Field Emission Enhancement Field Emission Enhancement

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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