Substrate Mediation in Vapor Deposition Growth of Layered Chalcogenide Nanoplates: A Case Study of SnSe2

The two-dimensional (2D) nanostructure of layered chalcogenide materials (LCMs) is very interesting, but to make it a useful material platform necessiates the development of sophisticated synthetic control. We present the synthesis of single-crystalline SnSe2 nanoplates by a noncatalytic vapor deposition process and demonstrate that the growth is subject to strong influences from substrates. The effect of substrates is evidenced by a temperature-dependent morphological difference in the nanoplates grown on mica and silicon substrates. At a growth temperature of 280 degrees C, the diameter of the nanoplates grown on mica is larger than those grown on silicon by a ratio of 6.2. This ratio substantially decreases to be unity (1.04) at a higher temperature of 420 degrees C. Additionally, different from the nanoplates grown on silicon, which always show a well-defined hexagonal shape, the nanoplates grown on mica exhibit an irregular shape at low temperature and can gradually evolve into the hexagonal shape with increasing temperature. Our dynamics analysis suggests that the observed temperature-dependent morphological difference can be specifically correlated to the migration of SnSe2 adatoms on the surface of substrates. SnSe2 adatoms may migrate on mica more easily than on silicon substrates because of the presence of dangling bonds at the surface of silicon. The role of the facile migration on mica in the nanoplate growth may be further confirmed by a correlation between the nanoplate diameter and the distance between neighboring nanoplates. While the focus is on SnSe2, we believe that this understanding can apply to the growth of two-dimensional (2D) nanostructures of other layered chalcogenide materials (LCMs). It may pave the way for the development of a general synthetic paradigm that leverages the effect of substrates to control the growth of 2D LCM nanostructures.