Department Arzt – Research Areas

Nanomechanics of Metals | Thin Film Synthesis | Chemistry
and Patterning of Functional Surfaces | Evolutionary Biomaterials | Micromechanics of Biological Materials | Adaptive Fiber Structures |
Industrial Materials | Study Program Materials Science

Nanomechanics of Metals

Nanoscale metallic materials and structures exhibit size-dependent  mechanical properties, which deviate substantially from bulk values. Our research aims to quantify these phenomena, with a special view to plastic strength and fatigue.

To access these phenomena, various experimental methods to measure the stress/strain properties of thin films are developed and applied in our group. The results are both of fundamental and of technological relevance.

Methods and Devices

• wafer curvature method, recently also under UHV conditions
• in situ microtensile testing under X-ray and synchrotron radiation
• in situ transmission electron microscopy (TEM)
• texture analysis by electron back scatter diffraction (EBSD)
• focussed ion beam microscopy (FIB)
• scanning electron microscopy (SEM)
• atomic force microscopy (AFM)
• nanoindentation, including the continuous stiffness method (CSM)
• bulge tests (-180°C to 200°C)
• mechanical spectroscopy (-180°C to 1000°C)

The samples for our research are supplied by the Thin Film Synthesis and Processing group, also located in our department.

Recent highlights

• extensive data collection on yield stresses of fcc thin films: a strong increase with the inverse film thickness is followed by a plateau (below 100 nm thickness)
• discovery of a new dislocation process: "parallel glide" dominates in thin poly crystalline films, as predicted theoretically
• development of a synchrotron-based technique for testing ultra-thin films: micro tensile testing is now carried out down to film thicknesses of 20 nm, at the limit of X-ray diffraction
• fatigue of small scale films: strong size effects are identified for low and high cycle fatigue
• size effects in bcc films: first results in a new research field
• a MEMS-based in situ TEM technique reveals fracture mechanisms in ultra-fine grained metal films

Cooperations

Prof. J. Balk, University of Kentucky, Lexington, KY, USA
Prof. G. Dehm, University of Leoben, Austria
Prof. K. Hemker, Johns Hopkins University, Baltimore, MD, USA
Dr. M. Legros, CEMES-CNRS, Toulouse, France
Prof. W. D. Nix, Stanford University, Stanford, CA, USA
Prof. T. Saif, University of Illinois at Urbana-Champaign, Urbana, IL, USA
Prof. R. Schlögl, Fritz-Haber-Institute, Berlin
Prof. R. Spolenak, ETH Zürich, Zürich, Switzerland

Selected recent publications

Eberl, C., Spolenak, R., Kraft, O., Ruile, W., Arzt, E. Fatigue damage in thin film Al interconnects at ultra high frequency: A finite element analysis. Thin Solid Films, in press (2006)

Girgsdies, F., Ressler, T., Wild, U., Wübben, T., Balk, TJ., Dehm, G., Zhou, L., Günther, S., Arzt, E., Imbihl, R., Schlögl, R. Strained thin copper films as model catalysts in the materials gap. Cat.Let. 2005;102:91

Böhm, J.,Gruber, P. Spolenak, R., Stierle, A., Wanner, A., Arzt, E. Tensile testing of ultrathin polycrystalline films: A new synchrotron based method. Review of Scientific Instruments 2004; 75: 1110

Wellner, P., Dehm, G., Kraft, O., Arzt, E. Size effects in the plastic deformation of NiAl thin films. Zeitschr. f. Metallk. 2004; 95:769

Balk, J., Dehm, G., Arzt, E. Parallel glide: Unexpected dislocation motion parallel to the substrate in ultrathin copper films. Acta Mat. 2003; 51:4471

Gao, H., Zhang, W., Nix, W. D., Thompson, C. V., Arzt, E. Crack-like grain boundary diffusion wedges in thin metal films. Acta Mat. 1999; 47:2865

Arzt E. Size effects in materials due to microstructural and dimensional constraints: a comparative review. Acta Mat. 1998;46:5611

New perspectives in bcc thin films: Iron film, 500nm thick, as seen in a scanning electron microscope (SEM)

Strength level on the nanoscale: The flow stress of thin copper reaches a plateau

Sophisticated in situ TEM techniques reveal mechanisms of dislocation motion and nucleation

The model of constrained diffusional creep: an explanation for the stress plateau below a critical film thickness

In situ TEM: dislocations on unexpected "parallel" glide planes

for color scale click here

Electron Back Scatter Diffraction (EBSD): the grain orientation depends on the film thickness