Mechanical properties determined by nanoindentation tests of [Pb(Zr,Ti)O3] and [Pb(Mg1/3Nb2/3)1−xTixO3] sputtered thin films |
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Authors: | P Delobelle E Fribourg-Blanc |
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Affiliation: | a Institut FEMTO - ST, UMR CNRS 6174, Laboratoire de Mécanique Appliquée R. Chaléat - Université de Franche-Comté, 24 chemin de l'Epitaphe - 25000 Besançon, France b Matériaux et intégration pour la microélectronique et les Microsystèmes, DOAE/IEMN MIMM Team - UMR CNRS 8520 - Bat. P3 - Cité Scientifique USTL - 59652 Villeneuve d'Ascq cedex, France |
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Abstract: | As the introduction of piezoelectric materials into micro electromechanical systems increases, there is a correlating requirement for understanding the mechanical properties of these films. We have investigated the mechanical properties of unpoled PZT Pb(Zr,Ti)O3] and PMNT Pb(Mg1/3Nb2/3)1−xTixO3] thin films deposited by sputtering. In this study, nano-indentation, a technique which allows determination of the transverse mechanical properties, is used. It is the easiest method for assessing the biaxial elastic modulus and the hardness of thin films. It was confirmed that neither cracks, nor pile-ups, were observed for indentation depths below 20% of the film's thickness.The continuous stiffness method was used and allowed us to demonstrate that the indentation modulus decreases continuously with increasing grain diameter. This can be explained by the orientation changes of the crystallites with increasing grain diameter. The indentation modulus measured under load, or at almost null load (that is when the ferroelectric domains are or are not oriented by the stress) are coherent with those determined by the same method with a hard bulk ceramic. These results tend to show that the compliance Cij of the hard bulk ceramic can possibly be used with sputtered thin films. The hardness is almost independent of the grain diameter (Hb ≅ 7.5 ± 0.9 GPa) and higher than that for the bulk PZT ceramics considered in this study. PMNT and PZT films have appreciably the same mechanical characteristics. No influence of the film thickness was found on the values of both of these parameters. |
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Keywords: | Nanoindentation Thin films PZT PMNT Indentation modulus Hardness |
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