Influence of oxygen content on dielectric and electromechanical propertiesof Pb(Mg1/3Nb2/3)O-3 thin films

Pulsed laser deposition was used to grow Pb(Mg1/3Nb2/3)O-3 (PMN) thin film planar capacitor structures. X-ray diffraction and plan-view transmission e lectron microscopy were used to verify PMN crystallography. The dc leakage current and ac capacitance and dielectric loss were measured as a function of temperature and frequency. Finally, crystallographic strain as a functio n of applied dc field was monitored in situ by x-ray diffraction. The elect romechanical strain response was found to depend on the deposition conditio ns for each capacitor. Tensile strains of similar to 0.2% and compressive s trains of similar to 0.35%, both parallel to the applied field, were measur ed for capacitors of different oxygen contents and thicknesses. Tensile str ains achieved are higher than previously reported for PMN thin films or pol ycrystalline ceramics. We propose that the compressive strains are not an i ntrinsic property of the PMN. Instead they are induced by the combined effe ct of joule heating of the capacitor structure, caused by leakage currents, and thermal expansion mismatch between the substrate and films. (C) 1999 A merican Institute of Physics. [S0003-6951(99)00420-9].