W.-H. Soe’s research while affiliated with French National Centre for Scientific Research and other places

A molecule-gear rotating without a lateral jittering effect is constructed using a single copper adatom as a physical axle on a lead superconducting surface. The molecule-gear has a diameter of 1.2 nm with 6 tert-butyl-teeth. It is mounted on this Cu axle using the atom/molecule manipulation capability of a low temperature scanning tunneling microscope (LT-STM). Transmission of rotational motions between 2 molecule-gears, whose axles have to be exactly 1.9 nm separated, is functioning when this train of molecule-gears is completed with a molecule-handle. To manipulate the molecule-handle laterally, the first molecule-gear of the train directly entangled with the molecule-handle is step by step rotated around its Cu adatom axle. It drives the second molecule-gear mechanically engaged with the first gear to rotate like along a train of macroscopic solid-state gears. Such rotation transmission is one of the most basic function for the future construction of a complex molecular machinery.

A train of molecule gears consisting of PF3 molecules was studied using semi-empirical ASED+ method to explore the mechanism of rotational transmission along this train. It was observed that a unidirectional rotational transmission occurs between only the first two PF3 molecules for a PF3 molecule train up to six molecule-gears, the four PF3 molecules at the end of the train being used to rigidify the rotation axle of the first two PF3. This demonstrates that in a train of molecule-gears, the rotation of each molecule is resulting from a collective action of many degrees of freedom per molecule. This collective motion is rather fragile against many others possible minimum energy trajectories which can develop on the multidimensional ground state potential energy surface of a molecule-gear train to respond to the increase of the potential energy required to rotate the first molecule-gear of the train.

The Kondo effect results from the interactions of the conduction electrons in a metal bulk with localized magnetic impurities. While adsorbed atop a metallic surface, the on-surface nanoscale version of this effect is observed when a single magnetic atom or a single magnetic molecule (SMM) is interacting with the conduction electrons. SMM are commonly organo-metallic complex incorporating transition metal atoms in different oxidation states. We demonstrate how a single non-magnetic neutral tetrabenzo[a,c,j,h]phenazine molecule can be on-surface coordinated with exactly two aluminum metal atoms (Al(III) oxidation state on the Au(111) surface) by low-temperature scanning tunneling microscope (LT-STM) single atom manipulation. It results a Kondo measurable localized molecular magnetic moment. This opens a new way to design SMM complex without the need of heavy transition metal atom and complex ligand to stabilize the molecular coordination sphere.

Two molecule-gears, 1.2 nm in diameter with 6 teeth, are mounted each on a single copper ad-atom separated exactly by 1.9 nm on a lead surface using a low temperature scanning tunneling microscope (LT-STM). A functioning train of 2 molecule-gears is constructed completed with a molecule-handle. Not mounted on a Cu ad-atom axle, this ancillary molecule-gear is mechanically engaged with the first molecule-gear of the train to stabilize its step by step rotation. Centered on its Cu ad-atom axle, the rotation of the first gear of the train step by step rotates the second similar to a train of macroscopic gears. From the handle to the first and to this second molecule-gear, the exact positioning of the two Cu ad-atom axles on the lead surface ensures that the molecular teeth to teeth mechanics is fully reversible.

With a central curved chassis, a four wheels molecule-vehicle was deposited on an Au(111) surface and imaged at low temperature using a scanning tunneling microscope. The curved conformation of the chassis and the consequent moderate interactions of the four wheels with the surface were observed. The dI/dV constant current maps of the tunneling electronic resonances close to the Au(111) Fermi level were recorded to identify the potential energy entry port on the molecular skeleton to trigger and control a driving of the molecule. A lateral pushing mode of molecular manipulation and the consequent recording of the manipulation signals confirm how the wheels can step by step rotate while passing over the Au(111) surface native herringbone reconstructions. Switching a phenyl holding a wheel to the chassis was not observed for triggering a lateral molecular motion inelastically and without any mechanic push by the tip apex. This points out the necessity to encode the sequence of the required wheels action on the profile of potential energy surface of the excited states to be able to drive a molecule-vehicle.

Using a low temperature scanning tunneling microscope (LT-UHV-STM), local electronic tunneling spectroscopy and differential conductance mapping are performed to investigate how by extending one phenyl more each branch of the conjugated board of a trinaphthylene starphene molecule, the corresponding longer trianthracene starphene new molecule is functioning like a NOR Boolean logic gate according to a Quantum Hamiltonian Computing (QHC) design. Here the STM tip is used to manipulate single Au atoms one at a time for contacting a trianthracene molecule. Each Au atom is acting like a classical digital input on the molecule encoding for a logical “0'' when the atom is not interacting with the trianthracene input branch and for a logical “1'' when interacting. The inputs are converted in quantum information inside the trianthracene molecule and the logical output status available on the output branch. QHC is demonstrated to be robust since quantum information transfer can be used on the long range along the trianthracene for the NOR logic gate to function properly as compared to the shorter trinaphthylene molecule.

a b s t r a c t Single gold adatoms were manipulated on a Au(1 1 1) surface with the tip of a scanning tunnelling microscope to contact selected peripheral p bonds of a single Coronene molecule. Tunnelling electron spectroscopy and differential conductance mapping of the Au–Coronene complexes show how Coron-ene's electronic ground state is shifted down in energy as the function of the number of interacting Au atoms, demonstrating that a Coronene molecule can function like a single molecule counter. The number of interacting atoms can be counted by simply following the linear energy downshift of Coronene's ground state. Ó 2013 Elsevier B.V. All rights reserved.

In this chapter experiments done to investigate the scanning tunneling microscope (STM) imaging at near field emission voltages of single Copper Phthalocyanine (CuPc) molecules deposited on Au(111) are presented. An imaging bias voltage range is explored exceeding the standard tunneling imaging conditions going from the threshold of the tunneling junction barrier up to −10.0 V. At this voltage regime current transmitted through the tip-molecule–substrate junction is made not only of tunneling electrons but also of electrons overcoming the tunneling barrier and behaving like free electrons. Our interpretation of the process, enabling the visualization of the electronic cloud of single organic molecules under these conditions, is presented.

Using a low temperature, ultrahigh vacuum scanning tunneling microscope (STM), dI/dV differential conductance maps were recorded at the tunneling resonance energies for a single Cu phthalocyanine molecule adsorbed on an Au(111) surface. We demonstrated that, contrary to the common assumption, such maps are not representative of the molecular orbital spatial expansion, but rather result from their complex superposition captured by the STM tip apex with a superposition weight which generally does not correspond to the native weight used in the standard Slater determinant basis set. Changes in the molecule conformation on the Au(111) surface further obscure the identification between dI/dV conductance maps and the native molecular orbital electronic probability distribution in space.