Metal-organic frameworks (MOF)
Self-assembly at the nanoscale means using the nearly limitless library of organic molecules as building blocks to ideally engineer the electronic phenomena that emerge from the periodic patterns they form.
One such example is our work attributing the Kondo effect we measured in a substrate supported metal-organic framework to a strongly correlated electron state existing in the MOF.
Substrate-molecule effects, on-surface chemistry
There’s plenty of room at the bottomRichard Feynman
The invention of scanning tunneling microscopy and more recently, non-contact atomic force microscopy, has made the observation and manipulation of single atoms and molecules a routine exercise.
This work is at the intersection of chemistry & physics, with diverse messages reflecting the high likelihood for observing unexpected results even with tightly controlled ingredients and experimental circumstances.
“Aromatic Azide Transformation on the Ag(111) Surface Studied by Scanning Probe Microscopy”
“Nitrous oxide as an effective AFM tip functionalization: a comparative study”
Beilstein J. Nanotechnol. (2019)
“Iron-based trinuclear metal-organic nanostructures on a surface with local charge accumulation”
Nature Communications (2018)
“On-surface structural and electronic properties of spontaneously formed Tb2Pc3 single molecule magnets”
RSC Nanoscale (2018)
Topological Dirac Semimetal Na3Bi
We applied the methodology developed for Bi2Se3 to the Dirac semimetal Na3Bi with remarkable success. These are materials where band inversion near the Fermi level creates Dirac-like “cones”, a 3d version of the dispersion that made graphene famous.
We demonstrated large-area thin-film growth, with control in the regime where we could electrostatically control the presence of a topological gap, experimental proof-of-concept to build a topological transistor.
We demonstrated the efficacy of MgF2 as a stabilising capping layer, opening the door to possibilities for Na3Bi beyond just a UHV curiousity.
“Quantum Transport in Air-Stable Na3Bi Thin Films”
ACS Appl. Mater. Interfaces (2020)
“Electric-field-tuned topological phase transition in ultrathin Na3Bi”
“Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film”
Phys. Rev. B (2017)
“Spatial charge inhomogeneity and defect states in topological Dirac semimetal thin films of Na3Bi”
Science Advances (2017)
“Electrostatic modulation of the electronic properties of Dirac semimetal Na3Bi thin films”
Phys. Rev. Materials (2017)
“Molecular Doping the Topological Dirac Semimetal Na3Bi across the Charge Neutrality Point with F4-TCNQ”
ACS Appl. Mater. Interfaces (2016)
“Electronic Properties of High-Quality Epitaxial Topological Dirac Semimetal Thin Films”
Nano Lett. (2016)
Topological Insulator Bi2Se3
My thesis research focussed on the seminal topological insulator Bi2Se3.
With the apparatus we developed we were able to show that significant doping is present as soon as the TI is grown on substrate, before exposure to atmosphere.
We demonstrated that electron acceptor MoO3 can mitigate this effect and stabilise the TI in atmosphere.
“Thickness and growth-condition dependence of in-situ mobility and carrier density of epitaxial thin-film Bi2Se3“
Appl. Phys. Lett. (2014)
“Stability and Surface Reconstruction of Topological Insulator Bi2Se3 on Exposure to Atmosphere”
J. Phys. Chem. C (2014)
“Air-Stable Electron Depletion of Bi2Se3 Using Molybdenum Trioxide into the Topological Regime”
ACS Nano (2014)