Alex SamarianSchool of Physics, University of Sydney, NSW 2006, Australia

What is Dusty (Complex) Plasma?

Laboratory Dusty Plasma

Why Study Complex (Dusty) Plasma?

Worldwide Research Activities

Complex Plasma Laboratory at University of Sydney

Materials Fabrication

Complex (dusty) plasmaDusty plasmas occur naturallyPlanetary ringsCometsInterstellar gasNoctilucent clouds (upper atmosphere)Combustion products (fossil fuel MHD generators, solid fuel rocket exhausts)Dust generated during plasma processing operations which use reactive gasesElectrode and wall erosion

Complex (dusty) plasmaPlasma contains nano- or micro-sized particlesIn discharge plasma, particles become negatively charged due to impact of more mobile electronsPresence of dusts changes plasma propertiesCharged particles can form arrays: plasma crystal is an experimental realisation of strongly coupled plasma

Plasma Crystal

Features of Complex PlasmaMicro-particles can be visualized individually

Plasma time scales are slowed down (e.g. the dust plasma frequency is about 10 Hz) - plasma studies in slow motion

Damping is small (neutral gas pressure is typically less than 1 mbar) - studies of fast processes

Micro-particles are easily manipulated (e.g. by laser light pressure) - manipulation experiments

Felix Cheung - Unlike classic plasma where we consider the charge to be constant on each particulates, in complex plasma system, the charge on dust particles varies with time and position. And this open a completely new and fasicinating field in physics

Laboratory dusty plasmaEvirf powered electrodeRadius = aCharge = Zdewhere Zd ~ f(r,t) >> 1Sheath BoundaryFE, FthFg, FiIons

Laboratory dusty plasma

Experimental chamber and image of test dust particles levitated above the electrode. The test grains are generated in the discharge (power up to 200W, pressure up to 1 torr) by electrode sputtering.Actual View

Laboratory dusty plasma =4952m =4871m =1994m =4064m =2422m =4184m =2893m =4513mPlanar-2Planar-6 (1,5)Planar-10 (3,7)Planar-3Planar-7 (1,6)Planar-11 (3,8)Planar-4Planar-8 (1,7) =4544mPlanar-9 (2,7)

Why study complex plasmas?Such plasmas are of astrophysical interest (planetary rings, comets, intergalactic space)Need to control the dust produced during plasma processingBasic physics of interaction of plasmas with solidsNew phenomena - particles become charged and can form plasma crystals which can serve as model systems for the solid state phenomenaNew wave modes in dusty plasmasInstabilities in plasma crystalsOpportunities for production of novel materials in nano- and micro- particle form (non-equilibrium plasma chemistry)Micro-diagnostic probes Environmental interest - noctilucent clouds

Worldwide research activitiesPlasma crystals Charging of dust Instabilities Japan, USA, Germany, France, UK, Russia, Holland

Complex plasma in microgravity condition 1996 - first parabolic flight (Max Plank Institute, Germany, ESA) 1997 - first experiment on board of space station Mir (IVTAN, RAS)1999 - IMF program (Germany & Russia, later joined by 8 other countries)2001 - PKE-1 experiments started on board of ISS (ESA, NASA)2002 - Materials research on PKE installation (leaded by French team)

Control dusts during plasma processing (IBM, Sony) Dusts near wall region of plasma reactors (France, ITERA)Complex plasma in the Universe (NASA)

Complex Plasma in SydneySergey VladimirovBrian JamesFelix CheungNeil CramerWilliam TsangAlex Samarian

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Complex Plasma LaboratoryDynamical phenomenaDust OscillationDust VorticesDust Cluster Rotation Charging of Dust particlesPhase TransitionDiffusionDust as novel diagnostic tool

CPL Publications2001Self-excited vertical oscillations in an rf-discharge dusty plasmaPhysical Review E, 64, 025402(Rapid Communication) (2001).

Plasma Kinetics around a Dust Grain in an Ion Flow Physical Review E, Vol. 63, No. 1, Pp. 017401/1-4 (2001)

Sheath measurement in rf-discharge plasma with dust grainsPhysics Letters A, 287, 125 (2001)

Dynamics of the Charging and Motion of a Macroparticle in a Plasma FlowPhysical Review E, Vol. 63, No. 4, Pp. 045401( Rapid Communication )/1-3 (2001)

Positively charged particles in dusty plasmasPhysical Review E, 64, 056407 (2001)

Theory of Collision-dominated Dust Voids in Plasmas Physical Review E, Vol. 63, No. 5, Pp. 056609/1-11 (2001)

Behaviour of Dust Grain in the Double Layer of an Electric Probe in a Gas-DischargePlasma Physics Reports, 27, 340 (2001)

Interaction of a Rodlike Charged Macroparticle with a Flowing Plasma Physical Review E, Vol. 64, No. 2, Pp. 026403/1-7 (2001)

Self-excited motion of Dust Particles in a Inhomogeneous PlasmaPhysics Letters A, 289, 240 (2001)

Oscillations in a Chain of Rod-shaped Colloidal Particles in a Plasma Physical Review E, Vol. 64, No. 3, Pp. 035402(Rapid Communication)/1-4 (2001)

2002Rotation of Coulomb clusters in magnetised dusty plasmaPhysica Scripta, T98, 143 (2002)

Diffusion and Dynamics of Macro-particles in a Complex Plasma Physics of Plasmas, Vol. 9, No. 3, Pp. 835-840 (2002)

