Past Events

Abstract

The development of two-dimensional (2D) layered materials is driven both by fundamental interest and their potential applications. Atomically thin 2D Transition metal dichalcogenide (TMD) materials provide a wide range of basic building blocks with unique electrical, optical, and thermal properties which do not exist in their bulk counterparts. Our recent demonstration in vapor phase growth of TMD monolayer [1] has stimulated the research in growth and applications [2]. In this presentation, I would start with the discussion on the synthesis and characterizations of crystalline MoS₂ and WSe₂ monolayers. These layer materials can be transferred to desired substrates, making them suitable building blocks for constructing multilayer stacks for various applications [3].

The interlayer interaction based on van der Waals force enables the possibility to assemble different 2D materials into arbitrarily and vertically stacked heterostructures. Heterostructures of 2d materials formed by vertical stacking have been realized recently via transfer of their exfoliated flakes, where their properties are dominated by the stacking orientation and strength of interlayer coupling. The method to determine valence band and conduction band alignment for various TMD materials is proposed [4].

Another very attractive structure is the lateral heterostructure, where the junction is atomically sharp and the active region can be as narrow as few strings of atoms at the junction areas. This structure offers much easier band offset tuning since materials are spatially separated. The direct growth of such lateral heterostructures will be presented [5]. These unique 2D heterostructures have abundant implications for many potential applications. Preliminary results and perspectives on monolayer electronics shall be discussed.

_{[1] Adv. Mater. 24, 2320 (2012); ACS Nano 8, 923 (2014).
[2] Nature Chem. 5, 263-275 (2013); Chem. Soc. Rev. 44, 2744 (2015)
[3] ACS Nano 8, 2951 (2014); ACS Nano 8, 8317 (2014); Adv. Mater. 26,4838 (2014)
[4] Nature Comm. 6, 7666 (2015)
[5] Science 349, 524 (2015)}

Coffee and tea will be served 20 minutes prior to the seminar.
Anyone interested is welcome to attend.