R&D: WPI-MANA Team Demonstrates Laser-Assisted Non Volatile Memory-Based on 2D Van-der-Waals Heterostructures

From International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Japan

A research team at WPI-MANA (World Premier International Research Center Initiative – International Center for Materials Nanoarchitectonics) has demonstrated a laser-assisted non-volatile memory device based on 2-dimensional van-der-Waals heterostructures.

The researchers designed and investigated a few-layer rhenium disulfide (ReS2) field-effect transistor with a local floating gate (FG) of monolayer graphene separated by a thin hexagonal boron nitride (h-BN) tunnel layer, and applied it to non-volatile memory (NVM) devices.

FG-NVM devices based on 2D van-der-Waals heterostructures (atomically thin layers that are attached to each other via very weak van-der-Waals interactions) have been the focus of considerable attention recently, as their tuneable and multibit operation under laser light could make them important components in future digital electronics and multifunctional memory applications.

The team demonstrated multi-level memory operation via 532nm laser pulse and electrostatic gate pulse coupling. The robustness and stability of the laser-assisted tuneable ReS2/h-BN/FG-graphene device show the potential for multibit information storage.

Laser-assisted memory operation provides a new degree of freedom for multifunctional optoelectronic devices with the extra functionality of optically communicated multilevel access. Since laser light can travel through free space without losing power, it allows operation of optoelectronic devices from a distance at low power and with little need for maintenance.

The WPI-MANA researchers used direct bandgap multilayer ReS2 because the material satisfies various requirements as a channel material for electronic devices, as well as being a strong light-absorbing layer, which makes it useful in light-assisted optoelectronic applications.

The device exhibits the functionality of a conventional electronic memory and can store laser pulse-excited signal information for future all-optical logic and quantum information processing.

It also addresses the need for a low-power and optical control of multi-level operation of NVM devices, as well as for an NVM optoelectronic device that can distinguish light wavelengths for color sensing in digital imaging.

This research was carried out by Yutaka Wakayama (group leader, Quantum Device Engineering Group, WPI-MANA, NIMS) and his collaborators.

Article: Laser-Assisted Multilevel Non-Volatile Memory Device Based on 2D van-der-Waals Few-Layer-ReS2/h-BN/Graphene Heterostructures

Advanced Functional Materials has published an article written by Bablu Mukherjee, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan, Amir Zulkefli, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan, and Department of Chemistry and Biochemistry, Faculty of Engineering, Kyushu University, 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan, Kenji Watanabe, Takashi Taniguchi, Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan, Yutaka Wakayama, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan, and Department of Chemistry and Biochemistry, Faculty of Engineering, Kyushu University, 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044, Japan, and Shu Nakaharai, International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1‐1 Namiki, Tsukuba, Ibaraki, 305‐0044 Japan.

Abstract: “Few‐layer rhenium disulfide (ReS₂) field‐effect transistors with a local floating gate (FG) of monolayer graphene separated by a thin hexagonal boron nitride tunnel layer for application to a non‐volatile memory (NVM) device are designed and investigated. FG‐NVM devices based on two‐dimensional van‐der‐Waals heterostructures have been recently studied as important components to realize digital electronics and multifunctional memory applications. Direct bandgap multilayer ReS₂ satisfies various requirements as a channel material for electronic devices as well as being a strong light‐absorbing layer, which makes it possible to realize light‐assisted optoelectronic applications. The NVM operation with a high ON/OFF current ratio, a large memory window, good endurance (>1000 cycles), and stable retention (>10⁴ s) are observed. The successive program and erase states using 10 ms gate pulses of +10 V and −10 V are demonstrated, respectively. Laser pulses along with electrostatic gate pulses provide multibit level memory access via opto‐electrostatic coupling. The devices exhibit the dual functionality of a conventional electronic memory and can store laser‐pulse excited signal information for future all‐optical logic and quantum information processing.“