1. Introduction to Materials Science and Engineering
Chapter 10: Electrical Properties
Textbook Chapter 19

2. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

3. Introduction ISSUES TO ADDRESS...
• How are electrical conductance and resistance
characterized?
• What are the physical phenomena that distinguish
conductors, semiconductors, and insulators?
• For metals, how is conductivity affected by
imperfections, temperature, and deformation?
• For semiconductors, how is conductivity affected
by impurities (doping) and temperature?

4. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

5. View of an Integrated Circuit
• Scanning electron microscope images of an IC:
• A dot map showing location of Si (a semiconductor):
--Si shows up as light regions.
• A dot map showing location of Al (a conductor):
--Al shows up as light regions.

6. Electrical Conduction
Ohm’s Law

7. Electrical Conductivity

8. Important Unit

9. Electronic vs. Ionic charge carrier electron (e=1.602x10-19 C)
electron/hole
cation
anion

10. Energy Band:

11. Band Structure of Solids
Valence band
- The energy levels filled by electrons in their lowest energy states.
Conduction band
- The unfilled energy levels into which electrons can be excited to provide conductivity.
Holes
- Unfilled energy levels in the valence band. Because electrons move to fill these holes, the holes move and produce a current.
Energy gap (Bandgap)
- The energy between the top of the valence band and the bottom of the conduction band that a charge carrier must obtain before it can transfer a charge.

12. Energy Band

13. Formation of Energy Band

14. Energy Band of Na

15. Metal, Semiconductor, Insulator
Metal Insulator Semiconductor
Ex) Cu (3d104s1) Mg(3s2) > 2eV < 2eV

16. Energy band for Conductor

17. Conduction in terms of Band and Atomic Bonding Models
metals
insulators and semiconductors

18. Electron Mobility
Drift Velocity

19. Electron Mobility
conductivity
For metals

20. Electrical Resistivity of Metals
thermal scattering
impurity scattering
defect scattering

21. Electrical Resistivity of Metals
temperature
impurities

22. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

23. Semiconductor
Intrinsic semiconductor - A semiconductor in which properties are controlled by the element or compound that makes the semiconductor and not by dopants or impurities.
Extrinsic semiconductor - A semiconductor prepared by adding dopants, which determine the number and type of charge carriers.
Doping - Deliberate addition of controlled amounts of other elements to increase the number of charge carriers in a semiconductor.
Thermistor - A semiconductor device that is particularly sensitive to changes in temperature, permitting it to serve as an accurate measure of temperature.
Radiative recombination - Recombination of holes and electrons that leads to emission of light; this occurs in direct bandgap materials.

24. Intrinsic Semiconductors

25. Intrinsic Semiconductors

26. Intrinsic Semiconductors

27. Intrinsic Semiconductors

28. Intrinsic Semiconductors

29. Extrinsic Semiconductors
• Intrinsic:
# electrons = # holes (n = p)
• Extrinsic:
--n ≠ p
• N-type Extrinsic: (n >> p)
• P-type Extrinsic: (p >> n)

30. N-type Semiconductors60

31. N-type Semiconductors

32. N-type Semiconductors

33. P-type Semiconductors

34. P-type Semiconductors

35. P-type Semiconductors

36. Temperature Dependence of Mobility

37. Temperature Dependence of Mobility

38. Hall Effect
B=1kG
wc=2.8GHz

39. Hall Effect

40. Hall Effect

41. Semiconductor Devices
p-n junction

42. Semiconductor Devices
transistor

43. Semiconductor Devices
Junction transistor
MOSFET

44. Growth of Si crystal

45. IC Fabrication Process

46. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

47. Ionic Conduction
nI: charge of ions

48. Conducting Polymer temperature dependence of the conductivity
similar to that of semiconductor
polymer- semicrystalline
 require modification of band model
polyacetylene-prototype of a conducting polymer
(conjugated organic polymer-alternating single and double bonds between carbons)

49. Conducting Polymer conductivity
p-electrons in the double bond act as a carrier

50. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

51. Dielectric Capacitance Capacitance ( ,F) e0:permittivity of a vacuum
e:permittivity of the medium
er:relative permittivity
(dielectric constant)
where, e=ere0

52. Polarization
Electric dipole moment

53. dielectric displacement
Polarization
Surface charge density D, or quantity of charge per unit area is expressed as,
(C/m2)
dielectric displacement
dipole

54. Polarization
©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

55. Types of Polarization Electronic Polarization (Pe)
Ionic Polarization (Pi)
Orientation Polarization (Po)

56. Frequency Response
Dielectric Strength
Dielectric Materials

57. Content Introduction Electrical Conduction Semiconductivity
Electrical Conduction in Ionic Ceramics
and in Polymers
5. Dielectric Behavior
Other Electrical Characteristics of Materials
Electronic Devices and Fabrication

58. Ferroelectricity
BaTiO3
Rochelle salt(NaKC4H4O6·4H2O)
KH2PO4
KNbO3
PZT

59. Piezoelectricity PbZrO3 NH4H2PO4 Quartz
©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

60. Summary • Electrical conductivity and resistivity are:
-- material parameters.
-- geometry independent.
• Electrical resistance is:
-- a geometry and material dependent parameter.
• Conductors, semiconductors, and insulators...
-- differ in accessibility of energy states for
conductance electrons.
• For metals, conductivity is increased by
-- reducing deformation
-- reducing imperfections
-- decreasing temperature.
• For pure semiconductors, conductivity is increased by
-- increasing temperature
-- doping (e.g., adding B to Si (p-type) or P to Si (n-type).