The document discusses transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). It provides an overview of these techniques, including their working principles and applications. TEM uses electron beams to image thin samples at high magnifications. HRTEM provides higher resolution imaging at the atomic scale through interference between transmitted and scattered electron beams. Examples are given of using TEM and HRTEM to characterize materials such as metal oxide nanocomposites and semiconductor quantum structures.

1. Examination Paper for Foreign Graduates
Principle & Applications of TEM & HRTEM
Student Number: LS1401202
Submitted by: Mr.Gulfam Raza
Submitted to: Prof. Lilly Dong
Abstract: Transmission Electron Microscope (TEM) is a very powerful tool for
material science. A high energy beam of electrons is shone through a very thin
sample, and the interactions between the electrons and the atoms can be used to
observe features such as the crystal structure and features in the structure like
dislocations and grain boundaries. TEM can be used to study the growth of layers,
their composition and defects in semiconductors. High Resolution Transmission
Electron Microscope (HRTEM) can be used to analyze the quality, shape, size and
density of quantum wells, wires and dots.

2. 2
TABLE of CONTENTS
Topic Number Topic Name Page Number
1 BRIEF INTRODUCTION TO MICROSCOPY
1.1 What is Microscopy?
1.2 What is Microscope?
1.3 Microscopic Terms
3-4
2 TRANSMISSION ELECTRON MICROSCOPE
(TEM)
2.1 What is TEM?
2.2 Working Principle of TEM
2.2.1 Imaging
2.2.2 Diffraction
4-6
3 APPLICATIONS OF TEM
3.1CoFe2O4:BaTiO3 Core Shell Nanocomposite
3.2 g-C3N4/TiO2 Photo Catalyst
3.3 Characterization of ZnO Nanotubes
3.4 CdSe-graphene Composites
3.5 Pr-doped ZnO Nanoparticles
6-7
4 HIGH RESOLUTION TRANSMISSION
ELECTRON MICROSCOPE
(HRTEM)
4.1 What is HRTEM?
4.2 Working Principle of HRTEM
7-9
5 APPLICATIONS OF HRTEM
5.1 CoFe2O4:BaTiO3 Core Shell Nanocomposite
5.2 Characterization of ZnO Nanotubes
9

3. 3
TOPIC No. 01
BRIEF INTRODUCTION to MICROSCOPY
1.1What is Microscopy?
The science of investigating small objects using instruments like microscope is
called microscopy.Microscopy is the technical field of using microscopes to
viewing objects and areas of objects that are not within the resolution range of the
normal eye. There are three well-known branches of microscopy;
 Optical Microscopy
 Electron Microscopy
 Scanning Probe Microscopy
On October 8, 2014, the Nobel Prize in Chemistry was awarded to Eric
Betzig, William Moerner and Stefan Hell for "the development of super-
resolved fluorescence microscopy," which brings "optical microscopy into
the nanodimension". [1]
1.2What is Microscope?
An optical instrument that uses a lens or combination of lenses to produce
magnified images of small objects especially which are too small to be seen by
naked or unaided eye.There are many types of microscopes. The most common
and the first to be invented is the optical microscope, which uses light to image the
sample. [2]
Other major types of microscopes are following;
 Electron Microscope (TEM and SEM)
 Ultra-microscope
 Scanning Probe Microscopes
1.3Microscopic Terms
Resolution
The resolution of an optical microscope is defined as the shortest distance between
two points on a specimen that can still be distinguished by the observer or camera
system as separate entities.[3]

