C. Joachim’s research while affiliated with National Institute for Materials Science and other places

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Publications (174)


Figure 1. (a) Chemical structure of the zwitterionic DMNI-P (color code: C = gray, H = white, N = purple, O = red); (b) STM image of single DMNI-P molecules and dimers after sublimation on the Au(111) surface. Image size: 40 nm x 40 nm, I = 5 pA, V = 0.2 V.
Figure 2. Anchoring and rotation of an isolated DMNI-P. (a) STM image of the molecule anchored at the position of the purple cross; a voltage pulse is applied at the position of the red cross. (b) STM image of the same DMNI-P rotor after the voltage pulse, showing a one-step rotation (Θ = 60°; CCW); the anchoring point (center of rotation) is indicated in purple. (c) By combining the images of the six stations rotating in one direction (CCW), the common anchoring point is identified (indicated by a purple cross). (d) Example of a tip-height time plot Δz(t) measured during a pulse. A voltage pulse was applied under I = 250 pA and V = 0.5 V for 5 sec in constant current mode. STM images (3 nm x 3 nm) were taken at I = 5 pA and V = 0.2 V. (e) Adsorption geometry of the anchored DMNI-P in top and side view respectively, calculated by DFT.
Figure 5. Manipulation of the DMNI-P nanocar. (a) Controlled lateral translation starting from the top to the bottom of the 10 nm x 10 nm area can be observed, where the molecule moves towards the pulsing positions. The red marks indicate the position of the tip during the voltage pulses before the displacement, respectively (V = 0.5 -0.8 V). (b) Trajectory of the molecular movement from (a). STM images (10 nm x 10 nm) were taken under I = 21 pA and V = 0.25 V. (c) Adsorption geometry of the DMNI-P nanocar in top and side view respectively, calculated by DFT.
Figure 6. Yield (motion probability per electron) versus bias voltage for DMNI-P rotor (top) and nanocar (bottom) at pulses of fixed tunnelling current. The continuous lines for the rotor case (top) have been obtained fitting the experimental action spectra by the theory of Ref. 34 obtaining a threshold at 370 meV. In the lower panel, the continuous line is a simulation of the action spectra of the nanocar considering a threshold voltage of 165 meV and an overall yield constant of 3.5 x 10 -10 events/electron. The fitting of the data at different currents was not possible because of the data spread.
A Nanocar and Rotor in One Molecule
  • Preprint
  • File available

May 2023

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234 Reads

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T. Kühne

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Depending on its adsorption conformation on the Au(111) surface, a zwitterionic single-molecule machine works in two different ways under bias voltage pulses. It is a unidirectional rotor while anchored on the surface. It is a fast-drivable molecule-vehicle (nanocar) while physisorbed. By tuning the surface coverage, the conformation of the molecule can be selected to be either rotor or nanocar. The inelastic tunneling excitation producing the movement is investigated in the same experimental conditions for both the unidirectional rotation of the rotor and the directed movement of the nanocar.

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A schematic illustration of the (a) topview (b) sideview for a tert-butylbiphenylbenzene functionalized graphene disk with radius and hexa-tert-butylbiphenylbenzene on Cu(111) surface.
The angle displacement multiplied with number of teeth N 1 = 20 for graphene disk (N 2 = 6 for HB-BPB) within 100 ps with external torque (a) τ ext = 12.8 nN·Å and (b) τ ext = 48 nN·Å. (c) The blue (red) line represents the locking coefficient L 1,2 with respect to external torque ranged from 0 to 160 nN·Å, where region I, II and III represent underdriving, driving and overdriving phases, respectively.
Viscous dissipation for graphene disks with initial angular velocity ω 0 = 0.1 rad/ps on Cu(111) within 200 ps for different gear diameters ranging from 5 to 15 nm.
Size dependence of rotational friction coefficient η = 1/τ due to the phononic contribution (blue) and the electronic contribution according to equation (4) (red) for disk diameters d from 3 to 20 nm. The red region indicates that below 3 nm the motion becomes oscillatory due to confinement by rotational barrier heights.
Profiles of potential energy surfaces V(θ) and rotational kinetic energies (black line) for (a) 2 nm and (b) 3 nm graphene disk on Cu(111) surface.
A nanographene disk rotating a single molecule gear on a Cu(111) surface

