Transmission Electron Microscopy Skills:Sample preparation Lecture 7

8/8/2019 Transmission Electron Microscopy Skills:Sample preparation Lecture 7

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Sample preparationample preparationLecture 7ecture 7


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OutlineutlineSafetyafetyWhy thin?hy thin?Standard laboratory methodstandard laboratory methods

Grind / polish / dimple / ion millGrind / polish / dimple / ion mill TripodTripod

XX--sectionssections

ElectropolishElectropolish && ElectrochemicalElectrochemical

TripodTripod

NanoNano--stuffstuff

Focused ion beamocused ion beam


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SafetyafetyLots of chemicals used in specimen preparationots of chemicals used in specimen preparationSome are very dangerousome are very dangerous

PerchloricPerchloric

acid in ethanol or methanolacid in ethanol or methanol

--

explosiveexplosive

Good aluminum and stainless steel etchGood aluminum and stainless steel etch Best if done in a dedicated fume hoodBest if done in a dedicated fume hood

Nitric acid in ethanolNitric acid in ethanol -- explosiveexplosive

Keep cold, dispose of it quicklyKeep cold, dispose of it quickly Hydrofluoric acidHydrofluoric acid Fantastic way to make silicon samplesFantastic way to make silicon samples Extremely dangerous, eats bone, absorption can lead to heartExtremely dangerous, eats bone, absorption can lead to heart

failure, doesnfailure, doesnttburnburn so you can miss itso you can miss it Wash for 15 min in cold water, then CalciumWash for 15 min in cold water, then Calcium GluconateGluconate solution,solution,then hospital. Be explicit and demanding about being seen quicklthen hospital. Be explicit and demanding about being seen quicklyy

Organic solvents (Acetone; 1,1,1,Organic solvents (Acetone; 1,1,1, TricholorethaneTricholorethane))

Use in a fume hood, carcinogenicUse in a fume hood, carcinogenicDispose of chemicals properlyispose of chemicals properlyRead and followead and follow MSDSSDSs http://http://www.adpc.purdue.edu/PhysFac/rem/hmm/hmm.htmwww.adpc.purdue.edu/PhysFac/rem/hmm/hmm.htm


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Sample preparationample preparationIn nearly all cases, TEM samples are best whenn nearly all cases, TEM samples are best whenvery thinery thin

100100 maximum for interpretable HREM imagemaximum for interpretable HREM image If thicker, scattering is dynamical, image cannot beIf thicker, scattering is dynamical, image cannot be

interpretedinterpreted

100100 -- 500500 for good EELS, EFI, quantifiable EDSfor good EELS, EFI, quantifiable EDS If thicker, multiple scatteringIf thicker, multiple scattering Fluorescence, absorption, difficulties in interpretationFluorescence, absorption, difficulties in interpretation

300300 -- 500 nm for diffraction contrast work500 nm for diffraction contrast work If much thicker, dynamical scattering and absorptionIf much thicker, dynamical scattering and absorption

obscure imagesobscure images


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Preparation from the bulkreparation from the bulkCross sections of thin films on substratesross sections of thin films on substrates

Cross sectionross section samplesamplese.g. imaging perpendicular to the growth directione.g. imaging perpendicular to the growth direction

1.1. Cleave two 2.5 mm x 5 mm piecesCleave two 2.5 mm x 5 mm pieces2.2. Glue these together with the growth surfaces facingGlue these together with the growth surfaces facing

each other (Meach other (M--Bond or GBond or G--1 epoxies)1 epoxies)

3.3. Use a diamond saw to section these into 150 to 200Use a diamond saw to section these into 150 to 200m piecesm pieces

4.4. Polish one side first with 320, then 600 grit sandpaperPolish one side first with 320, then 600 grit sandpaper

5.5. Mount on a Cu 2mm slot gridMount on a Cu 2mm slot grid

6.6. Polish first with 320, then 600 grit to < 20Polish first with 320, then 600 grit to < 20 mm

7.7. Ion millIon mill


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(2)2)

(1)1)(3)3)

(4)4)

(5)5)


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Sample preparationample preparationargon ion millingrgon ion millingControlled sputtering usingontrolled sputtering usingenergetic argon ionsnergetic argon ionsIncident at between 100Vncident at between 100Vand 6 kVnd 6 kVControl angle of incidence,ontrol angle of incidence,current and voltageurrent and voltageMaximum thinning rate ataximum thinning rate ataround 14round 14 - 1 66Final thinning done at lowerinal thinning done at lowerangles, currents andngles, currents andvoltagesoltages


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OutlineutlineSafetyafetyWhy thin?hy thin?Standard laboratory methodstandard laboratory methods

