Controlled dust mobilization on a solid surface with grazing electron beam incidence

We present experimental results of dust mobilization on a solid surface under an electron beam with grazing incidence. When the electron beam energy has a secondary electron yield greater than 1, dust particles move in the opposite direction of the electron beam. This is caused by asymmetric charging between the beam-facing and beam-shadowed sides of the particles. On the beam-facing side, the microcavity between a dust particle and the substrate surface collects beam electrons and emits beam-induced secondary electrons. In contrast, on the beam-shadowed side, the microcavity mainly collects secondary electrons. It is shown that the charge magnitude on the beam-shadowed side is larger than that on the beam-facing side, resulting in a net repulsive force pointing in the opposite direction of the beam to move the particle. When the beam energy has a secondary electron yield smaller than 1, the beam-facing side charged by primary beam electrons and the beam-shadowed side charged by backscattered beam electrons reach a similar potential close to the beam energy, resulting in the dust particles moving in random directions. These experimental results show agreement with particle-in-cell simulations.