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Transcript of INTERPLAY OF ION BOMBARDMENT, SURFACE home.uni- fr Oberflchenmodifizierung INTERPLAY OF ION...

  • Leibniz-Institut fr Oberflchenmodifizierung

    INTERPLAY OF ION BOMBARDMENT,

    SURFACE ORIENTATION AND DIFFUSION

    DURING NITRIDING OF ALUMINIUM

    D. Manova, S. Mndl, B. Rauschenbach

  • Leibniz-Institut fr Oberflchenmodifizierung

    MotivationMotivation

    Wide applications of Al and its alloys

    Low hardness, high wear, low chemical and thermal stability

    Surface modification is necessary

  • Leibniz-Institut fr Oberflchenmodifizierung

    ContentsContents

    Motivation

    Formation of Aluminium Nitride

    Surface Orientation & Sputter Yield

    Diffusion & Temperature

    Conclusion

  • Leibniz-Institut fr Oberflchenmodifizierung

    Bulk DiffusionBulk Diffusion

    Methods: ion implantation, plasma nitriding, low energy implan-tation, plasma immersion ion implantation, ...

    Large scatter in diffusivity

    1,4 1,6 1,810-17

    10-16

    10-15

    10-14

    10-13

    10-12

    10-11

    Detection Limit

    PIII, 30 kV LEI, 1 keV LEI, 1 keV (contaminated) LEI, 1 keV + Anneal II, 100 keV + Anneal

    Diff

    usio

    n co

    effic

    ient

    (cm

    2 /s)

    1/Temperature (1000/K)

    500 450 400 350 300 250

    Temperature (C)

  • Leibniz-Institut fr Oberflchenmodifizierung

    Surface EffectsSurface Effects

    Native oxide layer as barrier against nitrogen insertion

    Sufficient oxygen partial pressure blocks nitrogen supply

    Competition of surface adsorption and sputter removal

    AlN Nitriding of Steel??

    Data from T.Fitz, PhD Thesis

  • Leibniz-Institut fr Oberflchenmodifizierung

    Surface EffectsSurface Effects

    Sputtering in Ar/H2 mixture, 410 C

    Almost uniform surface with regularly arranged features

    Possible explanations:

    i) self organisation

    ii) selective redeposition of sputtered oxide layer

    But: polycrystalline substrate: orientation dependence?

    M.Quast et al., Surf. Coat. Technol. (2001),

  • Leibniz-Institut fr Oberflchenmodifizierung

    Sputtering with CsSputtering with Cs++: EBSD: EBSD

    Sputtering of Al with 5 keV Cs+ ions

    For different grains-different sputter yield and different patterns

    Structure related with grain orientation and not with plane of incident ions

    Relation supported by EBSD patterns and inverse pole figure

    60

    EBSD

    IPFSEM12 3

  • Leibniz-Institut fr Oberflchenmodifizierung

    Surface Structure: PIIISurface Structure: PIII

    Sputtering independent of process (SIMS, PIII) Different surface morphology for different grain orientation after

    sputtering Competing processes: sputtering + adsorption + diffusion

    Surface structure determined by orientation of base material

  • Leibniz-Institut fr Oberflchenmodifizierung

    Temperature and Surface StructureTemperature and Surface Structure

    Nitrogen PII implantation in Al at medium temperature

    Strongly inhomogeneous surface

    Grain boundary diffusion dominates over bulk diffusion at medium temperatures

    Surface determined by grain boundary diffusion

  • Leibniz-Institut fr Oberflchenmodifizierung

    High Temperature DiffusionHigh Temperature Diffusion

    Nitrogen PII implantation in Al at high temperatures

    Very rough surface as a result of competition between sputtering and diffusion

    Uniform surface morphology due to dominance of bulk diffusion

  • Leibniz-Institut fr Oberflchenmodifizierung

    Summary & ConclusionsSummary & Conclusions

    Nitriding of Al different from nitriding of steel.

    Important role of surface orientation

    different sputter yield, diffusion rate, surface morphology

    Grain boundary diffusion starts to dominate over surface diffusion at medium temperatures.

    Bulk diffusion dominates at high temperatures, smoothing differences between grains. But: highly corrugated surface due to simultaneous sputtering.

  • Leibniz-Institut fr Oberflchenmodifizierung

    AcknowledgementsAcknowledgements

    Dr. M. Schreck, Universitt Augsburg

    Dr. J. W. Gerlach, IOM Leipzig

    G. Thorwarth, Universitt Augsburg