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We investigated the retention properties of BLT capacitors fabricated by a chemical solution deposition with Pt electrodes. BLT capacitors showed an opposite-state retention loss much better than that of PZT capacitor. On the other hand, BLT capacitors showed a large polarization loss of the same-state retention within 1 hour baking, while the corresponding loss of PZT was negligible. The hysteresis loops after different baking time showed a negligible imprint and a large relaxation of polarization. These behaviors were explained by a high resistance against imprint and a polarization relaxation possibly due to damaged interfacial layers developed by etching process of the BLT capacitors. [ABSTRACT FROM AUTHOR]

Charge retention loss was investigated for Pt/Pb(Zr 0.4 Ti 0.6 )O 3 /Pt capacitors in short- ( t < 1 s) and long-time ( t > 1 s) regimes. The short-time retention loss behaviors of fatigued capacitors were well described by a power-law function and analyzed in terms of a superposition of polarization relaxation with a distribution of relaxation time. We showed that depolarization field governs the retention loss in the short-time regime. Fatigue-induced defects, probably the interfacial passive layers, seemed to increase the depolarization field. In the long-time regime, the retention loss is shown to be related to the internal field developed parallel to the polarization direction. Particularly in "opposite-state" retention, the internal field caused polarization backswitching resulting in a severe degradation of retention characteristics. The internal field developed during retention was estimated by using Merz equations of polarization switching. Defects dynamics under electric field was discussed in conjunction with the recovery process of imprint. [ABSTRACT FROM AUTHOR]

We investigated the time-dependent current-voltage curves of the forming process in unipolar resistance switching. We applied triggered-voltage triangular-waveform (pulse-waveform) signals with varied sweep rate (amplitude) to Pt/SrTiOx/Pt capacitors. By investigating their temperature dependences, we found that the forming process was driven by two different mechanisms, depending on the sweep rate (amplitude): a purely electrical dielectric breakdown and a thermally assisted dielectric breakdown. For the latter process, we observed precursory changes in the current I(t) before the forming process. By fitting the time-dependent precursory changes with I(t)=Io-A exp(-t/τ), we suggest that the thermally activated migration of oxygen vacancies/ions could help the thermally assisted dielectric breakdown. [ABSTRACT FROM AUTHOR]

The high reset current, IR, in unipolar resistance switching is an important issue which should be resolved for practical applications in nonvolatile memories. We showed that, during the forming and set processes, the compliance current, Icomp, can work as a crucial parameter to reduce IR. Doping with Co or Mn can significantly reduce the leakage current in capacitors made using SrTiOx film, opening a larger operation window for Icomp. By decreasing Icomp with acceptor doping, we could reduce IR in SrTiOx films by a factor of approximately 20. Our work suggests that the decrease in Icomp by carrier doping could be a viable alternative for reducing IR in unipolar resistance switching. [ABSTRACT FROM AUTHOR]

Epitaxial c-axis-oriented Bi3.15Nd0.85Ti3O12 (BNT) thin films with thickness ranging from 150 to 350 nm were deposited on conductive SrRuO3 (SRO) on (001) SrTiO3 substrates by pulsed laser deposition. The top Pt electrode was deposited by sputtering to construct a capacitor Pt/BNT/SRO. The authors have evaluated the effective thickness (ti) and dielectric constant ([variant_greek_epsilon]i) of interfacial layers at the Pt/BNT and BNT/SRO interfaces based on the optical refractive index of the BNT layer and the capacitance frequency as well as the current-voltage characteristics of the capacitors. Using a series capacitor model, they have found that the dielectric constant of bulk BNT and the ti/[variant_greek_epsilon]i ratio are 586 and 1.46 nm, respectively. Knowing the optical dielectric constant ([variant_greek_epsilon]opt) and the product of [variant_greek_epsilon]optti of BNT thin films, the authors have estimated that the effective thickness and dielectric constant of the interfacial layers are 20.1 nm and 13.7, respectively. [ABSTRACT FROM AUTHOR]

The retention characteristics of Ir/IrO2/Pb(Zr0.4Ti0.6)O3(PZT)/Pt/IrO2 capacitors were investigated by measuring the switching and nonswitching polarizations, the switching current profiles, and the P–V hysteresis loops. The retention losses of Ir/IrO2/PZT/Pt/IrO2 capacitors were compared with those of the Pt/PZT/Pt capacitors, and a significant improvement of an opposite-state retention was observed. It was found that the growth and the relaxation behaviors of the internal field are quite similar for both capacitors, but that the polarization backswitching becomes significantly smaller for the PZT capacitors with the IrO2 top electrodes. The difference in polarization backswitching might originate from the nature of the ferroelectric/electrode interfaces, possibly suppressing the nucleation of opposite domains at the interfaces. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Short-time retention loss behaviors were investigated for fatigued Pt/PbZr[sub 0.4]Ti[sub 0.6]O[sub 3]/Pt capacitors. In the short-time regime of t < 1 s, fatigued capacitors showed a significant loss in retained polarization, which could be well described by a power-law function. This behavior was interpreted in terms of a superposition of polarization relaxations with a relaxation time distribution. The effects of the pulse voltage on the relaxation time distribution suggested that the retention loss should be activated by a depolarization field. As the fatigue stress was applied, the retention loss became worse. This effect can be explained in terms of the increase of the depolarization field, possibly due to the growth of an interfacial passive layer. [ABSTRACT FROM AUTHOR]