Atomic layer deposition of stable 2D materials

Abstract

Following the graphene isolation, strong interest in two dimensional (2D) materials has been driven by their outstanding properties. Their typical intrinsic structure, including strong in-plane covalent bonding and weak out-of-plane Van der Waals interaction, makes them highly promising in diverse areas such as electronics, catalysis, and environment. Growth of 2D materials requires a synthesis approach able to control the deposition onto a support at the atomic scale. Thanks to their simplicity, versatility and ability to control thickness at the angstrom level, Atomic Layer Deposition (ALD) and its variant Atomic Layer Etching (ALET) appear as ones of the most suited techniques to synthesize 2D materials. The development of ALD technique for fabricating 2D materials in the last ten years justifies reviewing its most recent groundbreaking discoveries and progresses. Particular attention will be paid to stable 2D materials especially graphene, h-BN, Mo and W dichalcogenides and few monolayered metal oxides. Specificities and outputs of ALD for 2D material as well as emerging directions and remaining technical challenges will be highlighted. layers. This kind of materials exhibits interesting properties related to their size restriction: electronic confinement, modifying both optical and electronic properties, and high surface to volume ratio that affects the mechanical and chemical properties. 4,5 Therefore, 2D materials are highly attractive due to their potential in cutting edge domains such as micro-, and opto-electronics 4,6 as well as renewable energy, 4,7-9 catalysis, 10,11 gas sensing 12,13 and environment. 4,7,14,15 They are also exciting because of their possibility to be stacked into VdW heterostructures combining and/or tuning their chemical and physical properties. 6,[16][17][18] However, since 2D materials are atomically thin, a suitable manufacturing process capable of controlling their fabrication in terms of structure, composition, thickness, defects, purity and crystallinity without degradation of their original properties is necessary. Two approaches can be considered: the top-down and bottom-up synthetic routes. 19 Historically, top-down approach has first been developed using mechanical and chemical exfoliation techniques, 1,2,20,21 the first example being the well-known graphene exfoliation using scotch tape.Later on, etching processes have been adapted. Recently, Atomic Layer Etching (ALET), 22 the top down variant of Atomic Layer Deposition (ALD), has been introduced for fabricating 2D materials. On the other hand, bottom-up techniques have largely been developed using conventional thin film deposition. These techniques include sputtering, evaporation and Chemical Vapor Deposition (CVD). 3,23,24 However, they are mainly based on either high temperature processes, substrate restrictive deposition or low thickness control. 21,25,26 Amongst all the fabrication processes, ALD appears to be one of the most suited techniques to synthesize 2D materials, because of its simplicity, versatility and c...

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

“…Deposition of TMDCs by ALD and their optoelectronic applications reported up to November 2018 have been reviewed by the authors. [47] Furthermore, Hao et al [48] have provided an extensive review on ALD of 2D materials up to early 2018, whereas Huang and Liu [49] have reviewed deposition of MoS 2 by ALD. In early 2020, Cai et al [50] published another broad review concerning deposition of 2D materials by ALD.…”

Low-Temperature Phase-Controlled Synthesis of Titanium Di- and Tri-sulfide by Atomic Layer Deposition

“…The ALD method has advantages such as precise thickness control and conformal growth over a large area. 28,29 In addition, most ALD processes are performed at low temperatures (<450 °C), which are favorable for device manufacturing schemes. 29−31 Recently, interest in controlling the phase as well as the composition of metal-oxide-based materials has been made viable by ALD.…”

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

“…40,41 In recent years, ALD has been increasingly studied for the deposition of various TMDCs, although so far most studies have focused on MoS2. 42 On the contrary, only a few processes have been demonstrated for WS2. WF6 does not enable film growth with H2S unless a H2 plasma pulse [43][44][45][46] is added before the H2S pulse or either a ZnS substrate or a ZnEt2 pulse [47][48][49] is applied.…”