What is child-Langmuir equation?
Child’s Law (or the Child-Langmuir Law or three-halves-power law) gives the maximum space-charge-limited current in a planar diode of infinite radius (i.e. one-dimensional beam) as a function of the length and potential difference between anode and cathode. J = K Vd3/2 / d2. where. J = current density (mA mm-2)
What is space charge density in semiconductor?
Another example of space charge occurs when two different semiconductor materials are brought together. Electrons very near the interface in one of the materials (the donor) typically migrate into the other material (the acceptor) in order to establish thermodynamic equilibrium.
What is space charge limit?
One-carrier space-charge-limited. Definition: if an electron injecting contact is applied to an insulator, electrons will travel from the metal into the conduction band of the insulator and form a space-charge similar to that of a vacuum diode.
What is Richardson Dushman equation?
The Richardson-Dushman equation relates the current density of a thermionic emission to the work function (W) and temperature (T) of the emitting material: js = A T2 exp(-W/kT) where. js is the current density of the emission (mA/mm2) A is Richardson’s constant.
What is child’s Law in physics?
The equation known as “Child’s Law” describes the electric current between two metal plates in a vacuum tube; the current flows when a power supply applies a voltage between the plates. One plate, the cathode, is heated hot enough that it will emit electrons well.
What is depletion region?
A region in a semiconductor device, usually at the juncture of P-type and N-type materials, in which there is neither an excess of electrons nor of holes. Large depletion regions inhibit current flow.
What is meant by space charge in a photo conductor?
Space charge refers to the collection of electrons which are emitted from the metal surface, after the application of tube current, at a short distance away from the metal surface.
How do you find charge density?
Thus charge density is very important to calculate for many purposed. Such charge density has to be calculated based on the surface area as well as the volume of the electric object….Formula for Charge Density.
| \lambda | Linear charge density |
|---|---|
| \sigma | Surface charge density |
| \rho | Volume charge density |
| q | Electric charge |
| A | Area |
What is drift current in semiconductor?
Drift current is the electric current caused by particles getting pulled by an electric field. The term is most commonly used in the context of electrons and holes in semiconductors, although the same concept also applies to metals, electrolytes, and so on.
What is the space-charge effect?
Definition of space-charge effect : the limitation of flow of plate current in an electron tube produced by repulsion exerted on electrons leaving the filament by the other electrons in the region between filament and plate.
How is SCLC measured?
Put simply, bore multiplied by stroke gives you cylinder volume, and then you multiply that figure by cylinder count and you have the capacity of the engine.
Which is better Freundlich isotherm or Langmuir’s equations?
This equation implies that if one makes a log-log plot of adsorption data, the data will fit a straight line. The Freundlich isotherm has two parameters while Langmuir’s equations has only one: as a result, it often fits the data on rough surfaces better than the Langmuir’s equations.
What is the derivation of the Langmuir like equation?
The thermodynamic derivation is usually referred to as the “Langmuir-like equation”. This derivation based on statistical mechanics was originally provided by Volmer and Mahnert in 1925. The partition function of the finite number of adsorbents adsorbed on a surface, in a canonical ensemble, is given by
When did Irving Langmuir write the space charge equation?
Irving Langmuir published the application to electron currents in 1913, and extended it to the case of cylindrical cathodes and anodes. The equation’s validity is subject to the following assumptions:
How is the Langmuir model different from the kinetic model?
The difference between the kinetic and thermodynamic derivations of the Langmuir model is that the thermodynamic uses activities as a starting point while the kinetic derivation uses rates of reaction. The thermodynamic derivation allows for the activity coefficients of adsorbates in their bound and free states to be included.