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P5.06 - In situ TEM Study of Piezoelectricity and Ferroelectricity of Thin Films 
April 8, 2015   3:30pm - 3:45pm

Oxides based on Ln2O3-MO3 (A = Bi3+, Ln3+ M = Mo and W) system are of significant technological interest for their laser applications1, ionic conduction2, catalytic3, photoluminescence4 and ferroelectric5 properties. In this work, rare earth tungstate La2WO6 grown by pulsed laser deposition for the first time as thin film at room temperature, has been in situ characterized. The experiments are carried out in a JEOL 2010F (200 kV) Transmission Electron Microscope (TEM) equipped with a scanning tunneling microscope (STM) holder for in situ electrical probing. A sharp platinum tip is attached to the movable part of the STM holder controlled with piezoelectrics, and both sample and tip are oriented perpendicular to the electron beam of the TEM. The probe can be positioned in a millimeter-scale workspace with subnanometer resolution enabling the selection of a specific nanostructure and to perform electrical measurements. The characterization of conductivity through the La2WO6 and a qualitative characterization of its piezoelectric behavior are performed. An I-V characteristic has been taken for each step of the tip controlled with the piezoelectrics of the holder. During the experiment a decrease of the resistance is observed while more pressure is applied from the tip to the sample from 8M? to 800K?. Besides, ferroelectricity characterizations are carried out from the cycle of the hysteresis switching current using the I-V method. The measured current is maximum when the applied voltage is close to the coercive voltage of the ferroelectric films and these current maxima correspond to the dipole reorientation contribution of the ferroelectric material6. For La2WO6 the measured coercive voltage is 620mV. Thus, in this work we show the piezoelectric and ferroelectric behavior of La2WO6 through TEM-STM in situ characterization. Moreover, this system also allows us to determine its coercive voltage. 1 Kumaran, A. S. et al. Crystal growth and characterization of KY(WO4)2 and KGd(WO4)2 for laser applications. J. Cryst. Growth 2006, 292 (2),368-372. 2 Lacorre, P et al. Designing fast oxide-ion conductors based on La2Mo2O9. Nature 2000, 404 (6780), 856�858. 3 Alonso, J. A. et al. Preparation and structural study from neutron diffraction data of R2MoO6 (R = Dy, Ho, Er, Tm, Yb, Y). J. Solid State Chem. 2004, 177 (7), 2470�2476. 4 Ishigaki,T. et al. Melt synthesis of oxide red phosphors La2WO6: Eu3+. Physics Procedia. 2009, 2, 587-601. 5 Brixner, L. H.; Sleight, A. W.; Licis, M. S. Ln2MoO6-type rare-earth molybdates -preparation and lattice-parameters. J. Solid State Chem. 1972, 5 (2), 186�190. 6 K. Svensson et al. Compact design of a transmission electron microscopescanning tunneling microscope holder with three-dimensional coarse motion. Rev. Sci. 2003, 74, 4945-4947.

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