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Xie, Shihong (2023) Van der Waals Heterostructures based on Two-dimensional Ferroelectric and Ferromagnetic Layers. PhD thesis, University of Nottingham.

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Abstract

Two-dimensional (2D) van der Waals (vdW) crystals provide a platform for studies of novel phenomena and promising applications beyond traditional systems. This PhD thesis focuses on vertical 2D vdW heterostructures, including ferroelectric semiconductor junctions (FSJs), p-n junction diodes, and magnetic tunnel junctions (MTJs). These have potential for non-volatile memories, ultraviolet (UV) photosensing and low-power electronics.

The ferroelectric polarization of the vdW semiconductor α-In2Se3 in graphene/α-In2Se3/graphene FSJs was switched by the bias voltage, thus producing memristive effects in the transport characteristics. These can be modified by light due to screening of the polarization by photocreated carriers. The FSJs demonstrated a high photoresponsivity (up to ~ 10^6 A/W) and a relatively fast modulation (down to ~ 0.2 ms) of the photocurrent.

The graphene/p-GaSe/n-In2Se3/graphene heterostructures were used to investigate novel mechanisms for the detection of UV light. The p-GaSe/n-In2Se3 type-II band alignment and the electric field at the vdW interfaces were found to be beneficial to suppress carrier recombination and enhance the UV-photoresponse.

Finally, the Fe3GaTe2/WSe2/Fe3GaTe2 MTJs exhibited an ideal tunnelling behaviour with a tunnel magnetoresistance (TMR) signal as large as 85 % at room temperature, breaking through the bottleneck of previous vdW MTJs that worked only at low temperatures (T < 300 K).

The findings of this work offer opportunities for further developments, including the optimization of device structures and their studies towards enhanced functionalities beyond the current state of the art.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Patane, Amalia
Keywords:	van der Waals forces, heterostructures, ferroelectronics
Subjects:	Q Science > QC Physics > QC170 Atomic physics. Constitution and properties of matter Q Science > QC Physics > QC501 Electricity and magnetism T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800 Electronics
Faculties/Schools:	UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID:	74386
Depositing User:	Xie, Shihong
Date Deposited:	12 Dec 2023 04:40
Last Modified:	12 Dec 2023 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/74386

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