Fabrication and characterization of van der Waals heterostructure thermoelectric devices

Abstract

With the discovery of graphene, two-dimensional layered materials (2DLMs) have attracted a huge amount of attention. Each layer in 2DLM contains a covalently-bonded lattice without dangling bonds, which can be weakly bonded to the adjacent layer through van der waals force. So it becomes feasible to isolate, mix, and match atomic layers of different sizes. Under this property's premise, we can create multifarious van der waals heterostructures (vdWHs) without being limited by lattice matching, processing, and compatibility. With the development of vdWHs，it is possible to design a variety of electronic devices and optoelectronic devices with unprecedented characteristics, like tunneling transistors, and photodetectors. Also, with the increasing priority of thermal management, enhancing thermoelectric power (TEP) of vdWHs devices has been widely used in thermoelectric applications. The project was aimed at the fabrication and characterization of van der Waals heterostructures thermoelectric devices. In this report, we introduce the structures and properties of samples in chapter 2 and present the fabrication of the sample (chapter 3), where the vdWHs can now be fabricated layer by layer by using the deterministic placement methods to transfer two-dimensional (2D) materials. In chapter 4, we process the characterization of van der waals heterostructures by Raman Spectroscopy and AFM. In chapter 5, a previous study on TEP in graphene will be focused. In chapter 6, we use thermal power measurement to study the electron-electron correlation in fabricated samples. To quantitatively understand the TEP data, we adopted the semi-classical Mott relationship. We compare the measured TEP, the TEP values calculated with the Mott formula, and the hydrodynamic TEP. In our experiment, it shows that at high temperatures (around 100K ), the measurement value of TEP shows an agreement with Mott's formula.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Sarah Haigh (Supervisor) & Andrey Kretinin (Supervisor)