Study of dust formation routes by time-resolved in situ multi-pass laser extinction method and laser scattering imaging in microwave magnetized plasma

Dust production kinetics and dust particle dynamics in low pressure (0.1-1 Pa) microwave electron cyclotron resonance acetylene plasmas are investigated experimentally using highly sensitive multi-pass laser extinction and scattering imaging techniques. We showed that despite the very low pressure, carbon dust nanoparticles are produced according to two routes: a homogeneous nucleation route leading to few tens of nanometers-size spherical particles and a heterogeneous route resulting in complex shape micrometer-size dust that are directly expelled from a carbon film deposited when the plasma is operated. We suggest that molecular growth involving positively charged ions may be the dominant mechanism underlying the homogeneous nucleation route for this magnetized plasma. Also, we showed that the dynamic of dust particles is mainly governed by thermophoresis force.