Degradation behaviors and mechanisms of MoS2 crystals relevant to bioabsorbable electronics

Xiang Chen,Hyunmin Kim,Jong-Hyun Ahn,Sachin M Shinde,Zonghoon Lee,Suk Woo Lee,Krishna P Dhakal

doi:10.1038/s41427-018-0078-6

Abstract

Monolayer molybdenum disulfide (MoS2) exhibits unique semiconducting and bioresorption properties, giving this material enormous potential for electronic/biomedical applications, such as bioabsorbable electronics. In this regard, understanding the degradation performance of monolayer MoS2 in biofluids allows modulation of the properties and lifetime of related bioabsorbable devices and systems. Herein, the degradation behaviors and mechanisms of monolayer MoS2 crystals with different misorientation angles are explored. High-angle grain boundaries (HAGBs) biodegrade faster than low-angle grain boundaries (LAGBs), exhibiting degraded edges with wedge and zigzag shapes, respectively. Triangular pits that formed in the degraded grains have orientations opposite to those of the parent crystals, and these pits grow into larger pits laterally. These behaviors indicate that the degradation is induced and propagated based on intrinsic defects, such as grain boundaries and point defects, because of their high chemical reactivity due to lattice breakage and the formation of dangling bonds. High densities of dislocations and point defects lead to high chemical reactivity and faster degradation. The structural cause of MoS2 degradation is studied, and a feasible approach to study changes in the properties and lifetime of MoS2 by controlling the defect type and density is presented. The results can thus be used to promote the widespread use of two-dimensional materials in bioabsorption applications.

Highlights

Molybdenum disulfide (MoS2), a key member of the class of materials known as layered transition metal dichalcogenides (TMDCs), has attracted tremendous interest from the scientific community over the past few years because of its applications in various areas, including electronics, optoelectronics, and physicochemical and biomedical sensors[1,2,3,4,5,6,7]
The results show that high-angle grain boundaries (HAGBs, >15°) preferentially degraded faster than low-angle grain boundaries (LAGBs,
The degradation process of MoS2 crystals is evidenced to be induced by intrinsic defects in the as-grown crystals, including GBs and point defects, because of the greater density of dangling bonds and higher reactivity in these regions

Summary

Introduction

Molybdenum disulfide (MoS2), a key member of the class of materials known as layered transition metal dichalcogenides (TMDCs), has attracted tremendous interest from the scientific community over the past few years because of its applications in various areas, including electronics, optoelectronics, and physicochemical and biomedical sensors[1,2,3,4,5,6,7]. Monolayer MoS2 can be slowly oxidized in air or dissolved in aqueous solution after several weeks or months, resulting in its environmental degradation[12,13,14,15]. Owing to these characteristics, monolayer MoS2 is an ideal candidate for use in bioabsorbable electronics, such as temporary biomedical sensors and therapeutic vehicles, that can be absorbed after being implanted into the human body, thereby eliminating the need for secondary surgeries to extract the implants[16,17,18,19].

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Results

Conclusion