Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

Hadas Alon; Rachel Garrick; Sidharam P. Pujari; Tal Toledano; Ofer Sinai; Nir Kedem; Tatyana Bendikov; Joe E. Baio; Tobias Weidner; Han Zuilhof; David Cahen; Leeor Kronik; Chaim N. Sukenik; Ayelet Vilan

doi:10.1021/acs.jpcc.7b09118

Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

Hadas Alon, Rachel Garrick, Sidharam P. Pujari, Tal Toledano, Ofer Sinai, Nir Kedem, Tatyana Bendikov, Joe E. Baio, Tobias Weidner, Han Zuilhof, David Cahen, Leeor Kronik^*, Chaim N. Sukenik, Ayelet Vilan

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

9 Citations (Scopus)

Abstract

Molecular monolayers at metal/semiconductor heterointerfaces affect electronic energy level alignment at the interface by modifying the interface's electrical dipole. On a free surface, the molecular dipole is usually manipulated by means of substitution at its external end. However, at an interface such outer substituents are in close proximity to the top contact, making the distinction between molecular and interfacial effects difficult. To examine how the interface dipole would be influenced by a single atom, internal to the molecule, we used a series of three molecules of identical binding and tail groups, differing only in the inner atom: aryl vinyl ether (PhO), aryl vinyl sulfide (PhS), and the corresponding molecule with a CH₂ group - allyl benzene (PhC). Molecular monolayers based on all three molecules have been adsorbed on a flat, oxide-free Si surface. Extensive surface characterization, supported by density functional theory calculations, revealed high-quality, well-aligned monolayers exhibiting excellent chemical and electrical passivation of the silicon substrate, in all three cases. Current-voltage and capacitance-voltage analysis of Hg/PhX (X = C, O, S)/Si interfaces established that the type of internal atom has a significant effect on the Schottky barrier height at the interface, i.e., on the energy level alignment. Surprisingly, despite the formal chemical separation of the internal atom and the metallic electrode, Schottky barrier heights were not correlated to changes in the semiconductor's effective work function, deduced from Kelvin probe and ultraviolet photoemission spectroscopy on the monolayer-adsorbed Si surface. Rather, these changes correlated well with the ionization potential of the surface-adsorbed molecules. This is interpreted in terms of additional polarization at the molecule/metal interface, driven by potential equilibration considerations even in the absence of a formal chemical bond to the top Hg contact.

Original language	English
Journal	Journal of Physical Chemistry C
Volume	122
Issue	6
Pages (from-to)	3312-3325
Number of pages	14
ISSN	1932-7447
DOIs	https://doi.org/10.1021/acs.jpcc.7b09118
Publication status	Published - 15 Feb 2018

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Alon, H., Garrick, R., Pujari, S. P., Toledano, T., Sinai, O., Kedem, N., Bendikov, T., Baio, J. E., Weidner, T., Zuilhof, H., Cahen, D., Kronik, L., Sukenik, C. N., & Vilan, A. (2018). Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces. Journal of Physical Chemistry C, 122(6), 3312-3325. https://doi.org/10.1021/acs.jpcc.7b09118

@article{602a47ef520f4ed89de1339ecbe26884,

title = "Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces",

abstract = "Molecular monolayers at metal/semiconductor heterointerfaces affect electronic energy level alignment at the interface by modifying the interface's electrical dipole. On a free surface, the molecular dipole is usually manipulated by means of substitution at its external end. However, at an interface such outer substituents are in close proximity to the top contact, making the distinction between molecular and interfacial effects difficult. To examine how the interface dipole would be influenced by a single atom, internal to the molecule, we used a series of three molecules of identical binding and tail groups, differing only in the inner atom: aryl vinyl ether (PhO), aryl vinyl sulfide (PhS), and the corresponding molecule with a CH2 group - allyl benzene (PhC). Molecular monolayers based on all three molecules have been adsorbed on a flat, oxide-free Si surface. Extensive surface characterization, supported by density functional theory calculations, revealed high-quality, well-aligned monolayers exhibiting excellent chemical and electrical passivation of the silicon substrate, in all three cases. Current-voltage and capacitance-voltage analysis of Hg/PhX (X = C, O, S)/Si interfaces established that the type of internal atom has a significant effect on the Schottky barrier height at the interface, i.e., on the energy level alignment. Surprisingly, despite the formal chemical separation of the internal atom and the metallic electrode, Schottky barrier heights were not correlated to changes in the semiconductor's effective work function, deduced from Kelvin probe and ultraviolet photoemission spectroscopy on the monolayer-adsorbed Si surface. Rather, these changes correlated well with the ionization potential of the surface-adsorbed molecules. This is interpreted in terms of additional polarization at the molecule/metal interface, driven by potential equilibration considerations even in the absence of a formal chemical bond to the top Hg contact.",

