-
A comprehensive van der Waals heterostructure strategy has been implemented to enable the observation of all Davydov components of the A-mode in few-layer transition-metal dichalcogenides (TMDs) at room temperature. In few-layer 2H-TMDs such as MoS2, MoSe2, and WS2, the A-mode phonon splits into N Davydov components that directly reflect interlayer coupling strength and layer number. Under the resonance conditions near band edge, however, strong photoluminescence (PL) and band filling effects severely obscure these Raman signals, particularly for infrared-active modes, rendering observation of all the Davydov components at ambient temperature infeasible. In this work, few-layer TMD flakes (1–4 layers) were mechanically exfoliated and dry-transferred onto four-layer graphene, followed by high-vacuum annealing to promote interfacial coupling quality. Ultralow-frequency Raman spectroscopy of interlayer shear and breathing modes provided an unambiguous fingerprint for determining the layer numbers of both TMDs and graphene constituents, while differential reflectance spectroscopy precisely located the exciton resonance energies.
Under resonance excitation with the A-exciton, the heterostructures exhibited a marked enhancement of A-mode Raman intensity accompanied by strong PL quenching. Raman peaks associated with all the Davydov components were simultaneously resolved for MoS2, MoSe2, and WS2 at room temperature. The activation of all the Davydov components arises from three synergistic mechanisms: (1) symmetry breaking at the TMDs/graphene interface, which renders forbidden components Raman-allowed; (2) interfacial charge transfer, which suppresses the PL background by depleting photoexcited carriers into graphene; and (3) effcient nonradiative relaxation pathways provided by graphene, which mitigate band filling effect and restore resonant Raman scattering. Furthermore, the highest-frequency Davydov component A(1) exhibited an overall blue shift in the heterostructure relative to the intrinsic TMDs, with the magnitude of the shift decreasing as layer number increased. This behavior is accounted for by a diatomic linear-chain model in which interfacial van der Waals coupling enhances the force constants of intralayer vibrations.
This work thus establishes a general platform for Raman analysis of all the Davydov components of the A mode in 2D TMDs at room temperature and elucidates how interface coupling, layer number, and symmetry breaking jointly govern phonon behavior. The approach offers valuable insights for phonon engineering and interface design in two-dimensional heterostructures and may readily be extended to related systems such as WSe2 and ReS2.-
Keywords:
- Davydov components /
- Heterostructures /
- Transition metal dichalcogenides /
- Interlayer coupling /
- Raman spectroscopy
-
[1] Splendiani A, Sun L, Zhang Y, Li T, Kim J, Chim C Y, Galli G, Wang F 2010 Nano letters 10 1271
[2] Wang G, Chernikov A, Glazov M M, Heinz T F, Marie X, Amand T, Urbaszek B 2018 Reviews of Modern Physics 90 021001
[3] Zhang X, Qiao X F, Shi W, Wu J B, Jiang D S, Tan P H 2015 Chemical Society Reviews 44 2757
[4] Song Q J, Tan Q H, Zhang X, Wu J B, Sheng B W, Wan Y, Wang X Q, Dai L, Tan P H 2016 Physical Review B 93 115409
[5] Leng Y C, Lin M L, Zhou Y, Wu J B, Meng D, Cong X, Li H, Tan P H 2021 Nanoscale 13 9732
[6] Kim K, Lee J U, Nam D, Cheong H 2016 ACS nano 10 8113
[7] Tan Q H, Sun Y J, Liu X L, Zhao Y, Xiong Q, Tan P H, Zhang J 2017 2D Materials 4 031007
[8] Kim S, Kim K, Lee J, Cheong H 2017 2D Materials 4 045002
[9] Tan P H 2019 Raman Spectroscopy of Two-Dimensional Materials (Singapore: Springer).
[10] Zhang Q Y, Cui X W, Dong W L, Jarapanyacheep R, Liu L Q 2025 Chinese Journal of Light Scattering 37 188–195 (in Chinese) [张琼予, 崔旭伟, 董文龙, JARAPANYACHEEP Rapisa, 刘璐琪 2025 光散 射学报 37 188-195]
[11] Jiang J, Li C H, Yao S H, Shen S, Ran N, Zhang J 2024 Chinese Journal of Light Scattering 36 305–319 (in Chinese) [蒋杰, 李聪慧，姚森浩，申珅，冉娜，张洁 2024 光散射学报 36 305–319]
[12] Liu Y, Hu X, Wang T, Liu D 2019 ACS nano 13 14416
[13] Shi H, Yan R, Bertolazzi S, Brivio J, Gao B, Kis A, Jena D, Xing H G, Huang L 2013 ACS Nano 7 1072
[14] Mei R, Zhong Y G, Xie J L, Wu J B, Du W N, Zhang X H, Liu X F, Lin M L, Tan P H Laser & Photonics Reviews e00821
[15] Jiang Y, Chen S, Zheng W, Zheng B, Pan A 2021 Light: Science & Applications 10 72
[16] Li H, Wu J B, Ran F, Lin M L, Liu X L, Zhao Y, Lu X, Xiong Q, Zhang J, Huang W, Zhang H, Tan P H 2017 ACS nano 11 11714
[17] Huang Y, Sutter E, Shi N N, Zheng J, Yang T, Englund D, Gao H J, Sutter P 2015 ACS nano 9 10612
[18] Castellanos-Gomez A, Buscema M, Molenaar R, Singh V, Janssen L, Van Der Zant H S, Steele G A 2014 2D Materials 1 011002
[19] Zhang X, Han W P, Wu J B, Milana S, Lu Y, Li Q Q, Ferrari A C, Tan P H 2013 Physical Review B 87 115413
[20] Tan P H, Han W P, Zhao W J, Wu Z H, Chang K, Wang H, Wang Y F, Bonini N, Marzari N, Pugno N, Savini G, Lombardo A, Ferrari A C 2012 Nature materials 11 294
[21] Wu J B, Zhang X, Ijäs M, Han W P, Qiao X F, Li X L, Jiang D S, Ferrari A C, Tan P H 2014 Nature communications 5 5309
[22] Liang L, Zhang J, Sumpter B G, Tan Q H, Tan P H, Meunier V 2017 ACS nano 11 11777
[23] Pierucci D, Henck H, Avila J, Balan A, Naylor C H, Patriarche G, Dappe Y J, Silly M G, Sirotti F, Johnson A T C, Asensio M C, Ouerghi A 2016 Nano Letters 16 4054
[24] Bieniek M, Szulakowska L, Hawrylak P 2020 Phys. Rev. B 101 125423
[25] Robert C, Han B, Kapuscinski P, Delhomme A, Faugeras C, Amand T, Molas M R, Bartos M, Watanabe K, Taniguchi T, Urbaszek B, Potemski M, Marie X 2020 Nat. Commun. 11 4037
[26] Carvalho B R, Malard L M, Alves J M, Fantini C, Pimenta M A 2015 Phys. Rev. Lett. 114 136403
[27] Niu Y, Gonzalez-Abad S, Frisenda R, Marauhn P, Drüppel M, Gant P, Schmidt R, Taghavi N S, Barcons D, Molina-Mendoza A J, De Vasconcellos S M, Bratschitsch R, Perez De Lara D, Rohlfing M, Castellanos-Gomez A 2018 Nanomaterials 8
[28] Zhou K G, Withers F, Cao Y, Hu S, Yu G, Casiraghi C 2014 ACS nano 8 9914
[29] Tan Q H, Zhang X, Luo X D, Zhang J, Tan P H 2017 Journal of Semiconductors 38 031006
Metrics
- Abstract views: 205
- PDF Downloads: 0
- Cited By: 0
下载:
