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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  • Spin Dependent Transport Properties of Magnetic NanostructuresAmde dAboville, with Dr. J. Philip, Dr. S. Kang, J. Battogtokh

  • OutlineIntroduction to NanostructuresMagnetic NanostructuresGrowthPropertiesDevice fabricationDevice characterization

  • What is Nano?SI unit of length = 1mOther units are the millimeter: 1x 10-3 mmicrometer : 1 x 10-6 mnanometer : 1 x 10-9 m1 meter = 1 billion nanometersThe width of a hair is about 50 000 nmNanostructures have at least one dimension less than 100nm

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

  • What are the Applications of Nanotechnology?Better food packagingStronger, lighter materialsOptical ComputingBetter DisplaysSunscreenQuantum ComputingSpin-dependent electronics

  • GalfenolGalfenol is a Gallium Iron compound with a specific stoichiometric composition (Ga0.2Fe0.8)Galfenol is ferromagnetic, and has a Curie Temperature of 1000 KThere are also a range of interesting properties (ie. Magnetostriction).

  • Nanowire Growth: Electro-SpinningA syringe is filled with a solution of correct stochiometric compositionsA high potential is applied between the tip of the needle and the collectorNanowires spin out of the syringe

  • Optical Microscope picture of Electro-spun GaFe NWmm

  • Sample Preparation: SonicationNanowires are separated from the substrate by placing in an ultrasonic bathThe Nanowires are left in an IPA solution

  • PreparationCoordinates of the NW are obtained using an SEMElectrodes designed are designed using a Computer Aided Design programThe CAD file is fed into a computerThe computer controls a finely focused electron beam

  • LithographyA sample is coated with electron sensitive resist material, similar to photographic filmA computer controlled Electron Beam exposes certain parts of the resistThe exposed sections change molecular weight and can be dissolved in a particular solvent

    Si WaferResistNanowire

  • Ultra-High Vacuum DepositionState of the art technique to deposit high quality materialHigh vacuum can be achieved ( up to 10-10 torr)Ti and Cu electrodes are deposited in thin sheets ( 5nm and 100nm, respectively)

  • Metallization and liftoffElectrodes are deposited with the Ultra High Vacuum Deposition systemThe sheet of resist is removed with acetone, leaving only the metal in the exposed partsSi WaferResistNanowire

  • Galfenol Nanowire with Ti and Cu electrodes(500x)

  • Spin Dependent Transport PropertiesPlacing Galfenol NW in an external field can orient its electron spin in the desired directionThe NW resistance changes with the orientation of its electrons relative to the current

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

    Wafer acts as gateSourceNanowire acts as a channelDrain

  • Expected ResultsThere is a thin sheet of oxide on top of the nanowire which acts as an insulatorThe electrons get through the sheet by quantum tunnelingThe oxide is a Quantum Tunneling BarrierSourceDrainNanowireWaferGaFe Oxide

  • Measured properties

  • ConclusionWe have grown Galfenol NWAnalyzed their structureBuilt devices out of single NWsMeasured these device propertiesAnalyzed these device measurements