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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 (CuZn) © 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 Glut3m ln [af‘ir II/(‘ it; ,  L 3“ “fﬂr'. afar“ of 0" dr{{FfFrl{ rtfl‘nilyf ﬂuid1"?” 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" (stairQ I15:If’glanr ﬂf' l # Fr‘ , I " ' 1’0 4: bﬂLIrILIQ‘r , Tlt( ping“, HIinr ff Lofflha; (ﬁ— A:{{p('ﬂf oripﬂfq +r9'ﬂ; magFf “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
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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...
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#06 mm 15) Determine the atomic packing factor for a simple cubic crystal. (5) Inn 0’" uhi‘f gigca? (Kiow : $31!"? 5'41 (of cm ii (If; :. r?
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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 (wallow41:11: 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
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a 5. Main/J7 Vl/iii In(i'€q)( Whﬂi i
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 Spring '09
 MALLIARAS

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