hw10sol - s The donor concentration in germanium is 2.88 10...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
3.091 Fall Term 2004 Homework #10 solution outlines 1. Assume steady state. J =− D c x ; ∴∆ x = D c J = 3.091 × 10 4 cm 2 s × 1.5 × 10 19 atom cm 3 10 3 mol cm 2 hr × 1hr 3600 s × 6.02 × 10 23 atom mol = 2.773 × 10 –2 cm 2. A solution to Fick’s second law for the given boundary conditions is: c c s = 1 erf 2 x Dt , from which we get erf 2 x Dt = 1 0.018 = 0.982 From the error function tables 0.982 is the erf of 1.67. This means that 0.002 2 Dt = 0.001 Dt = 1.67 D = 286 10 5 8.314 1253 0 e D = 13 6 . 4 5 1 0 2 cm sec t = 0.001 2 = 5.56 10 5 sec = 6.4 days 1.67 2 6.45 10 13 3. C s C c × = erfc x = erfc 31 0 3 = erfc (2.083) c s 2 Dt 2 Dt c = 1 erf (. . 2 083), 1 c = 0 9964 c c s s 1 6 3 c = 36 × 10 3 , c = 2 88 × 10 c m
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: s The donor concentration in germanium is 2.88 10 16 /cm 3 . 3.091 Fall Term 2004 Homework #10 Solution Outlines page 2 ( , c x = 5 10 16 = c erfc 25 10 4 4. c x t ) = c erf x = c erfc s s s 90 2 Dt s 2 Dt 2 7.23 10 9 60 c = 5 10 16 = 6.43 10 16 cm 3 s 25 10 4 erfc 2 7.23 10 9 5400 erfc(0.20) = 1 erf(0.20) = 1 0.2227 = 0.7773 5. c o /3 O x c o c ? c x t ) = c 0 e r f x ( , 2 Dt What is x when c = c o /3? x x c 0 = c 0 erf 0.33 = erf ; erf (0.30) = 0.3286 0.33 3 2 Dt 2 Dt x 2 10 = 0.30 x = 0.30 3.091 10 6 60 = 2.58 10 2 cm = 258 m 2 Dt...
View Full Document

This note was uploaded on 11/02/2009 for the course CHEMISTRY 3.091 taught by Professor Donsadoway during the Fall '04 term at MIT.

Page1 / 2

hw10sol - s The donor concentration in germanium is 2.88 10...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online