ROLE OF THE ELECTRON FORWARD-FOCUSING EFFECT IN THE FORMATION OF KIKUCHI PATTERNS OF SINGLE-CRYSTAL SILICON

Kikuchi patterns produced by quasi-elastic backscattering of electrons with energies of 0.6-2 keV from a thin Si(111)7 x 7 near-surface laye r are studied, It is shown that experimental data obtained for silicon , just like those for metals, can be described satisfactorily by calcu lations made in single-scattering cluster approximation, as well as in terms of a model taking phenomenologically into account the forward-f ocusing of backscattered electrons as they escape from the crystal. It has thus been demonstrated that the forward-focusing effect at an ene rgy E=2 keV plays a dominant role in the formation of Kikuchi patterns , which permits their use for visualization of the atomic structure of a surface. The dependences of the focusing efficiency on the paramete rs of the atomic chains along which electrons propagate have been esta blished for the closest-packed crystal directions. (C) 1997 American I nstitute of Physics.