title: Enhanced Raman Scattering on In-Plane Anisotropic Layered Materials.
abstract: Surface-enhanced Raman scattering (SERS) on two-dimensional (2D) layered materials has provided a unique platform to study the chemical mechanism (CM) of the enhancement due to its natural separation from electromagnetic enhancement. The CM stems from the charge interactions between the substrate and molecules. Despite the extensive studies of the energy alignment between 2D materials and molecules, an understanding of how the electronic properties of the substrate are explicitly involved in the charge interaction is still unclear. Lately, a new group of 2D layered materials with anisotropic structures, including orthorhombic black phosphorus (BP) and triclinic rhenium disulfide (ReS2), has attracted great interest due to their unique anisotropic electrical and optical properties. Herein, we report a unique anisotropic Raman enhancement on few-layered BP and ReS2 using copper phthalocyanine (CuPc) molecules as a Raman probe, which is absent on isotropic graphene and h-BN. According to detailed Raman tensor analysis and density functional theory calculations, anisotropic charge interactions between the 2D materials and molecules are responsible for the angular dependence of the Raman enhancement. Our findings not only provide new insights into the CM process in SERS, but also open up new avenues for the exploration and application of the electronic properties of anisotropic 2D layered materials.
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Lin
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Liangbo
authors.initials: L
authors.lastname: Liang
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Ling
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Shuqing
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Nannan
authors.initials: N
authors.lastname: Mao
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.|Computer Science & Mathematics Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Sumpter
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Vincent
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Lianming
authors.initials: L
authors.lastname: Tong
authors.affiliation: Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang