Reflection electron microscopy and interferometry of atomic steps on gold and platinum single crystal surfaces

Two beam interferences produced using an electrostatic biprism, which is inserted in the position of the selected area diaphragm of a commercial electron microscope, may be used in reflection electron microscopy to determine the phase shifts induced by structures on single crystal surfaces. A description of our interferometrical and holographical experiments on the phase shift at steps on (111)Au and (111)Pt single crystal surfaces is given and a straight forward interpretation of the results in terms of refraction will be discussed. As a particular result phase shifts of pi and 0.9 pi were measured for monatomic steps on (111)gold and (111)platinum surfaces, respectively.