Seed crystal
Encyclopedia
A seed crystal is a small piece of single crystal
/polycrystal material from which a large crystal
of the same material typically is to be grown. The large crystal can be grown
by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it.
The theory behind this effect is thought to derive from the physical intermolecular interaction that occurs between compounds in a supersaturated solution
(or possibly vapor). In solution, liberated (soluble) molecules (solute
) are free to move about in random flow. This random flow permits for the possibility of two or more molecular compounds to interact. This interaction can potentiate intermolecular forces between the separate molecules and form a basis for a crystal lattice. The placement of a seed crystal into solution allows the recrystallization
process to expedite by eliminating the need for random molecular collision/interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily/readily than relying on random flow. Often, this phase transition from solute in a solution
to a crystal lattice will be referred to as nucleation
. Seeding is therefore said to decrease the necessary amount of time needed for nucleation to occur in a recrystallization process.
One example where a seed crystal is used to grow large boules
or ingot
s of a single crystal is the semiconductor
industry where methods such as the Czochralski process
or Bridgman technique are employed.
Single crystal
A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
/polycrystal material from which a large crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
of the same material typically is to be grown. The large crystal can be grown
Crystal growth
A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a major stage of a crystallization process, and consists in the addition of new atoms, ions, or polymer strings into...
by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it.
The theory behind this effect is thought to derive from the physical intermolecular interaction that occurs between compounds in a supersaturated solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
(or possibly vapor). In solution, liberated (soluble) molecules (solute
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
) are free to move about in random flow. This random flow permits for the possibility of two or more molecular compounds to interact. This interaction can potentiate intermolecular forces between the separate molecules and form a basis for a crystal lattice. The placement of a seed crystal into solution allows the recrystallization
Recrystallization (chemistry)
-Chemistry:In chemistry, recrystallization is a procedure for purifying compounds. The most typical situation is that a desired "compound A" is contaminated by a small amount of "impurity B". There are various methods of purification that may be attempted , which includes recrystallization...
process to expedite by eliminating the need for random molecular collision/interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily/readily than relying on random flow. Often, this phase transition from solute in a solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
to a crystal lattice will be referred to as nucleation
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...
. Seeding is therefore said to decrease the necessary amount of time needed for nucleation to occur in a recrystallization process.
One example where a seed crystal is used to grow large boules
Boule (crystal)
A boule is a single-crystal ingot produced by synthetic means. A boule of silicon is the starting material for most of the integrated circuits used today....
or ingot
Ingot
An ingot is a material, usually metal, that is cast into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods.-Uses:...
s of a single crystal is the semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
industry where methods such as the Czochralski process
Czochralski process
The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors , metals , salts, and synthetic gemstones...
or Bridgman technique are employed.
See also
- Crystal structureCrystal structureIn mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
- CrystallizationCrystallizationCrystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...
- Laser Heated Pedestal Growth
- Micro-Pulling-DownMicro-pulling-down-Basics:The micro-pulling-down method is a crystal growth technique based on continuous transport of the melted substance through micro-channel made in a crucible bottom. Continuous solidification of the melt is progressed on a liquid/solid interface positioned under the crucible...
- Single crystalSingle crystalA single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...
- Wafer (electronics)Wafer (electronics)A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...