Compton Scattering Artifacts in Electron Excited X-Ray Spectra Measured with a Silicon Drift Detector

Abstract

Artifacts are the nemesis of trace element analysis in electron-excited energy dispersive X-ray spectrometry. Peaks that result from nonideal behavior in the detector or sample can fool even an experienced microanalyst into believing that they have trace amounts of an element that is not present. Many artifacts, such as the Si escape peak, absorption edges, and coincidence peaks, can be traced to the detector. Others, such as secondary fluorescence peaks and scatter peaks, can be traced to the sample. We have identified a new sample-dependent artifact that we attribute to Compton scattering of energetic X-rays generated in a small feature and subsequently scattered from a low atomic number matrix. It seems likely that this artifact has not previously been reported because it only occurs under specific conditions and represents a relatively small signal. However, with the advent of silicon drift detectors and their utility for trace element analysis, we anticipate that more people will observe it and possibly misidentify it. Though small, the artifact is not inconsequential. Under some conditions, it is possible to mistakenly identify the Compton scatter artifact as approximately 1% of an element that is not present.

Efficient Simulation of Secondary Fluorescence Via NIST DTSA-II Monte Carlo

“…As Compton scattering is not an important phenomenon in most electron excited X-ray spectra, the model used in DTSA-II is fairly simplistic. Compton scattering can be observed (Ritchie et al, 2011) when small samples emitting higher energy (>10 keV) photons rest on low Z bulk substrates (like a particle on a carbon substrate). Compton scattering can also be observed in X-ray fluorescence spectra when the incident excitation X-rays scatter from the sample into the detector.…”

Gaining Improved Chemical Composition by Exploitation of Compton-to-Rayleigh Intensity Ratio in XRF Analysis

“…At present it is possible, similar to the common XRF or SEM/EDX spectra, to simulate XRF spectra with reliable scattering contributions , and evaluate before or even without the experiment, the chances of gaining more analytical information for any given individual experimental conditions. It was also recently reported that Compton scattering “artefacts”, easily misinterpreted as X-ray fluorescence peaks of trace elements, could be explained by such valuable simulations …”

“…It was also recently reported that Compton scattering "artefacts", easily misinterpreted as X-ray fluorescence peaks of trace elements, could be explained by such valuable simulations. 23 ■ THEORETICAL BASIS OF X-RAY SCATTERING By irradiation of matter with an X-ray beam the following three types of interactions may occur: 24 (i) photoelectric absorption, (ii) elastic (or coherent, or Rayleigh) scattering, and (iii) inelastic (or incoherent, or Compton) scattering. The mass attenuation coefficient (MAC), which describes the attenuation degree of the X-rays in matter, is determined by all these three types of interactions.…”