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9 | 3139-3142 | 93494 u and
m ( 28
13 Al ) = 27 98191 u Rationalised 2023-24
Physics
322
13 7
The fission properties of 239
94 Pu are very similar to those of 235
92 U |
9 | 3140-3143 | 98191 u Rationalised 2023-24
Physics
322
13 7
The fission properties of 239
94 Pu are very similar to those of 235
92 U The
average energy released per fission is 180 MeV |
9 | 3141-3144 | Rationalised 2023-24
Physics
322
13 7
The fission properties of 239
94 Pu are very similar to those of 235
92 U The
average energy released per fission is 180 MeV How much energy,
in MeV, is released if all the atoms in 1 kg of pure 239
94 Pu undergo
fission |
9 | 3142-3145 | 7
The fission properties of 239
94 Pu are very similar to those of 235
92 U The
average energy released per fission is 180 MeV How much energy,
in MeV, is released if all the atoms in 1 kg of pure 239
94 Pu undergo
fission 13 |
9 | 3143-3146 | The
average energy released per fission is 180 MeV How much energy,
in MeV, is released if all the atoms in 1 kg of pure 239
94 Pu undergo
fission 13 8
How long can an electric lamp of 100W be kept glowing by fusion of
2 |
9 | 3144-3147 | How much energy,
in MeV, is released if all the atoms in 1 kg of pure 239
94 Pu undergo
fission 13 8
How long can an electric lamp of 100W be kept glowing by fusion of
2 0 kg of deuterium |
9 | 3145-3148 | 13 8
How long can an electric lamp of 100W be kept glowing by fusion of
2 0 kg of deuterium Take the fusion reaction as
2
2
3
1
1
2
H+ H
He+n+3 |
9 | 3146-3149 | 8
How long can an electric lamp of 100W be kept glowing by fusion of
2 0 kg of deuterium Take the fusion reaction as
2
2
3
1
1
2
H+ H
He+n+3 27 MeV
→
13 |
9 | 3147-3150 | 0 kg of deuterium Take the fusion reaction as
2
2
3
1
1
2
H+ H
He+n+3 27 MeV
→
13 9
Calculate the height of the potential barrier for a head on collision
of two deuterons |
9 | 3148-3151 | Take the fusion reaction as
2
2
3
1
1
2
H+ H
He+n+3 27 MeV
→
13 9
Calculate the height of the potential barrier for a head on collision
of two deuterons (Hint: The height of the potential barrier is given
by the Coulomb repulsion between the two deuterons when they
just touch each other |
9 | 3149-3152 | 27 MeV
→
13 9
Calculate the height of the potential barrier for a head on collision
of two deuterons (Hint: The height of the potential barrier is given
by the Coulomb repulsion between the two deuterons when they
just touch each other Assume that they can be taken as hard
spheres of radius 2 |
9 | 3150-3153 | 9
Calculate the height of the potential barrier for a head on collision
of two deuterons (Hint: The height of the potential barrier is given
by the Coulomb repulsion between the two deuterons when they
just touch each other Assume that they can be taken as hard
spheres of radius 2 0 fm |
9 | 3151-3154 | (Hint: The height of the potential barrier is given
by the Coulomb repulsion between the two deuterons when they
just touch each other Assume that they can be taken as hard
spheres of radius 2 0 fm )
13 |
9 | 3152-3155 | Assume that they can be taken as hard
spheres of radius 2 0 fm )
13 10 From the relation R = R0A1/3, where R0 is a constant and A is the
mass number of a nucleus, show that the nuclear matter density is
nearly constant (i |
9 | 3153-3156 | 0 fm )
13 10 From the relation R = R0A1/3, where R0 is a constant and A is the
mass number of a nucleus, show that the nuclear matter density is
nearly constant (i e |
9 | 3154-3157 | )
13 10 From the relation R = R0A1/3, where R0 is a constant and A is the
mass number of a nucleus, show that the nuclear matter density is
nearly constant (i e independent of A) |
9 | 3155-3158 | 10 From the relation R = R0A1/3, where R0 is a constant and A is the
mass number of a nucleus, show that the nuclear matter density is
nearly constant (i e independent of A) Rationalised 2023-24
14 |
9 | 3156-3159 | e independent of A) Rationalised 2023-24
14 1 INTRODUCTION
Devices in which a controlled flow of electrons can be obtained are the
basic building blocks of all the electronic circuits |
9 | 3157-3160 | independent of A) Rationalised 2023-24
14 1 INTRODUCTION
Devices in which a controlled flow of electrons can be obtained are the
basic building blocks of all the electronic circuits Before the discovery of
transistor in 1948, such devices were mostly vacuum tubes (also called
valves) like the vacuum diode which has two electrodes, viz |
9 | 3158-3161 | Rationalised 2023-24
14 1 INTRODUCTION
Devices in which a controlled flow of electrons can be obtained are the
basic building blocks of all the electronic circuits Before the discovery of
transistor in 1948, such devices were mostly vacuum tubes (also called
valves) like the vacuum diode which has two electrodes, viz , anode (often
called plate) and cathode; triode which has three electrodes – cathode,
plate and grid; tetrode and pentode (respectively with 4 and 5 electrodes) |
9 | 3159-3162 | 1 INTRODUCTION
Devices in which a controlled flow of electrons can be obtained are the
basic building blocks of all the electronic circuits Before the discovery of
transistor in 1948, such devices were mostly vacuum tubes (also called
