The physics of ultra-thin materials
Dr Kai Leng, Assistant Professor at the Hong Kong Polytechnic University, has been making headlines in the scientific community. She’s just been named one of the “Innovators Under 35” (TR35) in the Asia Pacific region in 2023 by the Massachusetts Institute of Technology Review. She has also received an award from the Excellent Young Scientist Fund (Hong Kong and Macau) from the National Natural Science Foundation of China in 2023.
On top of this, earlier this year, she was also awarded the Croucher Innovation Award to support her research work.
Croucher News caught up with Dr Leng to find out why her work was attracting so much attention.
Dr Leng is currently working on new physics in the emerging field of molecularly thin 2D hybrid perovskites. She has created a set of nanotechnology tools and procedures for studying these materials at the molecular level and for realising their promise for multifunctional smart device applications. Her group is currently working on the large-scale development of molecularly thin 2D hybrid perovskite films and investigating novel spintronic device applications.
Leng told Croucher News that this was an exciting field to be working in. “There’s huge interest in these kinds of materials,” she told us. “One of their key attributes is ‘tunability,’ which refers to the ability to adjust or control specific properties of a material. We can manipulate its structure, for example, to adjust its sensitivity to light.”
Leng’s success in fabricating the first hybrid perovskite monolayer photodetector is a good example of this. She was able to detect a new physical property of molecularly thin (monolayer) level, a “reversible order (de-relaxation) to disorder (relaxation) transition” phenomenon. This led to greatly increased internal quantum efficiency when compared to the use of traditional bulk crystal materials, which would mean far less energy would be required for this kind of photodetector.
Photodectectors are used in countless ways, from scientific research to fibre optics, and from digital cameras to medical imaging equipment. Greater energy efficiency would be a major development, especially for battery-powered applications.
It’s this tunability of molecularly thin 2D hybrid perovskite films which makes them so intriguing and which has huge potential for applications ranging from solar cells to optical sensors. The material is of great interest, too, to the semiconductor industry as well as for its use in “spintronics”. Leng explained that whereas in traditional electronics, the charge of the electron is used to store and manipulate information, “in spintronics, the spin of electrons is used. This has the potential for creating new ways of processing and storing information in electronic devices, making them faster, smaller, and more efficient.” Potential applications of spintronics include advanced data storage devices, spin-based transistors, and quantum computing.
It was becoming clear why there was so much excitement around these kinds of 2D materials, just one molecule thick. But how hard was it to create them?
“It’s not easy, of course! But I have been lucky enough to work in state-of-the-art labs, which have sophisticated machines required to make this material. I’ve also spent years developing the skills I needed, especially at the National University in Singapore.”
“And my background in chemistry helps me with the synthesis of new materials. For this kind of innovative research work, it’s really useful to be able to draw upon different disciplines like this.”
So what comes next?
“Next, I’m going to investigate how spin transport can be controlled by electricity and light in these materials, and to grow large-area films to take the first step towards bridging the gap for industrial applications. I’m hoping I can publish several papers on this in the next year or so and hopefully apply for a patent. After that, I don’t think we’ll need to wait very long for commercial applications to be developed.
We asked Dr Leng how she became a scientist and why she chose this field of work.
“Growing up, I always knew that I wanted to go beyond the knowledge given to me and make a difference. This field is exciting because it has given me the chance to do just that, since there is so much to learn and discover, and the applications of these discoveries are so many and varied. The possibilities are endless.”
“I have been lucky to have been inspired and encouraged by my peers and senior colleagues,” she continued. “I’ve enjoyed different working environments, such as the extremely supportive one I’ve found here at PolyU and the wonderful labs I had access to at NUS in Singapore. And the support of Croucher Foundation with its Innovation Award this year has been hugely important to me. It really helps me to make a difference with my work.”
Dr Kai Leng was awarded a Croucher Innovation Award in 2023. Her profile is here.