纳米材料学_14IC
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The level filled by the last electron is known as Fermi level and the corresponding energy is known as Fermi Energy
Fermi Energy
Energy Bands
Energy Band and Conductor
What is an insulator?
+
_
Ba tte ry
Sa m p le
What is a semiconductor?
+
_
B a tte ry
S a m p le
+
_
B a tte ry
_
+
S a m p le
From Energy Levels to Energy Bands
When atoms get together to form the various crystal structures, what happen to the quantized energy levels?
In a metal, electron can lower its energy by moving towards the positive terminal. This accounts for the conduction of electricity when an electric potential is applied.
As the electron moves along in a material, it collides with the vibrating ions in the lattice will scatter the electron from its path. This gives rise to electrical resistance.
Filling Up The Energy Band
Electrons will filled up the energy bands starting from the lowest level and then move on to the higher energy band according to Pauli’s Exclusion Principle.
p-n junction
Energy Band and conduction of electricity
What is a conductor?
+
_
Ba tte ry
_
+
Sa m p le
Structure of Metal
++++ +++
++++
Delocalized Electrons
Free to move around in the sample and hence can take part in electrical conduction
When many many atoms get together, the multiple closely spaced level become so close that one finds an energy band instead.
One Atom
Many Atoms
……..
Energy Levels
No state here
Lower energy state all filled up
Unoccupied States Fermi Energy
Occupied States
When we applied potential (Conductor)
En e rg y
Electron at higher energy state
Electron at Lower energy state
Conductor: Resistance Vs Temperature
Slope of this line is V/I = R, Resistance of the material
V
Resistance (R)
High Temperature
Low Temperature I
Temperature (T)
One Atom
Two Atoms
Energy Levels
From Energy Levels to Energy Band
Each energy level splits into many closely spaced levels.
Energy Levels
From Energy Levels to Energy Band
Current vs Applied Potential (Conductor)
Voltage (V)
Slope of this line is V/I = R, Resistance of the material (Ohm’s Law)
Current (I)
The Idea of Electrical Resistance
Energy Band and Insulator
Energy Gap
Unoccupied States Fermi Energy
Occupied States
百度文库
Energy
When we applied potential (Insulator)
In an insulator, electron cannot move to a lower energy state as all the states are occupied and Pauli’s exclusion principle prevent the electron to occupy the same state. Hence no current flow.
Introduction to the Nanoworld
A Journey into the Integrated Circuits
Lecture Outline
Introduction
Conductor, Insulator, Semiconductor
Different Types of Semiconductors
Fermi Energy
Energy Bands
Energy Band and Conductor
What is an insulator?
+
_
Ba tte ry
Sa m p le
What is a semiconductor?
+
_
B a tte ry
S a m p le
+
_
B a tte ry
_
+
S a m p le
From Energy Levels to Energy Bands
When atoms get together to form the various crystal structures, what happen to the quantized energy levels?
In a metal, electron can lower its energy by moving towards the positive terminal. This accounts for the conduction of electricity when an electric potential is applied.
As the electron moves along in a material, it collides with the vibrating ions in the lattice will scatter the electron from its path. This gives rise to electrical resistance.
Filling Up The Energy Band
Electrons will filled up the energy bands starting from the lowest level and then move on to the higher energy band according to Pauli’s Exclusion Principle.
p-n junction
Energy Band and conduction of electricity
What is a conductor?
+
_
Ba tte ry
_
+
Sa m p le
Structure of Metal
++++ +++
++++
Delocalized Electrons
Free to move around in the sample and hence can take part in electrical conduction
When many many atoms get together, the multiple closely spaced level become so close that one finds an energy band instead.
One Atom
Many Atoms
……..
Energy Levels
No state here
Lower energy state all filled up
Unoccupied States Fermi Energy
Occupied States
When we applied potential (Conductor)
En e rg y
Electron at higher energy state
Electron at Lower energy state
Conductor: Resistance Vs Temperature
Slope of this line is V/I = R, Resistance of the material
V
Resistance (R)
High Temperature
Low Temperature I
Temperature (T)
One Atom
Two Atoms
Energy Levels
From Energy Levels to Energy Band
Each energy level splits into many closely spaced levels.
Energy Levels
From Energy Levels to Energy Band
Current vs Applied Potential (Conductor)
Voltage (V)
Slope of this line is V/I = R, Resistance of the material (Ohm’s Law)
Current (I)
The Idea of Electrical Resistance
Energy Band and Insulator
Energy Gap
Unoccupied States Fermi Energy
Occupied States
百度文库
Energy
When we applied potential (Insulator)
In an insulator, electron cannot move to a lower energy state as all the states are occupied and Pauli’s exclusion principle prevent the electron to occupy the same state. Hence no current flow.
Introduction to the Nanoworld
A Journey into the Integrated Circuits
Lecture Outline
Introduction
Conductor, Insulator, Semiconductor
Different Types of Semiconductors