Quasi-Stationary Processes of the Dielectric Relaxation in Polycrystalline Thin PZT Films
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OELECTRICS
Quasi-Stationary Processes of the Dielectric Relaxation in Polycrystalline Thin PZT Films V. V. Ivanova, E. N. Golubevaa, O. N. Sergeevaa, b, *, G. M. Nekrasovab, I. P. Proninc, and D. A. Kiselevd a Tver
State University, Tver, 170100 Russia Tver State Agricultural Academy, Tver, 170100 Russia c Ioffe Institute, St. Petersburg, 194021 Russia d National University of Science and Technology MISiS, Moscow, 119049 Russia *e-mail: [email protected] b
Received April 17, 2020; revised April 17, 2020; accepted April 21, 2020
Abstract—The relaxation processes in polycrystalline PZT films formed on silicon substrates have been studied during a quasi-static change in an external electric field. The dielectric relaxation is shown to be characterized at least by three relaxation times depending on the direction of the self-polarization in the film, the value of the polarizing field, and also the PZT film annealing temperature. Keywords: polycrystalline thin PZT films, rf magnetron sputtering, relaxation phenomena DOI: 10.1134/S1063783420100133
Interest to studying thin lead zirconate–titanate (PZT) films as most important functional materials in modern microelectronics is not lost now, as well. The use of these materials as elements of nonvolatile memory [1, 2] justifies the topicality of studying their switching properties whose features are the existence of several quasi-stationary relaxation processes with different relaxation times; however, there is no unambiguous opinion on their physical nature up to now [3–7]. This is especially true regarding the shortest relaxation time of several seconds. In this work, we studied the relaxation phenomena in polycrystalline PZT films prepared by rf magnetron sputtering of the ceramic PbZr0.54Ti0.46O3 target in the region of the morphotropic phase boundary on a platinized silicon substrate at a temperature of 150°C; then, the films was subjected to annealing (crystallization) in air at various temperatures (Tann) from 580 to 650°C to form the perovskite phase. To compensate the lead loss during the perovskite phase crystallization, 10 mol % PbO was added in the stoichiometric composition of the target. The thickness of the deposited PZT films was 0.5–1 μm. The upper electrodes were also fabricated from platinum. The relaxation processes were studied both at the quasi-static change in the external electric field and in the fields corresponding to the maxima of the dielectric permittivity at reversible dependences (ε–V). The relaxation dependences of the capacity and the dielectric permittivity we studied using an E7-20 immittance
meter at a frequency of 10 kHz and the measurement voltage 100 mV. The time dependences of the local piezoelectric response of the PZT films were studied using a piezoresponse force microscopy in the contact mode at the scanning nanolaboratory Ntegra Prima (NT-MDT). The measurements were performed at a frequency of 150 kHz when applying an ac voltage with amplitude 5 V and applying dc bias voltage (Udc) in the range from 10 to 30 V to an NSG30
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