Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies

The van der Waals (VdW) heterostructure has attracted significant attention owing to its potential as a platform for unique physics and electronic device applications. Recently, a one-dimensional VdW (1D-VdW) heterostructure was achieved by the direct growth of two-dimensional materials, such as hexagonal boron nitride (hBN) and transition-metal dichalcogenide on carbon nanotubes (CNTs). Despite its attractive configuration in terms of the possible high integration density of VdW heterojunctions, scaling up from individual nanostructures to bulk structures for actual applications remains unachieved. One possible strategy to fabricate the bulk-scale 1D-VdW heterostructure is the direct growth of heterogeneous materials on CNT assemblies. In the past decade, significant developments have been made in the dry spinning method to scale up CNTs to bulk structures while maintaining the clean surface of CNTs without any mixture. By combining the dry spinning technique and direct heterogeneous growth of hBN, we successfully achieved the bulk-scale integration of the hBN/CNT heterostructures with high controllability of crystallinity of the hBN layer. Through electric transport investigations, we found memristive behavior in hBN/CNT heterostructure assemblies. Through systematic experiments and structural observations, we propose a possible model for the mechanism of memristive behavior that originates from the one-dimensional growth of the hBN layer on the CNTs and functionalized amorphous carbon (a-C). The imperfect crystallinity of hBN with turbostratic layers and grain boundaries prepared by well-controlled growth may function as an appropriate barrier for the formation of a conductive filament channel, enhancing the memristive behavior. The hBN/CNT heterostructure assemblies with memristive functions and high mechanical degrees of freedom are extremely valuable for future neuromorphic computing and conventional nonvolatile memory devices.

Automated summary

The study focuses on the fabrication of one-dimensional van der Waals heterogeneous structures on carbon nanotubes by directly growing two-dimensional materials such as hexagonal boron nitride. The research successfully achieved the bulk-scale integration of the hBN/CNT heterostructures and discovered memristive behavior in the assemblies. The imperfect crystallinity of hBN on CNTs may enhance the memristive behavior, making the heterostructure assemblies valuable for neuromorphic computing and nonvolatile memory devices.