Abstract
Molecular electronics is considered a promising approach for future nanoelectronic devices. In order that molecular junctions can be used as electrical switches or even memory devices, they need to be actuated between two distinct conductance states in a controlled and reproducible manner by external stimuli. Here we present a tripodal platform with a cantilever arm and a nitrile group at its end that is lifted from the surface. The formation of a coordinative bond between the nitrile nitrogen and the gold tip of a scanning tunnelling microscope can be controlled by both electrical and mechanical means, and leads to a hysteretic switching of the conductance of the junction by more than two orders of magnitude. This toggle switch can be actuated with high reproducibility so that the forces involved in the mechanical deformation of the molecular cantilever can be determined precisely with scanning tunnelling microscopy.
Highlights
Molecular electronics is considered a promising approach for future nanoelectronic devices
We present low-temperature scanning tunnelling microscope (STM) measurements and density functional theory (DFT) calculations on tripodal spirobifluorene derivatives, which are designed to firmly bind to a gold surface via three sulfur atoms at the feet[27]
We show that the high reproducibility of the process of contact formation of the nitrile group to a gold electrode allows us to build a fully controllable electromechanical molecular toggle switch and to deduce the forces that are needed to stretch the molecular junction
Summary
Molecular electronics is considered a promising approach for future nanoelectronic devices. Break-junction experiments largely contributed to the progress of understanding electron transport in single-molecule junctions[3,4,5] In these measurements, the molecular adsorption and the arrangement of the atoms in the metallic electrodes are a priori unknown and often many different nearly degenerate junction geometries exist. With a view to future applications, it is necessary to control the properties of single-molecule junctions by external means[16] such as mechanical forces[17], electric fields[18,19,20], currents[21,22] or light[23,24] In this respect, it is helpful to design the molecule such that it binds to the substrate electrode in a welldefined geometry and to lift the functional group of the molecule from the metallic substrate. We show that the high reproducibility of the process of contact formation of the nitrile group to a gold electrode allows us to build a fully controllable electromechanical molecular toggle switch and to deduce the forces that are needed to stretch the molecular junction
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