Stability of Particle Arrangements in a Complex Plasma Physical Review E, Vol. 65, No. 4, Pp. 046416/1-4 (2002) Criteria of Phase Transitions in a Complex Plasma Physical Review Letters, Vol. 88, No. 24, Pp. 245002/1-4 (2001)

Formation of vertical and horizontal dust vortexes in an RF-discharge plasmaPhysica Scripta, T98, 123 (2002)

Comment on "Dependence of the Dust-Particle Charge on Its Size in a Glow-Discharge Plasma" Physical Review Letters, Vol. 89, No. 22, P. 229501 (2002)

Optical diagnostics of plasma and particle in an atmospheric pressure dusty plasmaPhysica Scripta, 66, 82 (2002)

Vibrational Modes in Plasma Crystals due to Nonlinear temperature Distribution in Gas Discharge Plasmas

2003 Rotation of Coulomb crystals in magnetized inductively coupled complex plasmaIEEE Transaction Plasma Science 31, Issue 1 (2003)

The rotation of planar-2 to planar-12 dust clusters in an axial magnetic fieldNew Journal of Physics, Focus Issue on Complex Plasma (2003)

Materials fabricationGrow particlesNano to microsizeUnifom sizeParticles can be coated - examples metal coating using auxiliary magnetron sputtering sourcea -C:H coating of SiO2 particlesAlumina coating of fluorescent particles to protect particle against degradation and aging and to improve adhesion

Growth of particlesReactive species are generated by dissociation/ionisation of gases in discharge (e.g. in fluorocarbon plasmas used for semiconductor processing)gas phase polymerisation produces molecules which are precursors for high molecular weight compounds (~ 100,000 amu)these act as nuclei for few hundred nanometer size amorphous particles (ex situ TEM) which grow finally to micrometre-sized particles Using capacitively-coupled reactor gas phase products studied using FTIRParticle growth monitored by laser scatteringConcentration of gas phase products correlated with particle production

Growth of particlesArgon/methane and argon/acetylene capacitively-coupled rf plasmas.Gas phase products studied using FTIR; Particle growth monitors by laser scattering and laser absorptionStrong evidence that C2Hx is precursor for particle growthParticle growth occurs spontaneously in argon/acetylene plasmaOccurs in argon/methane transiently when acetylene added

Materials FabricationUniform Ion FlowWake Ion ConeWaferWafer

Please visit our Complex Plasma Laboratory website at:http://www.physics.usyd.edu.au/plasma/complex/index.html

Dust in plasma processingParticles produced during etching processesDust charges and levitates in sheath above silicon waferWhen plasma extinguished, dust falls on waferWays devised to remove suspended dustAs feature size decreases, and inductively-coupled devices become more common, deposition of nanometre sized particles during processing is new problemEfficiency of silicon solar cells improved if nanometre-sized dust particles formed in silane discharge are imbedded in deposited silicon filmBack

In nature, in the universeExamples of Complex Plasma

Felix Cheung - Unlike classic plasma where we consider the charge to be constant on each particulates, in complex plasma system, the charge on dust particles varies with time and position. And this open a completely new and fasicinating field in physics

In our world, in the laboratoryExamples of Complex Plasmawafer

Felix Cheung - Unlike classic plasma where we consider the charge to be constant on each particulates, in complex plasma system, the charge on dust particles varies with time and position. And this open a completely new and fasicinating field in physics

PLASMA CRYSTALS IN SPACE: EXPERIMENTS IN WEIGHTLESS CONDITIONS IN THE SPACE STATIONS

Charge Mechanism for DustBack

Dusty Plasma Experiments

Good morning everyone. I am a PhD student from the University of Sydney. My research interests are in the field of dusty plasma or complex plasma. And I am particularly interested in the rotational properties of such plasma system. So today my talk is titled the rotation of dust particles in magnetized and complex plasma. I started doing this research at Flinders University of South Australia. Now I am mainly based in Sydney.Dusty plasma is a rapidly growing branch of plasma physics. It provides a lot of information in fundamental physics. The knowledge in manipulating particles is important in in plasma processing.

The reason why we are investigating the crystal motion is because by analyzing the motion, we can get a better understanding in the physics of dust transport properties in the discharge. Hence we can manipulate the particles motion.

And also up until now, only a minimal number of experiments have been reported on the motion of dust crystal under the influence of an applied magnetic field. Dust coulomb crystal rotation in a DC glow discharge was reported by in Japan group and in a capacitive RF-discharge by in Germany group.

The rotation of both large and small plasma crystals are currently being studied at Sydney Uni. But today I will concentrate on the small plasma clusters only. Rotational motion can occur when an axial magnetic field is applied to them.

An approximation model was obtained from the data we got from experiment. We also demonstrated that rotational motion in electric field is also possible.We can easily illuminate the dust particles in the plasma crystal with a laser. And this why complex plasma is a really good model for us to study solid state physics and to understand the relationship between the plasma and solid as we can see everything in slow motion. Also we can manipulate the particles so that, eventually, we will be able to produce novel materials, like for superchemistry. We can also use the dust as a diagnostic tool like for plasma sheath visualization and temperature measurement.

Complex plasma does not only exists in laboratory. For example, in the universe, we can find complex plasma in nebulae, at the back of comet tails or in the planet rings where we have ionized gas and fine particulates such as dust, ice or water vapour.And here on earth, there are many applications in everyday life that is associated with complex plasma. For example, in microelectronics, where we have dust contaminates from plasma etching in the silicon wafer. In MHD power generator and tokamak where dust can be introduced into the system. Or from rocket launches where residues are left behind from the high temperature combustion. So as you can see, there is a wide range of field related to complex plasma.