Spatial high resolution energy dispersive X-ray spectroscopy on thin lamellas

For conventional samples and measurement geometries the spatial resolution of energy dispersive X-ray spectroscopy is limited by a tear drop shaped emission volume to about 1μm. This restriction can be substantially improved using thin samples and high acceleration voltage. In this contribution the spatial resolution of energy dispersive X-ray spectroscopy in a scanning electron microscope using thin lamella samples is investigated. At an acceleration voltage of 30 kV, an edge resolution down to Δdedge=40±10nm is observed performing linescans across an interface, using an 80 nm thin sample prepared from a GaAs/AlAs-heterostructure. Furthermore, Monte-Carlo simulations of pure elements ranging from sodium to mercury are performed for different sample thicknesses. From the simulations we can derive a simple empirical formula to predict the spatial resolution as a function of sample thickness.

► An edge resolution of Δd=40±10nm is observed using an 80 nm thin GaAs/AlAs-heterostructure sample.
► An empirical formula to predict the spatial resolution is derived from Monte-Carlo simulations.
► The experimental resolution is within a factor of 2 close to the physical limit predicted by simulation.