40 research outputs found
Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy
Electrochemical
deposition of aromatic organic molecules by reduction
of diazonium reagents enables formation of molecular layers with sufficient
integrity for use in molecular electronic junctions of interest to
microelectronics. Characterization of organic films with thicknesses
in the 1–10 nm range is difficult with Raman spectroscopy,
since most molecular structures of electronic interest have Raman
cross sections which are too small to observe as either thin films
on solid electrodes or within intact molecular junctions. Layer formation
on a 10 nm thick Ag island film on a flat carbon surface (eC/Ag) permitted
acquisition of structural information using surface enhanced Raman
spectroscopy (SERS), in many cases for molecules with weak Raman scattering.
Raman spectra obtained on eC/Ag surfaces were indistinguishable from
those on carbon without Ag present, and the spectra of oligomeric
molecular layers were completely consistent with those of the monomers.
Layer growth was predominantly linear for cases where such growth
was sterically allowed, and linear growth correlated strongly with
the line width and splitting of the CC phenyl ring stretches.
Molecular bilayers made by successive reduction of different diazonium
reagents were also observable and will be valuable for applications
of 1–20 nm organic films in molecular electronics
Mechanism of rectification in tunneling junctions based on molecules with asymmetric potential drops
10.1021/ja108311jJournal of the American Chemical Society1325118386-18401JACS