valves) like the vacuum diode which has two electrodes, viz , anode (often
called plate) and cathode; triode which has three electrodes – cathode,
plate and grid; tetrode and pentode (respectively with 4 and 5 electrodes) In a vacuum tube, the electrons are supplied by a heated cathode and
the controlled flow of these electrons in vacuum is obtained by varying
the voltage between its different electrodes |
9 | 3160-3163 | Before the discovery of
transistor in 1948, such devices were mostly vacuum tubes (also called
valves) like the vacuum diode which has two electrodes, viz , anode (often
called plate) and cathode; triode which has three electrodes – cathode,
plate and grid; tetrode and pentode (respectively with 4 and 5 electrodes) In a vacuum tube, the electrons are supplied by a heated cathode and
the controlled flow of these electrons in vacuum is obtained by varying
the voltage between its different electrodes Vacuum is required in the
inter-electrode space; otherwise the moving electrons may lose their
energy on collision with the air molecules in their path |
9 | 3161-3164 | , anode (often
called plate) and cathode; triode which has three electrodes – cathode,
plate and grid; tetrode and pentode (respectively with 4 and 5 electrodes) In a vacuum tube, the electrons are supplied by a heated cathode and
the controlled flow of these electrons in vacuum is obtained by varying
the voltage between its different electrodes Vacuum is required in the
inter-electrode space; otherwise the moving electrons may lose their
energy on collision with the air molecules in their path In these devices
the electrons can flow only from the cathode to the anode (i |
9 | 3162-3165 | In a vacuum tube, the electrons are supplied by a heated cathode and
the controlled flow of these electrons in vacuum is obtained by varying
the voltage between its different electrodes Vacuum is required in the
inter-electrode space; otherwise the moving electrons may lose their
energy on collision with the air molecules in their path In these devices
the electrons can flow only from the cathode to the anode (i e |
9 | 3163-3166 | Vacuum is required in the
inter-electrode space; otherwise the moving electrons may lose their
energy on collision with the air molecules in their path In these devices
the electrons can flow only from the cathode to the anode (i e , only in one
direction) |
9 | 3164-3167 | In these devices
the electrons can flow only from the cathode to the anode (i e , only in one
direction) Therefore, such devices are generally referred to as valves |
9 | 3165-3168 | e , only in one
direction) Therefore, such devices are generally referred to as valves These vacuum tube devices are bulky, consume high power, operate
generally at high voltages (~100 V) and have limited life and low reliability |
9 | 3166-3169 | , only in one
direction) Therefore, such devices are generally referred to as valves These vacuum tube devices are bulky, consume high power, operate
generally at high voltages (~100 V) and have limited life and low reliability The seed of the development of modern solid-state semiconductor
electronics goes back to 1930’s when it was realised that some solid-
state semiconductors and their junctions offer the possibility of controlling
the number and the direction of flow of charge carriers through them |
9 | 3167-3170 | Therefore, such devices are generally referred to as valves These vacuum tube devices are bulky, consume high power, operate
generally at high voltages (~100 V) and have limited life and low reliability The seed of the development of modern solid-state semiconductor
electronics goes back to 1930’s when it was realised that some solid-
state semiconductors and their junctions offer the possibility of controlling
the number and the direction of flow of charge carriers through them Simple excitations like light, heat or small applied voltage can change
the number of mobile charges in a semiconductor |
9 | 3168-3171 | These vacuum tube devices are bulky, consume high power, operate
generally at high voltages (~100 V) and have limited life and low reliability The seed of the development of modern solid-state semiconductor
electronics goes back to 1930’s when it was realised that some solid-
state semiconductors and their junctions offer the possibility of controlling
the number and the direction of flow of charge carriers through them Simple excitations like light, heat or small applied voltage can change
the number of mobile charges in a semiconductor Note that the supply
Chapter Fourteen
SEMICONDUCTOR
ELECTRONICS:
MATERIALS, DEVICES
AND SIMPLE CIRCUITS
Rationalised 2023-24
Physics
324
and flow of charge carriers in the semiconductor devices are within the
solid itself, while in the earlier vacuum tubes/valves, the mobile electrons
were obtained from a heated cathode and they were made to flow in an
evacuated space or vacuum |
9 | 3169-3172 | The seed of the development of modern solid-state semiconductor
electronics goes back to 1930’s when it was realised that some solid-
state semiconductors and their junctions offer the possibility of controlling
