Off-axis electron holography: Materials analysis at atomic resolution

Abstract

In high-resolution off-axis electron holography, the correction of coherent aberrations allows the quantitative interpretation of the amplitude and phase of the object wave up to the information limit of the electron microscope. Since the measured object phase is directly related to the projected atomic potential for sufficiently thin samples, off-axis electron holography is expected to allow distinguishing of different elements in the reconstructed phase image (“holographic materials analysis”). This has already been verified with the example of Ga and As. However, simulations of the atomic phase shift reveal that the interpretation of the measured phase shift in terms of atomic species is generally rather complex. The findings suggest that, in some cases, the requirements as to lateral resolution and phase detection limit will be met only by electron microscopes of the next generation.