by: kyle logan meen 3344. crystals have special desired optical and electrical properties growing...

By: Kyle Logan

MEEN 3344

Crystals have special desired optical and electrical properties

Growing single crystals to produce gem quality stones

Industrial applications Money

The driving force for crystallization comes from the lowering of the potential energy of the atoms or molecules when they form bonds to each other. 

CVD A slice of material is placed in a chamber A vapor form or hydrocarbon gas is

introduced into a high pressure, high temperature atmosphere (58,000 atm @ 2,300°F for diamonds)

Atoms land on the surface of the slice The crystal can be cut to applications Bridgman Material is melted, starting at one end to the

other. At a pace from 5-50 mm/day

Compared to other growth methods, Bridgman method is considered to be a rather simple crystal growth method, but several limitations still exist.

The Bridgman method can not be applied to a material system which decomposes before it melts, systems having components with high vapor pressure, and materials exhibiting destructive solid - solid phase transformations which will compromise the crystalline quality on cooling the crystal at the end of the growth run.

Strains develop during growth and can be reduced by thermal annealing.

Thermal annealing is where the crystals are heated at a particular rate to a particular temperature, then kept there for a particular time duration and then slowly cooled down to room temperature.

For optical or electrical use the single crystals are cut into thin wafers around 300-500 microns, then polished and then etched to remove imperfections

For diamonds and gems, they are cut and shaped to the desired ranges or appearance, and then they are polished to remove imperfections

Prior to any device fabrication process, the polished surface is sometimes etched in order to remove the damaged/ defective layer produced during polishing process.

Etchants are also useful for revealing bulk defects present in the crystals.

Some etchants are also used for determining the orientation of the crystal surface.

Electrical- Silicon, Gallium Arsenide, Diamond, etc. for computer chips and other uses for semi conductors

Optical- Diamond, lasers, lenses, optical fiber. etc.

Industrial- Diamond cutting tools

3-D Holographic optical storage More powerful lasers Diamond computer chips, instead of

silicon “Diamond is the hardest material, it

won’t expand in heat, won’t wear, is chemically inert and optically transparent”. ~Paul May

http://www.fisk.edu/~aburger/Published03_06/Sample_prep/Crystal_growth/crystal_growth.html

http://www.siliconfareast.com/crystal.htm http://www.usatoday.com/tech/news/

techinnovations/2005-10-06-man-made-diamonds_x.htm