AN INVESTIGATION INTO NIOBIUM DISELENIDE: ATOMIC DEFECTS AND 2D PROPERTIES

Abstract

Niobium Diselenide (NbSe2) is quickly becoming a highly interesting material due to its unusual properties [1-5]. Such properties include Superconductivity (SC) at low temperatures of 10 K [3,6-9]; Charge Density Wave (CDW) formation from ≤ 33 K in the bulk regime to ≤ 145 K in the monolayer [3,7,10,11] and it also demonstrates excellent photoconductivity [12].Through High-Resolution Transmission Electron Microscopy (HRTEM) analysis of the 2-Dimensional (2D) material NbSe2, different types of defects were explored and compared to previously explored defects in other 2D crystals [1,14]. Defects are important to investigate because of the effect they have on the materials’ properties [13-22]. The introduction of defects can vastly alter the properties of a pristine crystal structure and can be used to functionalise materials for a range of different purposes [16,17,19,23]. This body of work demonstrates the first defects observed in monolayer NbSe2 by HRTEM and describes temporal defect population dynamics and their relative stability in addition to how NbSe2 might be functionalised. My work contributed to the paper ‘Atomic defects and doping of monolayer NbSe2 (Nguyen, L. et al. ACS Nano 11 (3), pp 2894–2904 (2017))’, in which I am a listed author. This thesis will outline the objectives of the paper, dealing with its content while highlighting my contributions. This project took advantage of samples produced in a unique glove-box mechanical exfoliation system within the NGI (produced by Ekaterina Khestanova and Roman Gorbachev), Transmission Electron Microscope (TEM) imaging was performed using an image corrected TEM at the University of Warwick by Reza Jalilikashtiban in collaboration with Jeremy Sloan. Geometric Phase Analysis (GPA) was done by Jonathan Peters at the University of Warwick. DFT (Density Functional Theory) work was done by Hannu-Pekka Komsa and Arkady V. Krasheninnikov.

Date of Award	31 Dec 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Antonios Oikonomou (Supervisor) & Sarah Haigh (Supervisor)