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Chemical, Electronic, and Electrical Properties of Alkylated Ge(111) Surfaces

Knapp, David and Brunschwig, Bruce S. and Lewis, Nathan S. (2010) Chemical, Electronic, and Electrical Properties of Alkylated Ge(111) Surfaces. Journal of Physical Chemistry C, 114 (28). pp. 12300-12307. ISSN 1932-7447. doi:10.1021/jp101375x.

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The use of Ge in semiconductor electronics has been constrained by the lack of a simple method of passivating the crystal surface. Toward that end, we have explored the utility of chemically bonded hydrocarbon monolayers. Alkylated Ge(111) surfaces have been prepared by addition of 1-alkenes to the H-terminated Ge(111) surface as well as by a two-step halogenation/alkylation procedure. The chemical compositions of the resulting methyl-, ethyl-, and decyl-terminated surfaces have been evaluated using X-ray photoelectron spectroscopy (XPS). Thermal addition of 1-decene produced hydrophobic surfaces with 0.3 ± 0.1 monolayer of Ge oxide detected by XPS, whereas no oxide was observed on the methyl-, ethyl-, or decyl-terminated surfaces that were prepared using the two-step halogenation/alkylation method. Methyl-terminated Ge(111) surfaces prepared by the two-step method displayed a well-resolved C 1s XPS peak at a binding energy of 284 eV, consistent with carbon bonded to a less electronegative element such as Ge. The electronic properties of all of the alkylated surfaces were characterized by measurements of the surface recombination velocity as a function of an externally applied gate voltage. Treatment of HF-etched Ge(111) surfaces with Br2 vapor, followed by reaction with alkylmagnesium or alkyllithium reagents, yielded air-stable surfaces that had surface recombination velocities of 100 cm s^(−1) or less under flat-band conditions. The field-dependent surface recombination velocity experiments indicated that, in contact with air, methyl-terminated n-type Ge(111) samples had a negative surface potential approaching 300 mV, in contrast to the oxidized Ge(111) surface, which exhibited a strongly positive surface potential under the same conditions. Mercury contacts to n-type methyl-, ethyl-, or decyl-terminated Ge(111) substrates that were alkylated using the two-step method formed rectifying junctions with barrier heights of 0.6 ± 0.1 eV, whereas no measurable rectification was observed for Hg contacts to p-type Ge(111) substrates that were alkylated by the two-step method, to n-type Ge(111) substrates that were alkylated through addition of 1-decene, or to oxidized n-type Ge(111) samples.

Item Type:Article
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URLURL TypeDescription DOIArticle
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2010 American Chemical Society. Received: February 13, 2010; Revised Manuscript Received: May 3, 2010. Publication Date (Web): June 28, 2010. We acknowledge the National Science Foundation, Grant CHE-0604894, the Defense Advanced Research Projects Agency, Grant BAA-08-48, and the Beckman Institute for support of this work.
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)BAA-08-48
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:28
Record Number:CaltechAUTHORS:20100804-101624923
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Official Citation:Chemical, Electronic, and Electrical Properties of Alkylated Ge(111) Surfaces David Knapp, Bruce S. Brunschwig, Nathan S. Lewis The Journal of Physical Chemistry C 2010 114 (28), 12300-12307
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19270
Deposited By: Tony Diaz
Deposited On:04 Aug 2010 17:23
Last Modified:08 Nov 2021 23:50

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