ABSTRACT
In studies of the atomic structure of surfaces and surface phase transitions currently the most widely used method is the slow electron diffraction (SED) method. Its high sensitivity to the atomic structure of surfaces is due WR WKHIDFW WKDWDWDQHOHFWURQHQHUJ\RIDERXW·H9 WKHLUPHDQIUHH path is 0.5 ÷ 1 nm. The low-voltage electronograph used in this method is so constructed (Fig. 2.1) that due to the delaying potential difference applied between the shield and filter grids, only the electrons which have undergone elastic scattering in the opposite direction from the crystal surface (about 1% of full output) are separated. The screen is attached to a large positive potential that defines the acceleration of electrons and determines the excitation energy or luminophor of the screen upon impact. Photo or video cameras are used record the resulting diffraction reflexes. Due to the selection of electrons which have undergone elastic scattering on atoms of the surface and near-surface ionic planes, the diffraction pattern displayed on the screen, is formed only by a few atomic planes closest to the surface. The basics of the SED method were discussed in detail in several monographs and reviews [169, 170, 349, 430]. Here we will focus on its most important of features and characteristics.
