Electrical properties of junctions between Hg and Si(111) surfaces functionalized with short-chain alkyls

Stephen Maldonado, Katherine E. Plass, David Knapp, Nathan S Lewis

Research output: Contribution to journalArticle

64 Citations (Scopus)

Abstract

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 (C nH 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.

Original languageEnglish
Pages (from-to)17690-17699
Number of pages10
JournalJournal of Physical Chemistry C
Volume111
Issue number48
DOIs
Publication statusPublished - Dec 6 2007

Fingerprint

Electric properties
electrical properties
Electron affinity
methylidyne
electron affinity
Oxides
Functional groups
Semiconductor junctions
dipoles
semiconductor junctions
oxides
alkylation
Alkylation
Electric potential
electric potential
Silicon
Photoelectron spectroscopy
Photoelectrons
Fermi level
Charge transfer

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Electrical properties of junctions between Hg and Si(111) surfaces functionalized with short-chain alkyls. / Maldonado, Stephen; Plass, Katherine E.; Knapp, David; Lewis, Nathan S.

In: Journal of Physical Chemistry C, Vol. 111, No. 48, 06.12.2007, p. 17690-17699.

Research output: Contribution to journalArticle

Maldonado, Stephen ; Plass, Katherine E. ; Knapp, David ; Lewis, Nathan S. / Electrical properties of junctions between Hg and Si(111) surfaces functionalized with short-chain alkyls. In: Journal of Physical Chemistry C. 2007 ; Vol. 111, No. 48. pp. 17690-17699.
@article{c16265305bca4e8db4b533c2ae1d6e24,
title = "Electrical properties of junctions between Hg and Si(111) surfaces functionalized with short-chain alkyls",
abstract = "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 (C nH 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.",
author = "Stephen Maldonado and Plass, {Katherine E.} and David Knapp and Lewis, {Nathan S}",
year = "2007",
month = "12",
day = "6",
doi = "10.1021/jp070651i",
language = "English",
volume = "111",
pages = "17690--17699",
journal = "Journal of Physical Chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "48",

}

TY - JOUR

T1 - Electrical properties of junctions between Hg and Si(111) surfaces functionalized with short-chain alkyls

AU - Maldonado, Stephen

AU - Plass, Katherine E.

AU - Knapp, David

AU - Lewis, Nathan S

PY - 2007/12/6

Y1 - 2007/12/6

N2 - 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 (C nH 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.

AB - 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 (C nH 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.

UR - http://www.scopus.com/inward/record.url?scp=37249035984&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=37249035984&partnerID=8YFLogxK

U2 - 10.1021/jp070651i

DO - 10.1021/jp070651i

M3 - Article

VL - 111

SP - 17690

EP - 17699

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 48

ER -