Study On The Contrast Of Transmission Electron Microscopy Image For Microstruction

Transmission Electron Microscopy (TEM) has become one of the most powerful tools for microstructural study. Diffraction image recorded the reciprocal space information of sample can be used to reveal the crystalline phase, symmetry and orientation, and microscope images recorded the real space information of sample can be used to reveal the microstructure and spatial distribution. According to the formation mechanism of microscopy image, the contrast of image includes amplitude contrast and phase contrast, and amplitude contrast can be divided into mass-thickness contrast and diffraction contrast. Diffraction contrast reflects the internal organization of crystal, and it is sensitive to the crystal defect, crystal orientation. Mass-thickness contrast reflects the morphology features of the sample, which is caused by the different thickness or average atomic number of sample. When the electron wave passes through the very thin sample, its amplitude remain unchanged almost, but the phase of electron beam is modulated by periodic potential field of crystals, therefore form the phase contrast, that is the high-resolution TEM (HRTEM). Under certain conditions, the phase contrast can be use to explain the crystallographic structure. In this article, we introduce the contrast formation mechanism of transmission electron microscopy and characteristics of different contrast; We present the principles and techniques for the transformation between mass-thickness contrast and diffraction contrast; We study the structures of rare earth nanomaterials by HRTEM. More information about the microstructures in the same position can be revealed by combining the TEM images with the different contrasts.