Ncafm

Another installment in the annals of the bullying of the Shockley surface state, this time the trick isn’t exotic adatoms or massive molecular weight, just a 120° tilt of hexaazatriphenylene (HAT) ligands that converts an achiral lattice into a pair of enantiomeric 2-D metal–organic frameworks. The result: chirality-imposed scattering potentials that lift degeneracies and open ΔE ≈ 80 meV gaps in the Ag(111) two-dimensional electron gas while leaving the global periodicity intact. ...

We had the opportunity to use the new toroidal analyzer at the Australian synchrotron to do ARPES of self-assembled monolayers of MgPc on Ag100. Careful simultaneous fitting of different high-symmetry EDC measurements, in concert with the structural understanding gleaned from ncAFM & LEED characterization, allowed us to tease out a feature with bandwidth 20 meV, which was surprising to us given that we did the ARPES at room temperature. ...

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. 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. ...

nc-AFM atomic registration of single MgPc molecule on Ag100 (surface atoms top and bottom stripes) Marina Castelli studied the phthalocyanine containing magnesium (MgPc) via 5K scanned probe microscopies extensively during her PhD. ‘Routine’ STM characterisation showed that the molecules were interacting with one another on the Ag100 surface. ncAFM showed identical contrast for all molecules, pointing to an electronic origin to the observed changes in appearance. Our key observation was to track the shape of the occupied LUMO for different pairwise distances, an electronic feature that otherwise remained isoenergetic. ...