February 2022

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84 Reads

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5 Citations

We perform molecular dynamics simulations to study the collective rotation of a graphene nanodisk functionalized on its circumference by tert-butylphenyl chemical groups in interaction with a molecule-gear hexa-tert-butylphenylbenzene supported by a Cu(111) surface. The rotational motion can be categorized underdriving, driving and overdriving regimes calculating the locking coefficient of this machinery as a function of external torque applied. Moreover, the rotational friction with the surface of both the phononic and electronic contributions is investigated. It shows that for small size graphene nanodisks the phononic friction is the main contribution, whereas the electronic one dominates for the larger disks putting constrains on the experimental way of achieving the transfer of rotation from a graphene nanodisk to single molecule-gear.


A Simple Example of a Molecule-Gear Train: PF3 Molecules on a Cu(111) Surface

September 2020

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35 Reads

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1 Citation

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.


Transmission of Rotational Motion Between Molecule-Gears

September 2020

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14 Reads

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.


Rotations of Adsorbed Molecules Induced by Tunneling Electrons

September 2020

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60 Reads

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1 Citation

The advent of molecular machines is placing special attention on the rotation of a single molecule. Arguably, rotations are central for the diverse movements of a machine during its working dynamics. Here, we consider molecules that are constrained by the surface and effect rotations over an axle. They are then planar molecule-rotors. The excitation of a rotation by tunneling electrons, induced for example by the tip of a scanning tunneling microscope (STM), can be quite efficient as shown by a large body of experimental evidence. These rotations are indeed excited by single tunneling electron effect and are limited by the damping of the rotation by the different degrees of freedom of the substrate. When the molecule inertia momentum is small, quantum effects become apparent and rotation becomes very efficient by the large transfer of angular momentum produced by the transferred electrons through the STM junction. For larger molecules the classical limit is rapidly attained. After several considerations on the electron-induced rotation of a single molecule, we show how to evaluate the rotational dynamics during the tunneling of electrons through a molecule-rotor.


FIG. 1. Schematic plot of a train of molecule gears with two hexa (4-tert-butylphenyl)benzene mounted above copper atoms (red) on top of a lead surface (yellow). (a) Top view with rotational angle θ1 and θ2. (b) Side view with rotational axes n1 and n2.
FIG. 7. Analytic modelling of approximate two-gear interaction potential V12(θ1, θ2) with V0 = 450 meV, V1 = 140 meV and k = 50.
Mechanical transmission of rotational motion between molecular-scale gears

October 2019

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893 Reads

Manipulating and coupling molecule gears is the first step towards realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular dynamics simulations. Within a nearly rigid-body approximation we reduce the dynamics of the gears to the rotational motion around the orientation vector. This allows us to study their behavior based on a few collective variables. Specifically, for a single hexa (4-tert-butylphenyl) benzene molecule we show that the rotational-angle dynamics corresponds to the one of a Brownian rotor. For two such coupled gears, we extract the effective interaction potential and find that it is strongly dependent on the center of mass distance. Finally, we study the collective motion of a train of gears. We demonstrate the existence of three different regimes depending on the magnitude of the driving-torque of the first gear: underdriving, driving and overdriving, which correspond, respectively, to no collective rotation, collective rotation and only single gear rotation. This behavior can be understood in terms of a simplified interaction potential.


