SCANNING ELECTRON MICROSCOPE AND FIELD EMISSION SCANNING ELECTRON MICROSCOPY

1. SCANNING ELECTRON MICROSCOPE
(SEM)

3. Laboratory Apparatus

4. Links:
https://myscope.training/SEM_simulator.html
https://myscope.training/#
photogrammetry (using MountainsSEM software)
Virtual Laboratory

5. Links:
https://electron-flight-simulator-demo.software.informer.com/download/
Utilizing Monte Carlo Modeling of electron trajectories Electron Flight Simulator is a software tool desig
ned to make your job easier. It can help you understand difficult samples, show the best way to run an analy
sis, and help explain results to others.
Virtual Laboratory

7. HISTORY
 The scanning electron microscope (SEM) was invented by Max Knoll in 1935,
at the Telefunken Company in Berlin, for studying the secondary emission proper
ties of television camera tube targets.
 The first attempt at building a scanning microscope with a sub-micrometre probe
was made in 1937 by Manfred von Ardenne in his private laboratory, also in Be
rlin.
 Further developed by Prof. Sir Charles Oatley and his student Gary Stewart
and first time marketed by Cambridge Scientific Instrument Company as the
"Stereoscan" in 1965.

8. What is SEM?
•SEM = scanning electron microscope
•A scanning electron microscope (SEM) is a type of electron microscope that produ
ces images of a sample by scanning the surface with a focused beam of electrons. T
he electrons interact with atoms in the sample, producing various signals that contai
n information about the surface topography and composition of the sample.

9. SCANNING ELECTRON MICROSCOPE
PRINCIPLE
The basic principle is that a beam of electrons is generated by a suitable source.
typically a tungsten filament or a field emission gun.
The electron beam is accelerated through a high voltage (e.g.: 20 kV) and pass
through a system of apertures and electromagnetic lenses to produce a thin beam of
electrons.
Then the beam scans the surface of the specimen. Electrons are emitted from the
specimen by the action of the scanning beam and collected by a suitably-positioned
detector.

10. SCANNING ELECTRON MICROSCOPE
BASIC COMPONENTS
Electronıc console
Electron gun
Electromagnetic lenses
Scanning Coils
Detectors
Sample stage
Vacuum system

11. BASIC COMPONENTS

12. BASIC COMPONENTS
Electronıc console
•Focus, Magnification, Brightness, Contrast
Electron gun is used for producing an intense beam of electron.
Thermionic gun  thermal energy
Field emission gun  electric field
Electromagnetic lenses
LENSES is used to produce clear and Detail images.
Condenser lens  reduces the diameter of the electron beam
Objective lens  focuses electron beam

13. BASIC COMPONENTS
Scanning Coils
After the beam is focused, scanning coils are used to deflect
the beam in the X and Y axes so that it scans in a raster fashi
on over the surface of the sample.
Sample stage
The container at the end of the column is called the Sample
Chamber. The sample stage and the electron detector sit in h
ere.
Detectors
When the electron beam interacts with a sample in a scannin
g electron microscope (SEM), multiple events happen. In ge
neral, different detectors are needed to distinguish secondar
y electrons, backscattered electrons, or characteristic x-rays.

14. VACUUM CHAMBER
SEMs require a vacuum to operate.
Without a vacuum, the electron beam generated by the electron gun would
encounter constant interference from air particles in the atmosphere.
Not only would these particles block the path of the electron beam, they would also
be knocked out of the air and onto the specimen. which would distort the surface of
the specimen.
Continue…..

15. HOW THE SEM WORKS
 The SEM uses electrons instead of light to form an image.
 A beam of electrons is produced at the top of the microscope by heating of a metallic filament.
 The electron beam follows a vertical path through the column of the microscope. It makes its w
ay through electromagnetic lenses which focus and direct the beam down towards the sample.
 Once it hits the sample, other electrons ( backscattered or secondary) are ejected from the sampl
e.
 Detectors collect the secondary or backscattered electrons, and convert them to a signal that is s
ent to a viewing screen similar to the one in an ordinary television, producing an image.

16. Diagrams

17. Working Diagrams

18. CHEMICAL ANALYSIS!
Chemical analysis with a scanning electron microscope and it works like
this when the fast electrons of the electron beam the primary electrons reach the
surface they knock out electrons of the specimen material these are the secondary
electrons used for image formation what happens in detail shows a schematically
drawn atom from near the surface just like any other atom it consists of a positively
charged nucleus and negatively charged electrons
the electrons stay in energetically well defined shells around the nucleus
a primary electron comes from above and accidentally knocks out an electron from
the K shell of the sample atom a vacant place remains as indicated by the yellow
circle this state is unstable an electron from the L shell fills the gap and the energy
difference is released in the form of a characteristic x-ray photon this x-ray photon
is called characteristic because its energy is quite characteristic or typical for the
particular element now another transition follows and finally the atom repairs itself
with an electron from the vicinity a free electron so x-ray
radiation is generated during the operation of the scanning electron

