Question

5. Consider the EDS spectra below. (10 points total) a. Indicate the background signal on the figure. b. Identify Peaks P1 and P2. Label them on the figure. c. The peak at around 1keV was identified as sodium (Na). Is Na actually present in the sample? Explain in the space below the figure. P2 21600 19200 16800 OS 14400 12000 Nak 4800 2400 OK SbM CK 100 200 300 400 500 600 700 800g 10

Answer 1

Energy-dispersive X-ray spectroscopy (EDS) is a surface analytical technique where an electron beam hits the sample, exciting an electron in an inner shell, causing its ejection and the formation of an electron hole in the electronic structure of the element. The energy of the beam is typically in the range of 10–20 keV which causes X-rays to be emitted from the sample. In general, the energy of the X-rays emitted depends on the test sample.

(a) Background signal , is peaks indicated for C-K and O-K . (usually carbon-film is used ,and 'O' is present ).

(b) From energy table analysis :

     => P1 ( 8.6 - 8.7 keV) : Zn (K_α)   ( peak ~ 9.6 keV : Zn Kβ1 => confirms this )

=> P2 ( 3.6 keV) : Sb (L_α)   ( peaks : Sb-M (0.7 keV) - 3.85 keV : Sb Lβ1 ; 4.1 keV : Sb Lβ2=> confirms this )

(c)

Automation of peak identification is extremely vulnerable to misidentifying even major peaks, especially for trace elements. This happens with software from any EDS companies. In general, automated methods statistically fail to identify major peaks 3-5 % .

~1 keV : Identified as Na-K   ; but probably Na is not present in the sample,

it might be peak for Zn (L_α) :~1 keV , which misidentified as Na-K by EDS software.