Bachelor of Chem Engineering, Seoul National University (2003)
Master of Science in Engr, Seoul National University (2005)
Doctor of Philosophy, Seoul National University (2010)
Yi Cui, Postdoctoral Faculty Sponsor
Vertical Heterostructure of Two-Dimensional MoS2 and WSe2 with Vertically Aligned Layers.
2015; 15 (2): 1031-1035
Two-dimensional (2D) layered materials consist of covalently bonded 2D atomic layers stacked by van der Waals interactions. Such anisotropic bonding nature gives rise to the orientation-dependent functionalities of the 2D layered materials. Different from most studies of 2D materials with their atomic layers parallel to substrate, we have recently developed layer vertically aligned 2D material nanofilms. Built on these developments, here, we demonstrate the synthesis of vertical heterostructure of n-type MoS2 and p-type WSe2 with vertically aligned atomic layers. Thin film of MoS2/WSe2 vertical structure was successfully synthesized without significant alloy formation. The heterostructure synthesis is scalable to a large area over 1 cm(2). We demonstrated the pn junction diode behavior of the heterostructure device. This novel device geometry opens up exciting opportunities for a variety of electronic and optoelectronic devices, complementary to the recent interesting vertical heterostructures with horizontal atomic layers.
View details for DOI 10.1021/nl503897h
View details for PubMedID 25590995
In situ observation of divergent phase transformations in individual sulfide nanocrystals.
2015; 15 (2): 1264-1271
Inorganic nanocrystals have attracted widespread attention both for their size-dependent properties and for their potential use as building blocks in an array of applications. A complete understanding of chemical transformations in nanocrystals is important for controlling structure, composition, and electronic properties. Here, we utilize in situ high-resolution transmission electron microscopy to study structural and morphological transformations in individual sulfide nanocrystals (copper sulfide, iron sulfide, and cobalt sulfide) as they react with lithium. The experiments reveal the influence of structure and composition on the transformation pathway (conversion versus displacement reactions), and they provide a high-resolution view of the unique displacement reaction mechanism in copper sulfide in which copper metal is extruded from the crystal. The structural similarity between the initial and final phases, as well as the mobility of ions within the crystal, are seen to exert a controlling influence on the reaction pathway.
View details for DOI 10.1021/nl504436m
View details for PubMedID 25602713
- Two-dimensional layered transition metal disulphides for effective encapsulation of high-capacity lithium sulphide cathodes NATURE COMMUNICATIONS 2014; 5