Electrical Properties of Materials

9 Key excerpts on "Electrical Properties of Materials"

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  Materials Under Extreme Conditions

  Recent Trends and Future Prospects

  • A.K. Tyagi, S. Banerjee, A. K. Tyagi(Authors)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  10 ]. Such multifaceted approach from different disciplines of science and engineering led to dramatically enhanced capacity of known materials and discovery of newer materials. For example, the current carrying capacity of a conductor is the backbone for civilization in terms of producing current inside a power generator and transmitting power from generator to the end use, as well as governing the speed and size of motors, etc. In addition to these normal electrical applications, the size and performance of electronic components in integrated circuits are also based on the materials' properties.

  The Electrical Properties of Materials are characterized in a number of ways, and most commonly explained terminology is based on resistance (R ), which means the extent of opposition a material exhibits to the flow of electrical current, i.e., the flow of charge carrier, which may be electron (e ), hole (h ), or ions under the influence of electrical field. The fundamental quantity of material, defined as a term resistivity, ρ   =  R   ×  (l /A ), where R , l , and A are resistance, length, and area of cross-section of the conductor, is in general used to explain its electrical property. Broadly, materials exhibiting conductivity (defined as σ   =  1/ρ ), 104 –106   S/cm (ρ   =  1–102   μΩ·cm) are classed as conductor , while those having conductivity (<10

  − 15

    S/cm) are classed as insulators. The term superconductors is used for materials having zero resistivity. Materials that are intermediate-level conductors are generally called semiconductors . The conductivity of materials depends on number and charge of the carrier of current as well as their mobility carrier (σ   =  n ·e ·μ , where n   =  number of carriers, i.e., carrier density, e   =  charge of the carrier, and μ is their mobility). Thus, all sorts of materials can be classed either as an insulator, semiconductor, or conductor. A more appropriate mode of classification of the electrical properties is based on the temperature dependence of electrical resistance/resistivity or their reciprocals, conductance/conductivity. It has been realized that different types of materials have some relevant applications and they either may be as current conductor, or current blocker (insulator), or as controlled conduction as in electronic circuits [3 –9

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  Materials Science and Engineering, P-eBK

  An Introduction

  • William D. Callister, Jr., David G. Rethwisch, Aaron Blicblau, Kiara Bruggeman, Michael Cortie, John Long, Judy Hart, Ross Marceau, Ryan Mitchell, Reza Parvizi, David Rubin De Celis Leal, Steven Babaniaris, Subrat Das, Thomas Dorin, Ajay Mahato, Julius Orwa(Authors)
  • 2020(Publication Date)
  • Wiley

    (Publisher)

  For example, when we consider an integrated circuit package, the electrical behaviours of the various materials are diverse. Some need to be highly electrically conductive (e.g. connecting wires), whereas electrical insulativity is required of others (e.g. protective package encapsulation). The functioning of modern flash‐memory cards (and flash drives) that are used to store digital information relies on the unique electrical properties of silicon, a semiconducting material. (Flash memory is discussed in section 18.5.) (b) Courtesy SanDisk Corporation 100 µm (a) Andrew Syred/Science Source (c) Nicholas/Getty Images (a) Scanning electron micrograph of an integrated circuit, which is composed of silicon and metallic interconnects. Integrated circuit components are used to store information in a digital format. (b) Three different flash‐memory card types. (c) A flash‐memory card being inserted into a digital camera. This memory card will be used to store photographic images (and in some cases GPS location). 18.1 Introduction The prime objective of this chapter is to explore the Electrical Properties of Materials — that is, their responses to an applied electric field. We begin with the phenomenon of electrical conduction: the parameters by which it is expressed, the mechanism of conduction by electrons, and how the electron energy band structure of a material influences its ability to conduct. These principles are extended to metals, semiconductors, and insulators. Particular attention is given to the characteristics of semiconductors and then to semiconducting devices. The dielectric characteristics of insulating materials are also treated. The final sections are devoted to the phenomena of ferroelectricity and piezoelectricity. ELECTRICAL CONDUCTION 18.2 Ohm’s law FIGURE 18.1 Schematic representation of the apparatus used to measure electrical resistivity.

