The EFG process, also known as melt pulling, growth pot or simply CZ, is a single crystal growing technology with which pure single crystal materials can be synthesised.
The process was developed in 1918 by Jan Czochrolski from Poland.
A purified melt of a certain material (e.g. sapphire crystals) is placed in a crucible. From the top, a seed (inoculation) oriented and fixed to a slowly rotating metal rod is plunged into the melt, which is then slowly pulled up again, while the melt solidifies at the forming interface due to overcooling. By varying and decreasing the speed and temperature the crystal grows.
The crystal column is called “ingot”.
The Stepanov process is a modified CZ process, known in the USA as EFG (edge-defined film-fed growth). In this technique, a mask is placed on the surface or a matrix is placed in the melt. Special shapes include sapphire strips (substrates for integrated circuits), sapphire single crystals with a predetermined cross-section and sapphire tubes (lasers, high-pressure lamps na).