Feasibility of quantitative analysis of metals and alloys by non‐resonant multiphoton ionization of sputtered neutral species

Abstract

AbstractA system for non‐resonant multiphoton ionization (NRMPI) of suttered neutral species has been developed. The instrumentation is based on a Kratos time‐of‐flight SIMS system with a dual‐stage ion reflectron. Ionization of sputtered neutral species is provided by a focused excimer laser beam of wavelength 193 nm.Two basic operational procedures are defined that involve using either a continuous or pulsed primary ion beam for sputtering. The consequences of each mode on the resulting spectrum are considered. Characterization experiments are reported that show the effect of laser flux on the yields of elemental and molecular species, allowing conditions to be selected for subsequent experiments. The laser flux profiles demonstrate that saturation of the ionization process is easily achieved for most species studied. Relative sensitivity factors (RSFs) from elements in standard metal alloy samples are presented that suggest that some effect of matrix is present. However, reproducibility of RSFs between consecutive runs and between the pulsed and continuous modes of bombardment is very good (<10% and even <5% in some cases) for the majority of species. Values for the useful yield and detection limit in NRMPI and SIMS are compared.