konsep dasar sem

7/26/2019 Konsep Dasar SEM

http://slidepdf.com/reader/full/konsep-dasar-sem 1/29

Sintesissolid state reaction, sol gel, vacuum system,

chemical reaction

Perlakuan

Karakterisasi

SEM: morfologi, struktur kristal, cacatkristal, deformasi, grain growth, crystalgrowth, dll



Scanning Electron Microscope



Bagian-agian SEM



Skema SEM



!eneral "ses:#Mengamati permukaan pada M$ %&-%&&&&& ',resolusi permukaan hingga kedalaman (-%&& nm

#)paila ditamahkan dengan detektorbackscattered , SEM erfungsi untuk:*%+mengamati grain oundaries pada sampel tanpa

etsa *+pengamatan daerah domain pada materialferromagnetic, *(+evaluasi orientasi kristalografigrain dengan diameter -%& µm, *.+pengamatanfasa lain akiat adanya peredaan rerata grain



E/amples of )plication

# Pengamatan permukaan dengan peresaran diatas

peresaran mikroskop optik

# Pengamatan fracture surfaces dan peredaankedalaman permukaan akiat etsa

# Penentuan orientasi kristalografi akiat preparasisurface, individual grain, fasa presipitat dandendrite



# 0dentifikasi elemen kimia dalam ukuran mikron pada ulk sample,eg inclusi, fasa presipitate

# Evaluasi gradien komposisi kimia pada

permukaan ulk sample

# Pengamatan pada semikonduktor devices untukfailure analysis, function control dan verifikasi

desain

E/amples of )plication



Sampel# 1orm solid ataupun li2uid dengan tekanan rendah*3%&-( torr

atau &4%( Pa+

# Si5e: diatasi oleh kemampuan masing-masing peralatan iasanya sample dengan luasan %6-& cm atau ukuran .-7cm masih mungkin diamati dengan SEM

# Preparation: standar metalografi erupa teknik polishing danetsa yang erlaku untuk material konduktif4 "ntuk materialnon-konduktif iasanya di-coating dengan lapisan tipiscaron, gold atau gold alloy hingga ketealan lapisan .&&84Sampel harus terhuung dengan holder iasanya digunakan pasta perak4 Sample harus tereas dari uap air, ahan pengotor organik dan minyak



9apailities of related echni2ues

# '-ray ;iffraction: menyediakan informasikristalografi# Mikroskop <ptik: memerikan informasi

awal keadaan permukaan sampel

# ransmission electron microscopy:memerikan informasi keadaan materialsecara spesifik dislokasi, small angle

oundari distriution and vacancy cluster4



Kategori komponen dalam mikroskop elektron

%4 Electron column

4 Specimen chamer

(4 =acuum pumping system

.4 Electronic control and imaging system



Electron Source *!">+



) hermionic Electron !un functions in the following manner

%4 )n positive electrical potential is applied to the anode

4 he filament *cathode+ is heated until a stream of electrons is produced

(4 he electrons are then accelerated y the positive potential down the column

.4 ) negative electrical potential *?6&& =+ is applied to the @henelt 9ap

64 )s the electrons move toward the anode any ones emitted from the filamentAs side are repelled y the @henelt 9ap toward the optic a/is *hori5ontal center+

4 ) collection of electrons occurs in the space etween the filament tip and @henelt 9ap4 his collection is called a space charge

C4 hose electrons at the ottom of the space charge *nearest to the anode+ can e/it the gun area through the small *D% mm+ hole in the @henelt 9ap

74 hese electrons then move down the column to e later used in imaging



Parameter elektron gun

Brightness, β yang menunukkan fungsimaterial filamen, suhu operasi dan tegangan4

FaBB adalah material dengan nilai β tertinggi

dimana nilainya %&-& ' lipat diandingtungsten

( ) ( ) ( )( )--.G ood I

solidangleareacurrent

πα π β ==



# he Broers design utili5es a tungstencoil wrapped around the pointed endof a long *around cm+ FaB rod4his design uses the heat radiationand electron omardment from the

tungsten coil to heat the very end ofthe tip4 he conduction of heatthrough the cathode holder, locatedat the other end of the rod, helps tolessen the prolems of the reactivityof the material4

# =ogel proposed a short FaB rodheated directly y passing a currentthrough the FaB rod, perpendicularto the length of the rod4 his isaccomplished y using rigidelectrical connectors that also

provide the support for the rod4# 0n the design of 1erris et al.C, a short

FaB rod is supported y a rion orstrip through which an electricalcurrent is passed for heating4 he rod

is heated y conduction from therion4



Specimen 0nteraction



Backscattered Electrons:

Formation

9aused y an incident electron colliding with an atom in the specimen which isnearly normal to the incidentAs path4 he incident electron is then scatteredHackwardH %7& degrees4

Utilization he production of ackscattered electrons varies directly with the specimenAs atomicnumer4 his differing production rates causes higher atomic numer elements toappear righter than lower atomic numer elements4 his interaction is utili5ed todifferentiate parts of the specimen that have different average atomic numer4 )ne/ample is shown in the SEM output section, specifically the mechanically alloyedspecimen micrograph



Secondary Electrons:

Source

9aused y an incident electron passing HnearH an atom in the specimen, nearenough to impart some of its energy to a lower energy electron *usually in the K-shell+4 his causes a slight energy loss and path change in the incident electron andthe ioni5ation of the electron in the specimen atom4 his ioni5ed electron thenleaves the atom with a very small kinetic energy *6e=+ and is then termed aHsecondary electronH4 Each incident electron can produce several secondaryelectrons4Utilization

