AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS1-TuM

Paper NS1-TuM8
Nanoindentation Mechanism and Surface Recovery in an Ionic Crystal Surface, MgO(100)

Tuesday, October 26, 1999, 10:40 am, Room 612

Session: Nanomechanics
Presenter: P.F.M. Teran Arce, Universidad de Barcelona, Spain
Authors: P.F.M. Teran Arce, Universidad de Barcelona, Spain
G. Andreu Riera, Universidad de Barcelona, Spain
P. Gorostiza, Universidad de Barcelona, Spain
F. Sanz, Universidad de Barcelona, Spain
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The atomic force microscope can be used to perform nanoindentations on surfaces. With the resulting indentation curves one is enabled to characterize at the nanometer level elastic and strength properties of materials. Furthermore, one is allowed to follow in situ the recovery of the surface after the indentation, therefore gaining insight into the processes affecting the dynamical behavior of the surface. We have carried out nanoindentations, only a few monatomic layers deep, on a semibrittle surface, MgO(100), utilizing an atomic force microscope both for indenting and imaging. Indentations were performed by scanning the piezo vertically until the tip contacts and eventually indents the surface. A force curve was recorded to characterize in situ the indentation. It was found that relative humidity, RH, plays a fundamental role in the kinetics of surface recovery after the indentation. Therefore, in order to avoid the influence of recovery processes in the measurement of cavity dimensions, indentations were carried out at 0 % RH when measuring elastic or strength properties. The force curves obtained show characteristic discontinuities associated with atomic layers being expelled by the tip penetrating the surface. Indentation curves extracted from the force plots show clearly two regions. One of them corresponds to the elastic deformation of the crystal. The other one starts with the onset of discontinuities and corresponds to plastic deformation. The Young modulus and hardness values of MgO(100) obtained from these experiments agree well with the known macroscopic values.