shifts were attributed to emission through these in-gap states, which reduce the effective band gap for the electron-hole recombination process. The observed in-gap states can be associated with new interface states formed via (-Si-C C-) bonds in combination with conjugated molecules as indicated by ab initio calculations. In contrast to alkynyl(aryl)s, the formation of in-gap states and shifts in PL maximum of the SiNCs were not observed with aryl (phenyl, naphthalene, 2-hexylthiophene) and alkynyl (1-dodecyne) surface groups. These outcomes show that surface functionalization with alkynyl(aryl) molecules is a valuable tool to control the electronic structure. and optical properties of SiNCs via tuneable interface states, which may enhance the performance of SiNCs in semiconductor devices.
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