2011_Chapter_4_Exam_Practice_problems

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Unformatted text preview: ergy with a dashed line and label as EF Label the typical band gap (eV) for materials where the Fermi energy sits in the bandgap. Shade states filled at 0 Kelvin. f) (4 pts) Sketch the band diagram for an insulator. Give an example of a material that is an insulator. g) (4 pts) Sketch the band diagram for a metal. Give an example of a material that is a metal. h) (4 pts) Sketch the band diagram for a semiconductor. Give an example of a material that is a semiconductor. Problem 4 – Multiple Choice Roundup [____/42 pts] Each question below is worth 3 points. 1. The bond energy between two atoms in a solid forming a diatomic molecule depends on: a. the number of valence electrons in the two atoms b. the distance between the atoms c. a and b d. neither a nor b 2. The probability of occupation at the Fermi energy in a metal is: a. 0 b. 0.25 c. 0.75 d. 0.5 3. The kinetic energy of an atom or molecule in an ideal gas in 3D is: a. kBT b. less than total energy c. equal to total energy d. 1/2 kBT 4. How many valence electrons are there in 1 cm3 of silicon (Si)? a. 5x1022 b. 1x1010 c. 1x1016 d. 2x1023 Problem 5 – A Few Quick Questions on Bonding… [____/12 pts] a) Choose an element from the periodic table to alloy with the one given in order to make a semiconducting material with the valence band exactly full at 0 K. [2 pts] In [2 pts] Zn [2 pts] Si ________ ________ ________ (must choose an element other than Si for this one) 2) [6 pts] Earlier this semester, we studied bonding and learned that the equilibrium distance between two atoms is determined by the minimum of the total energy vs. distance curve. Explain in a few sentences based on the material in Chapter 4 what provides the attractive energy (lowering of the total energy) for covalent bonding such as Si‐Si bonds....
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