In situ transmission electron microscope study of reliability in molybdenum disulfide based strain sensors

Reliability of flexible device under external strain is an important issue. The clarification of complex evolution of structure under external strain is critical for basic physical understanding and reliability improvement. However, lack of the direction of the evolution process and the construction of the relationship between structure and electrical properties, the failure mechanism of flexible device remains controversial. Here, in situ transmission electron microscope (TEM) is used to directly observe the structural evolution during stretching and compression process in MoS2 based strain sensor. Through the analysis of the relationship between electrical properties and structure, the interfacial structure related gradual and abrupt resistance changes are observed. The formation of twisted and defected MoS2 layers during stretching process is important. The formed twisted MoS2 layers changes the current path, the resistance changes continuously. Then, the MoS2 is mechanically peeled off into two separate individuals, and the twisted MoS2 at the interface is removed in situ. By controlling the distance between two separate MoS2, the current has a sudden change. The in situ electrical TEM experiment clarified the relationship between the current (resistance) and the interface structure. It provides the experimental basis for the understanding of complex evolution mechanism under external strain, which is important for reliability of flexible device.