chex42_hw1_s2003

chex42_hw1_s2003 - UNIVERSITY OF CALIFORNIA SANTA BARBARA...

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UNIVERSITY OF CALIFORNIA SANTA BARBARA DEPARTMENT OF CHEMICAL ENGINEERING CHE 142 and ChE 242: Microelectronics Processing Spring 2003 Homework # 1 (Due April 16, 2003) 1) Neatly draw the atomic configurations of the {111}, {100} and {110} planes of Si. Show these planes on the diamond structure and calculate their atomic densities in # of Si atoms/cm 2 . 2) Using the lattice constants as a starting point, calculate the atomic density of Si. Also, calculate the density (in g/cm 3 ) of Si and GaAs compare your answer to published values. 3) Calculate the Si-Si bond length and the angle between the two Si-Si bonds. 4) When a piece of Si crystal is cleaved across the (100) surface it looks like the projection you drew in question 1. However, this configuration is high energy and unstable. When you answer parts (a) and (b) of this question you will find out why. The surface reconstructs by forming Si-Si bonds (dimers) to reduce the dangling bond density on the surface. The reconstructed surface looks like Figure 1 where you can clearly see the rows of dimers. This surface is called the Si(100)-(2x1) surface because the unit cell required to generate the surface is a rectangle that has sides 2a x 1a where a × a × a are the dimensions of the Si diamond lattice unit cell. (a) How many dangling bonds per Si atom are there on the unreconstructed surface?
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chex42_hw1_s2003 - UNIVERSITY OF CALIFORNIA SANTA BARBARA...

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