Research

Scanning Probe Microscopy
The SPMQT Lab uses scanning probe microscopy techniques, including STM (Scanning Tunneling Microscopy) and AFM (Atomic Force Microscopy), to visualize the structure of materials at the atomic scale. We specialize in imaging and spectroscopic analysis of advanced materials including 2D materials, semiconductors, oxides, and organic molecules.

STM is a non-optical microscopy technique based on the quantum mechanical tunneling of electrons. STM images are recorded using an atomically sharp metallic tip, shown here forming a mirror image on a gold crystal. Electronics precisely control the motion of the tip and allow us to resolve single atoms.

The centerpiece of our lab is a low temperature combined STM/AFM operating in an ultrahigh vacuum (UHV) system. Combined STM/AFM (qPlus method) allows us to image the surface using tunneling electrons or force (frequency shift) measurements. UHV allows us to prepare and image atomically clean surfaces. Low temperatures (77 K, 5 K) stop thermal diffusion and gives increased energy resolution.

Illustration of a STM tip positioned above a single atom (left). Examples of atomically resolved STM images on a semiconductor (center, 9×9 nm^2) and a 2D material (right, 4×4 nm^2).

Recently, in collaboration with Aleks Rakic (UQ Engineering), we have used scattering Scanning Near-field Optical Microscopy (s-SNOM) with THz light sources to push the boundaries of nanoscale imaging. This collaboration is closely aligned to our push in materials for quantum technology.

Materials for Quantum Technology
Progress in superconducting quantum technology is currently limited by material imperfections such as defects and amorphous oxides which are concentrated at device interfaces. Treating or removing these imperfections significantly improves the performance of superconducting devices. Our research is focused on engineering methods to mitigate the influence of defects. This includes limiting oxide growth and controlling the chemical reactivity of surfaces and interfaces found in quantum devices.

We explore new substrate materials, develop surface engineering strategies, and advance characterization methods to make better devices. This includes collaboration with IQM via an ARC Linkage Project and is in close collaboration with the SQD Lab at UQ led by Arkady Fedorov.

Two resonator chips mounted onto a printed circuit board in preparation for measurement.

SEM images of a Ta film with an etched resonator circuit on a sapphire substrate.

Collaboration
Collaboration is essential to achieve our goals. We work with a wide range of national and international collaborators. Some recent collaborators include:

Arkady Fedorov (UQ SMP) – device fabrication and measurement
Julian Steele (UQ AIBN/SMP) – synchrotron GIWAXS
Javad Shabani (New York University, USA) – MBE material growth
Aleks Rakic (UQ Engineering) – THz SNOM
Carla Verdi (UQ SMP) – DFT calculations
Kirrily Rule, David Cortie (ANSTO) – neutron scattering
Dongchen Qi (QUT) – synchrotron photoemission, NEXAFS
Xiuwen Zhou (QUT) – DFT calculations
Leonhard Grill (Graz, Austria) – molecular manipulation
Craig Williams (UQ SCMB) – synthesis of organic molecules