Digital enhancement of the surface contrast in a conventional HREM image

Three numerical methods for enhancing surface contrast in a conventional HREM image are discussed. The first two are simulations of the special experimental techniques for surface plan-view imaging, i.e., aperture-restricted HREM and off-zone HREM. The third one, which increases the surface diffraction, is unrealizable in experiment. The last method is shown to be more effective for revealing the relationship between the surface and the bulk. Moreover, this method can be made highly objective by exploiting the fact that the period of the surface structure is generally larger than that of the bulk.