Experiments are carried out to investigate the rotation of dust clusters in a radio-frequency plasma sheath with a vertical magnetic field. Our observations are in disagreement with the standard model, in which it was assumed that the neutral gas is at rest and that a steady rotation is attained when the ion-drag force is balanced by neutral friction. Here, we re-examine this basic assumption by carefully designed experiments. Our results suggest that the neutral gas is set into rotation by E×B induced ion flow through ion-neutral collisions and that the dust particles are advected by this flow. A hydrodynamic model is proposed to describe the rotation of the neutral gas and it can explain our observations.

Determination and understanding of energy fluxes to nano-or microparticles, which are confined in process plasmas, is highly desirable because the energy balance results in an equilibrium particle temperature which may even initiate the crystallization of nanoparticles. A simple balance model has been used to estimate the energy fluxes between plasma and immersed particles on the basis of measured plasma parameters. Addition of molecular hydrogen to the argon plasma results in additional heating of the particles due to molecule recombination. The measured particle temperature is discussed with respect to appearing plasma-particle interactions which contribute to the particle's energy balance.

Temperature sensitive features of particular phosphors were utilized for measuring the temperature T(p) of microparticles, confined in the sheath of a rf plasma. The experiments were performed under variation of argon pressure and rf power of the process plasma. T(p) has been determined by evaluation of characteristic fluorescent lines. The results for T(p) measurements are strongly dependent on rf power and gas pressure.

The temperature of micro-particles, confined in the sheath of a capacitively coupled low-pressure rf-discharge in front of an Adaptive Electrode, has been measured for different plasma conditions and in different gas mixtures by using temperature-dependent optical features of the particles. In the range from 10 to 50 Pa, the temperature increase with rising discharge power is found to be more pronounced at low pressures than at higher pressures. Addition of molecular gases to the argon-plasma may either result in a temperature decrease (as in the case of nitrogen) or in additional heating of the particles (when hydrogen is added). The measured particle temperature is discussed with respect to appearing plasma-particle interactions which contribute to the particle's energy balance.

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