Bridgman

Bridgman(Vertical Gradient Freeze method,VGF)method,this method is similar to the horizontal zone melting method , the main way is to move the crucible , the melt temperature gradient within the soup , and then begin to grow crystals. Bridgman method uses a heater is divided into two parts , the top of the furnace body heater temperature is high, the bottom temperature is lower, the temperature difference generated by the heater causes the temperature gradients , and thus crystal growth . Since the growth process , the temperature of the heater is constant, the crystal growth of the solid-liquid interface when the distance to the heater is fixed to the crucible at this time decreased, so that molten metal through the solid-liquid interface , the use of Bridgman way , it solidified molten metal to form a single crystal normal . Principle of growth shown. Bridgman following features:

1)The shape of the crystal can vary the shape of the crucible , for shaped crystal growth ;

2)It can be added directional growth of single crystal seed can also be natural nucleation , based on the principle of geometric phase crystal growth ;

3)It can be closed or semi-closed crucible growth . Prevent melt dopant volatilization , causing
Compositional deviation and doping concentration, and can be hazardous substance pollution of the surrounding environment ;

4)It's suitable for large size , the number of multi- crystal growth . A furnace can grow a few or dozens of different root
Sizes of crystals ;

5 )Operation process is relatively simple and easy to implement procedures and automation . Bridgman 's main drawback is as follows:

a)The whole process of crystal growth within the crucible , not easy to directly observe the growth of the crystal . But
Lower melting point of the organic crystal growth exception can be used to facilitate the observation tube furnace or crucible .

b)Different kinds of crystalline material of the crucible to the physical and chemical properties have specific requirements . In particular, the crucible with the crystalline material matching the thermal expansion coefficient to the right, the volume expansion is not suitable for crystal growth of the crystal material .

c)Crystals in the crystallization process, the crucible crucible easy to produce compressive stress in the crystal nucleation and parasites , so
Crucible inner surface finish have higher requirements .

d)Bridgman crystal growth crucible during descent generally does not rotate , so grow out
Uniformity of the crystal grown by Czochralski method is often not as good out of the crystal

Bridgman's schematic diagram,left melt more crystals less;Right melt fewer larger crystals

Bridgman's schematic diagram