Optimal accelerating voltage for HRTEM imaging of zeolite.

The electron irradiation damage of MFI-type zeolite was estimated under various accelerating voltages of 100, 200 and 300 kV from successively captured high-resolution transmission electron microscopy (HRTEM) images. To determine the optimal accelerating voltage for HRTEM imaging of electron-sensitive MFI zeolite, the critical dose was estimated from the disappearance of a specific fast Fourier transform spot calculated from experimental images. Based only on the electron dose, a higher voltage was more advantageous. However, taking into account the minimum dose for imaging with a CCD camera, the optimal accelerating voltage for imaging MFI zeolite was 200 kV. The minimum dose for image detection with a CCD camera was surmised from the output/input signal ratio dependence on the accelerating voltage and the contrast range in simulated HRTEM images.