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Significantly Increased Raman Enhancement on MoX 2 (X = S, Se) Monolayers upon Phase Transition
Author(s) -
Yin Ying,
Miao Peng,
Zhang Yumin,
Han Jiecai,
Zhang Xinghong,
Gong Yue,
Gu Lin,
Xu Chengyan,
Yao Tai,
Xu Ping,
Wang Yi,
Song Bo,
Jin Song
Publication year - 2017
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201606694
Subject(s) - raman spectroscopy , materials science , rhodamine 6g , monolayer , phase transition , density functional theory , transition metal , fermi level , valence (chemistry) , molecule , nanotechnology , chemical physics , electron , condensed matter physics , optics , computational chemistry , chemistry , biochemistry , physics , organic chemistry , quantum mechanics , catalysis
2D transition metal dichalcogenide (TMD) materials have been recognized as active platforms for surface‐enhanced Raman spectroscopy (SERS). Here, the effect of crystal structure (phase) transition is shown, which leads to altered electronic structures of TMD materials, on the Raman enhancement. Using thermally evaporated copper phthalocyanine, solution soaked rhodamine 6G, and crystal violet as typical probe molecules, it is found that a phase transition from 2H‐ to 1T‐phase can significantly increase the Raman enhancement effect on MoX 2 (X = S, Se) monolayers through a predominantly chemical mechanism. First‐principle density functional theory calculations indicate that the significant enhancement of the Raman signals on metallic 1T‐MoX 2 can be attributed to the facilitated electron transfer from the Fermi energy level of metallic 1T‐MoX 2 to the highest occupied molecular orbital level of the probe molecules, which is more efficient than the process from the top of valence band of semiconducting 2H‐MoX 2 . This study not only reveals the origin of the Raman enhancement and identifies 1T‐MoSe 2 and 1T‐MoS 2 as potential Raman enhancement substrates, but also paves the way for designing new 2D SERS substrates via phase‐transition engineering.