Automated single particle SEM/EDX analysis of submicrometer particles downto 0.1 mu m

Typically single-particle SEM/EDX analysis of aerosols is done on polycarbo nate filters or solid carbon substrates, This has led to a widespread concl usion that EDX provides poor information on carbon, oxygen, and nitrogen co ntent of a particle and usually could not go below 0.5-mum particles. We sh ow that use of grid-supported carbon films of 15-25-nm thickness gives exce ptionally low background in the SEM/EDX analysis and allows satisfied autom ated analysis of particles down to 0.1-mum size, including detection of low -Z elements. In this work, six laboratory-generated 0.1-2-mum aerosols were tested for their elemental composition. The EDX analysis yields reasonably accurate quantitative results featuring all the elements present in the te sted compounds, namely, C, O, N, Na, S, Al, Si, and Cl, Furthermore, the ca rbon 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 celer y high contrast, This greatly improves quality and speed of the automated m apping of particles by SEM prior to EDX analysis.