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  Physical Properties of Materials, Third Edition

  • Mary Anne White(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  Part IVElectrical and Magnetic Properties of Materials

  The missing link between electricity and magnetism was found in 1820, by Hans Christian Ørsted, who noticed that a magnetic compass needle is influenced by current in a nearby conductor. His discovery literally set the wheels of modern industry in motion.

  Rodney Cotterill The Cambridge Guide to the Material World

  Passage contains an image

  12

  Electrical Properties

  12.1 Introduction

  Although all the properties of materials—optical, thermal, electrical, magnetic, and mechanical—are related, it is perhaps the electrical properties that most distinguish one material from another. This distinction can be as simple as metal versus nonmetal, or it can involve more exotic properties such as superconductivity. The aim of this chapter is to expose the principles that determine electrical properties of matter.

  12.2 Metals, Insulators, and Semiconductors: Band Theory

  The resistance to flow of electric current in a material, designated R , is determined by the dimensions of the material (length L and cross-sectional area A ) and the intrinsic resistivity (also known as resistivity , and represented by ρ) of the material:*

  R = ρ

  (

  L A

  )

   

  ( 12.1 )

  where R is in units of ohms† (abbreviated Ω) and ρ is typically in units Ω m. The intrinsic resistivity depends not just on the specific material but also on the temperature. (We will see later how the temperature dependence of resistivity can be used to produce electronic thermometers.) Some typical resistivities are given in Table 12.1 .

  TABLE 12.1 Electrical Resistivities, ρ, and Conductivities, σ (= ρ−1 ), of Selected Materials at 25 °C

  The electrical conductivity , σ, of a material is the reciprocal of its resistivity, ρ:

  σ =

  1 ρ

   

  ( 12.2 )

  so typical units of σ are Ω−1 m−1 (≡S m−1 , where S represents Siemens* and 1 S = 1 Ω−1 ). Electrical conductivity also can be equivalently expressed in terms of current density, J (units A m−2 , where A is amperes† ) and electric field, ε (units V m−1 , where V is volts‡

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  Handbook of Polymer Testing

  Physical Methods

  • Roger Brown(Author)
  • 1999(Publication Date)
  • CRC Press

    (Publisher)

  1 Synopsis 25 Electrical Properties Cyril Barry Consultant, Hay-on-Wye, Hereford, England The electrical properties of polymers that are of general interest are those related to the behavior of the polymer as an electrical insulating material. It is, however, true that such properties may be important in assessing the behavior and suitability of a material in applications that may not be electrical in nature (for example the dissipation factor may be useful to detect the presence of an unwanted contaminant in a polyolefine). These properties may be conveniently divided into two categories: 1. Those dependent on the mobility of electrically charged molecular entities (e.g., ions or dipoles) within the material. These movements do not generally lead to irrever-sible changes in the material. The important properties are volume resistivity, sur-face resistivity, insulation resistance, permittivity, and dissipation factor. 2. Those relevant to the ability of the material to withstand electrical stress without degradation leading to the loss, permanent or temporary, complete or partial, of its electrical insulating character. This group comprises mainly breakdown voltage, tracking resistance, arc resistance, and resistance to electrical discharges. An important subdivision of these categories identifies those properties that are significant in determining the behavior of the material in generating or retaining unwanted electro-static charges. These will be considered separately, for two reasons: 1. The methods may be very specialized (e.g., chargeability and charge decay). 2. The determined value of the property may be such that some experimental errors are not significant, so that a simplified procedure or lower accuracy may be acceptable (e.g., resistivity). 617 618 Barry In preparing this chapter, the aim of the author has been to provide a guide to the standardized practical methods.

