Atomic displacements in the modulated structure of Bi2Sr2(Ca1-xPrx)Cu2O8+delta and their effect on HRTEM reverse contrast image

The amplitude of transverse atomic displacement wave along the direction of incident. electron beam exerts a significant effect on the brightness of s pots in a high-resolution transmission electron microscope (HRTEM) reverse contrast image. The bright spot is associated with the projection of the mo dulated atomic chain along the beam direction. In general, the spot brightn ess is roughly inversely proportional to the amplitude of the displacement wave in an appropriate region of defocus, specimen thickness and amplitude. Monotonic decrease in the spot brightness with increasing amplitude can be attributed to the decrease in the degree of interference between scattered electrons. A complicated domain configuration has been found by the analys is of the spot brightness modulation observed in a [0 0 1] HRTEM reverse co ntrast image.