Tag: SPM

scanbot

Jules has put in the hard yards implementing nanonisTCP as a python module, and leveraged that to create scanbot, a tool for automating the tasks of preparing a good imaging & spectroscopy probe, as well as a suite of functions for performing nuanced, drift-corrected measurements over very long timescales.

See the below example of systematically grid scanning 100x100nm images to concatenate a comprehensive view of the surface. Right is the upper left red corner, where self-assembled molecular islands are visible.

Ceddia et al., (2024). Scanbot: An STM Automation Bot. Journal of Open Source Software, 9(99), 6028, https://doi.org/10.21105/joss.06028

2021 AIP summer meeting

The AIP summer meeting was a hybrid event this year 6-9 Dec. ’21 with the border restrictions still in place preventing us from travelling to Brisbane.

Iolanda kindly invited me to talk about Marina’s MgPc hybridization work as well as new results of orbital tomography performed at the Australian Synchrotron (in preparation).

Ben Lowe contributed a talk to the scanning probe microscopy focus session, with an update on how we’re closing in on understanding the mechanism of formation for some unusual metal-organic products identified with ncAFM measurements.

Thanks also to Peggy Schönherr, Peggy Zhang, Peter Jacobson, and Iolanda DiBernardo for contributing talks to the SPM focus session.

Bernard Field talked about how he’s pushing forward how we can rationalise our observations of self-assembled MOF structures, stemming from our recently published experimental results that Agustin talked about in the MOF focus session.

Kagome metal-organic framework

Dhaneesh Kumar has extensively studied the on-surface properties of the DCA molecule for his PhD. After getting a good handle on just the DCA on Ag111, we started sprinkling some Cu atoms into the mix.

We observed the same honeycomb kagome structure that forms on Cu111– as seen in an ncAFM force volume shown in the right image. It has also been synthesized on graphene.

The key difference we observed on Ag111 was the Kondo effect, an STS peak at Fermi we tracked up to 150 K!

The consistent spatial distribution of this feature across the MOF was another key observation.

ncAFM force volume of DCA (structure superimposed upper right) self-assembly on Cu111 surface. dZ denotes lift of sensor away from surface for each frame.

Bernard put in the hard yards with DFT/ +U calculations in conjunction with mean-field Hubbard modelling to rationalise our experimental observations as strong Coulomb interactions between electrons within the kagome MOF.

STS maps
dI/dV STS mapping at biases indicated upper left
DCA Cu Kagome schematic
Schematic of Kondo screened spin moments within the MOF. Blender by Dhaneesh

We’re excited by the possibilities for solid-state architectures to offer further access & control of these intriguing quantum states.

Kumar, D., et. al. (2021). Manifestation of Strongly Correlated Electrons in a 2D Kagome Metal–Organic Framework. Advanced Functional Materials, 2106474. https://doi.org/10.1002/adfm.202106474

ArXiv link
FLEET blog

Concerted Proton Transfer

We stumbled on a very curious observation in the summer of 2018 with DABQDI molecules provided by Olivier Siri‘s team.

ncAFM image of 26 molecule chain. Unfiltered data.
STM chain manipulation
Repeated manipulations with STM tip are capable of dragging a DABQDI chain around the Au111 surface.

While evaluating its experimental suitability for 1d coordination with metals, which has already proven to be fruitful, we noticed the molecules forming chain-like structures even before we introduced metal adatoms.

The low temperature SPM results are sublime: unusual mechanical stability, distinctive intermolecular bonding, and near-Fermi electronic states lighting up at the ends of the chains.

It took an extraordinary cast of theorists hailing from Pavel’s core group, FZU, Charles, Reykjavik, & Madrid Universities to unravel this puzzle and explain these observations as concerted proton tunneling causing a delocalization of electrons.

“Significance of Nuclear Quantum Effects in Hydrogen Bonded Molecular Chains”, ACS Nano, 2021. 10.1021/acsnano.1c02572

ArXiv link