(Transmission)+Electron+Microscopy+for+Multi6Scale+

Porous+Materials++

I6+Basic+principles+and+techniques!!A.#BARONNET,#J.#BERTHONNEAU#&#O.#GRAUBY##

Aix3Marseille#Université#Centre#Interdisciplinaire#de#Nanoscience#de#

Marseille#(CINaM)#

Fourth#Winter#School#on#MulKscale#Porous#Materials#–#January,#20173Marseilles,#France##

I"–"Basic"principles"of"Transmission"Electron"Microscopy"(TEM)"#The$TEM$machine$"

#3#Of#what#it#is#made#of,#and#how#it#works##

#3#Some#aWached#techniques###Sample$prepara0on$techniques$$$Very$high9resolu0on$Imaging$and$diffrac0on$"

#Use#of#the#(Fast)#Fourier#Transform#(FFT)#in#TEM#at#very#high#resoluKon##"II"8"Some"applica:ons"of"high8resolu:on"TEM"on"non"conven:onal"minerals""

#3Ultrastructures*and*pores*down*to*the*atomic*scale##

high tension 100 – 400 Kv

vacuum 10-5 - 10-9 torr

The transmission electron microscope upside down ≈ a "light" microscope in which electrons replace photons

Varying#lens#focal#distances#

Fixed#equipment#

Fixed#lens#focal#distances#

Moving#equipment#

air*

MET 200 kV (CRMCN)MET 200 kV (CRMCN)

Complexity#due#to:#3  Bad#electron#opKcs#3  Need#of#vacuum#

#anywhere#inside#

In a TEM, you may switch immediately from

the direct space (image)

to the reciprocal space (diffraction)

objecKve#lens#

back#focal#plane#

image##plane#

incident#beam#

diffracKon#paWern#

crystal#

The#complex#electron#path#through#a#TEM#

Bigger#and#bigger?#BeWer#and#beWer?##1.25 MV HRTEM

RUCA (Anvers)

Image3corrected#300#keV#HRTEM##Aix3Marseille#Université#

Desperate#guy#(red#face))#trying#to#image#anKgorite#To#pass#through#«#thick#»#samples#

Not#suited#for#beam3sensiKve#

materials#

A LaB6tip

Electron sources and acceleration voltage

Classical tungsten filament

Cold and warm cathode field emission tip

coherent#beam#

not#so#coherent#beam#suited#for#beam3sensiKve#materials#acceleraKon#voltage#300keV#=#

best#against#beam#damages#

True#Ponctual#source#

# # #######specimen#

Secondary#e–#(std#SEM#imaging)#

BackscaWered#e–#(SEM#Z3imaging#

Electron#Back#ScaWering#DiffracKon#(EBSD))#

Incident#beam#e–#

Auger#e–#Surface#chemical#analysis#

X3rays##Energy#Dispersive#Spectroscopy#(EDS)#

Wavelength#Dispersive#Spectroscopy#(WDS)#

ElasKcally#scaWered#e–#(Selected#Area)##

Electron#DiffracKon(SAED)#Dark3Field#(DF)#imaging#

InelasKcally#scaWered#e–#

High3Angle#Annular#Dark#Field##(HAADF)#imaging#Electron#Energy##

Loss#Spectroscopy#(EELS)#UnscaWered#e–#

(transmiWed#beam)#Bright3Field#(BF)#imaging#Electron#Tomography#

Cathodaluminescence#

Material"responses"under"electrons"

300 keV

Sample

EDS (hν analysis)

X

1 µm

30 keV

Sample

Analysed zone

Detector (λ analysis)

X

Vanalyzed = 10 µm3 Vanalyzed = 10-6 µm3

Sample volumes analyzed with Electron microprobe/ TEM EDS (ATEM)

ATEM#is#a#satellite#tool#absolutely*needed#for#complex#material#studies#dealing#with#micro#to#nano#size#of#crystals#

#

QuanKtaKve#data#for#oxygen#and##above#;#Z≥#8##X3ray#energy#0320keV#

5#µm#

An ideal sample to enter the TEM should be:

:

Transparent for standard acceleration (200-300 kV) => 0 < thickness < 500 nm for oxides (silicates) HRTEM --> 5-10 nm

Manipulable (support inscribed in diam. 3 mm)

Conductive or rendered conductive by metallization => amorphous C-coating

Representative of the bulk of the materials => structures, microstructures, defects, chemical compositions,…be saved (preparation and observation)

