Einblick in das Verformungsverhalten von mikro- und nano- strukturierten Materialien mithilfe von Röntgenstrahlung

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1 DFG Forschergruppe 714 Plastizität in nanokristallinen Materialien und Legierungen Einblick in das Verformungsverhalten von mikro- und nano- strukturierten Materialien mithilfe von Röntgenstrahlung Patric A. Gruber, R. Baumbusch, J. Lohmiller, O. Kraft D. Bachurin, P. Gumbsch A. Castrup, H. Hahn, J. Markmann, J. Weissmüller, INT T. Filatova, T. Ulyanenkova, S. Doyle, T. Baumbach LAS/ISS izbs Kompetenzfeld Angewandte und neue Materialien Dienstag, 19. Januar 2010 KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 Outline Mechanical testing and in situ characterization with XRD of 1. Thin metallic films on polyimide: polycrystalline (columnar), single-crystalline, nanocrystalline 2. Small scale metallic single crystals: Microcolumns and nanowires Determination of stress and strain Characterization and identification of deformation mechanisms

3 Synchrotron-based tensile testing technique Load Extensometer nm thick metallic film X-rays CCD Camera Tensile tester 125 µm thick polyimide substrate Experimental setup at ANKA/MPI-MF-Beamline Sample layout J Boehm et al, Rev. Sci. Instr. 75, 1110 (2004)

4 Novel aspects polycrystalline y Cu h = 80 nm E = 8.92 kev Cooling system -100 to -150 C Synchrotron radiation: - High flux / variable wavelength polycrystalline as well as single crystalline films as thin as 20 nm - Transmission geometry / area detector whole information by one measurement fast, accurate in situ - Selective different film systems - Microstructural information Tensile testing: -Isothermal T-dependence of mechanical properties - Compliant substrate strains up to 20% single crystalline Au h = 160 nm white beam (5-18 kev) Heating device RT to 250 C

5 Experimental Setup at SLS MS-Powder beamline In cooperation with: Prof. Ralph Spolenak D F Dr. Fabia bi G Gozzo Dr. Bernd Schmitt Strain rate 10-6 to 10-3 s-1; temperature -140 to 200 C

6 Polycrystalline thin film systems Ta SiN x Cu Cu Au Cu Au Au Pd nm Ta Ta SiN x SiN x Polyimide substrate 125 µm All metallic films were prepared by UHV magnetron sputtering. Thickness of Cu and Au films between 20 nm and 1000 nm. Thickness of cap- and interlayers 10 nm. Thickness of nanocrystalline Pd films 1000 nm

7 Typical stress-strain curve 10/300/10 nm Ta/Cu/Ta on 125 µm Polyimide Substrate Stress [MPa] σ x σ y Global Strain [%] ν polyimide = 0.34 < ν Cu = 0.51 tensile stress in transverse direction (σ y )

8 Plasticity of ultra thin Cu and Au films 1000 passivated 1000 passivated Von Mises s flow stress [MP Pa] CuB Cu TaCu TaCuTa unpassivated Von Mises s flow stress [MP Pa] unpassivated Au single-crystalline Au polycrystalline AuSiN SiNAuSiN Film thickness [nm] Film thickness [nm] Distinct effect of different interfaces and microstructures but lower than expected Decrease in slope for all film systems Smallest dimension determines strength Source controlled plasticity Nucleation of partial dislocations in thinnest films/grains PA Gruber et al, Acta Mater 56, 2318 (2008)

9 TEM on deformed single crystalline Au films 31 nm 134 nm [110] [110] Partial dislocations Full dislocations PA Gruber et al, Acta Mater 56, 1876 (2008)

10 Stress evolution and crack density Ta/Cu films on polyimide Ta/Cu films on polyimide [MPa] µm] Long gitudinal stress Cu film thickness 34 nm 67 nm 91 nm 251 nm 506 nm Total strain [%] Crack distance [ 100 Cu film thickness nm 67 nm 91 nm 251 nm 506 nm Total strain [%] Stress release decreases with Mean crack distance and increasing Cu film thickness. fracture strain increase with increasing Cu film thickness PA Gruber et al, J Mater Res 24, 1906 (2009)

11 Strong temperature dependence nm Au films on polyimide nm Au on polyimide ss [MPa] Lo ongitudinal stre C 25 C C C 250 C Total strain [%] MPa] Flow stress [ unpassivated bulk Au passivated Temperature [ C] Very strong temperature dependence compared to bulk material Size effect is completely lost for unpassivated films and 200 C PA Gruber et al, J Mater Res 23, 2406 (2008)

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13 Comparison: stress, peak width and asymmetry [GPa] Stress 1,0 0,8 0,6 0,4 0,2 0,0-0,2-0,4 293 K Asy ymmetry 1,4 1,3 1,2 1,1 1,0 0,9 0,8 0,3 Integra al Breadth 0,2 Deformation mode separation: -elastic -microplastic -macroplastic based on the different evolution of integral breadth, stress and asymmetry parameter Bauschinger like back-strain may be related to recovery of microplastic deformation Strain [%]

14 Micro-Laue diffraction setup at the ALS Berkeley Jia Ye, Daniel Kiener, Andrew Minor, NCEM, LBNL Berkeley Martin Kunz, Nobumichi Tamura, ALS, LBNL Berkeley

15 Micro-Laue diffraction on 1 µm thick Al fiber 10 µm Inhomogenous strain and defect density along the fiber. Andreas Sedlmayr, Dan Gianola, R. Mönig, IMFII Marc Legros, Frédéric Mompiou, CEMES-CNRS, Toulouse

16 Summary In situ synchrotron setups for mechanical testing of thin films and micro- and nanostructures are available. Size effects on flow stress and deformation behavior can be investigated for thin films and micro- and nanocrystals. Combination of stress determination and peak shape analysis enables characterization of elastic, microplastic and macroplastic deformation. Micro-Laue diffraction yields local information on strain and defect densities within single grains or across micro- and nanostructures