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STM-induced Phase Change and Photon Emission in Thiol-based Self-assembled Monolayers on Gold (111)
Maud Jaouen, Céline Fiorini, Ludovic Douillard and Fabrice Charra

The self-assembly of alkanethiols onto gold surfaces constitutes a key process for building various systems of interest for nanoelectronics and nanophotonics. We report scanning-tunnelling-microscopy-induced local light emission measurements in self-assembled monolayers of (i) dodecanethiol, (ii) 11-amino-1-undecanethiol, and (iii) 11-amino-1- undecanethiol covered with electrostatically bonded poly(5-methoxy-2- (3-sulfopropoxy)-1,4-phenylenevinylene. In (i) and (ii) moderate bias voltages induce a phase change in the monolayer which almost suppress the luminescence yields. A conjugated polymer coverage in (iii) plays a protective role for bias voltages below its optical band-gap, ~2.2 V. Above this value, the PPV layer itself is degraded, which prevents the excitation by STM of the PPV core luminescence.

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