Two-dimensional (2D) materials of atomic thickness are nowadays considered with attention in view of future applications and more fundamental studies. Transition metal dichalcogenides (TMDs) in the rhombohedral (3R, i.e., 0° twist) crystal phase have been the focus of significant research interest in optical applications due to their broken inversion symmetry and induced ferroelectric state [1-3]. During my thesis, we report an experimental and theoretical study of tungsten diselenide (WSe2) homo-bilayers obtained in stable 3R configuration by chemical vapor synthesis (CVD) [4] and molecular-beam epitaxy (MBE) [5]. These bilayers' electronic and structural properties are investigated using micro- Raman spectroscopy, angle-resolved photoemission nano-spectroscopy measurements (nano-ARPES), and density functional theory (DFT) calculations. Our results demonstrate that WSe2 bilayers with 3R crystal phase show a significant spin-orbit splitting estimated to 550 ± 20 meV. Comparing the dispersion of specific bands with the theoretical calculations, we were able to distinguish the stacking type of the MBE-grown structure. Our work opens new perspectives for the development of optoelectronic and spintronic devices based on 3R TMD homo-bilayers.

[1] K. M. McCreary et al. Nanoscale, 2022,14, 147-156 (2022)
[2] Zhijie Li et al. Phys. Rev. B 106, 045411 (2022)
[3] Chao Chang et al. Nat Commun 15, 4130 (2024)
[4] Aymen Mahmoudi et al. Phys. Rev. B 108, 045417 (2023)
[5] Aymen Mahmoudi et al. ACS Nano 2023 17 (21), 21307-21316 (2023)