Two-electron dissociation of single molecules by atomic manipulation at room temperature

Abstract

Using the tip of a scanning tunnelling microscope (STM) to mechanically manipulate individual atoms and molecules on a surface is now a well established procedure. Similarly, selective vibrational excitation of adsorbed molecules with an STM tip to induce motion or dissociation has been widely demonstrated. Such experiments are usually performed on weakly bound atoms that need to be stabilized by operating at cryogenic temperatures. Analogous experiments at room temperature are more difficult, because they require relatively strongly bound species that are not perturbed by random thermal fluctuations. But manipulation can still be achieved through electronic excitation of the atom or molecule by the electron current tunnelling between STM tip and surface at relatively high bias voltages, typically 1-5 V. Here we use this approach to selectively dissociate chlorine atoms from individual oriented chlorobenzene molecules adsorbed on a Si(111)-7 x 7 surface. We map out the final destination of the chlorine daughter atoms, finding that their radial and angular distributions depend on the tunnelling current and hence excitation rate. In our system, one tunnelling electron has nominally sufficient energy to induce dissociation, yet the process requires two electrons. We explain these observations by a two-electron mechanism that couples vibrational excitation and dissociative electron attachment steps.

Communication: Site-selective bond excision of adenine upon electron transfer

“…3 However these methods are not readily scalable for many potential technological or medical applications. Therefore, the achievement of electron-induced site-and bond-specific dissociation (on surfaces using STM tips 4 and in the gas phase using low-energy electron beams [5][6][7][8][9] ) in the mid 2000s was highly significant. The only previous control over dissociation pathways in atom-molecule collisions was demonstrated for potassium impact on gas-phase thymine and uracil.…”

Mapping the site-specific potential energy landscape for chemisorbed and physisorbed aromatic molecules on the Si(1 1 1)-7 × 7 surface by time-lapse STM

“…Towards this aim there has been a focus on using the tip of the scanning tunnelling microscope (STM) to induce atomic and molecular manipulation to build designer nano-structures with many striking results [5][6][7]. Underpinning these works are the ground-state properties of the target atoms and molecules.…”

Molecular nano-arches on silicon

“…In particular, the mechanism of adsorption of chlorobenzene on the Si(1 1 1)-7 · 7 surface has been extensively studied recently [1][2][3][4][5][6][7][8][9][10]. At low-coverages chlorobenzene chemisorbs on the Si(1 1 1)-7 · 7 surface in the form of single molecules by opening a double bond of the aromatic ring and forming two carbon-silicon r-bonds with a silicon adatom and a restatom [2].…”