The#criKcal#point#in#a#TEM#study:#The#sample#preparaKon#

The#thin3sample#preparaKon#techniques##Which*materials*do*you*want*to*look*at?**organic,*mineral,*hard,*so:,*coherent,*porous,*granular,*fibrous,*composite,,*hydroxylated,*hydrated,................*#*What*do*you*want*to*see*in*this*material?**

shape,*size,*crystallinity,*chemical*composi?on,*defects,*texture,*ultrastructure,*........................*

TEM#grids#and#slots#

3#mm#

conducKng:#Cu,#Ni,##Mo,#Au,.....# "bivalve"#grids#

"stadium"#slots#for#ion#thinning#

honeycomb#grid#

mesh#grids#

Where#should#I#put#the#specimen?#

+#SupporKng#

C#film#+##

amorphous#C#sample#coaKng#

slots#

EvacuaKon#of#electric#charges#=#image#stability#

The "drop deposition" technique

1 µm

3 mm

Advantages - the simplest and quickest - for powder characterization - (size, shape, diffraction, composition)

Drawbacks -not for water soluble minerals -Particle density adjustment -drift and tilt under the beam (no clean HRTEM)

- +-noise from C-film background (holey, lacey C-films- C-film wettability

Celadonite mica crystals (O. Grauby)

syntheKc#chrysoKle#charge#

Ultramicrotoming#(conKnue)#

Advantages#

#3unique#for#powders,#fibers,#synthesis#charges#

#3chemically#extremely#clean#

#3ready#for#the#TEM#

Drawbacks"

#3not#for##big#and#hard#materials#

#3sample#bent#and#cracked:#avoid##for#microstructure#and#defect##observaKons#

#3Long#training#for#embedding##samples#and#to#cut#well#

#3expensive#diamond#knives#

#3mechanical#drir#under#the#e3#beam:#not#good#for#HRTEM#

Focused#ion#beam##(FIB)#milling#

Slicing#the#nacreous#layer#of#an#oyster#shell3#O.#Grauby#

Advantages#3sample#below#a#surface#feature#ready#for#TEM#3normal#to#the#surface#3sor#and#hard,#porous#samples##drawbacks#Achemically*dirty:#Ga#&#Pt##implantaKons#3smearing#of#chemical#composiKon#3strong#structural#damages###

3#mm#

Recent#FIB#specimen#holder#

half#slot#

A$phytolithe:#a*mesoporous*material*made*of*amorphous*silica** * * *Storage*of*Si*by*plants*

Nano#pillar#

Thinned#window#

Pt#

Pt#welded# See#Jérémie#B.##to#morrow#

for#electron#tomography#of#this#slice#

From*the*rock*to*the*atomic*image*by*TEM*

The#royal#road#

the#rock#slice#

sugar#piece#

thin#secKon#

a#special#thin#secKon#

uncovered#rock#slate#double#face#1µm#polish#30850"µm3thick##Thermofusible#resin#(Lakeside,#crystalbond)##glass#plate#

Thin3secKon#facility#of#a#geological#laboratory#

300#µm#

diamond#saw##

diamond#wire#saw#

polishing#machines#

Crossed"nicols"light"microscopy"to"place"the"slots##

thin#secKon#

3 recognize#the#minerals#from#their#opKcal#properKes#(refringence#&#

3 Birefringence)#

3 crystallographic#orientaKon#with#15°#accuracy#(#for#HRTEM)#

glue#Rock#slice#

microdrilling#around#the#slot#and#melt#the#glue#underneath#(<#200°C)#

detach#with#a#twizzer#and#wash#the#glue#with#alcohol#

ready#for#the#PIPS#milling#

<#50#µm#

Glass#slide#

Araldite#film#

slot#

### Precision ion polishing system

(PIPS) Ar+ ions, 5 -->2 keV, two guns 7-4° incidence. Polishing time

0.5h to 5 days for 50µm - thick thin section

Ion#3#milling#systems#

Advantages#3large#and#thin#surfaces#to#look#at#3wedge3shaped#sample:#extra3thin#zones#3#gentle#heaKng#3high#mechanical#stability#3reasonable#damages#(amorphisaKon)#

Drawbacks#

3polluKon#by#spuWering:#grid,#specimen#holder#

3needs#to#be#trained#for#opKmum#use#

#

The#top#for#high3resoluKon#electron#microscopy#(HRTEM)##of#most#minerals#

Ultra#thin#wedge#around#the#hole#border#Only#part#suitable#for#TEM#

Around#the#hole:#hours#of#TEM#exploraKon#to#come#

1#mm#

PreparaKon#of#TEM#specimens:##The#sampling#problem:#to#be#representaKve##for#up#scaling##to#be#useful#####

