MATS 3011 Lecture Notes - Electronic Band Structure, Valence Electron, Covalent Bond
Document Summary
When you have 2 separate atoms, have up to 3p states Band structure depends on (graph of bands with increasing energy) Nature of bonding (covalent, ionic, van der waals) For real material, band structures are really complicated. 2 critical characteristics of the band structures are: Fermi dirav distribution: density of states (dos, occupation of the states. Take deltae of a certain portion of band structure this = eqn for density of staes. Graph on most right = electron density @ 0 k. If increase t, density of states doesn"t changethat depends on structure, bonding, etc. If fermi energy is inside the allowed and --> it"s a metal. If not lying w/in band, but now in bandgap --> semiconductor or insulator (if bandgap too big, then insulator, if less than 4 ev, it = semiconductor) Ec - ef > kt ----> (ec - ef )/(kt) > 1. ---> there is certain probability of finding electrons at conduction band.