Development of tomography–transmission electron microscope (TEM) specimen holder stable under acoustic disturbances

Abstract

This paper focuses on the development of tomography—transmission electron microscope (TEM) specimen holder stable under environment effect that allows atomic resolution. The successful holder must be dynamically stable for accuracy and image processes to obtain an atomic resolution, with a minimum controllable drift of the sample position. Different strategies to reduce the effect of acoustic disturbances are investigated. The approach to the problem has been two-fold, numerical and experimental. The effect of mechanical and acoustic noise is analyzed. Finite element results match very well previous experimental results and observations. Theoretical analysis showed that air pressure fluctuations have a significant impact on microscopes with side entry goniometers, especially when the exciting frequency matches a vibration mode of the sample holder. For example, finite element analysis (FEA) predicts that the tip deflections are 4.5 Å and 0.09 Å under air pressure excitation of 64 and 40 dB respectively. Utilizing a sandwiched constrained damping shell layer made of viscoelastic material that partially covers the inner part of TEM holder body successfully decreased the vibration. Finite element simulations predict that a shell layer of viscoelastic material with a thickness equal to the 1/10 of the body holder diameter reduces the vibrations by 30%. The viscoelastic layer shell thickness, loss factor, and elastic modulus have a strong effect on the damping behavior and the optimal combination should be determined.