A new type of RHEED apparatus equipped with an energy filter

A new type of RHEED apparatus is constructed. A retarding-type energy filter with three spherical grids is inserted between the specimen and the fluorescent screen. For the first time this apparatus can exclude inelastically scattered electrons from the whole RHEED pattern. The performance of the apparatus is demonstrated using aSi(001)2 × 1 surface andSi(111)7 × 7 surface. With the energy filter, the line pattern due to disordering of the2 × 4 structure can be extracted from the background of theSi(001)2 × 1 RHEED pattern. Kikuchi lines almost completely disappear at an energy loss of about 10 eV. Another advantage of the apparatus is that the energy loss spectra of the diffraction spots and energy filtered rocking-curves can be measured with an energy resolution of ∼ 3 eV. The excitation probability for surface plasmons becomes larger at smaller incident glancing angles. It is found that the peak at smaller angles in the rocking-curve contains more inelastic scattering than at larger angles.