Diffusion of Electrons in a Constant Field: Tof Analysis

Abstract

Time-of-flight measurement of drift velocity W and diffusion coefficient D is based on the assumption that when a short pulse of electrons from a point Source is injected into a region of constant electric field, then (a), the Center-of-mass of the pulse travels a distance h in time t_m, where W = h/t_mAnd (b), the pulse half-width δt, where t_m+ δt is the time at which the intensity of the pulse has fallen to 1/e of its maximum value at t_m, is related to D by an equation such as

$$ D = \frac{{{h^2}\delta {t^2}}}{{4t_m^3}}\left( 1 \right) $$

(1)