Auger Electron Spectroscopy

Auger Electron Spectroscopy

1. AUGER ELECTRON SPECTRSCOPY By- Manish Sahu M.Sc. Chemistry (Final) Sp.- Physical Chemistry

2. Synopsis:- Introduction History Principle of AES Steps Instrumentation Graphical representation Advantages Disadvantages/Limitation Application of AES References AUGER ELECTRON SPECTROSCOPY

3. Introduction:- Auger electron spectroscopy (AES), is a widely used technique to investigate the composition of surfaces of solids. It can also be used for the study of surfaces ,oxidation catalysis , chemistry of fractured interfaces and more generally in the area of material science . AUGER ELECTRON SPECROSCOPY

4. History:- The phenomenon of Auger electron spectroscopy was first discovered in 1923 by “ Lise Meitner” and later independently discovered once again in 1925 by “Pierre Auger”. AUGER ELECTRON SPECTROSCOPY

5. Principle of Auger electron spectroscopy A fine focused electron beam bombards the sample and ejects an electron of the inner shell of the atoms. The vacancy must be refilled by an electron from a higher energy level. When the higher energy electron fills the hole, the release of energy is transferred to an electron in an outer orbit electron. The electron has sufficient energy to overcome the binding energy and the work function to be ejected with a characteristic kinetic energy. AUGER ELECTRON SPECTROSCOPY

6. AUGER ELECTRON SPECTROSCOPY The ejected electron is referred to as an Auger electron after Pierre Auger.

7. Principle continue............ AUGER ELECTRON SPECTROSCOPY

8. Auger electron spectroscopy is a two step phenomenon :- Step 1:- Involve the formation of electronically excited ion. With x-ray :- With electron beam: :- Incident electron from the source. :- Shows the same electron after it has interacted with“A ” and has lost some of its energy . :- Indicates the ejected electron from one of the inner orbital of “A” . AUGER ELECTRON SPECTROSCPY Steps of Auger process i i A i i

9. Step2:- Relaxation process The relaxation of the excited ion can occur in two way:- AUGER ELECTRON SPECTROSCPY A f (Auger electron) (x-ray fluorescence)

10. Instrumentation:- AUGER ELECTRON SPECTROSCOPY Fig.- Instrumentation of auger electron spectroscopy

11. The essential components of an AES are:- UHV Environment. Electron gun. Electron energy analyzer. Electron detector. Data recording, processing and out put system. AUGER ELECTRON SPECTROSCOPY

12. Graphical representation Fig: - Graph between atomic number and yield per shell vacancy. AUGER ELECTRON SPECTROSCOPY

13. Advantages :- Surface sensitive. Elemental and chemical composition analysis by comparison with standard sample of known composition. Detection of elements heavier than Li. Very good sensitive for light elements. AUGER ELECTRON SPECTROSCOPY

14. Disadvantages/Limitation Analyzes conducting and semiconducting samples. Special procedure are required for non-conducting samples. Only solid specimen can be analyzed. Samples that decompose under electron beam irradiation cannot be studied. Hydrogen and helium are not detectable as they have electron less than three. AUGER ELECTRON SPECTROSCOPY

15. Application :- Chemical shifts can be seen by Auger spectral peaks. AES also throws light on the various oxidation states of the elements. All elements except hydrogen and helium can produce Auger spectra, in which the area under the peak is measured to give a quantitative picture. AES is largely used for qualitative analysis of solid surface. AES is also use for depth profiling of surfaces. An Auger microprobe is used, to produce a beam that can be moved across a surface. AUGER ELECTRON SPECTROSCOPY

16. References:- Chatwal G.R . , Instrumental method of chemical analysis, 1 st edition, Himalaya Publishing house; 2004 , page No. 3.18 – 3.21 Banwell Colin N. , Fundamentals of Molecular Spectroscopy, 4 th edition, McGraw Hill Education Private Limited; 2016 , page No. 194-196 Kaur H. , Spectroscopy , 28 th edition, Pragati prakashan 2016, Page No. 643-646

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