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. https://resolver.caltech.edu/CaltechAUTHORS:20100804-101624923
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Abstract
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.
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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. | |||||||||
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Issue or Number: | 28 | |||||||||
DOI: | 10.1021/jp101375x | |||||||||
Record Number: | CaltechAUTHORS:20100804-101624923 | |||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20100804-101624923 | |||||||||
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 | |||||||||
Collection: | CaltechAUTHORS | |||||||||
Deposited By: | Tony Diaz | |||||||||
Deposited On: | 04 Aug 2010 17:23 | |||||||||
Last Modified: | 08 Nov 2021 23:50 |
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