PNNL

Abstract

An automated single particle SEM/EDX analysis of aerosols deposited onto grid supported carbon film of 15-25 nm thickness is demonstrated. Use of the carbon film gives exceptionally low background in the SEM/EDAX and allows satisfied automated analysis of particles down to 0.1 mm size, including analysis of low-Z elements (C, O and N). In this work, six lab-generated 0.1-2 mm aerosols were tested for their elemental composition. The EDAX yields reasonably accurate quantitative results featuring all the elements presented in the tested compounds, namely C, O, N, Na, S, Al, Si and Cl. Furthermore, the carbon film has very low backscattered electron (BSE) yield compared to that from the particle, so in the BSE mode the particle image is seen with very high contrast. This greatly improves quality and speed of the automated mapping of particles by SEM prior to EDAX. The presented approach is believed to be a significant improvement over the automated single particle analysis in the electron microprobe based techniques, which usually provide limited information on low-Z elements and usually could not go below ~0.5 mm.