Microanalysis results with low Z gas inside environmental SEM

► The electron beam skirt phenomenon in ESEM under gas environment is studied. ► The use of gas with high atomic number induces some uncertainties in the microanalysis results. ► The use of a gas with low atomic number such as Helium, leads to accurate results. ► A new explanation related to the gas ionization is given. ► Equation given rs is not suitable.