EMS172L_Lab03_Semiconductors

EMS172L_Lab03_Semiconductors - UC Davis EMS 107L...

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UC Davis – EMS 107L Electronic, Magnetic, and Optical Properties Laboratory – Prof. Ricardo Castro 1 UNIVERSITY OF CALIFORNIA, DAVIS Department of Chemical Engineering and Materials Science EMS 172L: Electronic, Magnetic, and Optical Properties Laboratory Laboratory Class III – Semiconductors Semiconductors are neither good conductor nor isolators, they are in between them and have their properties strongly dependent on the composition and, specially temperature. The properties of semiconductors may be explained considering the band theory. We will briefly introduce it here (please do a better job in your report using the skills you’ll have from the lecture part). To understand the band theory you should remember the structure of an atom, with the electronic orbital around the nucleus. Around an atom, an electron can only have specific energies (energy levels). These levels are separated by gaps of energy, and an electron can only change a level if enough “quantisized” energy is provided. When atoms come together, as in a crystal, the electronic orbitals start to overlap. This will create a larger number of slight different energies since electrons must not have the same set of quantum numbers. Therefore, what were isolated levels, become bands (see figure above). Sometimes, these bands overlap each other partially or completely. This will give rise to the so called conductor, semiconductor and isolator behaviors. The
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This note was uploaded on 05/14/2010 for the course EMS 172L taught by Professor R.castro during the Spring '10 term at UC Davis.

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EMS172L_Lab03_Semiconductors - UC Davis EMS 107L...

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