1. Physik-Department
E20, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
2. ARC
Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
3. Monash
Centre for Atomically Thin Materials, Monash University, Clayton, Victoria 3800, Australia
4. School
of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
5. School
of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371