New Ultra-High-Resolution TEM Cameras

Abstract

TEM image acquisition is subject to limitations in resolution imposed by the physics of the position-sensitive detection process. in existing on-line digital cameras detection consists of scintillation, image transfer and photon detection by a CCD. Scintillator resolution is governed primarily by the incident beam energy. Material parameters affect the resolution only weakly. Some improvement can be made with a thin transmission scintillator. Still, backscatter of electrons from below can form a noisy background. Optical transfer resolution also has an important effect on overall camera system resolution. Leakage of light within scintillator, between fibers, at interfaces, and the inherent resolution loss due to binning into a finite pixel all contribute to optical resolution loss. This point spread function is narrower than the electron point spread function above 100kV but has an affect at all voltages. Long-range light leakage (psf tail) affects the background noise in diffraction work where there is often a 10e6 ratio between central peak and diffraction spot of interest. Thus, the number of resolved pixels in a TEM image detector is limited by the area of the detector, the effective thickness of the scintillator and the quality of the image transfer.

Gatan has developed several improvements which will address both electron and lightoptical resolution loss.