MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Electrical Engineering and Computer Science Department of Materials Science and Engineering 6.152J3.155J IN-CLASS QUIZ 16 September 2002 (5 problems/9 pages total) 1)Defects(20 points) The equilibrium concentration of oxygen in Si is given by Cox=5x 10exp(-2.6eV/kBT)(cm")and that for vacancies is given by CVAC =2 x 10exp(-1.06 eV/kBT(cm). Recall kB=8.62 x 10eV/K a) At what temperature are Cvac and Cox equal? b) Which defect, oxygen impurities or vacancies, would have a greater equilibrium concentration at the melting temperature(1417C)of Si?Name: ___________________________ MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Electrical Engineering and Computer Science Department of Materials Science and Engineering 6.152J/3.155J IN-CLASS QUIZ 16 September 2002 (5 problems/9 pages total) 1) Defects (20 points) The equilibrium concentration of oxygen in Si is given by COX = 5 × 1022 exp (-2.6 eV / kBT) (cm-3) and that for vacancies is given by CVAC = 2 × 1022 exp (-1.06 eV / kBT) (cm-3). Recall kB = 8.62 x 10-5 eV/K. a) At what temperature are CVAC and COX equal? b) Which defect, oxygen impurities or vacancies, would have a greater equilibrium concentration at the melting temperature (1417 °C) of Si? 1