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Electrical Properties of Junctions between Hg and Si(111) Surfaces Functionalized with Short-Chain Alkyls

Maldonado, Stephen and Plass, Katherine E. and Knapp, David and Lewis, Nathan S. (2007) Electrical Properties of Junctions between Hg and Si(111) Surfaces Functionalized with Short-Chain Alkyls. Journal of Physical Chemistry C, 111 (48). pp. 17690-17699. ISSN 1932-7447. doi:10.1021/jp070651i.

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Metal−semiconductor junctions between Hg and chemically modified n- and p-Si(111) surfaces have been prepared and analyzed using current−voltage and differential capacitance−voltage methods. To understand the role of the interfacial dipole on interfacial charge transfer, silicon surfaces were modified with either nonstoichoimetric oxide (SiO_x), terminal monohydride, short (CnH_(2n+1)−, n = 1, 2, 3) saturated alkyl chains, or propynyl (CH_3−C≡C−) groups. X-ray photoelectron spectra of the modified Si electrode surfaces taken before and after exposure to Hg contacts showed no evidence of irreversible chemical interactions between the Si and the Hg. Hg/Si contacts made using H-terminated Si(111) surfaces exhibited Schottky junctions having barrier heights (Φ_b) that were consistent with the known surface electron affinity of Si and the work function of Hg. In contrast, Si coated with a thin, chemically grown oxide formed Hg/Si junctions having barrier heights suggestive of Fermi level pinning. Si(111) surfaces modified with methyl groups yielded Hg junctions having barrier heights in accord with expectations based on the electron affinity (3.67 eV) and surface dipole (0.38 eV) measured on such surfaces by photoemission spectroscopy, attesting to the degree of chemical control that can be exerted over the barrier heights of such systems by surface functionalization methods. Incomplete coverages of functional groups produced by alkylation with ethyl or iso-propyl groups did not greatly impact the observed values of Φ_b relative to Φ_b values observed for CH_3-terminated Si(111) surfaces. However, the observed variation in Φ_b between nominally identical samples increased as the number of carbons in the functionalizing alkyl group increased. Junctions between Hg and Si(111) surfaces modified with propynyl groups showed nearly identical behavior to that of CH_3−Si(111)/Hg contacts, both in average Φ_b values and standard deviation between samples. The behavior of Si/Hg interfaces modified with short organic functional groups is consistent with the efficacy and utility of passivated surfaces in modifying the properties of surface-based Si devices.

Item Type:Article
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URLURL TypeDescription Information
Maldonado, Stephen0000-0002-2917-4851
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2007 American Chemical Society. Received 25 January 2007. Published online 1 September 2007. Published in print 1 December 2007. We acknowledge the National Science Foundation, grant No. CHE-0604894, for support of this work. S.M. also acknowledges financial support from the Ford Foundation, through the National Academy of Sciences.
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Ford FoundationUNSPECIFIED
Issue or Number:48
Record Number:CaltechAUTHORS:20170614-082600888
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Official Citation:Electrical Properties of Junctions between Hg and Si(111) Surfaces Functionalized with Short-Chain Alkyls Stephen Maldonado, Katherine E. Plass, David Knapp, and Nathan S. Lewis The Journal of Physical Chemistry C 2007 111 (48), 17690-17699 DOI: 10.1021/jp070651i
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78190
Deposited By: Ruth Sustaita
Deposited On:14 Jun 2017 16:04
Last Modified:15 Nov 2021 17:37

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