Low‐Temperature Wafer‐Scale Deposition of Continuous 2D SnS₂ Films

Abstract

Semiconducting 2D materials, such as SnS , hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few-layer SnS films has remained a great challenge. Herein, continuous wafer-scale 2D SnS films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low-temperature (250 °C) postdeposition annealing. Uniform coating of large-area and 3D substrates is demonstrated owing to the unique self-limiting growth mechanism of atomic layer deposition. Detailed characterization confirms the 1T-type crystal structure and composition, smoothness, and continuity of the SnS films. A two-stage deposition process is also introduced to improve the texture of the films. Successful deposition of continuous, high-quality SnS films at low temperatures constitutes a crucial step toward various applications of 2D semiconductors.

Crystalline tungsten sulfide thin films by atomic layer deposition and mild annealing

“…This approach has proven to be effective in producing crystalline and smooth SnS2 films while retaining a low thermal budget and requiring no additional annealing equipment. 62 Initially, temperatures from 300 to 500 °C were tested for approximately 9 nm thick tungsten sulfide films deposited using 100 cycles.…”

Controlling Atomic Layer Deposition of 2D Semiconductor SnS2 by the Choice of Substrate

“…Film Deposition: SnS 2 films were deposited using a commercial hotwall, cross-flow type ALD reactor (F120, ASM Microchemistry) using tin(IV) acetate [Sn(OAc) 4 ] and hydrogen sulfide (H 2 S) as precursors. [36] Sn(OAc) 4 (Alfa Aesar) was evaporated from an open glass boat held at 130 °C inside the reactor and pulsed by inert gas valving. Sn(OAc) 4 is air and moisture sensitive and was handled in a glove box under nitrogen until it was transferred into the reactor.…”

“…In thicker films, a large part of the grains were tilted by ≈10° (α ≈ 80°) with respect to the substrate, which is similar to the films grown on SiO 2 /Si. [36] The SnS 2 films deposited on sapphire remained smooth after the annealing, as evidenced by the low roughness values and visibility of the 2 Å high sapphire steps in atomic force microscopy (AFM) images ( Figure S9, Supporting Information). Even the thinnest film deposited using 25 cycles crystallized upon annealing, as shown by in-plane X-ray diffraction (XRD) (Figure 2b; Figure S10, Supporting Information).…”

“…In contrast, a 25 cycle SnS 2 film grown on SiO 2 /Si was smooth as deposited, but became clearly discontinuous after the annealing. [36] Low energy ion scattering (LEIS) measurements on the annealed 25-250 cycle films were performed to assess film coverage as a function of film thickness. In addition to the SnS 2 films on sapphire, films deposited on SiO 2 /Si were examined for comparison.…”

“…[66] Herein, we have prepared air-stable SnS 2 thin films on different substrates by ALD using tin(IV) acetate and hydrogen sulfide at 150 °C followed by mild H 2 S/N 2 annealing at 250-300 °C to crystallize the films. [36] This process has been shown to deposit continuous, high-quality SnS 2 films from approximately two to ten monolayers in thickness on SiO 2 /Si substrates. We show that crystalline SnS 2 films can be successfully grown on a variety of substrates with clear differences in film continuity, morphology, and crystallinity.…”