Atomic-scale X-ray structural analysis of self-assembled monolayers on silicon

J. C. Lin; J. A. Kellar; J. H. Kim; N. L. Yoder; K. H. Bevan; S. T. Nguyen; M. C. Hersam; M. J. Bedzyk

doi:10.1140/epjst/e2009-00933-8

Atomic-scale X-ray structural analysis of self-assembled monolayers on silicon

J. C. Lin, J. A. Kellar, J. H. Kim, N. L. Yoder, K. H. Bevan, S. T. Nguyen, M. C. Hersam, M. J. Bedzyk^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

Two related self-assembled monolayers (SAMs), 4-bromostyrene (BrSty) and 4-bromophenylacetylene (BPA), are photochemically grown from solution on to the monohydride-terminated Si(111) surface. The atomic-scale structures of the resulting SAMs are examined by X-ray standing waves (XSW), X-ray reflectivity (XRR), X-ray fluorescence, atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The coverage is 0.5 ML. The results show that in each case the molecule covalently bonds to a single Si T₁ site and stands up-right with a slight molecular tilt of 17° that leaves the Br terminal end over a neighboring T₄ site. The Br height is 8.5 Å (BrSty) and 8.6 Å (BPA) above the top surface Si atom. The combined XSW and XRR results rule-out two alternative bonding models predicted by DFT that have the root of the molecule bonded to two neighboring top Si surface atoms. Based on the XSW 111 and 333 coherent fractions, the BPA/Si(111) has a reduced vertical Br distribution width in comparison to BrSty. This greater rigidity in the molecular structure is correlated to a C=C bond at the root.

Original language	English (US)
Pages (from-to)	33-39
Number of pages	7
Journal	European Physical Journal: Special Topics
Volume	167
Issue number	1
DOIs	https://doi.org/10.1140/epjst/e2009-00933-8
State	Published - 2009

Funding

This work was supported by the Nanoscale Science and Engineering Initiative of the National Science Foundation (Award Numbers EEC-0118025 and ECS-0506802). The authors thank the DND-CAT staff and Jerrold Carsello of the NU X-ray Lab for technical assistance. Use of the APS at Argonne National Laboratory was supported by the DOE/BES under Contract No. DE-AC02-06CH11357. DND-CAT is supported in part by the State of Illinois. This work made use of NU Central Facilities supported by the MRSEC through NSF Contract No. DMR-0520513. Computational resources were provided by the National Science Foundation Network for Computational Nanotechnology.

ASJC Scopus subject areas

General Materials Science
General Physics and Astronomy
Physical and Theoretical Chemistry

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10.1140/epjst/e2009-00933-8

Cite this

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title = "Atomic-scale X-ray structural analysis of self-assembled monolayers on silicon",

abstract = "Two related self-assembled monolayers (SAMs), 4-bromostyrene (BrSty) and 4-bromophenylacetylene (BPA), are photochemically grown from solution on to the monohydride-terminated Si(111) surface. The atomic-scale structures of the resulting SAMs are examined by X-ray standing waves (XSW), X-ray reflectivity (XRR), X-ray fluorescence, atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The coverage is 0.5 ML. The results show that in each case the molecule covalently bonds to a single Si T1 site and stands up-right with a slight molecular tilt of 17° that leaves the Br terminal end over a neighboring T4 site. The Br height is 8.5 {\AA} (BrSty) and 8.6 {\AA} (BPA) above the top surface Si atom. The combined XSW and XRR results rule-out two alternative bonding models predicted by DFT that have the root of the molecule bonded to two neighboring top Si surface atoms. Based on the XSW 111 and 333 coherent fractions, the BPA/Si(111) has a reduced vertical Br distribution width in comparison to BrSty. This greater rigidity in the molecular structure is correlated to a C=C bond at the root.",

author = "Lin, {J. C.} and Kellar, {J. A.} and Kim, {J. H.} and Yoder, {N. L.} and Bevan, {K. H.} and Nguyen, {S. T.} and Hersam, {M. C.} and Bedzyk, {M. J.}",

