SEMSEM(SCANNING ELECTRON MICROSCOPE)(SCANNING ELECTRON MICROSCOPE)

20823856 Özgen Buğdaycı20823856 Özgen Buğdaycı

20824336 Elif Topçuoğlu20824336 Elif Topçuoğlu

20823985 Yavuz Duran20823985 Yavuz Duran

Hacettepe UniversityHacettepe University 12.04.201212.04.2012

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OUTLINEOUTLINE

Definiton of scanning electron microscopeDefiniton of scanning electron microscopeHistoryHistoryUsage AreaUsage AreaInstrumentationInstrumentationSample preparationSample preparationWorking principlesWorking principlesLimitationsLimitationsAdvantages & disadvantagesAdvantages & disadvantagesConclusionConclusion

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What is SEM?What is SEM?

SEM = Scanning Electron SEM = Scanning Electron MicroscopeMicroscope

Is a type of electron Is a type of electron microscope.microscope.

Uses a focused beam of high-Uses a focused beam of high-energy electrons to generate a energy electrons to generate a variety of signals at the surface variety of signals at the surface of solid specimens. of solid specimens.

Scanning electron microscope - www.directindustry.com

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HISTORYHISTORY

The first SEM image was The first SEM image was obtained by Max Knoll in 1935.obtained by Max Knoll in 1935.

Further pioneering work on SEM Further pioneering work on SEM was performed by Manfred von was performed by Manfred von Ardenne (1937)Ardenne (1937)

Further developed by Prof. Sir Further developed by Prof. Sir Charles Oatley and his student Charles Oatley and his student Gary Stewart and first time Gary Stewart and first time marketed by Cambridge marketed by Cambridge Scientific Instrument Company Scientific Instrument Company in 1965.in 1965.  first successful SEM – www.science.howstuffworks.com

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USAGE AREAUSAGE AREA

MorphologyMorphology

TopologyTopology

Microstructure studiesMicrostructure studies

Solid state physicSolid state physic

GeologyGeology

BiologyBiology

microstructure of a 15Mo3 steel - emeraldinsight.com

diamond-crystal structure - worldscheaper.com

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SEMSEM

ELECTRONIC CONSOLEELECTRONIC CONSOLE

ffocusocus mmagnificationagnification bbrightnessrightness ccontrastontrast

Console of SEM - www.chems.msu.edu

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SEMSEM

ELECTRONIC ELECTRONIC COLUMNCOLUMN

generated under generated under vacuumvacuum

focused to a small focused to a small diameterdiameter

scanned across the scanned across the surface of a specimensurface of a specimen

.

Electronic column of SEM - www.chems.msu.eduElectronic column of SEM - www.chems.msu.edu

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INSTRUMENTATIONINSTRUMENTATION

COMPONENTSCOMPONENTS

Electron gunElectron gun

Electromagnetic Electromagnetic lenseslenses

ScanningScanning

DetectorsDetectors

Sample stageSample stage

Vacuum systemVacuum system

Components of SEM - www.purdue.edu

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INSTRUMENTATIONINSTRUMENTATIONELECTRON GUN;ELECTRON GUN;

is used for producing an intense beam of electronis used for producing an intense beam of electron Thermionic gun Thermionic gun thermal energy thermal energy Field emission gun Field emission gun electric field electric field

ANODE;ANODE;

accelarates the accelarates the free electronsfree electrons

Electron gun - academic.udayton.edu

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INSTRUMENTATIONINSTRUMENTATION

LENSES;LENSES;

is used to produce clear and is used to produce clear and

detail imagesdetail images

Condenser lens Condenser lens reduces the reduces the diameter of the electron beamdiameter of the electron beam

Objective lens Objective lens focuses electron focuses electron beambeam

Lens - ammrf.org.au

Working principle of the lens - ammrf.org.au

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INSTRUMENTATIONINSTRUMENTATION

SCANNING COILSSCANNING COILS

are used to raster the are used to raster the beam across the sample beam across the sample surfacesurface

are able to move the are able to move the beambeam

Scanning coils - freudlabs.com

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INSTRUMENTATIONINSTRUMENTATIONSAMPLE CHAMBERSAMPLE CHAMBER

is where the sample is placedis where the sample is placed

can manipulate and move the can manipulate and move the

samplesample

DETECTORSDETECTORS

is used the detect the secondary is used the detect the secondary and backscattered electrons and backscattered electrons

