PROSPECTS FOR QUANTITATIVE CHEMICAL MAPPING OF SURFACES USING THE SURFACE-ANALYSIS BY LASER IONIZATION (SALI) TECHNIQUE

Determination of the lateral distributions of constituents on surfaces is important in a large variety of applications. Although scanning Auger electron spectroscopy (AES) is commonly used, better sensitivity can often be achieved by scanning SIMS within practical time constraints. However, this depends strongly on both the species of interest and the local matrix of the sample. Large variations in secondary ion yields among species lead to severe difficulties in the quantitative interpretation of SIMS chemical maps. Surface Analysis by Laser Ionization (SALI) is a recently developed technique that uses non-resonant multiphoton ionization of neutral species emitted from the sample surface. In most situations, the neutrals constitute a much greater portion of the sputtered material than do the secondary ions, and so are much less sensitive to variations in secondary ion yields. The result is that SALI data can be quantified more easily than SIMS data, while achieving comparable detection sensitivities. In this paper, the prospects for quantitative chemical mapping of surfaces is evaluated for SALI using recent experimental results for achievable useful yields. The theoretical detection capabilities of SALI is compared to that for SIMS and AES as a function and spatial resolution. It is demonstrated that the capabilities of SALI compare very well with those of SIMS and AES in applications of surface chemical mapping at high spatial resolution.