the number and the direction of flow of charge carriers through them Simple excitations like light, heat or small applied voltage can change
the number of mobile charges in a semiconductor Note that the supply
Chapter Fourteen
SEMICONDUCTOR
ELECTRONICS:
MATERIALS, DEVICES
AND SIMPLE CIRCUITS
Rationalised 2023-24
Physics
324
and flow of charge carriers in the semiconductor devices are within the
solid itself, while in the earlier vacuum tubes/valves, the mobile electrons
were obtained from a heated cathode and they were made to flow in an
evacuated space or vacuum No external heating or large evacuated space
is required by the semiconductor devices |
9 | 3170-3173 | Simple excitations like light, heat or small applied voltage can change
the number of mobile charges in a semiconductor Note that the supply
Chapter Fourteen
SEMICONDUCTOR
ELECTRONICS:
MATERIALS, DEVICES
AND SIMPLE CIRCUITS
Rationalised 2023-24
Physics
324
and flow of charge carriers in the semiconductor devices are within the
solid itself, while in the earlier vacuum tubes/valves, the mobile electrons
were obtained from a heated cathode and they were made to flow in an
evacuated space or vacuum No external heating or large evacuated space
is required by the semiconductor devices They are small in size, consume
low power, operate at low voltages and have long life and high reliability |
9 | 3171-3174 | Note that the supply
Chapter Fourteen
SEMICONDUCTOR
ELECTRONICS:
MATERIALS, DEVICES
AND SIMPLE CIRCUITS
Rationalised 2023-24
Physics
324
and flow of charge carriers in the semiconductor devices are within the
solid itself, while in the earlier vacuum tubes/valves, the mobile electrons
were obtained from a heated cathode and they were made to flow in an
evacuated space or vacuum No external heating or large evacuated space
is required by the semiconductor devices They are small in size, consume
low power, operate at low voltages and have long life and high reliability Even the Cathode Ray Tubes (CRT) used in television and computer
monitors which work on the principle of vacuum tubes are being replaced
by Liquid Crystal Display (LCD) monitors with supporting solid state
electronics |
9 | 3172-3175 | No external heating or large evacuated space
is required by the semiconductor devices They are small in size, consume
low power, operate at low voltages and have long life and high reliability Even the Cathode Ray Tubes (CRT) used in television and computer
monitors which work on the principle of vacuum tubes are being replaced
by Liquid Crystal Display (LCD) monitors with supporting solid state
electronics Much before the full implications of the semiconductor devices
was formally understood, a naturally occurring crystal of galena (Lead
sulphide, PbS) with a metal point contact attached to it was used as
detector of radio waves |
9 | 3173-3176 | They are small in size, consume
low power, operate at low voltages and have long life and high reliability Even the Cathode Ray Tubes (CRT) used in television and computer
monitors which work on the principle of vacuum tubes are being replaced
by Liquid Crystal Display (LCD) monitors with supporting solid state
electronics Much before the full implications of the semiconductor devices
was formally understood, a naturally occurring crystal of galena (Lead
sulphide, PbS) with a metal point contact attached to it was used as
detector of radio waves In the following sections, we will introduce the basic concepts of
semiconductor physics and discuss some semiconductor devices like
junction diodes (a 2-electrode device) and bipolar junction transistor (a
3-electrode device) |
9 | 3174-3177 | Even the Cathode Ray Tubes (CRT) used in television and computer
monitors which work on the principle of vacuum tubes are being replaced
by Liquid Crystal Display (LCD) monitors with supporting solid state
electronics Much before the full implications of the semiconductor devices
was formally understood, a naturally occurring crystal of galena (Lead
sulphide, PbS) with a metal point contact attached to it was used as
detector of radio waves In the following sections, we will introduce the basic concepts of
semiconductor physics and discuss some semiconductor devices like
junction diodes (a 2-electrode device) and bipolar junction transistor (a
3-electrode device) A few circuits illustrating their applications will also
be described |
9 | 3175-3178 | Much before the full implications of the semiconductor devices
was formally understood, a naturally occurring crystal of galena (Lead
sulphide, PbS) with a metal point contact attached to it was used as
detector of radio waves In the following sections, we will introduce the basic concepts of
semiconductor physics and discuss some semiconductor devices like
junction diodes (a 2-electrode device) and bipolar junction transistor (a
3-electrode device) A few circuits illustrating their applications will also
be described 14 |
9 | 3176-3179 | In the following sections, we will introduce the basic concepts of
semiconductor physics and discuss some semiconductor devices like
junction diodes (a 2-electrode device) and bipolar junction transistor (a
3-electrode device) A few circuits illustrating their applications will also
