Quenching the melt – Quartz Glass Ampoules

Taking the ampoule, containing the melt, out of the furnace and dipping it in water can be dangerous sometimes. There are a few videos on youtube showing an ampoule explode when trying to quench it. Chances are that they used a thin walled ampoule and that’s why they had an unexpected result.

The advantage of Quartz glass for crystal growth is that it allows the user to keep an eye on the crystal as it grows. Of course, you also need a furnace with a window. And the Quartz crucibles are generally used for growth temperatures not exceeding 1000° C.

Crucibles made out of Alumina, graphite, pyrolytic boron nitride, or other types of material can be used, but other methods of monitoring growth have to be employed. If growing with electric and magnetic fields, a suitable conducting material has to be used.

The ampoules we manufacture at Sandfire Scientific are made out of Semiconductor Grade Fused Quartz Tubing. The chemical composition of the Quartz itself is SiO2, silicon dioxide or silica, and has a purity of 99.995 W %. Quartz is the glass of choice for electrical insulation, and is impermeable to most gases. Another advantage of fused Quartz is its very low coefficient of expansion, and high compression strength. The Quartz we use is also the standard for lamp tubing.

When growing crystals for semiconductor wafer applications the starting material is placed in the Quartz ampoules/crucibles. Then, the ampoules are heated in a Bridgman furnace, for one, and after a period of time, a single crystal is pulled from the melt. When an ampoule is submerged in water to quench it, the heat is transferred from the quartz melt center to the wall of the ampoule and into the water. The glass melt along the inner wall of the ampoule/crucible freezes. The melt quenches and rapidly pulls away from the glass. The shock can sometimes crack the ampoule if the glass wall is not thick enough. There are quite a number of applications for melt-quenching. Some types of nanocrystals, for example, can form completely when melt-quenching.

Fused Quartz ampoules provide the necessary purity and tolerance to high temperature required for such application. In addition to that, our customers ask for ampoules with pyrolyzed carbon coating to facilitate removal of the crystal and reuse of the ampoules, depending on their design. Sandfire Scientific has developed a unique method of applying carbon to the inside of the ampoules/crucibles.

Want to quench a melt, but you are not too sure what kind of Quartz ampoule to use? Please contact us to find out.