摘要
Vertical van der Waals(vdW)heterostructures composed of two-dimensional(2D)layered materials have recently attracted substantial interests due to their unique properties.However,the direct synthesis of moirésuperlattice remains a great challenge due to the difficulties in heterogeneous nucleation on smooth vdW surfaces.Here,we report a controllable chemical vapor deposition growth of complete monolayer WS_(2)on highly ordered pyrolytic graphite(HOPG)substrates through the plasma pretreatment.The results show that the morphologies of the grown WS_(2)have a strong dependence on the plasma parameters,including gas composition,source power,and treatment time.It is found that the surface C–C bonds are broken in the plasma pretreated HOPG,and the formed small clusters can act as the nucleation sites for the subsequent growth of WS_(2).Moreover,the height of clusters dominates the growth mode of WS_(2)islands.A transition from a 2D mode to three-dimensional(3D)growth mode occurs when the height is higher than the interlayer spacing of the heterostructure.Besides,diverse moirésuperlattices with different twist angles for WS_(2)/HOPG heterostructures are observed,and the formation mechanism is further analyzed by firstprinciples calculations.
基金
the National Natural Science Foundations of China(Nos.61974123,61874092,and 61804129)
the National Science Fund for Excellent Young Scholars(No.62022068)
the Fundamental Research Funds for the Central Universities(Nos.20720190055 and 20720190058).
