In isolated atom the valence electrons can exist only in one of the allowed orbital's each of a sharply defined energy called energy levels. But when two molecules are brought close to each other, there are changes in energy levels and they spread in the form of bands.
Energy bands are of following types
Valence band: The energy band formed by a series of energy levels containing valence electrons is known as valence band. At 0 K, the electrons fulfill the energy levels in valence band starting from lowest one.
(i) This band is always fulfilling by electron.
(ii) This is the type of maximum energy.
(iii) Electrons are not capable of increasing energy from external electric field.
(iv) No flow of current because of such electrons.
(v) The highest power level which may be placed by an electron in valence band at 0 K is called Fermi level.
Conduction band: The higher power level band is known as the conduction band.
(i) It is also known as empty band of minimum energy.
(ii) This band is partially filled by the electrons.
(iii) In this band the electrons can gain energy from external electric field.
(iv) The electrons in the conduction band are called the free electrons. They are free to go anywhere within the volume of the solid.
(v) Current flows because of such electrons.
|
Forbidden energy gap (ΔEg): Energy gap between conduction band and valence band
ΔEg = (CB)min - (V.B)max
(i) No free electron placed in forbidden energy gap.
(ii) Width of forbidden power gap upon the nature of material.
(iii) As temperature increases (↑), forbidden energy gap decreases (↓) very slightly.
|
|
Email based Physics assignment help - homework help at Expertsmind
Are you searching physics expert for help with Electronics questions? Electronics topic is not easier to learn without external help? We at www.expertsmind.com offer finest service of Physics assignment help and physics homework help. Live tutors are available for 24x7 hours helping students in their Electronics related problems. We provide step by step Electronics question's answers with 100% plagiarism free content. We prepare quality content and notes for Electronics topic under physics theory and study material. These are avail for subscribed users and they can get advantages anytime.
Why Expertsmind for assignment help
- Higher degree holder and experienced experts network
- Punctuality and responsibility of work
- Quality solution with 100% plagiarism free answers
- Time on Delivery
- Privacy of information and details
- Excellence in solving physics queries in excels and word format.
- Best tutoring assistance 24x7 hours