Liu Zheng
Associate Professor
Nanyang Technological University
Singapore
AsianScientist (Jun. 22, 2019) – At the atomic scale, materials can take on properties that are vastly different from when they are in their bulk state. For instance, carbon arranged into a two-dimensional hexagonal lattice—what is known as graphene—acquires incredible strength and electrical conductivity not observed when carbon is in the form of a pencil tip.
Studying atomically thin materials is Associate Professor Liu Zheng at Nanyang Technological University, Singapore. But instead of graphene, he is interested in transition metal chalcogenides (TMCs)—a family of semiconducting materials with potential applications in electronics, such as high-mobility field-effect transistors and broadband mid-infrared detectors.
Over the course of his research career, Liu has found ways to overcome some of the major hurdles in synthesizing single-layer TMCs, discovering novel TMCs with unique properties as well. For expanding the repertoire of 2D materials and their means of production, Liu received the Young Scientist Award at the Singapore President’s Science and Technology Awards 2018. He shares with Asian Scientist Magazine his research journey and his hopes for the future.
- How would you summarize your research in a tweet?
Our work focuses on the growth and applications of 2D materials with only single-atom thickness, via innovative methods and artificial intelligence technology.
- Describe a completed research project that you are most proud of.
I am proudest of my work involving the use of salt to spice up a library of materials beyond graphene. This work has been published in Nature in 2018.
Thinning materials such as graphene down to a layer of single atoms will dramatically change the material’s physical properties and create a wide spectrum of applications for the future of electronics and energy. Apart from graphene, TMCs are a group comprising dozens of atom-thin materials.
TMCs are combinations of metal elements (from group IV to VIII in the periodic table) and chalcogen elements (sulfur, selenium and tellurium, from group IV). Unfortunately, because of the high melting point of many metal precursors, only a handful of these compounds had been produced previously.
Our work has shown that by adding salt such as sodium chloride and potassium iodide, the melting point of the precursor can be dramatically lowered by up to 1,000 degrees Celsius, allowing us to create a greater variety of TMCs. Using a molten salt-assisted chemical vapour deposition method, we have produced 47 atom-thin TMCs (including binary compounds, alloys and heterostructured compounds), of which 35 are completely new to science.
This work is a milestone in nanomaterials. These materials will become game changers in many areas such as electronics, energy and catalysis. We have filed a patent through NTU’s Nanyang Innovation and Enterprise Office for this invention, and initiated collaborations with industrial partners to commercialize these materials.
- What do you hope to accomplish with your research in the next decade?
In the next decade, we will focus on using artificial intelligence to accelerate the development of new materials, as well as commercialize 2D materials for use in electronic devices. We will also be exploring the catalysis and energy applications of 2D materials.
- Who (or what) motivated you to go into your field of study?
My PhD supervisor Professor Sun Lianfeng at the National Center for Nanoscience and Technology (NCNST), China, brought me into the wonderful world of nanomaterials. Sun’s enthusiasm for research impressed me.
After graduation, I got a postdoctoral position at Rice University in the US, where I enjoyed the beauty of 2D materials. There, I experienced fantastic collaborations and fruitful output with my supervisors Professor P. M. Ajayan and Professor Lou Jun.
- What is the biggest adversity that you experienced in your research?
The biggest adversity I am experiencing is the shortage of funds. We are applying for grants from different agencies such as the Ministry of Education and the National Research Foundation to make sure my team can be well-supported moving forward.
- What are the biggest challenges facing the academic research community today, and how can we fix them?
Among the public, there is a rise of anti-intellectualism. According to the Rutgers University Commencement Address by Obama, “we have access to more information than at any time in human history… but, ironically, the flood of information hasn’t made us more discerning of the truth. In some ways, it’s just made us more confident in our ignorance.”
This trend may undermine the basis of modern science and technology. It is not easy to fix it, but as Carl Sagan once said, “we can judge our progress by the courage of our questions and the depth of our answers, our willingness to embrace what is true rather than what feels good.”
Within the academic research community itself, we are missing reliable and commonly accepted criteria to evaluate researchers and research work. A synergic effort is required to consider the difference in research subjects, scientific and social impact of the research.
- If you had not become a scientist, what would you have done instead?
I probably would have been a writer, a front-end web engineer or a freelancer.
- Outside of work, what do you do to relax?
Most of the time, I read books on my Kindle or Kobo. I also play RPG games [role-playing video games] occasionally.
- If you had the power and resources to eradicate any world problem using your research, which one would you solve?
I would like to solve global warming. Global warming has already shown observable effects on the environment such as the accelerated rise of global temperature, loss of biological biodiversity, increased ocean acidity and high frequency of extreme weather.
However, the impact of global warming is still underestimated because of two reasons: its effects manifest over a relatively long-term, and it is a collective and complicated phenomenon consequential of human activities.
- What advice would you give to aspiring researchers in Asia?
Look far and work deep. Be bold to cross the boundaries of research areas.
This article is from a monthly series called Asia’s Rising Scientists. Click here to read other articles in the series.
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Copyright: Asian Scientist Magazine; Photos: Liu Zheng.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