19. microscope namely X radiation which is characteristic for the chemical elements
present in the sample if the energy and the intensity of the radiation are
measured with an x-ray detector then the chemical composition of the sample
can be determined here the typical x-ray spectrum of the piece of jewelry builds
up chemical analysis is then carried out using sophisticated methods with the
help of a computer certain limitations must indeed be minded but it's
definitely a fine method and above all it is completely non-destructive and
even very small spots on a sample can be analyzed and what has happened to the
small cobalt plate which was one of the samples it was used to calibrate the
measurement this means to adjust it finally the chemical analysis is finished now
a piece of jewelry is genuine the gold content amounts to about 70% the balance
is silver and copper.
Continue…..

20. Images Taken by SEM!
Scanning electron micrograph of the eggs of a European
cabbage butterfly (Pieris rapae).

21. A video illustrating a typical practical magnification range of a scanning electron microscope designe
d for biological specimens. The video starts at 25×, about 6 mm across the whole field of view, and zo
oms in to 12000×, about 12 μm across the whole field of view. The spherical objects are glass beads w
ith a diameter of 10 μm, similar in diameter to a red blood cell.

22. Advantages Disadvantages
Advantages of a Scanning Electron Microscop
e include its wide-array of applications, the de
tailed three-dimensional and topographical im
aging and the versatile information garnered f
rom different detectors.
The disadvantages of a Scanning Electron Mi
croscope start with the size and cost.
SEMs are also easy to operate with the proper
training and advances in computer technology
and associated software make operation user-f
riendly.
SEMs are expensive, large and must be house
d in an area free of any possible electric, mag
netic or vibration interference.
• Although all samples must be prepared befor
e placed in the vacuum chamber, most SEM s
amples require minimal preparation actions.
Maintenance involves keeping a steady voltag
e, currents to electromagnetic coils and circula
tion of cool water.
SEMs are limited to solid, inorganic samples s
mall enough to fit inside the vacuum chamber
that can handle moderate vacuum pressure.
Advantages and Disadvantages

23. SEMs have a variety of applications in a number of scientific and industry-
related fields, especially where characterizations of solid materials is beneficial.
 In addition to topographical. morphological and compositional information, a
Scanning Electron Microscope can detect and analyze surface fractures, provide
information in microstructures, examine surface contaminations, reveal spatial
variations in chemical compositions, provide qualitative chemical analyses and
identify crystalline structures.
In addition, SEMs have practical industrial and technological applications
such as semiconductor inspection, production line of miniscule products and
assembly of microchips for computers.
SEMs can be as essential research tool in fields such as lift science, biology,
gemology, medical and forensic science, metallurgy.
Applications

24. FIELD EMISSION SCANNING ELECTRON
MICROSCOPY
(FESEM)

25. Laboratory Apparatus

26.  FESEM is the abbreviation of Field Emission Scanning Electron Microscope. A FESEM is microscope
that works with electrons (particles with a negative charge) instead of light. These electrons are liberate
d by a field emission source. The object is scanned by electrons according to a zig-zag pattern.
 A FESEM is used to visualize very small topographic details on the surface or entire or fractioned obje
cts. Researchers in biology, chemistry and physics apply this technique to observe structures that may b
e as small as 1 nanometer (= billion of a millimeter). The FESEM may be employed for example to stu
dy organelles and DNA material in cells, synthetically polymers, and coatings on microchips. The micr
oscope that has served as an example for the virtual FESEM is a Jeol 6330 that is coupled to a special f
reeze-fracturing device.
What is difference between Fesem and SEM?
Field emission scanning electron microscopy (FESEM) provides topographical and elemental information at magni
fications of 10x to 300,000x, with virtually unlimited depth of field. Compared with convention scanning electron
microscopy (SEM), field emission SEM (FESEM) produces clearer, less electrostatically distorted images with spa
tial resolution down to 1 1/2 nanometers – three to six times better.
INTRODUCTION

27. Overview of the FESEM system
CONTINUE…..

28. CONTINUE…..

29. CONTINUE…..

30. Advantages of FESEM
• The ability to examine smaller-area contamination spots at electron accelerating voltages compatible wi
th energy dispersive spectroscopy (EDS).
• Reduced penetration of low-kinetic-energy electrons probes closer to the immediate material surface.
• High-quality, low-voltage images with negligible electrical charging of samples (accelerating voltages r
anging from 0.5 to 30 kilovolts).
• Essentially no need for placing conducting coatings on insulating materials. For ultra-high-magnificatio
n imaging, we use in-lens FESEM.
Applications of FESEM
• Semiconductor device cross section analyses for gate widths, gate oxides, film thicknesses, and constru
ction details
• Advanced coating thickness and structure uniformity determination
• Small contamination feature geometry and elemental composition measurement
CONTINUE…..

31. THANK YOU