Single crystal growth

High-quality single crystal growth is one of most important theme in our Lab. Interesting physical properties attract us and good size and shape single crystal also do that. By using various techniques, we try growing crystals.

●Czochralski (pulling) method
We use radio frequency furnace and tetra arc furnace to pull up the single crystal after contacting seed or tungsten rod to melt of materials. This method require technique, and trial and error.

　high-frequency furnace
We heat up a tungsten crucible with materials by high-frequency induction heating. This method enables us to stabilizing temperature of melt regardless of an amount of materials, contrary to the tetra arc furnace. Due to the reactivity of material with the crucible, the highest temperature is reduced to 1500 ℃.

　tetra arc furnace
It has four tungsten tourched to improve a stability of temperature. Material are put on Cu-hearth which is cooled by water. Arc melting is done under pure Ar atomosphere. While pulling up the single crystal, it is difficult to make the temperature stable, because an amount of melt decreases. Unfortunately, we can not deal with materials with high vapor pressure.

process of pulling up single crystal. move seed sample to a melt, necking (allignment of direction), pulling.

●Flux method
The flux is solvent to melt materials. We often use In, Sn, Bi, and so on with low melting point as the flux. We put on materials into alumina crucible with a large amount of flux element and heat up it. The single crystals are grown in the process of cooling. To remove the flux, we centrifuge or use some kind of acids.

●Bridgman method Inserting materials into W or Mo crucible with high melting poin, we seal it under Ar atomasphere by using tetra-arc furnace. Single crystals are grown by thermal gradient or moving the crucible away from the heater.

Each technique has merits and demerits. To achieve a purpose of growing high-quality single crystals, we challenge every day using various of techniques. We investigate physical properties of single crystals and sometimes supply for special experimental technique, sound-wave and NMR, for example.