Elisa De Ranieri

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My research properties of GaMnAs, a magnetic
semiconductor

• Elisa De Ranieri
• University of Cambridge

2nd VC, 07 Mar 2007
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Semiconductors
Semiconductors conduct current only under certain
conditions
Conduction can be related to the energy of the
electrons in the system
Bands of E conduction and valence band
Conduction band ? empty
E
Valence band ? full
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Semiconductors
E gap
METALS
INSULATORS
SEMICONDUCTORS
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Ferromagnets
Each atom behaves like a small magnet
Vector represent the magnetic moment
Moments couple and align in the same direction
even with no applied field
Domains are formed ? energetic reason
Moments align with the external magnetic field
B
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Magnetic semiconductors
Semiconducting magnetic properties ? density of
charge carriers
Resistance changes with the magnetic field
orientation ? anisotropic magneto resistance (AMR)
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Magnetic semiconductors
Gold contacts
Channel
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Devices
My device fabricated on a GaMnAs
1. Layout designed with AutoCAD 2. Fabrication
metal evaporation, etching, electron beam
lithography 3. Measurements
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Clean rooms
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Processes
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Measurements
Cryostat ? very low temperature
Liquid helium inside
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Measurements
Screen of the parameter analyser
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Measurements
Data looks like this
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Finally

• Data needs to be interpreted in view of the
  theoretical knowledge of physics
• useful discussion with experts in the field
  (supervisors, other academics)
• publication of results on scientific journals