Dielectric and fatigue properties of Pb(Zr 0.53 Ti 0.47 )O 3 thin films prepared from oxide precursors method
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Dielectric and fatigue properties of Pb(Zr0.53Ti0.47)O3 thin films prepared from oxide precursors method Silvia T. Shibatta-Kagesawa1*, C. A. Guarany2, E. B. Araújo2 , N. Oki1 1 Universidade Estadual Paulista (UNESP), Departamento de Engenharia Elétrica 15385-000 Ilha Solteira, SP – Brazil (*E-mail: [email protected]) 2 Universidade Estadual Paulista (UNESP), Departamento de Física e Química 15385-000 Ilha Solteira, SP – Brazil ABSTRACT Fatigue is an important problem to be considered if a ferroelectric film is used for non-volatile memory devices. In this phenomena, the remanent polarization and coercive field properties degrades in cycles which increase in hysteresis loops. The reasons have been attributed to different mechanisms such as a large voltage applied on ferroelectric film in every reading process in Ferroelectric Random Access Memory (FeRAM) or memories for digital storage in computer, grain size effects and others. The aim of this work is to investigate the influence of the crystallization kinetics on dielectric and ferroelectric properties of the Pb(Zr0.53Ti0.47)O3 thin films prepared by an alternative chemical method. Films were crystallized in air on Pt/Ti/SiO2/Si substrates at 700oC for 1 hour, in conventional thermal annealing (CTA), and at 700oC for 1 min and 700oC 5 min, using a rapid thermal annealing (RTA) process. Final films were crack free and presented an average of 750 nm in thickness. Dielectric properties were studied in the frequency range of 100 Hz – 1 MHz. All films showed a dielectric dispersion at low frequency. Ferroelectric properties were measured from hysteresis loops at 10 kHz. The obtained remanent polarization (Pr) and coercive field (Ec) were 3.7 µC/cm2 and 71.9 kV/cm respectively for film crystallized by CTA while in films crystallized by RTA these parameters were essentially the same. In the fatigue process, the Pr value decreased to 14% from the initial value after 1.3 × 109 switching cycles, for film by CTA, while for film crystallized by RTA for 5 min, Pr decreased to 47% from initial value after 1.7 × 109 switching cycles. INTRODUCTION In the recent years, studies involving dielectric, piezoelectric and ferroelectric properties of PbZrx-1TixO3 (PZT) thin films were increased due to the potential applications of this important ferroelectric material in microelectronics devices. The several applications using this material in microelectronic justify the necessity of studying the thin film PZT. As examples of PZT applications, we have nonvolatile memories device for computers [1], piezoelectric and piroelectrics sensors and electromechanical devices [2,3]. With the crescent technological development in micro devices comes a diversified method to obtain thin film ferroelectrics like DC sputtering, RF sputtering [4], sol gel and others [5]. Among the various chemical methods, the Oxide Precursor Method (OPM) [6] has been outstanding as an alternative to obtain ferroelectric thin films with good quality and high stoichiometric control. Although this m
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