Paper TF-TuM3
Synthesis of Single Phase Two-dimensional SnS₂ by Plasma-enhanced Atomic Layer Deposition

Tuesday, October 23, 2018, 8:40 am, Room 101A

Two-dimensional (2-D) metal chalcogenides have received great attention because of their unique characteristics. A challenge in implementing 2-D metal chalcogenides in emerging devices is to synthesize a well-crystallized layer over large areas at temperatures compatible with current fabrication processes. Tin disulfide, a n-type layered semiconductor, is a promising candidate for realizing large-area growth at low temperatures because of its low melting point. However, tin sulfides exist in various phases such as SnS, Sn₂S₃, and SnS₂. It is challenging to form a single phase SnS₂ at low temperatures.

Here, we demonstrated the synthesis of high-quality SnS₂ by plasma-enhanced atomic layer deposition (PEALD). All the processes were performed below 300 ^oC, which is compatible with current electronic devices. Stoichiometric SnS₂ films were formed. It was verified from various techniques such as Raman spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction that a single phase of SnS₂ was formed. It was found that the microstructure of the SnS₂ films was strongly dependent on the growth temperature. Vertically aligned SnS₂ flakes were observed in the SnS2 grown at relatively high temperatures (210 - 270 ^oC). Through a two-step process – a seed layer growth at low temperature (150 ^oC) and a main layer growth at high temperatures (240 – 270 ^oC), well crystallized SnS₂ layers were aligned in parallel to the substrate. Moreover, the properties of field-effect transistor using the SnS₂ films were investigated. A high on/off ratio of ~ 10⁶ and a moderate field-effect mobility of ~ 1 cm²/Vs were achieved from the devices utilizing SnS₂ grown by PEALD.