Field Emission Enhancement from Patterned Gallium Nitride Nanowires

Overview Introduction GaN nanowire growth Experimental Procedures Results & Discussion Field emission of GaN nanowires Experimental Procedures Results & Discussion Conclusions

Introduction

GaN nanowire growth

Experimental Procedures

Results & Discussion

Field emission of GaN nanowires

Experimental Procedures

Results & Discussion

Conclusions

Objective Obtained ENHANCED Field Emission from patterned GaN nanowire films

Introduction Field Emitters Applications Ultrahigh Speed Devices Electron Beam Lithography Low Power & High Brightness Field Emission Flat Panel Displays

Field Emitters Applications

Ultrahigh Speed Devices

Electron Beam Lithography

Low Power & High Brightness Field

Emission Flat Panel Displays

Introduction GaN GaN for Field Emission Applications GaN Films 1 GaN Pyramid Arrays 2 Roughed GaN films 2 Wide Bandgap (3.45 eV) Strong Chemical & Mechanical Stabilities Low Electron Affinity (2.7~3.3 eV) 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

GaN for Field Emission Applications

GaN Films 1

GaN Pyramid Arrays 2

Roughed GaN films 2

Wide Bandgap (3.45 eV)

Strong Chemical & Mechanical Stabilities

Low Electron Affinity (2.7~3.3 eV)

Introduction Field Emission of GaN nanowire films Issue - Screening effect Solution – Patterning the nanowires 3 H. M. Manohara et. al., JVST B, 23, 157 (2005) Nanotubes in regular patterned arrays of bundles 3 versus dense mats nanotubes, thin films of nanotubes or arrayed individual nanotubes

Field Emission of GaN nanowire films

Issue - Screening effect

Solution – Patterning the nanowires

Experimental Procedures Schematic diagram of experimental setup Gas Inlet To Pump 248 nm KrF laser beam Focus Lens View Port Substrate Heater Rotating Target Plasma Plume n-Si substrate n-Si substrate Unpatterned Patterned

Results & Discussion SEM Images 500 nm 100 nm 500 nm

Results & Discussion TEM Images 20 nm 2 nm 2.7245 Å (100) (010) (100) (1-10)

Experimental Procedures Schematic diagram of field emission measurement setup 100  m Pump Anode Cathode V/A

Device characterization – Field Emission Study With patterning Without patterning Results & Discussion INCREASE 960 TIMES!!! 0.001 mA/cm 2 0.96 mA/cm 2 n-Si substrate n-Si substrate

Results & Discussion Field Emission of GaN nanowire films With patterning Without patterning Substrate FE collection Enhanced FE collection Substrate

Conclusions Density patterned GaN nanowires synthesized by pulsed laser ablation Morphology & Structure studied Field Emission studied Turn-on field = 8.4 V/  m at 0.01 mA/cm 2 Peak current density = 0.96 mA/cm 2 at 10.8 V/  m Field Emission properties depend on Good crystalline quality Low electron affinity Density difference THANK YOU

Density patterned GaN nanowires synthesized by pulsed laser ablation

Morphology & Structure studied

Field Emission studied

Turn-on field = 8.4 V/  m at 0.01 mA/cm 2

Peak current density = 0.96 mA/cm 2 at 10.8 V/  m

Field Emission properties depend on

Good crystalline quality

Low electron affinity

Density difference