Research On In-situ Atmosphere Controllable Transfer System For Transmission Electron Microscope

As a large-scale scientific research instrument with ultra-high resolution and rich characterization methods,Transmission Electron Microscopy（TEM）has been widely used in many disciplines such as materials science,chemistry,physics,and life sciences.The high-resolution microstructure analysis of TEM has increasingly become a common basic key technology in many areas.Especially in recent years,with the development of in-situ experimental technology,scientists can observe the changes in the microstructure of matter under working conditions at the nanometer or even atomic scale,unveiling the veil of the movement of matter in the microscopic world.However,due to the limitations of the equipment,the electron microscope sample under test will inevitably be exposed to the air atmosphere during the process of preparing and transferring to TEM,resulting in oxidation and pollution problems,especially for metals such as lithium and magnesium that are easily oxidized and easily polluted,which will change their microstructures.Therefore,in this paper,we develop an In-situ atmosphere controllable transfer system for TEM,which aims to protect the sample that suffered from oxidation,deliquescence,pollution and other problems during the whole process from preparation to delivery to the electron microscope.The main research contents are as follows:Design and manufacture of In-situ atmosphere controllable transfer system.Facing the existing TEM,we design a new controllable atmosphere In-situ TEM holder to ensure that sample does not come into contact with air and other pollution sources during the transfer process,and to ensure that the internal vacuum degree is better than 10^-2 mbar for more than 1h;build an In-situ atmosphere controllable sample loading system to ensure that the samples are not contaminated during preparation and loading.Establish a finite element model of the sealing structure and calculate its leakage.The finite element model of the O-ring seal is established,and it is determined that when the contact wire diameter of the local contact seal accounted for about 20%of the O-ring wire diameter,and the installation interference of the rotary seal O-ring is about 9%,the tightness of controllable atmosphere In-situ TEM holder can meet the requirements of the sealing design.At the same time,based on the average flow model of the compressible gas,the leakage time of the in-situ sample stage of the controllable atmosphere is calculated to be 68.4 min,and the actual sealing time is about 71 min through the establishment of an air tightness detection device,which verifies the validity of the finite element model.Research on imaging stability of TEM based on charge effect.A new TEM sandwich like sample structure is designed to change the resistance of the tip of TEM holder to low resistance,medium resistance and high resistance respectively,which verify the aberration stability and image drift of the TEM imaging instability and analyze its internal dynamic mechanism.The results show that the increase of resistance value will cause periodic charging and discharging in TEM sample,leading to a periodic change in the imaging stability of electron microscope.Lithium protective observation experiments.Using the In-situ atmosphere controllable transfer system designed in this paper to carry out the metal lithium microscopic observation experiment,the high-resolution images and diffraction patterns of the metal lithium were taken,which proved the practicability of the system.