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

Abstract

been explored. The 2D semiconductors, such as MoS 2 , have become the topic of particularly active research due to the crucial role of semiconductors in modern microelectronics. [7-11] Tin disulfide (SnS 2) has recently emerged as a highly interesting 2D semiconductor. [12,13] It crystallizes in the CdI 2-type 2D structure (1T phase) similar to many TMDCs [12,14] and has a fairly large, indirect band gap of approximately 2.2 eV in bulk [13,15] and 2.4−2.6 eV as a monolayer. [15,16] SnS 2 has already shown performance comparable to the benchmark 2D semiconductor, MoS 2 , in applications such as FETs [9,12,17-19] and photodetectors. [12,20] Furthermore, possible reduction in shortchannel leakage [20,21] due to the larger, indirect band-gap of SnS 2 and higher predicted mobility [22] compared to MoS 2 make SnS 2 a favorable material for electronics. Other promising applications for SnS 2 include lithium and sodium-ion batteries, [23,24] gas sensing, [25] and various kinds of catalysis. [26-28] Synthesis of 2D materials including SnS 2 is, however, a major obstacle for the realization of practical applications. An ideal synthesis method should offer high material quality, monolayer-level thickness control as well as good uniformity on large areas and complex shapes-preferably all at low processing temperatures. The substrate is an integral part of the deposition process and applications, and there are great needs both for methods capable of directly synthesizing 2D materials on different substrates, as well as for methods depositing highquality materials on single-crystalline substrates. The latter route could be combined with a transfer of the deposited material onto another substrate, if needed. [29-31] High-quality, few-layer SnS 2 has been produced from bulk crystals by micromechanical exfoliation, [12,17] but this method offers very limited control over the flake size and thickness and has extremely low throughput. Vapor-phase deposition techniques, such as chemical vapor deposition (CVD) and atomic layer deposition (ALD), are promising techniques for the deposition of 2D materials. Thus far, CVD has been mostly used to produce high-quality, isolated few-layer flakes of SnS 2 at 450-700 °C. [16,18,32,33] CVD of continuous SnS 2 films was demonstrated recently, but films below 3-4 nm in thickness remained discontinuous and even 15 nm thick films contained some holes. [34,35] ALD has been used to deposit continuous SnS 2 films with thicknesses from approximately two up to tens of monolayers. [36-41] In addition to thermal ALD processes, [36-39] Semiconducting 2D materials, such as SnS 2 , hold great promise in a variety of applications including electronics, optoelectronics, and catalysis. However, their use is hindered by the scarcity of deposition methods offering necessary levels of thickness control and large-area uniformity. Herein, a low-temperature atomic layer deposition (ALD) process is used to synthesize up to 5 × 5 cm 2 continuous, few-layer SnS 2 films on a variety of substrates, including SiO 2 /Si, S...

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

“…[129,130] The possibility of vdW epitaxy of ALD TMDCs has been presented, but needs further improvement to fully utilize its potential. [126,128,131] One important issue related to the substrate is whether the ALD-grown TMDCs bond covalently to the substrate (x). In an ideal case, an interface with only vdW bonds between the film and the substrate would be formed.…”

“…[ 129,130 ] The possibility of vdW epitaxy of ALD TMDCs has been presented, but needs further improvement to fully utilize its potential. [ 126,128,131 ]…”

“…amorp., ann. 15-70 nm) - [131] Sn(dmamp) 2 + H 2 S plasma 150-240 (300, H 2 S) ≈1-20 ML films to rough films (as-dep. partly cryst., ann ≈10-30 nm)…”

Mechanical Behavior of Blisters Spontaneously Formed by Multilayer 2D Materials

“…It is well known that the interfacial adhesion is not only beneficial to guide the growth of 2D materials and the efficient transfer from a donor substrate to a target substrate to fabricate various 2D material based vdW devices, [35,51,52] but also a prerequisite to extract the intrinsic mechanical parameters (e.g., bending stiffness) of 2D materials through stepping methodology. [33,34] Experimentally, several methods have been developed to measure interfacial adhesion energy between 2D materials and its supported substrates, such as pressurized blister, [27,53] buckle metrology, [54] and doublecantilever beam fracture mechanics testing.…”

Nucleation and growth studies of large-area deposited WS2 on flexible substrates

“…In covalent heteroepitaxy, similarity in crystalline symmetry, lattice parameters, and thermal expansion coefficients between the substrate and the epitaxial crystalline overlayer is required to suppress elastic strain and the nucleation of defects in the crystal. Although the lattice constant of mica is larger than that of most TMDCs, high quality MoSe 2 [38] and SnS 2 [39] layers have been successfully grown on muscovite by vdW epitaxy. In this study, we also use the layerstructured muscovite mica (figure S1) as a substrate to study the CVD growth process on a crystalline, flexible substrate.…”