be described 14 2 CLASSIFICATION OF METALS, CONDUCTORS AND
SEMICONDUCTORS
On the basis of conductivity
On the basis of the relative values of electrical conductivity (s ) or resistivity
(r = 1/s ), the solids are broadly classified as:
(i) Metals: They possess very low resistivity (or high conductivity) |
9 | 3177-3180 | A few circuits illustrating their applications will also
be described 14 2 CLASSIFICATION OF METALS, CONDUCTORS AND
SEMICONDUCTORS
On the basis of conductivity
On the basis of the relative values of electrical conductivity (s ) or resistivity
(r = 1/s ), the solids are broadly classified as:
(i) Metals: They possess very low resistivity (or high conductivity) r ~ 10–2 – 10–8 W m
s ~ 102 – 108 S m–1
(ii) Semiconductors: They have resistivity or conductivity intermediate
to metals and insulators |
9 | 3178-3181 | 14 2 CLASSIFICATION OF METALS, CONDUCTORS AND
SEMICONDUCTORS
On the basis of conductivity
On the basis of the relative values of electrical conductivity (s ) or resistivity
(r = 1/s ), the solids are broadly classified as:
(i) Metals: They possess very low resistivity (or high conductivity) r ~ 10–2 – 10–8 W m
s ~ 102 – 108 S m–1
(ii) Semiconductors: They have resistivity or conductivity intermediate
to metals and insulators r ~ 10–5 – 106 W m
s ~ 105 – 10–6 S m–1
(iii)Insulators: They have high resistivity (or low conductivity) |
9 | 3179-3182 | 2 CLASSIFICATION OF METALS, CONDUCTORS AND
SEMICONDUCTORS
On the basis of conductivity
On the basis of the relative values of electrical conductivity (s ) or resistivity
(r = 1/s ), the solids are broadly classified as:
(i) Metals: They possess very low resistivity (or high conductivity) r ~ 10–2 – 10–8 W m
s ~ 102 – 108 S m–1
(ii) Semiconductors: They have resistivity or conductivity intermediate
to metals and insulators r ~ 10–5 – 106 W m
s ~ 105 – 10–6 S m–1
(iii)Insulators: They have high resistivity (or low conductivity) r ~ 1011 – 1019 W m
s ~ 10–11 – 10–19 S m–1
The values of r and s given above are indicative of magnitude and
could well go outside the ranges as well |
9 | 3180-3183 | r ~ 10–2 – 10–8 W m
s ~ 102 – 108 S m–1
(ii) Semiconductors: They have resistivity or conductivity intermediate
to metals and insulators r ~ 10–5 – 106 W m
s ~ 105 – 10–6 S m–1
(iii)Insulators: They have high resistivity (or low conductivity) r ~ 1011 – 1019 W m
s ~ 10–11 – 10–19 S m–1
The values of r and s given above are indicative of magnitude and
could well go outside the ranges as well Relative values of the resistivity
are not the only criteria for distinguishing metals, insulators and
semiconductors from each other |
9 | 3181-3184 | r ~ 10–5 – 106 W m
s ~ 105 – 10–6 S m–1
(iii)Insulators: They have high resistivity (or low conductivity) r ~ 1011 – 1019 W m
s ~ 10–11 – 10–19 S m–1
The values of r and s given above are indicative of magnitude and
could well go outside the ranges as well Relative values of the resistivity
are not the only criteria for distinguishing metals, insulators and
semiconductors from each other There are some other differences, which
will become clear as we go along in this chapter |
9 | 3182-3185 | r ~ 1011 – 1019 W m
s ~ 10–11 – 10–19 S m–1
The values of r and s given above are indicative of magnitude and
could well go outside the ranges as well Relative values of the resistivity
are not the only criteria for distinguishing metals, insulators and
semiconductors from each other There are some other differences, which
will become clear as we go along in this chapter Our interest in this chapter is in the study of semiconductors which
could be:
(i)
Elemental semiconductors: Si and Ge
(ii) Compound semiconductors: Examples are:
· Inorganic: CdS, GaAs, CdSe, InP, etc |
9 | 3183-3186 | Relative values of the resistivity
are not the only criteria for distinguishing metals, insulators and
semiconductors from each other There are some other differences, which
will become clear as we go along in this chapter Our interest in this chapter is in the study of semiconductors which
could be:
(i)
Elemental semiconductors: Si and Ge
(ii) Compound semiconductors: Examples are:
· Inorganic: CdS, GaAs, CdSe, InP, etc · Organic: anthracene, doped pthalocyanines, etc |
9 | 3184-3187 | There are some other differences, which
will become clear as we go along in this chapter Our interest in this chapter is in the study of semiconductors which
could be:
(i)
Elemental semiconductors: Si and Ge
(ii) Compound semiconductors: Examples are:
· Inorganic: CdS, GaAs, CdSe, InP, etc · Organic: anthracene, doped pthalocyanines, etc · Organic polymers: polypyrrole, polyaniline, polythiophene, etc |
9 | 3185-3188 | Our interest in this chapter is in the study of semiconductors which
could be:
(i)
Elemental semiconductors: Si and Ge
(ii) Compound semiconductors: Examples are:
· Inorganic: CdS, GaAs, CdSe, InP, etc · Organic: anthracene, doped pthalocyanines, etc · Organic polymers: polypyrrole, polyaniline, polythiophene, etc Most of the currently available semiconductor devices are based on
elemental semiconductors Si or Ge and compound inorganic
semiconductors |
