{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

L13 - SUMMARY FROM LAST CLASS Conductivity n is the number...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Dr. P. Lucas U of A MSE 110 Conductivity SUMMARY FROM LAST CLASS n is the number of charge carriers (electrons) per unit volume (m -3 ). e is the charge of the electron (1.6x10 -19 C). μ is the mobility of the electron. Metals have high n but low μ , semiconductors have high μ but low n and insulators have n =0. The mobility μ of an electron moving in a solid is finite due to collision with structural defects and vibrating atoms. Vibrations amplitude increases with temperature hence the conductivity of metals decrease with increasing temperature. µ σ ne = = kT E N n g c 2 exp In semiconductors, the number of charge carrier n increase with increasing temperature according to: hence the conductivity of semiconductors increase with increasing temperature . In semiconductors both the electron and holes contribute to the conductivity: σ =n h h + n e e
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Dr. P. Lucas U of A MSE 110 Crystals: CRYSTALLINE STRUCTURE Evidently this can only be achieved by assuming a highly ordered structure characterized by regular arrays of atoms. If the crystal can grow freely without confinement, the internal order is reflected by the external macroscopic appearance of the crystal For all type of solids, metallic, ionic, covalent and molecular, the bonding energy is maximum at a specific equilibrium bonding distance r o . A system of atoms or molecule interacting together to form a solid will therefore attempt to maximize its total bonding energy by all adopting the same equilibrium distance.
Image of page 2
Dr. P. Lucas U of A MSE 110 Packing of atoms: In other words, the atoms tend to fill the available volume with high efficiency, they maximize the packing density. CRYSTALLINE STRUCTURE A B C When the atoms or molecule do not favor bonding in any particular direction like elemental metals or ionic compounds, the atoms behave as hard sphere.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern