Secondary electron detector
description
Transcript of Secondary electron detector
![Page 1: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/1.jpg)
Secondary electron detectorelectron strikes scintillator and converted to light pulse - Amplified and displayed
Raster the beam over sample and display at the same time and get image (basically an intensity map)
Scan smaller and smaller areas to increase magnification
Object: Convert radiation into an electrical signal which is then amplified
SelectSecondary electronsBackscattered electronsX-raysAuger electronsPhotons from CathodoluminescenceAbsorbed electron current
Incident beamLight
(cathodoluminescence)
BremsstrahlungSecondary electrons
Backscattered electrons
heat
Elastically scattered electrons
Transmitted electrons
Specimen current
Auger electrons
Characteristic X-rays
Sample
Any of the collected signals can be displayed as an image if you either scan the beam or the specimen stage
5 mm
Signal Detection
![Page 2: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/2.jpg)
Electron DetectorsScintillator – Photomultiplier system (Everhart-Thornley, 1960)1) Electron strikes scintillator
plasticLi-glassCaF2 (Eu)P47
Photons produced
2) Light conducted by light pipe to photomultiplier3) Signal passes through quartz window into photomultiplier4) Photons strike electrodes – emit electrons (photoelectric effect)5) Electrons cascade through electrode stages
output pulse with 105 – 106 gain
![Page 3: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/3.jpg)
Up to 300V potential to collect secondary electronsDeflect – does not require line-of-sight geometryCollection efficiency ~ 50% SE
~ 1-10% BSE
![Page 4: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/4.jpg)
Backscattered Electron DetectorsUsually solid state devicesAnnular – thin wafer (Si semiconductor)
Extrinsic p-n junctionp-type = positive charge carriers (holes) dominantn-type = negative charge carriers (electrons) dominant
Use Li as donorUse B as acceptor
![Page 5: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/5.jpg)
1) Backscattered electron strikes semiconductor2) Valence electron promoted to conduction band – free to move
Leaves hole in valence band3) No bias → recombination
Forward bias → current
~ 3.6 eV expended per electron / hole pairCurrent of 2800 electrons flows from detector if 10keV electron enters
4) Amplify signal5) Display
![Page 6: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/6.jpg)
Energy-filtered electron detectorsIn lens detectors
EsB = Energy selective backscatteruses filtering grid
AsB = Angle selective backscatteruses angle
![Page 7: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/7.jpg)
![Page 8: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/8.jpg)
INLENS SE image from a sectionedsemiconductor. Clearly visible: No BSE contrast!
The same section but seen with the LL-BSE; detected with the INLENS EsB at 1.27 kV
Si
Ti
TiN
Si3N4
![Page 9: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/9.jpg)
Simultaneously acquired In-lens SE (left) and EsB image (right) from a fuel cell showing the outer electrode. We see doped ZrO2 and different phases of Ni-oxide.
![Page 10: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/10.jpg)
Gold particles seen with the In-lens SE and AsB detector. We see surface contrast with the In lens SE and crystalline contrast from single elastic scattered BSE electrons (Mott scattering).
![Page 11: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/11.jpg)
11
Beam deceleration: enhancing resolution and contrast
If Bias=0 (no BD):Landing V = HV
What is beam deceleration?New optics mode enabling high resolution imaging and high surface sensitivity at very low kV
BD specifications:• Landing energy range: 30 keV down to 50 eV• The deceleration (Bias) can be continuously adjusted
by the userBenefits:
• Enhances the resolution • Provides additional contrast options• Greatest benefit at 2kV and below
Bias
HVLanding V
Beam
vCD
Sample
TLD
2-mode final lens
![Page 12: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/12.jpg)
Gold on carbon1kV1.75MX imaging, <0.9nm resolution
Gold on carbon2kV2.8MX imaging, <0.8nm resolution
Deprocessed IC1kV600KX imaging
Pt catalyst nanoparticles2kV1.0MX imaging
![Page 13: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/13.jpg)
Low voltage-high contrast detector with beam deceleration
Through-the-lens detector with beam deceleration
Through-the-lens detector without beam deceleration
Pt sample. Landing energy 2keV, Beam deceleration=4kV.
![Page 14: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/14.jpg)
Image FormationScanning
Signals are produced as beam strikes sample at single locationTo study an area, must scan either beam or sample stage
For beam scanning, there are 2 pairs of scan coils deflecting the beam in X and Ylocated in bore of objective lens
![Page 15: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/15.jpg)
Produce a matrix of points – a map of intensities
Output displayed on screen or collected digitally
Each point on specimen corresponds to point on screen
Scanning is synchronized
Emission characteristics produce contrast in resulting imageTopographyAtomic # differencesEtc.
![Page 16: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/16.jpg)
MagnificationRatio between size of display screen (or recorded image) and size of area on specimen
M = L / lL = length of scan line on screenl = length of scan line on specimenL is fixed, so magnification changed by changing area scanned on specimen
Mag Area on Sample 10X 1 cm2
1000X 100 μm2
100,000X 1 μm2
specimenscreen
1X10X
![Page 17: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/17.jpg)
Picture ElementRegion on specimen to which beam is addressed and from which information is transferred to screenHigh resolution screen spot size ~ 100μm diameterCorresponding picture element depends on magnification
Picture Element size = 100 μm / magnification= L / NL = length of scan line on specimenN = Number of picture elements along
the scan line (lines / frame) Mag Picture Element Size 10X 10 μm 1000X 0.1 μm100,000X 1.0 nm
True focus: area sampled is smaller than picture element sizeIf beam sampling area extends to at least 2 picture elements
= blurring = “hollow magnification”No additional information gained by increasing magnification
![Page 18: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/18.jpg)
Depth of FieldDetermined by distance where beam broadening exceeds one picture elementBeam broadening due to divergence angle
![Page 19: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/19.jpg)
Depth of field
Plane of focusD
Region of image in effective focus
Long working distance
Sample surface
Short working distance Insert smaller objective aperture to improve D
![Page 20: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/20.jpg)
Depth of Field (D) Aperture radius( μm)
Mag. 100 200 600 10X 4 mm 2 mm 670 μm 1000X 40 μm 20 μm 6.7 μm100,000X 0.4 μm 0.2 μm 0.067 μm
Must choose between two modes of operation1) High resolution = short working distance2) High depth-of-field = long working distance and / or small aperture
Compared to light microscopes at the same magnificationSEM 10 – 100 X greater depth-of-field
![Page 21: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/21.jpg)
Contrast originsCompositional differencesDifferent emitted current intensities for scanned areas of different average atomic #
BSE intensity is a function of Z1) Regions of high average Z appear
bright relative of low Z areas2) The greater the Z difference = greater
obtainable contrast3) High Z = high η, so z contrast not as
high for adjacent pairs of elements higher in periodic chart
![Page 22: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/22.jpg)
Electron Backscatter
Backscattering more efficient with heavier elements
Can get qualitative estimate of average atomic number of target
Image will reveal different phases
Brighter = higher average Z
![Page 23: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/23.jpg)
TopographyBackscattered electrons
If ET detector not biased, or negatively biasedIf no SEs are detected, then only those BSEs scattered directly into detector will be counted (line-of-sight geometry)Those surfaces facing detector will be brightAs if viewing specimen with light source in direction of detector
![Page 24: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/24.jpg)
TopographySecondary + Backscattered electronsET detector positively biasedCollect secondary electrons emitted from all surfaces, more where incidence angle is highEntire surface appears illuminatedAlways some contribution of BSEshigh Z areassurfaces oriented toward detector
![Page 25: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/25.jpg)
Solid-state detection system - application of the p-n junction diode
Take p-type SiApply Li to surfaceDiffuses to form p-n junctionApply reverse bias at high temp (room temp)
expands intrinsic regionMust keep cold (LN2 = 77K) or Li will diffuse
++++++
Depletion width W
Space-charge layers
Direction of built-in field
-------
p n
X-Ray spectrometryEDS: Energy dispersive spectrometry
![Page 26: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/26.jpg)
Inelastically scattered – absorbedNumber of charges created:
N = E / ЄE = photon energyЄ = 3.8 eV for Si5 KeV photon → 1300 electrons (2 X 10-16 C)
4) Potential sweeps electrons and holes apart
-500 to -1500 V
1) After passing through isolation / protection window (Be, BN, C, etc.) X-ray absorbed (photoelectric absorption) by Si
2) Inner shell ionization of Si → electron ejected with energy = 1.84 eVPhotoelectron creates electron-hole pairs (elevating electrons to the conduction
band)3) Relaxation of the Si back to the ground state → SiK X-ray or Auger electron
![Page 27: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/27.jpg)
To preamplifier
X-rays
p-type region (dead layer ~ 0.1μm)
Li-drifted, intrinsic region
n-type region
Gold contact surface (~2000Å)
Gold contact surface (~200Å)
Electronsholes
X-Ray spectrometryEDS: Energy dispersive spectrometry
![Page 28: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/28.jpg)
6) Leads to output pulse (convert charge to voltage in preamplifier)
→ linear amplifier7) Sort by voltage in a multichannel analyzer
→ voltage histogram
![Page 29: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/29.jpg)
EDSResolution ~ 150 eVIf separation < 50eV, very difficult to resolve
If looking for a minor element in the presence of major elements, need even more separation (200eV or more)
Fe – CoTi – VCr – MnPb – SBa – TiSi – SrW - Si
![Page 30: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/30.jpg)
EDS detector
![Page 31: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/31.jpg)
Silicon Drift Detector (SDD)
Conventional diode = homogeneous electric field between layersSDD = radially gradient potential field in active volumeElectrons guided toward center readout nodeCan process very high count rates (up to 1,000,000 cps)No LN2 cooling
![Page 32: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/32.jpg)
Wavelength Dispersive Spectrometry (WDS)Bragg Law:
θ
nλ = 2d sinθ
d
At certain θ, rays will be in phase,otherwise out of phase = destructive interference
cambridgephysics.com – Bragg’s Law demonstration
![Page 33: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/33.jpg)
d is known - solve for λ by changing θMove crystal and detector to select different X-ray lines
Si Kα
S Kα
Cl Kα
Ti Kα
Gd Lαsample
Crystal monochromator
Proportional counter Maintain Bragg condition = motion of
crystal and detector along circumference of circle (Rowland circle)
![Page 34: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/34.jpg)
![Page 35: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/35.jpg)
Spectrometer focusing geometryCurve crystal to improve collection efficiency
Crystal bent to 2R Crystal bent to 2R, then ground to R – All rays have same angle of incidence and focus to detector
![Page 36: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/36.jpg)
VLPET
![Page 37: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/37.jpg)
Only small areas of the sample will be “in focus” for vertical spectrometers
In focus region = elongate ellipsoid on sampleFor vertical spectrometers –
Shortest axis of focus ellipsoid coincides with stage Z (parallel to electron optic axis)
Stage focus extremely importantLight optical system = very short depth of field
Advantageous for focusing X-ray optics
![Page 38: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/38.jpg)
MonochromatorsUse different crystals (or synthetic multilayers) with different d-spacings to get different ranges in wavelengthSmaller d = shorter λ detection and higher spectral resolution
synthetic crystalspseudocrystals (e.g., stearate films on mica)layered synthetic microstructures (multilayers) - LSM
“crystal” 2d(Å)LIF Lithium flouride 4.0PET Pentaery thritol 8.7TAP (TlAP) Thallium acid phthalate
25.76Ge Germanium 6.532LAU Lead laurate 70.0STE Lead stearate 100.4MYR Lead myristate 79.0RAP Rubidium acid phthalate 26.1CER Lead cerotate 137.0LSM W / Si W / C 45
60809098
![Page 39: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/39.jpg)
![Page 40: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/40.jpg)
![Page 41: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/41.jpg)
Lowest Z diffracted Resolution Count RatesKα Lα
LIF K In high medium LLIF high highPET Al Kr medium high LPET medium very high VLPET medium ultra-highTAP O V low medium LTAP low highSTE B low mediumLSM Be low very high
1 5 10 50 100
Wavelength (Å)
LIFPET
TAPSTE
Resolution can be improved somewhat with use of collimating slits
LSMs
![Page 42: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/42.jpg)
Accelerating voltageMonochromator
(“crystal”)
Spectrometer number
Diffraction order
![Page 43: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/43.jpg)
K lines also available on PET
![Page 44: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/44.jpg)
K lines also available on LIFCr, Mn, Fe usually prefer LIF for high spectral resolution
![Page 45: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/45.jpg)
![Page 46: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/46.jpg)
![Page 47: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/47.jpg)
Crystal Comparison
0
100
200
300
400
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
length / PET
Inte
nsity
(cps
/nA)
PbMa
UMb
PET
LPET
VLPET
![Page 48: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/48.jpg)
Detectors for WDS analysisUsually gas filled counter tubes
1) X-ray enters tube and ionizes counter gas (Xe, Ar)2) eject photoelectron3) photoelectron ionizes other gas atoms4) Released electrons attracted to + potential on anode
wire – causes secondary ionizations and increases total charge collected
5) Collect charge and convert to output pulse – the energy of this pulse will be proportional to the energy of the X-ray - → count
![Page 49: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/49.jpg)
Gas proportional counters
Use Ar, Xe, Kr…1-3 kV on anode wirewindows
BeMylarFormvarPolypropylene
“softer” X-rays = thinner windowsCan be sealed, or gas - flow.Low energy detection: low pressure flow (Ar – 10%CH4 = P-10)Higher energy : sealed Xe (low partial pressure Xe + CH4) or high pressure P-10
![Page 50: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/50.jpg)
For P-1028 eV absorbed / electron – ion pair createdMnKα = 5.895 KeV
210 electrons directly createdIncrease signal by increasing bias and # of secondary ionizations = gas amplification factor
![Page 51: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/51.jpg)
Gas type
![Page 52: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/52.jpg)
Shift P-10 peak to lower λ by increasing pressure
High pressure
Low pressure
Xe, low pressure
![Page 53: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/53.jpg)
X-ray pulse must be processed by electronics resulting in dead timeAnother X-ray may enter during this time = not countedCorrect for (usually a few microseconds)
N = N’ / (1 – Τ N’)T = dead timeN’ = measured count rateN = actual count rate
raw
![Page 54: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/54.jpg)
Pulse Height AnalysisUsed to separate energies of overlapping lines (recall: nλ = 2d sinθ)
Variables: biasbaselinewindow
Al in chromite FeCr2O4
λ Al Kα = 8.339 Åλ Cr KβIV = 8.34 ÅE Al Kα = 1.487 KeVE Cr KβIV = 5.946 KeV
Apatite
λ P Kα = 6.157 Åλ Ca KβII = 6.179 ÅE P Kα = 2.013 KeVE Ca KβII = 4.012 KeV
baseline
![Page 55: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/55.jpg)
In integral mode the pulse height analyzer accepts all counts above the baselineIn differential mode, an energy acceptance window is employed to select a particular line
In some cases, the overlap in energy and wavelength is impossible to resolve – must use overlap correctionsV in ilmenite (FeTiO3)
V Kα = 2.5036 ÅTi Kβ = 2.51399 Å
Sr in feldsparSr Lα = 6.8629 ÅSi Kβ = 6.753 Å generally use TAP at this wavelength
baseline
![Page 56: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/56.jpg)
Pb M3-N4
Pb Ma
Pb Mb
WDS – background measurement
![Page 57: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/57.jpg)
Th Mα
Th Mβ
High net intensity (pk-bkg) and large pk/bkg
Major element analysis is primarily characterization of peaks…
![Page 58: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/58.jpg)
Measured net Int.20% error, ~350ppm error
Correct net Int.
Trace element analysis is primarily characterization of background…
![Page 59: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/59.jpg)
S sKa3,4
S Kb
S KaS K absorption edge
Increasing spectrometer efficiency
WDS – background measurement
![Page 60: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/60.jpg)
Comparison of EDS and WDS
LaPO4
![Page 61: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/61.jpg)
Comparison of EDS and WDS
![Page 62: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/62.jpg)
Comparison of EDS and WDS
![Page 63: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/63.jpg)
Comparison of EDS and WDS
![Page 64: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/64.jpg)
Comparison of EDS and WDS
La Lα1,2
![Page 65: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/65.jpg)
Comparison of EDS and WDS
La Lα1,2
![Page 66: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/66.jpg)
Th interferences on U-M regionTh absorption edges significant for high Th monazite
Brabantite
ThO2
![Page 67: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/67.jpg)
37500 38500 39500 40500 41500 42500 43500 44500 45500 465000.30
0.80
1.30
1.80
2.30
Er La2
Tm La2Tm La1 Er La1
Ho La2Ho La1 Dy La1Dy Lb1
Tb Lb4Tb Lb1 Gd Lb1
Gd Lb2,15Eu Lb1
Eu Lb3Eu Lb2,15 Sm Lb2,15
Pm Lg
Monazite GSC 8153 U-region (PET)
Wavelength (sin-q * 105)
I (cp
s/nA
)
![Page 68: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/68.jpg)
![Page 69: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/69.jpg)
![Page 70: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/70.jpg)
![Page 71: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/71.jpg)
Monazite (LIF monochromator) in wavelength region of NdL
EDS spectrum
![Page 72: Secondary electron detector](https://reader035.fdocuments.in/reader035/viewer/2022062218/568165ac550346895dd89600/html5/thumbnails/72.jpg)
EDS vs. WDS
WDS EDSElement range ≥4 ≥10 (Be) (≥ 4 thin window)Resolution to 5eV ~150eVInstant range = eV resolution entire rangeMax. count rate 50,000 cps <2000cps (SDD ~ 1,000,000)Data collection time minutes minutesArtifacts rare lotsSensitivity at least 10X EDS
Pk/bkg vs. voltage