文档介绍：Electronic Materials
Silicon Age: Pervasive technology
• Communications
• Computation
• Automation
• Defense
•………..
Factors:
• Reproducibility/Reliability
• Miniaturization
• Functionality
• Cost
•…………..
© . Tuller-2001 1
What Features Distinguish Different Conductors?
• Magnitude: varies by over 25 orders of magnitude!
• metal; semiconductor; insulator
• Carrier type:
• electrons vs ions;
• negative vs positive
• Mechanism:
• wave-like
• activated hopping
• Field Dependence:
• Linear vs non-linear
© . Tuller-2001 2
1
How Do We Arrive at Properties That We Want?
• Crystal Structure:
• diamond vs graphite
• Composition
• silicon vs germanium
• Doping
• n-Si:P vs p-Si:B
• Microstructure
• single vs polycrystalline
• Processing/Annealing Conditions
•Ga1+xAs vs Ga1-xAs
© . Tuller-2001 3
What is the Application?
• Interconnect • Thermistor
• Resistor • Piezoresistor
• Insulator • Chemoresistor
• Non-ohmic device • Photoconductor
– diode, transistor • oresistor
© . Tuller-2001 4
2
Origin of Conduction Range of Resistivity
Why?
© . Fitzgerald-1999 5
Response of Material to Applied Potential
I
I V=f(I)
Linear,
Rectification,
Ohmic
Non-linear, Non-Ohmic
V R
V
e-
V=IR
Metals show Ohmic behavior microscopic origin?
© . Fitzgerald-1999 6
3
Microscopic Origin: Can we Predict Conductivity of Metals?
• Drude model: Sea of electrons
– all electrons are bound to ion atom cores except valence electrons
– ignore cores
– electron gas
Schematic model of a crystal of sodium
metal.
From: C. Kittel, Introduction to Solid State Physics, 3rd
Ed., Wiley (1967) p. 198.
© . Fitzgerald-1999 7
Does this Microscopic Picture of Metals Give us Ohm’s Law?
E
F=-eE
F=ma v,J,σ,I
m(dv/dt)=-eE
v =-(eE/m)t t
E
t
Cons