Island growth

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.