Standard 120° Four Grid LEED Optics Pckg.
981-0127 Four Grid LEED Optic
981-2145 Electron Gun Power Module
981-2125 Off-Axis Electron Gun
981-2148 LEED Control Module
Cable Kit, Manual
USD 13 880
The LEED/Auger electron optics is a multi-purpose assembly. In LEED analysis, the unit displays the diffraction patterns resulting from the interaction of low energy electrons with the ordered surface structure of samples under study. These diffraction patterns can be directly observed and photographed.
In Auger analysis, retarding field techniques are used to measure the secondary electron energy distributions, producing Auger spectra that identify the elemental composition of sample surfaces. This technique for producing Auger spectra has two built-in advantages: it is a low cost method because it utilizes the same analyzer that is used for LEED studies; and the additional components required for Retarding Field Auger work are usable without modification if one wishes to convert to Cylindrical Mirror Analyzer Auger techniques.
The electron optics assembly consists of a concentric fluorescent screen and four-grid assembly. The screen is a P11 phosphor-coated spherical surface which yields a sharp, blue diffraction image. Four concentric spherical grids made from nickel plated tungsten mesh form the grid assembly. The nickel plated grid are hydrogen-fired to give the structure the high degree of mechanical stability needed to give both high resolution and longterm, consistent data.
The grid nearest the specimen is normally held at specimen potential to create a field-free region between specimen and grid. The two center grids form a suppressor that gives excellent cut-off characteristics for LEED work, and permits the examination of the energy distribution of scattered electrons for Auger analysis. The fourth grid shields the screen from the modulation applied to the suppressor grids during Retarding Field Auger (RFA) analysis.
In Auger analysis, the potential on the suppressor grids is slowly swept across the energy range of interest. By modulating the sweep voltage and measuring the second harmonic component of the current to the collector screen, the energy distribution is differentiated, emphasizing the Auger peaks.