Centimeter-level MoS2 films with controllable number of layers by face-to-face chemical vapor deposition strategy.

Two-dimensional layered transition metal dichalcogenides (TMDCs) are highly promising in field-effect-transistors (EFTs), photodetectors, flexible devices, but the limitation of uncontrollable size and number of layers is a huge challenge for the development of these devices. Although some breakthroughs like wafer-level MoS 2 have been achieved on specific substrates such as copper foil or sapphire using advanced chemical vapor deposition, electrical and optoelectronic testing requires the transfer of material from these substrates to SiO 2 /Si substrates. In this paper, we developed a face-to-face confined space CVD scheme for the preparation of centimeter-level MoS 2 thin films on amorphous SiO 2 /Si substrate. In contrast to traditional confined-space CVD scheme where the MoO 3 powder is often piled like a small hill in the small quartz boat, The MoO 3 powder is evenly spread in the small quartz boat, facing directly up to the growing substrate with a "face-to-face" growth mode. Therefore, the nucleation centers are uniformly distributed on the growing substrate, finally resulting in a uniform and clean continuous film originating from the coalescence of numerous MoS 2 domains grown up from these nucleation centers. The layer number can be well controlled by adjusting growing parameters like growing temperature, gas flow rate and growth time. Our facile but robust face-to-face growth strategy may be a great supplementary to the wafer-level growth of 2D TMDCs. • We developed a face-to-face confined space CVD method. • We achieved centimeter-level MoS 2 films by this method. • The resultant films are uniform, continuous and clean. • The layer number can be well controlled. [ABSTRACT FROM AUTHOR]