局部气流扰动下转角双层MoS2的合成及层间角的表征

Synthesis of hetero-site nucleation twisted bilayer MoS2 by local airflow perturbations and interlayer angle characterization

近些年,随着对二维材料的深入研究,人们发现当二维材料以不同的旋转角度堆叠在一起时,表现出了比单层二维材料更强大、更复杂的物理性质,这使得其在电子器件、光电子器件、自旋电子器件以及能源转换和存储等领域有着极其广阔的应用前景。在转角材料中,以二硫化钼(MoS2)为代表的转角双层过渡金属二硫化物(TMDC)。由于其具有独特的摩尔超晶格结构,会在特定角度下诱导产生电子平带,这引起了人们极大的兴趣。均匀莫尔势的高质量转角双层TMDC对于发现强关联效应、非常规超导、量子反常霍尔效应和拓扑相也是至关重要。然而,由于非稳定态转角双层材料的合成需要克服较高的能量壁垒,利用化学气相沉积(CVD)合成大面积高质量宽角分布的转角双层MoS2(tBMo S2)的方法仍然缺乏。本文展示了一种改进的CVD方法,该方法采用局部气流扰动,通过使用异位成核策略来生长高比例且具有任意扭转角度的tBMo S2。此外,文章还使用无损几何方法(原子力显微图像)和TEM选区电子衍射(SAED)对角度进行了表征,并使用拉曼光谱分析了角度和层间耦合的关系。

Twisted bilayer transition metal dichalcogenides including MoS2 have attracted great interest due to their unique Moirésuperlattice induced electronic flat bands.High-quality twisted bilayer TMDs with uniform Moirépotentials are essential for the discovery of strong correlation effects,unconventional superconductivity,and quantum anomalous Hall effect.However,the synthesis of large-area high-quality twisted bilayer MoS2(tBMoS2)using chemical vapor deposition(CVD)is still absent,which needs to overcome the formation energy barrier for nonstable twist bilayers.Here,we demonstrate a novel CVD approach with local airflow perturbation for growing tBMoS2 by a hetero-site nucleation strategy,which enables the nucleation of the second layer at the different site from the first layer nucleation site with arbitrary twist angles.Furthermore,the accurate determination of interlayer twist angles in tBMoS2 is crucial for studying structure-physical properties relationship.We quantitatively compare the measurement accuracy between a geometrical method and TEM selected area electron diffractions(SAED),in which the measured angles from TEM-SAED show much smaller angle errors.Finally,Raman spectra show that the interlayer coupling can be tuned by the twist angles.Our study opens an avenue for the controllable growth of tBMoS2 for both fundamental research and practical applications.