Wafer-Scale, Conformal, and Low-Temperature Synthesis of Layered Tin Disulfides for Emerging Non-Planar and Flexible Electronics.

Two-dimensional (2D) metal dichalcogenides have drawn considerable interest because they offer possibilities for the implementation of emerging electronics. The emerging electronics are moving toward two major directions: vertical expansion of device space and flexibility. However, the development of a synthesis method for 2D metal dichalcogenides that meets all the requirements remains a significant challenge. Here, we propose a promising method for wafer-scale, conformal, and low-temperature (≤ 240 °C) synthesis of single-phase SnS via the atomic layer deposition technique. There is a trade-off relationship between the crystallinity and orientation preference of SnS, which is efficiently eliminated by the two-step growth occurring at different temperatures. Consequently, the van der Waals layers of the highly crystalline SnS2 are parallel to the substrate. Thin film transistors (TFTs) comprising the SnS layer show reasonable electrical performances (field-effect mobility: ~0.8 cmVs and on/off ratio: ~10), which are comparable to that of a single-crystal SnS flake. Moreover, we demonstrate non-planar and flexible TFTs to identify the feasibility of the implementation of future electronics. Both the diagonal-structured TFT and flexible TFT fabricated without a transfer process show electrical performances comparable to those of rigid and planar TFTs. Particularly, the flexible TFT does not exhibit substantial degradation even after 2,000 bending cycles. Our work would provide decisive opportunities for the realization of future electronic devices utilizing 2D metal chalcogenides.