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MatS_3011_S12_HW_2 - diamond denser than Si even though C...

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University of Minnesota Department of Chemical Engineering and Materials Science MatS 3011: Introduction to Materials Science and Engineering Spring Semester 2012 Homework #2 (Due February 8, 2012) 1) (7 pts) Is there anything wrong with Figure 2.16? If yes what is wrong and how should it be corrected? 2) (12 pts) Using the atomic radius given on the inside cover of Callister calculate the densities of lead and aluminum. What is the major difference in the densities of these metals due to? Name some applications of lead and aluminum where density is an important factor in choosing them. 3) (10 pts) Callister 3.9 4) (15 pts) Silicon is an important semiconductor used in computer chips, memory chips and solar cells. Si has the diamond cubic structure. If the Si-Si bond length is 0.235 nm, calculate the lattice constant, a, and the density of Si. Density of diamond (which also has the diamond structure) is 3.52 g/cm 3 . Calculate the C-C bond length in diamond. Why is
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Unformatted text preview: diamond denser than Si even though C is above Si in the periodic table and therefore has lower molecular weight? 5) (10 pts) GaAs is a semiconductor used in many telecommunication devices. It has the zinc blende structure. Draw the conventional unit cell for GaAs and give the coordinates of all the lattice points and the coordinates of all the Ga and As atoms. How many Ga atoms are there in the unit cell? How many As atoms are there in the unit cell? 6) (8 pts) Callister 3.30 (a)-(d) and Callister 3. 31 7) (16 pts) Callister 3. 40 8) (12 pts) Callister 3.41, 3.42 and 3.43 9) (10 pts) Picture below shows some Si wafers. Surfaces of these wafers are atomically smooth crystal planes. While you can not tell by looking at them, they are the (001) surface or the (111) surface. (There are others but these two are the most common.) Draw the atomic arrangement of these two surfaces and calculate their atomic density. The lattice constant a=0.5431 nm for Si....
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