Estudio de la colección incompleta de cargas en un detector de Si(Li

VISÑOVEZKY C.; LIMANDRI S.; CANAFOGLIA ME; BONETTO RD; TRINCAVELLI J

AVANCES EN ANALISIS POR TECNICAS DE RAYOS X

Lugar: Chile; Año: 2008 vol. XIV p. 277 - 282

1515-1565

The asymmetry of the characteristic peaks obtained using a detector of Si(Li) is mainly due to incomplete charge collection. Impurities and defects in the crystalline structure of Si can act as "traps" for holes and electrons in their trip toward the detector electrodes. Therefore, the collected charge, and consequently the detected energy, is smaller than the expected one. The global effect is that peaks may present a "tail" toward the low energy side. This phenomenon is more important for low energies (lower than 2.3 keV, in the case of the detector used). In this work, the parameters related to peak asymmetry are studied, allowing a better understanding of the trapping process mentioned above. For this purpose, spectra form pure and compound samples were collected for elements with atomic number between 7 and 17. In order to describe the shape of the characteristic K peaks as a function of its energy, an asymmetric correction to a Gaussian function is proposed. Spectra were obtained by Electron Probe Microanalysis (EPMA) for incidence energies between 5 and 25 keV using an energy dispersive spectrometer equipped with a Si(Li) detector protected by an ultrathin window.