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Abstract

Ion surface scattering (ISS) is a powerful diagnostic tool to measure the composition and morphology of surfaces. This method is strictly surface sensitive since backscattered ions are analyzed which can only originate from collision processes with the topmost atoms of a solid. Either noble gas or alkali ions are used as probing beams with typical energies in the range of a few keV. This paper discusses the feasibility of this diagnostic to probe a film surface exposed to a low temperature plasma. Two major difficulties arise from the combination of ISS with the presence of a glow discharge. First, ISS is usually performed at least under high vacuum conditions. Therefore, the generation of the primary ions as well as the detection of backscattered ions has to be separated from the plasma chamber by differential pumping. Second, the trajectories of the ions during the scattering process are bent within the sheath region in front of the solid in the glow discharge. This bending of the ion trajectories can be put to an advantage since it serves also as a simple energy filter for the backscattered ions. On the other hand, if the kinematic of the scattering process is known the measurement of the energy and trajectory of the scattered ions provides information about the potential distribution in the plasma sheath.