Surface investigation of solids by the statical method of secondary ion mass spectroscopy (SIMS)

Abstract

Abstract The physical and chemical properties of a solid surface are determined by its uppermost monolayers. Besides other methods like Auger electron spectroscopy (AES) and X-ray electron spectroscopy (ESCA) for example, the chemical composition of these uppermost monolayers can be investigated by the statical method of secondary ion mass spectroscopy (SIMS). In this method a relatively large target area (0.1 cm 2 ) is bombarded with a small primary ion current density (10 −9 A cm −2 ). Thus a sputtering time of several hours is achieved for an individual monolayer. A mass analysis of the emitted positive and negative secondary ions gives information about the chemical composition of the uppermost monomolecular layer of the bombarded surface. Important features of SIMS are: detection of chemical compounds; isotope sensitivity; detection of hydrogen and its compounds ; depth resolution in the range of a single monolayer ; low detection limits ( −6 monolayer or −14 g) for many elements and compounds. The capacity of this method is demonstrated using as examples the initial surface oxidation of metals and semiconductors and adsorption phenomena on clean metal surfaces. In some special cases additional information on the chemical composition of the uppermost monolayer can be obtained by the electron induced ion emission from the surface.