Grind / polish / dimple / ion millGrind / polish / dimple / ion mill TripodTripod

XX--sectionssections

ElectropolishElectropolish && ElectrochemicalElectrochemical

TripodTripod

NanoNano--stuffstuff

Focused ion beamocused ion beam


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Preparation from the bulkreparation from the bulkselfelf-supporting discs of brittle materialsupporting discs of brittle materials

Plan viewlan view samplesamplese.g. imaging along the growth directione.g. imaging along the growth direction

1.1. Section your sample into pieces of order 250Section your sample into pieces of order 250 mmthickthick

2.2. Create a 3 mm discCreate a 3 mm disc Ultrasonic cutterUltrasonic cutter -- ceramics, semiconductorsceramics, semiconductors Drill coring toolDrill coring tool -- ceramics, semiconductorsceramics, semiconductors

Or scribe to 2.8 mm x 2.8 mm square (if thin film poorlyOr scribe to 2.8 mm x 2.8 mm square (if thin film poorly

bonded)bonded)3.3. Grind to 100Grind to 100 m or som or so

4.4. DimpleDimple to 10to 10 -- 2020 mm

5.5. Ion millIon mill


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Sample preparationample preparationargon ion millingrgon ion millingControlled sputtering usingontrolled sputtering usingenergetic argon ionsnergetic argon ionsIncident at between 100Vncident at between 100Vand 6 kVnd 6 kVControl angle of incidence,ontrol angle of incidence,current and voltageurrent and voltageMaximum thinning rate ataximum thinning rate ataround 14round 14 - 1 66Final thinning done at lowerinal thinning done at lowerangles, currents andngles, currents andvoltagesoltages


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(2)2)

(1)1)(3)3)

(4)4)

(5)5)


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Sample preparationample preparationElectropolishinglectropolishing / ElectrochemicalElectrochemicalUsed to thin metals:sed to thin metals: Does not introduceDoes not introduce

deformation.deformation. A electrolytic solution isA electrolytic solution isdirected at sample. Voltagedirected at sample. Voltageacross anode / cathodeacross anode / cathode

varied.varied.A variant is used tovariant is used toprepare semiconductorsrepare semiconductors No voltage drop used, justNo voltage drop used, justan acid mixture.an acid mixture.

Excellent methods exist forExcellent methods exist forSi,Si, SiGeSiGe,, GaAsGaAs, other III, other III--VVss

Not IIINot III--NNs, thoughs, though


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Sample preparationample preparationother techniques / termsther techniques / terms

Tripod polishing:ripod polishing: Very controlled method of grinding a sample to close electronVery controlled method of grinding a sample to close electron

transparency or close, followed by ion milltransparency or close, followed by ion mill

Nanoparticlesanoparticles / Nanotubes / Nanowires:Nanotubes / Nanowires: Disperse in methanol, drop onto a thin carbon web.Disperse in methanol, drop onto a thin carbon web. Can also embed particulates in harder medium, and grind /Can also embed particulates in harder medium, and grind /

dimple / ion milldimple / ion millCleavage:leavage: Controlled fracture across a known cleavage plane.Controlled fracture across a known cleavage plane. Only effective in certain casesOnly effective in certain cases

Replica:eplica: Old techniqueOld technique Coat surface with carbon,Coat surface with carbon, sputtersputter heaveyheavey metal on to this atmetal on to this at

oblique angle, remove carbonoblique angle, remove carbon Fracture surfaces, particle countsFracture surfaces, particle counts


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Focused ion beam microscopyocused ion beam microscopyLiquid metal ion source (LMIS)iquid metal ion source (LMIS)Gaa+ ions incident on sampleons incident on sample

Causes sputteringCauses sputtering Causes, SE, BSE, SI emissionCauses, SE, BSE, SI emission

Rate of sputter proportional toate of sputter proportional tocurrenturrent Ranges from 1Ranges from 1 pApA to 20to 20 nAnA

Superb for:uperb for: Site specific preparationSite specific preparation

Cross sections & plan viewsCross sections & plan viewsofofdifficultdifficult samplessamples

Cross sectionsCross sections samples withsamples withhighly different hardness / ionhighly different hardness / ion

sputtering ratesputtering rate

FESEMFESEM

FIBFIB

FEIEI DualBeamualBeam FIB / SEMIB / SEM


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Focused ion beamocused ion beamH barbar methodethod


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Focused ion beamocused ion beamsite specific prepite specific prep


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Surface featuresurface features


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Transmission Electron Microscopy Skills:Sample preparation Lecture 7

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Transcript of Transmission Electron Microscopy Skills:Sample preparation Lecture 7