title: Two-Dimensional Heterostructure as a Platform for Surface-Enhanced Raman Scattering.
abstract: Raman enhancement on a flat nonmetallic surface has attracted increasing attention, ever since the discovery of graphene enhanced Raman scattering. Recently, diverse two-dimensional layered materials have been applied as a flat surface for the Raman enhancement, attributed to different mechanisms. Looking beyond these isolated materials, atomic layers can be reassembled to design a heterostructure stacked layer by layer with an arbitrary chosen sequence, which allows the flow of charge carriers between neighboring layers and offers novel functionalities. Here, we demonstrate the heterostructure as a novel Raman enhancement platform. The WSe2(W) monolayer and graphene (G) were stacked together to form a heterostructure with an area of 10 mm × 10 mm. Heterostructures with different stacked structuress are used as platforms for the enhanced Raman scattering, including G/W, W/G, G/W/G/W, and W/G/G/W. On the surface of the heterostructure, the intensity of the Raman scattering is much stronger compared with isolated layers, using the copper phthalocyanine (CuPc) molecule as a probe. It is found that the Raman enhancement effect on heterostructures depends on stacked methods. Phonon modes of CuPc have the strongest enhancement on G/W. W/G and W/G/G/W have a stronger enhancement than that on the isolated WSe2monolayer, while lower than the graphene monolayer. The G/W/G/W/substrate demonstrated a comparable Raman enhancement effect than the G/W/substrate. These differences are due to the different interlayer couplings in heterostructures related to electron transition probability rates, which are further proved by first-principle calculations and probe-pump measurements.
authors.affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University , Shandong, Jinan 250100, P. R. China.
authors.forename: Yang
authors.identifier: 0000-0001-7912-1742
authors.initials: Y
authors.lastname: Tan
authors.affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University , Shandong, Jinan 250100, P. R. China.
authors.forename: Linan
authors.initials: L
authors.lastname: Ma
authors.affiliation: Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University , 200092 Shanghai, P. R. China.|China-EU Joint Center for Nanophononics, School of Physics Science and Engineering, Tongji University , 200092 Shanghai, P. R. China.|Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University , 200092 Shanghai, P. R. China.
authors.forename: Zhibin
authors.identifier: 0000-0002-6843-381X
authors.initials: Z
authors.lastname: Gao
authors.affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University , Shandong, Jinan 250100, P. R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University , Shandong, Jinan 250100, P. R. China.
authors.forename: Feng
authors.identifier: 0000-0002-9277-9810
authors.initials: F
authors.lastname: Chen
keywords: Heterostructure; surface-enhanced Raman scattering