INTERPLAY OF ION BOMBARDMENT, SURFACE...
Transcript of INTERPLAY OF ION BOMBARDMENT, SURFACE...
Leibniz-Institut für Oberflächenmodifizierung
INTERPLAY OF ION BOMBARDMENT,
SURFACE ORIENTATION AND DIFFUSION
DURING NITRIDING OF ALUMINIUM
D. Manova, S. Mändl, B. Rauschenbach
Leibniz-Institut für Oberflächenmodifizierung
MotivationMotivation
• Wide applications of Al and its alloys
• Low hardness, high wear, low chemical and thermal stability
� Surface modification is necessary
Leibniz-Institut für Oberflächenmodifizierung
ContentsContents
• Motivation
• Formation of Aluminium Nitride
• Surface Orientation & Sputter Yield
• Diffusion & Temperature
• Conclusion
Leibniz-Institut für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
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 für Oberflächenmodifizierung
AcknowledgementsAcknowledgements
Dr. M. Schreck, Universität Augsburg
Dr. J. W. Gerlach, IOM Leipzig
G. Thorwarth, Universität Augsburg