FIG. 1. Schematic plot of a train of molecule gears with two hexa (4-tert-butylphenyl)benzene mounted above copper atoms (red) on top of a lead surface (yellow). (a) Top view with rotational angle θ1 and θ2. (b) Side view with rotational axes n1 and n2.
FIG. 7. Analytic modelling of approximate two-gear interaction potential V12(θ1, θ2) with V0 = 450 meV, V1 = 140 meV and k = 50.
Mechanical transmission of rotational motion between molecular-scale gears

October 2019

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142 Reads

Manipulating and coupling molecule gears is the first step towards realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular dynamics simulations. Within a nearly rigid-body approximation we reduce the dynamics of the gears to the rotational motion around the orientation vector. This allows us to study their behavior based on a few collective variables. Specifically, for a single hexa (4-tert-butylphenyl) benzene molecule we show that the rotational-angle dynamics corresponds to the one of a Brownian rotor. For two such coupled gears, we extract the effective interaction potential and find that it is strongly dependent on the center of mass distance. Finally, we study the collective motion of a train of gears. We demonstrate the existence of three different regimes depending on the magnitude of the driving-torque of the first gear: underdriving, driving and overdriving, which correspond, respectively, to no collective rotation, collective rotation and only single gear rotation. This behavior can be understood in terms of a simplified interaction potential.


Surface manipulation of a curved polycyclic aromatic hydrocarbon-based nanovehicle molecule equipped with triptycene wheels

October 2018

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59 Reads

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12 Citations

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.


Long Starphene Single Molecule NOR Boolean Logic Gate

April 2018

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46 Reads

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17 Citations

Surface Science

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.


The mathematics of a quantum Hamiltonian computing half adder Boolean logic gate

August 2015

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124 Reads

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12 Citations

The mathematics behind the quantum Hamiltonian computing (QHC) approach of designing Boolean logic gates with a quantum system are given. Using the quantum eigenvalue repulsion effect, the QHC AND, NAND, OR, NOR, XOR, and NXOR Hamiltonian Boolean matrices are constructed. This is applied to the construction of a QHC half adder Hamiltonian matrix requiring only six quantum states to fullfil a half Boolean logical truth table. The QHC design rules open a nano-architectronic way of constructing Boolean logic gates inside a single molecule or atom by atom at the surface of a passivated semi-conductor.


Citations (72)


... For those mechanical interfaces, nanoscale teeth around the nano-disk edge of the gear are not required. The native molecular scale corrugation at the nanodisk edge will normally be enough for the transmission of a rotation between the solid-state nano-disk and a single molecule machinery as recently simulated using molecular dynamics [7]. This is important to consider since nanofabrication of teeth with a width below 5 nm are very difficult to achieve [8,9]. ...

Reference:

Cutting nanodisks in graphene down to 20 nm in diameter
A nanographene disk rotating a single molecule gear on a Cu(111) surface

... [21c] A left-handed helical molecule rotates preferentially in the opposite direction to its equivalent right-handed helical molecule. Tert-butyl groups have also been introduced to increase organic solubility of the target molecule and to allow for easier observation by STM techniques, [24] where they are known to induce good contrast in the imaging. Since this metallo-organic anchoring subunit can be repositioned at will on the surface by pushing with the apex of a STM tip, it is envisioned to build a train of molecular gears with a tunable number of successive cogwheels, having precise control over their chirality. ...

Surface manipulation of a curved polycyclic aromatic hydrocarbon-based nanovehicle molecule equipped with triptycene wheels

... Active matter [1] that is materials containing molecules able to move by themselves, like molecular motors [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] for example, retains a lot of attention due to its links with biology and out of equilibrium statistical mechanics. More specifically, active matter could lead to a better understanding of the glass transition long standing problem [22][23][24][25][26][27][28][29][30][31], due to its out of equilibrium nature and because active matter introduces a controlled cooperative mechanism inside the medium that may interfere [32] with the spontaneous one, an idea that we will follow here. ...

