technical presentation ap4
TRANSCRIPT
Field Emission Enhancement Field Emission Enhancement
from from
Patterned Gallium Nitride NanowiresPatterned Gallium Nitride Nanowires
OverviewOverview
IntroductionIntroduction GaN nanowire growth
Experimental Procedures Results & Discussion
Field emission of GaN nanowires Experimental Procedures Results & Discussion
Conclusions
ObjectiveObjective
Obtained ENHANCED Field Emission from patterned GaN nanowire films
IntroductionIntroduction
Field Emitters ApplicationsUltrahigh Speed Devices
Electron Beam Lithography
Low Power & High Brightness Field
Emission Flat Panel Displays
GaN for Field Emission Applications
IntroductionIntroduction
GaN
FE enhancement anticipated from GaN nanowires
1 I. Berishev et. al., APL, 73, 1808 (1998)2 B. L. Ward et. al., JAP, 84, 5238 (1998)
GaN Films1
GaN Pyramid Arrays2
Roughed GaN films2
Wide Bandgap (3.45 eV)Strong Chemical & Mechanical StabilitiesLow Electron Affinity (2.7~3.3 eV)
IntroductionIntroduction Field Emission of GaN nanowire films
Issue - Screening effectSolution – Patterning the nanowires
3 H. M. Manohara et. al., JVST B, 23, 157 (2005)
Nanotubes in regular patterned arrays of bundles3
versus
dense mats nanotubes, thin films of nanotubes or arrayed individual nanotubes
Experimental ProceduresExperimental Procedures
Schematic diagram of experimental setup
Gas InletTo Pump
248 nm KrF laser beam
Focus Lens
View Port
Substrate Heater
Rotating Target
Plasma Plume
n-Si substrate
n-Si substrateUnpatterned Patterned
SEM Images
Results & DiscussionResults & Discussion
500 nm
100 nm
500 nm
Results & DiscussionResults & Discussion
20 nm 2 nm
2.7245 Å(100)
(010)
(100)
(1-10)
TEM Images
Experimental ProceduresExperimental Procedures
Schematic diagram of field emission measurement setup
Pump
Anode
Cathode
V/A 100 m
Device characterization – Field Emission Study
With patterningWithout patterning
0.001 mA/cm2 0.96 mA/cm2
n-Si substraten-Si substrate
Results & Discussion
INCREASE 960 TIMES!!!
Results & DiscussionResults & DiscussionField Emission of GaN nanowire films
With patterningWithout patterning
Substrate
FE collection Enhanced FE collection
Substrate
ConclusionsConclusions Density patterned GaN nanowires synthesized by Density patterned GaN nanowires synthesized by
pulsed laser ablationpulsed laser ablation
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Morphology & Structure studied
Field Emission studiedTurn-on field = 8.4 V/m at 0.01 mA/cm2
Peak current density = 0.96 mA/cm2 at 10.8 V/m
Field Emission properties depend onGood crystalline qualityLow electron affinityDensity difference