1. 부산대학교 재료공학부 계면공학 연구실 [Electrical Properties] 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 vibrationImpurity effect Temperature effect

2. 부산대학교 재료공학부 계면공학 연구실  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).electric current electric charge Greek letterrho  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.electric currentsigmakappagamma  = n e  = 1/   Electrical conductivity  ; n: carrier density  : mobility e: electronic charge [Electrical Properties] Chap. 4. Electrical Properties

3. 부산대학교 재료공학부 계면공학 연구실  Classification of materials: Conductor / Semiconductor / Insulator Eg = Energy gap Eg * Superconductor *Dielectric [Electrical Properties]  ( T ) = n e  Chap. 4. Electrical Properties

4. 부산대학교 재료공학부 계면공학 연구실  Path of Carriers(electrons and ions) flow? Electrons flow in the conducting mass[generally in the wire(solid)]. Ions flow in the solution (electrolyte). [Electrical Properties] Chap. 4. Electrical Properties

5. 부산대학교 재료공학부 계면공학 연구실  Concept of electrical resistivity(  ) in Bulk materials [Electrical Properties] Chap. 4. Electrical Properties

6. 부산대학교 재료공학부 계면공학 연구실  Concept of electrical resistivity(  ) in Bulk/Thin Film  Sheet resistance: by 4 point probe measurement: Rs = 4.53 x V/I (ohm/sq),  = Rs x t (ohm x cm)) for thin film Substrate [Electrical Properties] Chap. 4. Electrical Properties

7. 부산대학교 재료공학부 계면공학 연구실  4 point probe measurement: [size effect and thickness effect] Rs = 4.53 x V/I (ohm/sq),  = Rs x t (ohm x cm)) for thin film [Electrical Properties]   /t = Rs Chap. 4. Electrical Properties

8. 부산대학교 재료공학부 계면공학 연구실  Anisotropic properties of electrical resistance:  Fiber: conductor (Ag wire)  Matrix: insulator (polymer) [Electrical Properties] Chap. 4. Electrical Properties

9. 부산대학교 재료공학부 계면공학 연구실  Hall [effect] measurement for semiconducting thin film [Electrical Properties] What is hall voltage (V H )? [Fleming’s Left Hand Rule] / I have force V H = -lel  Ex R = V H /[Bx Jx], R = -[  Ex]/Jx =  /  = -1/  lel ** Sign of Hall coefficient R depends on Hall voltage ** Chap. 4. Electrical Properties

10. 부산대학교 재료공학부 계면공학 연구실 [Drift velocity] [Hall voltage] Thermal velocity Chap. 4. Electrical Properties

11. 부산대학교 재료공학부 계면공학 연구실  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. insulatorpolarizedelectric field conductor Q = C x V In capacitor [Dielectric Properties] Chap. 4. Electrical Properties

12. 부산대학교 재료공학부 계면공학 연구실  How about electrical conductance of ionic materials, ceramics and polymers in view point of major carriers In metal In electrolyte A conjugated system has a region of overlapping p-orbitals [OLED] [Complex Properties] Chap. 4. Electrical Properties

13. 부산대학교 재료공학부 계면공학 연구실 [Homework #4] / Due date: before next class 1. What is superconductor and describe its major application. 2. What is dielectric and describe its major application. 3. What is conducting polymer and describe its major application. 4. Describe a change of electrical resistivity for metals and semiconductors when a temperature is increased. 5. Describe the Hall effect in view point of measuring electrical conductivity, mobility and carrier density for thin semiconductor. Chap. 4. Electrical Properties