Island growth is a physical model of deposited film growth and
chemical vapor deposition
Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.
In typical CVD, the wafer (substra ...
.
Introduction
When
atoms
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, an ...
are deposited slowly onto a flat
surface
A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is t ...
, the first one undergoes a
random walk
In mathematics, a random walk is a random process that describes a path that consists of a succession of random steps on some mathematical space.
An elementary example of a random walk is the random walk on the integer number line \mathbb Z ...
on that surface. Eventually a second atom is deposited; in all likelihood it will eventually meet the first atom. Once the two atoms meet they may bond to form a particle with a higher mass and a lower random walk velocity. Because the bonded particles are now more stable and less mobile than before, they are called an "island." Subsequent atoms deposited on the substrate eventually meet and bond with the island, further increasing its size and stability. Eventually the island can grow to fill the entire substrate with a single large grain.
The faster the atoms are deposited, the greater amount of atoms on the substrate before any large stable islands form.
As these atoms meet, they will bond to their local neighbors before having the chance to migrate to a distant island. In this way a large number of separate islands are formed and can grow independently. Eventually the separate islands will grow to become separate grains in the final film.
The island growth model is used to explain how fast deposition techniques (such as
sputter deposition
Sputter deposition is a physical vapor deposition (PVD) method of thin film deposition by the phenomenon of sputtering. This involves ejecting material from a "target" that is a source onto a "substrate" such as a silicon wafer. Resputtering is re ...
) can produce films with many randomly oriented grains, whereas slow deposition techniques (such as
MBE Mbe may refer to:
* Mbé, a town in the Republic of the Congo
* Mbe Mountains Community Forest, in Nigeria
* Mbe language, a language of Nigeria
* Mbe' language, language of Cameroon
* ''mbe'', ISO 639 code for the extinct Molala language
Molal ...
) tend to produce larger grains with more uniform structure.
See also
Stranski–Krastanov growth
Stranski–Krastanov growth (SK growth, also Stransky–Krastanov or Stranski–Krastanow) is one of the three primary modes by which thin films grow epitaxially at a crystal surface or interface. Also known as 'layer-plus-island growth', the SK mo ...
References
Thin film deposition
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