Electric-field penetration into metals: consequences for high-dielectric-constant capacitors

Black, Charles T.; Welser, J.J.

doi:10.1109/16.753713

Cited by 158 publications

(112 citation statements)

References 17 publications

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“…2,18 On the other hand, the interfacial capacitance may mostly originate in the finite electronic screening length of metallic electrodes. 19,20 This would be in agreement with the results of recent first-principles calculations 21 and the latest experimental data on high quality BaTiO 3 thin films, 4 which indicate that the observed polarization relaxation can be attributed to the depolarizing field determined solely by imperfect compensation of ferroelectric polarization charges by electron density variations in SrRuO 3 electrodes. The form of Eq.…”

Section: Introductionsupporting

confidence: 80%

Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films

Pertsev

Dittmann

Plonka

et al. 2007

Journal of Applied Physics

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We studied theoretically the influence of the progressive strain relaxation and the depolarizing-field effect on the thickness dependence of the out-of-plane dielectric response of epitaxial ferroelectric thin films sandwiched between extended metal electrodes. The calculations show that the inverse of the measured capacitance varies with the film thickness almost linearly in the most part of the thickness range at the majority of temperatures. Extrapolation of this linear dependence to zero thickness usually gives considerable nonzero intercept even in the absence of nonferroelectric interfacial layers. Remarkably, such apparent “interfacial capacitance” in a certain temperature range becomes negative. The physical meaning of the effective dielectric constant, which can be extracted from the slope of the reciprocal capacitance thickness dependence, is also analyzed. The theoretical predictions are compared with the experimental data obtained for single-crystalline SrRuO3∕Ba0.7Sr0.3TiO3∕SrRuO3 and Pt∕Ba0.7Sr0.3TiO3∕SrRuO3 thin-film capacitors.

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Section: Introductionsupporting

confidence: 80%

Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films

Pertsev

Dittmann

Plonka

et al. 2007

Journal of Applied Physics

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“…To obtain theoretical E d values for our SRO/BTO/SRO capacitors, we have to know accurate values of ǫ e , λ, and ǫ F . Unfortunately, the reported physical parameter values in the literature vary [5,6,16,17]. Also, we could not find any definite experimental study on ǫ e .…”

mentioning

confidence: 82%

Polarization Relaxation Induced by a Depolarization Field in Ultrathin FerroelectricBaTiO3Capacitors

et al. 2005

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Time-dependent polarization relaxation behaviors induced by a depolarization field E d were investigated on high-quality ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors. The E d values were determined experimentally from an applied external field to stop the net polarization relaxation. These values agree with those from the electrostatic calculations, demonstrating that a large E d inside the ultrathin ferroelectric layer could cause severe polarization relaxation. For numerous ferroelectric devices of capacitor configuration, this effect will set a stricter size limit than the critical thickness issue.PACS numbers: 77.22. Ej, 77.22.Gm, 77.80.Dj, 77.55.+f With recent breakthroughs in fabricating high-quality oxide films [1,2,3], ultrathin ferroelectric (FE) films have attracted much attention from the scientific as well as application points of view. As the FE film thickness d approaches tens of unit cell length, the FE films often show significantly different physical properties from those of bulk FE materials. Some extrinsic effects, especially coming from FE film surfaces and/or interfaces with other materials, could be very important [4]. For some other cases, intrinsic physical quantities could play vital roles in determining the unique properties of ultrathin films.Many FE-based electronic devices have the capacitor configuration, where a FE layer is inserted between two conducting electrodes. Then, polarization bound charges will be induced at the surfaces of the FE layer, but compensated by free charge carriers in the conducting electrodes. In real conducting electrodes, however, the compensating charges will be induced with a finite extent, called the screening length λ. This will result in an incomplete compensation of the polarization charges. Such an incomplete charge compensation should induce a depolarization field E d inside the FE layer, with a direction opposite to that of the FE polarization P [5]. Therefore, E d will appear in every FE capacitor, and its effects will becomes larger with the decrease of d [5]. (For a FE film without electrodes, there is no compensation for the polarization bound charge, so the value of E d will become even larger than that of the FE capacitor case.) E d has been known to be important in determining the critical thickness [6] and domain structure of ultrathin FE films [7,8,9], and reliability problems of numerous FE devices [10,11].Recently, using a first principles calculation, Junquera and Ghosez investigated the critical thickness of BaTiO 3 (BTO) layers in SrRuO 3 (SRO)/BTO/SRO capacitor [6]. For calculations, they assumed that all of the BTO and SRO layers were fully strained with the SrTiO 3 substrate. By taking the real SRO/BTO interfaces into account properly, they showed that E d could make the ferroelectricity vanish for the BTO films thinner than 6 unit cells, i.e. 2.4 nm [6]. More recently, using pulsed laser deposition with a reflection high energy electron diffraction monitoring system, we fabricated high-quality fully-strained SRO/BTO/SRO capacitors...

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“…In particular, the choice of electrode materials should provide sufficiently large total interfacial capacitance compressive in-plane strains reducing the detrimental influence of the depolarizing field on /P 3 S 20 . At the same time, the numerical estimates based on the typical values of polarization of ultrathin BTO films (P 3 B0.3 C cm À 2 ) 16 and the difference between reciprocal space-charge capacitances of electrodes made of elemental metals and conductive oxides 20,49 show that the depolarizing-field effect is expected to give a considerable contribution to the TER of FTJs involving the BTO barrier (D fB0.3 À 0.5 eV). Accordingly, the microscopic interfacial effect on TER in our FTJs appears to be strong enough to override the depolarizingfield one and the coexistence of these two effects should be taken into account in the design of FTJs.…”

mentioning

confidence: 99%

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

et al. 2014

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Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO 3 barrier, La 0.7 Sr 0.3 MnO 3 bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.

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Electric-field penetration into metals: consequences for high-dielectric-constant capacitors

Cited by 158 publications

References 17 publications

Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films

Thickness dependence of intrinsic dielectric response and apparent interfacial capacitance in ferroelectric thin films

Polarization Relaxation Induced by a Depolarization Field in Ultrathin FerroelectricBaTiO3Capacitors

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

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