1. 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 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 MoS 2 nano-particles During wear of the layer, MoS 2 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 MoS 2 nano-particle production substrate TiN layer MoS 2 particle Lubricating MoS 2 film Particle lubricating the surface

3. HOW ? two chemistries : A. H 2 S based: 2MoCl 5 + 4H 2 S + H 2 --> 2MoS 2 + 10HCl H 2 S is in gas form--> easy in use H 2 S is very poisonous --> dangerous B. sulphur based:2MoCl 5 + 4S + 5H 2 -->2MoS 2 + 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 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 MoCl 5 Pressure: 0.05-5 Torr gas flows < 200 sccm rf power 0-500 W

5. -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 Particles trapped in plasma

6. Thermal ovenPlasma Sulphur H 2 S 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 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. H 2 S & Thermal oven Useful in CVD environment at pressures above 10 Torr Potentially not compatible with the TiN chemistry: 2TiCl 4 + N 2 + 4H 2 --> 2TiN + 8HCl Particle size can be controlled to sub-micrometer range particles are cauliflower like T vap = 150 o C T dep = 400 o C H 2 = 120 sccm H 2 S = 200 sccm p= 2 kPa (15 Torr)

8. H 2 S & Plasma Fast and abundant particle formation (size < 100 nm) co-deposition is possible 3  m Conditions(left): temperature evaporation oven 150 o C and main oven 160 o C, pressure 0.5 Torr, rfpower 13 W, gas flow 10 sccm Ar through evaporation chambers 5 sccm H 2 and 10 H 2 S through main oven and 10 sccm H 2 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 10  m Conditions: temperature evaporation oven 150 o C and main oven 450 o C, pressure 10 Torr gas flow20 sccm(left) and 50 sccm(right) Ar through evaporation chambers 50 sccm(left) and 100 sccm(right) H 2 through main oven 100 sccm Ar(left) and 100 sccm H 2 (right) in main chamber reaction time: 45 minutes(left) and 30 minutes(right) Amorphous layer with nanoparticleslarge crystals and nanoparticles

10. Sulphur & Plasma Fast and abundant particle formation Crystalline and amorphous phase 1  m Conditions: temperature evaporation oven 150 o C and main oven 160 o C, pressure 0.5 Torr, rfpower 13 W, gas flow 5 sccm Ar through evaporation chambers 5 sccm H 2 through main oven and 10 sccm H 2 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 MoS 2 10  m 3  m MoS 2 can be obtained commercially, For our purposes it is too large and contaminated by air exposure

12. Conclusions MoS 2 nano-particle production is possible under a variety of conditions:using either H 2 S 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