Long‐Term Stability Control of CVD‐Grown Monolayer MoS2

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2019-07, Vol.13 (7), p.n/a
• Main Authors: Şar, Hüseyin, Özden, Ayberk, Demiroğlu, İlker, Sevik, Cem, Perkgoz, Nihan K., Ay, Feridun
• Format: Article
• Language: English
• Subjects: aging; chemical vapor deposition, cracks; Configurations; Control stability; Cracking (fracturing); Defects; Electronics; First principles; Flakes (defects); fracture; Fracture mechanics; long‐term stability; Molybdenum disulfide; monolayer MoS2; Monolayers; Oxidation resistance; Structural stability; Tensile stress; Time dependence; Transition metal compounds; transition metal dichalcogenides; Vacancies
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201800687

The structural stability of 2D transition metal dichalcogenide (TMD) formations is of particular importance for their reliable device performance in nano‐electronics and opto‐electronics. Recent observations show that the CVD‐grown TMD monolayers are likely to encounter stability problems such as cracking or fracturing when they are kept under ambient conditions. Here, two different growth configurations are investigated and a favorable growth geometry is proposed, which also sheds light onto the growth mechanism and provides a solution for the stability and fracture formation issues for TMDs specifically for MoS2 monolayers. It is shown that 18 months naturally and thermally aged MoS2 monolayer flakes grown using specifically developed conditions, retain their stability. To understand the mechanism of the structural deterioration, two possible effective mechanisms, S vacancy defects and growth‐induced tensile stress, are assessed by the first principle calculations where the role of S vacancy defects in obtaining oxidation resistant MoS2 monolayer flakes is revealed to be rather more critical. Hence, these simulations, time‐dependent observations and thermal aging experiments show that durability and stability of 2D MoS2 flakes can be controlled by CVD growth configuration. The proposed growth geometry provides a solution for the stability–fracture issue for CVD‐grown transition metal dichalcogenides. A clear difference is unveiled regarding the mechanical stability of the flakes grown by horizontal (HO, proposed by the authors) and face down (FD, commonly used) growth approaches, where the FD‐grown flakes spontaneously crack but HO flakes remain unchanged and keep their as‐grown structures for the duration of their observation, exceeding 18 months.