From thickness dependent exit waves to projected potential: Thickness derivative approach

In HREM, due to multiple scattering, the exit wave of the object is nonlinear thickness dependent so that there is no one-to-one relation between object structure and the exit wave. This feature hampers the direct retrieval of structural information from exit waves. In this paper we discuss the possibility to restore the object structure in a direct way using exit waves of different thicknesses. It is theoretically shown that the amplitude of the thickness derivative exit wave vertical bar partial derivative psi/partial derivative z vertical bar may directly reflect the project potential in a simple way. Image simulations show that it can be applied to restore the projected potential