Midterm_2620_2009_midterm solutions

Midterm_2620_2009_midterm solutions - Name ' g MSE 2620...

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Unformatted text preview: Name ' g MSE 2620 Midterm 2009 Circle T or F indicating whether the statement is true or false. 3 points each 1) Metals have higher conductivities than semiconductors primarily because they have higher mobilities. T @ 2) The conductivity of both metals and intrinsic semiconductors decreases with increasing temperature. T @ 3) Two copper pieces of the same purity but of different dimensions will have different resistivities. T F 4) BCC is a close packed structure. T 5) Smaller grains improve electronic conductivity for metals. T F 6) At UK there are no electrons in the conduction band of both extrinsic and intrinsic semiconductors. C9 F 7) All atoms at a certain temperature have the same KE. T ('9 8) Pure copper conducts electrons better than Brass (Cu-Zn) © F 9) n*p=n[2 only holds true for intrinsic semiconductors. J, T (a 10) The kinetics energy of electrons at RT in a semiconductor is ‘f‘0 eV. Answer each question within 50 words. 5 points each 11) Give an example and a short description of each type of defect: 0d, 1d, 2d. Oi‘fl Vacant? —m:j5‘:fl9 Glut-3m l-n [af-‘ir II/(‘ it; , - L- 3“ “fflr'.- afar“ of 0" dr{{FfFrl{ rtfl‘nilyf fluid-1"?” 17" 531 I SI”: '. “l i} {'ng " an (1.1 T r-,.-, 'f "I .' In {It-*3}. l/Fr'r" 1 “If yr r i" 0~ {at ,, . J j!" , 5C H/I d -} focgi'mn I 01" (stair-Q I15:If’glanr flf' l #- Fr‘ , I " '- 1’0 4: bflLIr-ILIQ‘r ,- Tlt( ping“, HI-inr ff Lofflha; (fi— A:{{p('flf oripflfq +r9'fl; mag-Ff “Hr-{fut J" +£tf 1f!” W‘J‘rfifiath 12) Name the three major types of bonding in solids and give an example of a material for each one. MN’JIEL "'Cot COL/ale“; ,.. g " Iomlc* 13) Describe Matthiessen’s rule. 14) Describe the difference between Nc and the actual density of state at the conduction band. M; 'u an agricultmflan if *4! afthji‘fy erg f‘l‘afo Where: H CL +11( {Tafef are quarried +- be cd‘ ‘Hu' loam“ 50532. TA< CU {OIIH‘I‘S Cmdafi‘faa arf‘td/ day-(fir OF f-{q‘fes tic!“ E... {(7 c2 #06 mm 15) Determine the atomic packing factor for a simple cubic crystal. (5) Inn 0’" uhi‘f gig-ca? (Kiow- : $31!"? 5'41 (of cm ii (If; :. r? LIL For ? " 3m” _ if: ,n 3(3 16) Atomic Bonding (10) a. Sketch potential energy as a function of interatomic distance per ion pair in solid NaCl. PE i’f’flub‘m ‘ Pa hi I} E¥C{V’Jl.my Ct {iratHI/e (wallow-41:11: E,r(€ b. Label the areas of attractive and repulsive force and explain the physics behind each region. c. Label the equilibrium distance as r0 and sketch on the diagram what happens to this distance as you increase temperature. 17) Find the resistance of the following sample (5) A is a square with length 10um and conductance of 4.0 X105 {Tim1 B is a square with length Sum and conductance of 5.0 )(105 Q'lm‘l C is a square with length Burn and conductance of 6.0 X105 Q'lm‘1 err-«:1.- 18) Sketch Inln) as a function of 1fT(K} for the following two samples on the same graph. Label all slopes and the carrier concentration at relevant points. (No need to label temperatures) (15) ' Ionization Energy (meV} — a. A piece ofSi with [Be]=1x1015 m3 b. A piece of Ge with [P]=Ei)<1015 cm”3 and [Be]=1><1015 cm‘3 9L) 5’2 '«aa dwelt Queplar ‘10ch lmnégf’f of flu fem, 13W. WI 30 Glenda: 1140!”:‘1'HJ’I 1:) '1~ my [:03 —;.£&J=~_ Ho's“. 19] (15) Tim diagram balm: shows an r:de Hlnl! email; “we. *Fhe frmll at“ the. stamina has a positive pawlnitlii with malice! tn the back side at‘ the sample. measured Hall 1 a. In what directions will holes be deflected by the magnetic field? “*2 b. In what direction will electrons be deflected by the magnetic field? c. How would the Hall voltage {become larger, smaller, or stay the same) change for an intrinsic semiconductor if we increase the temperature of the sample. Give justification for ouranswer. - ' gale Palm" Thu: from “He «Laetitia/t RH: flu M Wm {,WM S] n ,Mm ( jay} . lnfi( ‘Ui go by mutilinrfeqqu d. How would the Hall Voltage and the voltage between 1 and 2 change if we suddenly increased the carrier mobility in the sample? Give justification for your answer agqtn i / {fl 1-. i I a 5. Main/J7 Vl/iii In(i'€q)( Whfli i "‘ fur ,_ '3 may; Rear” L, ...
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Midterm_2620_2009_midterm solutions - Name ' g MSE 2620...

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