One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy
One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy
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DOI：
10.1038/nature25155
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发表时间：
2018-01-04
期刊：
影响因子：
64.8
通讯作者：
Gutierrez, Humberto R.
中科院分区：
文献类型：
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作者：
Sahoo, Prasana K.;Memaran, Shahriar;Gutierrez, Humberto R.
过渡金属二卤化物(1-15)的二维异质结在低功率、高性能和柔性的电光器件中具有巨大的应用潜力，如隧道晶体管(5，6)、发光二极管(2，3)、光电探测器(2，4)和光伏电池(7，8)。尽管已经通过不同的二维材料(2-4，14)的van der Waals堆积制备了复杂的异质结，但高质量的具有多个结的横向异质结(9-13，15)的原位制备仍然是一个挑战。通过单步(9，11，12)、两步(10，13)或多步(15)生长工艺合成了过渡金属二卤化物侧向异质结构。然而，这些方法缺乏灵活性，无法就地控制单个领域的增长。多结横向异质结构的原位合成不需要多次源或反应器的交换，这是以前方法(9-13，15)的局限性，因为它将边缘暴露在环境污染中，损害了周期性结构中磁区尺寸的均一性，并导致较长的处理时间。在这里，我们报道了一种一锅合成法，使用单一的非均相固体源，连续地制备由过渡金属二盐基单分子层组成的横向多结异质结构。异质结的顺序形成仅通过在水蒸气存在的情况下改变反应气体环境的组成来实现。这使得能够选择性地控制每个过渡金属前体的水诱导氧化(16)和挥发(17)，以及它在衬底上的成核，从而导致不同的过渡金属二卤代化合物的顺序边缘外延。光致发光图证实了带隙的顺序空间调制，原子分辨率图像显示了单一晶体结构中不同过渡金属二卤化物结构域之间的无缺陷横向连接。电传输测量显示，在结的两端有二极管样的响应。我们的新方法比以前的方法提供了更大的灵活性和可控性，以连续生长过渡金属-二卤化物为基础的多结横向异质结构。这些发现可以推广到其他两维材料家族，并为开发复杂和原子薄的平面内超晶格、器件和集成电路奠定基础(18)。
Two-dimensional heterojunctions of transition-metal dichalcogenides(1-15) have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors(5,6), light-emitting diodes(2,3), photodetectors(2,4) and photovoltaic cells(7,8). Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials(2-4,14), the in situ fabrication of high-quality lateral heterostructures(9-13,15) with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step(9,11,12), two-step(10,13) or multi-step growth processes(15). However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches(9-13,15) as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation(16) and volatilization(17) of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the junctions. Our new approach offers greater flexibility and control than previous methods for continuous growth of transition-metal-dichalcogenide-based multi-junction lateral heterostructures. These findings could be extended to other families of two-dimensional materials, and establish a foundation for the development of complex and atomically thin in-plane superlattices, devices and integrated circuits(18).