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semiconductor

Discussion in 'Electronic Basics' started by achhu, Jun 6, 2006.

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  1. achhu

    achhu Guest

    can anybody explain the fundamentals of energy bands in materials (
    like a professor not like a lecturer, plz dont mind).
    i gone through the topics but every time confused. plz help me.
     
  2. Tim Williams

    Tim Williams Guest

    Energy required to bump an electron loose from an atom in a solid, no?

    In a crystalline solid, you have a lattice of atoms bonded to other atoms.
    Electrons form the bonds because some atoms give up electrons, while others
    accept them. Obviously, a pure solid must do both for each atom,
    simultaneously donating and accepting electrons to form a bond to another
    atom of the same type.

    In a solid like diamond, the carbon atoms hold the electrons tightly and
    they can't move, resulting in an insulator. In a solid like copper, by a
    quirk of the electric structure, roughly one electron per atom (??) is
    particularly able to move between atoms, with no real preference for being
    stuck to a given atom, resulting in a good conductor. In a solid like
    germanium or silicon, the electrons are bound with a certain energy, but
    thermal energy at room temperature is enough to kick a few, making a
    semiconductor.

    Thus, the binding energy of electrons versus the energy they are able to get
    (such as by an applied electric field, thermal motion, or incident light)
    determines whether or not a solid is conductive or insulating. How
    insulating, then, depends on the binding energy, which as far as I know is
    called the band gap.

    How's that? Or do you want to be more specific, about energy bands and
    diagrams of them and band gap and fermi level and such?

    Tim
     
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