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MoS 2 Nano-particle production in a PACVD environment

MoS 2 Nano-particle production in a PACVD environment. Eva Stoffels, Winfred Stoffels, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands stoffels@discharge.phys.tue.nl Giacomo Ceccone, Francois Rossi, Rachid Hasnaoui

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MoS 2 Nano-particle production in a PACVD environment

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  1. MoS2 Nano-particle production in a PACVD environment Eva Stoffels, Winfred Stoffels, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands stoffels@discharge.phys.tue.nl Giacomo Ceccone, Francois Rossi, Rachid Hasnaoui European Commission, Joint Research Center, Ispra (VA), Italy. Hartmut Keune, G. Wahl, Institut fuer Oberflaechentechnik und Plasmatechnische Werkstoffentwicklung, Technische Universitaet Braunschweig, Germany

  2. WHY ? • The final aim is the deposition of a hard self-lubricating coating • This is obtained by co-deposition of a hard TiN layer • and lubricating MoS2 nano-particles • During wear of the layer, MoS2 is released, providing in situ lubrication, without environmentally dangerous liquid lubricants • Co-deposition will be obtained by CVD or PACVD. • In this work: focus on MoS2 nano-particle production MoS2 particle Particle lubricating the surface Lubricating MoS2 film TiN layer substrate

  3. HOW ? • two chemistries: • A. H2S based: 2MoCl5 + 4H2S + H2 --> 2MoS2 + 10HCl • H2S is in gas form--> easy in use • H2S is very poisonous --> dangerous • B. sulphur based: 2MoCl5 + 4S + 5H2 -->2MoS2 + 10HCl • S needs to be evaporated • S is not toxic and cheap • two techniques: • 1. Condensation of particles in a thermal oven • easy, but additional process step needed, • only equilibrium chemistry --> high pressure • 2. Plasma assisted particle formation • complex, but matching TiN PACVD conditions • non-equilibrium chemistry available

  4. Setup Pressure: 0.05-5 Torr gas flows < 200 sccm rf power 0-500 W • Deposition occurs in the main chamber, with optional (heated) substrate or rf-electode • Thermal reactions occur in a thermal oven • Evaporation chambers supply gaseous sulphur and MoCl5

  5. Particles trapped in plasma -Nano-particles in a plasma acquire negative charge -They are trapped near the plasma glow-sheath edge -They fall on the substrate when the plasma is off -In a ring shaped plasma they are trapped vertically in the ring, but can diffuse horizontally to the center and deposit -Particles are observed by helium neon laser light scattering

  6. Thermal oven Plasma • Effective only at high pressures (>10 Torr) • Not compatible with PACVD TiN coating technology • Fast and abundant particle • formation • Particle size below 100 nm • Uniform size distribution • Spherical shape Sulphur H2S • Low particle formation rate at sub-Torr pressures • Chemistry compatible with TiN coating • Various sizes • Crystalline or amorphous • Fast and abundant particle • formation • Spherical shape • Crystalline and amorphous phase • Sub-micrometer size and larger

  7. H2S & Thermal oven • Useful in CVD environment at pressures above 10 Torr • Potentially not compatible with the TiN chemistry: • 2TiCl4 + N2 + 4H2 --> 2TiN + 8HCl • Particle size can be controlled to sub-micrometer range • particles are cauliflower like Tvap = 150 oC Tdep = 400 oC H2 = 120 sccm H2S = 200 sccm p= 2 kPa (15 Torr)

  8. H2S & Plasma • Fast and abundant particle formation (size < 100 nm) • co-deposition is possible 3 mm Conditions(left): temperature evaporation oven 150 oC and main oven 160 oC, pressure 0.5 Torr, rfpower 13 W, gas flow 10 sccm Ar through evaporation chambers 5 sccm H2and 10 H2S through main oven and 10 sccm H2 in main chamber reaction time: 10 minutes collected under plasma ring

  9. 3µm Sulphur & Thermal oven • Low particle formation rate, and large particles • Crystalline and amorphous particles Amorphous layer with nanoparticles large crystals and nanoparticles 10 mm Conditions: temperature evaporation oven 150 oC and main oven 450 oC, pressure 10 Torr gas flow 20 sccm(left) and 50 sccm(right) Ar through evaporation chambers 50 sccm(left) and 100 sccm(right) H2through main oven 100 sccm Ar(left) and 100 sccm H2(right) in main chamber reaction time: 45 minutes(left) and 30 minutes(right)

  10. Sulphur & Plasma • Fast and abundant particle formation • Crystalline and amorphous phase 1 mm 1 mm Conditions: temperature evaporation oven 150 oC and main oven 160 oC, pressure 0.5 Torr, rfpower 13 W, gas flow 5 sccm Ar through evaporation chambers 5 sccm H2through main oven and 10 sccm H2 in main chamber reaction time: 10 times 2 minutes(left) and 20 times 30 seconds(right) (plasma off 15 seconds) collection area: under plasma ring(left) and in center(right)

  11. Commercial MoS2 • MoS2 can be obtained commercially, • For our purposes it is too large and contaminated by air exposure 3 mm 10 mm

  12. Conclusions • MoS2 nano-particle production is possible under a • variety of conditions: using either H2S or sulphur • in CVD and in PACVD • Crystalline and amorphous material can be produced • The size-range spans from nanometers up to tens of micrometers • Plasma produced particles are formed faster, • more abundant and at lower pressures • Formation of titanium-sulphide and chlorine contamination are • possible future problems for hybrid self-lubricating hard coatings, • however the hardness of the hybrid layers is in the TiN range

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