Abstract
Two-dimensional MoS2 film can grow on oxide substrates including Al2O3 and SiO2. However, it cannot grow usually on non-oxide substrates such as a bare Si wafer using chemical vapor deposition. To address this issue, we prepared as-synthesized and transferred MoS2 (AS-MoS2 and TR-MoS2) films on SiO2/Si substrates and studied the effect of the SiO2 layer on the atomic and electronic structure of the MoS2 films using spherical aberration-corrected scanning transition electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The interlayer distance between MoS2 layers film showed a change at the AS-MoS2/SiO2 interface, which is attributed to the formation of S–O chemical bonding at the interface, whereas the TR-MoS2/SiO2 interface showed only van der Waals interactions. Through STEM and EELS studies, we confirmed that there exists a bonding state in addition to the van der Waals force, which is the dominant interaction between MoS2 and SiO2. The formation of S–O bonding at the AS-MoS2/SiO2 interface layer suggests that the sulfur atoms at the termination layer in the MoS2 films are bonded to the oxygen atoms of the SiO2 layer during chemical vapor deposition. Our results indicate that the S–O bonding feature promotes the growth of MoS2 thin films on oxide growth templates.
Highlights
Transition metal dichalcogenides, such as M oS2, have attracted much interest because of their remarkable electrical, mechanical, thermal, and optical properties
The final aim of this study is figuring out the main reason why MoS2 is deposited only on oxide substrates such as SiO2, Al2O3 and understanding how the S iO2 layer affects the structures of MoS2 films when Mo is sulfurized through chemical vapor deposition (CVD) [11,12,13]
The interlayer distance of the As-synthesized MoS2 (AS-MoS2) film exhibited a change at the AS-MoS2/SiO2 interface, which was attributed to the formation of S–O chemical bonding at the interface
Summary
Transition metal dichalcogenides, such as M oS2, have attracted much interest because of their remarkable electrical, mechanical, thermal, and optical properties. Recent studies have focused on the large-scale growth of MoS2 films, which is mainly carried out on A l2O3 and SiO2/Si substrates [11,12,13,14]. It has been reported that some substrates such as SiO2/Si and sapphire enable the largescale deposition of M oS2 films. Microscopic evidence showing the interaction between the chemicalvapor-deposited MoS2 and the SiO2 growth template has not been observed. Microscopic studies are mainly focused on the atomic and electronic structures of MoS2, using transmission electron microscopy (TEM) and aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), which can directly observe materials on an atomic level. Crystal and atomic structures with various defects have been discovered using a combination of ab-initio calculations [4, 11,12,13,14, 16,17,18,19,20,21,22]
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