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  Introduction to Engineering Materials

  • George Murray, Charles V. White, Wolfgang Weise(Authors)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  309 10 Electrical Properties of Materials 10.1 INTRODUCTION The electron conductivity of solid materials gives an almost unambiguous way to classify them. Simply put, on the basis of electrical conductivity, materials are either insulators, semiconductors, conductors, or superconductors. Superconduc-tors are a special class of materials that exhibit zero resistance below a certain temperature. They will not be considered here. The conductivity of all of the more common and widely used materials is shown in Figure 10.1. The range of conductivities is quite large. Where we draw the lines for these materials appears to be somewhat arbitrary, but we can define these three categories fairly precisely in terms of the number of electrons available for conduction. This number can be computed using the energy band structure for the valence electrons, a subject covered in the following section. Insulators and most polymers have a low conductivity because of their strong covalent bonds and the absence of free electrons, but in some polymers a conducting powder is mixed with the polymer to form a conducting composite. In a few others of the so-called conducting polymers, there exist some free electrons within the polymer structure, creating conductivity on the order of that found in crystalline semiconductors, and in some conducting polymers the conductivity approaches that of metals. There is a tremendously large variation in the conductivity of solids, being about a factor of 10 25 from conductors to insulators. Ohm’s law can be used to express conductivity and its reciprocal, resistivity, which are not functions of specimen dimensions, and the conductance and resis-tance, which are functions of specimen dimensions. Resistance is related to resistivity by: R = ρ l /A where R = resistance ρ = resistivity (usually expressed in Ω · m) l = specimen length A = specimen area and in terms of conductivity, σ , σ = l /RA units are ( Ω · m) − 1

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  Fundamentals of Materials Science and Engineering

  An Integrated Approach

  • William D. Callister, Jr., David G. Rethwisch(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  The dielectric characteristics of insulating materials are also treated. The final sections are devoted to the phenomena of ferroelectricity and piezoelectricity. 12.1 INTRODUCTION Electrical Conduction One of the most important electrical characteristics of a solid material is the ease with which it transmits an electric current. Ohm’s law relates the current I—or time rate of charge passage—to the applied voltage V as follows: V = IR (12.1) where R is the resistance of the material through which the current is passing. The units for V, I, and R are, respectively, volts (J/C), amperes (C/s), and ohms (V/A). The value Ohm’s law Ohm’s law expression 12.2 OHM’S LAW 12.3 Electrical Conductivity • 505 of R is influenced by specimen configuration and for many materials is independent of current. The electrical resistivity ρ is independent of specimen geometry but related to R through the expression ρ = RA l (12.2) where l is the distance between the two points at which the voltage is measured and A is the cross-sectional area perpendicular to the direction of the current. The units for ρ are ohm-meters (Ω∙m). From the expression for Ohm’s law and Equation 12.2, ρ = VA Il (12.3) Figure 12.1 is a schematic diagram of an experimental arrangement for measuring elec- trical resistivity. electrical resistivity Electrical resistivity— dependence on resistance, specimen cross-sectional area, and distance between measuring points Electrical resistivity— dependence on applied voltage, current, specimen cross-sectional area, and distance between measuring points Sometimes, electrical conductivity σ is used to specify the electrical character of a mate- rial. It is simply the reciprocal of the resistivity, or σ = 1 ρ (12.4) and is indicative of the ease with which a material is capable of conducting an electric current. The units for σ are reciprocal ohm-meters [(Ω∙m) –1 ]. 1 The following discussions on electrical properties use both resistivity and conductivity.

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  Nanomaterials, Nanotechnologies and Design

  An Introduction for Engineers and Architects

  • Daniel L. Schodek, Paulo Ferreira, Michael F. Ashby(Authors)
  • 2009(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  dielectric in referring to its behavior in an electric field.

  Three properties are of importance here. The first, the dielectric constant (or relative permittivity), has to do with the way the material acquires a dipole moment (it polarizes) in an electric field. The second, the dielectric loss factor, measures the energy dissipated when radio-frequency waves pass through a material, the energy appearing as heat (the principle of microwave cooking). The third is the dielectric breakdown potential; lightning is dielectric breakdown, and it can be as damaging on a small scale—in a piece of electrical equipment, for example—as on a large one.

  There are many kinds of electrical behavior, all of them useful. Figure 4.48 gives an overview, with examples of materials and applications.

  Figure 4.48 The hierarchy of electrical behavior. The interesting ones are in the darker colored boxes, with examples of materials and applications. Their nature and origins are described in this chapter.

  Resistivity and Conductivity

  The electrical resistance R (units: ohms, symbol Ω) of a rod of material is the potential drop V (volts) across it, divided by the current i (amps) passing through it, as in Figure 4.49 . This relationship is Ohm's Law:

  Figure 4.49 Electrical resistivity. Its value ranges from 1 to 10 24  µΩ⋅cm.

