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Control of the Band-Edge Positions of Crystalline Si(111) by Surface Functionalization with 3,4,5-Trifluorophenylacetylenyl Moieties

Plymale, Noah T. and Ramachandran, Anshul A. and Lim, Allison and Brunschwig, Bruce S. and Lewis, Nathan S. (2016) Control of the Band-Edge Positions of Crystalline Si(111) by Surface Functionalization with 3,4,5-Trifluorophenylacetylenyl Moieties. Journal of Physical Chemistry C, 120 (26). pp. 14157-14169. ISSN 1932-7447. doi:10.1021/acs.jpcc.6b03824.

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Functionalization of semiconductor surfaces with organic moieties can change the charge distribution, surface dipole, and electric field at the interface. The modified electric field will shift the semiconductor band-edge positions relative to those of a contacting phase. Achieving chemical control over the energetics at semiconductor surfaces promises to provide a means of tuning the band-edge energetics to form optimized junctions with a desired material. Si(111) surfaces functionalized with 3,4,5-trifluorophenylacetylenyl (TFPA) groups were characterized by transmission infrared spectroscopy (TIRS), X-ray photoelectron spectroscopy (XPS), and surface recombination velocity (S) measurements. Mixed methyl/TFPA-terminated (MMTFPA) n- and p-type Si(111) surfaces were synthesized and characterized by electrochemical methods. Current density versus voltage and Mott-Schottky measurements of Si(111)–MMTFPA electrodes in contact with Hg indicated that the barrier height, Φb, was a function of the fractional monolayer coverage of TFPA (θTFPA) in the alkyl monolayer. Relative to Si(111)–CH3 surfaces, Si(111)–MMTFPA samples with high θTFPA produced shifts in Φb of ≥0.6 V for n-Si/Hg contacts and ≥0.5 V for p-Si/Hg contacts. Consistently, the open-circuit potential (Eoc) of Si(111)–MMTFPA samples in contact with CH3CN solutions that contained the 1-electron redox couples decamethylferrocenium/decamethylferrocene (Cp*2Fe+/0) or methyl viologen (MV2+/+●) shifted relative to Si(111)–CH3 samples by +0.27 V for n-Si and by up to +0.10 V for p-Si. Residual surface recombination limited the Eoc of p-Si samples at high θTFPA despite the favorable shift in the band-edge positions induced by the surface modification process.

Item Type:Article
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URLURL TypeDescription Information
Plymale, Noah T.0000-0003-2564-8009
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2016 American Chemical Society. Received: April 14, 2016; Revised: June 1, 2016; Published: June 3, 2016. We acknowledge the National Science Foundation Grant No. CHE-1214152 for support of supplies and equipment for this work. Instrumentation support was provided by the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology. N.T.P. acknowledges support from a National Science Foundation Graduate Research Fellowship. B.S.B. and N.T.P. acknowledge support from the National Science Foundation CCI Solar Fuels Program under Grant No. CHE-1305124. N.S.L. acknowledges support from a National Science Foundation Grant No. CHE-1214152. We thank Dr. Adam C. Nielander, Mr. Christopher W. Roske, and Dr. Kimberly M. Papadantonakis for helpful discussions.
Group:CCI Solar Fuels
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Issue or Number:26
Record Number:CaltechAUTHORS:20160609-154706514
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Official Citation:Control of the Band-Edge Positions of Crystalline Si(111) by Surface Functionalization with 3,4,5-Trifluorophenylacetylenyl Moieties Noah T. Plymale, Anshul A. Ramachandran, Allison Lim, Bruce S. Brunschwig, and Nathan S. Lewis The Journal of Physical Chemistry C 2016 120 (26), 14157-14169 DOI: 10.1021/acs.jpcc.6b03824
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67805
Deposited By: Ruth Sustaita
Deposited On:10 Jun 2016 15:03
Last Modified:11 Nov 2021 03:54

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