4. 4
Magnification
Magnification in physical terms is defined as "a measure of the ability of a lens or
other optical instruments to magnify, expressed as the ratio of the size of the image
to that of the object". This means, that an object of any size is magnified to form an
enlarged image.
The magnification required to produce the visible image can be calculated using
the formula:[4]
Magnification = Image ÷ Object
Lenses
A lens is a transparent curved device that is used to refract light. A lens is usually made
from glass. There are two different shapes for lenses. They are called convex and concave.[5]
Aperture of Lense
In optics, an aperture is a hole or an opening through which light is admitted. More
specifically, the aperture of an optical system is the opening that determines the
cone angle of a bundle of rays that come to a focus in the image plane.It is crucial
in determining the resolving power of an optical devicebecause the aperture
determines the amount of diffraction and hence resolution.[6]
TOPIC No. 02
TRANSMISSION ELECTRON MICROSCOPY
2.1 What is TEM?
Transmission electron microscopy uses high energy electrons (up to 300 kV
accelerating voltage) which are accelerated to nearly the speed of light. The
electron beam behaves like a wavefront with wavelength about a million times
shorter than lightwaves.

5. 5
2.2 Working Principle
of TEM
The TEM operates on the
same basic principles as
the light microscope but
uses electrons instead of
light. When an electron
beam passes through a
thin-section specimen of
a material, electrons are
scattered. A sophisticated
system of electromagnetic
lenses focuses the
scattered electrons into an
image or a diffraction
pattern, or a nano-
analytical spectrum,
depending on the mode of
operation.
Fig 1 - General layout of a TEM describing the path of electron beam in a TEM
Fig 2 - A ray diagram for the diffraction mechanism in TEM
2.2.1Imaging
The beam of electrons from the electron gun is focused into a small, thin, coherent
beam by the use of the condenser lens. This beam is restricted by the condenser
aperture, which excludes high angle electrons. The beam then strikes the specimen
and parts of it are transmitted depending upon the thickness and electron
transparency of the specimen. This transmitted portion is focused by the objective
lens into an image on phosphor screen or charge coupled device (CCD) camera.
The image then passed down the column through the intermediate and projector
lenses, is enlarged all the way.

6. 6
The image strikes the phosphor screen and light is generated, allowing the user to
see the image.
2.2.2Diffraction
Fig 2 shows a simple sketch of the path of a beam of electrons in a TEM from just
above the specimen and down the column to the phosphor screen. As the electrons
pass through the sample, they are scattered by the electrostatic potential set up by
the constituent elements in the specimen. After passing through the specimen they
pass through the electromagnetic objective lens which focuses all the electrons
scattered from one point of the specimen into one point in the image plane. Also,
shown in fig 2 is a dotted line where the electrons scattered in the same direction
by the sample are collected into a single point. This is the back focal plane of the
objective lens and is where the diffraction pattern is formed.[7]
TOPIC No. 03
APPLICATIONS of TEM
3.1CoFe2O4:BaTiO3Core Shell Nanocomposite
The TEM image of as-synthesized CFO nanoparticles is
given as;
Figure shows nearly spherical CFO nanoparticles with
diameter 20 nm.[8]
3.2 g-C3N4/TiO2Photo Catalyst
Morphology and microstructure of samples were investigated by TEM as shown;[9]
TEM images of g-C3N4 (a), TB1 (b), TB0.5 (c), TB0.2 (d), TB0.05 (e), and TB0 (f), respectively. Redand white
arrows in image (b) showing the presence of hollowstructured TiO2 nanobox and film-like g-C3N4, respectively.

7. 7
3.3Characterization of ZnO Nanotubes
TEM micrograph indicates that the ZnO possesses uniform
nanotubes and are grown in large scale.[10]
3.4CdSe-graphene Composites
TEM images of CdSe-graphene
composite materials. From the
images, it can be observed that the
CdSe were the dark imaged
compounds almost spherical
nanoparticles attached to the surface
of the graphene sheets, whereas the
graphene components were found to
be relatively lighter than CdSe with
irregular edges, flat sheet-like
structure, having occasional distribution of CdSe on the surface.[11]
3.5Pr-doped ZnO Nanoparticles
The particles are agglomerated and the
shape of samples is turnover from
spheroid-like into the mixer of spheroid-
like and rod-like with the increase of
Prcontent, in which spheroid-like particles
are dominant.[12]
TOPIC No. 04
HIGH RESOLUTION TRANSMISSION ELECTRON
MICROSCOPE
4.1 What is HRTEM?
High-Resolution TEM (HRTEM) is the ultimate tool in imaging defects. In
favorable cases it shows directly a two dimensional projection of the crystal with
defects and all.

