Inspired by the ability of scanning tunneling microscopy (STM) to manipulate single molecules on the atomic scale, the idea to built nanomachines out of molecules has been emerged. The direct tip-molecule interaction or voltage pulses are used to control and power the movement of the molecules. However, until now only single molecules have been moved in a controlled way by applying voltage pulses. Moreover, the movement of larger molecules is crucially dependent on the underlying surface.
Here, we show the controlled manipulation of self-assembled molecular structures with voltage pulses on a metal surface. Depending on the polarity of the voltage, multiple types of movement, such as rotation, translation or reorganization, can be obtained.
The prochiral 4-Acetyl-Biphenyl molecule self-assembles on the Au(111) surface in chiral groups of four molecules. The groups are arranged in a windmill structure with two mirror symmetric forms. To achieve a manipulation, we apply a voltage pulse on top of one of the molecules. Subsequently, all molecules of the group move at once. The molecular groups show different manipulation behavior depending on the polarity of the voltage. In the negative voltage regime, the groups are repulsed by the tip and are moved laterally. At positive bias the supramolecular structures are attracted towards the tip. The groups can be either rotated or moved laterally in this regime. For high positive voltages the molecules reorganize. We analyzed the movement of the supramolecular structures statistically. We find that the electron yield is linear with the current. This indicates a single electron process. The threshold voltage on the negative side is about -1V, whereas on the positive side we need to apply about +2V to achieve a movement. The voltage of +2V coincides with the measured LUMO indicating a strong relation of the movements with the electronic structure of the supramolecular group.
Applying the voltage consecutively, we can move the structures over large distances and to any desired position on the surface. The movement is not restricted by the reconstruction of the surface. Our experiments show a unique possibility to manipulate nanostructures in a controlled manner on metal surfaces in view of assembly of novel nanoscale devices.
Inspired by the ability of scanning tunneling microscopy (STM) to manipulate single molecules on the atomic scale, the idea to built nanomachines out of molecules has been emerged. The direct tip-molecule interaction or voltage pulses are used to control and power the movement of the molecules. However, until now only single molecules have been moved in a controlled way by applying voltage pulses. Moreover, the movement of larger molecules is crucially dependent on the underlying surface.
Here, we show the controlled manipulation of self-assembled molecular structures with voltage pulses on a metal surface. Depending on the polarity of the voltage, multiple types of movement, such as rotation, translation or reorganization, can be obtained.
The prochiral 4-Acetyl-Biphenyl molecule self-assembles on the Au(111) surface in chiral groups of four molecules. The groups are arranged in a windmill structure with two mirror symmetric forms. To achieve a manipulation, we apply a voltage pulse on top of one of the molecules. Subsequently, all molecules of the group move at once. The molecular groups show different manipulation behavior depending on the polarity of the voltage. In the negative voltage regime, the groups are repulsed by the tip and are moved laterally. At positive bias the supramolecular structures are attracted towards the tip. The groups can be either rotated or moved laterally in this regime. For high positive voltages the molecules reorganize. We analyzed the movement of the supramolecular structures statistically. We find that the electron yield is linear with the current. This indicates a single electron process. The threshold voltage on the negative side is about -1V, whereas on the positive side we need to apply about +2V to achieve a movement. The voltage of +2V coincides with the measured LUMO indicating a strong relation of the movements with the electronic structure of the supramolecular group.
Applying the voltage consecutively, we can move the structures over large distances and to any desired position on the surface. The movement is not restricted by the reconstruction of the surface. Our experiments show a unique possibility to manipulate nanostructures in a controlled manner on metal surfaces in view of assembly of novel nanoscale devices.
