TIME-RESOLVED OBSERVATION IN TRANSMISSION ELECTRON-MICROSCOPY BY MEANS OF SPATIALLY-RESOLVED ELECTRON CORRELATION SPECTROSCOPY

Time-resolved electron microscopy incorporation electron counting and electron correlation spectroscopy can be used to quantify the dynamics in materials faster than the shot noise limit. An imaging electron be am current, temporally modulated by the dynamics of the specimen, is s elected by the aperture in the image plane and measured by means of an electron counting technique. Silicon avalanche photodiodes are ideal for detecting electrons because of their fast response (rise time <200 ps) and small dead time (<500 ps). A flipped digital correlator with 128 delay channels working at a clock frequency of 30 MHz is developed and successfully used for measuring the autocorrelation function of t he time-dependent image beam current (electron correlation spectroscop y). Applications of this method to the study of the dynamics of superc onducting vortices and to the observation of nanovibrations of materia ls associated with elastic properties are discussed.