Chemical Vapor Deposition of 2D Materials and Heterostructures
Ariel Ismach a
a Department of Materials Science and Engineering, Tel Aviv University
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#Sol2D19. Two Dimensional Layered Semiconductors
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Efrat Lifshitz, Cristiane Morais Smith and Doron Naveh
Invited Speaker, Ariel Ismach, presentation 311
Publication date: 16th July 2019

The ability to synthesize large-area and high quality atomic films is a prerequisite for their successful integration into a wide variety of novel and existing technologies. Here we show the growth of transition metal dichalcogenides (MoS2, WS2 and WSe2) via modified chemical vapor deposition (CVD) methods using volatile precursors [1,2]. The use of high vapor pressure precursors allows for the controlled delivery to the growth sample [2], and therefore, suitable for homogeneous and large-scale synthesis, as required for many applications. However, one of the problems with these precursors is the small domain size usually obtained. In order to address these issues, two different concepts were implemented and will be described: i. Seeded-growth and, ii. Pulsed-growth approaches. In the first, and following the success in growing 0 (QDs, NPs), 1 (NWs, NTs), 2 (films) and 3D crystals, the growth of 2D materials is nucleated at well-defined seeds. The description of the methodology as well as the influence of the seed-material on the grown layered domains will be described. In the second, a modified approach in which the metal and chalcogen precursors are delivered in a pulsed fashion is demonstrated. This approach allows to achieve a ten-fold increase in the domain size, from ~10 nm (or below) to ~10s of microns. Moreover, we demonstrate that the growth kinetics is highly dependent on the surface chemistry and by controlling it, the growth of ad-layers is inhibited and thus, more than 95% monolayer films are obtained.  Another advantage of using volatile precursors is the ability to control the lateral and vertical heterostructures formation, and will be described as well. Following this work and in order to expand our growth capabilities, the growth of monochalcogenides using lessons learned while growing TMDs will be briefly described.

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