Spin dependent transport properties of magnetic nanostructures
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Spin Dependent Transport Properties of Magnetic Nanostructures. Amédée d’Aboville, with Dr. J. Philip, Dr. S. Kang, J. Battogtokh. Outline. Introduction to Nanostructures Magnetic Nanostructures Growth Properties Device fabrication Device characterization. What is Nano?.

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Spin dependent transport properties of magnetic nanostructures
Spin Dependent Transport Properties of Magnetic Nanostructures

Amédée d’Aboville,

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

J. Battogtokh


Outline
Outline Nanostructures

  • Introduction to Nanostructures

  • Magnetic Nanostructures

    • Growth

    • Properties

    • Device fabrication

    • Device characterization


What is nano
What is Nano? Nanostructures

  • SI unit of length = 1m

  • Other units are the millimeter: 1x 10-3 m

    micrometer : 1 x 10-6 m

    nanometer : 1 x 10-9 m

    1 meter = 1 billion nanometers

  • The width of a hair is about 50 000 nm

  • Nanostructures have at least one dimension less than 100nm


What is nanotechnology
What is Nanotechnology? Nanostructures

  • Nanotechnology is the manipulation, fabrication, and characterization of nanostructures


What are the applications of nanotechnology
What are the Applications of Nanotechnology? Nanostructures

  • Better food packaging

  • Stronger, lighter materials

  • Optical Computing

  • Better Displays

  • Sunscreen

  • Quantum Computing

  • Spin-dependent electronics


Galfenol
Galfenol Nanostructures

  • Galfenol is a Gallium Iron compound with a specific stoichiometric composition (Ga0.2Fe0.8)

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

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


Nanowire growth electro spinning
Nanowire Growth: Electro-Spinning Nanostructures

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

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

  • Nanowires spin out of the syringe



Sample preparation sonication
Sample Preparation: Sonication Nanostructures

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

  • The Nanowires are left in an IPA solution


Preparation
Preparation Nanostructures

  • Coordinates of the NW are obtained using an SEM

  • Electrodes designed are designed using a Computer Aided Design program

  • The CAD file is fed into a computer

  • The computer controls a finely focused electron beam


Lithography
Lithography Nanostructures

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

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

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

Resist

Nanowire

Si Wafer


Ultra high vacuum deposition
Ultra-High Vacuum Deposition Nanostructures

  • State of the art technique to deposit high quality material

  • High vacuum can be achieved ( up to 10-10 torr)

  • Ti and Cu electrodes are deposited in thin sheets ( 5nm and 100nm, respectively)


Metallization and liftoff
Metallization and liftoff Nanostructures

  • Electrodes are deposited with the Ultra High Vacuum Deposition system

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

Resist

Nanowire

Si Wafer



Spin dependent transport properties
Spin Dependent Transport Properties Nanostructures

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

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


Property measurements
Property Measurements Nanostructures

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

Nanowire acts as a channel

Drain

Source

Wafer acts as gate


Expected results
Expected Results Nanostructures

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

  • The electrons get through the sheet by quantum tunneling

  • The oxide is a Quantum Tunneling Barrier

GaFe Oxide

Drain

Source

Nanowire

Wafer


Measured properties
Measured properties Nanostructures


Conclusion
Conclusion Nanostructures

  • We have grown Galfenol NW

  • Analyzed their structure

  • Built devices out of single NWs

  • Measured these device properties

  • Analyzed these device measurements


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