An international team of researchers has developed a groundbreaking method for detecting and analyzing atomic-level defects in hexagonal boron nitride (hBN), which is a two-dimensional (2D) material often referred to as ‘white graphene’ due to its impressive characteristics. This innovation could speed up the progress of next-generation electronic devices and quantum technologies.
A global research team spearheaded by the NYU Tandon School of Engineering and KAIST (Korea Advanced Institute of Science and Technology) has created a novel approach to identify and investigate atomic-scale defects in hexagonal boron nitride (hBN), a 2D material commonly known as “white graphene” because of its extraordinary attributes.
This breakthrough could hasten the development of cutting-edge electronics and quantum tech.
The researchers found a way to detect single carbon atoms that are substituting for boron atoms within the hBN crystals. This achievement was possible by measuring the electronic “noise” in specially engineered transistors, similar to how one might hear a faint whisper in a peaceful setting.
ACS Nano has chosen this research to feature on the cover of its October 22, 2024 issue.
“In this project, we’ve essentially created a stethoscope for 2D materials,” stated Davood Shahrjerdi, one of the paper’s corresponding authors alongside Yong-Hoon Kim. “By examining the tiny and consistent fluctuations in electrical current, we can ‘detect’ the behavior of individual atomic defects.”
Shahrjerdi serves as an associate professor in NYU Tandon’s Electrical and Computer Engineering Department, is a member of NYU WIRELESS, and directs the NYU Nanofabrication Cleanroom (NanoFab), which launched in 2023. Kim is a Professor of Electrical Engineering at KAIST. Both Shahrjerdi and Kim also hold positions at the NYU-KAIST Global Innovation and Research Institute, leading initiatives within the NYU-KAIST Next-Gen Semiconductor Devices and Chips research group.
The NYU-KAIST collaboration was formally established at NYU in September 2022, inaugurated by the President of South Korea. This noteworthy alliance combines the unique strengths of both institutions to foster progress in research and education, currently engaging over 200 faculty members from each school.
Single-crystal hBN has become a celebrated material in scientific discussions, offering the potential to revolutionize areas ranging from unconventional electronics to quantum technologies.
The atom-thin nature and superior insulating qualities of hBN make it an excellent medium for supporting unique physical phenomena that can’t be achieved with traditional materials. However, atomic defects in hBN can impair its electronic characteristics, sometimes in ways that could be advantageous for quantum technology applications.
The NYU team constructed a transistor by placing a few layers of thin molybdenum disulfide (another 2D semiconductor) between layers of hBN. By cooling this device to cryogenic temperatures and applying specific electrical voltages, they were able to observe distinct fluctuations in the electrical current passing through the transistor.
These fluctuations, referred to as random telegraph signals (RTS), occur when electrons are temporarily captured and released by defects in the hBN. Through meticulous analysis of these signals at various temperatures and voltages, the researchers could identify the energy levels and specific locations of the defects.
“It’s akin to having a microscope that can ‘visualize’ individual atoms, but we are leveraging electricity instead of light,” remarked Zhujun Huang, the lead author of the paper, who was a Ph.D. student in Electrical and Computer Engineering at NYU Tandon at the time of the research.
The KAIST team then employed sophisticated computer simulations to better understand the atomic origins of their experimental findings. This combined effort of experimentation and theoretical analysis demonstrated that the defects consist of carbon atoms positioned in sites where boron atoms should ideally reside in the hBN crystal framework.
“Gaining insight into and controlling the defects within 2D materials may have considerable implications for the future of electronics and quantum technologies,” Shahrjerdi and Kim explained. “For instance, we might be able to develop more perfect quantum material platforms for discovering new physical phenomena or single-photon emitters suitable for secure communications.”
