Role of an Al₂O₃ Passivation Layer during Annealing of 2D-SnS₂ Thin Films Grown by Atomic Layer Deposition

Abstract

Tin disulfide (SnS2) is a two-dimensional (2D) post-transition metal chalcogenide (p-TMDC) with considerable potential to compete with other benchmarked 2D-TMDC materials such as MoS2 and WS2. Compared with other 2D-TMDC materials, SnS2 has the strong advantage of being synthesized at low temperature. However, a lower synthetic temperature of SnS2 lessens its thermal stability at high temperature. Thus, many researchers have cautiously handled SnS2 when exposing it to high process temperature. In this paper, 2D SnS2 thin films with and without an Al2O3 passivation layer were prepared by atomic layer deposition (ALD), and post-annealing was performed under a H2S environment at various temperatures. SnS2 thin film with an Al2O3 passivation layer is more thermally stable at higher temperature during post-annealing than is SnS2 thin film without an Al2O3 passivation layer. Furthermore, higher temperatures used during post-annealing facilitate enhanced crystallinity of 2D SnS2 thin films without evaporation. The enhanced crystallinity is mainly attributed to the presence of an Al2O3 passivation layer that blocks evaporation of SnS2 and enables increased processing temperature in post-annealing.

Melting, Crystallization, and Alloying Dynamics in Nanoscale Bismuth Telluride

“…Together, these observations demonstrate that the nanoscale reactors can both retain the melted nanoplates and protect them from environmental reactions. As a related example, it was recently shown that 50 nm-thick Al 2 O 3 encapsulation layers can enable high-temperature annealing of SnS 2 , which resulted in improved crystallinity without material loss or oxidation . The nanoscale reactor design in this study can be used to image such processes at high resolution to gain a mechanistic understanding of transformation processes.…”

“…54 Oxide passivation layers have also been shown to increase the allowable annealing temperature during fabrication of LMC devices, resulting in improved crystallinity and electronic properties. 55 Here, we demonstrate the construction of an in situ TEM heating setup featuring an amorphous Al 2 O 3 encapsulation layer that enables investigation of melting, crystallization, and alloying transformations in nanoscale Bi 2 Te 3 platelets without significant material loss or electron beam damage. Melting was observed to progress through the movement of a sharp interface through the Bi 2 Te 3 crystals.…”

“…As a related example, it was recently shown that 50 nm-thick Al 2 O 3 encapsulation layers can enable hightemperature annealing of SnS 2 , which resulted in improved crystallinity without material loss or oxidation. 55 The nanoscale reactor design in this study can be used to image such processes at high resolution to gain a mechanistic understanding of transformation processes. Using these encapsulation layers, we performed in situ TEM heating experiments to investigate the melting and crystallization process of pure Bi 2 Te 3 nanoplates.…”

“…Particularly for TMCs, the use of graphene encapsulation is beneficial to limit beam-induced radiolysis during in situ TEM experiments . Oxide passivation layers have also been shown to increase the allowable annealing temperature during fabrication of LMC devices, resulting in improved crystallinity and electronic properties …”