Properso Klein

Hubert Klein





Self Assembled monolayers

Substrates for the observation of isolated molecules





AFM imaging (top left) and STM of a self assembled monolayer of decanethiols on Au(111).
Low current imaging (2pA). The high resolution picture exhibit the molecular structure of the film :a sqrt(3)*sqrt(3) surstructure of the underlying gold film.



STM pictures of a mixed monolayer decanethiols/octanethiols
Molecular contrast between the two molecules. This contrast depends on the imaging parameters and is due to the small conductive character of the alcane chains.
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STM imaging of diarylethene derivatives (photochromic molecules) inserted in a monolayer of octanethiols. The grafting in the monolayer allows the imaging of isolated molecules on substrates at room temperature


Contrast variation of an isolated photochrome during STM imaging.
The contrast evolves rapidly under the STM tip, and is not due to tip changes


Profiles of contrast variations of an isolated photochrome.These profiles show a bistability which depend on the tunneling bias
Contrast changes occurs between two states associated to the two isomers of the molecule under study. The relative lifetime of the molecule in these states depend on the tunnel bias. The conversion mechanism is an energy transfer between the tunneling electrons and the molecule.

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