You are cordially invited to attend the Special Lecture by International Joint-Appointed Scholar. We are pleased to have Professor Vincent Tung from the Department of Chemical System Engineering, The University of Tokyo as speaker. The topic of the lecture is “Materials Science and Engineering at the atomically thin limit ". Further details are as follows:
1. Date: 2024/12/18(Wed)13:00
2. Venue: 1st Meeting Room of Engineering College (Engineering Building 1F)
3. Topic: Materials Science and Engineering at the atomically thin limit
4. Speaker: Professor Vincent Tung
5. Abstract: Two-dimensional (2D)
semiconducting transition metal dichalcogenides (TMDs) representing the
ultimate thickness scaling of channel materials provide a solution to
tantalizingly push the limit of technology nodes in the sub-1-nm range. One key
challenge with 2D semiconducting TMDs channel materials is the large-scale
batch growth on insulating substrates with continuous single crystallinity,
spatial homogeneity, and low defect density. Recent studies have claimed the
epitaxy growth of wafer-scale, single-crystal 2D TMDs on C-plane sapphire
substrate with deliberately engineered off-cut angles. It has been
predominately postulated that exposed step edges break the energy degeneracy of
nucleation and thus drive the seamless stitching of mono-oriented flakes. In
this talk, I will show that a more dominant factor should be considered. The
interaction of 2D TMD grains with the exposed oxygen-aluminum atomic plane establishes an
energy-minimized 2D TMD-sapphire configuration. Reconstructing the surfaces of
C-plane sapphire substrates to only a single type (symmetry) of atomic planes
already guarantees the single-crystal epitaxy of monolayer TMDs without the aid
of step edges. In addition, replacing S-vacancies with isovalent oxygen atoms suppresses
the defect density by an order of magnitude. Electrical results also evidence
the structural uniformity of the monolayers. Our new experimental findings
elucidate the long-standing question that curbs the wafer-scale batch epitaxy
of 2D TMDs single crystals, an essential step toward using 2D materials for
future electronics. Experiments extended to other materials like perovskites
also support the argument that the interaction with sapphire atomic surfaces is
more dominant than the step edge docking.
Contact person: Chiu, Tzu-Ying
Contact number: 3744