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Comparison of Field Emission Behaviors Comparison of Field Emission Behaviors of Graphite Vitreous Carbon and Diamond of Graphite Vitreous Carbon and Diamond
PowdersPowders
S H Lee K R Lee K Y Eun
Thin Film Technology Research Center
Korea Institute of Science and Technology
P O Box 131 Cheongryang Seoul 130-650 Korea
Field Emission DevicesField Emission Devices
Applications
Vacuum microelectronics (Display Microwave devices etc)
Problems of cathode materials
Mo Si Difficult to process
High cost to make devices
Change of effective work function by residual gas
Decrease of life time by back sputtering
Others material for cold cathode
Diamond Diamond-like carbon Carbon Nano-tube etc
Carbon Base Cathode MaterialsCarbon Base Cathode Materials
Diamond sp3 bonds
Diamond-Like Carbon Amorphous structure of
sp3 sp2 and sp1 bonds
Graphite sp2 bonds Semi-metal (Free
carrier 10-18 cm-3) High electrically
conductive material
Carbon Nano-tube Structure like rolled grap
hite sheet Very high aspect ratio Problem of high tempera
ture growth
Vitreous Carbon Amorphous structure of
sp2 bonds High electrically conduct
ive material
Problems in Carbon Base CathodeProblems in Carbon Base Cathode
Limited understanding on field emission mechanism
Uniformity and stability of the emission still remain as the
prerequisites for the applications
It is difficult to compare field emission behaviors between
carbon materials of various doping levels
It is necessary that the difference of bonding
structure is investigated
Purposes of the Present WorkPurposes of the Present Work
Comparison of the field emission behaviors between Diamo
nd Vitreous Carbon and Graphite Powders
Effect of sp2 and sp3 bonding
Effect of crystal and amorphous structure
Observation of emission light image to identigy the emission
sites
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Field Emission DevicesField Emission Devices
Applications
Vacuum microelectronics (Display Microwave devices etc)
Problems of cathode materials
Mo Si Difficult to process
High cost to make devices
Change of effective work function by residual gas
Decrease of life time by back sputtering
Others material for cold cathode
Diamond Diamond-like carbon Carbon Nano-tube etc
Carbon Base Cathode MaterialsCarbon Base Cathode Materials
Diamond sp3 bonds
Diamond-Like Carbon Amorphous structure of
sp3 sp2 and sp1 bonds
Graphite sp2 bonds Semi-metal (Free
carrier 10-18 cm-3) High electrically
conductive material
Carbon Nano-tube Structure like rolled grap
hite sheet Very high aspect ratio Problem of high tempera
ture growth
Vitreous Carbon Amorphous structure of
sp2 bonds High electrically conduct
ive material
Problems in Carbon Base CathodeProblems in Carbon Base Cathode
Limited understanding on field emission mechanism
Uniformity and stability of the emission still remain as the
prerequisites for the applications
It is difficult to compare field emission behaviors between
carbon materials of various doping levels
It is necessary that the difference of bonding
structure is investigated
Purposes of the Present WorkPurposes of the Present Work
Comparison of the field emission behaviors between Diamo
nd Vitreous Carbon and Graphite Powders
Effect of sp2 and sp3 bonding
Effect of crystal and amorphous structure
Observation of emission light image to identigy the emission
sites
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Carbon Base Cathode MaterialsCarbon Base Cathode Materials
Diamond sp3 bonds
Diamond-Like Carbon Amorphous structure of
sp3 sp2 and sp1 bonds
Graphite sp2 bonds Semi-metal (Free
carrier 10-18 cm-3) High electrically
conductive material
Carbon Nano-tube Structure like rolled grap
hite sheet Very high aspect ratio Problem of high tempera
ture growth
Vitreous Carbon Amorphous structure of
sp2 bonds High electrically conduct
ive material
Problems in Carbon Base CathodeProblems in Carbon Base Cathode
Limited understanding on field emission mechanism
Uniformity and stability of the emission still remain as the
prerequisites for the applications
It is difficult to compare field emission behaviors between
carbon materials of various doping levels
It is necessary that the difference of bonding
structure is investigated
Purposes of the Present WorkPurposes of the Present Work
Comparison of the field emission behaviors between Diamo
nd Vitreous Carbon and Graphite Powders
Effect of sp2 and sp3 bonding
Effect of crystal and amorphous structure
Observation of emission light image to identigy the emission
sites
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Problems in Carbon Base CathodeProblems in Carbon Base Cathode
Limited understanding on field emission mechanism
Uniformity and stability of the emission still remain as the
prerequisites for the applications
It is difficult to compare field emission behaviors between
carbon materials of various doping levels
It is necessary that the difference of bonding
structure is investigated
Purposes of the Present WorkPurposes of the Present Work
