While analysing the Al alloy sample via XPS, I am getting the Oxygen value of 80% on the surface. Then I etched with an interval of 30sec, 30 sec, 1 min, 5 min, 10 min. The last etched surface provided me the Oxygen content to be 50% even though I reached within the material. It should not happen. What would be the possible reason behind this behavior? Can someone provide me with relevant literature?
Dear Dr. Jijo Christudasjustus ,
with respect to the thin passivating film that forms spontaneously on the surface of Al Alloys (thickness between 1 and 10 nm), a technique like XPS provides information on the oxide film chemical composition and its thickness, film alloying element content and the presence of impurities. The composition of the thick corrosion products layer that could form subsequently during humidity exposure can also be determined but the sputtering conditions must be more severe. In general, the information obtained by the XPS technique leads to a better understanding of corrosion phenomena and mechanisms.
For more details, please see the following note/paper:
-Thickness of passive film on the Al R.W. Revie, Uhlig’s Corrosion Handbook, third ed., John Wiley & Sons, New Jersey, 2011
-The Application of X-Ray Photoelectron Spectroscopy in Understanding Corrosion Mechanisms of Magnesium and Mg-Al Alloys
Sebastián Feliu Jr., C. Maffiotte, Juan Carlos Galván, Angel Pardo, Maria Concepción Merino and Raul Arraba
Science Journal, 3, 1-14 (2011)
Available at: https://benthamopen.com/contents/pdf/TOSURSJ/TOSURSJ-3-1.pdf
Best regards, Pierluigi Traverso.
Well.Oxygen forms the residual atmosphere in your vacuum chamber (XPS instrument), and essential part, if you do not use cryo panel or backup of the system before analysis, due to water vapor. At 10-6 Torr there is one mono atomic layer of residual gas molecules adsorbed of the surface of analyzed sample per second. So, for this vacuum level Al oxide should be formed very quickly. XPS method lets you opportunity to analyze a top surface layer of around 1-10 nm thick, depends on the photo-electrons used for analysis. So, the high oxygen concentration in your case says about a bad vacuum in your system or a leakage (in the ion source, used for sputtering, for example).
dear Jijo Christudasjustus;
if you immerse your sample in a strong alkaline solution or acidic solution (nitric acid HNO3 or NaOH) solution to remove the oxide film from the surface, you will see different results
Perhaps, you may find some information in:
Article Influence of alloying elements and etching treatment on the ...
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