An electron-permeable membrane for use in a charge-particle spectroscopy device

A device 1 for spectroscopy using charged analytes, particularly ion mobility spectrometry, has an electron generator 2 which sends electrons through an electron permeable window 6 into an ionization chamber 8. The thermal strain on the membrane 6 is lowered significantly if it is formed from a material which contains polysilicon, or at least one component from the group consisting of oxides and nitrides of boron, aluminium, carbon, silicon and titanium, as well as carbides of boron, aluminium, silicon and titanium. The membrane may be a multilayered membrane and have a thickness between 50 and 500 nm.