In-situ TEM investigation of MoS2 wrinkles and its effects on electrical properties

Abstract

MoS2 has potential application in the fields of electronics and optics. However, thin films with non-uniform or local compressive strain can form winkles. The presence of wrinkles has great effects on the performance of the transition metal dichalcogenides (TMDs) materials. In this work, by in-situ transmission electron microscopy (TEM), we tracked the formation and disappearance of MoS2 wrinkles to reveal the microstructure of wrinkles and its effects on electrical properties. It is found that compressive stress can lead to the formation of wrinkles, and the wrinkles disappeared with removal of the stress. The εxx maps show that MoS2 nanosheets corrugated as the strain reached 3.3% for 15 layers, accompanied by new diffraction points in fast Fourier transform (FFT) image. In contrast, removal of the stress resulted in the disappearance of wrinkles and new diffraction points, and MoS2 nanosheets restored to its initial morphology. Moreover, wrinkles also affect the electrical properties of MoS2 nanosheets. The existence of wrinkles caused an increase of the current, and the disappearance of the wrinkles accompanied by the current decreased, which is due to the piezoresistive effect. This study is helpful to understand the properties of MoS2 nanostructures and is of great significance to the structural design in the electronic field.