Sticking coefficient

Sticking coefficient is the term used in surface physics to describe the ratio of the number of adsorbate atoms (or molecules) that adsorb, or "stick", to a surface to the total number of atoms that impinge upon that surface during the same period of time. Sometimes the symbol S_c is used to denote this coefficient, and its value is between 1 (all impinging atoms stick) and 0 (no atoms stick). The coefficient is a function of surface temperature, surface coverage (θ) and structural details as well as the kinetic energy of the impinging particles.

When arriving at a site of a surface, an adatom has three options. There is a probability that it will adsorb to the surface (${\displaystyle P_{a}}$), a probability that it will migrate to another site on the surface (${\displaystyle P_{m}}$), and a probability that it will desorb from the surface and return to the bulk gas (${\displaystyle P_{d}}$). For an empty site (θ=0) the sum of these three options is unity.

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