Production of secondary electrons is very topography related4 ;ue to their lowenergy, 6e=, only secondaries that are very near the surface *D%&nm+ can e/it thesample and e e/amined4 )ny changes in topography in the sample that are larger

than this sampling depth will change the yield of secondaries due to collectionefficiencies4 9ollection of these electrons is aided y using a HcollectorH inconunction with the secondary electron detector4 he collector is a grid or meshwith a I%&&= potential applied to it which is placed in front of the detector,attracting the negatively charged secondary electrons to it which then pass through

the grid-holes and into the detector to e counted4

http://www.unl.edu/CMRAcfem/glossary.htm






Auger Electrons

Source

9aused y the de-energi5ation of the specimen atom after a secondary electron is produced4 Since a lower *usually K-shell+ electron was emitted from the atomduring the secondary electron process an inner *lower energy+ shell now has avacancy4 ) higher energy electron from the same atom can HfallH to a lowerenergy, filling the vacancy4 his creates and energy surplus in the atom which can

e corrected y emitting an outer *lower energy+ electron an )uger Electron4Utilization

)uger Electrons have a characteristic energy, uni2ue to each element from whichit was emitted from4 hese electrons are collected and sorted according to energyto give compositional information aout the specimen4 Since )uger Electrons

have relatively low energy they are only emitted from the ulk specimen from adepth of D(



X-rays

Source

9aused y the de-energi5ation of the specimen atom after a secondary electron is produced4 Since a lower *usually K-shell+ electron was emitted from the atomduring the secondary electron process an inner *lower energy+ shell now has avacancy4 ) higher energy electron can HfallH into the lower energy shell, filling thevacancy4 )s the electron HfallsH it emits energy, usually '-rays to alance the total

energy of the atom so it 4Utilization

'-rays or Fight emitted from the atom will have a characteristic energy which isuni2ue to the element from which it originated4 hese signals are collected andsorted according to energy to yield micrometer diameter+ of ulk specimens

limiting the point-to-point comparisons availale





Thin Specimen Interactions

"nscattered Electrons

Source 0ncident electrons which are transmitted through the thin specimen without anyinteraction occurring inside the specimen4

Utilization he transmission of unscattered electrons is inversely proportional to thespecimen thickness4 )reas of the specimen that are thicker will have fewertransmitted unscattered electrons and so will appear darker, conversely thethinner areas will have more transmitted and thus will appear lighter4



Elasticity Scattered electrons

Source

0ncident electrons that are scattered *deflected from their original path+ y atoms inthe specimen in an elastic fashion *no loss of energy+4 hese scattered electrons arethen transmitted through the remaining portions of the specimen4

Utilization

)ll electrons follow BraggAs Faw and thus are scattered according to@avelength$JSpace etween the atoms in the specimenJsin*angle of scattering+4)ll incident electrons have the same energy*thus wavelength+ and enter thespecimen normal to its surface4 )ll incidents that are scattered y the same atomicspacing will e scattered y the same angle4 hese Hsimilar angleH scatteredelectrons can e collated using magnetic lenses to form a pattern of spots each spot

corresponding to a specific atomic spacing *a plane+4 his pattern can then yieldinformation aout the orientation, atomic arrangements and phases present in thearea eing e/amined4



Inelastically Scattered Electrons

Source

0ncident electrons that interact with specimen atoms in a inelastic fashion, loosingenergy during the interaction4 hese electrons are then transmitted trough the rest ofthe specimen

Utilization 0nelasticaly scattered electrons can e utili5ed two ways

#Electron Energy Foss Spectroscopy: he inelastic loss of energy y theincident electrons is characteristic of the elements that were interacted with4hese energies are uni2ue to each onding state of each element and thus can eused to e/tract oth compositional and onding *i4e4 o/idation state+information on the specimen region eing e/amined4

#Kakuchi Bands: Bands of alternating light and dark lines that are formed yinelastic scattering interactions that are related to atomic spacings in thespecimen4 hese ands can e either measured *their width is inversely proportional to atomic spacing+ or HfollowedH like a roadmap to the HrealHelasticity scattered electron pattern4



Pemasangan detektor

This is an image of the broken surface

of a piece of metal, formed using

secondary electron imaging

This is a picture taken inside the samplechamber. On the left of the secondary

detector is the lens, on the right is the

backscatter detector.



Pemasangan detektor

On the far left of the backscatter

detector is the lens, in the center is the

secondary detector. To collect

electrons, the backscatter detector

moves under the lens so the electron

beam can travel through the hole in itscenter.

This is an image of an aluminum copper

alloy formed using backscattered

electron imaging. The light area is

mostly copper and the dark area is

mostly aluminum.



Keseluruhan detektor pada SEM



Sistem ;etektor # ;etektor Secondary Electron *SE+ untuk menghasilkan

gamar analisis struktur mikro, analisis produk korosi,

patahan, kegagalan material# ;etektor Backscattered Electron *BSE+ untuk menghasilkan

gamar topografi peta struktur mikro yang gamarnyadientuk dari peredaan nomor atomGdensitas yang dikandungoleh ahan4 ;aerah cuplikan dengan nomer atom yang leihtinggi akan terlihat relatif leih terang daripada daerah dengannomer atom rendah

# ;etektor sinar-/ *SiFi+ dan E;'GE;S untuk analisiskomposisi unsur yang terkandung dalam orde micrometer dan

pemetaan *distriusi unsur+ dalam suatu ahan

SKEM) M09<S9<P EFE9<>



SKEM) M09<S9<P EFE9<>

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