ED and WD X-ray Analysis Elemental analysis in the SEM The ‘what’, ‘where’ and ‘how much’?

‘What’ - Identifying the elements Locate the electron beam on the region of the sample Start acquisition Spectrum shows peaks Elements are identified and labelled The higher the peak is above the background, the higher the concentration of that element

X-ray Generation L lines K lines Demonstrate K and L series lines for, say, Fe and Mo using spectrum synthesis L lines K lines

X-ray line series Sn L series Ca K series

ED and/or WD? Energy dispersive Measures X-ray from its energy Wavelength dispersive Measures X-ray from its wavelength Energy in keV = 12.398/ wavelength in Angstroms High energy = short wavelength Low energy = long wavelength

ED detectors Old type Si(Li) detectors needed to be kept at liquid nitrogen temperature New type SDD detectors are cooled to Peltier temperature X-ray energy converted to charge pulse and then to a voltage pulse Simultaneous acquisition of elements Be to U Mention X-ray pulse processor

WD spectrometer Diffraction according to Bragg’s law nλ=2dsinθ Much better peak resolution then ED Much better sensitivity for trace elements Sequential analysis of elements Be to U How to play media clips by using Windows Media Player To play media clips in PowerPoint by using Windows Media Player, follow these steps, as appropriate for the version of PowerPoint that you are running. Microsoft PowerPoint 2000, Microsoft PowerPoint 2002, and Microsoft Office PowerPoint 2003 Start PowerPoint, and then open the presentation that you want. On the View menu, point to Toolbars, and then click Control Toolbox if it is not already selected. In the Control Toolbox, click More Controls. In the list of controls, click Windows Media Player. Click anywhere in your slide, and then draw a box by using your mouse pointer to create a Windows Media Player control. In the Control Toolbox, click the Properties button. In the File Name box of the Properties dialog box, type the path and name of the file that you want to play, and then press ENTER. For example, type the following line to play the movie file Mymovie.avi from the desktop: Close the Properties dialog box. The media clip now plays automatically when you view the slide. You can also change other properties of the clip, such as looping and size, in the Properties dialog box. Note To add a movie by using Windows Media Player version 9.0 and later versions of Windows Media Player, click the Custom property in the Properties dialog box, and then click the ellipsis button (...). Locate the movie file that you want to play. Select the movie, click Open, and then click OK.

ED and WD together resolution sensitivity Explain advantages/disadvantages of ED/WD Why it’s good to use both

What can be analysed? Just about anything you can put in the SEM! Microanalysis – typical volume analysed about 1µm Depends on accelerating voltage and density Nanoanalysis – need to reduce electron beam penetration Reduce accelerating voltage For best results the sample should be flat and polished and conducting But often you can achieve adequate results from ‘rough’ samples

Typical applications Comparing ‘good’ and ‘bad’ samples Identifying compositions in fine grain structures Identifying sources of contamination Measuring variation in composition across an interface

Industrial and research applications Failure analysis - automotive, aerospace, semiconductors Materials research Quality Control Photovoltaics Light Emitting Diodes Thin film analysis Artefact conservation Steel inclusions Gun Shot Residue forensics

‘Where’ - Mapping Scan the electron beam and acquire X-ray information at each pixel position Display the results as a series of maps for each element or as a single colour image

Individual maps

ED spectrum at each point

Interaction volume Ni 5kV 0.1 µm 1µm Si 5kV 0.4 µm

Mapping large areas Field width 0.53mm 3x3 maps stitched WD geometry requirement – will defocus at low mag.

‘How much’ – Quantitative Analysis Element Weight% Al K 1.42 Ti K 1.29 Cr K 17.46 Fe K 33.65 Ni K 42.29 Mo L 3.88 Totals 100.00

Processing for quant Measure peak areas Compare with standards Apply inter-element corrections For accurate results, the sample should be flat, polished, homogeneous (on the micro-scale) and conducting

Detection limits Typically 0.1% to 0.5% for ED Order of magnitude better for WD Exact detection limit depends on operating conditions and composition

ED or WD? ED for major elements, fast analysis, rough samples Ideal for a ‘quick look’ WD for minor and trace elements and overlaps Better sensitivity and resolution, but slow ED and WD are complementary techniques for analysis