Molecular Machines and Motors
  • Citing Book
  • July 2001

Structure and Bonding

... 40 Here, the BBD molecule must be manipulated with care not to open a conformation change path on its reduced state potential energy surface nor a chemical reaction path breaking some of its chemical bonds leading to the final destruction of the molecule since a molecule is often very unstable under high positive STM bias voltage pulses. 7,41 While exciting the BBD molecule at two different spatial locations of the same resonance maxima, the difference of mechanical response is a nice indication of how the electronic coupling between the tip apex and the electronic states of a molecule can give rise to different mechanical responses. Here and during an STM excitation (or imaging), the effective lateral extension of the tunneling electrons inelastic excitation is much narrower than the BBD molecular orbitals spatial lateral extension. ...

High Voltage STM Imaging of Single Copper Phthalocyanine
  • Citing Chapter
  • August 2013

... This circuit has a quantum cost of 6, a delay of 6△, an auxiliary qubit and no garbage outputs, as it is shown in Fig. 3. This design has been widely used to implement schemes in different experimental systems (Chatterjee and Roy, 2015;Barbosa, 2006;Srivastava et al., 2017;Wu and Cain, 2014;Dridi et al., 2015;Eloie et al., 2018). ...

The mathematics of a quantum Hamiltonian computing half adder Boolean logic gate

... Toujours en configuration de contacts coplanaires, on peut citer les premiers essais de fabrication d'électrodes multiples [19] construites en utilisant la lithographie à faisceau d'électrons sur une surface de SiO2. Ainsi, une vingtaine d'électrodes (de largeur de 18 nm) disposées de manière optimale en cercle ont été réalisées pour une distance inter-jonction de 200 nm. ...

Fabrication of N-electrodes nanojunctions for monomolecular electronic interconnects
  • Citing Article
  • November 2011

International Journal of Nanoscience

... Among possible applications, a significant one is the positioning of metal nanoislands as electrodes for molecular electronics [28,29]. Interconnecting an atomic wire or a molecule to macroscopic probes, while preserving the atomic cleanliness of the surface, is currently not feasible with e-beam nanolithography [30] or the nanostencil technique [31], whereas electrical contacts have been already fabricated using tip-induced motion of ultraflat metal islands [32]. Our results may help to define reliable nanomanipulation protocols in the near future. ...

Ultrahigh vacuum scanning tunneling microscope manipulation of single gold nanoislands on MoS2 for constructing planar nanointerconnects

Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures Processing Measurement and Phenomena

... With the persistent and rapid development of STM manipulation, its application has been greatly extended from arranging the adsorbates in a desired manner to managing singlemolecule chemistry, such as inducing 1) intramolecular confor-mational changes; [15][16][17][18][19][20] 2) intermolecular covalent interactions by coupling two molecules in a controlled step-by-step way; [21] 3) single-molecule isomerization including cis-trans transition of azobenzene, [22][23][24] tautomerization of melamine, [25] isomerization of single chlorobenzene and its analogues, [26,27] and tautomerization of single free-base naphthalocyanine and porphycene molecules; [28,29] and 4) metal-organic complexes including metal-aromatic binding on single-crystal surfaces, [30][31][32] K atoms attaching to C 60 molecules, [33] hybrid magnetic complexes of V atoms and tetracyanoethylene ligands, [34] and metal-ligand interactions on insulating films. [35][36][37] Moreover, the dynamic behaviors of the adsorbates on surfaces could also be controlled by STM manipulations. ...

Manipulation of a single molecule ground state by means of gold atom contacts

Chemical Physics Letters

... The UHV system hosting our UHV transfer printer has already been described in details in a previous publication [2], as well as in the first volume of this Springer book Series [3]. In summary, four independently controlled UHV Scanning Tunneling Microscope (STM) tips under a Scanning Electron Microscope (GEMINI column) constitute the heart of our multi-probe system as shown in Figure 1. ...

Atomic Scale Interconnection Machine
  • Citing Article
  • April 2012