The Schottky–Nordheim barrier, which is the barrier model used in deriving the standard Fowler–Nordheim-type equation, is a special case. In this case, it is known that the correction factor ν ν is a function of a single variable f h, defined by f h = F / F h, where F h is the field necessary to reduce the height of a Schottky–Nordheim barrier from h to 0. This field is given by