The influence of surface topography on the x‐ray intensity in electron microprobe analysis (EDS/WDS)

Copper surfaces were ground or polished to various surface roughnesses and analysed by WDS and EDS. Both K and L photons were analysed at the accelerating voltages 5, 15 and 45 kV. The influence of topography on the K‐peak intensity was negligible, while the L‐peak intensity was rather sensitive to the surface roughness. For low and medium accelerating voltages the L‐peak intensity was lower from a rough than from a smooth surface because of shadowing effects. For high accelerating voltages it was instead enhanced by the surface roughness because of an edge effect which outweighs the shadowing. If small areas are analysed (as always in WDS‐analyses) the variation of the local orientation will cause some scattering in the measured intensities of low energy photons. High energy photons are less affected by the surface roughness. Because of the larger escape length in the material these photons can reach also the detector from areas which are shadowed. Generally, if the surface roughness cannot be avoided, high energy photons should be preferred for the analysis or the peak to background ratio method should be used. The accelerating voltage should in all cases be kept as low as possible in order to minimise the influence of surface roughness.