NEMRG

○ Main Research Tool

Low Temperature Scanning Tunneling Microscope (LT-STM2)

○ Research Interests

(1) Influence of quantum well states on apparent tunneling barrier height in ultra thin Pb films.

Surface work function, defined as the minimum energy required to remove an electron in a solid into vacuum, is a fundamental quantity that dictates many physical and chemical processes on solid surface with tremendous technological implications. I’m interested in STM investigations of quantum size effects on the work function of ultra-thin films – a topic theoretically investigated many decades ago but only became experimentally accessible recently due to the advancement in quantum control of thin film growth.

(2) Influence of quantum well states on the formation of surface Au/Pb alloy in Pb/Si(111) quantum thin films.

Pb/Si(111) system has been widely studied due to its strong confinement of electronic states which gives rise to Quantum Well States (QWS). It has been known Au can easily form alloy with Pb and there are very interesting issues on Au/Pb/Si(111) system:

- Are there any preferred Pb thicknesses for Au to form 2D islands?

- If Au can form surface alloy on top of Pb islands, how QWS influences the formation of Au-Pb surface alloy?

- How all these things evolve with annealing process?

Eventually, these questions are related to what is the role of QWS on the competition between thermodynamic and kinetic processes? Our motivation starts from these questions

(3) 2D superconductivity

Studies of two-dimensional (2D) superconductivities have been generally limited to the regime where the superconducting order parameter behaves as a 2D wave function but the underline electrons are still three dimensional. Recent advancements in materials synthesis have enabled the growth of epitaxial superconductor thin films with unprecedented control in crystallinity, atomic smoothness, and film thickness, thus opening up new opportunities in investigations of 2D superconductivity.