HW8_MS115a

HW8_MS115a - measured and behaves as shown to the right....

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MS 115a, Problem Set #8 assigned 11/17/11 due 11/23/11 1. Explain why nonstoichiometric III-V compounds (where III implies Al, Ga or In and V implies P, As or Sb) are typically extrinsic semiconductors. 2. The resistivity of pure iron at 1 K is 0.0225 and at 273 K is 8.57 10 -6 cm. When alloyed with 5 wt % nickel, the resistivity of alloy at 273 K is 18.7 10 -6 cm. Estimate the resistivity of an alloy with 15 wt % nickel at 273 K. 3. The Fermi energy of lithium is 4.72 eV (at T = 0). (a) Calculate the number of conduction electrons per unit volume in lithium. (b) Compare this to the value implied by the crystal structure, BCC with a = 3.490 Å. 4. The resistivity of pure copper is 1.72 10 -6 cm (273 K) and its Fermi energy 7.02 eV. (a) Estimate the electron mobility, (b) estimate the time between electron scattering events, (c) estimate the velocity of the electrons with (kinetic) energy E F , (d) estimate the mean free path between scattering events. 5. The electrical conductivity of a p- type semiconductor has been
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Unformatted text preview: measured and behaves as shown to the right. The numbers on the plot indicate the slope of ln( ) vs. 1/T. Label the regions of this graph. Draw a schematic band diagram for this material in the form of E vs. N (E). Indicate as many energy terms as you can (in units of eV). 6. The phase diagram of H 2 O is shown to the right. a) For T 1 = -5C plot schematically G solid , G liquid and G vapor as functions of P. b) Do the same for T 2 = 10C. c) What is G P T N i ,{ } ? pressure, atm temperature, C-1C, 0.05atm-10 10 20 liquid solid vapor 7. Show that the entropy (per mole) due to mixing of A and B atoms is given by S mix = -RX A lnX A- RX B lnX B . a) Begin with the statistical definition of entropy, S = k b ln , b) Compare the entropies of the mixed and unmixed solutions (having N o atoms) c) Use Stirlings approximation, ln(N!) ~ Nln(N) N for large N, to evaluate S d) Note the relationship between k b , R and N o ....
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This note was uploaded on 01/03/2012 for the course MS 115a taught by Professor List during the Fall '09 term at Caltech.

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HW8_MS115a - measured and behaves as shown to the right....

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