9 | 3186-3189 | · Organic: anthracene, doped pthalocyanines, etc · Organic polymers: polypyrrole, polyaniline, polythiophene, etc Most of the currently available semiconductor devices are based on
elemental semiconductors Si or Ge and compound inorganic
semiconductors However, after 1990, a few semiconductor devices using
Rationalised 2023-24
325
Semiconductor Electronics:
Materials, Devices and
Simple Circuits
organic semiconductors and semiconducting polymers have been
developed signalling the birth of a futuristic technology of polymer-
electronics and molecular-electronics |
9 | 3187-3190 | · Organic polymers: polypyrrole, polyaniline, polythiophene, etc Most of the currently available semiconductor devices are based on
elemental semiconductors Si or Ge and compound inorganic
semiconductors However, after 1990, a few semiconductor devices using
Rationalised 2023-24
325
Semiconductor Electronics:
Materials, Devices and
Simple Circuits
organic semiconductors and semiconducting polymers have been
developed signalling the birth of a futuristic technology of polymer-
electronics and molecular-electronics In this chapter, we will restrict
ourselves to the study of inorganic semiconductors, particularly
elemental semiconductors Si and Ge |
9 | 3188-3191 | Most of the currently available semiconductor devices are based on
elemental semiconductors Si or Ge and compound inorganic
semiconductors However, after 1990, a few semiconductor devices using
Rationalised 2023-24
325
Semiconductor Electronics:
Materials, Devices and
Simple Circuits
organic semiconductors and semiconducting polymers have been
developed signalling the birth of a futuristic technology of polymer-
electronics and molecular-electronics In this chapter, we will restrict
ourselves to the study of inorganic semiconductors, particularly
elemental semiconductors Si and Ge The general concepts introduced
here for discussing the elemental semiconductors, by-and-large, apply
to most of the compound semiconductors as well |
9 | 3189-3192 | However, after 1990, a few semiconductor devices using
Rationalised 2023-24
325
Semiconductor Electronics:
Materials, Devices and
Simple Circuits
organic semiconductors and semiconducting polymers have been
developed signalling the birth of a futuristic technology of polymer-
electronics and molecular-electronics In this chapter, we will restrict
ourselves to the study of inorganic semiconductors, particularly
elemental semiconductors Si and Ge The general concepts introduced
here for discussing the elemental semiconductors, by-and-large, apply
to most of the compound semiconductors as well On the basis of energy bands
According to the Bohr atomic model, in an isolated atom the energy of
any of its electrons is decided by the orbit in which it revolves |
9 | 3190-3193 | In this chapter, we will restrict
ourselves to the study of inorganic semiconductors, particularly
elemental semiconductors Si and Ge The general concepts introduced
here for discussing the elemental semiconductors, by-and-large, apply
to most of the compound semiconductors as well On the basis of energy bands
According to the Bohr atomic model, in an isolated atom the energy of
any of its electrons is decided by the orbit in which it revolves But when
the atoms come together to form a solid they are close to each other |
9 | 3191-3194 | The general concepts introduced
here for discussing the elemental semiconductors, by-and-large, apply
to most of the compound semiconductors as well On the basis of energy bands
According to the Bohr atomic model, in an isolated atom the energy of
any of its electrons is decided by the orbit in which it revolves But when
the atoms come together to form a solid they are close to each other So
the outer orbits of electrons from neighbouring atoms would come very
close or could even overlap |
9 | 3192-3195 | On the basis of energy bands
According to the Bohr atomic model, in an isolated atom the energy of
any of its electrons is decided by the orbit in which it revolves But when
the atoms come together to form a solid they are close to each other So
the outer orbits of electrons from neighbouring atoms would come very
close or could even overlap This would make the nature of electron motion
in a solid very different from that in an isolated atom |
9 | 3193-3196 | But when
the atoms come together to form a solid they are close to each other So
the outer orbits of electrons from neighbouring atoms would come very
close or could even overlap This would make the nature of electron motion
in a solid very different from that in an isolated atom Inside the crystal each electron has a unique position and no two
electrons see exactly the same pattern of surrounding charges |
9 | 3194-3197 | So
the outer orbits of electrons from neighbouring atoms would come very
close or could even overlap This would make the nature of electron motion
in a solid very different from that in an isolated atom Inside the crystal each electron has a unique position and no two
electrons see exactly the same pattern of surrounding charges Because
of this, each electron will have a different energy level |
9 | 3195-3198 | This would make the nature of electron motion
