The invention of scanning tunnelling microscopy (STM) – for which the Nobel Prize in Physics was awarded in 1986 – and of scanning tunnelling spectroscopy (STS) enabled probing the local topographic and electronic properties (respectively) of surfaces with atomic resolution. However, real-space mapping of electronic excitations at the nanoscale remains a challenge. Recent progress in STM and STS coupled with optical techniques holds promise for probing local atomic-scale optoelectronic properties of solid interfaces. For example, spectroscopic signature of tunnelling-induced electroluminescence of semiconducting organic molecules, nanostructures and quantum dots allows for real-space mapping of electronic relaxation processes. Also, light-assisted STM and STS (where light is coupled onto the surface-tip junction) can be exploited to address the local electronic signatures of photo-excitation at photoactive interfaces.
The goal of this PhD project is to probe the local atomic-scale electronic properties of (organic and metal-organic) photoactive molecules on surfaces, in their ground and excited states. How does the adsorption configuration affect the photo-excitation characteristics? What is the influence of intermolecular interactions on the optical response? Experimental tools in the Schiffrin group at Monash will include tunnelling-induced electroluminescence, as well as light-assisted low-temperature STM, STS and atomic force microscopy. Metals, thin insulating films and semiconductors will be considered as substrates. The studied systems will be prepared in a controlled ultrahigh vacuum environment and will be investigated in situ. Time-resolved pump-probe experiments will be performed in parallel at collaborating institutes in order to track ultrafast photo-induced electron dynamics at the photoactive molecule-surface systems.
Scholarships are available and cover tuition and health insurance costs (for International candidates) and provide a living stipend of AUD25,849 per year. Exceptional candidates may receive AUD30,000 per year.