Unit 1 - Crystal physics
Objectives
❖ Importance of Crystals in the current world
❖To describe the arrangements in crystalline solids based on lattice,
basis, and crystal structure
❖Different crystal systems
Infromation Revolution
Electronic Numerical
Integrator and
Computer(ENIAC)
First Computer
Today
Semiconductor crystals made the possible information
Revolution today and lead to development of modern
electronic systems and devices
Crystals : germanium, silicon, gallium arsenide and many
others
Infromation Revolution
Crystals made possible the information in hand ....
Digital revolution
Information (world)
at Hand
Infromation Revolution
An example for infromation revolution ....
1990
•Cell phone subscribers: 12.5 million (0.25% of world population in 1990
•internet users: 2.8 million (0.05% of world population in 1990)
2000
Cell phone subscribers: 1.5 billion (19% of world population in 2002)
Internet users: 631 million (11% of world population in 2002)
2010
Cell phone subscribers: 4 billion (68% of world population in 2010)
Internet users: 1.8 billion (26.6% of world population in 2010)
2020
Cell phone subscribers: 4.78 billion (62% of world population in 2020)
Internet users: 4.54 billion (59% of world population in 2020)
What is the point of studying crystal physics ?
Silicon crystal ingots and
200 mm Si wafers
A multipurpose Si
Photonics Process Core
Crystals in Optics
Ruby crystal
❖ Many Crystals are
used in optical
conversions,
Lasers, Displays,
optical
communications ....
Nd- YAG crystals
Name a two crystals used in Lasers ...
Ruby laser
Nd- YAG Lasers
Crystals in Different
Fields
Industrial
communications
Telecommunications
Mobile, Radio
Aviation , Marine
Instrumentation
Computers, Disk drives
Automotive
Engine control,
sterio, clock,
GPS
Military & Aerospace
communications
Navigtion
Radar
Sensors
Electronic warfare
Research & Metrology
Atomic clocks
Instruments
Space tracking
Celestial navigation
Quatrz crystal is one of
the crystal used in the
all mentioned applications
Crystals found are Everywhere !
Some common crystals found in the human body ....
Calcium phosphate
Uric acid crystals- found in joints
Calcium oxalate crystals
Calcium carbonate crystals
What is the point of studying solid state physics ?
 Understanding the electrical properties of solids is right
at the heart of modern society and technology.
 The entire computer and electronics industry relies on
tuning of a special class of material, the semiconductor,
which lies right at the metal-insulator boundary.
 Solid state physics provide a background to understand
what goes on in metals, semiconductors and insulators
What is the point of studying solid state physics ?
 Solid state physics(SSP) is the applied physics • New
technology for the future will inevitably involve
developing and understanding new classes of
materials.
What does a crystal consist of at the microscopic
level?
(or)
How do atoms assemble into solid structures?
STRUCTURE OF ATOM
-
+++
+ +
-
-
-
Atom 1
Atom 2
Proton
Electron
Neutron
-
-
+++
+ +
- Repulsive force
-
-
-
+++
+ +
+
-
+++
+ +
-
-
Atom 3
FORCE VS DISTANCE FOR MANY ATOMS
Kasap – Principles of electronic materials
Matter
Liquid
Solid
Gas
On the basis of arrangement of atoms
Solid
Crystalline solids
Single crystalline
Amorphous solids
Polycrystalline
CRYSTALLINE SOLIDS
• The atoms or molecules are arranged in a definite, repeating pattern in three
dimension i.e., throughout the entire volume of the material
• The atoms possess perfect long range order
• Sharp melting point
• They are anisotropic
An example of long range periodic order
Single Crystal
What will be microscopic
picture ?
Single Crystal
Periodical across the entire volume
Single Crystal
Single Crystals, ideally have
a high degree of order, or
regular geometric periodicity,
throughout the entire volume
of the material
Si (110)
Polycrystalline Solids
❑ The grains are usually 100 nm - 100 microns in
diameter
❑ Polycrystals with grains that are < 100 nm in
diameter are called nanocrystallites
AMORPHOUS SOLIDS
• The atoms or molecules are not arranged in a regular pattern in three
dimension i.e., throughout the entire volume of the material
• The atoms possess perfect short range order
• No sharp melting point.
• They are isotropic.
• They don’t show all characteristics of solids.
Crystals
• The periodic array of atoms, ions, or molecules that form the solid is called
Crystal Structure
Crystal Structure = Lattice + Basis ( Motif)
• Space Lattice is a regular periodic arrangement of points in
space
• Basis is an atoms (group of atoms) placed in the points of the
space lattice
A Two-Dimensional (Bravais) Lattice with Different
Choices for the Basis
Lattice
Basis
+
Crystal
=
A Two-Dimensional (Bravais) Lattice with Different
Choices for the Basis
Lattice
Basis
+
Crystal
=
A Two-Dimensional (Bravais) Lattice with Different
Choices for the Basis
Lattice
Basis
+
Crystal
=
Unit Cell: A unit cell is the smallest portion of a crystal lattice,
which can generate the entire crystal by repetition through lattice
translations
Unit Cell: A region of space which can generate the entire cystal by
repetition through lattice translations
Unit Cell: A region of space which can generate the entire cystal by
repetition through lattice translations
Unit Cell (3D)
The unit cell is the smallest structural unit or building block that can
describe the crystal structure.
➢ Repetition of the unit cell generates the
entire crystal
FCC Unit Cell
Primitive Cell
A primitive cell of a particular crystal structure is the
smallest possible unit cell one can construct
❑ One lattice point ( one atom)
Primitive Cell: Lattice points only at the corner of the cell
Non-Primitive Cell:
Lattice points at its
corner and extra
lattice points
Parameters of a unit cell
• A unit cell is characterized by six parameters. These parameters are three
edges (a, b and c) and angles between them (α, β and γ).
• Dimensions along the edges of a unit cell is represented by a, b and c.
• Edges of unit cell may or may not be mutually perpendicular.
• The angle between b and c is represented by α, between
between a and b by γ.
by
and
Seven crystal system and
Seven crystal system and
Seven crystal system and
What different you noticed in the seven cystal system ?
Primitive Cell
Unit Cell
Seven crystal system and
Why there is only 14 Bravais lattices ?
Symmetry restricts only 14 different lattices in three dimensions
Symmetry operations : Translations, Rotation, Reflection, Inversion
Is this Scanning electron microscopic figure polycrstalline or
single crystalline ?
Zinc Oxide Semiconductor Thin film
Is this Scanning electron microscopic figure polycrstalline or
single crystalline ?
• Polycrystalline
Zinc Oxide Semiconductor Thin film