Electron probe microanalysis of submicron coatings containing ultralight elements

Wavelength-dispersive electron probe microanalysis (EPMA) is presented as a sensitive and accurate technique to study the composition of thin films containing several of the ultralight elements (B, C, N, O) in combination with a metal. The sensitivity for the ultralight elements reaches its maximum at electron energies of 5 - 10 keV. The corresponding ultimate depth of x-ray emission (Rsube) is low, typically "bulk" analysis can be carried out on coatings with a film thickness of only 0.2 - 0.4 Mym. A lateral-resolution of 0.6 Mym is demonstrated under conditions of quantitative analysis. The minimum or blank level for the determination of carbon and oxygen, caused by surface contamination, can be reduced to 0.1-0.3 wt% by use of a hydrogen gas jet device. Quantitative analysis, based on peak area k-ratios, is performed by the PAP matrix correction model. For some thin film materials the results of EPMA are compared with those established by Rutherford Backscattering Spectrometry and c hemical analysis. An accuracy of at least 5% can be estimated for quantitative electron probe microanalysis of complex compositions at conditions of Rsube is smaller than 0.5 Mym.