Use of differential surface charging to separate chemical differences in x-ray photoelectron spectroscopy

✍ Scribed by Havercroft, N. J.; Sherwood, P. M. A.

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 164 KB
• Volume: 29
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/(sici)1096-9918(200003)29:3<232::aid-sia731>3.0.co;2-6

✦ Synopsis

Differential sample charging is a potential problem in x-ray photoelectron spectroscopic studies of insulating or partially conducting materials, especially when monochromatic x-radiation is used. The phenomenon can be exploited to distinguish between compounds that do not exhibit a significant chemical shift but do have significant differences in sample conductivity. This paper shows how sample biasing using large d.c. negative biases can be used to identify chemical differences in an important practical system consisting of oxide films on an aluminum alloy (6061) with a significant level of contamination involving a heavily contaminated dark area and a lightly contaminated light area. The two areas exhibit significantly different spectral behavior, but in both cases differential charging assists analysis, allowing different carbon environments (disordered graphitic carbon and lubricant hydrocarbons) to be distinguished. Changes in the aluminum and magnesium core regions allow an estimate of the differences in oxide thickness to be obtained. The use of positive sample biasing to eliminate differential sample biasing is also illustrated.