Electron probe microanalysis EPMAWhat’s the point?Image AcquisitionImage Processing & AnalysisResources:Secondary electron imagesBSE imagesVariations on a themeEBSD*BSE and SE Detectors on our SX51CathodoluminescenceCL: in living colorCL Microscope AttachmentsCL: colors and eVCL: defects in GaAsCL: quartz, zirconX-ray mapsX-ray map defocusMosaic ImagesX-ray maps …. And the ClockX-ray maps … Fully quantitativePowerPoint PresentationSlide 23Histogram Stretching Before BSE AcquistionSX51Microscope ImagesImage StorageSome Image FormatsImage DefectsImage Enhancement - by MachineImage Enhancement - Done LaterIntensities, Histograms, LUTsBrightness and Contrast: or How I Learned to Love the HistogramGamma ProcessingHistogram Levels & EqualizationKernels/Rank OperatorsNeighborhood averagingImage Math2 Dimensional HistogramsProcessing in Frequency SpaceLook Up TablesProcessing binary imagesThresholdingMaking an Image into a BinaryBoolean* OperationsColor Superposition of Elemental MapsErosion/DilationImage measurementsConclusionAcquiring and Processing Acquiring and Processing Electron, X-ray, Electron, X-ray, and CL and CL imagesElectron probe microanalysisEPMAWhat’s the point? “A picture is worth a thousand words”. The more we know about how images are acquired and processed, the better we can present research results graphically. Additionally, 2 or 3 dimensional information about specimens can be extracted from some images.Image Acquisition• Secondary electron images• Backscatter electron images• X-ray maps (WDS, EDS)– Dot maps– Counter maps• Cathodoluminescence images• Microscope (camera) images• MicroImage vs Matrox framegrabberImage Processing & Analysis• Image acquisition• Image storage• Image defects/correction• Image enhancement• Segmentation and thresholding• Processing in frequency space• Processing binary images• Image measurements• Image presentationResources:Software• MicroImage (interfaces with SX51)• Matrox Intellicam (interfaces with SX51 video display)• NIH/Scion Image for a manual-article-tutorial, go to rsb.info.nih.gov/nih-image/more-docs/Tutorial/Contents.html• Adobe Photoshop• Image Processing Tool Kit (Russ/Reindeer Games) – plug-ins for Photoshop • Graphic Converter (Mac)Books• The Image Processing Handbook by John C. Russ, 3rd Ed, 1999, CRC Press (he teaches a week-long short course at North Carolina State University)• Quick Photoshop for Research, A guide to digital imaging for Photoshop 4xd, 5x,6x,7x by Jerry Sedgewick, 2002, Kluwer Academic/Plenum PublishersSecondary electron imagesSE imaging: the signal is from the top 5 nm in metals, and the top 50 nm in insulators. Thus, fine scale surface features are imaged. The detector is located to one side, so there is a shadow effect – one side is brighter than the opposite.Everhart-Thornley detector: low-energy secondary electrons are attracted by +200 V on grid and accelerated onto scintillator by +10 kV bias; light produced by scintillator (phosphor surface) passes along light pipe to external photomultiplier (PM) which converts light to electric signal. Back scattered electrons also detected but less efficiently because they have higher energy and are not significantly deflected by grid potential. (image and text from Reed, 1996, p. 37)BSE imagesBSE imaging: the signal comes from the top ~.1 um surface; solid-state detector is sensitive to light (and red LEDs). Above, 5 phases stand out in a volcanic ash fragmentA solid-state (semi-conductor) backscattered electron detector (a) is energized by incident high energy electrons (~90% E0), wherein electron-hole pairs are generated and swept to opposite poles by an applied bias voltage. This charge is collected and input into an amplifier (gain of ~1000). (b) It is positioned directly above the specimen, surrounding the opening through the polepiece. In our BSE detector, we can modify the amplifier gain: BSE GMIN or BSE GMAX.Goldstein et al, 1992, Fig 4.24, p. 184There are several alternative type SEM images sometimes found in BSE or SE imaging: (left) channeling (BSE) and (right) magnetic contrast (SE). I have found BSE images of single phase metals with crystalline structure shown by the first effect, and suspect the second effect may be the cause of problems with some Mn-Ni phases.Crystal lattice shown above, with 2 beam-crystal orientations: (a) non-channeling, and (b) channelling.Less BS electrons get out in B, so darker.From Newbury et al, 1986, Advanced Scanning Electron Microscopy and X-ray Microanalysis, Plenum, p. 88 and 159.Variations on a themeEBSD*(Left) EBSD pattern from marcasite (FeS2) crystal. (Right) Diagram showing formation of cone of diffracted electrons formed from a divergent point source within a specimen.Electron backscatter diffraction is a relatively new and specialized application whereby a specimen (say single crystal) is tilted acutely (~70°) in an SEM with a special detector (‘camera’). The electron beam interacts with the crystal lattice and the lattice planes will diffract the beam, with the backscattered electrons striking the detector, yielding sets of intersecting lines, which then can be indexed and crystallographic data deduced.* Also referred to as Kossel X-ray diffraction, and Kikuchi patterns.Dingley and Baba-Kishi, 1990, Electron backscatter diffraction in the scanning electron microscope, Microscopy and Analysis, May.BSE and SE Detectors on our SX51View from inside, looking up obliquely (image taken by handheld digital camera)Plates for +voltage for SE detectorAnnular BSE detectorsAnti-contamination air jetCathodoluminescenceThis is an optical phenomenon. CL occurs in semiconductors, be they man-made or natural (i.e., some minerals). Electrons in the valence band of these materials are excited into the conduction band for a brief time; subsequently these electrons recombine with the holes left in the valence band. The energy difference is released as a photon of wavelength of light.Two commonly used applications are(1) Locating strain (lattice mismatch) in semiconductors, and (2) Evaluating minerals for heterogeneous growth (complex history, overgrowths, dissolution, crack infilling)There are two distinct methods to image this effect: by SEM or microprobe, or by a small attachment to an optical microscope (static cold cathode electron source). Additionally, the light spectra can be quantified by a scanning monochronometer.CL: