HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPE OBSERVATION OF STACKING-FAULTS OF MOLYBDENUM-DISULFIDE IN RELATION TO LUBRICATION

An image profile of the layer structure of MoS2 was examined by transmission electron microscopy (TEM). An extra half-plane observed in the S-Mo-S layer lattice image from an ultramicrotomed section of this crystal suggested the appearance of a stacking fault due to a Shockley partial dislocation. The corresponding electron diffraction pattern showed a slight tilt of the normal to the layers against the direction of sliding, resulting in a low coefficient of the intergranular friction of MoS2 of about 0.035. A high resolution TEM observation of the above section with a well-determined crystallographic orientation revealed a zigzag structure of the trigonal prism configuration of molybdenum and sulphur atoms, and a new kind of stacking fault has been found with the aid of a computer simulation of projected images, leading to a proposal for the mechanism of the formation of stacking faults due to Shockley partials on an atomic level.