"All*thinned*samples*of*the*Earth*crust*for*TEM*enter*a*thimble*while*the*crust*volume*is*roughly*75.*107*km3.*

** * *So,*be*careful*with*sampling!*“*# ## ##

# # # # #David*Veblen,*** * * * * * * *Johns*Hopkins*University,*Bal?more#

***

Electron"diffrac:on"by"crystals""The#direct#lauce#(blue)#and#the#reciprocal#lauce#(green)#A#23D#case#

HRTEM#image#

DiffracKon#paWern#

Perpendicular#rows ######## # # #Inverse#metrics#

Lauce#fringes#

Electron diffraction by crystals

Bragg's law 2d(hkl)sinθ = nλ#

and#for#high3energy#electrons:##

2d(hkl)θ ≈ nλ#

#θ#≈ < 1-2° ----->only lattice planes // to the incident beam are diffracting very thin specimen ---> elongation of reciprocal lattice nodes --->relaxation of Bragg's conditions ------> many reflections at a time

1/λ#

Slight curvature of the Ewald's sphere (R= 1/λ) intersecting the 3D arrangement of the reciprocal lattice (RL) The SAED pattern = Visualisation of sub planar sections of the reciprocal lattice Tilting the sample in diffraction mode is exploring the RL in 3-D Double tilt , high-resolution, specimen holder ± 15° Procedure of alignment of a single crystal: find a crowdy SAED, put the zero-order Laue zone(ZOLZ) perfectly symetrical around the transmitted beam by centring the first - order Laue zone (FOLZ) when visible!

ZOLZ#

FOLZ#

MicrodiffracKon#paWerns#of#some#states#of#maWer#

amorphous# polycrystalline# single#crystal#+#disorder#

cylindrical#lauce# Quasi#crystal#

seen#along#a##23fold#axis#

B.#Devouard#

Toward#very#high3resoluKon#TEM#(HRTEM)###

Introducing#Atomic#structure#images###

A biperiodic image =

discrete sum (troncated) of sine variations of fringe contrast along diffraction vectors

Amplitude

Wavelength

Phase

The Graal: the charge density projection !of the crystal structure!!In the trigonometric form:!!ρ(y,z)=∑k∑l|F0kl| cos 2π (ky + lz +α0kl)!!= |F000|!!+ |F010| cos 2π (y +α010) + |F020| cos 2π (2y+α020) +......!!+ |F001| cos 2π (z+α001) + |F002| cos 2π (2z+α002) +......!!+ |F011| cos 2π (y+z+α011) + |F022| cos 2π (2y+2z+α022) +......!

In its focal plane, the diffraction pattern of the object!!In its image plane, the microscope performs !

!a Fourier photosummation!

The#objecKve#lens#is#the#only#one#that#maWers#

Point-to-point resolutions at CINaM: 2.8 Å for 200 kV TEM

1.6Å or 2.1Å for 300kV TEM

0.5Å somewhere in the world

R (Å -1 )d (Å)

R0

résolution

sin χ

+1

-1

0

Fenêtre

0,1 0,2 0,3 0,410 5 3,3

diaphragme de contraste

dr = 0, 65λ3 / 4Cs1/ 4

Electronic image = recombination of discrete diffracted beams that keep amplitudes and phases of diffracted waves not a « shadow »

image but: dynamical diffraction + phase offsets due mainly to spherical aberration The Scherzer defocus (critical underfocusing) roughly compensate for those phase offsets within the transfer window toward the structure image

Out#of#focus#

Scherzer#defocus#

Same#thickness#

ObjecKve#Aperture##Back#focal#plane#

DiffracKon#vectors#

Wave#shir#

Correct#phases#are#essenKel#to#get#a#correct#structure#image#

00l*

02l*

04l*

06l*

000#

Recorded#Diff#paWern#

Quasi3atomic#image#of#the#bioKte#mica#seen#along#<1#0#0>#

Very#HR#numerical#scan##of#the#image#«#nuclear#»#film#circular#selecKon#

FFT#processing#(FIJI#applicaKon)#

5#nm#

FFT#now##realisKc##subsKtute#to#the#microdiffracKon#

0#2#l*0#0#l* 0#4#l*The#high3resoluKon#TEM#Image#of#a#2M1#phengite#

From#lauce#images##to#

structure#images##

Summing#up#progressively#The#Fourier#terms#

Lauce#image#

Quasi#structure#image#

Stereo#imaging####Electron#tomography#(Jérémie#B.#tomorrow)#

Toward#the#3D#view#with#a#TEM#

See#Timm*Weitkamp*wednesday#evening#

See#Jérémie*Berthonneau*tomorrow#