Observation of surface enhanced IR absorption coefficient in alkanethiol based self-assembled monolayers on GaAs(001)

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DOIResolve DOI: http://doi.org/10.1063/1.3122052
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TypeArticle
Journal titleJournal of Applied Physics
Volume105
Issue9
Pages094310-1094310-7; # of pages: 7
AbstractAlkanethiol self-assembled monolayers (SAMs) of various methylene group chain lengths [HS–(CH₂)n–CH₃] (n=9,11,13,15,17) were fabricated on the GaAs(001) surface followed by characterization using Fourier transform infrared spectroscopy. Modal analysis of the CH₂ stretching mode region (2800–3000 cm⁻¹) showed that linear scaling of the n-dependent factors accurately reproduced the spectral data, supporting a chain-length consistent physical model upon which a measurement of the absorption coefficient was based. Evaluated from the linearity of the absorbance data, a peak coefficient of 3.5 x 10⁴ cm⁻¹ was obtained and a domain for ordered self-assembly was assigned for values n>9. Compared with measurements of the absorption coefficient made in the liquid phase, the SAM phase coefficient was determined to be about six times greater. This enhancement effect is discussed in terms of contributions relating to the locally ordered environment and is largely attributed to the chemical properties of the interface. We believe this to be the first demonstration of IR spectral enhancement of a molecular species chemisorbed on the semiconductor surface.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Chemical Process and Environmental Technology
Peer reviewedYes
NRC number52014
NPARC number15109547
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Record identifier7cf59c10-94fc-4a6b-8f05-8a2bb09d2d60
Record created2010-05-05
Record modified2017-03-23
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