GALLERY

COMMUNICATIONS

PUBLICATIONS

RESEARCH

ABOUT ME

Rémy Pawlak

Scientific homepage


Majorana bound state in superconducting Fe chains
R. Pawlak, C. Drechsel, P. D’Astolfo, M. Kisiel, E. Meyer, J. I. Cerda. Probing atomic structure and Majorana wavefunctions in mono-atomic Fe chains on superconducting Pb surface. npj Quantum Information , 2, 16035 (2016). ▸ read
Atomic buckling of silicene measured by AFM
R. Pawlak, C. Drechsel, P. D’Astolfo, M. Kisiel, E. Meyer, J. I. Cerda. Quantitative determination of atomic buckling of silicene by atomic force microscopy. Proceedings of the National Academy of Sciences , 117, 228-237 (2020). ▸ read
Mechanics of a single carbon-carbon bond
R. Pawlak, J.G. Vilhena, P. D'Astolfo, X. Liu, G. Prampolini, T. Meier, T. Glatzel, J.A. Lemkul, R. Haner, S. Decurtins, A. Baratoff, R. Perez, S.-X. Liu, E. Meyer. Sequential Bending And Twisting Around CC Single Bonds by Mechanical Lifting of a Pre-Adsorbed Polymer. Nano Lett. , 20, 652-657 (2020). ▸ read
Every atoms matter
S. Freund, R. Pawlak, L. Moser, A. Hinaut, R. Steiner, N. Marinakis, E. C. Constable, E. Meyer, C.E. Housecroft and Th. Glatzel Transoid-to-Cisoid Conformation Changes of Single Molecules on Surfaces Triggered by Metal Coordination. ACS Nano., 3(10), 12851-12856 (2018). ▸ read
How to win the first international nanocar race
R. Pawlak, T. Meier, N. Renaud, M. Kisiel, A. Hinaut, T. Glatzel, D. Sordes, C. Durand, W.-H. Soe, A. Baratoff, C. Joachim, C. E. Housecroft, E. C. Constable and Ernst Meyer. Design and Characterization of an Electrically Powered Single Molecule. ACS Nano , 11, 9930-9940 (2017). ▸ read
Pulling biomolecules with an atomic force microscope (AFM)
R. Pawlak, J.G. Vilhena, A. Hinaut, T. Meier, Th. Glatzel, A. Baratoff, E. Gnecco, R. Perez and E. Meyer. Conformations and cryo-force spectroscopy of spray-deposited single-strand DNA on gold. Nat. Comm., 10, 685 (2019). ▸ read
Elucidating molecule structure
A.Hinaut, T. Meier, R. Pawlak, S. Freund, R. Jöhr, S. Kawai, T. Glatzel, S. Decurtins, K. Müllen, A. Narita, S.-X. Liu and E. Meyer. Electrospray deposition of structurally complex molecules revealed by atomic force microscopy. Nanoscale, 10(3), 1337-1344 (2018). ▸ read
Single Molecule Tribology : the art of sliding molecules
R. Pawlak, W. Ouyang, A. E. Filippov, L. Kalikhman-Razvozov, S. Kawai, T. Glatzel, E. Gnecco, A. Baratoff , Q.-S. Zheng, O. Hod, M. Urbakh, E. Meyer. ACS Nano, 10, 713-722 (2016). ▸ read
Dr. Rémy Pawlak
Department of Physics
University of Basel
Klingelbergstr. 82
CH-4056 Basel, Switzerland

Office: +41 (0)61 207 3725
Lab: +41 (0)61 207 3797

RESEARCH

Scanning probe microscopy and ultra high vacuum instrumentation

Mountains
Picture of the inside of the microscope head showing the tuning fork holder mounted on the piezoscanner. The sample (not here) is facing down.

These past years as a student or researcher, I worked on ultra-high vacuum (UHV) apparatus to charaterize surfaces at the atomic scale. I developped strong skills in scanning tunneling microsope (STM) and atomic force microscopy (AFM) performed in cryogenic conditions (5K). Atomic force microscopy based on a tuning fork sensor in the qPlus configuration operated in the non-contact mode using a phase lock loop (PLL), together with typical STM characterizations (topographic imaging in the constant-current mode or scanning tunneling spectroscopy (STS)).
Part of my work consists in preparing samples in such atomically cleaned conditions (typically Cu(111), large band-gap semiconductors (TiO2, SrTio3) or superconductors (NbSe2, Pb(110), Pb(111))). Molecule and atoms are evaporated from a quartz crucible installed in the preparation chamber on substrates kept at temperatures from 10 K to 1000 K.


High resolution imaging of molecules and atomic structures

One of my main research task is the acquisition of highly resolved AFM images with functionalized tips enabling unprecedented resolution of molecule structures. Such AFM experiments is possible thank to the small amplitudes of tuning fork sensors operated at low temperature. In such conditions, a single carbon monoxide (CO) molecule can be attached to the the very end of the AFM tip, which drastically enhances the image contrast by probing Pauli repulsive force between tip and sample (Gross, Science 325, 1110 (2009)). Such real-space investigations can adress various on-surface chemical reactions allowing an unambiguous visualization of the atom/molecule organizations, chemical reaction and their biproducts.

Mountains
AFM image with a CO-terminated at 4.5 K tip of a tolyl-terpy molecule on Au(111).

Force and current spectroscopy at the atomic-scale

Mountains
Schematic of force and current grid-spectroscopy used to investigate mechanics, density of states etc.

Beside imaging surfaces, I acquired in the group of Prof. E. Meyer a long-standing experience in exploring the most advanced force and current spectroscopic methods, to give new insights into the mechanical, structural and electronic properties of single molecules at the atomic scale.
Scanning tunneling spectroscopy (STS) acquired using the standard lock-in technique helps determining the local electronic density of states (LDOS) of various samples down to the atomic scale. While inevestigating single molecules, this technique enables the determination of the Highest Occupied Molecular Orbitals (HOMO) and Lowest Unoccupied Molecular Orbitals (LUMO).
Force spectroscopy, on the other hand, is obtained by measuring interaction forces betwen tip and sample in the non-contact mode. This is done by detecting the frequency shift variations, Δf, compared to the resonance frequency of the oscillator. Over the past years, I particularly focused on building three-dimensional force field above single-molecules using atom-tracked positioning. Based on either Δf(z) or Δf(V) spectroscopic curves, this technique is now routinely employed to determine the mechanical properties of molecules as well as their charge redistribution at the sub-molecular scale. See review here.


Single-molecule manipulation

Pulling, sliding, stretching a single molecule, repositionning single atoms to build atomic structures on a surface... Single-molecule manipulation experiments can be achieved with an STM/AFM at low temperature enabling the investigation of the mechanical counter-reactions of a single molecule under a stress or en electrical field, and this well-below the effect of thermal fluctuations. I devote quite some efforts to build up such experiments, understand them and use them to engineer matter down to the atomic scale.

Figure 3: Movie composed of 28 STM images showing the displacement at 4.5 K of a single molecule on Au(111). The translation is propelled by an electrical current injected from the tip.