Synthesis of two-dimensional van der Waals’ ferromagnetic materials

Abstract

Two-dimensional materials that exhibit interesting properties have attracted extensive attention over the past few years due to its potential applications in highly compact spintronics. However, it was until recently that 2D magnet has been discovered. Various synthesis methods have been developed to produce 2D magnets, mainly categories into top-down exfoliation such as mechanical exfoliation and bottom-up growth methods such as chemical vapor deposition (CVD). In recent years, most of the research on 2D magnets mainly focused on top-down exfoliation of van der Waals’ crystal. However, top-down exfoliation lacks the scalability and consistency for large scale applications which could be potentially overcome by CVD. Hence in this project, 2D ferromagnetic FeS2 and Fe3GeTe2 crystals were synthesized via CVD. The synthesized 2D magnets were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), superconducting quantum interference device (SQUID), and scanning transmission electron microscopy (STEM). The properties of the 2D material are largely influenced by the morphology and phase of the 2D crystal which can be controlled by growth parameters such as growth temperature, source-substrate distance, and type of substrate. Therefore, the effects of these growth parameters on the size and morphology of FeS2 and Fe3GeTe2 were also studied in this project.