Dynamics of a pulsed-electron beam induced plasma: application to the growth of zinc oxide thin films

Spatial and temporal distributions of species emitted from ablation of zinc oxide target by a pulsed-electron beam are studied by the complementary use of optical emission spectroscopy and camera fast imaging. We show that the slowest electrons produced by the accelerating tube in the pulsed-electron beam deposition (PED) system interact with the plasma plume and involve a further excitation of the neutrals species. The velocities of atoms and ions are found to be similar to those obtained in the well-known pulsed-laser deposition (PLD) process while the plasma temperature and the electron density are lower. The low absorption of the electron beam by the expanding plasma compared with that experienced in PLD leads to a higher removal of ablated material and consequently to a higher deposition rate ten times greater than in PLD. The PED ZnO films grown at room temperature on silicon substrate are constituted by the stacking of small aggregates without large macroscopic droplets. These results are in agreement with the ICCD images recorded at long time delays from the electron impact which do not evidence bright trails correlated with the propagation of slow and large particles.