1. Wear resistant and low friction nanocomposite coatings Dr Tomasz Suszko

2. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 2 Plasma sputtering – short description DC-, triode-, RF-, magnetron sputtering Nonreactive and reactive mode Low friction nanocomposite coatings Chosen results: Mo 2 N/Cu nancristaline films – structure, mechanical and tribological properties Structure, hardness Friction & wear mechanisms in temperature range RT-400°C Lecture outline

3. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 3 http://fusedweb.pppl.gov/CPEP Plasma - the 4 th state of matter

4. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 4 Fundamentals of plasma sputtering – DC sputtering (diode sputtering) - + Cathode Anode + substrate Pressure ~10 Pa noble gas (e.g. Ar) Voltage ~1.5 kV Electron emission Sputtering Implantation Defects generation E-m radiation Ionisation coeffcient Electron energy [eV] 10100 1000 0.01 0.1 1 10 Disadvantages: Low ion current density (low sputtering rate) High working gas pressure resulting in scattering (low deposition rate) Dielectric materials can not be sputtered High voltage is needed

5. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 5 - + 100 V Target 0.5 kV - + Substrate Ionisation coeffcient Electron energy [eV] 10100 1000 0.01 0.1 1 10 +Lower working gas pressure – 0.1 Pa (higher deposition rate) +Higher ion current density (higher sputtering rate) –Dielectric materials can not be sputtered Fundamentals of plasma sputtering – triode sputtering

6. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 6 Ionisation coeffcient Electron energy [eV] 10100 1000 0.01 0.1 1 10 +Lower working gas pressure – 0.1 Pa (higher deposition rate) +Higher ion current density (higher sputtering rate) –Dielectric materials can not be sputtered Fundamentals of plasma sputtering – microwave assisted sputtering Target 0.5 kV – + Substrate Microwave antenna

7. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 7 Substrate Fundamentals of plasma sputtering – RF sputtering RF Matchbox The differce in: mobility of electrons and ions areas of electrodes results in negative target selfbias thus, dielectric materials can be sputtered

8. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 8 Fundamentals of plasma sputtering – motion of the electron in electromagnetic field R L v e cos   v e v e sin 

9. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 9

10. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 10

11. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 11 There is a possibility to control the substrate ion current and the energy of the ions as well – unbalanced magnetron sputtering Substrate Fundamentals of plasma sputtering – magnetron sputtering DC or pulsed power supply Ionisation coeffcient Electron energy [eV] 10100 1000 0.01 0.1 1 10 +Low working gas pressure – 0.1 Pa +Very high ion current density is possible (high sputtering rate)

12. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 12 What materials can be sputtered and deposited? Whatever one need? It must be kept in mind that: Compounds, targets are made of, are decomposed to the atomic form and only then can react again on the substrate (not always getting appropriate conditions) Sputtered atoms are scattered along their way towards substrate (the lighter the more intense thus the stoichiometry can change) A sputtered compound can not to easily evaporate (sufficient vacuum can not be obtain)

13. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 13 End of part one

14. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 14 Mean free path Secondary electron emmision Ion implantation Sputtering Charging effect Thermoemission Magnetic mirror and trap Larmor frequency and radius Magnetron source (gun) From yesterday

15. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 15 Fundamentals of plasma sputtering – reactive sputtering Compounds of the target and gas elements For poorly conducting or insulator deposits pulsed power supply is very usefull Pumping system Inert gas (e.g. Ar) Reactive gas (N 2, O 2, CH 4 etc.) Optical signal (optical emission spectroscopy) Gas pressure Gas flows Discharge power (Substrate bias – energy of the ions) (Substrate ion current density) Control unit

16. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 16 What I won’t speak about is... Plasma enhanced chemical vapour deposition Laser ablation Plasma spraying Ion implantation (clasical or plasma immersion) Plasma nitriding or carburazing etc.

17. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 17 Plasma maintained by: DC or pulsed discharge (magnetron), Vacuum arc, RF e-m waves Plasma maintained by: DC or pulsed discharge (magnetron), Vacuum arc, RF e-m waves Working gases: Ar (inert gas), N 2 (for nitrides), O 2 (for oxides), CH 4, C 2 H 2 (for carbides and DLC) Working gases: Ar (inert gas), N 2 (for nitrides), O 2 (for oxides), CH 4, C 2 H 2 (for carbides and DLC) Targets made of: Ti, Al, Mo, V, Ag, Cu but also Fe, Ni, Co and Si Targets made of: Ti, Al, Mo, V, Ag, Cu but also Fe, Ni, Co and Si What we use for deposition is...

18. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 18 Coils supply Pulsed power supply Substrate bias and heating Pulsed power supply Spectrometer Pumping system Optical signal Gases Valve unit Magnetron sources What we develop for process control and data acquisition is...

19. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 19 F L What we interest in is... Continuous looking for novel anti-wear coatings and development of their deposition methods Phenomena in the tribolgical contact between hard coated surface and a counterpart Structure, elemental and phase composition of the coatings in the initial state (after deposition) Stress, adhesion, hardness of the coatings Friction during tribological tests (especially in elevated temperatures) Tribomutation - chemical and physical changes of the „third body” – elemental and phase composition, structure etc. of that The role of oxides in friction process

20. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 20 Where can we look for hard compounds?

21. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 21  Chemical sythesis ( DLC, c-BN, AlMgB, C 3 N 4 )  Forming proper physical microstructure Nitride or carbide multilayers (TiN/CrN, TiN/TiAlN i in.) Composites nc-Me x N/a-Si 3 N 4 nc-Me x C/a-C:H np. nc-TiN/a-Si 3 N 4 Composites Me x N/M np. (ZrN/Cu, Cr 2 N/Cu, TiN/Ag) How to obtain hard films

22. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 22  Shear strength and hardness depend on each other thus friction coefficients are comparable for various izotropic materials. Hardness is not all - there is friction also! Shear strength Hardness F L A large small large Soft materials F L Hard materials A

23. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 23 F L Self-lubricating materials As a result of rubbing, a thin low-shear- -strengh layer should appear The material should be hard (what ensures small contact area) Composite materials: guaiac wood PTFE impregnated bronzes bearing metals with graphite or MoS 2 inclusions ceramic/carbon fiber composites Izotropic materils: diamond

24. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 24 RTDinfo - Mag. Europ. Res., 39, 2003 Self-lubricating FILMS Hard coating Enviromental gas Lubricating film

25. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 25 Mo 2 N as a hard coating MoO 3 as a solid lubricant Cu additive as a mean for hardness enhancement An attempt - Mo 2 N/Cu coatings

26. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 26 Mo 2 N/Cu nanocrystalline films – s tructure, mechanical and tribological properties Suszko et al., Surf. Coat. Tech., 200, 2006, pp. 6288-6292 Suszko et al., Surf. Coat. Tech., 194, 2005, pp. 319-324 Outline 1. Deposition method 2. Some remarks on the structure 3. Hardness of the films 4. Friction & wear in temperature range RT-400°C 5. Conclusions

27. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 27 Deposition method: unbalanced magnetron sputtering pulsed power supply pulsed power supply sample external coils pumps Ar, N 2 Mo Cu optical signal 30 cm Temperature: 200 °C Bias: -30 V

28. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 28 Structure – XRD spectra 0 2 4 6 8 10 12 14 16 18 Intensity [a.u.] Fe (substrate) 0% at. Cu 1% at. Cu 6% at. Cu 9% at. Cu 21% at. Cu 404550556065 Diffraction angle 2ϑ [°] ← γ-Mo 2 N (111) γ-Mo 2 N (200)→ ← Cu (111) Cu (200)→ Co K α radiation

29. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 29 Cu content (at. %) 0510152025 5 6 7 8 9 10 11 12 13 Crystallite size [nm] Mo 2 N (200) Crystallite size obtained from Scherrer’s formula AFM image of the pure γ–Mo 2 N nitride The influence of copper content on crystalite size

30. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 30 Structure Crystallite size and film hardness Cu content (% at.) 0510152025 5 6 7 8 9 10 11 12 13 Crystallite size (nm) Mo 2 N (111) Mo 2 N (200) 0510152025 10 15 20 25 30 35 40 Cu content (% at.) H (GPa) Load-depth sensitive method DUH 202 (F N 20 mN) Load-depth sensitive method Hysitron (F N 2mN) Traditional method (F N 100—1000 mN)

31. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 31 0100200300400 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Temperature [°C] Friction coefficient 0 % at. Cu 3 % at. Cu 7 % at. Cu 22 % at. Cu Fixed and scanned temperature TiN Friction coefficient Ball on disc configuration Counterpart: alumina ball Speed: 5 cm/s Normal force: 1 N

32. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 32 Wear rate coefficient - a definition Worn volume of the sample per work unit done against friction force -1.5 -0.5 0 0.5 b) 100°C 0 100200300400500600700 μmμm μmμm 010002000300040005000 0 0.2 0.4 0.6 0.8 1 Revolution number Friction coefficient

33. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 33 Wear behavior: 20-400°C 0510152025 10 -15 10 -14 10 -13 10 -12 Copper content (at. %) Wear rate ( m 3 /J ) 10 -16 400°C 300°C RT, 200°C 100°C Wear rate for TiN RT – 0.8·10 -14 200°C – 1.5·10 -14 400°C – 3·10 -15

34. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 34 Wear behavior – "100°C effect" RT: k F ~10 -16 m 3 / 100°C: k F ~2·10 -14 m 3 /J ! 200°C: k F ~10 -16 m 3 /J 02004006008001000 0 0.5 1 Raman shift [cm -1 ] Out In 02004006008001000 0 0.5 1 Raman shift [cm -1 ] Out In 02004006008001000 0 0.5 1 Raman shift [cm -1 ] Out In Mo 2 N 0% Cu

35. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 35 6 at. % Cu 50  m 9 at. % Cu 50  m 22 at. % Cu 0 at. % Cu 50  m 1 at. % Cu 50  m 2.5 at. % Cu Wear behavior – the influence of Cu addtion (100°C friction test) k F ~10 -16 m 3 /Jk F ~2·10 -14 m 3 /J

36. International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko suszko@tu.koszalin.pl http://www.balticnet-plasmatec.org 36 Conclusions Relatively low friction coefficient against alumina is observed in room temperature. 1-3 at. % of Cu additive increases hardness of Mo 2 N coatings. Low wear rate is registered in temperatures bellow 250°C. "The 100°C effect" is observed for samples with low content of copper. This effect is eliminated when films contain >6 at. % Cu. Coatings gradually oxidize in temperature over 300°C.