High Purity Germanium Detectors for EDS

Abstract

High purity germanium (HPGe) detectors offer multiple advantages for x-ray microanalysis in electron microscopes. These advantages include improved detection efficiency at energies above 20 keV, lower noise and higher energy resolution than can be obtained with a lithium drifted silicon detector. In the past, the use of HPGe detectors for EDS at energies below about 2 keV was impossible due to severe distortions of peak shapes and shifts in peak positions. These effects are the result of incomplete charge collection and are most pronounced at energies just above the energy of the germanium L absorption edges (1.2 to 1.4 keV). Using new processing techniques, we have manufactured 30 mm2 HPGe detectors that do not exhibit significant spectral distortion due to incomplete charge collection. Figure 1 presents a comparison of the peak shapes obtained from an HPGe detector produced by a previous method and a new detector produced with our current process. These detectors have been used for EDS applications in (S)TEM and SEM.