Public defence in Micro- and nanosciences, M.Sc. Xueyin Bai

The title of the thesis is Novel synthesis technologies for transition metal dichalcogenides and their heterostructures
Crystal structure of transition metal dichalcogenides, a family of two-dimensional materials

M.Sc. Xueyin Bai will defend the thesis "Novel synthesis technologies for transition metal dichalcogenides and their heterostructures" on 2 December 2022 at 12 (EET) in Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering, in lecture hall T2, Konemiehentie 2, Espoo, and onlin in Zoom.

Opponent: Dr. Cecilia Mattevi, Imperial College London, UK
Custos: Prof. Zhipei Sun, Aalto University School of Electrical Engineering, Department of Electronics and Nanoengineering

The public defence will be organized via remote technology. Follow defence:
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Thesis available for public display 10 days prior to the defence at:
Doctoral theses in the School of Electrical Engineering:

Public defence announcement:

Two-dimensional (2D) materials are nanomaterials with a thickness of just a few atoms. The special structure and composition of 2D materials lead to unique physical and chemical properties, enabling a wide range of applications of 2D materials such as transistors, diodes, modulators, catalysis and energy storage.

Currently, chemical vapour deposition is recognised as the most efficient method for synthesising high-quality 2D materials. However, in conventional chemical vapour deposition, 2D materials are typically deposited on expensive single-crystal substrates through the chemical reaction of gaseous precursors. This results in conventional methods having high time and money costs, severely limiting the possibility of large-scale preparation of 2D materials. In this dissertation, a new growth hypothesis that “gaseous precursors can grow spontaneously into substrates” is creatively proposed, and a gas-phase chemical vapour deposition (GCVD) of 2D materials without the involvement of substrates is experimentally achieved. In the experiments, aerosols of 2D nanoflakes are constantly produced by continuously feeding gaseous precursors into the reactor. This GCVD method allows for very facile process scale-up and ultimately large-scale industrial production. The produced materials can be used in the semiconductor industry, new energy industry, etc. and are of great scientific and economic importance.

It can be concluded that the GCVD method can be employed to consistently produce high-quality 2D nanoflakes with great research and application potential.

Contact information of doctoral candidate:

Email [email protected]
Mobile +358465384897


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