Island growth
Encyclopedia
Island growth is a physical model of deposited film growth and chemical vapor deposition
.
Consider a situation where atoms are being deposited onto a flat surface at a very slow rate. The first atom deposited undergoes a random walk
on the surface. Eventually a second atom is deposited and can be expected to eventually meet the first atom, given enough time. 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.
If atoms are being deposited at a faster rate, there will be many atoms present 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
) can produce films with many randomly-oriented grains, whereas slow deposition techniques (such as MBE
) tend to produce larger grains with more uniform structure.
Some proper, brief history of the thin film physics can be found in the following links:
http://www.uccs.edu/~tchriste/courses/PHYS549/549lectures/index.html
http://en.wikipedia.org/wiki/Stranski%E2%80%93Krastanov_growth
Chemical vapor deposition
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
.
Consider a situation where atoms are being deposited onto a flat surface at a very slow rate. The first atom deposited undergoes a random walk
Random walk
A random walk, sometimes denoted RW, is a mathematical formalisation of a trajectory that consists of taking successive random steps. For example, the path traced by a molecule as it travels in a liquid or a gas, the search path of a foraging animal, the price of a fluctuating stock and the...
on the surface. Eventually a second atom is deposited and can be expected to eventually meet the first atom, given enough time. 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.
If atoms are being deposited at a faster rate, there will be many atoms present 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
Sputter deposition is a physical vapor deposition method of depositing thin films by sputtering, that is ejecting, material from a "target," that is source, which then deposits onto a "substrate," such as a silicon wafer...
) can produce films with many randomly-oriented grains, whereas slow deposition techniques (such as MBE
Molecular beam epitaxy
Molecular beam epitaxy is one of several methods of depositing single crystals. It was invented in the late 1960s at Bell Telephone Laboratories by J. R. Arthur and Alfred Y. Cho.-Method:...
) tend to produce larger grains with more uniform structure.
Some proper, brief history of the thin film physics can be found in the following links:
http://www.uccs.edu/~tchriste/courses/PHYS549/549lectures/index.html
http://en.wikipedia.org/wiki/Stranski%E2%80%93Krastanov_growth