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Semiconductors.ppt

  • Количество слайдов: 13

My research: properties of Ga. Mn. As, a magnetic semiconductor Elisa De Ranieri University My research: properties of Ga. Mn. As, a magnetic semiconductor Elisa De Ranieri University of Cambridge 2 nd VC, 07 Mar 2007

Semiconductors conduct current only under certain conditions Conduction can be related to the energy Semiconductors conduct current only under certain conditions Conduction can be related to the energy of the electrons in the system E Bands of E: conduction and valence band Conduction band empty Valence band full

Semiconductors METALS E gap INSULATORS SEMICONDUCTORS Semiconductors METALS E gap INSULATORS SEMICONDUCTORS

Ferromagnets Each atom behaves like a small magnet Vector represent the “magnetic moment” Moments 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 B Moments align with the external magnetic field

Magnetic semiconductors Semiconducting + magnetic properties density of charge carriers I B V Resistance Magnetic semiconductors Semiconducting + magnetic properties density of charge carriers I B V Resistance changes with the magnetic field orientation anisotropic magneto resistance (AMR)

Magnetic semiconductors Gold contacts Channel Magnetic semiconductors Gold contacts Channel

Devices… My device fabricated on a Ga. Mn. As 1. Layout designed with Auto. Devices… My device fabricated on a Ga. Mn. As 1. Layout designed with Auto. CAD 2. Fabrication 50 m metal evaporation, etching, electron beam lithography 3. Measurements

Clean rooms Clean rooms

Processes Processes

Measurements Cryostat very low temperature Liquid helium inside Measurements Cryostat very low temperature Liquid helium inside

Measurements Screen of the parameter analyser Measurements Screen of the parameter analyser

Measurements Data looks like this… Measurements Data looks like this…

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