note = "Funding Information: This work was supported by the Nanoscale Science and Engineering Initiative of the National Science Foundation (Award Numbers EEC-0118025 and ECS-0506802). The authors thank the DND-CAT staff and Jerrold Carsello of the NU X-ray Lab for technical assistance. Use of the APS at Argonne National Laboratory was supported by the DOE/BES under Contract No. DE-AC02-06CH11357. DND-CAT is supported in part by the State of Illinois. This work made use of NU Central Facilities supported by the MRSEC through NSF Contract No. DMR-0520513. Computational resources were provided by the National Science Foundation Network for Computational Nanotechnology.",

year = "2009",

doi = "10.1140/epjst/e2009-00933-8",

language = "English (US)",

volume = "167",

pages = "33--39",

journal = "European Physical Journal: Special Topics",

issn = "1951-6355",

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number = "1",

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T1 - Atomic-scale X-ray structural analysis of self-assembled monolayers on silicon

AU - Lin, J. C.

AU - Kellar, J. A.

AU - Kim, J. H.

AU - Yoder, N. L.

AU - Bevan, K. H.

AU - Nguyen, S. T.

AU - Hersam, M. C.

AU - Bedzyk, M. J.

N1 - Funding Information: This work was supported by the Nanoscale Science and Engineering Initiative of the National Science Foundation (Award Numbers EEC-0118025 and ECS-0506802). The authors thank the DND-CAT staff and Jerrold Carsello of the NU X-ray Lab for technical assistance. Use of the APS at Argonne National Laboratory was supported by the DOE/BES under Contract No. DE-AC02-06CH11357. DND-CAT is supported in part by the State of Illinois. This work made use of NU Central Facilities supported by the MRSEC through NSF Contract No. DMR-0520513. Computational resources were provided by the National Science Foundation Network for Computational Nanotechnology.

PY - 2009

Y1 - 2009

N2 - Two related self-assembled monolayers (SAMs), 4-bromostyrene (BrSty) and 4-bromophenylacetylene (BPA), are photochemically grown from solution on to the monohydride-terminated Si(111) surface. The atomic-scale structures of the resulting SAMs are examined by X-ray standing waves (XSW), X-ray reflectivity (XRR), X-ray fluorescence, atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The coverage is 0.5 ML. The results show that in each case the molecule covalently bonds to a single Si T1 site and stands up-right with a slight molecular tilt of 17° that leaves the Br terminal end over a neighboring T4 site. The Br height is 8.5 Å (BrSty) and 8.6 Å (BPA) above the top surface Si atom. The combined XSW and XRR results rule-out two alternative bonding models predicted by DFT that have the root of the molecule bonded to two neighboring top Si surface atoms. Based on the XSW 111 and 333 coherent fractions, the BPA/Si(111) has a reduced vertical Br distribution width in comparison to BrSty. This greater rigidity in the molecular structure is correlated to a C=C bond at the root.

AB - Two related self-assembled monolayers (SAMs), 4-bromostyrene (BrSty) and 4-bromophenylacetylene (BPA), are photochemically grown from solution on to the monohydride-terminated Si(111) surface. The atomic-scale structures of the resulting SAMs are examined by X-ray standing waves (XSW), X-ray reflectivity (XRR), X-ray fluorescence, atomic-force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The coverage is 0.5 ML. The results show that in each case the molecule covalently bonds to a single Si T1 site and stands up-right with a slight molecular tilt of 17° that leaves the Br terminal end over a neighboring T4 site. The Br height is 8.5 Å (BrSty) and 8.6 Å (BPA) above the top surface Si atom. The combined XSW and XRR results rule-out two alternative bonding models predicted by DFT that have the root of the molecule bonded to two neighboring top Si surface atoms. Based on the XSW 111 and 333 coherent fractions, the BPA/Si(111) has a reduced vertical Br distribution width in comparison to BrSty. This greater rigidity in the molecular structure is correlated to a C=C bond at the root.

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DO - 10.1140/epjst/e2009-00933-8

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SN - 1951-6355

VL - 167

SP - 33

EP - 39

JO - European Physical Journal: Special Topics

JF - European Physical Journal: Special Topics

IS - 1

ER -

Atomic-scale X-ray structural analysis of self-assembled monolayers on silicon

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