Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 8M

Year: May 2014

Formation of energy bands:-

• In case of a single atom, there is a single energy for an electron orbit.

• However, when two atoms are brought close to each other, it leads to intermixing of electrons in the valence shell.

• As a result, the number of permissible energy levels are formed, which is called an energy band.

Conductor:

• In case of a conductor, valence band and conduction band are very near or even overlap.

• Thus,an electron can easily jump from valence band to conduction band.

Insulator:

• In case of an insulator, the band gap is much larger than the energy supplied to excite an electron under normal temperature.

• As a result, an excited electron instantaneously loses energy and returns into the valence band

Semiconductor:

• In a semiconductor, the gap between the valence band and conduction band is just enough to excite an electron to conduction band.

• With adequate amount of energy supplied, a current can be produced in a semiconductor.