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Spectroscopy of binary-ternary TMD heterostructures (master thesis)

Project description

Two-dimensional (2D) materials reveal fascinating mechanical, electrical, and optical properties with prospects in a wide range of electronic, optoelectronic, and photonic applications. Based on electrical conductivity, their classifications range from insulators via semiconductors and semi-metals to metals. A special class are transition metal dichalcogenides (TMDs), which are semiconducting. Group IVB TMDs show direct optical band gaps in their monolayer form, covering the visible and near infra-red regions. Moreover, they exhibit strong excitonic effects due to reduced dielectric screening and enhanced Coulomb interaction. In addition, alloying TMDs (via the transition metal or chalcogen) offers a way to tune the optical bandgap, carrier type and/or induce phase change transitions. Furthermore, both TMDs and their alloys offer novel spin and valley attributes due to the strong spin-orbit interaction and the lack of inversion symmetry in the TMD monolayer crystal structure, respectively. More importantly, pursuits in the design and development of functional low dimensional material structures to enhance functionality gave birth to the engineering of artificial van der Waals heterostructures. 

WSe2/Mo0.5W0.5Se2 heterostructure: Schematic diagrams of type-II band alignment (a) and material stacking arrangement (b) of a prepared sample shown in the optical micrograph (c) with corresponding photoluminescence data acquire at room temperature (d).   

Aim

The aim of the project is two-fold: (a) prepare binary-ternary heterostructures targeting type II band alignment which has prospects for optoelectronic devices, (b) explore intra- and inter-layer excitonic features, their nature, and dynamics coupled with spin-valley phenomena.

Skills acquired

During the project, you will acquire skills in exfoliating TMDs and their alloys, and prepare heterostructures using the viscoelastic stamping method, undertake optical characterization experiments using mainly photoluminescence and Raman spectroscopies. In addition, you will learn data analysis, to prepare analysis reports, and likely you will contribute to writing a manuscript for a scientific publication.

Contact: Dr Hilary Masenda