Andrew Wee is Professor of Physics and Vice President of Global Relations at the National University of Singapore. In the years leading up to his current roles, he has received numerous titles and awards. He began his bachelor’s degree in physics in 1984 and his master’s degree in physics in 1988, both from the University of Cambridge. He completed his Ph.D. 1990 at Oxford University.

He has received multiple awards over the years including the University of Cambridge’s 1981 Overseas Merit Scholarship and the 2015 Outstanding Scientist Award from the NUS Faculty of Science. Professor Wee was previously visiting scholar at Lawrence Berkeley National Laboratories, Commonwealth Fellow and Rhodes Scholar at the University of Oxford. He has published over 600 articles in internationally refereed journals and was co-editor of ACS Nano since 2011.

Wee’s research interests are currently in adsorption and surface structure studies on single crystals, scanning tunneling microscopy (STM) and synchrotron radiation studies of the molecule-substrate interface, graphene and 2D materials.

In this interview I ask Professor Wee about his current work with Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) and some of the problems he is trying to solve.

Can you please tell me something about your current work in the field of surface and nanosciences, in particular scanning tunneling microscopy (STM) and atomic force microscopy (AFM)?

My current work in surface and nanoscience involves using STM / AFM to study two specific areas: (1) novel 2D materials and heterostructures, and (2) the molecule-substrate interface, including molecular self-assembly and surface reactions.

What problems did your research solve?

Let me illustrate the topic of 2D transition metal dichalcogenides (2DTMDs), which have a variety of exotic properties that can be used in electronic, magnetic, storage, sensor or catalytic applications. Especially if 2D van der Waals magnets exist, they would be ideal atomically thin building blocks for 2D spintronics. Theories have predicted intrinsic magnetism in 2D VX2, such as vanadium diselenide and vanadium ditelluride, which have also been claimed in some experimental reports. However, we show that 2D-VSe2 is not intrinsically ferromagnetic, but shows evidence of spin frustration. A magnetic transition in 2D-VSe2 can be induced at the contamination-free interface between VSe2 and a ferromagnetic layer by interfacial hybridization.

We also found that the reconstructed VSe2 monolayer with Se-deficient line defects shows ferromagnetism at room temperature under X-ray magnetic circular dichroism and magnetic force microscopy, which is consistent with the calculations of density functional theory. This work potentially resolves the controversy over whether single-layer VSe2 is intrinsically ferromagnetic and underscores the importance of controlling surface defects in 2D crystals that affect potential device performance.

What problems are you currently trying to solve?

We are expanding this work on 2D magnets and exploring new ways to make 2D materials magnetic at room temperature, as this is used in practice in flexible and portable 2D spintronic devices. In another project on 2D carbon networks (2) we are investigating how 2D covalent organic frameworks (COFs) can form the basis for advanced membranes for liquid-phase hydrocarbon separations, which are important for efficient and sustainable separation processes in the petrochemical industry.

What uses of STM and AFM may be known to the general public?

STM and AFM are advanced surface science tools that provide images of conductive (STM) and insulating (AFM) surfaces on an atomic scale. In addition, scanning tunneling spectroscopy (STS) provides the local electronic density of states of the surface. As such, STM / AFM can be used to examine any material where surfaces are important, e.g. B. Electronics, catalysis, batteries, corrosion, etc.

Can you briefly tell us about the importance of surface and nanosciences and their recent advances?

In relation to my research interests, surface and nanosciences are important as they help us understand the properties of new and novel low dimensional materials that have potential applications in electronics, photonics, energy materials, etc.

What do you think is the most interesting and / or most important unsolved problem in your area?

In my particular field of 2D materials, the most interesting problem is discovering novel 2D materials with unique properties (electronic, magnetic, optical, etc.) that are useful for next-generation flexible and portable devices.

Are there any unconventional ways to come up with new and novel ideas?

Our unique approach is to use a pure vacuum environment (in-situ) to grow and study these 2D materials and heterojunctions, or to study molecule-substrate interactions. This approach allows us to study the ideal properties of these surfaces / interfaces without exposure to the atmosphere. Such definitive information is important for advancement in this field.

Did you get any good advice that stayed with you? How has it helped you in your career?

Andre Geim (2010 Nobel Prize Winner in Physics) highlighted the importance of changing fields every five years to tackle new and fresh physical problems. So I moved from traditional surface science to graphene and 2D materials, 2D magnets, 2D topological insulators, and molecular self-organization and surface reactions. These fields were alien to me at the time of the switch, but I knew they would be important.

What advice would you give to people pursuing a career in science? If you had to start all over, what advice would you give yourself?

My professional progress may not be typical. The research landscape in Singapore has changed rapidly over the past 30 years. When I returned to Singapore in 1990 and came to the NUS, I had neither scholarships nor Ph.D. Students. In the early years I had to be resourceful. Fortunately, Singapore then launched a number of well-resourced research and innovation plans and budgets that benefited my research program. The advice I would give to myself and others is: work on significant research problems that people care about so that your work has a significant impact.


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