(XPS)-2 - Washington State University

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XPS: It arises as a consequence of the build-up of a positive charge at thesurface of non-conducting specimens. The rate of photo-electron loss isgreater than that of their replacement from within the specimen.It produces a retarding field at the surface that wille -hνshift the peaks (reduce the KE of the ejected electrons).Suggestions:Static Charging1) Use of the adventitious Carbon line to correct any shift (most materialsexhibit a C 1s line).2) Deposition of a very thin layer of gold (as use in SEM).3) Use of a “flood gun” low energy electrons (0-5 eV).+ + + +-----
Static Charging (cont.)Auger: Sample charging is a function of the total electron yield, f (Σ). Σ isthe sum of secondary electron and backscattering coefficient.Σ > 1 samples charge positively. Auger (and XPS) peaks shift to lower KE(higher BE).Σ < 1 samples charge negatively. Auger (and XPS) peaks shift to higher KE(lower BE).Case 1, the emitted electrons have a reduced KE by a few tens of eVIdentification remains possibleCase 2, the KE of the emitted electrons increases due to the repulsive forcesbetween the charged surface and emitted electrons.Analysis is often impossible.
Page 5 and 6: Six features seen in a typical XPS
Page 7 and 8: F 1s peakSharp Peak (core level)O 1
Page 9 and 10: Vacancy created by photoionization
Page 11 and 12: Shake-up satellites: distinct peaks
Page 13 and 14: Auger featuresAuger electron emissi
Page 15 and 16: x 10 3Oxidized surfaces12Cr 2p ---d
Page 17 and 18: Chemical BondingThe curve fitting o
Page 19: Intensity ratio is given by (2j - +
Page 24 and 25: Peak Widths and IntensitiesPeak wid
Page 26 and 27: Quantitative Analysis (cont.)Sx=( A

(XPS)-2 - Washington State University

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