Device for separation of sputtered neutrals and high energy ions from sputtered low energy ions

摘要

A device capable of reducing the background in ion probe mass spectrometry by up to seven orders of magnitude (107) allows separation of sputtered neutrals and high energy sputtered or backscattered ions from low energy sputtered ions. The low energy sputtered ions are fed into a mass analyzer for determination of the mass-to-charge ratio whereas the neutrals and high energy ions which usually produce a high background intensity in the mass spectra are prevented from entering the mass analyzer. This is achieved by positioning the target off-axis with respect to the relevant analyzer axis on the entrance side of the mass analyzer, by placing a shutter with an aperture between target and entrance aperture of the mass analyzer so that sputtered neutrals passing through the shutter aperture impinge on the front panel of the mass analyzer outside the entrance aperture, by producing an electric field between shutter and front panel of the mass analyzer, and by adjusting the direction and strength of the electric field in such a way that low energy sputtered ions passing through the shutter aperture can be deflected into the entrance aperture of the mass analyzer whereas high energy ions are less deflected and thus impinge on the front panel of the mass analyzer outside the entrance aperture.