What is diffusion in solid state?
Solid state diffusion is a straight forward process and the typical method for introducing dopant atoms into semiconductors. Heating the wafer at a high temperature in an atmosphere containing dopant atoms causes some of the atoms to be incorporated into the top surface of the wafer.
How is diffusion coefficient determined?
The diffusion coefficient is calculated from the slope of the least-squares regression line relating the magnitude of the instantaneous solute flux to that of the instantaneous concentration gradient. Diffusion coefficients thus determined in water at 25 degrees C for CaCl2 (7.54 X 10(-6) cm2.
What is the use of diffusion coefficient?
The diffusion coefficient is a function of the fluid, size of the diffusing molecule (larger molecules diffuse more slowly), temperature, obstruction of diffusion by pore structure in sediments or other materials, and the rate of mixing of water.
Does diffusion occur in solid?
This is because of diffusion , the movement of particles from an area of high concentration to an area of low concentration. This means that diffusion does not happen in solids – the particles in a solid can only vibrate and cannot move from place to place.
What does a large diffusion coefficient mean?
The higher the diffusivity (of one substance with respect to another), the faster they diffuse into each other. Typically, a compound’s diffusion coefficient is ~10,000× as great in air as in water.
Why does diffusion occur in solids?
In solids, particularly, diffusion occurs due to thermally-activated random motion of atoms – unless the material is at absolute zero temperature (zero Kelvin), individual atoms keep vibrating and eventually move within the material. Therefore, this type of diffusion mechanism is referred to as “vacancy diffusion”.
How is a solid state diffusion process formed?
Solid state diffusion is a straight forward process and the typical method for introducing dopant atoms into semiconductors. In silicon solar cell processing starting substrates are typically uniformly doped with boron giving a p-type base. The n-type emitter layer is formed through phosphorus doping (see Doping ).
How is the solid state of a semiconductor formed?
Solid state diffusion is a straight forward process and the typical method for introducing dopant atoms into semiconductors. In silicon solar cell processing starting substrates are typically uniformly doped with boron giving a p-type base. The n-type emitter layer is formed through phosphorus doping (see Doping ). Solid state diffusion.
How is the rate of diffusion affected by temperature?
For diffusion to occur, there must be a concentration gradient present and the rate of the diffusion process is greatly affected by an increase in temperature. By using post 1982 pennies which consist of a zinc core and a copper plated shell, the diffusion of copper into zinc can be readily shown.
How does the diffusion of atoms take place?
Heating the wafer at a high temperature in an atmosphere containing dopant atoms causes some of the atoms to be incorporated into the top surface of the wafer. In its simplest form the diffusion process follows Fick’s law: