I2-5 Detector Characterization and Optimization of Detection Limits in EELS Studied on Natural Ruby

Electron energy-loss spectroscopy (EELS) is an efficient microanalytical technique for gaining chemical and structural information of thin samples with high trace element sensitivity. Although in principle possible, detecting single atoms [1], is not trivial. Estimating elemental detection limits or the minimum number of detectable atoms accurately requires a.) reliable signal extraction schemes, as the signal is often superimposed on a large background or overlaps with another edge, b.) a good estimation of the statistical uncertainty associated with background removal c.) accurately known ionization cross-sections and d.) a good understanding of the noise introduced by the spectrometer´s detector. In this paper systematic studies have been performed to evaluate the best possible way for signal extraction and optimizing the signal-to-noise ratio. Natural ruby was chosen as a complex sample, featuring overlapping edges, containing 0.4at % Cr (L23 edge at 575eV) on top of the alumina background (background plus O-K edge at 532eV)