Sample chamber - jenkins.ucdavis.edu

Detector - www.geos.ed.ac.uk

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INSTRUMENTATIONINSTRUMENTATIONVACUUM CHAMBERVACUUM CHAMBER

Absence of vacuum chamber;Absence of vacuum chamber;

electron gun’s filament would electron gun’s filament would be damagedbe damaged

other gas molecules would other gas molecules would cause collisions with electronscause collisions with electrons

sample would react with gasessample would react with gases

Electron column - iaszoology.com

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SAMPLE PREPARATIONSAMPLE PREPARATION

For organic materialsFor organic materials;;fixation fixation to preserve structure to preserve structure

drying drying moisture must be removed moisture must be removed

coating coating to conductive the sample to conductive the sample A spider coated with Au - thenallyblog.com

Preparation - www.mos.org

For metals;For metals; no need for preparationno need for preparation

For non-metallics;For non-metallics; need to be coatedneed to be coated

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SAMPLE PREPARATIONSAMPLE PREPARATION

SPUTTER COATING;SPUTTER COATING;

Makes non metallic Makes non metallic samples conductivesamples conductive

Uses Ar and electric Uses Ar and electric field to tear off metal field to tear off metal from cathodefrom cathode

Metal fall onto sample Metal fall onto sample and coat the materialand coat the material

Sputter coating device - microscopy.ca

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SAMPLE PREPARATIONSAMPLE PREPARATIONThe coating material;The coating material;

commonly carbon, gold, or some other metal or commonly carbon, gold, or some other metal or alloyalloy carbon carbon elemental analysis elemental analysis metal coatings metal coatings high resolution imaging high resolution imaging

applicationsapplications

must be vacuum compatiblemust be vacuum compatible

dependent on material properties (beam dependent on material properties (beam sensitivity,sensitivity,

hardness, etc.)hardness, etc.)

must be appropriate thicknessmust be appropriate thickness

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WORKING PRINCIPLEWORKING PRINCIPLEBeam is;generated by electron gungenerated by electron guncollimated and focused by collimated and focused by lenseslensesrastered across the rastered across the sample surfacesample surface

Secondary or Secondary or backscattered backscattered electrons are;electrons are;collected by detectorcollected by detectorformed the specimen formed the specimen image in the microscopeimage in the microscope

Working principle - ammrf.org.au

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LIMITATIONSLIMITATIONS

Samples must be solidSamples must be solid

Size of analyte Size of analyte vertically vertically <40mm <40mmhorizontally horizontally <100mm <100mm

Stable in a vacuumStable in a vacuum

Designed to prevent any electrical and magnetic Designed to prevent any electrical and magnetic interferenceinterference

Can not detect low elements (Lighter than Na-11) like most Can not detect low elements (Lighter than Na-11) like most of analys microscopyof analys microscopy

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ADVANTAGESADVANTAGES

High resolution and magnificationHigh resolution and magnification

3-D Topographical imaging3-D Topographical imaging

Compatible with PC technologies Compatible with PC technologies and softwaresand softwares

Fast AnalysingFast Analysing

Store data in digital formStore data in digital form

Easier sample preparation Easier sample preparation techniquestechniques

A peacock’s head front wiev - www.nanosmo.com

SEM adapted with pc equipments - www.lnnano.org

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DISADVANTAGESDISADVANTAGES

Can not analys fluid or gas compoundsCan not analys fluid or gas compounds

Expensive InstrumentationExpensive Instrumentation

Wasting time on sample preparationWasting time on sample preparation

Constant voltage during analysingConstant voltage during analysing

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RESULTRESULT

SEM uses electrons instead of light to form an SEM uses electrons instead of light to form an image.image.

developed new areas of study & still helping.developed new areas of study & still helping.

popular among researchers due to their wide popular among researchers due to their wide range of applications range of applications

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CONCLUSIONCONCLUSION

SEM;SEM;provides detailed surface data of solid samplesprovides detailed surface data of solid samples

informs external morphology, chemical informs external morphology, chemical composition, crystalline structurecomposition, crystalline structure

SAMPLE;SAMPLE;must be prepared before placedmust be prepared before placed

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REFERENCESREFERENCES

www.iaszoology.com/semwww.iaszoology.com/sem

www.phy.cuhk.edu.hkwww.phy.cuhk.edu.hk

www.fy.chalmers.se/microscopywww.fy.chalmers.se/microscopy

www.materials.ac.ukwww.materials.ac.uk

www.microscopemaster.comwww.microscopemaster.com

Thanks for your attentionThanks for your attention

Any Questions?Any Questions?