Chap. 4. Electrical Properties
Electrical properties
are the physical conditions that allow an electrical charge to move from atom to atom in a specific material.These properties differ greatly between the three major types of materials: solids, liquids and gases.
Temp. Content (%)
Thermal vibration Impurity effect
Temperature effect
Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter ρ (rho).
Electrical conductivity or specific conductance is the reciprocal of electrical resistivity, and measures a material's ability to conduct an electric current. It is commonly represented by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) or γ (gamma) are also occasionally used.
σ = n e µ = 1/ ρ
Electrical conductivity σ ;
n: carrier density µ: mobility
e: electronic charge
Chap. 4. Electrical Properties
Classification of materials:
Conductor / Semiconductor / InsulatorEg = Energy gap
Eg
* Superconductor *Dielectric
σ(
T) = n e µ
Chap. 4. Electrical Properties
Path of Carriers(electrons and ions) flow?
Electrons flow in the conducting mass[generally in the wire(solid)].
Ions flow in the solution (electrolyte).
Chap. 4. Electrical Properties
Concept of electrical resistivity(ρ) in Bulk materials
Chap. 4. Electrical Properties
Concept of electrical resistivity(ρ) in Bulk/Thin Film
Sheet resistance: by 4 point probe measurement:
Rs = 4.53 x V/I (ohm/sq), ρ = Rs x t (ohm x cm)) for thin film
Substrate
Chap. 4. Electrical Properties
4 point probe measurement: [size effect and thickness effect]
Rs = 4.53 x V/I (ohm/sq), ρ = Rs x t (ohm x cm)) for thin film
ρ/t = Rs
Chap. 4. Electrical Properties
Anisotropic properties of electrical resistance:
Fiber: conductor (Ag wire)
Matrix: insulator (polymer)
Chap. 4. Electrical Properties
Hall [effect] measurement for semiconducting thin film
What is hall voltage (VH)?
[Fleming’s Left Hand Rule] / I have force
VH = -lel µ Ex
R = VH/[Bx Jx], R = -[µEx]/Jx = µ /σ = -1/η lel
** Sign of Hall coefficient R depends on Hall voltage **
Chap. 4. Electrical Properties
[Drift velocity]
[Hall voltage]
Thermal velocity
Chap. 4. Electrical Properties
A dielectric material (dielectric for short) is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization.
Q = C x V In capacitor
Chap. 4. Electrical Properties
How about electrical conductance
of ionic materials, ceramics and polymers in view point of major carriersIn metal
In electrolyte
A conjugated system has a region of overlapping p-orbitals
[OLED]
