Watching Dynamic Self-Assembly of Web Buckles in Strained MoS₂ Thin Films

Abstract

Thin films with large compressive residual stress and low interface adhesion can buckle and delaminate from relatively rigid substrates, which is a common failure mode of film/substrate interfaces. Current studies mainly focused on the geometry of various buckling patterns and related physical origins based on a static point of view. However, fundamental understanding of dynamic propagation of buckles, particularly for the complicated web buckles, remains challenging. We adopt strained two-dimensional MoS2 thin films to study the phenomenon of web buckling because their interface adhesion, namely van der Waals interaction, is naturally low. With a delicately site-controlled initiation, web buckles can be triggered and their dynamic propagation is in situ observed facilely. Finite element modeling shows that the formation of web buckles involves the propagation and multilevel branching of telephone-cord blisters. These buckled semiconducting films can be patterned by spatial confinement and potentially used in diffuse-reflective coatings, microfluidic channels, and hydrogen evolution reaction electrodes. Our work not only reveals the hidden mechanisms and kinematics of propagation of web buckles on rigid substrates but also sheds light on the development of semiconducting devices based on buckling engineering.

Understanding and Controlling Hexagonal Patterns of Wrinkles in Neo-Hookean Elastic Bilayer Structures

“…In addition, most reported wrinkling patterns in the experiments are not perfect hexagons and contains pentagons and heptagons, which can be viewed as defects (e.g., disclinations, dislocations, and grain boundaries) if we treat hexagons as perfect crystal lattices. Very recently, hexagonal patterns down to micrometers were also reported in nanoscale strained MoS2 film on a sapphire substrate [Ren et al, 2019].…”

Strain-Modulated Magnetism in MoS2

“…In addition, the researchers have found that the intrinsic tensile strain (0.15–1.37%) was also introduced in CVD grown-monolayer MoS 2 [ 113 , 115 , 117 , 118 , 119 , 122 ]. This intrinsic tensile strain is caused by the mismatch of thermal expansion coefficients [ 72 , 73 , 113 , 115 , 116 , 117 , 121 ]. Interestingly, whether through flexible substrate [ 104 ] or thermal mismatch [ 72 , 73 ], the strain state of MoS 2 materials can be further mediated by creating buckles [ 72 , 73 , 104 , 105 , 114 , 121 , 123 , 124 ].…”

“…This intrinsic tensile strain is caused by the mismatch of thermal expansion coefficients [ 72 , 73 , 113 , 115 , 116 , 117 , 121 ]. Interestingly, whether through flexible substrate [ 104 ] or thermal mismatch [ 72 , 73 ], the strain state of MoS 2 materials can be further mediated by creating buckles [ 72 , 73 , 104 , 105 , 114 , 121 , 123 , 124 ].…”

“…However, most of the previous work mainly focused on theoretical calculations. We have first introduced biaxial strain into the MoS 2 film through spontaneous buckling and found that biaxial strain can enhance its room-temperature FM (RTFM) [ 72 , 73 , 74 ]. As a whole, an extensive and in-depth understanding of strain-mediated magnetism in MoS 2 is needed, which would provide new avenues for spintronics and straintronics.…”

Two‐dimensional materials: From mechanical properties to flexible mechanical sensors

“…The strain effect of 2D materials is also related to the lattice vibration and crystal orientation, resulting in the change of optical properties such as PL and Raman shift . It is well known that the diversification of bandgap and light emission energy is owing to the electronic configuration and energy levels based on the change of atomic structure by applied strain.…”