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Published January 20, 2005 | public
Journal Article

Low-Temperature STM Images of Methyl-Terminated Si(111) Surfaces


Low-temperature scanning tunneling microscopy (STM) has been used to image CH3-terminated Si(111) surfaces that were prepared through a chlorination/alkylation procedure. The STM data revealed a well-ordered structure commensurate with the atop sites of an unreconstructed 1 × 1 overlayer on the silicon (111) surface. Images collected at 4.7 K revealed bright spots, separated by 0.18 ± 0.01 nm, which are assigned to adjacent H atoms on the same methyl group. The C−H bonds in each methyl group were observed to be rotated by 7 ± 3° away from the center of an adjacent methyl group and toward an underlying Si atom. Hence, the predominant interaction that determines the surface structure arises from repulsions between hydrogen atoms on neighboring methyl groups, and secondary interactions unique to the surface are also evident.

Additional Information

© 2005 American Chemical Society. Received 28 May 2004. Published online 16 September 2004. Published in print 1 January 2005. We acknowledge the National Science Foundation, grant CHE-0213589 (N.S.L.), the DARPA Molectronics Program, and the MARCO Materials Structures and Devices Focus Center (J.R.H. and W.A.G.) for their support of this research. L.J.W. thanks the NSF for a graduate fellowship, and we are grateful to L. Henling for assistance with the X-ray diffraction experiments.

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