QMKPFM
Quantum approach to modelling high resolution Kelvin Probe Force Microscopy
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 85060. One of the main output of the project is this KPFM_sim code, that allows for (automated) calculation of the non-contact Atomic Force Microscopy (nc-AFM) and (still non-contact) Kelvin Probe Force Microcopy (KPFM) on a Density Functional Theory (DFT) level.
The project was (most) active in between 1/2020 -- 3/2022 .
Kelvin probe force microscopy (KPFM) is one of the latest scanning probe microscopy techniques that uses a very sharp tip to measure the electrostatic forces and charge transfer on the surface of a sample. However, the theory that underlies such measurements and all physical interactions between the tip and the sample are not well understood, especially in very close scans. Funded by the Marie Skłodowska-Curie programme, the QMKPFM project will use density functional theory calculations to reveal the unknown physics of close KPFM scans. The work will enable researchers to derive additional information about the composition of the local structures on the surface of a sample.
Kelvin Probe Force Microscopy (KPFM) is one of the newest scanning probe microscopy techniques, that enables us to obtain information about electrostatics and charge transfer on a surface, measured via very sharp tip moving above a sample. However, the theory behind the KPFM measurements and all physical interactions between the tip and sample are not fully understood, especially for very close scans. We plan to use density functional theory calculations to reveal the unknown physics of close KPFM scans. We will prepare multiscale simulation package for the KPFM, which will work on quantum theory level as well as simplified fast mechanistic model level and which will cover a wide range of experimental conditions. This work will enable us to get additional information about the physics going on the scanned sample from the KPFM measurements and to employ KPFM as an additional source of information for structural identification. Finally, it can lead to general theory for chemical resolution in scanning probe microscopy.
The video abstract together with other (possibly interesting) videos and video-posters are freely available on the QMKPFM youtube video channel.
The results of this project were disseminated and communicated on these conferences and workshops:
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08/2019 Nc-AFM 22, Regensburg, Germany – conference on high resolution non-contact atomic force microscopy concerning topics of surface science, physics and on-surface chemistry – POSTER
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06/2020 FHI-aims meeting, on-line (Germany & USA) – meeting of developers and users of the FHI-aims code for DFT and quantum chemical computations connecting people from material science, computational physics and chemistry – video POSTER
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10/2020 Nanoscience Days, on-line (Finland) – conference on nanoscience concerning topics from biology, medicine and physics – POSTER
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03/2021 DPG spring meeting, on-line (Germany) – conference on material science – POSTER
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03/2021 Physics Days, on-line (Finland) – conference on general physics in Finland – TALK
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04/2021 Seminar of Department of Surface and Plasma Science, Charles University, on-line (Czech Republic) – TALK
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12/2021 MRS autumn meeting, (USA) – conference on Material Science – TALK
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01/2022 Seminar of Institute of Theoretical chemistry, Ulm University, on-line (Germany) – TALK
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03/2022 Physics Days, on-line (Finland) – conference on general physics in Finland – TALK
The main outcome of this project is the KPFM_sim software, that allows to connect the atomic and electronic structure computing DFT code CP2K with a database with planing tasks and stored results. The calculations are mainly focusing on computations of geometries and total energies once a model of tip is approaching (z) a model of sample above different x and y points of the sample. Later it can approximate the electronic field around the tip and sample, once the voltage are applied between those and then it can calculate the total energy of the x,y,z point depending on the applied voltage V.
In addition to this, we came up with simple mechanical models, that can explain or approximate the source of KPFM signal, when the tip-apex is relaxing. These models are part of the Probe Particle (AFM) Model and they are openly available under the MIT License. These models and how to run them is explained in the Probe Particle (AFM) Model wiki.
K. Nakamura, Q. Q. Li, O. Krejčí, A. S. Foster, K. Sun, S. Kawai, and S. Ito, On-Surface Synthesis of a π-Extended Diaza[8]circulene, J. Am. Chem. Soc. 142, p. 11363–11369 (2020) DOI: https://doi.org/10.1021/jacs.0c02534; or green open ccess version.
L. Yan, O. J. Silveira, B. Alldritt, O. Krejčí, A. S. Foster and P. Liljeroth, Synthesis and Local Probe Gating of a Monolayer Metal‐Organic Framework, Adv. Funct. Mater. 2021, 2100519 (2021) DOI: https://doi.org/10.1002/adfm.202100519 (Open Access)
J. Järvi, B. Alldritt, O. Krejčí, M. Todorovic, P. Liljeroth and P. Rinke, Integrating Bayesian Inference with Scanning Probe Experiments for Robust Identification of Surface Adsorbate Configurations, Adv. Funct. Mater. 2021, 2010853 (2021) DOI: https://doi.org/10.1002/adfm.202010853 (Open Access)
Q. Fan, L. Yan, M.W. Tripp, O. Krejci, S. Dimosthenous, S. R. Kachel, M. Chen, A. S. Foster, U. Koert, P. Liljeroth, Peter; M. J. Gottfried, Biphenylene network: A nonbenzenoid carbon allotrope, Science 372, 852-856 (2021) DOI: https://doi.org/10.1126/science.abg4509; or green open-access version.
N. Oinonen, C. Xu, B. Alldritt, F. F. Canova, F. Urtev, S. Cai, O. Krejčí, J. Kannala, P. Liljeroth, A. S. Foster, Electrostatic discovery atomic force microscopy, ACS Nano 16, 89–97 (2022) DOI: https://doi.org/10.1021/acsnano.1c06840 (Open Access)
The project (funded by EU) would not be possible without access to High Performance Computing facilities through:
Triton Aalto Cluster:
CSC supercomputers through projects no. 2003835 and ay6310 .
ondrej(dot)krejci(at)aalto(dot)fi -- Ondrej Krejci, Aalto University; Last updates 4/2022