Sungkyunkwan University announced that Prof. Taesung Kim’s research group in the Department of Mechanical Engineering has achieved a dual breakthrough in next-generation artificial intelligence (AI) semiconductors and spintronic devices by utilizing van der Waals (vdW) materials. The team successfully fabricated a vdW 2D/3D heterojunction neuromorphic memory device through a single plasma process that simultaneously bonded nanocrystals with a van der Waals lattice, while also endowing bulk vanadium selenide (VSe₂), which intrinsically lacks ferromagnetism, with artificial room-temperature ferromagnetic functionality.

With the advent of AI and hyper-connected societies, the demand for neuromorphic memory devices capable of performing memory and computation simultaneously has intensified. However, conventional CMOS-based memory technologies have faced inherent limitations in power consumption and scalability, while metal oxide-based ReRAM has been constrained by grain-boundary effects and filamentary inhomogeneity, which compromise long-term reliability and large-scale integration. To overcome these challenges, the researchers implemented a single-step plasma sulfurization process in which ion penetration and ion-penning effects of Ar and H₂S were precisely controlled, enabling the direct formation of a three-dimensional monolithic integrated architecture without additional deposition or bonding. This approach demonstrated reliable long-term potentiation (LTP), long-term depression (LTD), and analog synaptic weight modulation, with stable operation confirmed for over 1.8×10⁷ switching cycles.

Moreover, the research team also succeeded in realizing two-dimensional room-temperature ferromagnetism, which had long been considered unattainable. Previously, two-dimensional magnetic materials could only be obtained through monolayer exfoliation and exhibited magnetic ordering solely at cryogenic temperatures, precluding practical application. By nanocrystallizing and isolating the lattice of inherently nonmagnetic bulk VSe₂, the team artificially induced ferromagnetic ordering at room temperature. Notably, magnetic force microscopy (MFM) observations revealed that nanocrystalline grain boundaries function as pinning centers for magnetic domains, thereby elucidating a previously unrecognized structure-magnetism coupling mechanism in vdW ferromagnets.

These dual achievements hold profound significance in simultaneously broadening both the universality and applicability of the van der Waals material platform. The 3D monolithic neuromorphic memory offers an alternative architecture that overcomes the physical and process-related limitations of conventional silicon-based integration, while the realization of room-temperature ferromagnetism paves the way for next-generation spintronics and quantum devices. Prof. Taesung Kim emphasized, "Through the development of Single-Step plasma process, we aim to establish a novel vdW material platform that enables the artificial injection of synaptic behavior and room-temperature ferromagnetism, thereby accelerating both next-generation AI semiconductors and spintronic technologies."

This research was jointly conducted with the IBS Center for Quantum Nanoscience, Washington University in St. Louis, the Korea Institute of Machinery and Materials, and the Park Systems R&D Center, and the two research projects were published in "Advanced Science" on May 28 and August 27, respectively.

Authors: Corresponding author: Prof. Taesung Kim; Joint first authors: Jinhyoung Lee (Ph.D. candidate), Gunhyoung Kim (Ph.D. candidate), Hyunho Seok (Postdoctoral Fellow), Hyunbin Choi (Ph.D. candidate), Sujeong Han (M.S. candidate).

Article 1: Monolithically-integrated van der Waals Synaptic Memory via Bulk Nano-crystallization

Article 2: Artificial Room-Temperature Ferromagnetism of Bulk van der Waals VSe2

Journal Link 1: https://doi.org/10.1002/advs.202510961

Journal Link 2: https://doi.org/10.1002/advs.202504746