Definitions
4 likes2,234 views
The document provides an overview of various concepts related to electrical and electronic materials, including capacitors, semiconductors, and ferroelectric materials. Key terms defined include dielectric strength, piezoelectric materials, and phenomena such as fluorescence and luminescence. Additional topics discussed range from the properties of superconductors to the function of components like transistors and solar cells.
Definitions
- 1. Capacitor A device that is capable of storing electrical charge. It typically consists of two electrodes with a dielectric material situated between them, but even an air gap can serve as a dielectric. A capacitor can be a single layer or multi-layer device. Curie temperature The temperature above which a ferroelectric is no longer piezoelectric. Dielectric constant (k) The ratio of the permittivity of a material to the permittivity of vacuum, thus describing the relative ability of a material to polarize and store a charge; the same as relative permittivity. Dielectric Strength The maximum electric field that can be maintained between two conductor plates without causing a breakdown. Doping Deliberate addition of controlled amounts of other elements to increase the number of charge carriers in a semiconductor. Drift velocity The average rate at which electrons or other charge carriers move through a material under the influence of an electric or magnetic field Electrostriction The dimensional change that occurs in any material when an electric field acts on it. Fermi energy The energy level at which the probability of finding an electron is 1>2. Ferroelectric A material that shows spontaneous and reversible dielectric polarization. Forward bias Connecting a p-n junction device so that the p-side is connected to a positive terminal, thereby enabling current to flow Hysteresis loop The loop traced out by the nonlinear polarization in a ferroelectric material as the electric field is cycled. A similar loop occurs in certain magnetic materials. Integrated circuit An electronic package that comprises large numbers of electronic devices fabricated on a single chip
- 2. Intrinsic semiconductor A semiconductor in which properties are controlled by the element or compound that is the semiconductor and not by dopants or impurities. p-n junction A device made by creating an n-type region in a p-type material (or vice versa). A p-n junction behaves as a diode and multiple p-n junctions function as transistors. It is also the basis of LEDs and solar cells. Piezoelectric Materials that develop voltage upon the application of a stress and develop strain when an electric field is applied. Polarization Movement of charged entities (i.e., electron cloud, ions, dipoles, and molecules) in response to an electric field. Rectifier A p-n junction device that permits current to flow in only one direction in a circuit. Superconductor A material that exhibits zero electrical resistance under certain conditions. Thermistor A semiconductor device that is particularly sensitive to changes in temperature, permitting it to serve as an accurate measure of temperature. Transistor A semiconductor device that amplifies or switches electrical signals. Coercivity The magnetic field needed to force the domains in a direction opposite to the magnetization direction. This is a microstructure-sensitive property. Diamagnetism The effect caused by the magnetic moment due to the orbiting electrons, which produces a slight opposition to the imposed magnetic field. Domains Small regions within a single or polycrystalline material in which all of the magnetization directions are aligned. Ferrimagnetism Magnetic behavior obtained when ions in a material have their magnetic moments aligned in an antiparallel arrangement such that the moments do not completely cancel out and a net magnetization remains.
- 3. Magnetic permeability The ratio between inductance or magnetization and magnetic field. It is a measure of the ease with which magnetic flux lines can “flow” through a material. Magnetic susceptibility The ratio between magnetization and the applied field. Permanent magnet A hard magnetic material. Soft magnet Ferromagnetic or ferrimagnetic material that has a coercivity. Characteristic spectrum The spectrum of radiation emitted from a material. It shows peaks at fixed wavelengths corresponding to particular electron transitions within an atom. Every element has a unique characteristic spectrum. Continuous spectrum Radiation emitted from a material having all wavelengths longer than a critical short wavelength limit. Fluorescence Emission of light obtained typically within 10-8 seconds of stimulation. Index of refraction Relates the change in velocity and propagation direction of radiation as it passes through a transparent medium (also known as the refractive index). Laser The acronym stands for light amplification by stimulated emission of radiation. A beam of monochromatic coherent radiation produced by the controlled emission of photons. Luminescence Conversion of radiation to visible light. Phosphorescence Emission of radiation from a material after the stimulus is removed. Photoconduction Production of a voltage due to the stimulation of electrons into the conduction band by radiation. Photons Energy or radiation produced from atomic, electronic, or nuclear sources that can be treated as particles or waves.
- 4. Relaxation time The time required for 1>e of the electrons to drop from the conduction band to the valence band in luminescence. Solar cell A p-n junction device that creates a voltage due to excitation by photons. Thermal emission Emission of photons from a material due to excitation of the material by heat. X-rays Electromagnetic radiation in the wavelength range 0.1 to 100 Å.