New pathways for improved quantification of energy-dispersive X-ray spectra of semiconductors with multiple X-ray lines from thin foils investigated in transmission electron microscopy

摘要

Theoretical approaches to quantify the chemical composition of bulk and thin-layer specimens using energy-dispersive Xray spectroscopy in a transmission electron microscope are compared to experiments investigating (In) GaAs and Si(Ge) semiconductors. Absorption correctors can be improved by varying the take-off angle to determine the depth of features within the foil or the samples thickness, or by definition of effective k-factors that can be obtained from plots of k-factors versus foil thickness or, preferably, versus the K/L intensity ratio for a suitable element. The latter procedure yields plots of self-consistent absorption corrections that can be used to determine the chemical composition, iteratively for SiGe using a set of calibration curves or directly from a single calibration curve for InGaAs, for single X-ray spectra without knowledge of sample thickness, density or mass absorption coefficients.