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Spin Dependent Transport Spin Dependent Transport Properties of Magnetic Properties of Magnetic Nanostructures Nanostructures Amédée d’Aboville, Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J. Battogtokh J. Battogtokh

Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

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Page 1: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Spin Dependent Transport Spin Dependent Transport Properties of Magnetic Properties of Magnetic

NanostructuresNanostructures

Amédée d’Aboville,Amédée d’Aboville,

with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang,

J. BattogtokhJ. Battogtokh

Page 2: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

OutlineOutline

Introduction to NanostructuresIntroduction to Nanostructures Magnetic NanostructuresMagnetic Nanostructures

GrowthGrowth PropertiesProperties Device fabricationDevice fabrication Device characterizationDevice characterization

Page 3: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

What is Nano?What is Nano? SI unit of length = 1mSI unit of length = 1m Other units are the millimeter: 1x 10Other units are the millimeter: 1x 10 -3-3 m m

micrometer : 1 x 10micrometer : 1 x 10-6-6 m m

nanometer : 1 x 10nanometer : 1 x 10-9-9 m m

1 meter = 1 billion nanometers1 meter = 1 billion nanometers The width of a hair is about 50 000 nmThe width of a hair is about 50 000 nm Nanostructures have at least one dimension Nanostructures have at least one dimension

less than 100nmless than 100nm

Page 4: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

What is Nanotechnology?What is Nanotechnology?

Nanotechnology is the manipulation, Nanotechnology is the manipulation, fabrication, and characterization of fabrication, and characterization of nanostructuresnanostructures

Page 5: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

What are the What are the Applications of Applications of

Nanotechnology?Nanotechnology? Better food packagingBetter food packaging Stronger, lighter materialsStronger, lighter materials Optical ComputingOptical Computing Better DisplaysBetter Displays SunscreenSunscreen Quantum ComputingQuantum Computing Spin-dependent electronicsSpin-dependent electronics

Page 6: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

GalfenolGalfenol

Galfenol is a Gallium Iron compound with a Galfenol is a Gallium Iron compound with a specific stoichiometric composition (Gaspecific stoichiometric composition (Ga0.20.2FeFe0.80.8))

Galfenol is ferromagnetic, and has a Curie Galfenol is ferromagnetic, and has a Curie Temperature of 1000 KTemperature of 1000 K

There are also a range of interesting properties (ie. There are also a range of interesting properties (ie. Magnetostriction).Magnetostriction).

Page 7: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Nanowire Growth: Nanowire Growth: Electro-SpinningElectro-Spinning

A syringe is filled with a A syringe is filled with a solution of correct solution of correct stochiometric compositionsstochiometric compositions

A high potential is applied A high potential is applied between the tip of the needle between the tip of the needle and the collectorand the collector

Nanowires spin out of the Nanowires spin out of the syringesyringe

Page 8: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J
Page 9: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Optical Microscope picture of Electro-spun GaFe NW

mm

Page 10: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Sample Preparation: Sample Preparation: SonicationSonication

•Nanowires are separated from the substrate by placing in an ultrasonic bath

•The Nanowires are left in an IPA solution

Page 11: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

PreparationPreparation

Coordinates of the NW are obtained Coordinates of the NW are obtained using an SEMusing an SEM

Electrodes designed are designed using Electrodes designed are designed using a Computer Aided Design programa Computer Aided Design program

The CAD file is fed into a computerThe CAD file is fed into a computer The computer controls a finely focused The computer controls a finely focused

electron beamelectron beam

Page 12: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

LithographyLithography

A sample is coated with electron sensitive resist A sample is coated with electron sensitive resist material, similar to photographic filmmaterial, similar to photographic film

A computer controlled Electron Beam exposes certain A computer controlled Electron Beam exposes certain parts of the resistparts of the resist

The exposed sections change molecular weight and The exposed sections change molecular weight and can be dissolved in a particular solventcan be dissolved in a particular solvent

Si Wafer

Resist

Nanowire

Page 13: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Ultra-High Vacuum Ultra-High Vacuum DepositionDeposition

State of the art technique to deposit high State of the art technique to deposit high quality materialquality material

High vacuum can be achieved ( up to 10High vacuum can be achieved ( up to 10-10-10 torr) torr) Ti and Cu electrodes are deposited in thin Ti and Cu electrodes are deposited in thin

sheets ( 5nm and 100nm, respectively)sheets ( 5nm and 100nm, respectively)

Page 14: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Metallization and liftoffMetallization and liftoff

Electrodes are deposited with the Ultra High Vacuum Electrodes are deposited with the Ultra High Vacuum Deposition systemDeposition system

The sheet of resist is removed with acetone, leaving The sheet of resist is removed with acetone, leaving only the metal in the exposed partsonly the metal in the exposed parts

Si Wafer

Resist

Nanowire

Page 15: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Galfenol Nanowire with Ti and Cu electrodes(500x)

Page 16: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Spin Dependent Spin Dependent Transport PropertiesTransport Properties

Placing Galfenol NW in an external field can Placing Galfenol NW in an external field can orient its electron spin in the desired directionorient its electron spin in the desired direction

The NW resistance changes with the The NW resistance changes with the orientation of its electrons relative to the orientation of its electrons relative to the currentcurrent

Page 17: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Property MeasurementsProperty Measurements

We apply a voltage and measure the resultant drain to We apply a voltage and measure the resultant drain to source currentsource current

Wafer acts as gate

Source

Nanowire acts as a channel

Drain

Page 18: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Expected ResultsExpected Results

There is a thin sheet of oxide on top of the There is a thin sheet of oxide on top of the nanowire which acts as an insulatornanowire which acts as an insulator

The electrons get through the sheet by The electrons get through the sheet by quantum tunnelingquantum tunneling

The oxide is a Quantum Tunneling BarrierThe oxide is a Quantum Tunneling Barrier

Source DrainNanowire

Wafer

GaFe Oxide

Page 19: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

Measured propertiesMeasured properties

Page 20: Spin Dependent Transport Properties of Magnetic Nanostructures Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, with Dr. J. Philip, Dr. S. Kang, J

ConclusionConclusion

We have grown Galfenol NWWe have grown Galfenol NW Analyzed their structureAnalyzed their structure Built devices out of single NWsBuilt devices out of single NWs Measured these device propertiesMeasured these device properties Analyzed these device measurementsAnalyzed these device measurements