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Anomalous Behavior of 2D Janus Excitonic Layers under Extreme Pressures
Author(s) -
Li Han,
Qin Ying,
Ko Byeongkwan,
Trivedi Dipesh B.,
Hajra Debarati,
Sayyad Mohammed Yasir,
Liu Lei,
Shim SangHeon,
Zhuang Houlong,
Tongay Sefaattin
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202002401
Subject(s) - janus , monolayer , materials science , blueshift , photoluminescence , chemical physics , chemical vapor deposition , van der waals force , semiconductor , condensed matter physics , phase transition , heterojunction , nanotechnology , transition metal , optoelectronics , chemistry , molecule , physics , biochemistry , organic chemistry , catalysis
Newly discovered 2D Janus transition metal dichalcogenides layers have gained much attention from a theory perspective owing to their unique atomic structure and exotic materials properties, but little to no experimental data are available on these materials. Here, experimental and theoretical studies establish the vibrational and optical behavior of 2D Janus S–W–Se and S–Mo–Se monolayers under high pressures for the first time. Chemical vapor deposition (CVD)‐grown classical transition metal dichalcogenides (TMD) monolayers are first transferred onto van der Waals (vdW) mica substrates and converted to 2D Janus sheets by surface plasma technique, and then integrated into a 500 µm size diamond anvil cell for high‐pressure studies. The results show that 2D Janus layers do not undergo phase transition up to 15 GPa, and in this pressure regime, their vibrational modes exhibit a nonmonotonic response to the applied pressures ( dω / dP ). Interestingly, these 2D Janus monolayers exhibit unique blueshift in photoluminescence (PL) upon compression, which is in contrast to many other traditional semiconductor materials. Overall theoretical simulations offer in‐depth insights and reveal that the overall optical response is a result of competition between the ab ‐plane (blueshift) and c ‐axis (redshift) compression. The overall findings shed the very first light on how 2D Janus monolayers respond under extreme pressures and expand the fundamental understanding of these materials.