Robust epitaxial growth of two-dimensional heterostructures, multiheterostructures, and superlattices

Abstract

We report a general synthetic strategy for highly robust growth of diverse lateral heterostructures, multiheterostructures, and superlattices from two-dimensional (2D) atomic crystals. A reverse flow during the temperature-swing stage in the sequential vapor deposition growth process allowed us to cool the existing 2D crystals to prevent undesired thermal degradation and uncontrolled homogeneous nucleation, thus enabling highly robust block-by-block epitaxial growth. Raman and photoluminescence mapping studies showed that a wide range of 2D heterostructures (such as WS-WSe and WS-MoSe), multiheterostructures (such as WS-WSe-MoS and WS-MoSe-WSe), and superlattices (such as WS-WSe-WS-WSe-WS) were readily prepared with precisely controlled spatial modulation. Transmission electron microscope studies showed clear chemical modulation with atomically sharp interfaces. Electrical transport studies of WSe-WS lateral junctions showed well-defined diode characteristics with a rectification ratio up to 10.

Nanoscale interfaces made easily

“…Lateral TMD heterostructures can be constructed by 'stitching' the edges of two TMD sheets together using covalent bonds. In the past few years, there has been a flurry of papers [5][6][7][8][9] reporting methods for synthesizing TMD lateral heterostructures using edge epitaxial growth, a method that allows a second TMD to grow at the edge of another, pre-grown TMD crystal. These heterostructures can be fabricated into p-n junctions, which conduct currents in only one direction (a property known as rectification), and constitute one of the building blocks of modern electronic and optoelectronic devices.…”

“…Lateral TMD heterostructures have previously been made in one-step procedures 5,6 that lacked the flexibility to make multi-junction heterostructures or more than one type of heterostructure, or in two-step or multi-step processes that involve many changes of TMD precursors and reaction chambers [7][8][9] . Sahoo and colleagues' method overcomes those constraints in a 'one-pot' procedure -a process that allows several steps to be performed in one reaction chamber.…”

“…This leads to the formation of large fibrin complexes, which are equivalent to blood clots. Moreover, tissue plasminogen activator protein, which is routinely given to people who have had an ischaemic stroke to promote the breakdown of fibrin-containing blood clots, inhibits the death of oligodendrocytes 9 and promotes axonal regeneration 10 . One must assume that these factors, like fibrinogen, access the brain in the absence of a functional BBB, and have roles in determining the success or failure of myelin repair.…”

New designing for nanostructured 2D materials and 2D superlattices

“…Such strategies could change the morphology or component of the substrates, directly impacting the grown products. The epitaxy growth along the edges or from the grains is related to the lattice mismatch, such as the lateral 1T'-MoTe 2 /1H-MoS 2 , 1T'-MoTe 2 /2H-MoTe 2 superlattices and the multinary lateral superlattices of MoS 2 , WS 2 and WSe 2 [4][5][6]. Even so, such a dislocation driven growth is so general that it is possible to obtain other kinds of nanowires or superlattices on the basis of defects in 2D materials.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…Duan et al had an insight into the temperature swing stage between two-step synthesizing methods (Figure 9). [95] The uncontrolled supply of sources always results to undesired homogeneous nuclea- Figure 9 is reproduced with permission from Ref. [95].…”