Sylvain Cruchon-Dupeyrat

In situ studies of thiol self-assembly on gold from solution using atomic force microscopy

The kinetics and mechanism for the solution-phase adsorption of n-alkanethiols onto gold to form self-assembled monolayers (SAMs) have been monitored in situ using atomic force microscopy (AFM). Time-dependent AFM images reveal detailed structural information about the adsorbed layer during its growth. In 2-butanol, CH3(CH2)17SH molecules initially adsorb on gold with the molecular axis of their hydrocarbon chains oriented parallel to the surface. As the surface coverage increases to near saturation, a two-dimensional phase transition occurs and produces islands composed of molecules with their hydrocarbon axis oriented ∼30° from the surface normal. Continued exposure to the thiol solution results in a greater number of these islands and the growth of these nuclei until a SAM is formed with a commensurate (∛×∛)R30° structure. The growth of the lying-down phase follows a first-order Langmuir adsorption isotherm, while the phase transition is best described by a second-order reaction. The kinetics of the se...

Nanofabrication using computer-assisted design and automated vector-scanning probe lithography

This work represents our initial effort towards the fabrication of complex nanopatterns with automated scanning probe lithography (SPL). A multi-mode scanning probe microscope is linked with a computer-controlled vector-scan module to allow precise, automated control of the tip motion. The module is interfaced with computer-assisted design (CAD) and VLSI software, and programming capabilities are developed. We also provide a pathway for integration of our apparatus with external instruments. The capability to rapidly produce complicated nanopatterns is demonstrated using AFM fabrication of thiol self-assembled monolayers.

Contact resonance imaging - A simple approach to improve the resolution of AFM for biological and polymeric materials

Abstract It is frequently observed that high resolution is difficult to achieve when using atomic force microscopy (AFM) to image “soft-and-sticky” surfaces, such as polymers and biomaterials. A new and simple method, contact resonance imaging (CRI), is introduced to address these issues. In CRI, the sample is modulated at a resonance frequency of the tip-sample contact, while the average position of the tip still remains in contact with the surface, i.e. in the repulsive region of the force–distance curve. The improvement in image resolution is demonstrated using various biological and polymeric specimens under ambient laboratory conditions and in liquid media. The possible mechanism of the resolution improvement is discussed in comparison to other techniques, such as tapping-mode imaging.