Low energy electron microscopy

A transmission-type low energy electron microscopy, comprising:

• a vacuum chamber;
• an electron gun located in the vacuum chamber and configured to emit an electron beam;
• a diffraction chamber in communication with the vacuum chamber;
• an imaging device located in the diffraction chamber;
• a core column connected to the diffraction chamber;
• a vacuum pumping device connected to the vacuum chamber;
• a sample holder configured to fix a two-dimensional nanomaterial sample so that the electron beam passes through the two-dimensional nanomaterial sample and enters the diffraction chamber to form a diffraction electron beam and a transmission electron beam to form an image on the imaging device;
• and
• a control computer, wherein the control computer comprises a switching module configured to switch the transmission-type low energy electron microscopy between a large beam spot diffraction imaging mode and a small beam spot diffraction imaging mode;
• in the large beam spot diffraction imaging mode, the electron beam is larger than the two-dimensional nanomaterial sample and used to irradiate entire surface of the two-dimensional nanomaterial sample so that a first diffraction imaging of the entire two-dimensional nanomaterial sample is obtained;
• and in the small beam spot diffraction imaging mode, the electron beam is smaller than the two-dimensional nanomaterial sample and used to irradiate partial surface or scan entire surface of the two-dimensional nanomaterial sample so that a second diffraction imaging, of part of the two-dimensional nanomaterial sample, is obtained.