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Applet Tutorial

• On the left hand side, the Fermi function f(E) is plotted. On the right hand side, discrete states (localized states) are shown. For E > EF, f(E) approaches zero. This means that the energy states are vacant (no electron occupies the state). For E < EF, f(E) approaches unity. This means that an energy state is occupied by an electron with certainty.
• Use mouse to drag EF up or down. Observe the electron occupying or vacating the states. The probability function f(E) is only relative to EF. EF is called the Fermi level and is the central parameter in deciding the number of electrons at a given energy E.
• Change the Temperature using the scroll bar at the bottom of the applet. Observe its effect on f(E) and on the electron distribution. At a higher T, the electron distribution is more gradual: the electron number changes more slowly with E. This is because the higher thermal energy kT promotes more electrons from lower states to higher states.