Excited Excitonic States in 1L, 2L, 3L, and Bulk WSe2 Observed by Resonant Raman Spectroscopy

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• 作者：Elena del Corro ; Humberto Terrones ; Ana Elias ; Cristiano Fantini ; Simin Feng ; Minh An Nguyen ; Thomas E. Mallouk ; Mauricio Terrones ; Marcos A. Pimenta
• 刊名：ACS Nano
• 出版年：2014
• 出版时间：September 23, 2014
• 年：2014
• 卷：8
• 期：9
• 页码：9629-9635
• 全文大小：525K
• ISSN：1936-086X

文摘

Resonant Raman spectroscopy (RRS) is a very useful tool to study physical properties of materials since it provides information about excitons and their coupling with phonons. We present in this work a RRS study of samples of WSe₂ with one, two, and three layers (1L, 2L, and 3L), as well as bulk 2H-WSe₂, using up to 20 different laser lines covering the visible range. The first- and second-order Raman features exhibit different resonant behavior, in agreement with the double (and triple) resonance mechanism(s). From the laser energy dependence of the Raman intensities (Raman excitation profile, or REP), we obtained the energies of the excited excitonic states and their dependence with the number of atomic layers. Our results show that Raman enhancement is much stronger for the excited A鈥?and B鈥?states, and this result is ascribed to the different exciton鈥損honon coupling with fundamental and excited excitonic states.

Keywords:

transition-metal dichalcogenides; WSe₂; resonant Raman spectroscopy; electronic properties; excitonic states