Question

(a) The band theory of solids can be used to qualitatively explain the difference in electrical conductivity between metals, semiconductors and insulators. Assume a pure solid with no impurities added and answer the following questions. ) What do the energy bands represent in a solid. (ii) What is the relationship between these bands in the solid and the quantum levels of electrons in an individual atom? (iii) Use sketches to show how the energy band structure of conductors, semiconductors and insulators will differ. (iv) Write down an expression for the electrical conductivity of a material and define all the variables in your equation. (v) Now use your equation from (iv) and the sketches of band structure from (iii) to explain the differences in electrical conductivity between metals, semiconductors and insulators.

Answer 1

of a solid determine The energy bands structure whether it is a conductor, an semiconductor. insulator, or are The atoms in every solid not just im metals 80 valence near one another that thair eletson wave function overlap. & thean atoms " The greater the number of interacting the greater the numbel of level produced by the mixing of respective valence wave function. In solid because the splitting is into marry level there their respective valence ware hinction. due to to many atony atoms present the levels are close together that they form energy band that consists of virtually continuous spread OF permitted energies. The energy bands OF solid, the gaps between them, and the extent to which they ane hilled by eletrons mot soly govem the eletrical behavr OF the solid but also have important bearing other of its its properties. so on a Feel free to conite comment give thumbs

Enefort Insulator Metal Semiconductor => schematic bands for eletion occupancy of allowed energy insulator, metal, semimetal and Semiconductor an → The box indicates the allowed the shaded areas indicates energy regions. the regions killed will eletrons. In pune insulator semiconductor (silicon) at absolute becomes an zenu. 4 formula 6- me ? ? m where - Conductivity eletron charge na number of atoms. = time period between two sussesive collision. ma mass of er unit : (ohm.cm) T =