1. Jari Koskinen 1 Thin Film Technology Lecture 2 Vacuum Surface Engineering Jari Koskinen 2014

2. Jari Koskinen 2 Vacuum surface engineering 1.Vacuum technology 2.Surface phenomena 3.Surface energetic ion interaction

3. Jari Koskinen 3 Vacuum surface engineering 1.Vacuum technology 2.Surface phenomena 3.Surface energetic ion interaction

4. Jari Koskinen 4 Vacuum system VACUUM GAUGE VACUUM CHAMBER FLANCE PUMP RESUDUAL GAS

5. Jari Koskinen 5

6. Jari Koskinen 6 Large surfaces, upscaling www.scheuten.com

7. Jari Koskinen 7 Residual gas pump desorption diffusion of dissolved molecules permeation leak Pumping of: Residual gas: Adsorption – Desorption Diffusion of dissolver or trapped gas Permeation trough materials Leaks

8. Jari Koskinen 8 Units of pressure UltraGood High HighInter- mediate Rough Total pressure of residual gasses

9. Jari Koskinen 9 Sources of residual gas High vacuum pumping speed leak Good High vacuum desorption from walls baking Ultra high vacuum impurities internal leaks material selection diffusion permeation

10. Jari Koskinen 10 UltraGood High HighInter- mediate Rough Total pressure of residual gasses Average mean free path (distance between collission) in nitrogen residual gas

11. Jari Koskinen 11 Average mean free path (distance between collission) in nitrogen residual gas UltraGood High HighInter- mediate Rough Total pressure of residual gasses

12. Jari Koskinen 12 Phases of residual gas UltraGood High HighInter- mediate Rough Total pressure of residual gasses d = diameter of chamber Viscotic < d/100 Intermediate Molecular >> d

13. Jari Koskinen 13 Phases of residual gas UltraGood High HighInter- mediate Rough Total pressure of residual gasses d = diameter of chamber Viscotic < d/100 Intermediate Molecular >> d

14. Jari Koskinen 14 Time to form one molecular layer on surface UltraGood High HighInter- mediate Rough Total pressure of residual gasses

15. Jari Koskinen 15 Vapour and liquid in vacuum pump balance: pumping = evaporation pressure constant until all liquid is pumped balance: condensation = evaporation

16. Jari Koskinen 16 Critical temperatures and pressures for some residual gasses above T c no liquid pump Helium Hydrogen Nitrogen Carbon monoxide Argon Oxygen Methane Carbon dioxide Chlorine Ether Ethanol Carbon tetraclor. Water Gas or vapor

17. Jari Koskinen 17 Vacuum pumps Positive displacement (mechanical pumps) Momentum transfer (molecular pumps) Entrapment

18. Jari Koskinen 18 Mechanical pumps Rotary vaneRootsDiafragma

19. Jari Koskinen 19 Mechanical pumps Scroll pumppump

20. Jari Koskinen 20 Momentum transfer Turbo molecularmolecularOil diffusion pump pump

21. Jari Koskinen 21 Entrapment cryo pumppump ion pump

22. Jari Koskinen 22 Pumps and vacuum ranges

23. Jari Koskinen 23 Vacuum gauges Mechanical – diaphragm Electronic Piezoresitive (strain gauge) Capacitive Magnetic Piezoelectric Optical Potentiometric Resonant Thermal conductivity – Pirani Ionzation gauge Hot cathode Cold cathode (Penning)

24. Jari Koskinen 24 Gauges ionization gauge hot filamentPirani

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26. Jari Koskinen 26 Residual gas analyser SRS RGA100 Residual Gas Analyzer

27. Jari Koskinen 27 Vacuum systems

28. Jari Koskinen 28 Vacuum systems

29. Jari Koskinen 29 Gas flow in vacuum systems Q = C(P 1 – P 2 ) P1P1 P2P2 C conductance l/s Q gas troughput [pressure*volume/s] in series: in parallel:

30. Jari Koskinen 30 Conductance of various geometries M. Ohring

31. Jari Koskinen 31 Vacuum systems

32. Jari Koskinen 32 Vacuum system design

33. Jari Koskinen 33 Vacuum surface engineering 1.Vacuum technology 2.Surface phenomena 3.Surface energetic ion interaction

34. Jari Koskinen 34 Surface energy γ surface tension = dW work needed to form surface dA In thermodynamic equilibrium:

35. Jari Koskinen 35 Contact angle Young equation S solid L liquid G gas Spreading parameter S Complete wetting when S ≈ 0 non-wetting when S ≈ -2 Υ LG

36. Jari Koskinen 36 Surface reconstruction 

37. Jari Koskinen 37 Surface structure and defects 

38. Jari Koskinen 38 Adsorption Physisorption Chemisorption

39. Jari Koskinen 39 Adsorption Physisorption Chemical bonding: polaroization (van der Waals) Bonding energy ≈ 0.001 – 0.5 eV Bond length ≈ 3 – 10 Å For example: nobel gas or molecules on materials Possibly precursion state before chemisorption

40. Jari Koskinen 40 Adsorption Chemisorption Chemical bonding: charge exchange Bonding energy ≈ 0.5 – 5 eV Bond length ≈ 1 – 3 Å For example: H, O, N, CO on metals Dissociation of molecule Final absorption

41. Jari Koskinen 41 Desorption Adsorbed molecule receives energy E D in order to leave surface thermal radiation photons electrons ions electric field

42. Jari Koskinen 42 Balance of absorption - desorption collisions of molecules (gas) S sticking coefficient E D energy for desorption P pressure Coverage ≈ High P, low T more adsorption E D large, full coverage very little adsorption in UHV

43. Jari Koskinen 43 Surface diffusion http://iramis.cea.fr/spcsi/Phocea/Vie_des_labos/Ast/astimg.php?voir=60&type=groupe

44. Jari Koskinen 44 Surface diffusion  Diffusion is thermally activated random movement of adsorbed atoms  D = D 0 e -E act /kT  E act large -> slow diffusion  T high – fast diffusion http://iramis.cea.fr/spcsi/Phocea/Vie_des_labos/Ast/astimg.php?voir=60&type=groupe Surface diffusion of Cu on Cu(111) E act

45. Jari Koskinen 45 Work function  Work function ϕ  E F Fermi energy  D dipole potential

46. Jari Koskinen 46 Work function of some metals Adsorbed atoms alloying effect work function

47. Jari Koskinen 47 Solubility of gasses into metals

48. Jari Koskinen 48 Vacuum surface engineering 1.Vacuum technology 2.Surface phenomena 3.Surface energetic ion interaction

49. Jari Koskinen 49 Energetic ion surface interactions

50. Jari Koskinen 50 Secondary electrons

51. Jari Koskinen 51 Desorption, cleaning

52. Jari Koskinen 52 Sputtering

53. Jari Koskinen 53 Collision cascade, thermal spike K. Nordlund

54. Jari Koskinen 54 Thermal spike http://en.wikipedia.org/wiki/File:10kevau _au.gif HY Nordlund simulations http://beam.acclab.helsinki.fi/~knordlun/ anims.html http://beam.acclab.helsinki.fi/~knordlun/ gif/au500.avi 10 keV Au ion to Au surface

55. Jari Koskinen 55 doping, compounds