Comparison of the field emission behaviors between Diamo
nd Vitreous Carbon and Graphite Powders
Effect of sp2 and sp3 bonding
Effect of crystal and amorphous structure
Observation of emission light image to identigy the emission
sites
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Purposes of the Present WorkPurposes of the Present Work
Comparison of the field emission behaviors between Diamo
nd Vitreous Carbon and Graphite Powders
Effect of sp2 and sp3 bonding
Effect of crystal and amorphous structure
Observation of emission light image to identigy the emission
sites
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
0 500 1000 1500 2000 2500
Inte
nsi
ty [a
u]
Raman shift [cm-1]
Raman Spectrum of Used PowdersRaman Spectrum of Used Powders
Graphite
Diamond
Vitreous Carbon
1330
1351 1573
1342 1575
Diamond 1018 [Ωcm] Graphite lt 10-5 [Ωcm]Vitreous Carbon lt10-3 [Ωcm]
Electrical conductivity
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Sample PreparationSample Preparation
glass
Screen printing method
Mo layer
glass
Silver paste mixed with the carbon powder
glass
Curing 150 C for 60 min amp 450 C for 60 min
Sputtering
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Surface MorphologySurface Morphology
10 m
20 m
10 m
20 m
10 m
20 m
Graphite DiamondVitreous Carbon
Grain size ~ 20 microm Roughness ~ 5 microm
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Current-Voltage MeasurementCurrent-Voltage Measurement
Keithley 6517Electrometer
SRS PS350Power Supply
x
y
ze
Anode
Cathode
CCDViewing System
ComputerInterface
3-D Manipulator
Viewing System
SRS PS350Power Supply
Keithley 6517Electrometer
Phosphor coated ITO-glass
Cathode
Spacer
CCD
e
Visible Light
998 Ω
Annealing
Over 6 hours by halogen lamp i
n vacuum (about 150 ordmC)
Out-gassing
at 1times10-7 Torr over 2 hours
Distance Control
50 microm ~ 200 microm
Spacer
Alumina (Al2O3)
Thickness 478 microm
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Current-Voltage BehaviorCurrent-Voltage Behavior
-2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28-5
0
5
10
15
20
25
30
35
40
45
50
55
p = 1 x 10-7 Torrball-type anode
Cu
rre
nt
[A]
Electric Field [Vm]
Graphite
Vitreous Carbon
Diamond
Typical current-voltage characters of field emission
The lowest on-set electric field and the most stable emission behavior in graphite
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Results and DiscussionsResults and Discussions Effect of sp2 and sp3 bonding
We observed the lower electric field and higher current density in
graphite than those of diamond or vitreous carbon
For good field emission it is necessary that the cathode materials
has much content of sp2 bonding
The sp2 bonding works as the electrical conductive channel and the
source of electron supply
Effect of crystal and amorphous structure
The crystal structure is favorable in the view point of stable field
emission from the carbon materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
0 500 1000 1500
0
10
20
30
40
50
60p = 1 x 10-7 Torrflat-type anodeDistance=478m
Cu
rren
t [
A]
Voltage [V]
Electron Emission Image of GraphiteElectron Emission Image of Graphite
Init
Condition
At 1000 V
At 1200 V
At 1500 V
On-set electric field about 2 ~ 3 V The localized light emission was observed
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
-500 0 500 1000 1500 2000 2500 3000 3500 4000
0
10
20
30
40
50
60
70
80
Cu
rren
t [
A]
Time [sec]
Emission Image for Fluctuation of GraphiteEmission Image for Fluctuation of Graphite
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
At 0 sec
At 1000 sec
At 2000 sec
At 3600 sec
The local emission sites are not static
The total current decreased and stabilized after long emission
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
Results and DiscussionsResults and Discussions The light emission as applied voltage
We observed the light emitted locally and occasionally disappeared
As the voltage increased the light emitted more brightly but sometimes th
e emission site changed
The electrically conductive channel forms locally and is varied depending
on the applied voltage
Possibility of the full area light emission
The full area light emission can be occurred by adding an insulating layer
between the electrode and the cathode materials The insulating layer see
ms to reduce the difference in electric conductivity in the cathode material
s S H Ahn et al J Kor Vac Soc 9 (2000) 122
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
ConclusionsConclusions The field emission behaviors of the carbon base cathode materials
strongly depend on the electrical conductivity of the materials
The structural requirements for a good cold cathode of carbon
materials
Well developed crystal structure for emission stability
High content of sp2 hybridization bond for the ease of electron
supply
Emission stability can be reduced by controlling the electrical contact
between electrode and the cathode However localized emission still
remains as a limitation of the carbon cathode materials
