• Nanotechnology 19 (2008) 475709 - [Nanotechnology]

    2008-10-31

     

    Thickness-dependent phase transformation in nanoindented germanium thin films

    D J Oliver1, J E Bradby1, J S Williams1, M V Swain2 and P Munroe3
    1 Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, The Australian National University, Canberra ACT 0200, Australia
    2 Biomaterials Science Research Unit, Faculty of Dentistry, The University of Sydney, Eveleigh, NSW 1430, Australia
    3 Electron Microscope Unit, University of New South Wales, Sydney, NSW 2052, Australia
    E-mail:     djo109@rsphysse.anu.edu.au

    Abstract. We investigate the mechanical response of 50–600 nm epitaxial Ge films on a Si substrate using nanoindentation with a nominally spherical (R≈4.3 µm) diamond tip. The inelastic deformation mechanism is found to depend critically on the film thickness. Sub-100 nm Ge films deform by pressure-induced phase transformation, whereas thicker films deform only by shear-induced dislocation slip and twinning. Nanoindentation fracture response is similarly dependent on film thickness. Elastic stress modelling shows that differing stress modes vary in their spatial distribution, and consequently the film thickness governs the stress state in the film, in conjunction with the radius of the nanoindenter tip. This opens the prospect of tailoring the contact response of Ge and related materials in thin film form by varying film thickness and indenter radius.

    Print publication: Issue 47 (26 November 2008)
    Received 10 September 2008, in final form 14 October 2008
    Published 30 October 2008
    Tag：Swain_MV
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