Processing of dust particles

in low-pressure plasmas 

G. Paeva, R.P. Dahiya*, E. Stoffels, W.W. Stoffels, G.M.W. Kroesen,

Department of Physics, Eindhoven University of Technology,

PO Box 513, 5600 MB Eindhoven

* on leave from: Centre for Energy Studies, Indian Institute of Technology, New Delhi - 110016, India.

E-mail: w.w.stoffels@tue.nl web page www.phys.tue.nl/EPG/

RFelectrodeTrapping

ring

Magnetronsputter head

Particlecloud

Lightsource

Manipulator armwith particle sieve

A schematic view of the setup. Particles are injected and trapped in the RF plasma. Coating is performed using a

magnetron sputter source at the top. For the void formation experiment the magnetron is replaced by a camera.

A schematic view of the setup. Particles are injected and trapped in the RF plasma. Coating is performed using a

magnetron sputter source at the top. For the void formation experiment the magnetron is replaced by a camera.

SETUPSETUP

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nsity

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Left: The fluorescent spectrum of the BAM particles in an Ar plasma. The fluorescence is induced by the UV radiation from the plasma.

Right: Optical spectrum during Cu coating process in Ar using an external Hg lamp as a light source. The broad band reflects the BAM fluorescence from uncoated particles. Simultaneously, Hg-lines are visible due to Mie scattering.

Left: The fluorescent spectrum of the BAM particles in an Ar plasma. The fluorescence is induced by the UV radiation from the plasma.

Right: Optical spectrum during Cu coating process in Ar using an external Hg lamp as a light source. The broad band reflects the BAM fluorescence from uncoated particles. Simultaneously, Hg-lines are visible due to Mie scattering.

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integrated 545nm Hg

integrated 576nm Hg

integrated flurescence signal

Problem:There is some decrease in the fluorescence from the BAM particles even in pure Argon plasma. Probably due to VUV degradation of the BAM particles.

Calibration in Ar needed Other fluorescent particles

Problem:There is some decrease in the fluorescence from the BAM particles even in pure Argon plasma. Probably due to VUV degradation of the BAM particles.

Calibration in Ar needed Other fluorescent particles

Time dependence of scattering and fluorescence signal.•The scattering signal reflects particle density.

•The fluorescence signal reflects uncoated particle surface.

•The faster decay of the fluorescence indicates particle coating.

Time dependence of scattering and fluorescence signal.•The scattering signal reflects particle density.

•The fluorescence signal reflects uncoated particle surface.

•The faster decay of the fluorescence indicates particle coating.

uncoatedcoated

Particles coated with sputtered aluminium.Particles coated with sputtered aluminium.

(left) crystalline structure and (right) 7mm diameter void in the dust cloud in RF plasma sheath. Ring electrode (30 mm diameter) is visible on the periphery. The pictures of 9.8 m diameter MF are recorded by camera looking from the top of the experimental system, which is normal to the page.

(left) crystalline structure and (right) 7mm diameter void in the dust cloud in RF plasma sheath. Ring electrode (30 mm diameter) is visible on the periphery. The pictures of 9.8 m diameter MF are recorded by camera looking from the top of the experimental system, which is normal to the page.

2-D VOID FORMATION2-D VOID FORMATION

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Left: Inner (ID) and outer diameter (OD) of particle ring in argon RF plasma sheath and the position of a single bigger size particle at lower horizontal plane (right hand scale).

Right: Surface of the particle cloud

Left: Inner (ID) and outer diameter (OD) of particle ring in argon RF plasma sheath and the position of a single bigger size particle at lower horizontal plane (right hand scale).

Right: Surface of the particle cloud

VOID EVOLUTION IN ARGONVOID EVOLUTION IN ARGON

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Graph 2(d)Ar, 22May01, Ar=10sccm, RF Power=10 WArea of dust cloud vs pressure

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Graph 4 ArOxyVd, 30May01, Pressure=0.18 mbar, Power=(40-0.16) WattAr+Oxygen=10sccm, void is closed at 55% oxygen

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Graph4(d):30May01, press=0.18 mbar, rf power=40-0.16WAr+Oxy=10sccm, area of dust cloud, Vd closed at 55%oxy

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VOID EVOLUTION IN ARGON / OXYGENVOID EVOLUTION IN ARGON / OXYGEN

Variation of the void size (left) and cloud surface(right) as a function of oxygen percentage in Argon + Oxygen mixture for RF

power = 40 W and P = 0.18 mbar.

The void can be closed by adding oxygen.

Variation of the void size (left) and cloud surface(right) as a function of oxygen percentage in Argon + Oxygen mixture for RF

power = 40 W and P = 0.18 mbar.

The void can be closed by adding oxygen.

CONCLUSIONS:

Processing

•Particles can be trapped in an RF plasma and simultaneously coated by magnetron sputtering.

•Coating process is monitored using fluorescent particles.

2-D Void formation

•In 2-D Coulomb crystals voids can be created similarly to 3-D voids observed in micro gravity conditions.

•The driving force for void formation seems to be the ion drag force.

•Void diameter depends on plasma conditions (pressure, power).

•The void can be closed by using electronegative gases

CONCLUSIONS:

Processing

•Particles can be trapped in an RF plasma and simultaneously coated by magnetron sputtering.

•Coating process is monitored using fluorescent particles.

2-D Void formation

•In 2-D Coulomb crystals voids can be created similarly to 3-D voids observed in micro gravity conditions.

•The driving force for void formation seems to be the ion drag force.

•Void diameter depends on plasma conditions (pressure, power).

•The void can be closed by using electronegative gases