in a solid very different from that in an isolated atom Inside the crystal each electron has a unique position and no two
electrons see exactly the same pattern of surrounding charges Because
of this, each electron will have a different energy level These different
energy levels with continuous energy variation form what are called
energy bands |
9 | 3196-3199 | Inside the crystal each electron has a unique position and no two
electrons see exactly the same pattern of surrounding charges Because
of this, each electron will have a different energy level These different
energy levels with continuous energy variation form what are called
energy bands The energy band which includes the energy levels of the
valence electrons is called the valence band |
9 | 3197-3200 | Because
of this, each electron will have a different energy level These different
energy levels with continuous energy variation form what are called
energy bands The energy band which includes the energy levels of the
valence electrons is called the valence band The energy band above the
valence band is called the conduction band |
9 | 3198-3201 | These different
energy levels with continuous energy variation form what are called
energy bands The energy band which includes the energy levels of the
valence electrons is called the valence band The energy band above the
valence band is called the conduction band With no external energy, all
the valence electrons will reside in the valence band |
9 | 3199-3202 | The energy band which includes the energy levels of the
valence electrons is called the valence band The energy band above the
valence band is called the conduction band With no external energy, all
the valence electrons will reside in the valence band If the lowest level in
the conduction band happens to be lower than the highest level of the
valence band, the electrons from the valence band can easily move into
the conduction band |
9 | 3200-3203 | The energy band above the
valence band is called the conduction band With no external energy, all
the valence electrons will reside in the valence band If the lowest level in
the conduction band happens to be lower than the highest level of the
valence band, the electrons from the valence band can easily move into
the conduction band Normally the conduction band is empty |
9 | 3201-3204 | With no external energy, all
the valence electrons will reside in the valence band If the lowest level in
the conduction band happens to be lower than the highest level of the
valence band, the electrons from the valence band can easily move into
the conduction band Normally the conduction band is empty But when
it overlaps on the valence band electrons can move freely into it |
9 | 3202-3205 | If the lowest level in
the conduction band happens to be lower than the highest level of the
valence band, the electrons from the valence band can easily move into
the conduction band Normally the conduction band is empty But when
it overlaps on the valence band electrons can move freely into it This is
the case with metallic conductors |
9 | 3203-3206 | Normally the conduction band is empty But when
it overlaps on the valence band electrons can move freely into it This is
the case with metallic conductors If there is some gap between the conduction band and the valence
band, electrons in the valence band all remain bound and no free electrons
are available in the conduction band |
9 | 3204-3207 | But when
it overlaps on the valence band electrons can move freely into it This is
the case with metallic conductors If there is some gap between the conduction band and the valence
band, electrons in the valence band all remain bound and no free electrons
are available in the conduction band This makes the material an
insulator |
9 | 3205-3208 | This is
the case with metallic conductors If there is some gap between the conduction band and the valence
band, electrons in the valence band all remain bound and no free electrons
are available in the conduction band This makes the material an
insulator But some of the electrons from the valence band may gain
external energy to cross the gap between the conduction band and the
valence band |
9 | 3206-3209 | If there is some gap between the conduction band and the valence
band, electrons in the valence band all remain bound and no free electrons
are available in the conduction band This makes the material an
insulator But some of the electrons from the valence band may gain
external energy to cross the gap between the conduction band and the
valence band Then these electrons will move into the conduction band |
9 | 3207-3210 | This makes the material an
insulator But some of the electrons from the valence band may gain
external energy to cross the gap between the conduction band and the
valence band Then these electrons will move into the conduction band At the same time they will create vacant energy levels in the valence band
where other valence electrons can move |
9 | 3208-3211 | But some of the electrons from the valence band may gain
external energy to cross the gap between the conduction band and the
valence band Then these electrons will move into the conduction band At the same time they will create vacant energy levels in the valence band