author = "Hadas Alon and Rachel Garrick and Pujari, {Sidharam P.} and Tal Toledano and Ofer Sinai and Nir Kedem and Tatyana Bendikov and Baio, {Joe E.} and Tobias Weidner and Han Zuilhof and David Cahen and Leeor Kronik and Sukenik, {Chaim N.} and Ayelet Vilan",

year = "2018",

month = feb,

day = "15",

doi = "10.1021/acs.jpcc.7b09118",

language = "English",

volume = "122",

pages = "3312--3325",

journal = "Journal of Physical Chemistry C",

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Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces. / Alon, Hadas; Garrick, Rachel; Pujari, Sidharam P. et al.
In: Journal of Physical Chemistry C, Vol. 122, No. 6, 15.02.2018, p. 3312-3325.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaper › Journal article › Research › peer-review

TY - JOUR

T1 - Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

AU - Alon, Hadas

AU - Garrick, Rachel

AU - Pujari, Sidharam P.

AU - Toledano, Tal

AU - Sinai, Ofer

AU - Kedem, Nir

AU - Bendikov, Tatyana

AU - Baio, Joe E.

AU - Weidner, Tobias

AU - Zuilhof, Han

AU - Cahen, David

AU - Kronik, Leeor

AU - Sukenik, Chaim N.

AU - Vilan, Ayelet

PY - 2018/2/15

Y1 - 2018/2/15

N2 - Molecular monolayers at metal/semiconductor heterointerfaces affect electronic energy level alignment at the interface by modifying the interface's electrical dipole. On a free surface, the molecular dipole is usually manipulated by means of substitution at its external end. However, at an interface such outer substituents are in close proximity to the top contact, making the distinction between molecular and interfacial effects difficult. To examine how the interface dipole would be influenced by a single atom, internal to the molecule, we used a series of three molecules of identical binding and tail groups, differing only in the inner atom: aryl vinyl ether (PhO), aryl vinyl sulfide (PhS), and the corresponding molecule with a CH2 group - allyl benzene (PhC). Molecular monolayers based on all three molecules have been adsorbed on a flat, oxide-free Si surface. Extensive surface characterization, supported by density functional theory calculations, revealed high-quality, well-aligned monolayers exhibiting excellent chemical and electrical passivation of the silicon substrate, in all three cases. Current-voltage and capacitance-voltage analysis of Hg/PhX (X = C, O, S)/Si interfaces established that the type of internal atom has a significant effect on the Schottky barrier height at the interface, i.e., on the energy level alignment. Surprisingly, despite the formal chemical separation of the internal atom and the metallic electrode, Schottky barrier heights were not correlated to changes in the semiconductor's effective work function, deduced from Kelvin probe and ultraviolet photoemission spectroscopy on the monolayer-adsorbed Si surface. Rather, these changes correlated well with the ionization potential of the surface-adsorbed molecules. This is interpreted in terms of additional polarization at the molecule/metal interface, driven by potential equilibration considerations even in the absence of a formal chemical bond to the top Hg contact.

AB - Molecular monolayers at metal/semiconductor heterointerfaces affect electronic energy level alignment at the interface by modifying the interface's electrical dipole. On a free surface, the molecular dipole is usually manipulated by means of substitution at its external end. However, at an interface such outer substituents are in close proximity to the top contact, making the distinction between molecular and interfacial effects difficult. To examine how the interface dipole would be influenced by a single atom, internal to the molecule, we used a series of three molecules of identical binding and tail groups, differing only in the inner atom: aryl vinyl ether (PhO), aryl vinyl sulfide (PhS), and the corresponding molecule with a CH2 group - allyl benzene (PhC). Molecular monolayers based on all three molecules have been adsorbed on a flat, oxide-free Si surface. Extensive surface characterization, supported by density functional theory calculations, revealed high-quality, well-aligned monolayers exhibiting excellent chemical and electrical passivation of the silicon substrate, in all three cases. Current-voltage and capacitance-voltage analysis of Hg/PhX (X = C, O, S)/Si interfaces established that the type of internal atom has a significant effect on the Schottky barrier height at the interface, i.e., on the energy level alignment. Surprisingly, despite the formal chemical separation of the internal atom and the metallic electrode, Schottky barrier heights were not correlated to changes in the semiconductor's effective work function, deduced from Kelvin probe and ultraviolet photoemission spectroscopy on the monolayer-adsorbed Si surface. Rather, these changes correlated well with the ionization potential of the surface-adsorbed molecules. This is interpreted in terms of additional polarization at the molecule/metal interface, driven by potential equilibration considerations even in the absence of a formal chemical bond to the top Hg contact.

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U2 - 10.1021/acs.jpcc.7b09118

DO - 10.1021/acs.jpcc.7b09118

M3 - Journal article

AN - SCOPUS:85042161787

SN - 1932-7447

VL - 122

SP - 3312

EP - 3325

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

IS - 6

ER -

Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

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