Alex Samarian School of Physics, University of Sydney, NSW 2006, Australia

Transcription

1 Alex Samarian School of Physics, University of Sydney, NSW 2006, Australia

2 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

3 Complex (dusty) plasma Dusty plasmas occur naturally Planetary rings Comets Interstellar gas Noctilucent clouds (upper atmosphere) Combustion products (fossil fuel MHD generators, solid fuel rocket exhausts) Dust generated during plasma processing operations which use reactive gases Electrode and wall erosion

4 Complex (dusty) plasma Plasma contains nano- or microsized particles In discharge plasma, particles become negatively charged due to impact of more mobile electrons Presence of dusts changes plasma properties Charged particles can form arrays: plasma crystal is an experimental realisation of strongly coupled plasma Plasma Crystal Γ = 2 Qd πε dkt 4 0 d exp d λ D >> 1

5 FC6 Features of Complex Plasma Micro-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

6 Slide 5 FC6 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 Felix Cheung, 29/08/2002

7 Laboratory dusty plasma Ions v i Sheath Boundary E F E, F th F g, F i Radius = a Charge = Z d e where Zd ~ f(r,t) >> 1 T rf powered electrode

8 Laboratory dusty plasma Actual View 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.

9 Laboratory dusty plasma Planar-2 ρ =199±4µm Planar-3 ρ =242±2µm Planar-4 ρ =289±3µm Planar-6 (1,5) ρ =406±4µm Planar-7 (1,6) ρ =418±4µm Planar-8 (1,7) ρ =451±3µm Planar-9 (2,7) ρ =454±4µm Planar-10 (3,7) ρ =495±2µm Planar-11 (3,8) ρ =487±1µm

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

11 Worldwide research activities Plasma crystals Charging of dust Instabilities Japan, USA, Germany, France, UK, Russia, Holland Complex plasma in microgravity condition first parabolic flight (Max Plank Institute, Germany, ESA) first experiment on board of space station Mir (IVTAN, RAS) IMF program (Germany & Russia, later joined by 8 other countries) PKE-1 experiments started on board of ISS (ESA, NASA) 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)

12 Complex Plasma in Sydney 1. Sergey Vladimirov 2. Brian James 3. Felix Cheung 4. Neil Cramer 5. William Tsang 6. Alex Samarian

13 Complex Plasma Laboratory Dynamical phenomena Dust Oscillation Dust Vortices Dust Cluster Rotation Charging of Dust particles Phase Transition Diffusion Dust as novel diagnostic tool

14 CPL Publications 2001 Self-excited vertical oscillations in an rf-discharge dusty plasma Physical Review E, 64, (Rapid Communication) (2001). Plasma Kinetics around a Dust Grain in an Ion Flow Physical Review E, Vol. 63, No. 1, Pp /1-4 (2001) Sheath measurement in rf-discharge plasma with dust grains Physics Letters A, 287, 125 (2001) Dynamics of the Charging and Motion of a Macroparticle in a Plasma Flow Physical Review E, Vol. 63, No. 4, Pp ( Rapid Communication )/1-3 (2001) Positively charged particles in dusty plasmas Physical Review E, 64, (2001) Theory of Collision-dominated Dust Voids in Plasmas Physical Review E, Vol. 63, No. 5, Pp /1-11 (2001) Behaviour of Dust Grain in the Double Layer of an Electric Probe in a Gas- Discharge Plasma Physics Reports, 27, 340 (2001) Interaction of a Rodlike Charged Macroparticle with a Flowing Plasma Physical Review E, Vol. 64, No. 2, Pp /1-7 (2001) Self-excited motion of Dust Particles in a Inhomogeneous Plasma Physics 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 (Rapid Communication)/1-4 (2001) 2002 Rotation of Coulomb clusters in magnetised dusty plasma Physica Scripta, T98, 143 (2002) Diffusion and Dynamics of Macro-particles in a Complex Plasma Physics of Plasmas, Vol. 9, No. 3, Pp (2002) Stability of Particle Arrangements in a Complex Plasma Physical Review E, Vol. 65, No. 4, Pp /1-4 (2002) Criteria of Phase Transitions in a Complex Plasma Physical Review Letters, Vol. 88, No. 24, Pp /1-4 (2001) Formation of vertical and horizontal dust vortexes in an RF-discharge plasma Physica 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 (2002) Optical diagnostics of plasma and particle in an atmospheric pressure dusty plasma Physica 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 plasma IEEE Transaction Plasma Science 31, Issue 1 (2003) The rotation of planar-2 to planar-12 dust clusters in an axial magnetic field New Journal of Physics, Focus Issue on Complex Plasma (2003)

15 Materials fabrication Grow particles Nano to microsize Unifom size Particles can be coated - examples metal coating using auxiliary magnetron sputtering source a -C:H coating of SiO 2 particles Alumina coating of fluorescent particles to protect particle against degradation and aging and to improve adhesion

16 Growth of particles Reactive 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 FTIR Particle growth monitored by laser scattering Concentration of gas phase products correlated with particle production

17 Growth of particles Argon/methane and argon/acetylene capacitivelycoupled rf plasmas. Gas phase products studied using FTIR; Particle growth monitors by laser scattering and laser absorption Strong evidence that C 2 H x is precursor for particle growth Particle growth occurs spontaneously in argon/acetylene plasma Occurs in argon/methane transiently when acetylene added

18 Materials Fabrication Uniform Ion Flow Wake Ion Cone Wafer Wafer

19 Please visit our Complex Plasma Laboratory website at:

20 Dust in plasma processing Particles produced during etching processes Dust charges and levitates in sheath above silicon wafer When plasma extinguished, dust falls on wafer Ways devised to remove suspended dust As feature size decreases, and inductively-coupled devices become more common, deposition of nanometre sized particles during processing is new problem Efficiency of silicon solar cells improved if nanometre-sized dust particles formed in silane discharge are imbedded in deposited silicon film Back

21 FC4 Examples of Complex Plasma Nebulae Comet Tails Planet Rings In nature, in the universe

22 Slide 20 FC4 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 Felix Cheung, 29/08/2002

23 FC5 Examples of Complex Plasma In our world, in the laboratory wafer MHD Generator Microelectronics Solid Propellant European TOR

24 Slide 21 FC5 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 Felix Cheung, 29/08/2002

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

26 Charge Mechanism for Dust Back

27 Dusty Plasma Experiments