where other valence electrons can move Thus the process creates the
possibility of conduction due to electrons in conduction band as well as
due to vacancies in the valence band |
9 | 3209-3212 | Then these electrons will move into the conduction band At the same time they will create vacant energy levels in the valence band
where other valence electrons can move Thus the process creates the
possibility of conduction due to electrons in conduction band as well as
due to vacancies in the valence band Let us consider what happens in the case of Si or Ge crystal containing
N atoms |
9 | 3210-3213 | At the same time they will create vacant energy levels in the valence band
where other valence electrons can move Thus the process creates the
possibility of conduction due to electrons in conduction band as well as
due to vacancies in the valence band Let us consider what happens in the case of Si or Ge crystal containing
N atoms For Si, the outermost orbit is the third orbit (n = 3), while for Ge
it is the fourth orbit (n = 4) |
9 | 3211-3214 | Thus the process creates the
possibility of conduction due to electrons in conduction band as well as
due to vacancies in the valence band Let us consider what happens in the case of Si or Ge crystal containing
N atoms For Si, the outermost orbit is the third orbit (n = 3), while for Ge
it is the fourth orbit (n = 4) The number of electrons in the outermost
orbit is 4 (2s and 2p electrons) |
9 | 3212-3215 | Let us consider what happens in the case of Si or Ge crystal containing
N atoms For Si, the outermost orbit is the third orbit (n = 3), while for Ge
it is the fourth orbit (n = 4) The number of electrons in the outermost
orbit is 4 (2s and 2p electrons) Hence, the total number of outer electrons
in the crystal is 4N |
9 | 3213-3216 | For Si, the outermost orbit is the third orbit (n = 3), while for Ge
it is the fourth orbit (n = 4) The number of electrons in the outermost
orbit is 4 (2s and 2p electrons) Hence, the total number of outer electrons
in the crystal is 4N The maximum possible number of electrons in the
outer orbit is 8 (2s + 6p electrons) |
9 | 3214-3217 | The number of electrons in the outermost
orbit is 4 (2s and 2p electrons) Hence, the total number of outer electrons
in the crystal is 4N The maximum possible number of electrons in the
outer orbit is 8 (2s + 6p electrons) So, for the 4N valence electrons there
are 8N available energy states |
9 | 3215-3218 | Hence, the total number of outer electrons
in the crystal is 4N The maximum possible number of electrons in the
outer orbit is 8 (2s + 6p electrons) So, for the 4N valence electrons there
are 8N available energy states These 8N discrete energy levels can either
form a continuous band or they may be grouped in different bands
depending upon the distance between the atoms in the crystal (see box
on Band Theory of Solids) |
9 | 3216-3219 | The maximum possible number of electrons in the
outer orbit is 8 (2s + 6p electrons) So, for the 4N valence electrons there
are 8N available energy states These 8N discrete energy levels can either
form a continuous band or they may be grouped in different bands
depending upon the distance between the atoms in the crystal (see box
on Band Theory of Solids) At the distance between the atoms in the crystal lattices of Si and Ge,
the energy band of these 8N states is split apart into two which are
separated by an energy gap Eg (Fig |
9 | 3217-3220 | So, for the 4N valence electrons there
are 8N available energy states These 8N discrete energy levels can either
form a continuous band or they may be grouped in different bands
depending upon the distance between the atoms in the crystal (see box
on Band Theory of Solids) At the distance between the atoms in the crystal lattices of Si and Ge,
the energy band of these 8N states is split apart into two which are
separated by an energy gap Eg (Fig 14 |
9 | 3218-3221 | These 8N discrete energy levels can either
form a continuous band or they may be grouped in different bands
depending upon the distance between the atoms in the crystal (see box
on Band Theory of Solids) At the distance between the atoms in the crystal lattices of Si and Ge,
the energy band of these 8N states is split apart into two which are
separated by an energy gap Eg (Fig 14 1) |
9 | 3219-3222 | At the distance between the atoms in the crystal lattices of Si and Ge,
the energy band of these 8N states is split apart into two which are
separated by an energy gap Eg (Fig 14 1) The lower band which is
completely occupied by the 4N valence electrons at temperature of absolute
zero is the valence band |
9 | 3220-3223 | 14 1) The lower band which is
completely occupied by the 4N valence electrons at temperature of absolute
zero is the valence band The other band consisting of 4N energy states,
called the conduction band, is completely empty at absolute zero |
9 | 3221-3224 | 1) The lower band which is
completely occupied by the 4N valence electrons at temperature of absolute
zero is the valence band The other band consisting of 4N energy states,
called the conduction band, is completely empty at absolute zero Rationalised 2023-24
