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Role of Bilayer Graphene Microstructure on the Nucleation of WSe2 Overlayers
ACS Nano ( IF 15.8 ) Pub Date : 2023-06-27 , DOI: 10.1021/acsnano.2c12621 Saiphaneendra Bachu 1 , Malgorzata Kowalik 2, 3 , Benjamin Huet 3, 4 , Nadire Nayir 2, 3, 5 , Swarit Dwivedi 2, 3 , Danielle Reifsnyder Hickey 1, 3, 6 , Chenhao Qian 1 , David W Snyder 4 , Slava V Rotkin 7 , Joan M Redwing 1, 3 , Adri C T van Duin 1, 2, 3 , Nasim Alem 1, 3
ACS Nano ( IF 15.8 ) Pub Date : 2023-06-27 , DOI: 10.1021/acsnano.2c12621 Saiphaneendra Bachu 1 , Malgorzata Kowalik 2, 3 , Benjamin Huet 3, 4 , Nadire Nayir 2, 3, 5 , Swarit Dwivedi 2, 3 , Danielle Reifsnyder Hickey 1, 3, 6 , Chenhao Qian 1 , David W Snyder 4 , Slava V Rotkin 7 , Joan M Redwing 1, 3 , Adri C T van Duin 1, 2, 3 , Nasim Alem 1, 3
Affiliation
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Over the past few years, graphene grown by chemical vapor deposition (CVD) has gained prominence as a template to grow transition metal dichalcogenide (TMD) overlayers. The resulting two-dimensional (2D) TMD/graphene vertical heterostructures are attractive for optoelectronic and energy applications. However, the effects of the microstructural heterogeneities of graphene grown by CVD on the growth of the TMD overlayers are relatively unknown. Here, we present a detailed investigation of how the stacking order and twist angle of CVD graphene influence the nucleation of WSe2 triangular crystals. Through the combination of experiments and theory, we correlate the presence of interlayer dislocations in bilayer graphene with how WSe2 nucleates, in agreement with the observation of a higher nucleation density of WSe2 on top of Bernal-stacked bilayer graphene versus twisted bilayer graphene. Scanning/transmission electron microscopy (S/TEM) data show that interlayer dislocations are present only in Bernal-stacked bilayer graphene but not in twisted bilayer graphene. Atomistic ReaxFF reactive force field molecular dynamics simulations reveal that strain relaxation promotes the formation of these interlayer dislocations with localized buckling in Bernal-stacked bilayer graphene, whereas the strain becomes distributed in twisted bilayer graphene. Furthermore, these localized buckles in graphene are predicted to serve as thermodynamically favorable sites for binding WSex molecules, leading to the higher nucleation density of WSe2 on Bernal-stacked graphene. Overall, this study explores synthesis–structure correlations in the WSe2/graphene vertical heterostructure system toward the site-selective synthesis of TMDs by controlling the structural attributes of the graphene substrate.
中文翻译：
双层石墨烯微观结构对 WSe2 覆盖层成核的作用
在过去的几年中，通过化学气相沉积（CVD）生长的石墨烯作为生长过渡金属二硫属化物（TMD）覆盖层的模板而受到重视。由此产生的二维（2D）TMD/石墨烯垂直异质结构对于光电和能源应用具有吸引力。然而，CVD 生长的石墨烯的微观结构异质性对 TMD 覆盖层生长的影响相对未知。在这里，我们详细研究了 CVD 石墨烯的堆叠顺序和扭转角如何影响 WSe 2三角形晶体的成核。通过实验和理论的结合，我们将双层石墨烯中层间位错的存在与 WSe 2与扭曲双层石墨烯相比，伯纳尔堆叠双层石墨烯顶部WSe 2的成核密度更高。扫描/透射电子显微镜（S/TEM）数据表明，层间位错仅存在于伯纳尔堆叠的双层石墨烯中，而不存在于扭曲的双层石墨烯中。原子ReaxFF反作用力场分子动力学模拟表明，应变弛豫促进了伯纳尔堆叠双层石墨烯中具有局部屈曲的层间位错的形成，而应变分布在扭曲双层石墨烯中。此外，石墨烯中的这些局部扣预计将成为结合 WSe x的热力学有利位点分子，导致伯纳尔堆叠石墨烯上WSe 2的成核密度更高。总的来说，本研究探索了WSe 2 /石墨烯垂直异质结构系统中的合成-结构相关性，通过控制石墨烯基底的结构属性来实现TMD的位点选择性合成。
更新日期：2023-06-27
中文翻译：
双层石墨烯微观结构对 WSe2 覆盖层成核的作用
在过去的几年中，通过化学气相沉积（CVD）生长的石墨烯作为生长过渡金属二硫属化物（TMD）覆盖层的模板而受到重视。由此产生的二维（2D）TMD/石墨烯垂直异质结构对于光电和能源应用具有吸引力。然而，CVD 生长的石墨烯的微观结构异质性对 TMD 覆盖层生长的影响相对未知。在这里，我们详细研究了 CVD 石墨烯的堆叠顺序和扭转角如何影响 WSe 2三角形晶体的成核。通过实验和理论的结合，我们将双层石墨烯中层间位错的存在与 WSe 2与扭曲双层石墨烯相比，伯纳尔堆叠双层石墨烯顶部WSe 2的成核密度更高。扫描/透射电子显微镜（S/TEM）数据表明，层间位错仅存在于伯纳尔堆叠的双层石墨烯中，而不存在于扭曲的双层石墨烯中。原子ReaxFF反作用力场分子动力学模拟表明，应变弛豫促进了伯纳尔堆叠双层石墨烯中具有局部屈曲的层间位错的形成，而应变分布在扭曲双层石墨烯中。此外，石墨烯中的这些局部扣预计将成为结合 WSe x的热力学有利位点分子，导致伯纳尔堆叠石墨烯上WSe 2的成核密度更高。总的来说，本研究探索了WSe 2 /石墨烯垂直异质结构系统中的合成-结构相关性，通过控制石墨烯基底的结构属性来实现TMD的位点选择性合成。
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