Charge-Spin Conversion and Electronic Transport in Two-Dimensional Materials and van der Waals Heterostructures
Doctoral thesis, 2022

Applications related to artificial intelligence (AI), 5G communication, cloud computing, Internet of Things (IoT) will necessitate wide range of data collection, communication and processing. Current charge-based technology using conventional materials suffers adverse effects with down-scaling the device size and has limited efficiency in meeting the future demands for computation and data storage. The exploration of alternative device technology along with new materials is important to enhance computing performance and energy efficiency. In this thesis, I investigated new materials for future memory and logic technologies.  Recently developed 2D materials such as graphene, semiconductors, and semimetals exhibit remarkable new properties that promise faster and energy efficient non-volatile memory and logic functionalities. For non-volatile memory technologies, increasing efforts are being directed towards exploiting charge-spin conversion phenomena in high spin-orbit coupling (SOC) materials to realize all-electric magnetic memory.

Interestingly, magnetic memory devices have been demonstrated on an industrial scale; however, the moderate efficiency and fundamental limitations of the conventional materials employed limit their use in consumer electronics. This thesis addresses some of these critical challenges and presents charge-spin conversion mechanisms in layered high SOC materials such as topological insulators, semimetals, and two-dimensional (2D) materials heterostructures. At the same time, this thesis contributes in the direction of integrating memory and logic devices by investigating 2D semiconductor devices with sub-20 nm narrow channel width and memristive switching in field-effect transistors using 2D semiconductors with graphene contacts. Such 2D semiconductors have enormous prospects for next-generation high-performance and energy-efficient nanoscale field-effect transistors and integration with memory technologies. These studies of charge and spin transport in 2D materials and heterostructures can open the door for nanometer-scale memory, logic and sensing technologies.



Spin-orbit coupling


Two-dimensional materials

Chemical vapor deposition

van der Waals heterostructure

Proximity effect


Charge-spin conversion

Kollektorn (A423), 4th floor, MC2, Kemiv¨agen 9
Opponent: Professor Luis E. Hueso, CIC nanoGUNE, Spain


Anamul Md Hoque

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

A. M. Hoque, S. Lars, B. Zhao, D. Khokhriakov, and S. P. Dash, “Room temperature nonlocal detection of charge-spin interconversion in a topological insulator”.

A. M. Hoque, B. Zhao, D. Khokhriakov, P. Muduli, and S. P. Dash, “Charge to Spin Conversion in van derWaalsMetal NbSe2”.

A. M. Hoque, V. Ramachandra, A. George, E. Najafidehaghani, Z. Gan, R. Mitra, B. Zhao, D. Khokhriakov, A. Turchanin, S. Lara-Avila, S. Kubatkin, and S. P. Dash, “Spin-valley coupling and spin-relaxation anisotropy in all- CVD Graphene-MoS2 van der Waals heterostructure”.

A. M. Hoque, A. Poliakov, A. V. Agrawal, B. Zhao, R. Mitra, S. Kubatkin, S. Lara-Avila, T. O. Shegai, and S. P. Dash, “Ultra-narrow Semiconductor WS2 Nanoribbon Field-effect Transistors with Atomically Designed Zig-zag Edges”.

In the near future, new applications associated with healthcare, agriculture, automobile and manufacturing industries will greatly depend on artificial intelligence (AI), 5G communication, cloud computing, Internet of Things (IoT). These forthcoming technologies will necessitate a wide range of data collection, communication and computation. These processes will dramatically increase the need for efficient computation and memory technology with gigantic data storage facilities. In modern computer technology, the memory units are separated from the central processing unit (CPU) and these units are connected via a system bus. This separation of the memory and CPU constraints efficiency of the modern computation because sending data back and forth between different components imposes a time delay on the CPU by keeping it idle during data communication.

The integration of memory and logic functionalities like the brain can reduce the energy loss associated with transferring data between memory and processor units, cut the time needed for computing operations and shrink the amount of space required on chips. Conventional materials (silicon) based current computation device is unsuitable to integrate logic and memory functionality locally in compact device design. In this thesis, I investigated the spin and charge transport in the newly developed two-dimensional (2D) materials for future memory and logic technologies. To mention, spin is a basic quantum property of an electron similar to its charge property. 2D materials such as graphene, semiconductors, and semimetals exhibit remarkable new properties that promise to integrate non-volatile memory and logic functionalities with lower energy consumption. One of the key aspects of spin-dependent device applications is to realize robust spin-charge conversion in 2D materials, for example, to read and write data in the memory cell. In this thesis, I show charge-to-spin interconversion phenomena in 2D materials for memory and logic applications. Interestingly a memory unit is accompanied by a field-effect transistor (FET) to access a particular memory cell. Hence, all 2D material-based memory applications will require 2D semiconductor material-based FETs.  In this regard, this thesis presents transistor transport properties in 2D semiconductors (WS2, MoS2)  with nanoribbon channels and with graphene contacts. These studies in 2D materials will be beneficial to develop nanometer-scale memory,  logic and sensing technologies.

2Dimensional van der Waals Spin-Orbit Torque Technology

Swedish Research Council (VR) (2021-05925), 2021-12-01 -- 2024-11-30.

2D material-based technology for industrial applications (2D-TECH)

VINNOVA (2019-00068), 2020-05-01 -- 2024-12-31.

GKN Aerospace Sweden (2D-tech), 2021-01-01 -- 2024-12-31.

Graphene Core Project 3 (Graphene Flagship)

European Commission (EC) (EC/H2020/881603), 2020-04-01 -- 2023-03-31.

Spintronics with Topological Quantum Material and Magnetic Heterostructures

Swedish Research Council (VR) (2021-04821), 2022-01-01 -- 2025-12-31.

Driving Forces

Sustainable development

Innovation and entrepreneurship

Areas of Advance

Nanoscience and Nanotechnology


Basic sciences

Subject Categories

Nano Technology

Condensed Matter Physics


Chalmers Materials Analysis Laboratory

Nanofabrication Laboratory



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5218



Kollektorn (A423), 4th floor, MC2, Kemiv¨agen 9


Opponent: Professor Luis E. Hueso, CIC nanoGUNE, Spain

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