Introduction to Inorganic Chemistry/Electronic Properties of Metals, Superconductors, and Semiconductors
Chapter 10: Electronic Properties of Materials: Superconductors and Semiconductors edit
10.1 Metal-insulator transitions edit
10.2 Superconductors edit
10.3 Periodic trends: metals, semiconductors, and insulators edit
10.4 Semiconductors: band gaps, colors, conductivity and doping edit
10.5 Semiconductor p-n junctions edit
10.6 Diodes, LED's and solar cells edit
10.7 Amorphous semiconductors edit
10.8 Discussion questions edit
10.9 Problems edit
1. The structure of a high temperature superconductor containing barium, europium, copper, and oxygen is shown at the right. What is the stoichiometry of the compound? This structure is actually closely related to perovskite, ABO3. Mark the positions of the missing atoms that would be found in a perovskite.
2. VO2 can exist in insulating or metallic form, depending on temperature and pressure. Which form would be stabilized by increasing the pressure? Explain your answer.
3. Offer a brief explanation of why bandgaps for octet p-block semiconductors (1) decrease with increasing average principal quantum number, and (2) increase with increasing electronegativity difference.
4. Indicate the type of conduction (n or p) in the following: (a) Zn-doped GaAs, (b) In1+xAs1-x, where x << 1, (c) Li0.05Cu0.95O, (d) WO2.999
5. Using 1 eV = 1240 nm, predict the colors of ZnO (Eg = 3.2 eV), AlP (2.5 eV), ZnSnP2 (2.1 eV), CdGeP2 (1.8 eV), and InP (1.27 eV).
6. Pure Ge is much more conductive than pure Si. Given their bandgaps (0.74 and 1.15 eV, respectively), estimate the ratio of their conductivities at room temperature.
7. Sketch a silicon p-n junction, showing the depletion region, band bending, and the Fermi level in the absence of light or applied potential. In the dark, the p-n junction acts as a rectifier. Which way does current flow with an applied bias? In the light, the junction acts as a photodiode. Which way does current flow in this case?