ELECTROMECHANICAL PROPERTIES OF Pb(Mg_(1/3)Nb_(2/3))O_3 THIN FILM CAPACITORS

摘要

Pulsed Laser Deposition was used to grow Pb(Mg_(1/3)Nb_(2/3))O_3 (PMN) thin film planar capacitor structures. PMN crystallography was verified by x-ray diffraction and plan-view Transmission Electron Microscopy (TEM). Capacitance of the thin film structures was measured as a function of temperature and frequency. Leakage current was also measured for each capacitor. A DC field was subsequently applied and crystallographic strain was monitored in-situ by X-ray diffraction. The electromechanical strain was found to strongly depend on the deposition conditions for each capacitor. Tensile strains of ～0.2% and compressive strains of ～0.3% parallel to the applied field were measured for capacitors of different oxygen contents and thicknesses. We propose that the compressive strain is caused by the combined effect of joule heating of the capacitor structure, caused by large leakage currents, and epitaxial coupling between substrate and films. Electrostrictive tensile strains are of the same order as observed in bulk.