8. 8
Of course, this only makes sense if the two-dimensional projection is down some
low-index direction, so atoms are exactly on top of each other.[13-14-15]
4.2 Working Principle of HRTEM
The basic principle involved in the image formation in both the microscopes (TEM
& HRTEM) is similar. However, HRTEM provides high resolution images at
atomic scale level.
Most precisely, HRTEM is a type of TEM.
The high-resolution transmission electron microscopy (HRTEM) uses both the
transmitted and the scattered
beams to create an interference
image. It is a phase contrast
image and can be as small as the
unit cell of crystal. In this case,
the outgoing modulated electron
waves at very low angles
interfere with itself during
propagation through the objective
lens. All electrons emerging from
the specimen are combined at a
point in the image plane.
In short, following are the salient
features to describe working
principle of HRTEM;
 Consider a very thin slice of crystal that has been tilted so that a low-index
direction is exactly perpendicular to the electron beam. All lattice planes
about parallel to the electron beam will be close enough to the Bragg
position and will diffract the primary beam.
 The diffraction pattern is the Fourier Transform of the periodic potential for
the electrons in two dimensions. In the objective lens all diffracted beams
and the primary beam are brought together again; their interference provides
a back-transformation and leads to an enlarged picture of the periodic
potential.

9. 9
 This picture is magnified by the following electron-optical system and
finally seen on the screen at magnifications of typically 106
.[13-14-15]
TOPIC No. 05
APPLICATIONS of HRTEM
5.1CoFe2O4:BaTiO3Core Shell Nanocomposite
High Resolution Transmission Electron Microscope images confirm the core shell
structure.The CFO: BTO core shell nanoparticles are shown as;
Figure shows the core shell nanoparticles of CFO: BTO. Two crystallographic
phases are evident and were identified by measuring the interplanar spacings, d, of
an enlarged image.[8]
5.2Characterization of ZnO Nanotubes
Structural properties of the as-synthesized ZnO nanotubes were done by HRTEM.[10]

10. 10
References
1: http://en.wikipedia.org/wiki/Microscope
2: http://www.thefreedictionary.com/microscope
3: http://www.microscopyu.com/articles/formulas/formulasresolution.html
4: http://www.wikilectures.eu/index.php/Magnification_of_optical_microscope
5: http://www.gcsescience.com/pwav24.htm
6: https://answers.yahoo.com/question/index?qid=20080516234223AA7QV11
7:http://www2.warwick.ac.uk/fac/sci/physics/current/postgraduate/regs/mpags/ex5/techniques/structural/tem/ ,
http://portal.tugraz.at/portal/page/portal/felmi/research/TEM%20and%20Nanoanalysis/Principles%20of%20TEM
8: http://www.sciencedirect.com/science/article/pii/S0304885314010658#(Paper had been accepted at
October 27, 2014)
9: http://www.sciencedirect.com/science/article/pii/S0926337314005773#(Paper had been accepted at
September 21, 2014)
10:http://www.sciencedirect.com/science/article/pii/S1386142514011809# (Paper had been accepted at
July 29, 2014)
11:http://www.tandfonline.com/doi/abs/10.1080/1536383X.2014.885954#.VKjpr8lYi-U (Paper had been
accepted at January 17, 2014)
12:http://www.sciencedirect.com/science/article/pii/S0925838814023913# (Paper had been accepted at
September 26, 2014)
13-14-15:http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_6/backbone/r6_3_4.pdf
http://www.researchgate.net/post/What_is_the_difference_between_TEM_and_HRTEM
https://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0CE
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