2DCC User Research Highlight

With the escalating costs of developing and manufacturing integrated circuit (IC) chips, methods to vertically stack devices are being thoroughly explored. While silicon-based 3D ICs have been achieved using innovative packaging solutions, there has been limited exploration of emerging nanomaterials, such as 2D Transition metal dichalcogenides (TMDs), for a monolithic 3D chip.

Ultra-thin 2D semiconductors based on monolayer transition metal dichalcogenides (TMDs) are seen as potential candidates for future generation electronic and optoelectronic devices for energy efficient computing and sensing for applications such as Internet-of-Things and artificial intelligence. Wafer-scale epitaxial TMD monolayers grown by metalorganic chemical vapor deposition (MOCVD) in the 2D Crystal Consortium Materials Innovation Platform facility can be readily transferred from the growth substrate for heterogeneous integration enabling large area device demonstrations.

The canonical topological insulator Bi₂Se₃ has played a central role in the development of ‘topological spintronics,’ a framework that seeks to exploit the inherent spin-momentum correlation in helical Dirac surface states for spin transport devices that could be used for non-volatile magnetic random access memory. Prior experiments have focused on studying efficient interconversion between spin current and charge current in devices that interface a topological insulator with a ferromagnet.

Transition metal dichalcogenides have strong intra-covalent bonding. When stacked in multilayers, weak van der Waals interactions dominate interlayer mechanical coupling and influence their lattice vibrations. In this work, we developed an efficient transfer method for fabricating bilayers of WS₂ with a controlled twist angle. We investigated the evolution of interlayer and moiré phonons, and photoluminescence bandgap depending on the twist angle.

The potential of memristive devices for applications in nonvolatile memory and neuromorphic computing has sparked considerable interest, particularly in exploring memristive effects in two-dimensional (2D) magnetic materials. However, the progress in developing nonvolatile, magnetic field-free memristive devices using 2D magnets has been limited. By fabricating CrI₃-based tunnel junctions, the Tian group at University of Wyoming has recently demonstrated the realization of electrostatic-gating-induced nonvolatile memristive effect. Tian et al.

3D monolithic integration of memory devices with logic transistors is essential for augmenting computational power concurrent with enhanced energy efficiency in big data applications such as artificial intelligence. Ferroelectric field-effect transistors (FE-FETs) are a promising candidate, but requisite scalability and performance in a back-end-of-line process have proven challenging. Here we present BEOL-compatible FE-FETs using 2D MoS₂ channels and AlScN ferroelectric materials, all grown via wafer-scalable processes.

2D semiconductors such as MoS₂ are attractive materials for solar energy conversion because their small physical dimensions minimize the distance that photogenerated carriers must travel to be extracted from the material. Hot carrier extraction from 2D semiconductors depends on ΔG°′, the driving force for interfacial electron transfer.

The MnBi₂Te₄ (MBT) family of intrinsic magnetic topological insulators (MTI) has emerged as an important class of materials to study the interplay between topology, quantum transport, and magnetism. Quantum Hall effect (QHE) of this system has attracted enormous interest but is limited to a few septuple layer thin films (<10-SL). Thick MBT thin film has never been reported to show QHE due to the presence of bulk conductivity.

Surface nanopatterning of substrate by ion beam irradiation provides precise control over the nucleation sites, density, orientation, and growth uniformity of 2D materials, which are crucial for advancing the growth of high-quality atomically thin films and enabling the development of 2D material-based devices with enhanced performance and functionalities. The joint study combining experiment, ReaxFF and DFT calculations [1], focuses on the role of surface patterning of silica in the nucleation of MoS₂.

Alloying different transition metal dichalcogenides not only offers the opportunities to fine-tune their properties, but also opens up some unique properties, which are highly desirable for wide applications including optoelectronics and catalysis. The Jaramillo group at MIT recently demonstrated the synthesis of large area, high-Ti-content, single phase 2H Mo_1−xTi_xS₂ thin films using a two-step method of metal film deposition by magnetron sputtering, followed by sulfurization in H₂S. In collaboration with 2DCC, Jaramillo et al.