Physics
326
The lowest energy level in the
conduction band is shown as EC and
highest energy level in the valence band
is shown as EV |
9 | 3222-3225 | The lower band which is
completely occupied by the 4N valence electrons at temperature of absolute
zero is the valence band The other band consisting of 4N energy states,
called the conduction band, is completely empty at absolute zero Rationalised 2023-24
Physics
326
The lowest energy level in the
conduction band is shown as EC and
highest energy level in the valence band
is shown as EV Above EC and below EV
there are a large number of closely spaced
energy levels, as shown in Fig |
9 | 3223-3226 | The other band consisting of 4N energy states,
called the conduction band, is completely empty at absolute zero Rationalised 2023-24
Physics
326
The lowest energy level in the
conduction band is shown as EC and
highest energy level in the valence band
is shown as EV Above EC and below EV
there are a large number of closely spaced
energy levels, as shown in Fig 14 |
9 | 3224-3227 | Rationalised 2023-24
Physics
326
The lowest energy level in the
conduction band is shown as EC and
highest energy level in the valence band
is shown as EV Above EC and below EV
there are a large number of closely spaced
energy levels, as shown in Fig 14 1 |
9 | 3225-3228 | Above EC and below EV
there are a large number of closely spaced
energy levels, as shown in Fig 14 1 The gap between the top of the valence
band and bottom of the conduction band
is called the energy band gap (Energy gap
Eg) |
9 | 3226-3229 | 14 1 The gap between the top of the valence
band and bottom of the conduction band
is called the energy band gap (Energy gap
Eg) It may be large, small, or zero,
depending upon the material |
9 | 3227-3230 | 1 The gap between the top of the valence
band and bottom of the conduction band
is called the energy band gap (Energy gap
Eg) It may be large, small, or zero,
depending upon the material These
different situations, are depicted in Fig |
9 | 3228-3231 | The gap between the top of the valence
band and bottom of the conduction band
is called the energy band gap (Energy gap
Eg) It may be large, small, or zero,
depending upon the material These
different situations, are depicted in Fig 14 |
9 | 3229-3232 | It may be large, small, or zero,
depending upon the material These
different situations, are depicted in Fig 14 2 and discussed below:
Case I: This refers to a situation, as
shown in Fig |
9 | 3230-3233 | These
different situations, are depicted in Fig 14 2 and discussed below:
Case I: This refers to a situation, as
shown in Fig 14 |
9 | 3231-3234 | 14 2 and discussed below:
Case I: This refers to a situation, as
shown in Fig 14 2(a) |
9 | 3232-3235 | 2 and discussed below:
Case I: This refers to a situation, as
shown in Fig 14 2(a) One can have a
metal either when the conduction band
is partially filled and the balanced band
is partially empty or when the conduction
and valance bands overlap |
9 | 3233-3236 | 14 2(a) One can have a
metal either when the conduction band
is partially filled and the balanced band
is partially empty or when the conduction
and valance bands overlap When there
is overlap electrons from valence band can
easily move into the conduction band |
9 | 3234-3237 | 2(a) One can have a
metal either when the conduction band
is partially filled and the balanced band
is partially empty or when the conduction
and valance bands overlap When there
is overlap electrons from valence band can
easily move into the conduction band This situation makes a large number of
electrons available for electrical conduction |
9 | 3235-3238 | One can have a
metal either when the conduction band
is partially filled and the balanced band
is partially empty or when the conduction
and valance bands overlap When there
is overlap electrons from valence band can
easily move into the conduction band This situation makes a large number of
electrons available for electrical conduction When the valence band is
partially empty, electrons from its lower level can move to higher level
making conduction possible |
9 | 3236-3239 | When there
is overlap electrons from valence band can
easily move into the conduction band This situation makes a large number of
electrons available for electrical conduction When the valence band is
partially empty, electrons from its lower level can move to higher level
making conduction possible Therefore, the resistance of such materials
is low or the conductivity is high |
9 | 3237-3240 | This situation makes a large number of
electrons available for electrical conduction When the valence band is
partially empty, electrons from its lower level can move to higher level
making conduction possible Therefore, the resistance of such materials
is low or the conductivity is high FIGURE 14 |
9 | 3238-3241 | When the valence band is
partially empty, electrons from its lower level can move to higher level
making conduction possible Therefore, the resistance of such materials
is low or the conductivity is high FIGURE 14 2 Difference between energy bands of (a) metals,
(b) insulators and (c) semiconductors |
Subsets and Splits