Xray Analysis 1 XRay Tools Energy Dispersive Xray

X-ray Analysis 1

X-Ray Tools Energy Dispersive X-ray Spectroscopy (EDS) n Wavelength Dispersive X-ray Spectroscopy (WDS) n X-ray photoelectron spectroscopy (XPS) n X-ray diffraction (XRD) n X-ray fluorescence (XRF) n 2

Energy Dispersive X-Ray Spectroscopy, EDS Element maps n Spectra n Applications n System overview n System image n X-Ray detector n 3

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EDS Element Map 5

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EDS Applications n n n Used to determine the elemental composition of a sample. Can perform both qualitative (What is it? ) and quantitative (How much? ) analysis. Depending on the window low atomic number elements may not be visible. Super ultra thin windows detect down to berilium. Older detectors may only detect fluorine and higher. Window less detectors are available. 8

EDS Image 9

Energy Dispersive X-Ray Detector System 10

Solid state Si Li X-Ray Detector Insert image 11

Energy Dispersive X-Ray Detector System CPS: Counts per second. This is the number of X-rays detected each second. Dead Time: This is the percentage of X-rays rejected. Optimal collection rates occur at dead times of approximately 30 -40 %. Resolution is the ability to distinguish between two X-rays with similar energy. Longer integration time results in better resolution but greater dead time. 12

Energy Dispersive X-Ray Detector System 1. An X-Ray strikes the Si Li Detector creating electron hole pairs 2. These are drawn to opposite sides of the detector due to the voltage creating an electrical current. 3. The current pulse is amplified and integrated for the duration of the window. 4. The longer the integration time the greater the resolution of the X-ray energy however dead time will increase. 5. If two X-rays strike the detector at the same time they will be rejected by the pile-up director. 13

Vendors n EDAX http: //www. edax. com/index. html n Princeton Gamma Tech http: //www. pgt. com/ n Noran/Kevex/Thermo http: //www. thermo. com/BURedirect/welcome. Msg/1, 5107, 28, 00. html n Oxford Instruments http: //www. oxinst. com/ 14

Energy Dispersive X-Ray Spectroscopy, EDS Element maps n Spectra n Applications n System overview n System image n X-Ray detector n Vendors n 15

Wavelength Dispersive X-Ray Spectroscopy, WDS System Overview n Detector n Image n 16

WDS Detector Insert image 17

WDS Detector Insert image 18

Wavelength Dispersive X-Ray Spectroscopy System Overview n Detector n Image n 19

X-Ray Photoelectron Spectroscopy, XPS Insert image 20

Example of XPS Insert image 21

X-ray Photoelectron Process Insert image 22

X-Ray Photoelectron Spectroscopy n n n An incoming X-Ray removes a core electron which will have a characteristic energy based on the difference between the initial X-Ray energy, which is of known energy, and the energy to remove the inner electron from the atom, which is characteristic. This has very high sensitivity 100 ppm Area is somewhat large at 10 -200 microns 23

X-ray Fluorescence XRF n n X-rays are directed at a sample and X-rays given off from the sample are analyzed with either EDS or WDS. Atmospheric systems are available which are useful for detecting lead in products. Insert image from Thermo electron 24

Links n n n http: //hyperphysics. phyastr. gsu. edu/hbase/quantum/hydazi. html#c 3 http: //elchem. kaist. ac. kr/vt/chem-ed/analytic/acmeths. htm http: //elchem. kaist. ac. kr/vt/chem-ed/scidex. htm http: //www. nanopicoftheday. org/ http: //www. physics. berkeley. edu/research/crommie/index. html 25

X-Ray Diffraction, XRD Applications n System overview n Theory n Simulations n 26

Müller’s Micrograph http: //www. ornl. gov/info/ornlreview/rev 28 -4/text/atoms. htm 27

X-Ray Diffraction 28

X-Ray Diffraction http: //www. matter. org. uk/diffraction/x-ray/default. htm 29

XRD n http: //www. matter. org. uk/diffraction/Default. htm http: //www. uniwuerzburg. de/mineralogie/crystal/teaching. html http: //dept. physics. upenn. edu/~heiney/talks/hires. html n http: //www. mrl. ucsb. edu/mrl/centralfacilities/xray-basics/ n n X-rays are diffracted by a crystal to form a pattern on a photographic plate. n Analyzing this pattern can reveal the structure of the atoms. n Single crystals or powders can be used. n 30

XRD System Overview Insert image from ICE document 31

Fraunhofer and Bragg Diffraction Comparison Insert image 32

XRD n http: //www. matter. org. uk/diffraction/Default. htm n http: //www. uni-wuerzburg. de/mineralogie/crystal/teaching. html n http: //dept. physics. upenn. edu/~heiney/talks/hires. html http: //www. mrl. ucsb. edu/mrl/centralfacilities/xray-basics/ n 33

http: //en. wikipedia. org/wiki/X-ray_fluorescence 34

X-Ray Tools Energy Dispersive X-ray Spectroscopy (EDS) n Wavelength Dispersive X-ray Spectroscopy (WDS) n X-ray photoelectron spectroscopy (XPS) n X-ray diffraction (XRD) n X-ray fluorescence (XRF) n 35