Concentric hemispherical analyser

The energy of the photoelectrons leaving the sample are determined using a Concentric Hemispherical Analyser (CHA), and this gives a spectrum with a series of peaks whose energy values are characteristic of each element. A schematic diagram of a CHA is shown in Figure 2.3. 

The hemispherical analyser shown in Figure 8.5(d) works on a similar principle buf has fhe advanfage of collecting more phofoelecfrons. An analyser consisting of two concentric plates which are parts of hemispheres, so-called spherical sector plates, is often used in a spectiomefer which operafes for bofh UPS and XPS. 

Figure 2.3. Schematic diagram of a concentric hemispherical electron energy analyser.

Figure 12.29 Diagram of a Concentric Hemispherical Analyzer (CHA) for XPS with a standard input lens system, which transfers an image of the analysed area on the sample onto the entrance slit to the analyzer, with slight magnification to permit removing the sample from close proximity to the entrance slit of the analyzer permitting greater working space around the sample. Source Reprinted with permission from Coxon P, Krizek J, Humpherson M, Warden IRM, Relat Phenomena, 52, 821, 1990. Copyright 1990, Elsevier.

XPS analyses were performed using a PHI 5700 spectrophotometer equipped with a concentric hemispherical analyzer in the standard configuration (Physical Electronics, Eden Prairie, MN, USA). The vacuum system consists of a turbo-molecular pump, ion pump, and a titanium sublimation pump. The base pressure before the analysis was better than 10 Pa. The X-ray source was A1K0 (1486.6 eV), run at 300 watts. The incident angle was 54.7° and the emission angle was 45° with respect to the sample surface normal. All the spectra were obtained in digital mode. A constant energy of 23.50 eV was set across the hemispheres of the electron analyzer operated in the Fixed Analyzer Transmission (FAT) mode for the detailed spectra the survey spectra have been acquired with 187.85 eV pass... 

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