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What is solid state diffusion?

What is solid state diffusion?

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).

What is diffusion of iron?

Self-diffusion in high-purity iron (99.97 per cent Fe) has been determined over the temperature range from 700 to 1436°C. The diffusivity below the magnetic transformation is lower than expected from an extrapolation of the diffusion data for paramagnetic alpha-iron.

What is vacancy diffusion?

The unit step in vacancy diffusion is an atom breaks its bonds and jumps into neighboring vacant site. In interstitial diffusion, solute atoms which are small enough to occupy interstitial sites diffuse by jumping from one interstitial site to another.

Does Iron diffuse?

More interstitial diffusion in iron At a temperature of 1000 oC (1832 oF) where forging takes place, and at temperatures somewhat below the γ → α transition temperature of 910 oC (1670 oF), in pure iron all three interstitial elements can cover distances of several µm in just 1 second.

How does solid state diffusion work?

Diffusion in solid state materials is a process whereby a liquid, a gas, or another solid can mix together with the host solid on the atomic level. 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.

What is the mode of carbon diffusion in iron?

Due to a small atomic radius, carbon is expected to dissolve by interstitial diffusion in solid metals.

What are two types of diffusion in metals?

4. Types of Diffusion:

  • Types of Diffusion: The different types of diffusion are:
  • Self-Diffusion: Self-diffusion is the migration of atoms in pure materials.
  • Inter-Diffusion: It occurs in binary metallic alloys.
  • Volume Diffusion:
  • Grain Boundary Diffusion:
  • Surface Diffusion:

Why is interstitial diffusion much faster than substitutional diffusion?

Interstitial diffusion is generally faster than vacancy diffusion because bonding of interstitials to the surrounding atoms is normally weaker and there are many more interstitial sites than vacancy sites to jump to. Requires small impurity atoms (e.g. C, H, O) to fit into interstices in host.

Which of the following will diffuse the fastest in iron?

Carbon atoms
Carbon atoms will diffuse fastest in iron since the rate of diffusion depends upon the size of the atoms.

What is the difference between interstitial diffusion and self-diffusion?

Self-diffusion occurs by a vacancy mechanism, whereas carbon diffusion in iron is interstitial. Diffusion coefficient is the measure of mobility of diffusing species. or diffusion of substitutional atoms).