  (4.25)

  The material property that determines resistance is the electrical resistivity, ρ e . It is related to the resistance by

  (4.26)

  where A is the section and L the length of a test rod of material; think of it as the resistance of a unit cube of the material. Its units in the metric system are Ω⋅m, but it is commonly reported in units of µΩ⋅cm. It has an immense range, from a little more than 10 −8 in units of Ω⋅m for good conductors (equivalent to 1  µΩ⋅cm, which is why these units are still used) to more than 10 16   Ω⋅m (10 24   µΩ⋅cm) for the best insulators. The electrical conductivity κ e is simply the reciprocal of the resistivity. Its units are Siemens per meter ( S/m or ( Ω⋅m) −1

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  Materials Science in Microelectronics II

  The Effects of Structure on Properties in Thin Films

  • Eugene Machlin(Author)
  • 2010(Publication Date)
  • Elsevier Science

    (Publisher)

  Various electrical properties of thin films are vital to the efficient function-ing of many devices. For example: interconnections in integrated circuits require low resistivity; thin-film transistors require adequate charge carrier mobility and high on–off current ratio; solar cells require a high value of the minority carrier diffusion length, a low dark conductivity coupled with a high photoconductivity, and as high a short-circuit current and open circuit voltage as possible; superconducting thin films require a high critical current density; dielectric films require a high breakdown volt-age; ohmic contacts require a low interfacial impedance; etc. We will consider these electrical properties and how the structure (i.e. mostly defect structure) affects them in this chapter. As stated in the Preface, we shall not give a detailed exposition of each topic. Rather, our objective here is to provide, where possible, an understand-ing of the physical bases for the effects of structure on the electrical properties and a summary of the data that characterize these effects. 1. Conductivity and charge carrier mobility. 1.1. Metallic conductors. 1.1.1. Conducting lines (interconnections) in integrated circuits. 1.1.1.1. History. The lower is the electrical resistance of the interconnection material in integrated circuits the faster can signals be transmitted between devices. Hence, there is a compelling commercial reason to make use of an interconnection material having the lowest electrical resistivity. Yet, the standard interconnection material in use prior to 2002 in integrated circuits is an aluminum alloy having somewhat higher resistivity than pure aluminum, and even higher resistivity than other metals such as copper, gold and silver. (Table 1.1 provides data which support this statement.) Why? CHAPTER I Electrical Properties Table 1.1.

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  Materials Science and Engineering

  An Introduction

  • William D. Callister, Jr., David G. Rethwisch(Authors)
  • 2018(Publication Date)
  • Wiley

    (Publisher)

  (b) On the extrinsic curve, note freeze-out, extrinsic, and intrinsic regions. 6. For a p–n junction, explain the rectification process in terms of electron and hole motions. 7. Calculate the capacitance of a parallel-plate capacitor. 8. Define dielectric constant in terms of permittivities. 9. Briefly explain how the charge-storing capacity of a capacitor may be increased by the insertion and polarization of a dielectric material between its plates. 10. Name and describe the three types of polarization. 11. Briefly describe the phenomena of ferroelec- tricity and piezoelectricity. The prime objective of this chapter is to explore the Electrical Properties of Materials— that is, their responses to an applied electric field. We begin with the phenomenon of electrical conduction: the parameters by which it is expressed, the mechanism of conduc- tion by electrons, and how the electron energy band structure of a material influences its ability to conduct. These principles are extended to metals, semiconductors, and insula- tors. Particular attention is given to the characteristics of semiconductors and then to semi- conducting devices. The dielectric characteristics of insulating materials are also treated. The final sections are devoted to the phenomena of ferroelectricity and piezoelectricity. 18.1 INTRODUCTION Electrical Conduction One of the most important electrical characteristics of a solid material is the ease with which it transmits an electric current. Ohm’s law relates the current I —or time rate of charge passage—to the applied voltage V as follows: V = IR (18.1) where R is the resistance of the material through which the current is passing. The units for V, I, and R are, respectively, volts (J/C), amperes (C/s), and ohms (V/A).

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