Professor Taesung Kim’s research team in the Department of Mechanical Engineering at Sungkyunkwan University (President Ji-Bum Yoo) has collaborated with Professor Seok-Joon Kwon’s research team to develop next-generation encryption technology based on Physically Unclonable Function (PUF) which was achieved by identifying the randomly generated lattice symmetry-breaking characteristics within van der Waals topological insulators.

PUF utilize the random physical variations occurring during the semiconductor manufacturing process to generate unique, physically unclonable identification keys. Considered highly secure, hardware-based encryption technologies, PUF are suitable for small Internet of Things (IoT) devices. However, conventional PUF have limitations as they require more complex hardware structures to increase the number of security key combinations. To overcome this, the research team focused on the unique characteristics of van der Waals topological insulators. A topological insulator is a material that behaves as an insulator internally but conducts electricity on its surface, making it highly useful in quantum computing research. In van der Waals topological insulators, inversion symmetry in the crystalline structure is broken, leading to a topological state with metallic properties on the surface. The research team employed a low-temperature plasma process to sulfurize the top layer of the material, inducing asymmetric lattice structures and randomly distributed ferroelectric domains. These domains exhibited spontaneous polarization, enabling the development of a self-powered, high-security PUF device.

The research demonstrated that the PUF device achieved an optimal level of randomness, with a probability of approximately 0.5012 for generating “1” in a binary sequence. This randomness level is crucial for ensuring encryption security. Additionally, the research team verified that the size of the ferroelectric domains and the PUF device could be controlled by adjusting the plasma process parameters. Piezoelectric force microscopy (PFM) was utilized to validate the device’s reliability and reproducibility. The low-temperature plasma process also allows for large-area synthesis with shorter production times, making the technology highly scalable and suitable for commercial mass production.

Professor Kim explained, "This next-generation quantum encryption technology, leveraging lattice symmetry-

breaking characteristics in van der Waals topological insulators, enables self-powered, high-security encryption with a low-temperature plasma process. It will be a key foundational technology for future artificial intelligence and quantum security platforms.“

The research was supported by the National Research Foundation of Korea (NRF) and the Institute for Basic Science (IBS). The findings were published in Advanced Materials, one of the world’s leading journals in materials science, on February 18th.

※ Title: Stochastically Broken Inversion Symmetry of Van der Waals Topological Insulator for Nanoscale Physically Unclonable Functions

※ Journal: Advanced Materials (IF: 29.6, Top 1% JCR)

※ Link: https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.202419927

Schematic of stochastically broken inversion symmetry of van der Waals topological insulator