• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.186-189
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• 2003

The role of excess Pb about the crystallization behavior and electrical properties in b(Zr$\sub$0.52/Ti$\sub$0.48/)O3(PZT) thin films has not been precisely defined. In this work, the effect of excess Pb content on the ferroelectric properties of these films was investigated. To analyze the effect, PZT films containing various amounts of excess Pb were Prepared. PZT thin films were deposited on the Pt/Ti bottom electrode by rf magnetron sputtering method and then they were crystallized by rapid thermal annealing (RTA). The experiment showed that all PZT films indicated perovskite polycrystalline structure with preferred orientation (111) and no pyrochlore phase was observed. As higher excess Pb was included, the films showed that value of leakage current shift from 2.03${\times}$10$\^$-6/ to 6.63 ${\times}$ 10$\^$-8/A/cm$^2$ at 100kV/cm, and value of remanent polarization shift from 8.587 ${\mu}$C /cm$^2$ to 4.256 ${\mu}$C/ cm$^2$. Electrical properties of PZT thin film affected by Pb excess content of target were explained to be caused of defect among space charges and defect grain boundaries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.6
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• pp.436-441
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• 1998

$Pt/SrTiO_3/Pb_x(Zr_{0.52}, Ti_{0.48})O_3/SrTiO_3/Si$ structure was prepared by rf-magnetron sputtering method for use in nondestructive read out ferroelectric RAM(NDRO-FEAM). PBx(Zr_{0.52}Ti_{0.48})O_3}$(PZT) and $SrTiO_3$(STO) films were deposited respectively at the temperatures of $300^{\circ}C and 500^{\circ}C$on p-Si(100) substrate. The role of the STO film as a buffer layer between the PZT film and the Si substrate was studied using X-ray diffraction (XRD), Auger electron spectroscopy (ASE), and scanning electron microscope(SEM). Structural analysis on the interfaces was carried out using a cross sectional transmission electron microscope(TEM). For PZT/Si structure, mostly Pb deficient pyrochlore phase was formed due to the serious diffusion of Pb into the Si substrate. On the other hand, for STO/PZT/STO/Si structure, the PZT film had perovskite phase and larger grain size with a little Pb interdiffusion. the interfaces of the PZT and the STO film, of the STO film and the interface layer and $SiO_2$, and of the $SiO_2$ and the Si substate had a good flatness. Across sectional TEM image showed the existence of an amorphous layer and $SiO_2$ with 7nm thickness between the STO film and the Si substrate. The electrical properties of MIFIS structure was characterized by C-V and I-V measurements. By 1MHz C-V characteristics Pt/STO(25nm)/PZT(160nm)/STO(25nm)/Si structure, memory window was about 1.2 V for and applied voltage of 5 V. Memory window increased by increasing the applied voltage and maximum voltage of memory window was 2 V for V applied. Memory window decreased by decreasing PZT film thickness to 110nm. Typical leakage current was abour $10{-8}$ A/cm for an applied voltage of 5 V.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.198-202
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• 2009

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of $(1\;-\;x)Pb(Zr_{0.515}Ti_{0.485})O_3$ - $xPb(Sb_{1/2}Nb_{1/2})O_3$ + 0.5 wt% $MnO_2$ [(1 - x)PZT - xPSN + $MnO_2$] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at $1250^{\circ}C$ for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to $1.3{\mu}m$ by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN+$MnO_2$ ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + $MnO_2$ system, exhibited good piezoelectric properties: a piezoelectric constant ($d_{33}$) of 325 pC/N, an electromechanical coupling factor ($k_p$) of 70.8%, and a mechanical quality factor ($Q_m$) of 1779. The specimens with a relatively high curie temperature ($T_c$) of $305^{\circ}C$ also showed a significantly high dielectric constant (${\varepsilon}_r$) value of 1109. Therefore, the 0.96PZT - 0.04PSN + $MnO_2$ ceramics are suitable for use in ultrasonic vibrators.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.313-322
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• 2001

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. Rosette and pyrochlore phase are observed in PLZT (10/40/60) thin film and the (100) orientation, the grain size, and the surface roughness of PLZT thin films increase due to the increase of Ti amount in Zr/Ti concentration ratio. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10KHz decrease from 600 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kY/cm decrease from 1.64$\times$10$^{-6}$ to 1.26$\times$10$^{-7}$ A/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$ 170 ㎸/cm, the remanent polarization and the coercive field increase from 6.62 to 12.86 $\mu$C/$\textrm{cm}^2$ and from 32.15 to 56.45 ㎸/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying 10$^{9}$ square pulses with $\pm$5V, the remanent polarization of the PLZT (10/40/60) thin film decreases 50％ from the initial state while that of the PLZT (10/0/100) thin film decreases 30％. In the results of retention measurements of 10$^{5}$ s, the remanent polarization of the PLZT (10/0/100) thin film decreases only 11％ from the initial state, while that of the PLZT (10/40/60) thin film decreases 40%.