Layer-by-Layer Oxidation Induced Electronic Properties in Transition- Metal Dichalcogenides

 

Soumya Ranjan Das1*, Katsunori Wakabayashi2,3, Mahito Yamamoto3, Kazuhito Tsukagoshi3, and Sudipta Dutta1

 

1Department of Physics, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati 517507, Andhra Pradesh, India

 

²Department of Nanotechnology for Sustainable Energy, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda 669-1337, Japan

 

³WPI Centre for Materials Nanoarchitechtonics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan

 

*soumya.das[at]students.iisertirupati.ac.in

 

Recent progress in transition-metal dichalcogenides has opened up new possibilities for atomically thin nanomaterial based electronic device applications. Here we investigate atomic-scale self-assembled heterojunction modulated by layer-by-layer controlled oxidation in monolayer and few-layer dichalcogenide systems and their electronic properties within a first-principles framework1. Pristine dichalcogenide systems exhibit semiconducting behavior. We observe reduction of the band gap for partial oxidation of the top layer. However, complete oxidation of the top layer makes the system metallic, owing to the charge transfer from the pristine to the oxidized layer, making the pristine layer hole-doped. As a result, the system is expected to show p-type charge conduction. Our results are in complete agreement with recent experimental findings2, 3. When the bottom layer gets partially oxidized with fully oxidized top layers, the system shows unprecedented semimetallic behavior. The appearance of valence band maximum and conduction band minimum at different k-points can introduce valley polarization. Electron conduction in this system is possible only by introducing inter-k scattering in terms of electron-electron or electron-phonon coupling. This exotic behavior can be considered as a new topological phase of charge carriers originating at the interface. Therefore, our study shows controlled oxidation induced varying electronic properties in dichalcogenide based heterojunctions that can be exploited for advanced electronic, optoelectronic and valleytronic applications.

References
[1] Soumya Ranjan Das et al., J. Phys. Chem. C 122, 17001 (2018).

[2] Mahito Yamamoto et al., Nano Lett. 15, 2067 (2015).

[3] Mahito Yamamoto et al., Nano Lett. 16, 2720 (2016).