酞菁铜与MoS_2(0001)范德瓦耳斯异质结研究

利用光电子能谱、原子力显微镜以及低能电子衍射等表面研究手段系统研究了真空沉积生长的酞菁铜薄膜与衬底MoS2(0001)之间的范德瓦耳斯异质结界面电子结构和几何结构.角分辨光电子能谱清楚地再现了MoS2(0001)衬底在Γ点附近的能带结构.低能电子衍射结果表明,CuPc薄膜在MoS2(0001)表面沿着衬底表面11ˉ20],1ˉ210]和ˉ2110]三个晶向有序生长,反映了衬底对CuPc的影响.原子力显微镜结果表明,CuPc在MoS2衬底上遵循层状-岛状生长模式:在低生长厚度下(单层薄膜厚度约为0.3 nm),CuPc分子平面平行于MoS2表面上形成均匀连续的薄膜;在较高的沉积厚度下,CuPc沿衬底晶向形成棒状晶粒,表现出明显的各向异性.光电子能谱显示界面偶极层为0.07 eV,而且能谱在膜厚1.2 nm饱和,揭示了酞菁铜与MoS2(0001)范德瓦耳斯异质结的能级结构.

van der Waals heterostructure about CuPc/MoS2(0001)

Molecular packing and interfacial electronic properties of well-ordered organic semiconductor, copper phthalocyanine, thin films grown on MoS₂(0001) are studied with low energy electron diffraction (LEED) optics, atomic force microscope (AFM) and photoelectron spectroscopy (PES). The band structure of MoS₂(0001) around the Γ point of the surface Brillouin zone is given by angle-resolved photoelectron spectroscopy. The LEED patterns indicate that three equivalent well-ordered two-dimensional square lattices are formed in CuPc monolayer thin film along three surface crystalline axes (1120], 1210] and 2110]) of MoS₂ (0001) substrate, respectively. The AFM measurements show that the growth of CuPc on MoS₂ (0001) occurs in a Stranski-Krastanov mode. The CuPc molecule can be flat-laying on MoS₂(0001) at low coverage (～0.3 nm), but form strip-like crystals along the surface crystal axes of MoS₂ (0001) at high coverage (>2.4 nm). The CuPc molecule shows obvious anisotropy, indicating that the molecular plane is not parallel to the MoS₂ surface. The PES measurements show there is no charge transfer process at the interface, indicating weak van der Waals interaction between CuPc and MoS₂(0001).
Keywords： organic semiconductor photoemission spectroscopy electronic structure heterostructure