Web Release Date: January 31,
Phase-Dependent Desorption from Biphenyl-Substituted Alkanethiol Self-Assembled Monolayers Induced by Ion Irradiation
and
Laboratory of Solid State Physics and Magnetism and INPAC, Institute for Nanoscale Physics and Chemistry, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium, Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, PL 30-059 Kraków, Poland, and EaStChem School of Chemistry, St Andrews University, North Haugh, St Andrews, KY16 9ST, United Kingdom
Received: December 28, 2007
Abstract:
Using laser ionization in combination with time-of-flight mass spectrometry, we have studied ion-induced
desorption of neutral particles from self-assembled monolayers (SAMs) of 
-(4'-methylbiphenyl-4-yl) alkane
thiols (CH3(C6H4)2(CH2)nSH, BPn, n = 2, 4, 6) formed on Au(111) substrates. Because BPn/Au(111) SAMs
with n = even exhibit polymorphism, the effect of purely structural changes on emission yield and fragmentation
pattern could be studied without interference from changes in the chemical composition. In spite of the high
energy of the primary ion beam (15 keV), the mass spectra reveal a striking sensitivity of the desorption
process to rather subtle changes in the structure of the layer. Depending on the SAM structure, substantial
differences in the ratio between the cleavage of the molecule-substrate and the C-S bonds are observed.
For applications of SAMs as resists in ion beam lithography, the results demonstrate that well-defined removal
of molecules requires exact control of the SAM structure.
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