WAVE OPTICAL TREATMENT OF SURFACE STEP CONTRAST IN LOW-ENERGY ELECTRON MICROSCOPY

A wave optical treatment of surface step contrast in a low-energy electron microscopy (LEEM) is presented. The aberrations of an idealised LEEM imaging system are directly incorporated into a transfer function (TF) and image simulations of surface steps are evaluated in one and two dimensions. Under the special circumstances of a weak phase object, the simplified form of the contrast transfer function (CTF) is used to discuss LEEM image contrast and optimum defocus conditions.