Development of large scale CVD grown two dimensional materials for field-effect transistors, thermally-driven neuromorphic memory, and spintronics applications

TL;DR

This research advances the synthesis and application of large-scale 2D TMDC materials grown via CVD for use in transistors, neuromorphic memory, and spintronics, addressing key fabrication challenges and demonstrating high-performance devices.

Contribution

It introduces optimized CVD methods, novel transfer techniques, and demonstrates multifunctional devices, advancing 2D TMDC integration in electronics and spintronics.

Findings

High mobility, hysteresis-free MoS2 transistors

Room temperature mem-transistors with multi-level memory

6-bit neuromorphic memory using WS2

Abstract

Semiconductor research has shifted towards exploring two-dimensional (2D) materials as candidates for next-generation electronic devices due to the limitations of existing silicon technology. Transition Metal Dichalcogenides (TMDCs) stand out for their exceptional optoelectronic properties and potential for advanced device integration. This thesis focuses on the synthesis of 2D TMDCs using Chemical Vapor Deposition (CVD) for their potential applications in transistors, memory, and neuromorphic computing. By optimizing the NaCl-assisted CVD method and examining their optical properties through Raman and photoluminescence spectroscopy, challenges such as premature growth, defects, and non-uniformity in MoS2 samples are addressed. The thesis highlights device fabrication techniques and electrical performance of salt-assisted CVD-grown MoS2 field-effect transistors, which exhibit hysteresis-free behavior and high field-effect mobility. A novel etching-free transfer technique is introduced, improving transistor performance and enabling applications in flexible optoelectronics. The thesis also explores monolayer MoS2 mem-transistors, demonstrating multifunctional room temperature transistor and high-temperature multi-level memory behaviour. These devices leverage interfacial physics and ion dynamics to achieve non-volatile memory with multi-level storage capabilities. Additionally, high density memory devices using monolayer WS2 are developed, which demonstrate 6-bit memory operation with neuromorphic biomimetic plasticity. The study also includes 2D TMDCs and their hetero-bilayers as potential 2D dilute magnetic semiconductors via doping, strain engineering using density functional theory and micromagnetic simulations, revealing potential applications in spintronics. This thesis makes significant contributions to advancing 2D materials for next-generation electronics and spintronic devices.